Update nitrokey crate to 0.2.3

This change updates the nitrokey crate to version 0.2.3. This version bumps the rand crate used to 0.6.1, which in turn requires an additional set of dependencies. Import subrepo nitrokey/:nitrokey at b3e2adc5bb1300441ca74cc7672617c042f3ea31 Import subrepo rand/:rand at 73613ff903512e9503e41cc8ba9eae76269dc598 Import subrepo rustc_version/:rustc_version at 0294f2ba2018bf7be672abd53db351ce5055fa02 Import subrepo semver-parser/:semver-parser at 750da9b11a04125231b1fb293866ca036845acee Import subrepo semver/:semver at 5eb6db94fa03f4d5c64a625a56188f496be47598
author: Daniel Mueller <deso@posteo.net> 2019-01-02 21:14:10 -0800
committer: Daniel Mueller <deso@posteo.net> 2019-01-02 21:14:10 -0800
commit: ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb (patch)
tree: 03134a683791176b49ef5c92e8d6acd24c3b5a9b
parent: 686f61b75055ecb02baf9d9449525ae447a3bed1 (diff)
download: nitrocli-ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb.tar.gz
nitrocli-ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb.tar.bz2
182 files changed, 22875 insertions, 5332 deletions
diff --git a/nitrocli/CHANGELOG.md b/nitrocli/CHANGELOG.md
index da08209..c6ad543 100644
--- a/nitrocli/CHANGELOG.md
+++ b/nitrocli/CHANGELOG.md
@@ -3,6 +3,10 @@ Unreleased
 - Added the `pws` command for accessing the password safe
 - Added the `lock` command for locking the Nitrokey device
 - Adjusted release build compile options to optimize binary for size
+- Bumped `nitrokey` dependency to `0.2.3`
+  - Bumped `rand` dependency to `0.6.1`
+  - Added `rustc_version` version `0.2.3`, `semver` version `0.9.0`, and
+    `semver-parser` version `0.7.0` as indirect dependencies
 - Bumped `cc` dependency to `1.0.28`
 
 
diff --git a/nitrocli/Cargo.lock b/nitrocli/Cargo.lock
index 09775f8..abbf84d 100644
--- a/nitrocli/Cargo.lock
+++ b/nitrocli/Cargo.lock
@@ -18,6 +18,14 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 replace = "cc 1.0.28"
 
 [[package]]
+name = "cloudabi"
+version = "0.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "fuchsia-zircon"
 version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -46,16 +54,16 @@ name = "nitrocli"
 version = "0.2.0"
 dependencies = [
  "argparse 0.2.2",
- "nitrokey 0.2.1",
+ "nitrokey 0.2.3",
 ]
 
 [[package]]
 name = "nitrokey"
-version = "0.2.1"
+version = "0.2.3"
 dependencies = [
  "libc 0.2.45 (registry+https://github.com/rust-lang/crates.io-index)",
  "nitrokey-sys 3.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -73,18 +81,103 @@ replace = "nitrokey-sys 3.4.1"
 
 [[package]]
 name = "rand"
-version = "0.4.3"
+version = "0.6.1"
 dependencies = [
+ "cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.45 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_chacha 0.1.0",
+ "rand_core 0.3.0",
+ "rand_hc 0.1.0",
+ "rand_isaac 0.1.0",
+ "rand_pcg 0.1.1",
+ "rand_xorshift 0.1.0",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "rand"
-version = "0.4.3"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+replace = "rand 0.6.1"
+
+[[package]]
+name = "rand_chacha"
+version = "0.1.0"
+dependencies = [
+ "rand_core 0.3.0",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.3.0"
+
+[[package]]
+name = "rand_hc"
+version = "0.1.0"
+dependencies = [
+ "rand_core 0.3.0",
+]
+
+[[package]]
+name = "rand_isaac"
+version = "0.1.0"
+dependencies = [
+ "rand_core 0.3.0",
+]
+
+[[package]]
+name = "rand_pcg"
+version = "0.1.1"
+dependencies = [
+ "rand_core 0.3.0",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.1.0"
+dependencies = [
+ "rand_core 0.3.0",
+]
+
+[[package]]
+name = "rustc_version"
+version = "0.2.3"
+dependencies = [
+ "semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rustc_version"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+replace = "rustc_version 0.2.3"
+
+[[package]]
+name = "semver"
+version = "0.9.0"
+dependencies = [
+ "semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "semver"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+replace = "semver 0.9.0"
+
+[[package]]
+name = "semver-parser"
+version = "0.7.0"
+
+[[package]]
+name = "semver-parser"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-replace = "rand 0.4.3"
+replace = "semver-parser 0.7.0"
 
 [[package]]
 name = "winapi"
@@ -108,11 +201,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 [metadata]
 "checksum bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "228047a76f468627ca71776ecdebd732a3423081fcf5125585bcd7c49886ce12"
 "checksum cc 1.0.28 (registry+https://github.com/rust-lang/crates.io-index)" = "bb4a8b715cb4597106ea87c7c84b2f1d452c7492033765df7f32651e66fcf749"
+"checksum cloudabi 0.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ddfc5b9aa5d4507acaf872de71051dfd0e309860e88966e1051e462a077aac4f"
 "checksum fuchsia-zircon 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2e9763c69ebaae630ba35f74888db465e49e259ba1bc0eda7d06f4a067615d82"
 "checksum fuchsia-zircon-sys 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
 "checksum libc 0.2.45 (registry+https://github.com/rust-lang/crates.io-index)" = "2d2857ec59fadc0773853c664d2d18e7198e83883e7060b63c924cb077bd5c74"
 "checksum nitrokey-sys 3.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "34794d630d40a093a3f0e31b821b38ee1c16e6909dc42064feff28f4798484f4"
-"checksum rand 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8356f47b32624fef5b3301c1be97e5944ecdd595409cc5da11d05f211db6cfbd"
+"checksum rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ae9d223d52ae411a33cf7e54ec6034ec165df296ccd23533d671a28252b6f66a"
+"checksum rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
+"checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
+"checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "92c1eb33641e276cfa214a0522acad57be5c56b10cb348b3c5117db75f3ac4b0"
 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/nitrocli/Cargo.toml b/nitrocli/Cargo.toml
index fc97e20..1fd4f3d 100644
--- a/nitrocli/Cargo.toml
+++ b/nitrocli/Cargo.toml
@@ -54,4 +54,7 @@ path = "../nitrokey"
 "cc:1.0.28" = { path = "../cc" }
 "libc:0.2.45" = { path = "../libc" }
 "nitrokey-sys:3.4.1" = { path = "../nitrokey-sys" }
-"rand:0.4.3" = { path = "../rand" }
+"rand:0.6.1" = { path = "../rand" }
+"rustc_version:0.2.3" = { path = "../rustc_version" }
+"semver:0.9.0" = { path = "../semver" }
+"semver-parser:0.7.0" = { path = "../semver-parser" }
diff --git a/nitrokey/CHANGELOG.md b/nitrokey/CHANGELOG.md
index a60d6a7..5064d4f 100644
--- a/nitrokey/CHANGELOG.md
+++ b/nitrokey/CHANGELOG.md
@@ -1,3 +1,16 @@
+# v0.2.3 (2018-12-31)
+
+- Dummy release to fix an issue with the crates.io tarball.
+
+# v0.2.2 (2018-12-30)
+
+- Update to Rust edition 2018.
+- Remove the `test-no-device` feature.
+- Update the rand dependency to version 0.6.
+- Add function `Device::get_model` that returns the connected model.
+- Derive the `Copy` and `Clone` traits for the enums `CommandError`, `LogLevel`
+  and `OtpMode`
+
 # v0.2.1 (2018-12-10)
 
 - Re-export `device::{StorageStatus, VolumeStatus}` in `lib.rs`.
diff --git a/nitrokey/Cargo.toml b/nitrokey/Cargo.toml
index dad751b..6369fba 100644
--- a/nitrokey/Cargo.toml
+++ b/nitrokey/Cargo.toml
@@ -1,7 +1,8 @@
 [package]
 name = "nitrokey"
-version = "0.2.1"
+version = "0.2.3"
 authors = ["Robin Krahl <robin.krahl@ireas.org>"]
+edition = "2018"
 homepage = "https://code.ireas.org/nitrokey-rs/"
 repository = "https://git.ireas.org/nitrokey-rs/"
 documentation = "https://docs.rs/nitrokey"
@@ -12,11 +13,10 @@ readme = "README.md"
 license = "MIT"
 
 [features]
-test-no-device = []
 test-pro = []
 test-storage = []
 
 [dependencies]
 libc = "0.2"
 nitrokey-sys = "3.4.1"
-rand = "0.4"
+rand = "0.6"
diff --git a/nitrokey/README.md b/nitrokey/README.md
index 6039943..568b1d4 100644
--- a/nitrokey/README.md
+++ b/nitrokey/README.md
@@ -4,11 +4,6 @@ A libnitrokey wrapper for Rust providing access to Nitrokey devices.
 
 [Documentation][]
 
-```toml
-[dependencies]
-nitrokey = "0.2.1"
-```
-
 ## Compatibility
 
 The required [`libnitrokey`][] version is built from source.  The host system
@@ -35,12 +30,12 @@ supported by `nitrokey-rs`:
 ## Tests
 
 This crate has three test suites that can be selected using features.  One test
-suite (feature `test-no-device`) assumes that no Nitrokey device is connected.
-The two other test suites require a Nitrokey Pro (feature `test-pro`) or a
-Nitrokey Storage (feature `test-storage`) to be connected.
+suite assumes that no Nitrokey device is connected. It is run if no other test
+suite is selected.  The two other test suites require a Nitrokey Pro (feature
+`test-pro`) or a Nitrokey Storage (feature `test-storage`) to be connected.
 
 Use the `--features` option for Cargo to select one of the test suites.  You
-cannot select more than one of the test suites at the same time.  Note that the
+should select more than one of the test suites at the same time.  Note that the
 test suites that require a Nitrokey device assume that the device’s passwords
 are the factory defaults (admin password `12345678` and user password
 `123456`).  Running the test suite with a device with different passwords might
@@ -54,7 +49,7 @@ the test executable.
 In conclusion, you can use these commands to run the test suites:
 
 ```
-$ cargo test --features test-no-device -- --test-threads 1
+$ cargo test
 $ cargo test --features test-pro -- --test-threads 1
 $ cargo test --features test-storage -- --test-threads 1
 ```
diff --git a/nitrokey/src/auth.rs b/nitrokey/src/auth.rs
index 0918222..017cdbb 100644
--- a/nitrokey/src/auth.rs
+++ b/nitrokey/src/auth.rs
@@ -1,10 +1,14 @@
-use config::{Config, RawConfig};
-use device::{Device, DeviceWrapper, Pro, Storage};
-use nitrokey_sys;
-use otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData, RawOtpSlotData};
 use std::ops::Deref;
 use std::os::raw::c_int;
-use util::{generate_password, get_command_result, get_cstring, result_from_string, CommandError};
+
+use nitrokey_sys;
+
+use crate::config::{Config, RawConfig};
+use crate::device::{Device, DeviceWrapper, Pro, Storage};
+use crate::otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData, RawOtpSlotData};
+use crate::util::{
+    generate_password, get_command_result, get_cstring, result_from_string, CommandError,
+};
 
 static TEMPORARY_PASSWORD_LENGTH: usize = 25;
 
diff --git a/nitrokey/src/config.rs b/nitrokey/src/config.rs
index 33bf256..2ce6f77 100644
--- a/nitrokey/src/config.rs
+++ b/nitrokey/src/config.rs
@@ -1,4 +1,4 @@
-use util::CommandError;
+use crate::util::CommandError;
 
 /// The configuration for a Nitrokey.
 #[derive(Clone, Copy, Debug, PartialEq)]
diff --git a/nitrokey/src/device.rs b/nitrokey/src/device.rs
index f135261..9c6608d 100644
--- a/nitrokey/src/device.rs
+++ b/nitrokey/src/device.rs
@@ -1,20 +1,38 @@
-use auth::Authenticate;
-use config::{Config, RawConfig};
+use std::fmt;
+
 use libc;
 use nitrokey_sys;
-use otp::GenerateOtp;
-use pws::GetPasswordSafe;
-use util::{get_command_result, get_cstring, get_last_error, result_from_string, CommandError};
+
+use crate::auth::Authenticate;
+use crate::config::{Config, RawConfig};
+use crate::otp::GenerateOtp;
+use crate::pws::GetPasswordSafe;
+use crate::util::{
+    get_command_result, get_cstring, get_last_error, result_from_string, CommandError,
+};
 
 /// Available Nitrokey models.
-#[derive(Debug, PartialEq)]
-enum Model {
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Model {
     /// The Nitrokey Storage.
     Storage,
     /// The Nitrokey Pro.
     Pro,
 }
 
+impl fmt::Display for Model {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}",
+            match *self {
+                Model::Pro => "Pro",
+                Model::Storage => "Storage",
+            }
+        )
+    }
+}
+
 /// A wrapper for a Nitrokey device of unknown type.
 ///
 /// Use the function [`connect`][] to obtain a wrapped instance.  The wrapper implements all traits
@@ -210,6 +228,21 @@ pub struct StorageStatus {
 /// This trait provides the commands that can be executed without authentication and that are
 /// present on all supported Nitrokey devices.
 pub trait Device: Authenticate + GetPasswordSafe + GenerateOtp {
+    /// Returns the model of the connected Nitrokey device.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use nitrokey::Device;
+    /// # use nitrokey::CommandError;
+    ///
+    /// # fn try_main() -> Result<(), CommandError> {
+    /// let device = nitrokey::connect()?;
+    /// println!("Connected to a Nitrokey {}", device.get_model());
+    /// #    Ok(())
+    /// # }
+    fn get_model(&self) -> Model;
+
     /// Returns the serial number of the Nitrokey device.  The serial number is the string
     /// representation of a hex number.
     ///
@@ -536,7 +569,7 @@ fn connect_model(model: Model) -> bool {
 }
 
 impl DeviceWrapper {
-    fn device(&self) -> &Device {
+    fn device(&self) -> &dyn Device {
         match *self {
             DeviceWrapper::Storage(ref storage) => storage,
             DeviceWrapper::Pro(ref pro) => pro,
@@ -562,9 +595,30 @@ impl GenerateOtp for DeviceWrapper {
     }
 }
 
-impl Device for DeviceWrapper {}
+impl Device for DeviceWrapper {
+    fn get_model(&self) -> Model {
+        match *self {
+            DeviceWrapper::Pro(_) => Model::Pro,
+            DeviceWrapper::Storage(_) => Model::Storage,
+        }
+    }
+}
 
 impl Pro {
+    /// Connects to a Nitrokey Pro.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use nitrokey::Pro;
+    ///
+    /// fn use_pro(device: Pro) {}
+    ///
+    /// match nitrokey::Pro::connect() {
+    ///     Ok(device) => use_pro(device),
+    ///     Err(err) => println!("Could not connect to the Nitrokey Pro: {}", err),
+    /// }
+    /// ```
     pub fn connect() -> Result<Pro, CommandError> {
         // TODO: maybe Option instead of Result?
         match connect_model(Model::Pro) {
@@ -582,11 +636,29 @@ impl Drop for Pro {
     }
 }
 
-impl Device for Pro {}
+impl Device for Pro {
+    fn get_model(&self) -> Model {
+        Model::Pro
+    }
+}
 
 impl GenerateOtp for Pro {}
 
 impl Storage {
+    /// Connects to a Nitrokey Storage.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use nitrokey::Storage;
+    ///
+    /// fn use_storage(device: Storage) {}
+    ///
+    /// match nitrokey::Storage::connect() {
+    ///     Ok(device) => use_storage(device),
+    ///     Err(err) => println!("Could not connect to the Nitrokey Storage: {}", err),
+    /// }
+    /// ```
     pub fn connect() -> Result<Storage, CommandError> {
         // TODO: maybe Option instead of Result?
         match connect_model(Model::Storage) {
@@ -661,7 +733,6 @@ impl Storage {
         unsafe { get_command_result(nitrokey_sys::NK_lock_encrypted_volume()) }
     }
 
-
     /// Returns the status of the connected storage device.
     ///
     /// # Example
@@ -715,7 +786,11 @@ impl Drop for Storage {
     }
 }
 
-impl Device for Storage {}
+impl Device for Storage {
+    fn get_model(&self) -> Model {
+        Model::Storage
+    }
+}
 
 impl GenerateOtp for Storage {}
 
diff --git a/nitrokey/src/lib.rs b/nitrokey/src/lib.rs
index e70aa73..9f21518 100644
--- a/nitrokey/src/lib.rs
+++ b/nitrokey/src/lib.rs
@@ -84,25 +84,25 @@
 //! [`DeviceWrapper`]: enum.DeviceWrapper.html
 //! [`User`]: struct.User.html
 
-extern crate libc;
-extern crate nitrokey_sys;
-extern crate rand;
+#![warn(missing_docs, rust_2018_compatibility, rust_2018_idioms, unused)]
 
 mod auth;
 mod config;
 mod device;
 mod otp;
 mod pws;
-#[cfg(test)]
-mod tests;
 mod util;
 
-pub use auth::{Admin, Authenticate, User};
-pub use config::Config;
-pub use device::{connect, Device, DeviceWrapper, Pro, Storage, StorageStatus, VolumeStatus};
-pub use otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData};
-pub use pws::{GetPasswordSafe, PasswordSafe, SLOT_COUNT};
-pub use util::{CommandError, LogLevel};
+use nitrokey_sys;
+
+pub use crate::auth::{Admin, Authenticate, User};
+pub use crate::config::Config;
+pub use crate::device::{
+    connect, Device, DeviceWrapper, Model, Pro, Storage, StorageStatus, VolumeStatus,
+};
+pub use crate::otp::{ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData};
+pub use crate::pws::{GetPasswordSafe, PasswordSafe, SLOT_COUNT};
+pub use crate::util::{CommandError, LogLevel};
 
 /// Enables or disables debug output.  Calling this method with `true` is equivalent to setting the
 /// log level to `Debug`; calling it with `false` is equivalent to the log level `Error` (see
diff --git a/nitrokey/src/otp.rs b/nitrokey/src/otp.rs
index 00a5e5e..6f6bd80 100644
--- a/nitrokey/src/otp.rs
+++ b/nitrokey/src/otp.rs
@@ -1,9 +1,11 @@
-use nitrokey_sys;
 use std::ffi::CString;
-use util::{get_command_result, get_cstring, result_from_string, CommandError};
+
+use nitrokey_sys;
+
+use crate::util::{get_command_result, get_cstring, result_from_string, CommandError};
 
 /// Modes for one-time password generation.
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum OtpMode {
     /// Generate one-time passwords with six digits.
     SixDigits,
diff --git a/nitrokey/src/pws.rs b/nitrokey/src/pws.rs
index c20fe9d..08ac365 100644
--- a/nitrokey/src/pws.rs
+++ b/nitrokey/src/pws.rs
@@ -1,7 +1,10 @@
-use device::{Device, DeviceWrapper, Pro, Storage};
 use libc;
 use nitrokey_sys;
-use util::{get_command_result, get_cstring, get_last_error, result_from_string, CommandError};
+
+use crate::device::{Device, DeviceWrapper, Pro, Storage};
+use crate::util::{
+    get_command_result, get_cstring, get_last_error, result_from_string, CommandError,
+};
 
 /// The number of slots in a [`PasswordSafe`][].
 ///
@@ -51,7 +54,7 @@ pub const SLOT_COUNT: u8 = 16;
 /// [`lock`]: trait.Device.html#method.lock
 /// [`GetPasswordSafe`]: trait.GetPasswordSafe.html
 pub struct PasswordSafe<'a> {
-    _device: &'a Device,
+    _device: &'a dyn Device,
 }
 
 /// Provides access to a [`PasswordSafe`][].
@@ -98,11 +101,11 @@ pub trait GetPasswordSafe {
     /// [`lock`]: trait.Device.html#method.lock
     /// [`InvalidString`]: enum.CommandError.html#variant.InvalidString
     /// [`WrongPassword`]: enum.CommandError.html#variant.WrongPassword
-    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe, CommandError>;
+    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe<'_>, CommandError>;
 }
 
 fn get_password_safe<'a>(
-    device: &'a Device,
+    device: &'a dyn Device,
     user_pin: &str,
 ) -> Result<PasswordSafe<'a>, CommandError> {
     let user_pin_string = get_cstring(user_pin)?;
@@ -333,19 +336,19 @@ impl<'a> Drop for PasswordSafe<'a> {
 }
 
 impl GetPasswordSafe for Pro {
-    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe, CommandError> {
+    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe<'_>, CommandError> {
         get_password_safe(self, user_pin)
     }
 }
 
 impl GetPasswordSafe for Storage {
-    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe, CommandError> {
+    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe<'_>, CommandError> {
         get_password_safe(self, user_pin)
     }
 }
 
 impl GetPasswordSafe for DeviceWrapper {
-    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe, CommandError> {
+    fn get_password_safe(&self, user_pin: &str) -> Result<PasswordSafe<'_>, CommandError> {
         get_password_safe(self, user_pin)
     }
 }
diff --git a/nitrokey/src/tests/mod.rs b/nitrokey/src/tests/mod.rs
deleted file mode 100644
index 34ca0aa..0000000
--- a/nitrokey/src/tests/mod.rs
+++ /dev/null
@@ -1,4 +0,0 @@
-mod device;
-mod otp;
-mod pws;
-mod util;
diff --git a/nitrokey/src/tests/util.rs b/nitrokey/src/tests/util.rs
deleted file mode 100644
index c6fbb8f..0000000
--- a/nitrokey/src/tests/util.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-pub static ADMIN_PASSWORD: &str = "12345678";
-pub static USER_PASSWORD: &str = "123456";
-
-#[cfg(feature = "test-no-device")]
-pub type Target = ::Pro;
-
-#[cfg(feature = "test-pro")]
-pub type Target = ::Pro;
-
-#[cfg(feature = "test-storage")]
-pub type Target = ::Storage;
diff --git a/nitrokey/src/util.rs b/nitrokey/src/util.rs
index 6f4fbb0..a2e957e 100644
--- a/nitrokey/src/util.rs
+++ b/nitrokey/src/util.rs
@@ -1,13 +1,12 @@
-use libc::{c_void, free};
-use nitrokey_sys;
-use rand::{OsRng, Rng};
-use std;
 use std::ffi::{CStr, CString};
 use std::fmt;
 use std::os::raw::{c_char, c_int};
 
+use libc::{c_void, free};
+use rand::Rng;
+
 /// Error types returned by Nitrokey device or by the library.
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum CommandError {
     /// A packet with a wrong checksum has been sent or received.
     WrongCrc,
@@ -44,7 +43,7 @@ pub enum CommandError {
 ///
 /// Setting the log level to a lower level enables all output from higher levels too.  Currently,
 /// only the log levels `Warning`, `DebugL1`, `Debug` and `DebugL2` are actually used.
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum LogLevel {
     /// Error messages.  Currently not used.
     Error,
@@ -101,12 +100,8 @@ pub fn get_last_error() -> CommandError {
 }
 
 pub fn generate_password(length: usize) -> std::io::Result<Vec<u8>> {
-    let mut rng = match OsRng::new() {
-        Ok(rng) => rng,
-        Err(err) => return Err(err),
-    };
     let mut data = vec![0u8; length];
-    rng.fill_bytes(&mut data[..]);
+    rand::thread_rng().fill(&mut data[..]);
     return Ok(data);
 }
 
@@ -115,7 +110,7 @@ pub fn get_cstring<T: Into<Vec<u8>>>(s: T) -> Result<CString, CommandError> {
 }
 
 impl fmt::Display for CommandError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let msg = match *self {
             CommandError::WrongCrc => "A packet with a wrong checksum has been sent or received",
             CommandError::WrongSlot => "The given OTP slot does not exist",
diff --git a/nitrokey/src/tests/device.rs b/nitrokey/tests/device.rs
index fed465d..26afa62 100644
--- a/nitrokey/src/tests/device.rs
+++ b/nitrokey/tests/device.rs
@@ -1,8 +1,12 @@
+mod util;
+
 use std::ffi::CStr;
 use std::process::Command;
 use std::{thread, time};
-use tests::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
-use {Authenticate, CommandError, Config, Device, Storage};
+
+use nitrokey::{Authenticate, CommandError, Config, Device, Storage};
+
+use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
 
 static ADMIN_NEW_PASSWORD: &str = "1234567890";
 static USER_NEW_PASSWORD: &str = "abcdefghij";
@@ -15,45 +19,45 @@ fn count_nitrokey_block_devices() -> usize {
         .expect("Could not list block devices");
     String::from_utf8_lossy(&output.stdout)
         .split("\n")
-        .filter(|&s| s == "Nitrokey Storage")
+        .filter(|&s| s.replace("_", " ") == "Nitrokey Storage")
         .count()
 }
 
 #[test]
-#[cfg_attr(not(feature = "test-no-device"), ignore)]
+#[cfg_attr(any(feature = "test-pro", feature = "test-storage"), ignore)]
 fn connect_no_device() {
-    assert!(::connect().is_err());
-    assert!(::Pro::connect().is_err());
-    assert!(::Storage::connect().is_err());
+    assert!(nitrokey::connect().is_err());
+    assert!(nitrokey::Pro::connect().is_err());
+    assert!(nitrokey::Storage::connect().is_err());
 }
 
 #[test]
 #[cfg_attr(not(feature = "test-pro"), ignore)]
 fn connect_pro() {
-    assert!(::connect().is_ok());
-    assert!(::Pro::connect().is_ok());
-    assert!(::Storage::connect().is_err());
-    match ::connect().unwrap() {
-        ::DeviceWrapper::Pro(_) => assert!(true),
-        ::DeviceWrapper::Storage(_) => assert!(false),
+    assert!(nitrokey::connect().is_ok());
+    assert!(nitrokey::Pro::connect().is_ok());
+    assert!(nitrokey::Storage::connect().is_err());
+    match nitrokey::connect().unwrap() {
+        nitrokey::DeviceWrapper::Pro(_) => assert!(true),
+        nitrokey::DeviceWrapper::Storage(_) => assert!(false),
     };
 }
 
 #[test]
 #[cfg_attr(not(feature = "test-storage"), ignore)]
 fn connect_storage() {
-    assert!(::connect().is_ok());
-    assert!(::Pro::connect().is_err());
-    assert!(::Storage::connect().is_ok());
-    match ::connect().unwrap() {
-        ::DeviceWrapper::Pro(_) => assert!(false),
-        ::DeviceWrapper::Storage(_) => assert!(true),
+    assert!(nitrokey::connect().is_ok());
+    assert!(nitrokey::Pro::connect().is_err());
+    assert!(nitrokey::Storage::connect().is_ok());
+    match nitrokey::connect().unwrap() {
+        nitrokey::DeviceWrapper::Pro(_) => assert!(false),
+        nitrokey::DeviceWrapper::Storage(_) => assert!(true),
     };
 }
 
 fn assert_empty_serial_number() {
     unsafe {
-        let ptr = ::nitrokey_sys::NK_device_serial_number();
+        let ptr = nitrokey_sys::NK_device_serial_number();
         assert!(!ptr.is_null());
         let cstr = CStr::from_ptr(ptr);
         assert_eq!(cstr.to_string_lossy(), "");
@@ -77,6 +81,23 @@ fn disconnect() {
     assert_empty_serial_number();
 }
 
+fn require_model(model: nitrokey::Model) {
+    assert_eq!(model, nitrokey::connect().unwrap().get_model());
+    assert_eq!(model, Target::connect().unwrap().get_model());
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-pro"), ignore)]
+fn get_model_pro() {
+    require_model(nitrokey::Model::Pro);
+}
+
+#[test]
+#[cfg_attr(not(feature = "test-storage"), ignore)]
+fn get_model_storage() {
+    require_model(nitrokey::Model::Storage);
+}
+
 #[test]
 #[cfg_attr(not(any(feature = "test-pro", feature = "test-storage")), ignore)]
 fn get_serial_number() {
@@ -163,11 +184,9 @@ fn change_user_pin() {
     let device = device.authenticate_user(USER_PASSWORD).unwrap().device();
     let device = device.authenticate_user(USER_NEW_PASSWORD).unwrap_err().0;
 
-    assert!(
-        device
-            .change_user_pin(USER_PASSWORD, USER_NEW_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .change_user_pin(USER_PASSWORD, USER_NEW_PASSWORD)
+        .is_ok());
 
     let device = device.authenticate_user(USER_PASSWORD).unwrap_err().0;
     let device = device
@@ -178,11 +197,9 @@ fn change_user_pin() {
     let result = device.change_user_pin(USER_PASSWORD, USER_PASSWORD);
     assert_eq!(Err(CommandError::WrongPassword), result);
 
-    assert!(
-        device
-            .change_user_pin(USER_NEW_PASSWORD, USER_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .change_user_pin(USER_NEW_PASSWORD, USER_PASSWORD)
+        .is_ok());
 
     let device = device.authenticate_user(USER_PASSWORD).unwrap().device();
     assert!(device.authenticate_user(USER_NEW_PASSWORD).is_err());
@@ -195,11 +212,9 @@ fn change_admin_pin() {
     let device = device.authenticate_admin(ADMIN_PASSWORD).unwrap().device();
     let device = device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err().0;
 
-    assert!(
-        device
-            .change_admin_pin(ADMIN_PASSWORD, ADMIN_NEW_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .change_admin_pin(ADMIN_PASSWORD, ADMIN_NEW_PASSWORD)
+        .is_ok());
 
     let device = device.authenticate_admin(ADMIN_PASSWORD).unwrap_err().0;
     let device = device
@@ -212,11 +227,9 @@ fn change_admin_pin() {
         device.change_admin_pin(ADMIN_PASSWORD, ADMIN_PASSWORD)
     );
 
-    assert!(
-        device
-            .change_admin_pin(ADMIN_NEW_PASSWORD, ADMIN_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .change_admin_pin(ADMIN_NEW_PASSWORD, ADMIN_PASSWORD)
+        .is_ok());
 
     let device = device.authenticate_admin(ADMIN_PASSWORD).unwrap().device();
     device.authenticate_admin(ADMIN_NEW_PASSWORD).unwrap_err();
@@ -235,11 +248,9 @@ fn require_failed_user_login(device: Target, password: &str, error: CommandError
 fn unlock_user_pin() {
     let device = Target::connect().unwrap();
     let device = device.authenticate_user(USER_PASSWORD).unwrap().device();
-    assert!(
-        device
-            .unlock_user_pin(ADMIN_PASSWORD, USER_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .unlock_user_pin(ADMIN_PASSWORD, USER_PASSWORD)
+        .is_ok());
     assert_eq!(
         Err(CommandError::WrongPassword),
         device.unlock_user_pin(USER_PASSWORD, USER_PASSWORD)
@@ -255,11 +266,9 @@ fn unlock_user_pin() {
         Err(CommandError::WrongPassword),
         device.unlock_user_pin(USER_PASSWORD, USER_PASSWORD)
     );
-    assert!(
-        device
-            .unlock_user_pin(ADMIN_PASSWORD, USER_PASSWORD)
-            .is_ok()
-    );
+    assert!(device
+        .unlock_user_pin(ADMIN_PASSWORD, USER_PASSWORD)
+        .is_ok());
     device.authenticate_user(USER_PASSWORD).unwrap();
 }
 
diff --git a/nitrokey/src/tests/otp.rs b/nitrokey/tests/otp.rs
index cf71d9d..8e7ae08 100644
--- a/nitrokey/src/tests/otp.rs
+++ b/nitrokey/tests/otp.rs
@@ -1,6 +1,12 @@
+mod util;
+
 use std::ops::Deref;
-use tests::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
-use {Admin, Authenticate, CommandError, Config, ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData};
+
+use nitrokey::{
+    Admin, Authenticate, CommandError, Config, ConfigureOtp, GenerateOtp, OtpMode, OtpSlotData,
+};
+
+use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
 
 // test suite according to RFC 4226, Appendix D
 static HOTP_SECRET: &str = "3132333435363738393031323334353637383930";
diff --git a/nitrokey/src/tests/pws.rs b/nitrokey/tests/pws.rs
index f581515..875324b 100644
--- a/nitrokey/src/tests/pws.rs
+++ b/nitrokey/tests/pws.rs
@@ -1,8 +1,31 @@
-use device::Device;
+mod util;
+
+use std::ffi::CStr;
+
+use libc::{c_int, c_void, free};
+use nitrokey::{CommandError, Device, GetPasswordSafe, PasswordSafe, SLOT_COUNT};
 use nitrokey_sys;
-use pws::{GetPasswordSafe, PasswordSafe, SLOT_COUNT};
-use tests::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
-use util::{result_from_string, CommandError};
+
+use crate::util::{Target, ADMIN_PASSWORD, USER_PASSWORD};
+
+fn get_slot_name_direct(slot: u8) -> Result<String, CommandError> {
+    let ptr = unsafe { nitrokey_sys::NK_get_password_safe_slot_name(slot) };
+    if ptr.is_null() {
+        return Err(CommandError::Unknown);
+    }
+    let s = unsafe { CStr::from_ptr(ptr).to_string_lossy().into_owned() };
+    unsafe { free(ptr as *mut c_void) };
+    match s.is_empty() {
+        true => {
+            let error = unsafe { nitrokey_sys::NK_get_last_command_status() } as c_int;
+            match error {
+                0 => Err(CommandError::Unknown),
+                other => Err(CommandError::from(other)),
+            }
+        }
+        false => Ok(s),
+    }
+}
 
 fn get_pws(device: &Target) -> PasswordSafe {
     device.get_password_safe(USER_PASSWORD).unwrap()
@@ -12,11 +35,9 @@ fn get_pws(device: &Target) -> PasswordSafe {
 #[cfg_attr(not(any(feature = "test-pro", feature = "test-storage")), ignore)]
 fn enable() {
     let device = Target::connect().unwrap();
-    assert!(
-        device
-            .get_password_safe(&(USER_PASSWORD.to_owned() + "123"))
-            .is_err()
-    );
+    assert!(device
+        .get_password_safe(&(USER_PASSWORD.to_owned() + "123"))
+        .is_err());
     assert!(device.get_password_safe(USER_PASSWORD).is_ok());
     assert!(device.get_password_safe(ADMIN_PASSWORD).is_err());
     assert!(device.get_password_safe(USER_PASSWORD).is_ok());
@@ -30,13 +51,13 @@ fn drop() {
         let pws = get_pws(&device);
         assert!(pws.write_slot(1, "name", "login", "password").is_ok());
         assert_eq!("name", pws.get_slot_name(1).unwrap());
-        let result = result_from_string(unsafe { nitrokey_sys::NK_get_password_safe_slot_name(1) });
+        let result = get_slot_name_direct(1);
         assert_eq!(Ok(String::from("name")), result);
     }
-    let result = result_from_string(unsafe { nitrokey_sys::NK_get_password_safe_slot_name(1) });
+    let result = get_slot_name_direct(1);
     assert_eq!(Ok(String::from("name")), result);
     assert!(device.lock().is_ok());
-    let result = result_from_string(unsafe { nitrokey_sys::NK_get_password_safe_slot_name(1) });
+    let result = get_slot_name_direct(1);
     assert_eq!(Err(CommandError::NotAuthorized), result);
 }
 
diff --git a/nitrokey/tests/util/mod.rs b/nitrokey/tests/util/mod.rs
new file mode 100644
index 0000000..c2c94e2
--- /dev/null
+++ b/nitrokey/tests/util/mod.rs
@@ -0,0 +1,8 @@
+pub static ADMIN_PASSWORD: &str = "12345678";
+pub static USER_PASSWORD: &str = "123456";
+
+#[cfg(not(feature = "test-storage"))]
+pub type Target = nitrokey::Pro;
+
+#[cfg(feature = "test-storage")]
+pub type Target = nitrokey::Storage;
diff --git a/rand/.travis.yml b/rand/.travis.yml
index f3d7688..2f0bb79 100644
--- a/rand/.travis.yml
+++ b/rand/.travis.yml
@@ -1,28 +1,212 @@
 language: rust
 sudo: false
 
+# We support too many combinations of Rust releases, crate features, operating
+# systems, and architectures to even remotely test all combinations.
+# Yet it turns out we can test most of these independent of each other, because
+# they serve different goals or test different pieces of code.
+#
+# RUST RELEASES
+# Goal: make sure we don't use language features unavailable on a certain
+#       version, and build without warnings.
+# We have different builders use 4 Rust releases, a pinned stable release,
+# the latest stable, beta and nightly.
+#
+# ARCHITECTURES
+# Goal: test against issues caused by differences in endianness, pointer sizes,
+#       etc.
+# We run tests on 4 different architectures.
+# - x64_84, default on Travis (Linux) and AppVeyor (Windows)
+# - i686, second AppVeyor (Windows) configuration
+# - MIPS, big-endian Linux emulated with QEMU (thanks to Trust)
+# - ARMv7, Android emulated with QEMU (thanks to Trust)
+#
+# OPERATING SYSTEMS
+# Goal: test on many operating systems, to verify the OsRng code, which is
+#       mostly architecture-independent.
+# We run tests on Linux, OS X, Windows, Android (emulated), and Node.js (using
+# cargo-web).
+# One builder cross-compiles for many of the remaining OSes, which ensures we
+# keep building, but doesn't run tests.
+# OSes supported by Rand but which we can't cross-compile because there
+# is no pre-built standard library available: Dragonfly BSD, Haiku, OpenBSD.
+#
+# CRATE FEATURES, TESTS, AND SUB-CRATES
+# Goal: Run unit tests, doctests, examples, and test benchmarks for all crates,
+#       in configurations that cover all interesting combinations of features.
+# (`--lib` only runs unit tests just like `--tests`, but the latter is not
+# available in Rust 1.22.0)
+# Tests run on rand:
+# - test no_std support, but only the unit tests:
+#   `cargo test --lib --no-default-features`
+# - run unit tests and doctests with all features which are available on stable:
+#   `cargo test --features=serde1,log`
+# - test examples:
+#   `cargo test --examples`
+# Additional tests on nightly:
+# - run unit tests and doctests with all features which are available on nightly:
+#   `cargo test --all-features`
+# - test no_std support, including the nightly alloc feature:
+#   cargo test --lib --no-default-features --features=alloc
+# - run benchmarks as tests:
+#   `cargo test --benches --features=nightly`
+# Tests on subcrates:
+# - select crates via --manifest-path (more reliable than --package)
+# - test appropriate feature matrix
+#
+# TODO: SIMD support on stable releases
+# NOTE: SIMD support is unreliable on nightly; we track the latest release
 matrix:
   include:
-    - rust: 1.15.0
-    - rust: stable
+    - rust: 1.22.0
+      env: DESCRIPTION="pinned stable Rust release"
+      script:
+        # Differs from standard script: rand_pcg features
+        - cargo test --lib --no-default-features
+        # TODO: add simd_support feature:
+        - cargo test --features=serde1,log
+        - cargo test --examples
+        - cargo test --manifest-path rand_core/Cargo.toml
+        - cargo test --manifest-path rand_core/Cargo.toml --no-default-features
+        - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1
+        # TODO: cannot test rand_pcg due to explicit dependency on i128
+        - cargo test --manifest-path rand_xorshift/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_chacha/Cargo.toml
+        - cargo test --manifest-path rand_hc/Cargo.toml
+
     - rust: stable
+      env: DESCRIPTION="stable Rust release, macOS, iOS (cross-compile only)"
       os: osx
+      install:
+        - rustup target add aarch64-apple-ios
+      script:
+        # Differs from standard script: includes aarch64-apple-ios cross-build
+        - cargo test --lib --no-default-features
+        # TODO: add simd_support feature:
+        - cargo test --features=serde1,log
+        - cargo test --examples
+        - cargo test --manifest-path rand_core/Cargo.toml
+        - cargo test --manifest-path rand_core/Cargo.toml --no-default-features
+        - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_pcg/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_xorshift/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_chacha/Cargo.toml
+        - cargo test --manifest-path rand_hc/Cargo.toml
+        - cargo build --target=aarch64-apple-ios
+
     - rust: beta
-    - rust: nightly
+      env: DESCRIPTION="beta Rust release"
 
     - rust: nightly
+      env: DESCRIPTION="nightly features, benchmarks, documentation"
+      install:
+        - cargo --list | egrep "^\s*deadlinks$" -q || cargo install cargo-deadlinks
+        - cargo deadlinks -V
       before_script:
         - pip install 'travis-cargo<0.2' --user && export PATH=$HOME/.local/bin:$PATH
       script:
-        - cargo doc --no-deps --all-features
-        - cargo test --benches
-        - cargo test --features nightly
+        # Differs from standard script: alloc feature, all features, doc build
+        - cargo test --lib --no-default-features --features=alloc
+        - cargo test --all-features
+        - cargo test --benches --features=nightly
+        - cargo test --examples
+        - cargo test --manifest-path rand_core/Cargo.toml
+        - cargo test --manifest-path rand_core/Cargo.toml --no-default-features --features=alloc
+        - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_pcg/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_xorshift/Cargo.toml --features=serde1
+        - cargo test --manifest-path rand_chacha/Cargo.toml
+        - cargo test --manifest-path rand_hc/Cargo.toml
+        # remove cached documentation, otherwise files from previous PRs can get included
+        - rm -rf target/doc
+        - cargo doc --no-deps --all --all-features
+        - cargo deadlinks --dir target/doc
       after_success:
         - travis-cargo --only nightly doc-upload
 
+    - rust: nightly
+      env: DESCRIPTION="WASM via emscripten, stdweb and wasm-bindgen"
+      install:
+        - rustup target add wasm32-unknown-unknown
+        - rustup target add wasm32-unknown-emscripten
+        # cargo-web takes ±10 min. to install, and cargo and cargo-update offer
+        # no reliable update-or-install command. We ignore updating for now
+        # (just drop the Travis' caches when necessary)
+        - cargo --list | egrep "^\s*web$" -q || cargo install cargo-web
+        - cargo web -V
+      addons:
+        chrome: stable
+      script:
+        # testing wasm32-unknown-emscripten fails because of rust-lang/rust#49877
+        - cargo build --target wasm32-unknown-emscripten
+        #- cargo web test --target wasm32-unknown-emscripten
+        #- cargo web test --nodejs --target wasm32-unknown-emscripten
+        - cargo build --target wasm32-unknown-unknown # without any features
+        - cargo web test --nodejs --target wasm32-unknown-unknown --features=stdweb
+        - cargo build --target wasm32-unknown-unknown --features=wasm-bindgen
+
+    - rust: nightly
+      env: DESCRIPTION="cross-platform builder (doesn't run tests)"
+      install:
+        - rustup target add x86_64-sun-solaris
+        - rustup target add x86_64-unknown-cloudabi
+        - rustup target add x86_64-unknown-freebsd
+        #- rustup target add x86_64-unknown-fuchsia
+        - rustup target add x86_64-unknown-netbsd
+        - rustup target add x86_64-unknown-redox
+      script:
+        - cargo build --target=x86_64-sun-solaris --all-features
+        - cargo build --target=x86_64-unknown-cloudabi --all-features
+        - cargo build --target=x86_64-unknown-freebsd --all-features
+        #- cargo build --target=x86_64-unknown-fuchsia --all-features
+        - cargo build --target=x86_64-unknown-netbsd --all-features
+        - cargo build --target=x86_64-unknown-redox --all-features
+
+    # Trust cross-built/emulated targets. We must repeat all non-default values.
+    - rust: stable
+      sudo: required
+      dist: trusty
+      services: docker
+      env: DESCRIPTION="Linux (MIPS, big-endian)" TARGET=mips-unknown-linux-gnu
+      install:
+        - sh utils/ci/install.sh
+        - source ~/.cargo/env || true
+      script:
+        - bash utils/ci/script.sh
+    - rust: stable
+      sudo: required
+      dist: trusty
+      services: docker
+      env: DESCRIPTION="Android (ARMv7)" TARGET=armv7-linux-androideabi
+      install:
+        - sh utils/ci/install.sh
+        - source ~/.cargo/env || true
+      script:
+        - bash utils/ci/script.sh
+
+before_install:
+  - set -e
+  - rustup self update
+
 script:
-  - cargo test
-  - cargo test --manifest-path rand-derive/Cargo.toml
+  - cargo test --lib --no-default-features
+  # TODO: add simd_support feature:
+  - cargo test --features=serde1,log
+  - cargo test --examples
+  - cargo test --manifest-path rand_core/Cargo.toml
+  - cargo test --manifest-path rand_core/Cargo.toml --no-default-features
+  - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_pcg/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_xorshift/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_chacha/Cargo.toml
+  - cargo test --manifest-path rand_hc/Cargo.toml
+
+after_script: set +e
+
+cache: cargo
+before_cache:
+  # Travis can't cache files that are not readable by "others"
+  - chmod -R a+r $HOME/.cargo
 
 env:
   global:
diff --git a/rand/CHANGELOG.md b/rand/CHANGELOG.md
index 1811b45..489df48 100644
--- a/rand/CHANGELOG.md
+++ b/rand/CHANGELOG.md
@@ -2,22 +2,224 @@
 All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
-and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+A [separate changelog is kept for rand_core](rand_core/CHANGELOG.md).
+
+You may also find the [Upgrade Guide](https://rust-random.github.io/book/update.html) useful.
+
+
+## [0.6.1] - 2018-11-22
+- Support sampling `Duration` also for `no_std` (only since Rust 1.25) (#649)
+- Disable default features of `libc` (#647)
+
+## [0.6.0] - 2018-11-14
+
+### Project organisation
+- Rand has moved from [rust-lang-nursery](https://github.com/rust-lang-nursery/rand)
+  to [rust-random](https://github.com/rust-random/rand)! (#578)
+- Created [The Rust Random Book](https://rust-random.github.io/book/)
+  ([source](https://github.com/rust-random/book))
+- Update copyright and licence notices (#591, #611)
+- Migrate policy documentation from the wiki (#544)
+
+### Platforms
+- Add fork protection on Unix (#466)
+- Added support for wasm-bindgen. (#541, #559, #562, #600)
+- Enable `OsRng` for powerpc64, sparc and sparc64 (#609)
+- Use `syscall` from `libc` on Linux instead of redefining it (#629)
+
+### RNGs
+- Switch `SmallRng` to use PCG (#623)
+- Implement `Pcg32` and `Pcg64Mcg` generators (#632)
+- Move ISAAC RNGs to a dedicated crate (#551)
+- Move Xorshift RNG to its own crate (#557)
+- Move ChaCha and HC128 RNGs to dedicated crates (#607, #636)
+- Remove usage of `Rc` from `ThreadRng` (#615)
+
+### Sampling and distributions
+- Implement `Rng.gen_ratio()` and `Bernoulli::new_ratio()` (#491)
+- Make `Uniform` strictly respect `f32` / `f64` high/low bounds (#477)
+- Allow `gen_range` and `Uniform` to work on non-`Copy` types (#506)
+- `Uniform` supports inclusive ranges: `Uniform::from(a..=b)`. This is
+  automatically enabled for Rust >= 1.27. (#566)
+- Implement `TrustedLen` and `FusedIterator` for `DistIter` (#620)
+
+#### New distributions
+- Add the `Dirichlet` distribution (#485)
+- Added sampling from the unit sphere and circle. (#567)
+- Implement the triangular distribution (#575)
+- Implement the Weibull distribution (#576)
+- Implement the Beta distribution (#574)
+
+#### Optimisations
+
+- Optimise `Bernoulli::new` (#500)
+- Optimise `char` sampling (#519)
+- Optimise sampling of `std::time::Duration` (#583)
+
+### Sequences
+- Redesign the `seq` module (#483, #515)
+- Add `WeightedIndex` and `choose_weighted` (#518, #547)
+- Optimised and changed return type of the `sample_indices` function. (#479)
+- Use `Iterator::size_hint()` to speed up `IteratorRandom::choose` (#593)
+
+### SIMD
+- Support for generating SIMD types (#523, #542, #561, #630)
+
+### Other
+- Revise CI scripts (#632, #635)
+- Remove functionality already deprecated in 0.5 (#499)
+- Support for `i128` and `u128` is automatically enabled for Rust >= 1.26. This
+  renders the `i128_support` feature obsolete. It still exists for backwards
+  compatibility but does not have any effect. This breaks programs using Rand
+  with `i128_support` on nightlies older than Rust 1.26. (#571)
+
+
+## [0.5.5] - 2018-08-07
+### Documentation
+- Fix links in documentation (#582)
+
+
+## [0.5.4] - 2018-07-11
+### Platform support
+- Make `OsRng` work via WASM/stdweb for WebWorkers
+
+
+## [0.5.3] - 2018-06-26
+### Platform support
+- OpenBSD, Bitrig: fix compilation (broken in 0.5.1) (#530)
+
+
+## [0.5.2] - 2018-06-18
+### Platform support
+- Hide `OsRng` and `JitterRng` on unsupported platforms (#512; fixes #503).
+
+
+## [0.5.1] - 2018-06-08
+
+### New distributions
+- Added Cauchy distribution. (#474, #486)
+- Added Pareto distribution. (#495)
+
+### Platform support and `OsRng`
+- Remove blanket Unix implementation. (#484)
+- Remove Wasm unimplemented stub. (#484)
+- Dragonfly BSD: read from `/dev/random`. (#484)
+- Bitrig: use `getentropy` like OpenBSD. (#484)
+- Solaris: (untested) use `getrandom` if available, otherwise `/dev/random`. (#484)
+- Emscripten, `stdweb`: split the read up in chunks. (#484)
+- Emscripten, Haiku: don't do an extra blocking read from `/dev/random`. (#484)
+- Linux, NetBSD, Solaris: read in blocking mode on first use in `fill_bytes`. (#484)
+- Fuchsia, CloudABI: fix compilation (broken in Rand 0.5). (#484)
+
+
+## [0.5.0] - 2018-05-21
+
+### Crate features and organisation
+- Minimum Rust version update: 1.22.0. (#239)
+- Create a separate `rand_core` crate. (#288)
+- Deprecate `rand_derive`. (#256)
+- Add `prelude` (and module reorganisation). (#435)
+- Add `log` feature. Logging is now available in `JitterRng`, `OsRng`, `EntropyRng` and `ReseedingRng`. (#246)
+- Add `serde1` feature for some PRNGs. (#189)
+- `stdweb` feature for `OsRng` support on WASM via stdweb. (#272, #336)
+
+### `Rng` trait
+- Split `Rng` in `RngCore` and `Rng` extension trait.
+  `next_u32`, `next_u64` and `fill_bytes` are now part of `RngCore`. (#265)
+- Add `Rng::sample`. (#256)
+- Deprecate `Rng::gen_weighted_bool`. (#308)
+- Add `Rng::gen_bool`. (#308)
+- Remove `Rng::next_f32` and `Rng::next_f64`. (#273)
+- Add optimized `Rng::fill` and `Rng::try_fill` methods. (#247)
+- Deprecate `Rng::gen_iter`. (#286)
+- Deprecate `Rng::gen_ascii_chars`. (#279)
+
+### `rand_core` crate
+- `rand` now depends on new `rand_core` crate (#288)
+- `RngCore` and `SeedableRng` are now part of `rand_core`. (#288)
+- Add modules to help implementing RNGs `impl` and `le`. (#209, #228)
+- Add `Error` and `ErrorKind`. (#225)
+- Add `CryptoRng` marker trait. (#273)
+- Add `BlockRngCore` trait. (#281)
+- Add `BlockRng` and `BlockRng64` wrappers to help implementations. (#281, #325)
+- Revise the `SeedableRng` trait. (#233)
+- Remove default implementations for `RngCore::next_u64` and `RngCore::fill_bytes`. (#288)
+- Add `RngCore::try_fill_bytes`. (#225)
+
+### Other traits and types
+- Add `FromEntropy` trait. (#233, #375)
+- Add `SmallRng` wrapper. (#296)
+- Rewrite `ReseedingRng` to only work with `BlockRngCore` (substantial performance improvement). (#281)
+- Deprecate `weak_rng`. Use `SmallRng` instead. (#296)
+- Deprecate `AsciiGenerator`. (#279)
+
+### Random number generators
+- Switch `StdRng` and `thread_rng` to HC-128. (#277)
+- `StdRng` must now be created with `from_entropy` instead of `new`
+- Change `thread_rng` reseeding threshold to 32 MiB. (#277)
+- PRNGs no longer implement `Copy`. (#209)
+- `Debug` implementations no longer show internals. (#209)
+- Implement `Clone` for `ReseedingRng`, `JitterRng`, OsRng`. (#383, #384)
+- Implement serialization for `XorShiftRng`, `IsaacRng` and `Isaac64Rng` under the `serde1` feature. (#189)
+- Implement `BlockRngCore` for `ChaChaCore` and `Hc128Core`. (#281)
+- All PRNGs are now portable across big- and little-endian architectures. (#209)
+- `Isaac64Rng::next_u32` no longer throws away half the results. (#209)
+- Add `IsaacRng::new_from_u64` and `Isaac64Rng::new_from_u64`. (#209)
+- Add the HC-128 CSPRNG `Hc128Rng`. (#210)
+- Change ChaCha20 to have 64-bit counter and 64-bit stream. (#349)
+- Changes to `JitterRng` to get its size down from 2112 to 24 bytes. (#251)
+- Various performance improvements to all PRNGs.
+
+### Platform support and `OsRng`
+- Add support for CloudABI. (#224)
+- Remove support for NaCl. (#225)
+- WASM support for `OsRng` via stdweb, behind the `stdweb` feature. (#272, #336)
+- Use `getrandom` on more platforms for Linux, and on Android. (#338)
+- Use the `SecRandomCopyBytes` interface on macOS. (#322)
+- On systems that do not have a syscall interface, only keep a single file descriptor open for `OsRng`. (#239)
+- On Unix, first try a single read from `/dev/random`, then `/dev/urandom`. (#338)
+- Better error handling and reporting in `OsRng` (using new error type). (#225)
+- `OsRng` now uses non-blocking when available. (#225)
+- Add `EntropyRng`, which provides `OsRng`, but has `JitterRng` as a fallback. (#235)
+
+### Distributions
+- New `Distribution` trait. (#256)
+- Add `Distribution::sample_iter` and `Rng::::sample_iter`. (#361)
+- Deprecate `Rand`, `Sample` and `IndependentSample` traits. (#256)
+- Add a `Standard` distribution (replaces most `Rand` implementations). (#256)
+- Add `Binomial` and `Poisson` distributions. (#96)
+- Add `Bernoulli` dsitribution. (#411)
+- Add `Alphanumeric` distribution. (#279)
+- Remove `Closed01` distribution, add `OpenClosed01`. (#274, #420)
+- Rework `Range` type, making it possible to implement it for user types. (#274)
+- Rename `Range` to `Uniform`. (#395)
+- Add `Uniform::new_inclusive` for inclusive ranges. (#274)
+- Use widening multiply method for much faster integer range reduction. (#274)
+- `Standard` distribution for `char` uses `Uniform` internally. (#274)
+- `Standard` distribution for `bool` uses sign test. (#274)
+- Implement `Standard` distribution for `Wrapping<T>`. (#436)
+- Implement `Uniform` distribution for `Duration`. (#427)
+
 
 ## [0.4.3] - 2018-08-16
 ### Fixed
 - Use correct syscall number for PowerPC (#589)
 
-## [0.4.2] - 2018-01-05
+
+## [0.4.2] - 2018-01-06
 ### Changed
-- Use winapi on Windows
+- Use `winapi` on Windows
 - Update for Fuchsia OS
 - Remove dev-dependency on `log`
 
+
 ## [0.4.1] - 2017-12-17
 ### Added
 - `no_std` support
 
+
 ## [0.4.0-pre.0] - 2017-12-11
 ### Added
 - `JitterRng` added as a high-quality alternative entropy source using the
@@ -33,6 +235,20 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Deprecated
   - `sample` function deprecated (replaced by `sample_iter`)
 
+
+## [0.3.20] - 2018-01-06
+### Changed
+- Remove dev-dependency on `log`
+- Update `fuchsia-zircon` dependency to 0.3.2
+
+
+## [0.3.19] - 2017-12-27
+### Changed
+- Require `log <= 0.3.8` for dev builds
+- Update `fuchsia-zircon` dependency to 0.3
+- Fix broken links in docs (to unblock compiler docs testing CI)
+
+
 ## [0.3.18] - 2017-11-06
 ### Changed
 - `thread_rng` is seeded from the system time if `OsRng` fails
@@ -181,7 +397,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Compatible with Rust master
 
 ### Removed
-- Removed Copy inplementaions from RNGs
+- Removed Copy implementations from RNGs
 
 
 ## [0.1.2] - 2015-02-03
@@ -227,7 +443,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - `Rng::gen_ascii_chars()` which will return an infinite stream of random ascii characters
 
 ### Changed
-- Now only depends on libcore!   2adf5363f88ffe06f6d2ea5c338d1b186d47f4a1
+- Now only depends on libcore!
 - Remove `Rng.choose()`, rename `Rng.choose_option()` to `.choose()`
 - Rename OSRng to OsRng
 - The WeightedChoice structure is no longer built with a `Vec<Weighted<T>>`,
@@ -266,4 +482,3 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## [0.10-pre] - 2014-03-02
 ### Added
 - Seperate `rand` out of the standard library
-
diff --git a/rand/COPYRIGHT b/rand/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/Cargo.toml b/rand/Cargo.toml
index c21f53e..5f95c37 100644
--- a/rand/Cargo.toml
+++ b/rand/Cargo.toml
@@ -1,35 +1,76 @@
 [package]
 name = "rand"
-version = "0.4.3"
-authors = ["The Rust Project Developers"]
+version = "0.6.1"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
 license = "MIT/Apache-2.0"
 readme = "README.md"
-repository = "https://github.com/rust-lang-nursery/rand"
-documentation = "https://docs.rs/rand"
-homepage = "https://github.com/rust-lang-nursery/rand"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand"
+homepage = "https://crates.io/crates/rand"
 description = """
 Random number generators and other randomness functionality.
 """
 keywords = ["random", "rng"]
-categories = ["algorithms"]
+categories = ["algorithms", "no-std"]
+build = "build.rs"
+exclude = ["/utils/*", "/.travis.yml", "/appveyor.yml", ".gitignore"]
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
 
 [features]
-default = ["std"]
-nightly = ["i128_support"] # enables all features requiring nightly rust
+default = ["std" ] # without "std" rand uses libcore
+nightly = ["simd_support"] # enables all features requiring nightly rust
+std = ["rand_core/std", "alloc", "libc", "winapi", "cloudabi", "fuchsia-zircon"]
+alloc = ["rand_core/alloc"]  # enables Vec and Box support (without std)
+i128_support = [] # enables i128 and u128 support
+simd_support = ["packed_simd"] # enables SIMD support
+serde1 = ["rand_core/serde1", "rand_isaac/serde1", "rand_xorshift/serde1"] # enables serialization for PRNGs
 
-std = ["libc"] # default feature; without this rand uses libcore
-alloc = []  # enables Vec and Box support without std
+[workspace]
+members = ["rand_core", "rand_isaac", "rand_chacha", "rand_hc", "rand_pcg", "rand_xorshift"]
 
-i128_support = [] # enables i128 and u128 support
+[dependencies]
+rand_core = { path = "rand_core", version = "0.3", default-features = false }
+rand_pcg = { path = "rand_pcg", version = "0.1" }
+# only for deprecations and benches:
+rand_isaac = { path = "rand_isaac", version = "0.1" }
+rand_chacha = { path = "rand_chacha", version = "0.1" }
+rand_hc = { path = "rand_hc", version = "0.1" }
+rand_xorshift = { path = "rand_xorshift", version = "0.1" }
+log = { version = "0.4", optional = true }
+
+[dependencies.packed_simd]
+# NOTE: so far no version works reliably due to dependence on unstable features
+version = "0.3"
+# git = "https://github.com/rust-lang-nursery/packed_simd"
+optional = true
+features = ["into_bits"]
 
 [target.'cfg(unix)'.dependencies]
-libc = { version = "0.2", optional = true }
+libc = { version = "0.2", optional = true, default-features = false }
 
 [target.'cfg(windows)'.dependencies]
-winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "profileapi", "winnt"] }
+winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "profileapi", "winnt"], optional = true }
 
-[workspace]
-members = ["rand-derive"]
+[target.'cfg(target_os = "cloudabi")'.dependencies]
+cloudabi = { version = "0.0.3", optional = true }
 
 [target.'cfg(target_os = "fuchsia")'.dependencies]
-fuchsia-zircon = "0.3.2"
+fuchsia-zircon = { version = "0.3.2", optional = true }
+
+[target.wasm32-unknown-unknown.dependencies]
+# use with `--target wasm32-unknown-unknown --features=stdweb`
+stdweb = { version = "0.4", optional = true }
+wasm-bindgen = { version = "0.2.12", optional = true }
+
+[dev-dependencies]
+# This has a histogram implementation used for testing uniformity.
+average = "0.9.2"
+
+[build-dependencies]
+rustc_version = "0.2"
+
+[package.metadata.docs.rs]
+all-features = true
diff --git a/rand/LICENSE-APACHE b/rand/LICENSE-APACHE
index 16fe87b..17d7468 100644
--- a/rand/LICENSE-APACHE
+++ b/rand/LICENSE-APACHE
@@ -1,6 +1,6 @@
                               Apache License
                         Version 2.0, January 2004
-                     http://www.apache.org/licenses/
+                     https://www.apache.org/licenses/
 
 TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
 
@@ -192,7 +192,7 @@ Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
-	http://www.apache.org/licenses/LICENSE-2.0
+	https://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
diff --git a/rand/LICENSE-MIT b/rand/LICENSE-MIT
index 39d4bdb..d93b5ba 100644
--- a/rand/LICENSE-MIT
+++ b/rand/LICENSE-MIT
@@ -1,3 +1,4 @@
+Copyright 2018 Developers of the Rand project
 Copyright (c) 2014 The Rust Project Developers
 
 Permission is hereby granted, free of charge, to any
diff --git a/rand/README.md b/rand/README.md
index f72bd51..95970af 100644
--- a/rand/README.md
+++ b/rand/README.md
@@ -1,12 +1,28 @@
-rand
-====
+# Rand
 
-A Rust library for random number generators and other randomness functionality.
+[![Build Status](https://travis-ci.org/rust-random/rand.svg?branch=master)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Crate](https://img.shields.io/crates/v/rand.svg)](https://crates.io/crates/rand)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand)
+[![API](https://docs.rs/rand/badge.svg)](https://docs.rs/rand)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
 
-[![Build Status](https://travis-ci.org/rust-lang-nursery/rand.svg?branch=master)](https://travis-ci.org/rust-lang-nursery/rand)
-[![Build status](https://ci.appveyor.com/api/projects/status/rm5c9o33k3jhchbw?svg=true)](https://ci.appveyor.com/project/alexcrichton/rand)
+A Rust library for random number generation.
+
+Rand provides utilities to generate random numbers, to convert them to useful
+types and distributions, and some randomness-related algorithms.
+
+The core random number generation traits of Rand live in the [rand_core](
+https://crates.io/crates/rand_core) crate but are also exposed here; RNG
+implementations should prefer to use `rand_core` while most other users should
+depend on `rand`.
+
+Documentation:
+-   [The Rust Rand Book](https://rust-random.github.io/book)
+-   [API reference (master)](https://rust-random.github.io/rand)
+-   [API reference (docs.rs)](https://docs.rs/rand)
 
-[Documentation](https://docs.rs/rand)
 
 ## Usage
 
@@ -14,126 +30,86 @@ Add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-rand = "0.4"
+rand = "0.6"
 ```
 
-and this to your crate root:
+To get started using Rand, see [The Book](https://rust-random.github.io/book).
 
-```rust
-extern crate rand;
-```
 
-### Versions
+## Versions
 
-Version `0.4`was released in December 2017. It contains almost no breaking
-changes since the `0.3` series, but nevertheless contains some significant
-new code, including a new "external" entropy source (`JitterRng`) and `no_std`
-support.
+The Rand lib is not yet stable, however we are careful to limit breaking changes
+and warn via deprecation wherever possible. Patch versions never introduce
+breaking changes. The following minor versions are supported:
 
-Version `0.5` is in development and contains significant performance
-improvements for the ISAAC random number generators.
+-   Version 0.6 was released in November 2018, redesigning the `seq` module,
+    moving most PRNGs to external crates, and many small changes.
+-   Version 0.5 was released in May 2018, as a major reorganisation
+    (introducing `RngCore` and `rand_core`, and deprecating `Rand` and the
+    previous distribution traits).
+-   Version 0.4 was released in December 2017, but contained almost no breaking
+    changes from the 0.3 series.
 
-## Examples
+A detailed [changelog](CHANGELOG.md) is available.
 
-There is built-in support for a random number generator (RNG) associated with each thread stored in thread-local storage. This RNG can be accessed via thread_rng, or used implicitly via random. This RNG is normally randomly seeded from an operating-system source of randomness, e.g. /dev/urandom on Unix systems, and will automatically reseed itself from this source after generating 32 KiB of random data.
+When upgrading to the next minor series (especially 0.4 → 0.5), we recommend
+reading the [Upgrade Guide](https://rust-random.github.io/book/update.html).
 
-```rust
-let tuple = rand::random::<(f64, char)>();
-println!("{:?}", tuple)
-```
+### Rust version requirements
 
-```rust
-use rand::Rng;
+Since version 0.5, Rand requires **Rustc version 1.22 or greater**.
+Rand 0.4 and 0.3 (since approx. June 2017) require Rustc version 1.15 or
+greater. Subsets of the Rand code may work with older Rust versions, but this
+is not supported.
 
-let mut rng = rand::thread_rng();
-if rng.gen() { // random bool
-    println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
-}
-```
+Travis CI always has a build with a pinned version of Rustc matching the oldest
+supported Rust release. The current policy is that this can be updated in any
+Rand release if required, but the change must be noted in the changelog.
 
-It is also possible to use other RNG types, which have a similar interface. The following uses the "ChaCha" algorithm instead of the default.
+To avoid bumping the required version unnecessarily, we use a `build.rs` script
+to auto-detect the compiler version and enable certain features or change code
+paths automatically. Since this makes it easy to unintentionally make use of
+features requiring a more recent Rust version, we recommend testing with a
+pinned version of Rustc if you require compatibility with a specific version.
 
-```rust
-use rand::{Rng, ChaChaRng};
+## Crate Features
 
-let mut rng = rand::ChaChaRng::new_unseeded();
-println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
-```
-
-## Features
-
-By default, `rand` is built with all stable features available. The following
+Rand is built with only the `std` feature enabled by default. The following
 optional features are available:
 
--   `i128_support` enables support for generating `u128` and `i128` values
--   `nightly` enables all unstable features (`i128_support`)
--   `std` enabled by default; by setting "default-features = false" `no_std`
-    mode is activated; this removes features depending on `std` functionality:
-    
-        -   `OsRng` is entirely unavailable
-        -   `JitterRng` code is still present, but a nanosecond timer must be
-            provided via `JitterRng::new_with_timer`
-        -   Since no external entropy is available, it is not possible to create
-            generators with fresh seeds (user must provide entropy)
-        -   `thread_rng`, `weak_rng` and `random` are all disabled
-        -   exponential, normal and gamma type distributions are unavailable
-            since `exp` and `log` functions are not provided in `core`
-        -   any code requiring `Vec` or `Box`
--   `alloc` can be used instead of `std` to provide `Vec` and `Box`
-
-## Testing
-
-Unfortunately, `cargo test` does not test everything. The following tests are
-recommended:
-
-```
-# Basic tests for rand and sub-crates
-cargo test --all
-
-# Test no_std support (build only since nearly all tests require std)
-cargo build --all --no-default-features
-
-# Test 128-bit support (requires nightly)
-cargo test --all --features nightly
-
-# Benchmarks (requires nightly)
-cargo bench
-# or just to test the benchmark code:
-cargo test --benches
-```
-
-# `derive(Rand)`
-
-You can derive the `Rand` trait for your custom type via the `#[derive(Rand)]`
-directive. To use this first add this to your Cargo.toml:
-
-```toml
-rand = "0.4"
-rand_derive = "0.3"
-```
-
-Next in your crate:
-
-```rust
-extern crate rand;
-#[macro_use]
-extern crate rand_derive;
-
-#[derive(Rand, Debug)]
-struct MyStruct {
-    a: i32,
-    b: u32,
-}
-
-fn main() {
-    println!("{:?}", rand::random::<MyStruct>());
-}
-```
+- `alloc` can be used instead of `std` to provide `Vec` and `Box`.
+- `log` enables some logging via the `log` crate.
+- `nightly` enables all unstable features (`simd_support`).
+- `serde1` enables serialization for some types, via Serde version 1.
+- `simd_support` enables uniform sampling of SIMD types (integers and floats).
+- `stdweb` enables support for `OsRng` on `wasm32-unknown-unknown` via `stdweb`
+  combined with `cargo-web`.
+- `wasm-bindgen` enables support for `OsRng` on `wasm32-unknown-unknown` via
+  [`wasm-bindgen`]
+
+[`wasm-bindgen`]: https://github.com/rustwasm/wasm-bindgen
+
+`no_std` mode is activated by setting `default-features = false`; this removes
+functionality depending on `std`:
+
+- `thread_rng()`, and `random()` are not available, as they require thread-local
+  storage and an entropy source.
+- `OsRng` and `EntropyRng` are unavailable.
+- `JitterRng` code is still present, but a nanosecond timer must be provided via
+  `JitterRng::new_with_timer`
+- Since no external entropy is available, it is not possible to create
+  generators with fresh seeds using the `FromEntropy` trait (user must provide
+  a seed).
+- Several non-linear distributions distributions are unavailable since `exp`
+  and `log` functions are not provided in `core`.
+- Large parts of the `seq`-uence module are unavailable, unless the `alloc`
+  feature is used (several APIs and many implementations require `Vec`).
 
 
 # License
 
-`rand` is primarily distributed under the terms of both the MIT
-license and the Apache License (Version 2.0).
+Rand is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
 
-See LICENSE-APACHE, and LICENSE-MIT for details.
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/appveyor.yml b/rand/appveyor.yml
index 02e217f..a0e518e 100644
--- a/rand/appveyor.yml
+++ b/rand/appveyor.yml
@@ -32,7 +32,21 @@ install:
 build: false
 
 test_script:
-  - cargo test --benches
-  - cargo test
-  - cargo test --features nightly
-  - cargo test --manifest-path rand-derive/Cargo.toml
+  - cargo test --lib --no-default-features --features alloc
+  # TODO: use --all-features once simd_support is sufficiently stable:
+  - cargo test --features=serde1,log
+  - cargo test --benches --features=nightly
+  - cargo test --examples
+  - cargo test --package rand_core
+  - cargo test --package rand_core --no-default-features --features=alloc
+  - cargo test --package rand_isaac --features=serde1
+  - cargo test --package rand_xorshift --features=serde1
+  - cargo test --package rand_chacha
+  - cargo test --package rand_hc
+  - cargo test --manifest-path rand_core/Cargo.toml
+  - cargo test --manifest-path rand_core/Cargo.toml --no-default-features --features=alloc
+  - cargo test --manifest-path rand_isaac/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_pcg/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_xorshift/Cargo.toml --features=serde1
+  - cargo test --manifest-path rand_chacha/Cargo.toml
+  - cargo test --manifest-path rand_hc/Cargo.toml
diff --git a/rand/benches/bench.rs b/rand/benches/bench.rs
deleted file mode 100644
index d396f25..0000000
--- a/rand/benches/bench.rs
+++ /dev/null
@@ -1,34 +0,0 @@
-#![feature(test)]
-
-extern crate test;
-extern crate rand;
-
-const RAND_BENCH_N: u64 = 1000;
-
-mod distributions;
-
-use std::mem::size_of;
-use test::{black_box, Bencher};
-use rand::{StdRng, Rng};
-
-#[bench]
-fn rand_f32(b: &mut Bencher) {
-    let mut rng = StdRng::new().unwrap();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.next_f32());
-        }
-    });
-    b.bytes = size_of::<f32>() as u64 * RAND_BENCH_N;
-}
-
-#[bench]
-fn rand_f64(b: &mut Bencher) {
-    let mut rng = StdRng::new().unwrap();
-    b.iter(|| {
-        for _ in 0..RAND_BENCH_N {
-            black_box(rng.next_f64());
-        }
-    });
-    b.bytes = size_of::<f64>() as u64 * RAND_BENCH_N;
-}
diff --git a/rand/benches/distributions.rs b/rand/benches/distributions.rs
new file mode 100644
index 0000000..7ac1a6a
--- /dev/null
+++ b/rand/benches/distributions.rs
@@ -0,0 +1,237 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(test)]
+
+extern crate test;
+extern crate rand;
+
+const RAND_BENCH_N: u64 = 1000;
+
+use std::mem::size_of;
+use test::Bencher;
+use std::time::Duration;
+
+use rand::{Rng, FromEntropy};
+use rand::rngs::SmallRng;
+use rand::distributions::*;
+
+macro_rules! distr_int {
+    ($fnn:ident, $ty:ty, $distr:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+            let distr = $distr;
+
+            b.iter(|| {
+                let mut accum = 0 as $ty;
+                for _ in 0..::RAND_BENCH_N {
+                    let x: $ty = distr.sample(&mut rng);
+                    accum = accum.wrapping_add(x);
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+macro_rules! distr_float {
+    ($fnn:ident, $ty:ty, $distr:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+            let distr = $distr;
+
+            b.iter(|| {
+                let mut accum = 0.0;
+                for _ in 0..::RAND_BENCH_N {
+                    let x: $ty = distr.sample(&mut rng);
+                    accum += x;
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+macro_rules! distr_duration {
+    ($fnn:ident, $distr:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+            let distr = $distr;
+
+            b.iter(|| {
+                let mut accum = Duration::new(0, 0);
+                for _ in 0..::RAND_BENCH_N {
+                    let x: Duration = distr.sample(&mut rng);
+                    accum = accum.checked_add(x).unwrap_or(Duration::new(u64::max_value(), 999_999_999));
+                }
+                accum
+            });
+            b.bytes = size_of::<Duration>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+macro_rules! distr {
+    ($fnn:ident, $ty:ty, $distr:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+            let distr = $distr;
+
+            b.iter(|| {
+                let mut accum = 0u32;
+                for _ in 0..::RAND_BENCH_N {
+                    let x: $ty = distr.sample(&mut rng);
+                    accum = accum.wrapping_add(x as u32);
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+// uniform
+distr_int!(distr_uniform_i8, i8, Uniform::new(20i8, 100));
+distr_int!(distr_uniform_i16, i16, Uniform::new(-500i16, 2000));
+distr_int!(distr_uniform_i32, i32, Uniform::new(-200_000_000i32, 800_000_000));
+distr_int!(distr_uniform_i64, i64, Uniform::new(3i64, 123_456_789_123));
+distr_int!(distr_uniform_i128, i128, Uniform::new(-123_456_789_123i128, 123_456_789_123_456_789));
+
+distr_float!(distr_uniform_f32, f32, Uniform::new(2.26f32, 2.319));
+distr_float!(distr_uniform_f64, f64, Uniform::new(2.26f64, 2.319));
+
+const LARGE_SEC: u64 = u64::max_value() / 1000;
+
+distr_duration!(distr_uniform_duration_largest,
+    Uniform::new_inclusive(Duration::new(0, 0), Duration::new(u64::max_value(), 999_999_999))
+);
+distr_duration!(distr_uniform_duration_large,
+    Uniform::new(Duration::new(0, 0), Duration::new(LARGE_SEC, 1_000_000_000 / 2))
+);
+distr_duration!(distr_uniform_duration_one,
+    Uniform::new(Duration::new(0, 0), Duration::new(1, 0))
+);
+distr_duration!(distr_uniform_duration_variety,
+    Uniform::new(Duration::new(10000, 423423), Duration::new(200000, 6969954))
+);
+distr_duration!(distr_uniform_duration_edge,
+    Uniform::new_inclusive(Duration::new(LARGE_SEC, 999_999_999), Duration::new(LARGE_SEC + 1, 1))
+);
+
+
+// standard
+distr_int!(distr_standard_i8, i8, Standard);
+distr_int!(distr_standard_i16, i16, Standard);
+distr_int!(distr_standard_i32, i32, Standard);
+distr_int!(distr_standard_i64, i64, Standard);
+distr_int!(distr_standard_i128, i128, Standard);
+
+distr!(distr_standard_bool, bool, Standard);
+distr!(distr_standard_alphanumeric, char, Alphanumeric);
+distr!(distr_standard_codepoint, char, Standard);
+
+distr_float!(distr_standard_f32, f32, Standard);
+distr_float!(distr_standard_f64, f64, Standard);
+distr_float!(distr_open01_f32, f32, Open01);
+distr_float!(distr_open01_f64, f64, Open01);
+distr_float!(distr_openclosed01_f32, f32, OpenClosed01);
+distr_float!(distr_openclosed01_f64, f64, OpenClosed01);
+
+// distributions
+distr_float!(distr_exp, f64, Exp::new(1.23 * 4.56));
+distr_float!(distr_normal, f64, Normal::new(-1.23, 4.56));
+distr_float!(distr_log_normal, f64, LogNormal::new(-1.23, 4.56));
+distr_float!(distr_gamma_large_shape, f64, Gamma::new(10., 1.0));
+distr_float!(distr_gamma_small_shape, f64, Gamma::new(0.1, 1.0));
+distr_float!(distr_cauchy, f64, Cauchy::new(4.2, 6.9));
+distr_int!(distr_binomial, u64, Binomial::new(20, 0.7));
+distr_int!(distr_poisson, u64, Poisson::new(4.0));
+distr!(distr_bernoulli, bool, Bernoulli::new(0.18));
+
+// Weighted
+distr_int!(distr_weighted_i8, usize, WeightedIndex::new(&[1i8, 2, 3, 4, 12, 0, 2, 1]).unwrap());
+distr_int!(distr_weighted_u32, usize, WeightedIndex::new(&[1u32, 2, 3, 4, 12, 0, 2, 1]).unwrap());
+distr_int!(distr_weighted_f64, usize, WeightedIndex::new(&[1.0f64, 0.001, 1.0/3.0, 4.01, 0.0, 3.3, 22.0, 0.001]).unwrap());
+distr_int!(distr_weighted_large_set, usize, WeightedIndex::new((0..10000).rev().chain(1..10001)).unwrap());
+
+// construct and sample from a range
+macro_rules! gen_range_int {
+    ($fnn:ident, $ty:ident, $low:expr, $high:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+
+            b.iter(|| {
+                let mut high = $high;
+                let mut accum: $ty = 0;
+                for _ in 0..::RAND_BENCH_N {
+                    accum = accum.wrapping_add(rng.gen_range($low, high));
+                    // force recalculation of range each time
+                    high = high.wrapping_add(1) & std::$ty::MAX;
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+gen_range_int!(gen_range_i8, i8, -20i8, 100);
+gen_range_int!(gen_range_i16, i16, -500i16, 2000);
+gen_range_int!(gen_range_i32, i32, -200_000_000i32, 800_000_000);
+gen_range_int!(gen_range_i64, i64, 3i64, 123_456_789_123);
+gen_range_int!(gen_range_i128, i128, -12345678901234i128, 123_456_789_123_456_789);
+
+// construct and sample from a floating-point range
+macro_rules! gen_range_float {
+    ($fnn:ident, $ty:ident, $low:expr, $high:expr) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = SmallRng::from_entropy();
+
+            b.iter(|| {
+                let mut high = $high;
+                let mut low = $low;
+                let mut accum: $ty = 0.0;
+                for _ in 0..::RAND_BENCH_N {
+                    accum += rng.gen_range(low, high);
+                    // force recalculation of range each time
+                    low += 0.9;
+                    high += 1.1;
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * ::RAND_BENCH_N;
+        }
+    }
+}
+
+gen_range_float!(gen_range_f32, f32, -20000.0f32, 100000.0);
+gen_range_float!(gen_range_f64, f64, 123.456f64, 7890.12);
+
+#[bench]
+fn dist_iter(b: &mut Bencher) {
+    let mut rng = SmallRng::from_entropy();
+    let distr = Normal::new(-2.71828, 3.14159);
+    let mut iter = distr.sample_iter(&mut rng);
+
+    b.iter(|| {
+        let mut accum = 0.0;
+        for _ in 0..::RAND_BENCH_N {
+            accum += iter.next().unwrap();
+        }
+        accum
+    });
+    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
+}
diff --git a/rand/benches/distributions/exponential.rs b/rand/benches/distributions/exponential.rs
deleted file mode 100644
index 152615d..0000000
--- a/rand/benches/distributions/exponential.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-use std::mem::size_of;
-use test::Bencher;
-use rand;
-use rand::distributions::exponential::Exp;
-use rand::distributions::Sample;
-
-#[bench]
-fn rand_exp(b: &mut Bencher) {
-    let mut rng = rand::weak_rng();
-    let mut exp = Exp::new(2.71828 * 3.14159);
-
-    b.iter(|| {
-        for _ in 0..::RAND_BENCH_N {
-            exp.sample(&mut rng);
-        }
-    });
-    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
-}
diff --git a/rand/benches/distributions/gamma.rs b/rand/benches/distributions/gamma.rs
deleted file mode 100644
index bf3fd36..0000000
--- a/rand/benches/distributions/gamma.rs
+++ /dev/null
@@ -1,31 +0,0 @@
-use std::mem::size_of;
-use test::Bencher;
-use rand;
-use rand::distributions::IndependentSample;
-use rand::distributions::gamma::Gamma;
-
-#[bench]
-fn bench_gamma_large_shape(b: &mut Bencher) {
-    let gamma = Gamma::new(10., 1.0);
-    let mut rng = rand::weak_rng();
-
-    b.iter(|| {
-        for _ in 0..::RAND_BENCH_N {
-            gamma.ind_sample(&mut rng);
-        }
-    });
-    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
-}
-
-#[bench]
-fn bench_gamma_small_shape(b: &mut Bencher) {
-    let gamma = Gamma::new(0.1, 1.0);
-    let mut rng = rand::weak_rng();
-
-    b.iter(|| {
-        for _ in 0..::RAND_BENCH_N {
-            gamma.ind_sample(&mut rng);
-        }
-    });
-    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
-}
diff --git a/rand/benches/distributions/mod.rs b/rand/benches/distributions/mod.rs
deleted file mode 100644
index 49f6bd9..0000000
--- a/rand/benches/distributions/mod.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-mod exponential;
-mod normal;
-mod gamma;
diff --git a/rand/benches/distributions/normal.rs b/rand/benches/distributions/normal.rs
deleted file mode 100644
index 1c858b1..0000000
--- a/rand/benches/distributions/normal.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-use std::mem::size_of;
-use test::Bencher;
-use rand;
-use rand::distributions::Sample;
-use rand::distributions::normal::Normal;
-
-#[bench]
-fn rand_normal(b: &mut Bencher) {
-    let mut rng = rand::weak_rng();
-    let mut normal = Normal::new(-2.71828, 3.14159);
-
-    b.iter(|| {
-        for _ in 0..::RAND_BENCH_N {
-            normal.sample(&mut rng);
-        }
-    });
-    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
-}
diff --git a/rand/benches/generators.rs b/rand/benches/generators.rs
index daee7c5..a12b5a6 100644
--- a/rand/benches/generators.rs
+++ b/rand/benches/generators.rs
@@ -1,7 +1,20 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
 #![feature(test)]
 
 extern crate test;
 extern crate rand;
+extern crate rand_isaac;
+extern crate rand_chacha;
+extern crate rand_hc;
+extern crate rand_pcg;
+extern crate rand_xorshift;
 
 const RAND_BENCH_N: u64 = 1000;
 const BYTES_LEN: usize = 1024;
@@ -9,31 +22,20 @@ const BYTES_LEN: usize = 1024;
 use std::mem::size_of;
 use test::{black_box, Bencher};
 
-use rand::{Rng, StdRng, OsRng, JitterRng};
-use rand::{XorShiftRng, IsaacRng, Isaac64Rng, ChaChaRng};
+use rand::prelude::*;
+use rand::rngs::adapter::ReseedingRng;
+use rand::rngs::{OsRng, JitterRng, EntropyRng};
+use rand_isaac::{IsaacRng, Isaac64Rng};
+use rand_chacha::ChaChaRng;
+use rand_hc::{Hc128Rng, Hc128Core};
+use rand_pcg::{Lcg64Xsh32, Mcg128Xsl64};
+use rand_xorshift::XorShiftRng;
 
 macro_rules! gen_bytes {
-    ($fnn:ident, $gen:ident) => {
-        #[bench]
-        fn $fnn(b: &mut Bencher) {
-            let mut rng: $gen = OsRng::new().unwrap().gen();
-            let mut buf = [0u8; BYTES_LEN];
-            b.iter(|| {
-                for _ in 0..RAND_BENCH_N {
-                    rng.fill_bytes(&mut buf);
-                    black_box(buf);
-                }
-            });
-            b.bytes = BYTES_LEN as u64 * RAND_BENCH_N;
-        }
-    }
-}
-
-macro_rules! gen_bytes_new {
-    ($fnn:ident, $gen:ident) => {
+    ($fnn:ident, $gen:expr) => {
         #[bench]
         fn $fnn(b: &mut Bencher) {
-            let mut rng = $gen::new().unwrap();
+            let mut rng = $gen;
             let mut buf = [0u8; BYTES_LEN];
             b.iter(|| {
                 for _ in 0..RAND_BENCH_N {
@@ -46,63 +48,63 @@ macro_rules! gen_bytes_new {
     }
 }
 
-gen_bytes!(gen_bytes_xorshift, XorShiftRng);
-gen_bytes!(gen_bytes_isaac, IsaacRng);
-gen_bytes!(gen_bytes_isaac64, Isaac64Rng);
-gen_bytes!(gen_bytes_chacha, ChaChaRng);
-gen_bytes_new!(gen_bytes_std, StdRng);
-gen_bytes_new!(gen_bytes_os, OsRng);
-
+gen_bytes!(gen_bytes_xorshift, XorShiftRng::from_entropy());
+gen_bytes!(gen_bytes_lcg64_xsh32, Lcg64Xsh32::from_entropy());
+gen_bytes!(gen_bytes_mcg128_xsh64, Mcg128Xsl64::from_entropy());
+gen_bytes!(gen_bytes_chacha20, ChaChaRng::from_entropy());
+gen_bytes!(gen_bytes_hc128, Hc128Rng::from_entropy());
+gen_bytes!(gen_bytes_isaac, IsaacRng::from_entropy());
+gen_bytes!(gen_bytes_isaac64, Isaac64Rng::from_entropy());
+gen_bytes!(gen_bytes_std, StdRng::from_entropy());
+gen_bytes!(gen_bytes_small, SmallRng::from_entropy());
+gen_bytes!(gen_bytes_os, OsRng::new().unwrap());
 
 macro_rules! gen_uint {
-    ($fnn:ident, $ty:ty, $gen:ident) => {
-        #[bench]
-        fn $fnn(b: &mut Bencher) {
-            let mut rng: $gen = OsRng::new().unwrap().gen();
-            b.iter(|| {
-                for _ in 0..RAND_BENCH_N {
-                    black_box(rng.gen::<$ty>());
-                }
-            });
-            b.bytes = size_of::<$ty>() as u64 * RAND_BENCH_N;
-        }
-    }
-}
-
-macro_rules! gen_uint_new {
-    ($fnn:ident, $ty:ty, $gen:ident) => {
+    ($fnn:ident, $ty:ty, $gen:expr) => {
         #[bench]
         fn $fnn(b: &mut Bencher) {
-            let mut rng = $gen::new().unwrap();
+            let mut rng = $gen;
             b.iter(|| {
+                let mut accum: $ty = 0;
                 for _ in 0..RAND_BENCH_N {
-                    black_box(rng.gen::<$ty>());
+                    accum = accum.wrapping_add(rng.gen::<$ty>());
                 }
+                accum
             });
             b.bytes = size_of::<$ty>() as u64 * RAND_BENCH_N;
         }
     }
 }
 
-gen_uint!(gen_u32_xorshift, u32, XorShiftRng);
-gen_uint!(gen_u32_isaac, u32, IsaacRng);
-gen_uint!(gen_u32_isaac64, u32, Isaac64Rng);
-gen_uint!(gen_u32_chacha, u32, ChaChaRng);
-gen_uint_new!(gen_u32_std, u32, StdRng);
-gen_uint_new!(gen_u32_os, u32, OsRng);
-
-gen_uint!(gen_u64_xorshift, u64, XorShiftRng);
-gen_uint!(gen_u64_isaac, u64, IsaacRng);
-gen_uint!(gen_u64_isaac64, u64, Isaac64Rng);
-gen_uint!(gen_u64_chacha, u64, ChaChaRng);
-gen_uint_new!(gen_u64_std, u64, StdRng);
-gen_uint_new!(gen_u64_os, u64, OsRng);
-
+gen_uint!(gen_u32_xorshift, u32, XorShiftRng::from_entropy());
+gen_uint!(gen_u32_lcg64_xsh32, u32, Lcg64Xsh32::from_entropy());
+gen_uint!(gen_u32_mcg128_xsh64, u32, Mcg128Xsl64::from_entropy());
+gen_uint!(gen_u32_chacha20, u32, ChaChaRng::from_entropy());
+gen_uint!(gen_u32_hc128, u32, Hc128Rng::from_entropy());
+gen_uint!(gen_u32_isaac, u32, IsaacRng::from_entropy());
+gen_uint!(gen_u32_isaac64, u32, Isaac64Rng::from_entropy());
+gen_uint!(gen_u32_std, u32, StdRng::from_entropy());
+gen_uint!(gen_u32_small, u32, SmallRng::from_entropy());
+gen_uint!(gen_u32_os, u32, OsRng::new().unwrap());
+
+gen_uint!(gen_u64_xorshift, u64, XorShiftRng::from_entropy());
+gen_uint!(gen_u64_lcg64_xsh32, u64, Lcg64Xsh32::from_entropy());
+gen_uint!(gen_u64_mcg128_xsh64, u64, Mcg128Xsl64::from_entropy());
+gen_uint!(gen_u64_chacha20, u64, ChaChaRng::from_entropy());
+gen_uint!(gen_u64_hc128, u64, Hc128Rng::from_entropy());
+gen_uint!(gen_u64_isaac, u64, IsaacRng::from_entropy());
+gen_uint!(gen_u64_isaac64, u64, Isaac64Rng::from_entropy());
+gen_uint!(gen_u64_std, u64, StdRng::from_entropy());
+gen_uint!(gen_u64_small, u64, SmallRng::from_entropy());
+gen_uint!(gen_u64_os, u64, OsRng::new().unwrap());
+
+// Do not test JitterRng like the others by running it RAND_BENCH_N times per,
+// measurement, because it is way too slow. Only run it once.
 #[bench]
 fn gen_u64_jitter(b: &mut Bencher) {
     let mut rng = JitterRng::new().unwrap();
     b.iter(|| {
-        black_box(rng.gen::<u64>());
+        rng.gen::<u64>()
     });
     b.bytes = size_of::<u64>() as u64;
 }
@@ -111,16 +113,19 @@ macro_rules! init_gen {
     ($fnn:ident, $gen:ident) => {
         #[bench]
         fn $fnn(b: &mut Bencher) {
-            let mut rng: XorShiftRng = OsRng::new().unwrap().gen();
+            let mut rng = XorShiftRng::from_entropy();
             b.iter(|| {
-                let r2: $gen = rng.gen();
-                black_box(r2);
+                let r2 = $gen::from_rng(&mut rng).unwrap();
+                r2
             });
         }
     }
 }
 
 init_gen!(init_xorshift, XorShiftRng);
+init_gen!(init_lcg64_xsh32, Lcg64Xsh32);
+init_gen!(init_mcg128_xsh64, Mcg128Xsl64);
+init_gen!(init_hc128, Hc128Rng);
 init_gen!(init_isaac, IsaacRng);
 init_gen!(init_isaac64, Isaac64Rng);
 init_gen!(init_chacha, ChaChaRng);
@@ -128,6 +133,68 @@ init_gen!(init_chacha, ChaChaRng);
 #[bench]
 fn init_jitter(b: &mut Bencher) {
     b.iter(|| {
-        black_box(JitterRng::new().unwrap());
+        JitterRng::new().unwrap()
+    });
+}
+
+
+const RESEEDING_THRESHOLD: u64 = 1024*1024*1024; // something high enough to get
+                                                 // deterministic measurements
+
+#[bench]
+fn reseeding_hc128_bytes(b: &mut Bencher) {
+    let mut rng = ReseedingRng::new(Hc128Core::from_entropy(),
+                                    RESEEDING_THRESHOLD,
+                                    EntropyRng::new());
+    let mut buf = [0u8; BYTES_LEN];
+    b.iter(|| {
+        for _ in 0..RAND_BENCH_N {
+            rng.fill_bytes(&mut buf);
+            black_box(buf);
+        }
     });
+    b.bytes = BYTES_LEN as u64 * RAND_BENCH_N;
+}
+
+macro_rules! reseeding_uint {
+    ($fnn:ident, $ty:ty) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = ReseedingRng::new(Hc128Core::from_entropy(),
+                                            RESEEDING_THRESHOLD,
+                                            EntropyRng::new());
+            b.iter(|| {
+                let mut accum: $ty = 0;
+                for _ in 0..RAND_BENCH_N {
+                    accum = accum.wrapping_add(rng.gen::<$ty>());
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * RAND_BENCH_N;
+        }
+    }
+}
+
+reseeding_uint!(reseeding_hc128_u32, u32);
+reseeding_uint!(reseeding_hc128_u64, u64);
+
+
+macro_rules! threadrng_uint {
+    ($fnn:ident, $ty:ty) => {
+        #[bench]
+        fn $fnn(b: &mut Bencher) {
+            let mut rng = thread_rng();
+            b.iter(|| {
+                let mut accum: $ty = 0;
+                for _ in 0..RAND_BENCH_N {
+                    accum = accum.wrapping_add(rng.gen::<$ty>());
+                }
+                accum
+            });
+            b.bytes = size_of::<$ty>() as u64 * RAND_BENCH_N;
+        }
+    }
 }
+
+threadrng_uint!(thread_rng_u32, u32);
+threadrng_uint!(thread_rng_u64, u64);
diff --git a/rand/benches/misc.rs b/rand/benches/misc.rs
index 4251761..8fb3a83 100644
--- a/rand/benches/misc.rs
+++ b/rand/benches/misc.rs
@@ -1,62 +1,160 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
 #![feature(test)]
 
 extern crate test;
 extern crate rand;
 
-use test::{black_box, Bencher};
+const RAND_BENCH_N: u64 = 1000;
+
+use test::Bencher;
 
-use rand::{Rng, weak_rng};
-use rand::seq::*;
+use rand::prelude::*;
 
 #[bench]
-fn misc_shuffle_100(b: &mut Bencher) {
-    let mut rng = weak_rng();
-    let x : &mut [usize] = &mut [1; 100];
+fn misc_gen_bool_const(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
     b.iter(|| {
-        rng.shuffle(x);
-        black_box(&x);
+        let mut accum = true;
+        for _ in 0..::RAND_BENCH_N {
+            accum ^= rng.gen_bool(0.18);
+        }
+        accum
     })
 }
 
 #[bench]
-fn misc_sample_iter_10_of_100(b: &mut Bencher) {
-    let mut rng = weak_rng();
-    let x : &[usize] = &[1; 100];
+fn misc_gen_bool_var(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
     b.iter(|| {
-        black_box(sample_iter(&mut rng, x, 10).unwrap_or_else(|e| e));
+        let mut accum = true;
+        let mut p = 0.18;
+        for _ in 0..::RAND_BENCH_N {
+            accum ^= rng.gen_bool(p);
+            p += 0.0001;
+        }
+        accum
     })
 }
 
 #[bench]
-fn misc_sample_slice_10_of_100(b: &mut Bencher) {
-    let mut rng = weak_rng();
-    let x : &[usize] = &[1; 100];
+fn misc_gen_ratio_const(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
     b.iter(|| {
-        black_box(sample_slice(&mut rng, x, 10));
+        let mut accum = true;
+        for _ in 0..::RAND_BENCH_N {
+            accum ^= rng.gen_ratio(2, 3);
+        }
+        accum
+    })
+}
+
+#[bench]
+fn misc_gen_ratio_var(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
+    b.iter(|| {
+        let mut accum = true;
+        for i in 2..(::RAND_BENCH_N as u32 + 2) {
+            accum ^= rng.gen_ratio(i, i + 1);
+        }
+        accum
+    })
+}
+
+#[bench]
+fn misc_bernoulli_const(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
+    b.iter(|| {
+        let d = rand::distributions::Bernoulli::new(0.18);
+        let mut accum = true;
+        for _ in 0..::RAND_BENCH_N {
+            accum ^= rng.sample(d);
+        }
+        accum
     })
 }
 
 #[bench]
-fn misc_sample_slice_ref_10_of_100(b: &mut Bencher) {
-    let mut rng = weak_rng();
-    let x : &[usize] = &[1; 100];
+fn misc_bernoulli_var(b: &mut Bencher) {
+    let mut rng = StdRng::from_rng(&mut thread_rng()).unwrap();
     b.iter(|| {
-        black_box(sample_slice_ref(&mut rng, x, 10));
+        let mut accum = true;
+        let mut p = 0.18;
+        for _ in 0..::RAND_BENCH_N {
+            let d = rand::distributions::Bernoulli::new(p);
+            accum ^= rng.sample(d);
+            p += 0.0001;
+        }
+        accum
     })
 }
 
-macro_rules! sample_indices {
-    ($name:ident, $amount:expr, $length:expr) => {
+macro_rules! sample_binomial {
+    ($name:ident, $n:expr, $p:expr) => {
         #[bench]
         fn $name(b: &mut Bencher) {
-            let mut rng = weak_rng();
+            let mut rng = SmallRng::from_rng(&mut thread_rng()).unwrap();
+            let (n, p) = ($n, $p);
             b.iter(|| {
-                black_box(sample_indices(&mut rng, $length, $amount));
+                let d = rand::distributions::Binomial::new(n, p);
+                rng.sample(d)
             })
         }
     }
 }
 
-sample_indices!(misc_sample_indices_10_of_1k, 10, 1000);
-sample_indices!(misc_sample_indices_50_of_1k, 50, 1000);
-sample_indices!(misc_sample_indices_100_of_1k, 100, 1000);
+sample_binomial!(misc_binomial_1, 1, 0.9);
+sample_binomial!(misc_binomial_10, 10, 0.9);
+sample_binomial!(misc_binomial_100, 100, 0.99);
+sample_binomial!(misc_binomial_1000, 1000, 0.01);
+sample_binomial!(misc_binomial_1e12, 1000_000_000_000, 0.2);
+
+#[bench]
+fn gen_1k_iter_repeat(b: &mut Bencher) {
+    use std::iter;
+    let mut rng = SmallRng::from_rng(&mut thread_rng()).unwrap();
+    b.iter(|| {
+        let v: Vec<u64> = iter::repeat(()).map(|()| rng.gen()).take(128).collect();
+        v
+    });
+    b.bytes = 1024;
+}
+
+#[bench]
+fn gen_1k_sample_iter(b: &mut Bencher) {
+    use rand::distributions::{Distribution, Standard};
+    let mut rng = SmallRng::from_rng(&mut thread_rng()).unwrap();
+    b.iter(|| {
+        let v: Vec<u64> = Standard.sample_iter(&mut rng).take(128).collect();
+        v
+    });
+    b.bytes = 1024;
+}
+
+#[bench]
+fn gen_1k_gen_array(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(&mut thread_rng()).unwrap();
+    b.iter(|| {
+        // max supported array length is 32!
+        let v: [[u64; 32]; 4] = rng.gen();
+        v
+    });
+    b.bytes = 1024;
+}
+
+#[bench]
+fn gen_1k_fill(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(&mut thread_rng()).unwrap();
+    let mut buf = [0u64; 128];
+    b.iter(|| {
+        rng.fill(&mut buf[..]);
+        buf
+    });
+    b.bytes = 1024;
+}
diff --git a/rand/benches/seq.rs b/rand/benches/seq.rs
new file mode 100644
index 0000000..0ca3398
--- /dev/null
+++ b/rand/benches/seq.rs
@@ -0,0 +1,174 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(test)]
+#![allow(non_snake_case)]
+
+extern crate test;
+extern crate rand;
+
+use test::Bencher;
+
+use rand::prelude::*;
+use rand::seq::*;
+use std::mem::size_of;
+
+const RAND_BENCH_N: u64 = 1000;
+
+#[bench]
+fn seq_shuffle_100(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &mut [usize] = &mut [1; 100];
+    b.iter(|| {
+        x.shuffle(&mut rng);
+        x[0]
+    })
+}
+
+#[bench]
+fn seq_slice_choose_1_of_1000(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &mut [usize] = &mut [1; 1000];
+    for i in 0..1000 {
+        x[i] = i;
+    }
+    b.iter(|| {
+        let mut s = 0;
+        for _ in 0..RAND_BENCH_N {
+            s += x.choose(&mut rng).unwrap();
+        }
+        s
+    });
+    b.bytes = size_of::<usize>() as u64 * ::RAND_BENCH_N;
+}
+
+macro_rules! seq_slice_choose_multiple {
+    ($name:ident, $amount:expr, $length:expr) => {
+        #[bench]
+        fn $name(b: &mut Bencher) {
+            let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+            let x : &[i32] = &[$amount; $length];
+            let mut result = [0i32; $amount];
+            b.iter(|| {
+                // Collect full result to prevent unwanted shortcuts getting
+                // first element (in case sample_indices returns an iterator).
+                for (slot, sample) in result.iter_mut().zip(
+                    x.choose_multiple(&mut rng, $amount)) {
+                    *slot = *sample;
+                }
+                result[$amount-1]
+            })
+        }
+    }
+}
+
+seq_slice_choose_multiple!(seq_slice_choose_multiple_1_of_1000, 1, 1000);
+seq_slice_choose_multiple!(seq_slice_choose_multiple_950_of_1000, 950, 1000);
+seq_slice_choose_multiple!(seq_slice_choose_multiple_10_of_100, 10, 100);
+seq_slice_choose_multiple!(seq_slice_choose_multiple_90_of_100, 90, 100);
+
+#[bench]
+fn seq_iter_choose_from_1000(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &mut [usize] = &mut [1; 1000];
+    for i in 0..1000 {
+        x[i] = i;
+    }
+    b.iter(|| {
+        let mut s = 0;
+        for _ in 0..RAND_BENCH_N {
+            s += x.iter().choose(&mut rng).unwrap();
+        }
+        s
+    });
+    b.bytes = size_of::<usize>() as u64 * ::RAND_BENCH_N;
+}
+
+#[derive(Clone)]
+struct UnhintedIterator<I: Iterator + Clone> {
+    iter: I,
+}
+impl<I: Iterator + Clone> Iterator for UnhintedIterator<I> {
+    type Item = I::Item;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+}
+
+#[derive(Clone)]
+struct WindowHintedIterator<I: ExactSizeIterator + Iterator + Clone> {
+    iter: I,
+    window_size: usize,
+}
+impl<I: ExactSizeIterator + Iterator + Clone> Iterator for WindowHintedIterator<I> {
+    type Item = I::Item;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (std::cmp::min(self.iter.len(), self.window_size), None)
+    }
+}
+
+#[bench]
+fn seq_iter_unhinted_choose_from_1000(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &[usize] = &[1; 1000];
+    b.iter(|| {
+        UnhintedIterator { iter: x.iter() }.choose(&mut rng).unwrap()
+    })
+}
+
+#[bench]
+fn seq_iter_window_hinted_choose_from_1000(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &[usize] = &[1; 1000];
+    b.iter(|| {
+        WindowHintedIterator { iter: x.iter(), window_size: 7 }.choose(&mut rng)
+    })
+}
+
+#[bench]
+fn seq_iter_choose_multiple_10_of_100(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &[usize] = &[1; 100];
+    b.iter(|| {
+        x.iter().cloned().choose_multiple(&mut rng, 10)
+    })
+}
+
+#[bench]
+fn seq_iter_choose_multiple_fill_10_of_100(b: &mut Bencher) {
+    let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+    let x : &[usize] = &[1; 100];
+    let mut buf = [0; 10];
+    b.iter(|| {
+        x.iter().cloned().choose_multiple_fill(&mut rng, &mut buf)
+    })
+}
+
+macro_rules! sample_indices {
+    ($name:ident, $fn:ident, $amount:expr, $length:expr) => {
+        #[bench]
+        fn $name(b: &mut Bencher) {
+            let mut rng = SmallRng::from_rng(thread_rng()).unwrap();
+            b.iter(|| {
+                index::$fn(&mut rng, $length, $amount)
+            })
+        }
+    }
+}
+
+sample_indices!(misc_sample_indices_1_of_1k, sample, 1, 1000);
+sample_indices!(misc_sample_indices_10_of_1k, sample, 10, 1000);
+sample_indices!(misc_sample_indices_100_of_1k, sample, 100, 1000);
+sample_indices!(misc_sample_indices_100_of_1M, sample, 100, 1000_000);
+sample_indices!(misc_sample_indices_100_of_1G, sample, 100, 1000_000_000);
+sample_indices!(misc_sample_indices_200_of_1G, sample, 200, 1000_000_000);
+sample_indices!(misc_sample_indices_400_of_1G, sample, 400, 1000_000_000);
+sample_indices!(misc_sample_indices_600_of_1G, sample, 600, 1000_000_000);
diff --git a/rand/build.rs b/rand/build.rs
new file mode 100644
index 0000000..e44b643
--- /dev/null
+++ b/rand/build.rs
@@ -0,0 +1,14 @@
+extern crate rustc_version;
+use rustc_version::{version, Version};
+
+fn main() {
+    if version().unwrap() >= Version::parse("1.25.0").unwrap() {
+        println!("cargo:rustc-cfg=rust_1_25");
+    }
+    if version().unwrap() >= Version::parse("1.26.0").unwrap() {
+        println!("cargo:rustc-cfg=rust_1_26");
+    }
+    if version().unwrap() >= Version::parse("1.27.0").unwrap() {
+        println!("cargo:rustc-cfg=rust_1_27");
+    }
+}
diff --git a/rand/examples/monte-carlo.rs b/rand/examples/monte-carlo.rs
new file mode 100644
index 0000000..9162996
--- /dev/null
+++ b/rand/examples/monte-carlo.rs
@@ -0,0 +1,51 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! # Monte Carlo estimation of π
+//!
+//! Imagine that we have a square with sides of length 2 and a unit circle
+//! (radius = 1), both centered at the origin. The areas are:
+//! 
+//! ```text
+//!     area of circle  = πr² = π * r * r = π
+//!     area of square  = 2² = 4
+//! ```
+//!
+//! The circle is entirely within the square, so if we sample many points
+//! randomly from the square, roughly π / 4 of them should be inside the circle.
+//!
+//! We can use the above fact to estimate the value of π: pick many points in
+//! the square at random, calculate the fraction that fall within the circle,
+//! and multiply this fraction by 4.
+
+#![cfg(feature="std")]
+
+
+extern crate rand;
+
+use rand::distributions::{Distribution, Uniform};
+
+fn main() {
+   let range = Uniform::new(-1.0f64, 1.0);
+   let mut rng = rand::thread_rng();
+
+   let total = 1_000_000;
+   let mut in_circle = 0;
+
+   for _ in 0..total {
+       let a = range.sample(&mut rng);
+       let b = range.sample(&mut rng);
+       if a*a + b*b <= 1.0 {
+           in_circle += 1;
+       }
+   }
+
+   // prints something close to 3.14159...
+   println!("π is approximately {}", 4. * (in_circle as f64) / (total as f64));
+}
diff --git a/rand/examples/monty-hall.rs b/rand/examples/monty-hall.rs
new file mode 100644
index 0000000..0932c5e
--- /dev/null
+++ b/rand/examples/monty-hall.rs
@@ -0,0 +1,116 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! ## Monty Hall Problem
+//!
+//! This is a simulation of the [Monty Hall Problem][]:
+//!
+//! > Suppose you're on a game show, and you're given the choice of three doors:
+//! > Behind one door is a car; behind the others, goats. You pick a door, say
+//! > No. 1, and the host, who knows what's behind the doors, opens another
+//! > door, say No. 3, which has a goat. He then says to you, "Do you want to
+//! > pick door No. 2?" Is it to your advantage to switch your choice?
+//!
+//! The rather unintuitive answer is that you will have a 2/3 chance of winning
+//! if you switch and a 1/3 chance of winning if you don't, so it's better to
+//! switch.
+//!
+//! This program will simulate the game show and with large enough simulation
+//! steps it will indeed confirm that it is better to switch.
+//!
+//! [Monty Hall Problem]: https://en.wikipedia.org/wiki/Monty_Hall_problem
+
+#![cfg(feature="std")]
+
+
+extern crate rand;
+
+use rand::Rng;
+use rand::distributions::{Distribution, Uniform};
+
+struct SimulationResult {
+    win: bool,
+    switch: bool,
+}
+
+// Run a single simulation of the Monty Hall problem.
+fn simulate<R: Rng>(random_door: &Uniform<u32>, rng: &mut R)
+                    -> SimulationResult {
+    let car = random_door.sample(rng);
+
+    // This is our initial choice
+    let mut choice = random_door.sample(rng);
+
+    // The game host opens a door
+    let open = game_host_open(car, choice, rng);
+
+    // Shall we switch?
+    let switch = rng.gen();
+    if switch {
+        choice = switch_door(choice, open);
+    }
+
+    SimulationResult { win: choice == car, switch }
+}
+
+// Returns the door the game host opens given our choice and knowledge of
+// where the car is. The game host will never open the door with the car.
+fn game_host_open<R: Rng>(car: u32, choice: u32, rng: &mut R) -> u32 {
+    use rand::seq::SliceRandom;
+    *free_doors(&[car, choice]).choose(rng).unwrap()
+}
+
+// Returns the door we switch to, given our current choice and
+// the open door. There will only be one valid door.
+fn switch_door(choice: u32, open: u32) -> u32 {
+    free_doors(&[choice, open])[0]
+}
+
+fn free_doors(blocked: &[u32]) -> Vec<u32> {
+    (0..3).filter(|x| !blocked.contains(x)).collect()
+}
+
+fn main() {
+    // The estimation will be more accurate with more simulations
+    let num_simulations = 10000;
+
+    let mut rng = rand::thread_rng();
+    let random_door = Uniform::new(0u32, 3);
+
+    let (mut switch_wins, mut switch_losses) = (0, 0);
+    let (mut keep_wins, mut keep_losses) = (0, 0);
+
+    println!("Running {} simulations...", num_simulations);
+    for _ in 0..num_simulations {
+        let result = simulate(&random_door, &mut rng);
+
+        match (result.win, result.switch) {
+            (true, true) => switch_wins += 1,
+            (true, false) => keep_wins += 1,
+            (false, true) => switch_losses += 1,
+            (false, false) => keep_losses += 1,
+        }
+    }
+
+    let total_switches = switch_wins + switch_losses;
+    let total_keeps = keep_wins + keep_losses;
+
+    println!("Switched door {} times with {} wins and {} losses",
+             total_switches, switch_wins, switch_losses);
+
+    println!("Kept our choice {} times with {} wins and {} losses",
+             total_keeps, keep_wins, keep_losses);
+
+    // With a large number of simulations, the values should converge to
+    // 0.667 and 0.333 respectively.
+    println!("Estimated chance to win if we switch: {}",
+             switch_wins as f32 / total_switches as f32);
+    println!("Estimated chance to win if we don't: {}",
+             keep_wins as f32 / total_keeps as f32);
+}
diff --git a/rand/rand-derive/Cargo.toml b/rand/rand-derive/Cargo.toml
deleted file mode 100644
index 1a2dbe1..0000000
--- a/rand/rand-derive/Cargo.toml
+++ /dev/null
@@ -1,23 +0,0 @@
-[package]
-
-name = "rand_derive"
-version = "0.3.1"
-authors = ["The Rust Project Developers"]
-license = "MIT/Apache-2.0"
-readme = "README.md"
-repository = "https://github.com/rust-lang-nursery/rand"
-documentation = "https://docs.rs/rand_derive"
-homepage = "https://github.com/rust-lang-nursery/rand"
-description = """
-`#[derive(Rand)]` functionality for the `rand::Rand` trait.
-"""
-
-[lib]
-proc-macro = true
-
-[dependencies]
-quote = "0.3"
-syn = "0.11"
-
-[dev-dependencies]
-rand = { path = "..", version = "0.4" }
diff --git a/rand/rand-derive/README.md b/rand/rand-derive/README.md
deleted file mode 100644
index 3d1fedb..0000000
--- a/rand/rand-derive/README.md
+++ /dev/null
@@ -1,51 +0,0 @@
-
-rand_macros
-====
-
-`#[derive(Rand)]` functionality for the `rand::Rand` trait.
-
-## Usage
-Add this to your `Cargo.toml`:
-
-```toml
-[dependencies]
-rand = "0.4"
-rand_macros = "0.2"
-```
-
-and this to your crate root:
-
-```rust
-extern crate rand;
-#[macro_use]
-extern crate rand_macros;
-```
-
-## Examples
-
-`#[derive(Rand)]` can be used on any `struct` or `enum` where all fields/variants implement `rand::Rand`.
-
-```rust
-#[derive(Debug, Rand)]
-struct Foo {
-    x: u16,
-    y: Option<f64>,
-}
-
-#[derive(Debug, Rand)]
-enum Bar {
-     X{x: u8, y: isize},
-     Y([bool; 4]),
-     Z,
-}
-```
-Now you can call the `Rng::gen()` function on your custom types.
-
-```rust
-use rand::Rng;
-
-let mut rng = rand::thread_rng();
-
-println!("{:?}", rng.gen::<Foo>());
-println!("{:?}", rng.gen::<Bar>());
-```
diff --git a/rand/rand-derive/src/lib.rs b/rand/rand-derive/src/lib.rs
deleted file mode 100644
index 80c803a..0000000
--- a/rand/rand-derive/src/lib.rs
+++ /dev/null
@@ -1,116 +0,0 @@
-//! Support for `#[derive(Rand)]`
-//!
-//! # Examples
-//!
-//! ```
-//! extern crate rand;
-//! #[macro_use]
-//! extern crate rand_derive;
-//!
-//! #[derive(Rand, Debug)]
-//! struct MyStruct {
-//!     a: i32,
-//!     b: u32,
-//! }
-//!
-//! fn main() {
-//!     println!("{:?}", rand::random::<MyStruct>());
-//! }
-//! ```
-
-extern crate proc_macro;
-#[macro_use]
-extern crate quote;
-extern crate syn;
-
-use proc_macro::TokenStream;
-
-#[proc_macro_derive(Rand)]
-pub fn rand_derive(input: TokenStream) -> TokenStream {
-    let s = input.to_string();
-    let ast = syn::parse_derive_input(&s).unwrap();
-    let gen = impl_rand_derive(&ast);
-    gen.parse().unwrap()
-}
-
-fn impl_rand_derive(ast: &syn::MacroInput) -> quote::Tokens {
-    let name = &ast.ident;
-    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
-
-    let rand = match ast.body {
-        syn::Body::Struct(syn::VariantData::Struct(ref body)) => {
-            let fields = body
-                .iter()
-                .filter_map(|field| field.ident.as_ref())
-                .map(|ident| quote! { #ident: __rng.gen() })
-                .collect::<Vec<_>>();
-
-            quote! { #name { #(#fields,)* } }
-        },
-        syn::Body::Struct(syn::VariantData::Tuple(ref body)) => {
-            let fields = (0..body.len())
-                .map(|_| quote! { __rng.gen() })
-                .collect::<Vec<_>>();
-
-            quote! { #name (#(#fields),*) }
-        },
-        syn::Body::Struct(syn::VariantData::Unit) => {
-            quote! { #name }
-        },
-        syn::Body::Enum(ref body) => {
-            if body.is_empty() {
-                panic!("`Rand` cannot be derived for enums with no variants");
-            }
-
-            let len = body.len();
-            let mut arms = body
-                .iter()
-                .map(|variant| {
-                    let ident = &variant.ident;
-                    match variant.data {
-                        syn::VariantData::Struct(ref body) => {
-                            let fields = body
-                                .iter()
-                                .filter_map(|field| field.ident.as_ref())
-                                .map(|ident| quote! { #ident: __rng.gen() })
-                                .collect::<Vec<_>>();
-                            quote! { #name::#ident { #(#fields,)* } }
-                        },
-                        syn::VariantData::Tuple(ref body) => {
-                            let fields = (0..body.len())
-                                .map(|_| quote! { __rng.gen() })
-                                .collect::<Vec<_>>();
-
-                            quote! { #name::#ident (#(#fields),*) }
-                        },
-                        syn::VariantData::Unit => quote! { #name::#ident }
-                    }
-                });
-
-            match len {
-                1 => quote! { #(#arms)* },
-                2 => {
-                    let (a, b) = (arms.next(), arms.next());
-                    quote! { if __rng.gen() { #a } else { #b } }
-                },
-                _ => {
-                    let mut variants = arms
-                        .enumerate()
-                        .map(|(index, arm)| quote! { #index => #arm })
-                        .collect::<Vec<_>>();
-                    variants.push(quote! { _ => unreachable!() });
-                    quote! { match __rng.gen_range(0, #len) { #(#variants,)* } }
-                },
-            }
-        }
-    };
-
-    quote! {
-        impl #impl_generics ::rand::Rand for #name #ty_generics #where_clause {
-            #[inline]
-            fn rand<__R: ::rand::Rng>(__rng: &mut __R) -> Self {
-                #rand
-            }
-        }
-    }
-}
diff --git a/rand/rand-derive/tests/rand_macros.rs b/rand/rand-derive/tests/rand_macros.rs
deleted file mode 100644
index 938f2b0..0000000
--- a/rand/rand-derive/tests/rand_macros.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-#![allow(dead_code)]
-
-extern crate rand;
-#[macro_use]
-extern crate rand_derive;
-
-use rand::Rng;
-
-#[derive(Rand)]
-struct Struct {
-    x: u16,
-    y: Option<f64>,
-}
-
-#[derive(Rand)]
-struct Tuple(i16, Option<f64>);
-
-#[derive(Rand)]
-struct Unit;
-
-#[derive(Rand)]
-enum EnumUnit {
-    X,
-}
-
-#[derive(Rand)]
-enum Enum1 {
-    X(u8, f32),
-}
-
-#[derive(Rand)]
-enum Enum2 {
-    X(bool),
-    Y,
-}
-
-#[derive(Rand)]
-enum Enum3 {
-    X { x: u8, y: isize },
-    Y([bool; 4]),
-    Z,
-}
-
-#[test]
-fn smoke() {
-    let mut rng = rand::XorShiftRng::new_unseeded();
-
-    // check nothing horrible happens internally:
-    for _ in 0..100 {
-        let _ = rng.gen::<Struct>();
-        let _ = rng.gen::<Tuple>();
-        let _ = rng.gen::<Unit>();
-        let _ = rng.gen::<EnumUnit>();
-        let _ = rng.gen::<Enum1>();
-        let _ = rng.gen::<Enum2>();
-        let _ = rng.gen::<Enum3>();
-    }
-}
diff --git a/rand/rand_chacha/CHANGELOG.md b/rand/rand_chacha/CHANGELOG.md
new file mode 100644
index 0000000..d0c4a2f
--- /dev/null
+++ b/rand/rand_chacha/CHANGELOG.md
@@ -0,0 +1,8 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2018-10-17
+- Pulled out of the Rand crate
diff --git a/rand/rand_chacha/COPYRIGHT b/rand/rand_chacha/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_chacha/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_chacha/Cargo.toml b/rand/rand_chacha/Cargo.toml
new file mode 100644
index 0000000..af70969
--- /dev/null
+++ b/rand/rand_chacha/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+name = "rand_chacha"
+version = "0.1.0"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_chacha"
+homepage = "https://crates.io/crates/rand_chacha"
+description = """
+ChaCha random number generator
+"""
+keywords = ["random", "rng", "chacha"]
+categories = ["algorithms", "no-std"]
+build = "build.rs"
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[dependencies]
+rand_core = { path = "../rand_core", version = ">=0.2, <0.4", default-features=false }
+
+[build-dependencies]
+rustc_version = "0.2"
diff --git a/rand/rand_chacha/LICENSE-APACHE b/rand/rand_chacha/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_chacha/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     https://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
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+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
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+
+   "Work" shall mean the work of authorship, whether in Source or
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+   copyright notice that is included in or attached to the work
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+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
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+   of this License, Derivative Works shall not include works that remain
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+   "Contribution" shall mean any work of authorship, including
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diff --git a/rand/rand_chacha/LICENSE-MIT b/rand/rand_chacha/LICENSE-MIT
new file mode 100644
index 0000000..d93b5ba
--- /dev/null
+++ b/rand/rand_chacha/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright 2018 Developers of the Rand project
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_chacha/README.md b/rand/rand_chacha/README.md
new file mode 100644
index 0000000..5a1dbac
--- /dev/null
+++ b/rand/rand_chacha/README.md
@@ -0,0 +1,45 @@
+# rand_chacha
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_chacha.svg)](https://crates.io/crates/rand_chacha)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_chacha)
+[![API](https://docs.rs/rand_chacha/badge.svg)](https://docs.rs/rand_chacha)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+A cryptographically secure random number generator that uses the ChaCha
+algorithm.
+
+ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use
+as an RNG. It is an improved variant of the Salsa20 cipher family, which was
+selected as one of the "stream ciphers suitable for widespread adoption" by
+eSTREAM[^2].
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_chacha)
+-   [API documentation (docs.rs)](https://docs.rs/rand_chacha)
+-   [Changelog](CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+[^1]: D. J. Bernstein, [*ChaCha, a variant of Salsa20*](
+      https://cr.yp.to/chacha.html)
+
+[^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+      http://www.ecrypt.eu.org/stream/)
+
+
+## Crate Features
+
+`rand_chacha` is `no_std` compatible. It does not require any functionality
+outside of the `core` lib, thus there are no features to configure.
+
+
+# License
+
+`rand_chacha` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_chacha/build.rs b/rand/rand_chacha/build.rs
new file mode 100644
index 0000000..cb3ae20
--- /dev/null
+++ b/rand/rand_chacha/build.rs
@@ -0,0 +1,8 @@
+extern crate rustc_version;
+use rustc_version::{version, Version};
+
+fn main() {
+    if version().unwrap() >= Version::parse("1.26.0").unwrap() {
+        println!("cargo:rustc-cfg=rust_1_26");
+    }
+}
diff --git a/rand/rand_chacha/src/chacha.rs b/rand/rand_chacha/src/chacha.rs
new file mode 100644
index 0000000..3e90409
--- /dev/null
+++ b/rand/rand_chacha/src/chacha.rs
@@ -0,0 +1,449 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2014 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The ChaCha random number generator.
+
+use core::fmt;
+use rand_core::{CryptoRng, RngCore, SeedableRng, Error, le};
+use rand_core::block::{BlockRngCore, BlockRng};
+
+const SEED_WORDS: usize = 8; // 8 words for the 256-bit key
+const STATE_WORDS: usize = 16;
+
+/// A cryptographically secure random number generator that uses the ChaCha
+/// algorithm.
+///
+/// ChaCha is a stream cipher designed by Daniel J. Bernstein[^1], that we use
+/// as an RNG. It is an improved variant of the Salsa20 cipher family, which was
+/// selected as one of the "stream ciphers suitable for widespread adoption" by
+/// eSTREAM[^2].
+///
+/// ChaCha uses add-rotate-xor (ARX) operations as its basis. These are safe
+/// against timing attacks, although that is mostly a concern for ciphers and
+/// not for RNGs. Also it is very suitable for SIMD implementation.
+/// Here we do not provide a SIMD implementation yet, except for what is
+/// provided by auto-vectorisation.
+///
+/// With the ChaCha algorithm it is possible to choose the number of rounds the
+/// core algorithm should run. The number of rounds is a tradeoff between
+/// performance and security, where 8 rounds is the minimum potentially
+/// secure configuration, and 20 rounds is widely used as a conservative choice.
+/// We use 20 rounds in this implementation, but hope to allow type-level
+/// configuration in the future.
+///
+/// We use a 64-bit counter and 64-bit stream identifier as in Bernstein's
+/// implementation[^1] except that we use a stream identifier in place of a
+/// nonce. A 64-bit counter over 64-byte (16 word) blocks allows 1 ZiB of output
+/// before cycling, and the stream identifier allows 2<sup>64</sup> unique
+/// streams of output per seed. Both counter and stream are initialized to zero
+/// but may be set via [`set_word_pos`] and [`set_stream`].
+///
+/// The word layout is:
+///
+/// ```text
+/// constant  constant  constant  constant
+/// seed      seed      seed      seed
+/// seed      seed      seed      seed
+/// counter   counter   stream_id stream_id
+/// ```
+///
+/// This implementation uses an output buffer of sixteen `u32` words, and uses
+/// [`BlockRng`] to implement the [`RngCore`] methods.
+///
+/// [^1]: D. J. Bernstein, [*ChaCha, a variant of Salsa20*](
+///       https://cr.yp.to/chacha.html)
+///
+/// [^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+///       http://www.ecrypt.eu.org/stream/)
+///
+/// [`set_word_pos`]: #method.set_word_pos
+/// [`set_stream`]: #method.set_stream
+/// [`BlockRng`]: ../rand_core/block/struct.BlockRng.html
+/// [`RngCore`]: ../rand_core/trait.RngCore.html
+#[derive(Clone, Debug)]
+pub struct ChaChaRng(BlockRng<ChaChaCore>);
+
+impl RngCore for ChaChaRng {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    #[inline]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for ChaChaRng {
+    type Seed = <ChaChaCore as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        ChaChaRng(BlockRng::<ChaChaCore>::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        BlockRng::<ChaChaCore>::from_rng(rng).map(ChaChaRng)
+    }
+}
+
+impl CryptoRng for ChaChaRng {}
+
+impl ChaChaRng {
+    /// Get the offset from the start of the stream, in 32-bit words.
+    ///
+    /// Since the generated blocks are 16 words (2<sup>4</sup>) long and the
+    /// counter is 64-bits, the offset is a 68-bit number. Sub-word offsets are
+    /// not supported, hence the result can simply be multiplied by 4 to get a
+    /// byte-offset.
+    ///
+    /// Note: this function is currently only available with Rust 1.26 or later.
+    #[cfg(rust_1_26)]
+    pub fn get_word_pos(&self) -> u128 {
+        let mut c = (self.0.core.state[13] as u64) << 32
+                  | (self.0.core.state[12] as u64);
+        let mut index = self.0.index();
+        // c is the end of the last block generated, unless index is at end
+        if index >= STATE_WORDS {
+            index = 0;
+        } else {
+            c = c.wrapping_sub(1);
+        }
+        ((c as u128) << 4) | (index as u128)
+    }
+
+    /// Set the offset from the start of the stream, in 32-bit words.
+    ///
+    /// As with `get_word_pos`, we use a 68-bit number. Since the generator
+    /// simply cycles at the end of its period (1 ZiB), we ignore the upper
+    /// 60 bits.
+    ///
+    /// Note: this function is currently only available with Rust 1.26 or later.
+    #[cfg(rust_1_26)]
+    pub fn set_word_pos(&mut self, word_offset: u128) {
+        let index = (word_offset as usize) & 0xF;
+        let counter = (word_offset >> 4) as u64;
+        self.0.core.state[12] = counter as u32;
+        self.0.core.state[13] = (counter >> 32) as u32;
+        if index != 0 {
+            self.0.generate_and_set(index); // also increments counter
+        } else {
+            self.0.reset();
+        }
+    }
+
+    /// Set the stream number.
+    ///
+    /// This is initialized to zero; 2<sup>64</sup> unique streams of output
+    /// are available per seed/key.
+    ///
+    /// Note that in order to reproduce ChaCha output with a specific 64-bit
+    /// nonce, one can convert that nonce to a `u64` in little-endian fashion
+    /// and pass to this function. In theory a 96-bit nonce can be used by
+    /// passing the last 64-bits to this function and using the first 32-bits as
+    /// the most significant half of the 64-bit counter (which may be set
+    /// indirectly via `set_word_pos`), but this is not directly supported.
+    pub fn set_stream(&mut self, stream: u64) {
+        let index = self.0.index();
+        self.0.core.state[14] = stream as u32;
+        self.0.core.state[15] = (stream >> 32) as u32;
+        if index < STATE_WORDS {
+            // we need to regenerate a partial result buffer
+            {
+                // reverse of counter adjustment in generate()
+                if self.0.core.state[12] == 0 {
+                    self.0.core.state[13] = self.0.core.state[13].wrapping_sub(1);
+                }
+                self.0.core.state[12] = self.0.core.state[12].wrapping_sub(1);
+            }
+            self.0.generate_and_set(index);
+        }
+    }
+}
+
+/// The core of `ChaChaRng`, used with `BlockRng`.
+#[derive(Clone)]
+pub struct ChaChaCore {
+    state: [u32; STATE_WORDS],
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for ChaChaCore {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "ChaChaCore {{}}")
+    }
+}
+
+macro_rules! quarter_round{
+    ($a: expr, $b: expr, $c: expr, $d: expr) => {{
+        $a = $a.wrapping_add($b); $d ^= $a; $d = $d.rotate_left(16);
+        $c = $c.wrapping_add($d); $b ^= $c; $b = $b.rotate_left(12);
+        $a = $a.wrapping_add($b); $d ^= $a; $d = $d.rotate_left( 8);
+        $c = $c.wrapping_add($d); $b ^= $c; $b = $b.rotate_left( 7);
+    }}
+}
+
+macro_rules! double_round{
+    ($x: expr) => {{
+        // Column round
+        quarter_round!($x[ 0], $x[ 4], $x[ 8], $x[12]);
+        quarter_round!($x[ 1], $x[ 5], $x[ 9], $x[13]);
+        quarter_round!($x[ 2], $x[ 6], $x[10], $x[14]);
+        quarter_round!($x[ 3], $x[ 7], $x[11], $x[15]);
+        // Diagonal round
+        quarter_round!($x[ 0], $x[ 5], $x[10], $x[15]);
+        quarter_round!($x[ 1], $x[ 6], $x[11], $x[12]);
+        quarter_round!($x[ 2], $x[ 7], $x[ 8], $x[13]);
+        quarter_round!($x[ 3], $x[ 4], $x[ 9], $x[14]);
+    }}
+}
+
+impl BlockRngCore for ChaChaCore {
+    type Item = u32;
+    type Results = [u32; STATE_WORDS];
+
+    fn generate(&mut self, results: &mut Self::Results) {
+        // For some reason extracting this part into a separate function
+        // improves performance by 50%.
+        fn core(results: &mut [u32; STATE_WORDS],
+                state: &[u32; STATE_WORDS])
+        {
+            let mut tmp = *state;
+            let rounds = 20;
+            for _ in 0..rounds / 2 {
+                double_round!(tmp);
+            }
+            for i in 0..STATE_WORDS {
+                results[i] = tmp[i].wrapping_add(state[i]);
+            }
+        }
+
+        core(results, &self.state);
+
+        // update 64-bit counter
+        self.state[12] = self.state[12].wrapping_add(1);
+        if self.state[12] != 0 { return; };
+        self.state[13] = self.state[13].wrapping_add(1);
+    }
+}
+
+impl SeedableRng for ChaChaCore {
+    type Seed = [u8; SEED_WORDS*4];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_le = [0u32; SEED_WORDS];
+        le::read_u32_into(&seed, &mut seed_le);
+        Self {
+            state: [0x61707865, 0x3320646E, 0x79622D32, 0x6B206574, // constants
+                    seed_le[0], seed_le[1], seed_le[2], seed_le[3], // seed
+                    seed_le[4], seed_le[5], seed_le[6], seed_le[7], // seed
+                    0, 0, 0, 0], // counter
+         }
+    }
+}
+
+impl CryptoRng for ChaChaCore {}
+
+impl From<ChaChaCore> for ChaChaRng {
+    fn from(core: ChaChaCore) -> Self {
+        ChaChaRng(BlockRng::new(core))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use ::rand_core::{RngCore, SeedableRng};
+    use super::ChaChaRng;
+
+    #[test]
+    fn test_chacha_construction() {
+        let seed = [0,0,0,0,0,0,0,0,
+            1,0,0,0,0,0,0,0,
+            2,0,0,0,0,0,0,0,
+            3,0,0,0,0,0,0,0];
+        let mut rng1 = ChaChaRng::from_seed(seed);
+        assert_eq!(rng1.next_u32(), 137206642);
+
+        let mut rng2 = ChaChaRng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u32(), 1325750369);
+    }
+
+    #[test]
+    fn test_chacha_true_values_a() {
+        // Test vectors 1 and 2 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653,
+                        0xb819d2bd, 0x1aed8da0, 0xccef36a8, 0xc70d778b,
+                        0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8,
+                        0xf4b8436a, 0x1ca11815, 0x69b687c3, 0x8665eeb2];
+        assert_eq!(results, expected);
+
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73,
+                        0xa0290fcb, 0x6965e348, 0x3e53c612, 0xed7aee32,
+                        0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874,
+                        0x281fed31, 0x45fb0a51, 0x1f0ae1ac, 0x6f4d794b];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_true_values_b() {
+        // Test vector 3 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 1];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        // Skip block 0
+        for _ in 0..16 { rng.next_u32(); }
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0x2452eb3a, 0x9249f8ec, 0x8d829d9b, 0xddd4ceb1,
+                        0xe8252083, 0x60818b01, 0xf38422b8, 0x5aaa49c9,
+                        0xbb00ca8e, 0xda3ba7b4, 0xc4b592d1, 0xfdf2732f,
+                        0x4436274e, 0x2561b3c8, 0xebdd4aa6, 0xa0136c00];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    #[cfg(rust_1_26)]
+    fn test_chacha_true_values_c() {
+        // Test vector 4 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        let seed = [0, 0xff, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0, 0, 0];
+        let expected = [0xfb4dd572, 0x4bc42ef1, 0xdf922636, 0x327f1394,
+                        0xa78dea8f, 0x5e269039, 0xa1bebbc1, 0xcaf09aae,
+                        0xa25ab213, 0x48a6b46c, 0x1b9d9bcb, 0x092c5be6,
+                        0x546ca624, 0x1bec45d5, 0x87f47473, 0x96f0992e];
+        let expected_end = 3 * 16;
+        let mut results = [0u32; 16];
+
+        // Test block 2 by skipping block 0 and 1
+        let mut rng1 = ChaChaRng::from_seed(seed);
+        for _ in 0..32 { rng1.next_u32(); }
+        for i in results.iter_mut() { *i = rng1.next_u32(); }
+        assert_eq!(results, expected);
+        assert_eq!(rng1.get_word_pos(), expected_end);
+
+        // Test block 2 by using `set_word_pos`
+        let mut rng2 = ChaChaRng::from_seed(seed);
+        rng2.set_word_pos(2 * 16);
+        for i in results.iter_mut() { *i = rng2.next_u32(); }
+        assert_eq!(results, expected);
+        assert_eq!(rng2.get_word_pos(), expected_end);
+
+        // Test skipping behaviour with other types
+        let mut buf = [0u8; 32];
+        rng2.fill_bytes(&mut buf[..]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 8);
+        rng2.fill_bytes(&mut buf[0..25]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 15);
+        rng2.next_u64();
+        assert_eq!(rng2.get_word_pos(), expected_end + 17);
+        rng2.next_u32();
+        rng2.next_u64();
+        assert_eq!(rng2.get_word_pos(), expected_end + 20);
+        rng2.fill_bytes(&mut buf[0..1]);
+        assert_eq!(rng2.get_word_pos(), expected_end + 21);
+    }
+
+    #[test]
+    fn test_chacha_multiple_blocks() {
+        let seed = [0,0,0,0, 1,0,0,0, 2,0,0,0, 3,0,0,0, 4,0,0,0, 5,0,0,0, 6,0,0,0, 7,0,0,0];
+        let mut rng = ChaChaRng::from_seed(seed);
+
+        // Store the 17*i-th 32-bit word,
+        // i.e., the i-th word of the i-th 16-word block
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() {
+            *i = rng.next_u32();
+            for _ in 0..16 {
+                rng.next_u32();
+            }
+        }
+        let expected = [0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036,
+                        0x49884684, 0x64efec72, 0x4be2d186, 0x3615b384,
+                        0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530,
+                        0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_true_bytes() {
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+        let mut results = [0u8; 32];
+        rng.fill_bytes(&mut results);
+        let expected = [118, 184, 224, 173, 160, 241, 61, 144,
+                        64, 93, 106, 229, 83, 134, 189, 40,
+                        189, 210, 25, 184, 160, 141, 237, 26,
+                        168, 54, 239, 204, 139, 119, 13, 199];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_nonce() {
+        // Test vector 5 from
+        // https://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
+        // Although we do not support setting a nonce, we try it here anyway so
+        // we can use this test vector.
+        let seed = [0u8; 32];
+        let mut rng = ChaChaRng::from_seed(seed);
+        // 96-bit nonce in LE order is: 0,0,0,0, 0,0,0,0, 0,0,0,2
+        rng.set_stream(2u64 << (24 + 32));
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0x374dc6c2, 0x3736d58c, 0xb904e24a, 0xcd3f93ef,
+                        0x88228b1a, 0x96a4dfb3, 0x5b76ab72, 0xc727ee54,
+                        0x0e0e978a, 0xf3145c95, 0x1b748ea8, 0xf786c297,
+                        0x99c28f5f, 0x628314e8, 0x398a19fa, 0x6ded1b53];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_chacha_clone_streams() {
+        let seed = [0,0,0,0, 1,0,0,0, 2,0,0,0, 3,0,0,0, 4,0,0,0, 5,0,0,0, 6,0,0,0, 7,0,0,0];
+        let mut rng = ChaChaRng::from_seed(seed);
+        let mut clone = rng.clone();
+        for _ in 0..16 {
+            assert_eq!(rng.next_u64(), clone.next_u64());
+        }
+
+        rng.set_stream(51);
+        for _ in 0..7 {
+            assert!(rng.next_u32() != clone.next_u32());
+        }
+        clone.set_stream(51);   // switch part way through block
+        for _ in 7..16 {
+            assert_eq!(rng.next_u32(), clone.next_u32());
+        }
+    }
+}
diff --git a/rand/rand_chacha/src/lib.rs b/rand/rand_chacha/src/lib.rs
new file mode 100644
index 0000000..8cff03a
--- /dev/null
+++ b/rand/rand_chacha/src/lib.rs
@@ -0,0 +1,25 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The ChaCha random number generator.
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
+
+#![no_std]
+
+extern crate rand_core;
+
+mod chacha;
+
+pub use chacha::{ChaChaRng, ChaChaCore};
diff --git a/rand/rand_core/CHANGELOG.md b/rand/rand_core/CHANGELOG.md
new file mode 100644
index 0000000..2cbb259
--- /dev/null
+++ b/rand/rand_core/CHANGELOG.md
@@ -0,0 +1,33 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.3.0] - 2018-09-24
+- Add `SeedableRng::seed_from_u64` for convenient seeding. (#537)
+
+## [0.2.1] - 2018-06-08
+- References to a `CryptoRng` now also implement `CryptoRng`. (#470)
+
+## [0.2.0] - 2018-05-21
+- Enable the `std` feature by default. (#409)
+- Remove `BlockRng{64}::inner` and `BlockRng::inner_mut`; instead making `core` public
+- Add `BlockRng{64}::index` and `BlockRng{64}::generate_and_set`. (#374, #419)
+- Change `BlockRngCore::Results` bound to also require `AsMut<[Self::Item]>`. (#419)
+- Implement `std::io::Read` for RngCore. (#434)
+
+## [0.1.0] - 2018-04-17
+(Split out of the Rand crate, changes here are relative to rand 0.4.2)
+- `RngCore` and `SeedableRng` are now part of `rand_core`. (#288)
+- Add modules to help implementing RNGs `impl` and `le`. (#209, #228)
+- Add `Error` and `ErrorKind`. (#225)
+- Add `CryptoRng` marker trait. (#273)
+- Add `BlockRngCore` trait. (#281)
+- Add `BlockRng` and `BlockRng64` wrappers to help implementations. (#281, #325)
+- Revise the `SeedableRng` trait. (#233)
+- Remove default implementations for `RngCore::next_u64` and `RngCore::fill_bytes`. (#288)
+- Add `RngCore::try_fill_bytes`. (#225)
+
+## [0.0.1] - 2017-09-14 (yanked)
+Experimental version as part of the rand crate refactor.
diff --git a/rand/rand_core/COPYRIGHT b/rand/rand_core/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_core/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_core/Cargo.toml b/rand/rand_core/Cargo.toml
new file mode 100644
index 0000000..1678773
--- /dev/null
+++ b/rand/rand_core/Cargo.toml
@@ -0,0 +1,28 @@
+[package]
+name = "rand_core"
+version = "0.3.0"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_core"
+homepage = "https://crates.io/crates/rand_core"
+description = """
+Core random number generator traits and tools for implementation.
+"""
+keywords = ["random", "rng"]
+categories = ["algorithms", "no-std"]
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[features]
+default = ["std"]
+std = ["alloc"]    # use std library; should be default but for above bug
+alloc = []  # enables Vec and Box support without std
+serde1 = ["serde", "serde_derive"] # enables serde for BlockRng wrapper
+
+[dependencies]
+serde = { version = "1", optional = true }
+serde_derive = { version = "^1.0.38", optional = true }
diff --git a/rand/rand_core/LICENSE-APACHE b/rand/rand_core/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_core/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
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diff --git a/rand/rand_core/LICENSE-MIT b/rand/rand_core/LICENSE-MIT
new file mode 100644
index 0000000..d93b5ba
--- /dev/null
+++ b/rand/rand_core/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright 2018 Developers of the Rand project
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
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+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
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+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_core/README.md b/rand/rand_core/README.md
new file mode 100644
index 0000000..dee6504
--- /dev/null
+++ b/rand/rand_core/README.md
@@ -0,0 +1,65 @@
+# rand_core
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_core.svg)](https://crates.io/crates/rand_core)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_core)
+[![API](https://docs.rs/rand_core/badge.svg)](https://docs.rs/rand_core)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+Core traits and error types of the [rand] library, plus tools for implementing
+RNGs.
+
+This crate is intended for use when implementing the core trait, `RngCore`; it
+defines the core traits to be implemented as well as several small functions to
+aid in their implementation and types required for error handling.
+
+The main [rand] crate re-exports most items defined in this crate, along with
+tools to convert the integer samples generated by `RngCore` to many different
+applications (including sampling from restricted ranges, conversion to floating
+point, list permutations and secure initialisation of RNGs). Most users should
+prefer to use the main [rand] crate.
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_core)
+-   [API documentation (docs.rs)](https://docs.rs/rand_core)
+-   [Changelog](CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+
+
+## Functionality
+
+The `rand_core` crate provides:
+
+-   base random number generator traits
+-   error-reporting types
+-   functionality to aid implementation of RNGs
+
+The traits and error types are also available via `rand`.
+
+## Crate Features
+
+`rand_core` supports `no_std` and `alloc`-only configurations, as well as full
+`std` functionality. The differences between `no_std` and full `std` are small,
+comprising `RngCore` support for `Box<R>` types where `R: RngCore`, as well as
+extensions to the `Error` type's functionality.
+
+Due to [rust-lang/cargo#1596](https://github.com/rust-lang/cargo/issues/1596),
+`rand_core` is built without `std` support by default. Since features are
+unioned across the whole dependency tree, any crate using `rand` with its
+default features will also enable `std` support in `rand_core`.
+
+The `serde1` feature can be used to derive `Serialize` and `Deserialize` for RNG
+implementations that use the `BlockRng` or `BlockRng64` wrappers.
+
+
+# License
+
+`rand_core` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_core/src/block.rs b/rand/rand_core/src/block.rs
new file mode 100644
index 0000000..de480e4
--- /dev/null
+++ b/rand/rand_core/src/block.rs
@@ -0,0 +1,508 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `BlockRngCore` trait and implementation helpers
+//!
+//! The [`BlockRngCore`] trait exists to assist in the implementation of RNGs
+//! which generate a block of data in a cache instead of returning generated
+//! values directly.
+//!
+//! Usage of this trait is optional, but provides two advantages:
+//! implementations only need to concern themselves with generation of the
+//! block, not the various [`RngCore`] methods (especially [`fill_bytes`], where
+//! the optimal implementations are not trivial), and this allows
+//! [`ReseedingRng`] perform periodic reseeding with very low overhead.
+//!
+//! # Example
+//! 
+//! ```norun
+//! use rand_core::block::{BlockRngCore, BlockRng};
+//! 
+//! struct MyRngCore;
+//! 
+//! impl BlockRngCore for MyRngCore {
+//!     type Results = [u32; 16];
+//!     
+//!     fn generate(&mut self, results: &mut Self::Results) {
+//!         unimplemented!()
+//!     }
+//! }
+//! 
+//! impl SeedableRng for MyRngCore {
+//!     type Seed = unimplemented!();
+//!     fn from_seed(seed: Self::Seed) -> Self {
+//!         unimplemented!()
+//!     }
+//! }
+//! 
+//! // optionally, also implement CryptoRng for MyRngCore
+//! 
+//! // Final RNG.
+//! type MyRng = BlockRng<u32, MyRngCore>;
+//! ```
+//! 
+//! [`BlockRngCore`]: trait.BlockRngCore.html
+//! [`RngCore`]: ../trait.RngCore.html
+//! [`fill_bytes`]: ../trait.RngCore.html#tymethod.fill_bytes
+//! [`ReseedingRng`]: ../../rand/rngs/adapter/struct.ReseedingRng.html
+
+use core::convert::AsRef;
+use core::fmt;
+use {RngCore, CryptoRng, SeedableRng, Error};
+use impls::{fill_via_u32_chunks, fill_via_u64_chunks};
+
+/// A trait for RNGs which do not generate random numbers individually, but in
+/// blocks (typically `[u32; N]`). This technique is commonly used by
+/// cryptographic RNGs to improve performance.
+/// 
+/// See the [module documentation](index.html) for details.
+pub trait BlockRngCore {
+    /// Results element type, e.g. `u32`.
+    type Item;
+    
+    /// Results type. This is the 'block' an RNG implementing `BlockRngCore`
+    /// generates, which will usually be an array like `[u32; 16]`.
+    type Results: AsRef<[Self::Item]> + AsMut<[Self::Item]> + Default;
+
+    /// Generate a new block of results.
+    fn generate(&mut self, results: &mut Self::Results);
+}
+
+
+/// A wrapper type implementing [`RngCore`] for some type implementing
+/// [`BlockRngCore`] with `u32` array buffer; i.e. this can be used to implement
+/// a full RNG from just a `generate` function.
+///
+/// The `core` field may be accessed directly but the results buffer may not.
+/// PRNG implementations can simply use a type alias
+/// (`pub type MyRng = BlockRng<MyRngCore>;`) but might prefer to use a
+/// wrapper type (`pub struct MyRng(BlockRng<MyRngCore>);`); the latter must
+/// re-implement `RngCore` but hides the implementation details and allows
+/// extra functionality to be defined on the RNG
+/// (e.g. `impl MyRng { fn set_stream(...){...} }`).
+///
+/// `BlockRng` has heavily optimized implementations of the [`RngCore`] methods
+/// reading values from the results buffer, as well as
+/// calling [`BlockRngCore::generate`] directly on the output array when
+/// [`fill_bytes`] / [`try_fill_bytes`] is called on a large array. These methods
+/// also handle the bookkeeping of when to generate a new batch of values.
+///
+/// No whole generated `u32` values are thown away and all values are consumed
+/// in-order. [`next_u32`] simply takes the next available `u32` value.
+/// [`next_u64`] is implemented by combining two `u32` values, least
+/// significant first. [`fill_bytes`] and [`try_fill_bytes`] consume a whole
+/// number of `u32` values, converting each `u32` to a byte slice in
+/// little-endian order. If the requested byte length is not a multiple of 4,
+/// some bytes will be discarded.
+///
+/// See also [`BlockRng64`] which uses `u64` array buffers. Currently there is
+/// no direct support for other buffer types.
+///
+/// For easy initialization `BlockRng` also implements [`SeedableRng`].
+///
+/// [`BlockRngCore`]: BlockRngCore.t.html
+/// [`BlockRngCore::generate`]: trait.BlockRngCore.html#tymethod.generate
+/// [`BlockRng64`]: struct.BlockRng64.html
+/// [`RngCore`]: ../RngCore.t.html
+/// [`next_u32`]: ../trait.RngCore.html#tymethod.next_u32
+/// [`next_u64`]: ../trait.RngCore.html#tymethod.next_u64
+/// [`fill_bytes`]: ../trait.RngCore.html#tymethod.fill_bytes
+/// [`try_fill_bytes`]: ../trait.RngCore.html#tymethod.try_fill_bytes
+/// [`SeedableRng`]: ../SeedableRng.t.html
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct BlockRng<R: BlockRngCore + ?Sized> {
+    results: R::Results,
+    index: usize,
+    /// The *core* part of the RNG, implementing the `generate` function.
+    pub core: R,
+}
+
+// Custom Debug implementation that does not expose the contents of `results`.
+impl<R: BlockRngCore + fmt::Debug> fmt::Debug for BlockRng<R> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("BlockRng")
+           .field("core", &self.core)
+           .field("result_len", &self.results.as_ref().len())
+           .field("index", &self.index)
+           .finish()
+    }
+}
+
+impl<R: BlockRngCore> BlockRng<R> {
+    /// Create a new `BlockRng` from an existing RNG implementing
+    /// `BlockRngCore`. Results will be generated on first use.
+    pub fn new(core: R) -> BlockRng<R>{
+        let results_empty = R::Results::default();
+        BlockRng {
+            core,
+            index: results_empty.as_ref().len(),
+            results: results_empty,
+        }
+    }
+
+    /// Get the index into the result buffer.
+    /// 
+    /// If this is equal to or larger than the size of the result buffer then
+    /// the buffer is "empty" and `generate()` must be called to produce new
+    /// results.
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// Reset the number of available results.
+    /// This will force a new set of results to be generated on next use.
+    pub fn reset(&mut self) {
+        self.index = self.results.as_ref().len();
+    }
+
+    /// Generate a new set of results immediately, setting the index to the
+    /// given value.
+    pub fn generate_and_set(&mut self, index: usize) {
+        assert!(index < self.results.as_ref().len());
+        self.core.generate(&mut self.results);
+        self.index = index;
+    }
+}
+
+impl<R: BlockRngCore<Item=u32>> RngCore for BlockRng<R>
+where <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
+{
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        if self.index >= self.results.as_ref().len() {
+            self.generate_and_set(0);
+        }
+
+        let value = self.results.as_ref()[self.index];
+        self.index += 1;
+        value
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        let read_u64 = |results: &[u32], index| {
+            if cfg!(any(target_arch = "x86", target_arch = "x86_64")) {
+                // requires little-endian CPU supporting unaligned reads:
+                unsafe { *(&results[index] as *const u32 as *const u64) }
+            } else {
+                let x = u64::from(results[index]);
+                let y = u64::from(results[index + 1]);
+                (y << 32) | x
+            }
+        };
+
+        let len = self.results.as_ref().len();
+
+        let index = self.index;
+        if index < len-1 {
+            self.index += 2;
+            // Read an u64 from the current index
+            read_u64(self.results.as_ref(), index)
+        } else if index >= len {
+            self.generate_and_set(2);
+            read_u64(self.results.as_ref(), 0)
+        } else {
+            let x = u64::from(self.results.as_ref()[len-1]);
+            self.generate_and_set(1);
+            let y = u64::from(self.results.as_ref()[0]);
+            (y << 32) | x
+        }
+    }
+
+    // As an optimization we try to write directly into the output buffer.
+    // This is only enabled for little-endian platforms where unaligned writes
+    // are known to be safe and fast.
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut filled = 0;
+
+        // Continue filling from the current set of results
+        if self.index < self.results.as_ref().len() {
+            let (consumed_u32, filled_u8) =
+                fill_via_u32_chunks(&self.results.as_ref()[self.index..],
+                                    dest);
+
+            self.index += consumed_u32;
+            filled += filled_u8;
+        }
+
+        let len_remainder =
+            (dest.len() - filled) % (self.results.as_ref().len() * 4);
+        let end_direct = dest.len() - len_remainder;
+
+        while filled < end_direct {
+            let dest_u32: &mut R::Results = unsafe {
+                &mut *(dest[filled..].as_mut_ptr() as
+                *mut <R as BlockRngCore>::Results)
+            };
+            self.core.generate(dest_u32);
+            filled += self.results.as_ref().len() * 4;
+            self.index = self.results.as_ref().len();
+        }
+
+        if len_remainder > 0 {
+            self.core.generate(&mut self.results);
+            let (consumed_u32, _) =
+                fill_via_u32_chunks(self.results.as_ref(),
+                                    &mut dest[filled..]);
+
+            self.index = consumed_u32;
+        }
+    }
+
+    #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut read_len = 0;
+        while read_len < dest.len() {
+            if self.index >= self.results.as_ref().len() {
+                self.generate_and_set(0);
+            }
+            let (consumed_u32, filled_u8) =
+                fill_via_u32_chunks(&self.results.as_ref()[self.index..],
+                                    &mut dest[read_len..]);
+
+            self.index += consumed_u32;
+            read_len += filled_u8;
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.fill_bytes(dest);
+        Ok(())
+    }
+}
+
+impl<R: BlockRngCore + SeedableRng> SeedableRng for BlockRng<R> {
+    type Seed = R::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Self::new(R::from_seed(seed))
+    }
+
+    fn seed_from_u64(seed: u64) -> Self {
+        Self::new(R::seed_from_u64(seed))
+    }
+
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        Ok(Self::new(R::from_rng(rng)?))
+    }
+}
+
+
+
+/// A wrapper type implementing [`RngCore`] for some type implementing
+/// [`BlockRngCore`] with `u64` array buffer; i.e. this can be used to implement
+/// a full RNG from just a `generate` function.
+///
+/// This is similar to [`BlockRng`], but specialized for algorithms that operate
+/// on `u64` values.
+///
+/// No whole generated `u64` values are thrown away and all values are consumed
+/// in-order. [`next_u64`] simply takes the next available `u64` value.
+/// [`next_u32`] is however a bit special: half of a `u64` is consumed, leaving
+/// the other half in the buffer. If the next function called is [`next_u32`]
+/// then the other half is then consumed, however both [`next_u64`] and
+/// [`fill_bytes`] discard the rest of any half-consumed `u64`s when called.
+///
+/// [`fill_bytes`] and [`try_fill_bytes`] consume a whole number of `u64`
+/// values. If the requested length is not a multiple of 8, some bytes will be
+/// discarded.
+///
+/// [`BlockRngCore`]: BlockRngCore.t.html
+/// [`RngCore`]: ../RngCore.t.html
+/// [`next_u32`]: ../trait.RngCore.html#tymethod.next_u32
+/// [`next_u64`]: ../trait.RngCore.html#tymethod.next_u64
+/// [`fill_bytes`]: ../trait.RngCore.html#tymethod.fill_bytes
+/// [`try_fill_bytes`]: ../trait.RngCore.html#tymethod.try_fill_bytes
+/// [`BlockRng`]: struct.BlockRng.html
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct BlockRng64<R: BlockRngCore + ?Sized> {
+    results: R::Results,
+    index: usize,
+    half_used: bool, // true if only half of the previous result is used
+    /// The *core* part of the RNG, implementing the `generate` function.
+    pub core: R,
+}
+
+// Custom Debug implementation that does not expose the contents of `results`.
+impl<R: BlockRngCore + fmt::Debug> fmt::Debug for BlockRng64<R> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("BlockRng64")
+           .field("core", &self.core)
+           .field("result_len", &self.results.as_ref().len())
+           .field("index", &self.index)
+           .field("half_used", &self.half_used)
+           .finish()
+    }
+}
+
+impl<R: BlockRngCore> BlockRng64<R> {
+    /// Create a new `BlockRng` from an existing RNG implementing
+    /// `BlockRngCore`. Results will be generated on first use.
+    pub fn new(core: R) -> BlockRng64<R>{
+        let results_empty = R::Results::default();
+        BlockRng64 {
+            core,
+            index: results_empty.as_ref().len(),
+            half_used: false,
+            results: results_empty,
+        }
+    }
+
+    /// Get the index into the result buffer.
+    ///
+    /// If this is equal to or larger than the size of the result buffer then
+    /// the buffer is "empty" and `generate()` must be called to produce new
+    /// results.
+    pub fn index(&self) -> usize {
+        self.index
+    }
+
+    /// Reset the number of available results.
+    /// This will force a new set of results to be generated on next use.
+    pub fn reset(&mut self) {
+        self.index = self.results.as_ref().len();
+        self.half_used = false;
+    }
+
+    /// Generate a new set of results immediately, setting the index to the
+    /// given value.
+    pub fn generate_and_set(&mut self, index: usize) {
+        assert!(index < self.results.as_ref().len());
+        self.core.generate(&mut self.results);
+        self.index = index;
+        self.half_used = false;
+    }
+}
+
+impl<R: BlockRngCore<Item=u64>> RngCore for BlockRng64<R>
+where <R as BlockRngCore>::Results: AsRef<[u64]> + AsMut<[u64]>
+{
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        let mut index = self.index * 2 - self.half_used as usize;
+        if index >= self.results.as_ref().len() * 2 {
+            self.core.generate(&mut self.results);
+            self.index = 0;
+            // `self.half_used` is by definition `false`
+            self.half_used = false;
+            index = 0;
+        }
+
+        self.half_used = !self.half_used;
+        self.index += self.half_used as usize;
+
+        // Index as if this is a u32 slice.
+        unsafe {
+            let results =
+                &*(self.results.as_ref() as *const [u64] as *const [u32]);
+            if cfg!(target_endian = "little") {
+                *results.get_unchecked(index)
+            } else {
+                *results.get_unchecked(index ^ 1)
+            }
+        }
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        if self.index >= self.results.as_ref().len() {
+            self.core.generate(&mut self.results);
+            self.index = 0;
+        }
+
+        let value = self.results.as_ref()[self.index];
+        self.index += 1;
+        self.half_used = false;
+        value
+    }
+
+    // As an optimization we try to write directly into the output buffer.
+    // This is only enabled for little-endian platforms where unaligned writes
+    // are known to be safe and fast.
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut filled = 0;
+        self.half_used = false;
+
+        // Continue filling from the current set of results
+        if self.index < self.results.as_ref().len() {
+            let (consumed_u64, filled_u8) =
+                fill_via_u64_chunks(&self.results.as_ref()[self.index..],
+                                    dest);
+
+            self.index += consumed_u64;
+            filled += filled_u8;
+        }
+
+        let len_remainder =
+            (dest.len() - filled) % (self.results.as_ref().len() * 8);
+        let end_direct = dest.len() - len_remainder;
+
+        while filled < end_direct {
+            let dest_u64: &mut R::Results = unsafe {
+                ::core::mem::transmute(dest[filled..].as_mut_ptr())
+            };
+            self.core.generate(dest_u64);
+            filled += self.results.as_ref().len() * 8;
+            self.index = self.results.as_ref().len();
+        }
+
+        if len_remainder > 0 {
+            self.core.generate(&mut self.results);
+            let (consumed_u64, _) =
+                fill_via_u64_chunks(&mut self.results.as_ref(),
+                                    &mut dest[filled..]);
+
+            self.index = consumed_u64;
+        }
+    }
+
+    #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        let mut read_len = 0;
+        self.half_used = false;
+        while read_len < dest.len() {
+            if self.index as usize >= self.results.as_ref().len() {
+                self.core.generate(&mut self.results);
+                self.index = 0;
+            }
+
+            let (consumed_u64, filled_u8) =
+                fill_via_u64_chunks(&self.results.as_ref()[self.index as usize..],
+                                    &mut dest[read_len..]);
+
+            self.index += consumed_u64;
+            read_len += filled_u8;
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
+
+impl<R: BlockRngCore + SeedableRng> SeedableRng for BlockRng64<R> {
+    type Seed = R::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Self::new(R::from_seed(seed))
+    }
+
+    fn seed_from_u64(seed: u64) -> Self {
+        Self::new(R::seed_from_u64(seed))
+    }
+
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        Ok(Self::new(R::from_rng(rng)?))
+    }
+}
+
+impl<R: BlockRngCore + CryptoRng> CryptoRng for BlockRng<R> {}
diff --git a/rand/rand_core/src/error.rs b/rand/rand_core/src/error.rs
new file mode 100644
index 0000000..5a8459e
--- /dev/null
+++ b/rand/rand_core/src/error.rs
@@ -0,0 +1,177 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Error types
+
+use core::fmt;
+
+#[cfg(feature="std")]
+use std::error::Error as stdError;
+#[cfg(feature="std")]
+use std::io;
+
+/// Error kind which can be matched over.
+#[derive(PartialEq, Eq, Debug, Copy, Clone)]
+pub enum ErrorKind {
+    /// Feature is not available; not recoverable.
+    /// 
+    /// This is the most permanent failure type and implies the error cannot be
+    /// resolved simply by retrying (e.g. the feature may not exist in this
+    /// build of the application or on the current platform).
+    Unavailable,
+    /// General failure; there may be a chance of recovery on retry.
+    /// 
+    /// This is the catch-all kind for errors from known and unknown sources
+    /// which do not have a more specific kind / handling method.
+    /// 
+    /// It is suggested to retry a couple of times or retry later when
+    /// handling; some error sources may be able to resolve themselves,
+    /// although this is not likely.
+    Unexpected,
+    /// A transient failure which likely can be resolved or worked around.
+    /// 
+    /// This error kind exists for a few specific cases where it is known that
+    /// the error likely can be resolved internally, but is reported anyway.
+    Transient,
+    /// Not ready yet: recommended to try again a little later.
+    /// 
+    /// This error kind implies the generator needs more time or needs some
+    /// other part of the application to do something else first before it is
+    /// ready for use; for example this may be used by external generators
+    /// which require time for initialization.
+    NotReady,
+    #[doc(hidden)]
+    __Nonexhaustive,
+}
+
+impl ErrorKind {
+    /// True if this kind of error may resolve itself on retry.
+    /// 
+    /// See also `should_wait()`.
+    pub fn should_retry(self) -> bool {
+        self != ErrorKind::Unavailable
+    }
+    
+    /// True if we should retry but wait before retrying
+    /// 
+    /// This implies `should_retry()` is true.
+    pub fn should_wait(self) -> bool {
+        self == ErrorKind::NotReady
+    }
+    
+    /// A description of this error kind
+    pub fn description(self) -> &'static str {
+        match self {
+            ErrorKind::Unavailable => "permanently unavailable",
+            ErrorKind::Unexpected => "unexpected failure",
+            ErrorKind::Transient => "transient failure",
+            ErrorKind::NotReady => "not ready yet",
+            ErrorKind::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
+
+
+/// Error type of random number generators
+/// 
+/// This is a relatively simple error type, designed for compatibility with and
+/// without the Rust `std` library. It embeds a "kind" code, a message (static
+/// string only), and an optional chained cause (`std` only). The `kind` and
+/// `msg` fields can be accessed directly; cause can be accessed via
+/// `std::error::Error::cause` or `Error::take_cause`. Construction can only be
+/// done via `Error::new` or `Error::with_cause`.
+#[derive(Debug)]
+pub struct Error {
+    /// The error kind
+    pub kind: ErrorKind,
+    /// The error message
+    pub msg: &'static str,
+    #[cfg(feature="std")]
+    cause: Option<Box<stdError + Send + Sync>>,
+}
+
+impl Error {
+    /// Create a new instance, with specified kind and a message.
+    pub fn new(kind: ErrorKind, msg: &'static str) -> Self {
+        #[cfg(feature="std")] {
+            Error { kind, msg, cause: None }
+        }
+        #[cfg(not(feature="std"))] {
+            Error { kind, msg }
+        }
+    }
+    
+    /// Create a new instance, with specified kind, message, and a
+    /// chained cause.
+    /// 
+    /// Note: `stdError` is an alias for `std::error::Error`.
+    /// 
+    /// If not targetting `std` (i.e. `no_std`), this function is replaced by
+    /// another with the same prototype, except that there are no bounds on the
+    /// type `E` (because both `Box` and `stdError` are unavailable), and the
+    /// `cause` is ignored.
+    #[cfg(feature="std")]
+    pub fn with_cause<E>(kind: ErrorKind, msg: &'static str, cause: E) -> Self
+        where E: Into<Box<stdError + Send + Sync>>
+    {
+        Error { kind, msg, cause: Some(cause.into()) }
+    }
+    
+    /// Create a new instance, with specified kind, message, and a
+    /// chained cause.
+    /// 
+    /// In `no_std` mode the *cause* is ignored.
+    #[cfg(not(feature="std"))]
+    pub fn with_cause<E>(kind: ErrorKind, msg: &'static str, _cause: E) -> Self {
+        Error { kind, msg }
+    }
+    
+    /// Take the cause, if any. This allows the embedded cause to be extracted.
+    /// This uses `Option::take`, leaving `self` with no cause.
+    #[cfg(feature="std")]
+    pub fn take_cause(&mut self) -> Option<Box<stdError + Send + Sync>> {
+        self.cause.take()
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[cfg(feature="std")] {
+            if let Some(ref cause) = self.cause {
+                return write!(f, "{} ({}); cause: {}",
+                        self.msg, self.kind.description(), cause);
+            }
+        }
+        write!(f, "{} ({})", self.msg, self.kind.description())
+    }
+}
+
+#[cfg(feature="std")]
+impl stdError for Error {
+    fn description(&self) -> &str {
+        self.msg
+    }
+
+    fn cause(&self) -> Option<&stdError> {
+        self.cause.as_ref().map(|e| e.as_ref() as &stdError)
+    }
+}
+
+#[cfg(feature="std")]
+impl From<Error> for io::Error {
+    fn from(error: Error) -> Self {
+        use std::io::ErrorKind::*;
+        match error.kind {
+            ErrorKind::Unavailable => io::Error::new(NotFound, error),
+            ErrorKind::Unexpected |
+            ErrorKind::Transient => io::Error::new(Other, error),
+            ErrorKind::NotReady => io::Error::new(WouldBlock, error),
+            ErrorKind::__Nonexhaustive => unreachable!(),
+        }
+    }
+}
diff --git a/rand/rand_core/src/impls.rs b/rand/rand_core/src/impls.rs
new file mode 100644
index 0000000..57bdd07
--- /dev/null
+++ b/rand/rand_core/src/impls.rs
@@ -0,0 +1,165 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Helper functions for implementing `RngCore` functions.
+//!
+//! For cross-platform reproducibility, these functions all use Little Endian:
+//! least-significant part first. For example, `next_u64_via_u32` takes `u32`
+//! values `x, y`, then outputs `(y << 32) | x`. To implement `next_u32`
+//! from `next_u64` in little-endian order, one should use `next_u64() as u32`.
+//!
+//! Byte-swapping (like the std `to_le` functions) is only needed to convert
+//! to/from byte sequences, and since its purpose is reproducibility,
+//! non-reproducible sources (e.g. `OsRng`) need not bother with it.
+
+use core::intrinsics::transmute;
+use core::ptr::copy_nonoverlapping;
+use core::slice;
+use core::cmp::min;
+use core::mem::size_of;
+use RngCore;
+
+
+/// Implement `next_u64` via `next_u32`, little-endian order.
+pub fn next_u64_via_u32<R: RngCore + ?Sized>(rng: &mut R) -> u64 {
+    // Use LE; we explicitly generate one value before the next.
+    let x = u64::from(rng.next_u32());
+    let y = u64::from(rng.next_u32());
+    (y << 32) | x
+}
+
+/// Implement `fill_bytes` via `next_u64` and `next_u32`, little-endian order.
+///
+/// The fastest way to fill a slice is usually to work as long as possible with
+/// integers. That is why this method mostly uses `next_u64`, and only when
+/// there are 4 or less bytes remaining at the end of the slice it uses
+/// `next_u32` once.
+pub fn fill_bytes_via_next<R: RngCore + ?Sized>(rng: &mut R, dest: &mut [u8]) {
+    let mut left = dest;
+    while left.len() >= 8 {
+        let (l, r) = {left}.split_at_mut(8);
+        left = r;
+        let chunk: [u8; 8] = unsafe {
+            transmute(rng.next_u64().to_le())
+        };
+        l.copy_from_slice(&chunk);
+    }
+    let n = left.len();
+    if n > 4 {
+        let chunk: [u8; 8] = unsafe {
+            transmute(rng.next_u64().to_le())
+        };
+        left.copy_from_slice(&chunk[..n]);
+    } else if n > 0 {
+        let chunk: [u8; 4] = unsafe {
+            transmute(rng.next_u32().to_le())
+        };
+        left.copy_from_slice(&chunk[..n]);
+    }
+}
+
+macro_rules! impl_uint_from_fill {
+    ($rng:expr, $ty:ty, $N:expr) => ({
+        debug_assert!($N == size_of::<$ty>());
+
+        let mut int: $ty = 0;
+        unsafe {
+            let ptr = &mut int as *mut $ty as *mut u8;
+            let slice = slice::from_raw_parts_mut(ptr, $N);
+            $rng.fill_bytes(slice);
+        }
+        int
+    });
+}
+
+macro_rules! fill_via_chunks {
+    ($src:expr, $dst:expr, $ty:ty, $size:expr) => ({
+        let chunk_size_u8 = min($src.len() * $size, $dst.len());
+        let chunk_size = (chunk_size_u8 + $size - 1) / $size;
+        if cfg!(target_endian="little") {
+            unsafe {
+                copy_nonoverlapping(
+                    $src.as_ptr() as *const u8,
+                    $dst.as_mut_ptr(),
+                    chunk_size_u8);
+            }
+        } else {
+            for (&n, chunk) in $src.iter().zip($dst.chunks_mut($size)) {
+                let tmp = n.to_le();
+                let src_ptr = &tmp as *const $ty as *const u8;
+                unsafe {
+                    copy_nonoverlapping(src_ptr,
+                                        chunk.as_mut_ptr(),
+                                        chunk.len());
+                }
+            }
+        }
+
+        (chunk_size, chunk_size_u8)
+    });
+}
+
+/// Implement `fill_bytes` by reading chunks from the output buffer of a block
+/// based RNG.
+///
+/// The return values are `(consumed_u32, filled_u8)`.
+///
+/// `filled_u8` is the number of filled bytes in `dest`, which may be less than
+/// the length of `dest`.
+/// `consumed_u32` is the number of words consumed from `src`, which is the same
+/// as `filled_u8 / 4` rounded up.
+///
+/// # Example
+/// (from `IsaacRng`)
+///
+/// ```ignore
+/// fn fill_bytes(&mut self, dest: &mut [u8]) {
+///     let mut read_len = 0;
+///     while read_len < dest.len() {
+///         if self.index >= self.rsl.len() {
+///             self.isaac();
+///         }
+///
+///         let (consumed_u32, filled_u8) =
+///             impls::fill_via_u32_chunks(&mut self.rsl[self.index..],
+///                                        &mut dest[read_len..]);
+///
+///         self.index += consumed_u32;
+///         read_len += filled_u8;
+///     }
+/// }
+/// ```
+pub fn fill_via_u32_chunks(src: &[u32], dest: &mut [u8]) -> (usize, usize) {
+    fill_via_chunks!(src, dest, u32, 4)
+}
+
+/// Implement `fill_bytes` by reading chunks from the output buffer of a block
+/// based RNG.
+///
+/// The return values are `(consumed_u64, filled_u8)`.
+/// `filled_u8` is the number of filled bytes in `dest`, which may be less than
+/// the length of `dest`.
+/// `consumed_u64` is the number of words consumed from `src`, which is the same
+/// as `filled_u8 / 8` rounded up.
+///
+/// See `fill_via_u32_chunks` for an example.
+pub fn fill_via_u64_chunks(src: &[u64], dest: &mut [u8]) -> (usize, usize) {
+    fill_via_chunks!(src, dest, u64, 8)
+}
+
+/// Implement `next_u32` via `fill_bytes`, little-endian order.
+pub fn next_u32_via_fill<R: RngCore + ?Sized>(rng: &mut R) -> u32 {
+    impl_uint_from_fill!(rng, u32, 4)
+}
+
+/// Implement `next_u64` via `fill_bytes`, little-endian order.
+pub fn next_u64_via_fill<R: RngCore + ?Sized>(rng: &mut R) -> u64 {
+    impl_uint_from_fill!(rng, u64, 8)
+}
+
+// TODO: implement tests for the above
diff --git a/rand/rand_core/src/le.rs b/rand/rand_core/src/le.rs
new file mode 100644
index 0000000..266651f
--- /dev/null
+++ b/rand/rand_core/src/le.rs
@@ -0,0 +1,68 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Little-Endian utilities
+//! 
+//! Little-Endian order has been chosen for internal usage; this makes some
+//! useful functions available.
+
+use core::ptr;
+
+macro_rules! read_slice {
+    ($src:expr, $dst:expr, $size:expr, $which:ident) => {{
+        assert_eq!($src.len(), $size * $dst.len());
+
+        unsafe {
+            ptr::copy_nonoverlapping(
+                $src.as_ptr(),
+                $dst.as_mut_ptr() as *mut u8,
+                $src.len());
+        }
+        for v in $dst.iter_mut() {
+            *v = v.$which();
+        }
+    }};
+}
+
+/// Reads unsigned 32 bit integers from `src` into `dst`.
+/// Borrowed from the `byteorder` crate.
+#[inline]
+pub fn read_u32_into(src: &[u8], dst: &mut [u32]) {
+    read_slice!(src, dst, 4, to_le);
+}
+
+/// Reads unsigned 64 bit integers from `src` into `dst`.
+/// Borrowed from the `byteorder` crate.
+#[inline]
+pub fn read_u64_into(src: &[u8], dst: &mut [u64]) {
+    read_slice!(src, dst, 8, to_le);
+}
+
+#[test]
+fn test_read() {
+    let bytes = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    
+    let mut buf = [0u32; 4];
+    read_u32_into(&bytes, &mut buf);
+    assert_eq!(buf[0], 0x04030201);
+    assert_eq!(buf[3], 0x100F0E0D);
+    
+    let mut buf = [0u32; 3];
+    read_u32_into(&bytes[1..13], &mut buf);  // unaligned
+    assert_eq!(buf[0], 0x05040302);
+    assert_eq!(buf[2], 0x0D0C0B0A);
+    
+    let mut buf = [0u64; 2];
+    read_u64_into(&bytes, &mut buf);
+    assert_eq!(buf[0], 0x0807060504030201);
+    assert_eq!(buf[1], 0x100F0E0D0C0B0A09);
+    
+    let mut buf = [0u64; 1];
+    read_u64_into(&bytes[7..15], &mut buf); // unaligned
+    assert_eq!(buf[0], 0x0F0E0D0C0B0A0908);
+}
diff --git a/rand/rand_core/src/lib.rs b/rand/rand_core/src/lib.rs
new file mode 100644
index 0000000..a65db93
--- /dev/null
+++ b/rand/rand_core/src/lib.rs
@@ -0,0 +1,486 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Random number generation traits
+//! 
+//! This crate is mainly of interest to crates publishing implementations of
+//! [`RngCore`]. Other users are encouraged to use the [rand] crate instead
+//! which re-exports the main traits and error types.
+//!
+//! [`RngCore`] is the core trait implemented by algorithmic pseudo-random number
+//! generators and external random-number sources.
+//! 
+//! [`SeedableRng`] is an extension trait for construction from fixed seeds and
+//! other random number generators.
+//! 
+//! [`Error`] is provided for error-handling. It is safe to use in `no_std`
+//! environments.
+//! 
+//! The [`impls`] and [`le`] sub-modules include a few small functions to assist
+//! implementation of [`RngCore`].
+//! 
+//! [rand]: https://crates.io/crates/rand
+//! [`RngCore`]: trait.RngCore.html
+//! [`SeedableRng`]: trait.SeedableRng.html
+//! [`Error`]: struct.Error.html
+//! [`impls`]: impls/index.html
+//! [`le`]: le/index.html
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
+
+#![cfg_attr(not(feature="std"), no_std)]
+#![cfg_attr(all(feature="alloc", not(feature="std")), feature(alloc))]
+
+#[cfg(feature="std")] extern crate core;
+#[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
+#[cfg(feature="serde1")] extern crate serde;
+#[cfg(feature="serde1")] #[macro_use] extern crate serde_derive;
+
+
+use core::default::Default;
+use core::convert::AsMut;
+use core::ptr::copy_nonoverlapping;
+
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::boxed::Box;
+
+pub use error::{ErrorKind, Error};
+
+
+mod error;
+pub mod block;
+pub mod impls;
+pub mod le;
+
+
+/// The core of a random number generator.
+/// 
+/// This trait encapsulates the low-level functionality common to all
+/// generators, and is the "back end", to be implemented by generators.
+/// End users should normally use [`Rng`] from the [rand] crate, which is
+/// automatically implemented for every type implementing `RngCore`.
+/// 
+/// Three different methods for generating random data are provided since the
+/// optimal implementation of each is dependent on the type of generator. There
+/// is no required relationship between the output of each; e.g. many
+/// implementations of [`fill_bytes`] consume a whole number of `u32` or `u64`
+/// values and drop any remaining unused bytes.
+/// 
+/// The [`try_fill_bytes`] method is a variant of [`fill_bytes`] allowing error
+/// handling; it is not deemed sufficiently useful to add equivalents for
+/// [`next_u32`] or [`next_u64`] since the latter methods are almost always used
+/// with algorithmic generators (PRNGs), which are normally infallible.
+/// 
+/// Algorithmic generators implementing [`SeedableRng`] should normally have
+/// *portable, reproducible* output, i.e. fix Endianness when converting values
+/// to avoid platform differences, and avoid making any changes which affect
+/// output (except by communicating that the release has breaking changes).
+/// 
+/// Typically implementators will implement only one of the methods available
+/// in this trait directly, then use the helper functions from the
+/// [`rand_core::impls`] module to implement the other methods.
+/// 
+/// It is recommended that implementations also implement:
+/// 
+/// - `Debug` with a custom implementation which *does not* print any internal
+///   state (at least, [`CryptoRng`]s should not risk leaking state through
+///   `Debug`).
+/// - `Serialize` and `Deserialize` (from Serde), preferably making Serde
+///   support optional at the crate level in PRNG libs.
+/// - `Clone`, if possible.
+/// - *never* implement `Copy` (accidental copies may cause repeated values).
+/// - *do not* implement `Default` for pseudorandom generators, but instead
+///   implement [`SeedableRng`], to guide users towards proper seeding.
+///   External / hardware RNGs can choose to implement `Default`.
+/// - `Eq` and `PartialEq` could be implemented, but are probably not useful.
+/// 
+/// # Example
+/// 
+/// A simple example, obviously not generating very *random* output:
+/// 
+/// ```
+/// #![allow(dead_code)]
+/// use rand_core::{RngCore, Error, impls};
+/// 
+/// struct CountingRng(u64);
+/// 
+/// impl RngCore for CountingRng {
+///     fn next_u32(&mut self) -> u32 {
+///         self.next_u64() as u32
+///     }
+///     
+///     fn next_u64(&mut self) -> u64 {
+///         self.0 += 1;
+///         self.0
+///     }
+///     
+///     fn fill_bytes(&mut self, dest: &mut [u8]) {
+///         impls::fill_bytes_via_next(self, dest)
+///     }
+///     
+///     fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+///         Ok(self.fill_bytes(dest))
+///     }
+/// }
+/// ```
+/// 
+/// [rand]: https://crates.io/crates/rand
+/// [`Rng`]: ../rand/trait.Rng.html
+/// [`SeedableRng`]: trait.SeedableRng.html
+/// [`rand_core::impls`]: ../rand_core/impls/index.html
+/// [`try_fill_bytes`]: trait.RngCore.html#tymethod.try_fill_bytes
+/// [`fill_bytes`]: trait.RngCore.html#tymethod.fill_bytes
+/// [`next_u32`]: trait.RngCore.html#tymethod.next_u32
+/// [`next_u64`]: trait.RngCore.html#tymethod.next_u64
+/// [`CryptoRng`]: trait.CryptoRng.html
+pub trait RngCore {
+    /// Return the next random `u32`.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// using `self.next_u64() as u32` or
+    /// [via `fill_bytes`](../rand_core/impls/fn.next_u32_via_fill.html).
+    fn next_u32(&mut self) -> u32;
+
+    /// Return the next random `u64`.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// [via `next_u32`](../rand_core/impls/fn.next_u64_via_u32.html) or
+    /// [via `fill_bytes`](../rand_core/impls/fn.next_u64_via_fill.html).
+    fn next_u64(&mut self) -> u64;
+
+    /// Fill `dest` with random data.
+    ///
+    /// RNGs must implement at least one method from this trait directly. In
+    /// the case this method is not implemented directly, it can be implemented
+    /// [via `next_u*`](../rand_core/impls/fn.fill_bytes_via_next.html) or
+    /// via `try_fill_bytes`; if this generator can fail the implementation
+    /// must choose how best to handle errors here (e.g. panic with a
+    /// descriptive message or log a warning and retry a few times).
+    /// 
+    /// This method should guarantee that `dest` is entirely filled
+    /// with new data, and may panic if this is impossible
+    /// (e.g. reading past the end of a file that is being used as the
+    /// source of randomness).
+    fn fill_bytes(&mut self, dest: &mut [u8]);
+
+    /// Fill `dest` entirely with random data.
+    ///
+    /// This is the only method which allows an RNG to report errors while
+    /// generating random data thus making this the primary method implemented
+    /// by external (true) RNGs (e.g. `OsRng`) which can fail. It may be used
+    /// directly to generate keys and to seed (infallible) PRNGs.
+    /// 
+    /// Other than error handling, this method is identical to [`fill_bytes`];
+    /// thus this may be implemented using `Ok(self.fill_bytes(dest))` or
+    /// `fill_bytes` may be implemented with
+    /// `self.try_fill_bytes(dest).unwrap()` or more specific error handling.
+    /// 
+    /// [`fill_bytes`]: trait.RngCore.html#method.fill_bytes
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>;
+}
+
+/// A marker trait used to indicate that an [`RngCore`] or [`BlockRngCore`]
+/// implementation is supposed to be cryptographically secure.
+/// 
+/// *Cryptographically secure generators*, also known as *CSPRNGs*, should
+/// satisfy an additional properties over other generators: given the first
+/// *k* bits of an algorithm's output
+/// sequence, it should not be possible using polynomial-time algorithms to
+/// predict the next bit with probability significantly greater than 50%.
+/// 
+/// Some generators may satisfy an additional property, however this is not
+/// required by this trait: if the CSPRNG's state is revealed, it should not be
+/// computationally-feasible to reconstruct output prior to this. Some other
+/// generators allow backwards-computation and are consided *reversible*.
+/// 
+/// Note that this trait is provided for guidance only and cannot guarantee
+/// suitability for cryptographic applications. In general it should only be
+/// implemented for well-reviewed code implementing well-regarded algorithms.
+/// 
+/// Note also that use of a `CryptoRng` does not protect against other
+/// weaknesses such as seeding from a weak entropy source or leaking state.
+/// 
+/// [`RngCore`]: trait.RngCore.html
+/// [`BlockRngCore`]: ../rand_core/block/trait.BlockRngCore.html
+pub trait CryptoRng {}
+
+/// A random number generator that can be explicitly seeded.
+///
+/// This trait encapsulates the low-level functionality common to all
+/// pseudo-random number generators (PRNGs, or algorithmic generators).
+/// 
+/// The [`rand::FromEntropy`] trait is automatically implemented for every type
+/// implementing `SeedableRng`, providing a convenient `from_entropy()`
+/// constructor.
+/// 
+/// [`rand::FromEntropy`]: ../rand/trait.FromEntropy.html
+pub trait SeedableRng: Sized {
+    /// Seed type, which is restricted to types mutably-dereferencable as `u8`
+    /// arrays (we recommend `[u8; N]` for some `N`).
+    ///
+    /// It is recommended to seed PRNGs with a seed of at least circa 100 bits,
+    /// which means an array of `[u8; 12]` or greater to avoid picking RNGs with
+    /// partially overlapping periods.
+    ///
+    /// For cryptographic RNG's a seed of 256 bits is recommended, `[u8; 32]`.
+    ///
+    ///
+    /// # Implementing `SeedableRng` for RNGs with large seeds
+    ///
+    /// Note that the required traits `core::default::Default` and
+    /// `core::convert::AsMut<u8>` are not implemented for large arrays
+    /// `[u8; N]` with `N` > 32. To be able to implement the traits required by
+    /// `SeedableRng` for RNGs with such large seeds, the newtype pattern can be
+    /// used:
+    ///
+    /// ```
+    /// use rand_core::SeedableRng;
+    ///
+    /// const N: usize = 64;
+    /// pub struct MyRngSeed(pub [u8; N]);
+    /// pub struct MyRng(MyRngSeed);
+    ///
+    /// impl Default for MyRngSeed {
+    ///     fn default() -> MyRngSeed {
+    ///         MyRngSeed([0; N])
+    ///     }
+    /// }
+    ///
+    /// impl AsMut<[u8]> for MyRngSeed {
+    ///     fn as_mut(&mut self) -> &mut [u8] {
+    ///         &mut self.0
+    ///     }
+    /// }
+    ///
+    /// impl SeedableRng for MyRng {
+    ///     type Seed = MyRngSeed;
+    ///
+    ///     fn from_seed(seed: MyRngSeed) -> MyRng {
+    ///         MyRng(seed)
+    ///     }
+    /// }
+    /// ```
+    type Seed: Sized + Default + AsMut<[u8]>;
+
+    /// Create a new PRNG using the given seed.
+    ///
+    /// PRNG implementations are allowed to assume that bits in the seed are
+    /// well distributed. That means usually that the number of one and zero
+    /// bits are about equal, and values like 0, 1 and (size - 1) are unlikely.
+    ///
+    /// PRNG implementations are recommended to be reproducible. A PRNG seeded
+    /// using this function with a fixed seed should produce the same sequence
+    /// of output in the future and on different architectures (with for example
+    /// different endianness).
+    ///
+    /// It is however not required that this function yield the same state as a
+    /// reference implementation of the PRNG given equivalent seed; if necessary
+    /// another constructor replicating behaviour from a reference
+    /// implementation can be added.
+    ///
+    /// PRNG implementations should make sure `from_seed` never panics. In the
+    /// case that some special values (like an all zero seed) are not viable
+    /// seeds it is preferable to map these to alternative constant value(s),
+    /// for example `0xBAD5EEDu32` or `0x0DDB1A5E5BAD5EEDu64` ("odd biases? bad
+    /// seed"). This is assuming only a small number of values must be rejected.
+    fn from_seed(seed: Self::Seed) -> Self;
+    
+    /// Create a new PRNG using a `u64` seed.
+    /// 
+    /// This is a convenience-wrapper around `from_seed` to allow construction
+    /// of any `SeedableRng` from a simple `u64` value. It is designed such that
+    /// low Hamming Weight numbers like 0 and 1 can be used and should still
+    /// result in good, independent seeds to the PRNG which is returned.
+    /// 
+    /// This **is not suitable for cryptography**, as should be clear given that
+    /// the input size is only 64 bits.
+    /// 
+    /// Implementations for PRNGs *may* provide their own implementations of
+    /// this function, but the default implementation should be good enough for
+    /// all purposes. *Changing* the implementation of this function should be
+    /// considered a value-breaking change.
+    fn seed_from_u64(mut state: u64) -> Self {
+        // We use PCG32 to generate a u32 sequence, and copy to the seed
+        const MUL: u64 = 6364136223846793005;
+        const INC: u64 = 11634580027462260723;
+        
+        let mut seed = Self::Seed::default();
+        for chunk in seed.as_mut().chunks_mut(4) {
+            // We advance the state first (to get away from the input value,
+            // in case it has low Hamming Weight).
+            state = state.wrapping_mul(MUL).wrapping_add(INC);
+            
+            // Use PCG output function with to_le to generate x:
+            let xorshifted = (((state >> 18) ^ state) >> 27) as u32;
+            let rot = (state >> 59) as u32;
+            let x = xorshifted.rotate_right(rot).to_le();
+            
+            unsafe {
+                let p = &x as *const u32 as *const u8;
+                copy_nonoverlapping(p, chunk.as_mut_ptr(), chunk.len());
+            }
+        }
+        
+        Self::from_seed(seed)
+    }
+    
+    /// Create a new PRNG seeded from another `Rng`.
+    ///
+    /// This is the recommended way to initialize PRNGs with fresh entropy. The
+    /// [`FromEntropy`] trait provides a convenient `from_entropy` method
+    /// based on `from_rng`.
+    /// 
+    /// Usage of this method is not recommended when reproducibility is required
+    /// since implementing PRNGs are not required to fix Endianness and are
+    /// allowed to modify implementations in new releases.
+    ///
+    /// It is important to use a good source of randomness to initialize the
+    /// PRNG. Cryptographic PRNG may be rendered insecure when seeded from a
+    /// non-cryptographic PRNG or with insufficient entropy.
+    /// Many non-cryptographic PRNGs will show statistical bias in their first
+    /// results if their seed numbers are small or if there is a simple pattern
+    /// between them.
+    ///
+    /// Prefer to seed from a strong external entropy source like [`OsRng`] or
+    /// from a cryptographic PRNG; if creating a new generator for cryptographic
+    /// uses you *must* seed from a strong source.
+    ///
+    /// Seeding a small PRNG from another small PRNG is possible, but
+    /// something to be careful with. An extreme example of how this can go
+    /// wrong is seeding an Xorshift RNG from another Xorshift RNG, which
+    /// will effectively clone the generator. In general seeding from a
+    /// generator which is hard to predict is probably okay.
+    ///
+    /// PRNG implementations are allowed to assume that a good RNG is provided
+    /// for seeding, and that it is cryptographically secure when appropriate.
+    /// 
+    /// [`FromEntropy`]: ../rand/trait.FromEntropy.html
+    /// [`OsRng`]: ../rand/rngs/struct.OsRng.html
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> {
+        let mut seed = Self::Seed::default();
+        rng.try_fill_bytes(seed.as_mut())?;
+        Ok(Self::from_seed(seed))
+    }
+}
+
+// Implement `RngCore` for references to an `RngCore`.
+// Force inlining all functions, so that it is up to the `RngCore`
+// implementation and the optimizer to decide on inlining.
+impl<'a, R: RngCore + ?Sized> RngCore for &'a mut R {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        (**self).next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        (**self).next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        (**self).fill_bytes(dest)
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        (**self).try_fill_bytes(dest)
+    }
+}
+
+// Implement `RngCore` for boxed references to an `RngCore`.
+// Force inlining all functions, so that it is up to the `RngCore`
+// implementation and the optimizer to decide on inlining.
+#[cfg(feature="alloc")]
+impl<R: RngCore + ?Sized> RngCore for Box<R> {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        (**self).next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        (**self).next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        (**self).fill_bytes(dest)
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        (**self).try_fill_bytes(dest)
+    }
+}
+
+#[cfg(feature="std")]
+impl std::io::Read for RngCore {
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, std::io::Error> {
+        self.try_fill_bytes(buf)?;
+        Ok(buf.len())
+    }
+}
+
+// Implement `CryptoRng` for references to an `CryptoRng`.
+impl<'a, R: CryptoRng + ?Sized> CryptoRng for &'a mut R {}
+
+// Implement `CryptoRng` for boxed references to an `CryptoRng`.
+#[cfg(feature="alloc")]
+impl<R: CryptoRng + ?Sized> CryptoRng for Box<R> {}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    
+    #[test]
+    fn test_seed_from_u64() {
+        struct SeedableNum(u64);
+        impl SeedableRng for SeedableNum {
+            type Seed = [u8; 8];
+            fn from_seed(seed: Self::Seed) -> Self {
+                let mut x = [0u64; 1];
+                le::read_u64_into(&seed, &mut x);
+                SeedableNum(x[0])
+            }
+        }
+        
+        const N: usize = 8;
+        const SEEDS: [u64; N] = [0u64, 1, 2, 3, 4, 8, 16, -1i64 as u64];
+        let mut results = [0u64; N];
+        for (i, seed) in SEEDS.iter().enumerate() {
+            let SeedableNum(x) = SeedableNum::seed_from_u64(*seed);
+            results[i] = x;
+        }
+        
+        for (i1, r1) in results.iter().enumerate() {
+            let weight = r1.count_ones();
+            // This is the binomial distribution B(64, 0.5), so chance of
+            // weight < 20 is binocdf(19, 64, 0.5) = 7.8e-4, and same for
+            // weight > 44.
+            assert!(weight >= 20 && weight <= 44);
+            
+            for (i2, r2) in results.iter().enumerate() {
+                if i1 == i2 { continue; }
+                let diff_weight = (r1 ^ r2).count_ones();
+                assert!(diff_weight >= 20);
+            }
+        }
+        
+        // value-breakage test:
+        assert_eq!(results[0], 5029875928683246316);
+    }
+}
diff --git a/rand/rand_hc/CHANGELOG.md b/rand/rand_hc/CHANGELOG.md
new file mode 100644
index 0000000..d0c4a2f
--- /dev/null
+++ b/rand/rand_hc/CHANGELOG.md
@@ -0,0 +1,8 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2018-10-17
+- Pulled out of the Rand crate
diff --git a/rand/rand_hc/COPYRIGHT b/rand/rand_hc/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_hc/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_hc/Cargo.toml b/rand/rand_hc/Cargo.toml
new file mode 100644
index 0000000..ed5dd5b
--- /dev/null
+++ b/rand/rand_hc/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+name = "rand_hc"
+version = "0.1.0"
+authors = ["The Rand Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_hc"
+homepage = "https://crates.io/crates/rand_hc"
+description = """
+HC128 random number generator
+"""
+keywords = ["random", "rng", "hc128"]
+categories = ["algorithms", "no-std"]
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[dependencies]
+rand_core = { path = "../rand_core", version = ">=0.2, <0.4", default-features=false }
diff --git a/rand/rand_hc/LICENSE-APACHE b/rand/rand_hc/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_hc/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
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+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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diff --git a/rand/rand_hc/LICENSE-MIT b/rand/rand_hc/LICENSE-MIT
new file mode 100644
index 0000000..cf65607
--- /dev/null
+++ b/rand/rand_hc/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright 2018 Developers of the Rand project
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_hc/README.md b/rand/rand_hc/README.md
new file mode 100644
index 0000000..178548a
--- /dev/null
+++ b/rand/rand_hc/README.md
@@ -0,0 +1,45 @@
+# rand_hc
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_hc.svg)](https://crates.io/crates/rand_hc)
+[[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_hc)
+[![API](https://docs.rs/rand_hc/badge.svg)](https://docs.rs/rand_hc)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+A cryptographically secure random number generator that uses the HC-128
+algorithm.
+
+HC-128 is a stream cipher designed by Hongjun Wu[^1], that we use as an
+RNG. It is selected as one of the "stream ciphers suitable for widespread
+adoption" by eSTREAM[^2].
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_hc)
+-   [API documentation (docs.rs)](https://docs.rs/rand_hc)
+-   [Changelog](CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+[^1]: Hongjun Wu (2008). ["The Stream Cipher HC-128"](
+      http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf).
+      *The eSTREAM Finalists*, LNCS 4986, pp. 39–47, Springer-Verlag.
+
+[^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+      http://www.ecrypt.eu.org/stream/)
+
+
+## Crate Features
+
+`rand_hc` is `no_std` compatible. It does not require any functionality
+outside of the `core` lib, thus there are no features to configure.
+
+
+# License
+
+`rand_hc` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_hc/src/hc128.rs b/rand/rand_hc/src/hc128.rs
new file mode 100644
index 0000000..d1dadcc
--- /dev/null
+++ b/rand/rand_hc/src/hc128.rs
@@ -0,0 +1,462 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The HC-128 random number generator.
+
+use core::fmt;
+use rand_core::{CryptoRng, RngCore, SeedableRng, Error, le};
+use rand_core::block::{BlockRngCore, BlockRng};
+
+const SEED_WORDS: usize = 8; // 128 bit key followed by 128 bit iv
+
+/// A cryptographically secure random number generator that uses the HC-128
+/// algorithm.
+///
+/// HC-128 is a stream cipher designed by Hongjun Wu[^1], that we use as an
+/// RNG. It is selected as one of the "stream ciphers suitable for widespread
+/// adoption" by eSTREAM[^2].
+///
+/// HC-128 is an array based RNG. In this it is similar to RC-4 and ISAAC before
+/// it, but those have never been proven cryptographically secure (or have even
+/// been significantly compromised, as in the case of RC-4[^5]).
+///
+/// Because HC-128 works with simple indexing into a large array and with a few
+/// operations that parallelize well, it has very good performance. The size of
+/// the array it needs, 4kb, can however be a disadvantage.
+///
+/// This implementation is not based on the version of HC-128 submitted to the
+/// eSTREAM contest, but on a later version by the author with a few small
+/// improvements from December 15, 2009[^3].
+///
+/// HC-128 has no known weaknesses that are easier to exploit than doing a
+/// brute-force search of 2<sup>128</sup>. A very comprehensive analysis of the
+/// current state of known attacks / weaknesses of HC-128 is given in *Some
+/// Results On Analysis And Implementation Of HC-128 Stream Cipher*[^4].
+///
+/// The average cycle length is expected to be
+/// 2<sup>1024*32+10-1</sup> = 2<sup>32777</sup>.
+/// We support seeding with a 256-bit array, which matches the 128-bit key
+/// concatenated with a 128-bit IV from the stream cipher.
+///
+/// This implementation uses an output buffer of sixteen `u32` words, and uses
+/// [`BlockRng`] to implement the [`RngCore`] methods.
+///
+/// ## References
+/// [^1]: Hongjun Wu (2008). ["The Stream Cipher HC-128"](
+///       http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf).
+///       *The eSTREAM Finalists*, LNCS 4986, pp. 39–47, Springer-Verlag.
+///
+/// [^2]: [eSTREAM: the ECRYPT Stream Cipher Project](
+///       http://www.ecrypt.eu.org/stream/)
+///
+/// [^3]: Hongjun Wu, [Stream Ciphers HC-128 and HC-256](
+///       https://www.ntu.edu.sg/home/wuhj/research/hc/index.html)
+///
+/// [^4]: Shashwat Raizada (January 2015),["Some Results On Analysis And
+///       Implementation Of HC-128 Stream Cipher"](
+///       http://library.isical.ac.in:8080/jspui/bitstream/123456789/6636/1/TH431.pdf).
+///
+/// [^5]: Internet Engineering Task Force (February 2015),
+///       ["Prohibiting RC4 Cipher Suites"](https://tools.ietf.org/html/rfc7465).
+///
+/// [`BlockRng`]: ../rand_core/block/struct.BlockRng.html
+/// [`RngCore`]: ../rand_core/trait.RngCore.html
+#[derive(Clone, Debug)]
+pub struct Hc128Rng(BlockRng<Hc128Core>);
+
+impl RngCore for Hc128Rng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for Hc128Rng {
+    type Seed = <Hc128Core as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Hc128Rng(BlockRng::<Hc128Core>::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        BlockRng::<Hc128Core>::from_rng(rng).map(Hc128Rng)
+    }
+}
+
+impl CryptoRng for Hc128Rng {}
+
+/// The core of `Hc128Rng`, used with `BlockRng`.
+#[derive(Clone)]
+pub struct Hc128Core {
+    t: [u32; 1024],
+    counter1024: usize,
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for Hc128Core {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Hc128Core {{}}")
+    }
+}
+
+impl BlockRngCore for Hc128Core {
+    type Item = u32;
+    type Results = [u32; 16];
+
+    fn generate(&mut self, results: &mut Self::Results) {
+        assert!(self.counter1024 % 16 == 0);
+
+        let cc = self.counter1024 % 512;
+        let dd = (cc + 16) % 512;
+        let ee = cc.wrapping_sub(16) % 512;
+
+        if self.counter1024 & 512 == 0 {
+            // P block
+            results[0]  = self.step_p(cc+0,  cc+1,  ee+13, ee+6,  ee+4);
+            results[1]  = self.step_p(cc+1,  cc+2,  ee+14, ee+7,  ee+5);
+            results[2]  = self.step_p(cc+2,  cc+3,  ee+15, ee+8,  ee+6);
+            results[3]  = self.step_p(cc+3,  cc+4,  cc+0,  ee+9,  ee+7);
+            results[4]  = self.step_p(cc+4,  cc+5,  cc+1,  ee+10, ee+8);
+            results[5]  = self.step_p(cc+5,  cc+6,  cc+2,  ee+11, ee+9);
+            results[6]  = self.step_p(cc+6,  cc+7,  cc+3,  ee+12, ee+10);
+            results[7]  = self.step_p(cc+7,  cc+8,  cc+4,  ee+13, ee+11);
+            results[8]  = self.step_p(cc+8,  cc+9,  cc+5,  ee+14, ee+12);
+            results[9]  = self.step_p(cc+9,  cc+10, cc+6,  ee+15, ee+13);
+            results[10] = self.step_p(cc+10, cc+11, cc+7,  cc+0,  ee+14);
+            results[11] = self.step_p(cc+11, cc+12, cc+8,  cc+1,  ee+15);
+            results[12] = self.step_p(cc+12, cc+13, cc+9,  cc+2,  cc+0);
+            results[13] = self.step_p(cc+13, cc+14, cc+10, cc+3,  cc+1);
+            results[14] = self.step_p(cc+14, cc+15, cc+11, cc+4,  cc+2);
+            results[15] = self.step_p(cc+15, dd+0,  cc+12, cc+5,  cc+3);
+        } else {
+            // Q block
+            results[0]  = self.step_q(cc+0,  cc+1,  ee+13, ee+6,  ee+4);
+            results[1]  = self.step_q(cc+1,  cc+2,  ee+14, ee+7,  ee+5);
+            results[2]  = self.step_q(cc+2,  cc+3,  ee+15, ee+8,  ee+6);
+            results[3]  = self.step_q(cc+3,  cc+4,  cc+0,  ee+9,  ee+7);
+            results[4]  = self.step_q(cc+4,  cc+5,  cc+1,  ee+10, ee+8);
+            results[5]  = self.step_q(cc+5,  cc+6,  cc+2,  ee+11, ee+9);
+            results[6]  = self.step_q(cc+6,  cc+7,  cc+3,  ee+12, ee+10);
+            results[7]  = self.step_q(cc+7,  cc+8,  cc+4,  ee+13, ee+11);
+            results[8]  = self.step_q(cc+8,  cc+9,  cc+5,  ee+14, ee+12);
+            results[9]  = self.step_q(cc+9,  cc+10, cc+6,  ee+15, ee+13);
+            results[10] = self.step_q(cc+10, cc+11, cc+7,  cc+0,  ee+14);
+            results[11] = self.step_q(cc+11, cc+12, cc+8,  cc+1,  ee+15);
+            results[12] = self.step_q(cc+12, cc+13, cc+9,  cc+2,  cc+0);
+            results[13] = self.step_q(cc+13, cc+14, cc+10, cc+3,  cc+1);
+            results[14] = self.step_q(cc+14, cc+15, cc+11, cc+4,  cc+2);
+            results[15] = self.step_q(cc+15, dd+0,  cc+12, cc+5,  cc+3);
+        }
+        self.counter1024 = self.counter1024.wrapping_add(16);
+    }
+}
+
+impl Hc128Core {
+    // One step of HC-128, update P and generate 32 bits keystream
+    #[inline(always)]
+    fn step_p(&mut self, i: usize, i511: usize, i3: usize, i10: usize, i12: usize)
+         -> u32
+    {
+        let (p, q) = self.t.split_at_mut(512);
+        // FIXME: it would be great if we the bounds checks here could be
+        // optimized out, and we would not need unsafe.
+        // This improves performance by about 7%.
+        unsafe {
+            let temp0 = p.get_unchecked(i511).rotate_right(23);
+            let temp1 = p.get_unchecked(i3).rotate_right(10);
+            let temp2 = p.get_unchecked(i10).rotate_right(8);
+            *p.get_unchecked_mut(i) = p.get_unchecked(i)
+                                       .wrapping_add(temp2)
+                                       .wrapping_add(temp0 ^ temp1);
+            let temp3 = {
+                // The h1 function in HC-128
+                let a = *p.get_unchecked(i12) as u8;
+                let c = (p.get_unchecked(i12) >> 16) as u8;
+                q[a as usize].wrapping_add(q[256 + c as usize])
+            };
+            temp3 ^ p.get_unchecked(i)
+        }
+    }
+
+    // One step of HC-128, update Q and generate 32 bits keystream
+    // Similar to `step_p`, but `p` and `q` are swapped, and the rotates are to
+    // the left instead of to the right.
+    #[inline(always)]
+    fn step_q(&mut self, i: usize, i511: usize, i3: usize, i10: usize, i12: usize)
+         -> u32
+    {
+        let (p, q) = self.t.split_at_mut(512);
+        unsafe {
+            let temp0 = q.get_unchecked(i511).rotate_left(23);
+            let temp1 = q.get_unchecked(i3).rotate_left(10);
+            let temp2 = q.get_unchecked(i10).rotate_left(8);
+            *q.get_unchecked_mut(i) = q.get_unchecked(i)
+                                       .wrapping_add(temp2)
+                                       .wrapping_add(temp0 ^ temp1);
+            let temp3 = {
+                // The h2 function in HC-128
+                let a = *q.get_unchecked(i12) as u8;
+                let c = (q.get_unchecked(i12) >> 16) as u8;
+                p[a as usize].wrapping_add(p[256 + c as usize])
+            };
+            temp3 ^ q.get_unchecked(i)
+        }
+    }
+
+    fn sixteen_steps(&mut self) {
+        assert!(self.counter1024 % 16 == 0);
+
+        let cc = self.counter1024 % 512;
+        let dd = (cc + 16) % 512;
+        let ee = cc.wrapping_sub(16) % 512;
+
+        if self.counter1024 < 512 {
+            // P block
+            self.t[cc+0]  = self.step_p(cc+0,  cc+1,  ee+13, ee+6,  ee+4);
+            self.t[cc+1]  = self.step_p(cc+1,  cc+2,  ee+14, ee+7,  ee+5);
+            self.t[cc+2]  = self.step_p(cc+2,  cc+3,  ee+15, ee+8,  ee+6);
+            self.t[cc+3]  = self.step_p(cc+3,  cc+4,  cc+0,  ee+9,  ee+7);
+            self.t[cc+4]  = self.step_p(cc+4,  cc+5,  cc+1,  ee+10, ee+8);
+            self.t[cc+5]  = self.step_p(cc+5,  cc+6,  cc+2,  ee+11, ee+9);
+            self.t[cc+6]  = self.step_p(cc+6,  cc+7,  cc+3,  ee+12, ee+10);
+            self.t[cc+7]  = self.step_p(cc+7,  cc+8,  cc+4,  ee+13, ee+11);
+            self.t[cc+8]  = self.step_p(cc+8,  cc+9,  cc+5,  ee+14, ee+12);
+            self.t[cc+9]  = self.step_p(cc+9,  cc+10, cc+6,  ee+15, ee+13);
+            self.t[cc+10] = self.step_p(cc+10, cc+11, cc+7,  cc+0,  ee+14);
+            self.t[cc+11] = self.step_p(cc+11, cc+12, cc+8,  cc+1,  ee+15);
+            self.t[cc+12] = self.step_p(cc+12, cc+13, cc+9,  cc+2,  cc+0);
+            self.t[cc+13] = self.step_p(cc+13, cc+14, cc+10, cc+3,  cc+1);
+            self.t[cc+14] = self.step_p(cc+14, cc+15, cc+11, cc+4,  cc+2);
+            self.t[cc+15] = self.step_p(cc+15, dd+0,  cc+12, cc+5,  cc+3);
+        } else {
+            // Q block
+            self.t[cc+512+0]  = self.step_q(cc+0,  cc+1,  ee+13, ee+6,  ee+4);
+            self.t[cc+512+1]  = self.step_q(cc+1,  cc+2,  ee+14, ee+7,  ee+5);
+            self.t[cc+512+2]  = self.step_q(cc+2,  cc+3,  ee+15, ee+8,  ee+6);
+            self.t[cc+512+3]  = self.step_q(cc+3,  cc+4,  cc+0,  ee+9,  ee+7);
+            self.t[cc+512+4]  = self.step_q(cc+4,  cc+5,  cc+1,  ee+10, ee+8);
+            self.t[cc+512+5]  = self.step_q(cc+5,  cc+6,  cc+2,  ee+11, ee+9);
+            self.t[cc+512+6]  = self.step_q(cc+6,  cc+7,  cc+3,  ee+12, ee+10);
+            self.t[cc+512+7]  = self.step_q(cc+7,  cc+8,  cc+4,  ee+13, ee+11);
+            self.t[cc+512+8]  = self.step_q(cc+8,  cc+9,  cc+5,  ee+14, ee+12);
+            self.t[cc+512+9]  = self.step_q(cc+9,  cc+10, cc+6,  ee+15, ee+13);
+            self.t[cc+512+10] = self.step_q(cc+10, cc+11, cc+7,  cc+0,  ee+14);
+            self.t[cc+512+11] = self.step_q(cc+11, cc+12, cc+8,  cc+1,  ee+15);
+            self.t[cc+512+12] = self.step_q(cc+12, cc+13, cc+9,  cc+2,  cc+0);
+            self.t[cc+512+13] = self.step_q(cc+13, cc+14, cc+10, cc+3,  cc+1);
+            self.t[cc+512+14] = self.step_q(cc+14, cc+15, cc+11, cc+4,  cc+2);
+            self.t[cc+512+15] = self.step_q(cc+15, dd+0,  cc+12, cc+5,  cc+3);
+        }
+        self.counter1024 += 16;
+    }
+
+    // Initialize an HC-128 random number generator. The seed has to be
+    // 256 bits in length (`[u32; 8]`), matching the 128 bit `key` followed by
+    // 128 bit `iv` when HC-128 where to be used as a stream cipher.
+    fn init(seed: [u32; SEED_WORDS]) -> Self {
+        #[inline]
+        fn f1(x: u32) -> u32 {
+            x.rotate_right(7) ^ x.rotate_right(18) ^ (x >> 3)
+        }
+
+        #[inline]
+        fn f2(x: u32) -> u32 {
+            x.rotate_right(17) ^ x.rotate_right(19) ^ (x >> 10)
+        }
+
+        let mut t = [0u32; 1024];
+
+        // Expand the key and iv into P and Q
+        let (key, iv) = seed.split_at(4);
+        t[..4].copy_from_slice(key);
+        t[4..8].copy_from_slice(key);
+        t[8..12].copy_from_slice(iv);
+        t[12..16].copy_from_slice(iv);
+
+        // Generate the 256 intermediate values W[16] ... W[256+16-1], and
+        // copy the last 16 generated values to the start op P.
+        for i in 16..256+16 {
+            t[i] = f2(t[i-2]).wrapping_add(t[i-7]).wrapping_add(f1(t[i-15]))
+                   .wrapping_add(t[i-16]).wrapping_add(i as u32);
+        }
+        {
+            let (p1, p2) = t.split_at_mut(256);
+            p1[0..16].copy_from_slice(&p2[0..16]);
+        }
+
+        // Generate both the P and Q tables
+        for i in 16..1024 {
+            t[i] = f2(t[i-2]).wrapping_add(t[i-7]).wrapping_add(f1(t[i-15]))
+                   .wrapping_add(t[i-16]).wrapping_add(256 + i as u32);
+        }
+
+        let mut core = Self { t, counter1024: 0 };
+
+        // run the cipher 1024 steps
+        for _ in 0..64 { core.sixteen_steps() };
+        core.counter1024 = 0;
+        core
+    }
+}
+
+impl SeedableRng for Hc128Core {
+    type Seed = [u8; SEED_WORDS*4];
+
+    /// Create an HC-128 random number generator with a seed. The seed has to be
+    /// 256 bits in length, matching the 128 bit `key` followed by 128 bit `iv`
+    /// when HC-128 where to be used as a stream cipher.
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_u32 = [0u32; SEED_WORDS];
+        le::read_u32_into(&seed, &mut seed_u32);
+        Self::init(seed_u32)
+    }
+}
+
+impl CryptoRng for Hc128Core {}
+
+#[cfg(test)]
+mod test {
+    use ::rand_core::{RngCore, SeedableRng};
+    use super::Hc128Rng;
+
+    #[test]
+    // Test vector 1 from the paper "The Stream Cipher HC-128"
+    fn test_hc128_true_values_a() {
+        let seed = [0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng = Hc128Rng::from_seed(seed);
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0x73150082, 0x3bfd03a0, 0xfb2fd77f, 0xaa63af0e,
+                        0xde122fc6, 0xa7dc29b6, 0x62a68527, 0x8b75ec68,
+                        0x9036db1e, 0x81896005, 0x00ade078, 0x491fbf9a,
+                        0x1cdc3013, 0x6c3d6e24, 0x90f664b2, 0x9cd57102];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    // Test vector 2 from the paper "The Stream Cipher HC-128"
+    fn test_hc128_true_values_b() {
+        let seed = [0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    1,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng = Hc128Rng::from_seed(seed);
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0xc01893d5, 0xb7dbe958, 0x8f65ec98, 0x64176604,
+                        0x36fc6724, 0xc82c6eec, 0x1b1c38a7, 0xc9b42a95,
+                        0x323ef123, 0x0a6a908b, 0xce757b68, 0x9f14f7bb,
+                        0xe4cde011, 0xaeb5173f, 0x89608c94, 0xb5cf46ca];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    // Test vector 3 from the paper "The Stream Cipher HC-128"
+    fn test_hc128_true_values_c() {
+        let seed = [0x55,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng = Hc128Rng::from_seed(seed);
+
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected = [0x518251a4, 0x04b4930a, 0xb02af931, 0x0639f032,
+                        0xbcb4a47a, 0x5722480b, 0x2bf99f72, 0xcdc0e566,
+                        0x310f0c56, 0xd3cc83e8, 0x663db8ef, 0x62dfe07f,
+                        0x593e1790, 0xc5ceaa9c, 0xab03806f, 0xc9a6e5a0];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_hc128_true_values_u64() {
+        let seed = [0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng = Hc128Rng::from_seed(seed);
+
+        let mut results = [0u64; 8];
+        for i in results.iter_mut() { *i = rng.next_u64(); }
+        let expected = [0x3bfd03a073150082, 0xaa63af0efb2fd77f,
+                        0xa7dc29b6de122fc6, 0x8b75ec6862a68527,
+                        0x818960059036db1e, 0x491fbf9a00ade078,
+                        0x6c3d6e241cdc3013, 0x9cd5710290f664b2];
+        assert_eq!(results, expected);
+
+        // The RNG operates in a P block of 512 results and next a Q block.
+        // After skipping 2*800 u32 results we end up somewhere in the Q block
+        // of the second round
+        for _ in 0..800 { rng.next_u64(); }
+
+        for i in results.iter_mut() { *i = rng.next_u64(); }
+        let expected = [0xd8c4d6ca84d0fc10, 0xf16a5d91dc66e8e7,
+                        0xd800de5bc37a8653, 0x7bae1f88c0dfbb4c,
+                        0x3bfe1f374e6d4d14, 0x424b55676be3fa06,
+                        0xe3a1e8758cbff579, 0x417f7198c5652bcd];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_hc128_true_values_bytes() {
+        let seed = [0x55,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng = Hc128Rng::from_seed(seed);
+        let expected = [0x31, 0xf9, 0x2a, 0xb0, 0x32, 0xf0, 0x39, 0x06,
+                 0x7a, 0xa4, 0xb4, 0xbc, 0x0b, 0x48, 0x22, 0x57,
+                 0x72, 0x9f, 0xf9, 0x2b, 0x66, 0xe5, 0xc0, 0xcd,
+                 0x56, 0x0c, 0x0f, 0x31, 0xe8, 0x83, 0xcc, 0xd3,
+                 0xef, 0xb8, 0x3d, 0x66, 0x7f, 0xe0, 0xdf, 0x62,
+                 0x90, 0x17, 0x3e, 0x59, 0x9c, 0xaa, 0xce, 0xc5,
+                 0x6f, 0x80, 0x03, 0xab, 0xa0, 0xe5, 0xa6, 0xc9,
+                 0x60, 0x95, 0x84, 0x7a, 0xa5, 0x68, 0x5a, 0x84,
+                 0xea, 0xd5, 0xf3, 0xea, 0x73, 0xa9, 0xad, 0x01,
+                 0x79, 0x7d, 0xbe, 0x9f, 0xea, 0xe3, 0xf9, 0x74,
+                 0x0e, 0xda, 0x2f, 0xa0, 0xe4, 0x7b, 0x4b, 0x1b,
+                 0xdd, 0x17, 0x69, 0x4a, 0xfe, 0x9f, 0x56, 0x95,
+                 0xad, 0x83, 0x6b, 0x9d, 0x60, 0xa1, 0x99, 0x96,
+                 0x90, 0x00, 0x66, 0x7f, 0xfa, 0x7e, 0x65, 0xe9,
+                 0xac, 0x8b, 0x92, 0x34, 0x77, 0xb4, 0x23, 0xd0,
+                 0xb9, 0xab, 0xb1, 0x47, 0x7d, 0x4a, 0x13, 0x0a];
+
+        // Pick a somewhat large buffer so we can test filling with the
+        // remainder from `state.results`, directly filling the buffer, and
+        // filling the remainder of the buffer.
+        let mut buffer = [0u8; 16*4*2];
+        // Consume a value so that we have a remainder.
+        assert!(rng.next_u64() == 0x04b4930a518251a4);
+        rng.fill_bytes(&mut buffer);
+
+        // [u8; 128] doesn't implement PartialEq
+        assert_eq!(buffer.len(), expected.len());
+        for (b, e) in buffer.iter().zip(expected.iter()) {
+            assert_eq!(b, e);
+        }
+    }
+
+    #[test]
+    fn test_hc128_clone() {
+        let seed = [0x55,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0, // key
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0]; // iv
+        let mut rng1 = Hc128Rng::from_seed(seed);
+        let mut rng2 = rng1.clone();
+        for _ in 0..16 {
+            assert_eq!(rng1.next_u32(), rng2.next_u32());
+        }
+    }
+}
diff --git a/rand/rand_hc/src/lib.rs b/rand/rand_hc/src/lib.rs
new file mode 100644
index 0000000..f1d772d
--- /dev/null
+++ b/rand/rand_hc/src/lib.rs
@@ -0,0 +1,25 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The HC128 random number generator.
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
+
+#![no_std]
+
+extern crate rand_core;
+
+mod hc128;
+
+pub use hc128::{Hc128Rng, Hc128Core};
diff --git a/rand/rand_isaac/CHANGELOG.md b/rand/rand_isaac/CHANGELOG.md
new file mode 100644
index 0000000..d0c4a2f
--- /dev/null
+++ b/rand/rand_isaac/CHANGELOG.md
@@ -0,0 +1,8 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2018-10-17
+- Pulled out of the Rand crate
diff --git a/rand/rand_isaac/COPYRIGHT b/rand/rand_isaac/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_isaac/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_isaac/Cargo.toml b/rand/rand_isaac/Cargo.toml
new file mode 100644
index 0000000..07c4a36
--- /dev/null
+++ b/rand/rand_isaac/Cargo.toml
@@ -0,0 +1,31 @@
+[package]
+name = "rand_isaac"
+version = "0.1.0"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_isaac"
+homepage = "https://crates.io/crates/rand_isaac"
+description = """
+ISAAC random number generator
+"""
+keywords = ["random", "rng", "isaac"]
+categories = ["algorithms", "no-std"]
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[features]
+serde1 = ["serde", "serde_derive", "rand_core/serde1"]
+
+[dependencies]
+rand_core = { path = "../rand_core", version = ">=0.2, <0.4", default-features=false }
+serde = { version = "1", optional = true }
+serde_derive = { version = "^1.0.38", optional = true }
+
+[dev-dependencies]
+# This is for testing serde, unfortunately we can't specify feature-gated dev
+# deps yet, see: https://github.com/rust-lang/cargo/issues/1596
+bincode = "1"
diff --git a/rand/rand_isaac/LICENSE-APACHE b/rand/rand_isaac/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_isaac/LICENSE-APACHE
@@ -0,0 +1,201 @@
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diff --git a/rand/rand_isaac/LICENSE-MIT b/rand/rand_isaac/LICENSE-MIT
new file mode 100644
index 0000000..d93b5ba
--- /dev/null
+++ b/rand/rand_isaac/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright 2018 Developers of the Rand project
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_isaac/README.md b/rand/rand_isaac/README.md
new file mode 100644
index 0000000..02d1230
--- /dev/null
+++ b/rand/rand_isaac/README.md
@@ -0,0 +1,47 @@
+# rand_isaac
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_isaac.svg)](https://crates.io/crates/rand_isaac)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_isaac)
+[![API](https://docs.rs/rand_isaac/badge.svg)](https://docs.rs/rand_isaac)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+Implements the ISAAC and ISAAC-64 random number generators.
+
+ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are
+the principal bitwise operations employed. It is the most advanced of a
+series of array based random number generator designed by Robert Jenkins
+in 1996[^1][^2].
+
+ISAAC is notably fast and produces excellent quality random numbers for
+non-cryptographic applications.
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_isaac)
+-   [API documentation (docs.rs)](https://docs.rs/rand_isaac)
+-   [Changelog](CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+[^1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number generator*](http://burtleburtle.net/bob/rand/isaacafa.html)
+[^2]: Bob Jenkins, [*ISAAC and RC4*](http://burtleburtle.net/bob/rand/isaac.html)
+
+
+## Crate Features
+
+`rand_isaac` is `no_std` compatible. It does not require any functionality
+outside of the `core` lib, thus there are no features to configure.
+
+The `serde1` feature includes implementations of `Serialize` and `Deserialize`
+for the included RNGs.
+
+
+# License
+
+`rand_isaac` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_isaac/src/isaac.rs b/rand/rand_isaac/src/isaac.rs
new file mode 100644
index 0000000..2bfdd94
--- /dev/null
+++ b/rand/rand_isaac/src/isaac.rs
@@ -0,0 +1,484 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The ISAAC random number generator.
+
+use core::{fmt, slice};
+use core::num::Wrapping as w;
+use rand_core::{RngCore, SeedableRng, Error, le};
+use rand_core::block::{BlockRngCore, BlockRng};
+use isaac_array::IsaacArray;
+
+#[allow(non_camel_case_types)]
+type w32 = w<u32>;
+
+const RAND_SIZE_LEN: usize = 8;
+const RAND_SIZE: usize = 1 << RAND_SIZE_LEN;
+
+/// A random number generator that uses the ISAAC algorithm.
+///
+/// ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are
+/// the principal bitwise operations employed. It is the most advanced of a
+/// series of array based random number generator designed by Robert Jenkins
+/// in 1996[^1][^2].
+///
+/// ISAAC is notably fast and produces excellent quality random numbers for
+/// non-cryptographic applications.
+///
+/// In spite of being designed with cryptographic security in mind, ISAAC hasn't
+/// been stringently cryptanalyzed and thus cryptographers do not not
+/// consensually trust it to be secure. When looking for a secure RNG, prefer
+/// [`Hc128Rng`] instead, which, like ISAAC, is an array-based RNG and one of
+/// the stream-ciphers selected the by eSTREAM contest.
+///
+/// In 2006 an improvement to ISAAC was suggested by Jean-Philippe Aumasson,
+/// named ISAAC+[^3]. But because the specification is not complete, because
+/// there is no good implementation, and because the suggested bias may not
+/// exist, it is not implemented here.
+///
+/// ## Overview of the ISAAC algorithm:
+/// (in pseudo-code)
+///
+/// ```text
+/// Input: a, b, c, s[256] // state
+/// Output: r[256]         // results
+///
+/// mix(a,i) = a ^ a << 13   if i = 0 mod 4
+///            a ^ a >>  6   if i = 1 mod 4
+///            a ^ a <<  2   if i = 2 mod 4
+///            a ^ a >> 16   if i = 3 mod 4
+///
+/// c = c + 1
+/// b = b + c
+///
+/// for i in 0..256 {
+///     x = s_[i]
+///     a = f(a,i) + s[i+128 mod 256]
+///     y = a + b + s[x>>2 mod 256]
+///     s[i] = y
+///     b = x + s[y>>10 mod 256]
+///     r[i] = b
+/// }
+/// ```
+///
+/// Numbers are generated in blocks of 256. This means the function above only
+/// runs once every 256 times you ask for a next random number. In all other
+/// circumstances the last element of the results array is returned.
+///
+/// ISAAC therefore needs a lot of memory, relative to other non-crypto RNGs.
+/// 2 * 256 * 4 = 2 kb to hold the state and results.
+///
+/// This implementation uses [`BlockRng`] to implement the [`RngCore`] methods.
+///
+/// ## References
+/// [^1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number generator*](
+///       http://burtleburtle.net/bob/rand/isaacafa.html)
+///
+/// [^2]: Bob Jenkins, [*ISAAC and RC4*](
+///       http://burtleburtle.net/bob/rand/isaac.html)
+///
+/// [^3]: Jean-Philippe Aumasson, [*On the pseudo-random generator ISAAC*](
+///       https://eprint.iacr.org/2006/438)
+///
+/// [`Hc128Rng`]: ../../rand_hc/struct.Hc128Rng.html
+/// [`BlockRng`]: ../../rand_core/block/struct.BlockRng.html
+/// [`RngCore`]: ../../rand_core/trait.RngCore.html
+#[derive(Clone, Debug)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct IsaacRng(BlockRng<IsaacCore>);
+
+impl RngCore for IsaacRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for IsaacRng {
+    type Seed = <IsaacCore as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        IsaacRng(BlockRng::<IsaacCore>::from_seed(seed))
+    }
+    
+    /// Create an ISAAC random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    fn seed_from_u64(seed: u64) -> Self {
+        IsaacRng(BlockRng::<IsaacCore>::seed_from_u64(seed))
+    }
+
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        BlockRng::<IsaacCore>::from_rng(rng).map(|rng| IsaacRng(rng))
+    }
+}
+
+impl IsaacRng {
+    /// Create an ISAAC random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    #[deprecated(since="0.6.0", note="use SeedableRng::seed_from_u64 instead")]
+    pub fn new_from_u64(seed: u64) -> Self {
+        Self::seed_from_u64(seed)
+    }
+}
+
+/// The core of `IsaacRng`, used with `BlockRng`.
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct IsaacCore {
+    #[cfg_attr(feature="serde1",serde(with="super::isaac_array::isaac_array_serde"))]
+    mem: [w32; RAND_SIZE],
+    a: w32,
+    b: w32,
+    c: w32,
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for IsaacCore {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "IsaacCore {{}}")
+    }
+}
+
+impl BlockRngCore for IsaacCore {
+    type Item = u32;
+    type Results = IsaacArray<Self::Item>;
+
+    /// Refills the output buffer, `results`. See also the pseudocode desciption
+    /// of the algorithm in the [`IsaacRng`] documentation.
+    ///
+    /// Optimisations used (similar to the reference implementation):
+    /// 
+    /// - The loop is unrolled 4 times, once for every constant of mix().
+    /// - The contents of the main loop are moved to a function `rngstep`, to
+    ///   reduce code duplication.
+    /// - We use local variables for a and b, which helps with optimisations.
+    /// - We split the main loop in two, one that operates over 0..128 and one
+    ///   over 128..256. This way we can optimise out the addition and modulus
+    ///   from `s[i+128 mod 256]`.
+    /// - We maintain one index `i` and add `m` or `m2` as base (m2 for the
+    ///   `s[i+128 mod 256]`), relying on the optimizer to turn it into pointer
+    ///   arithmetic.
+    /// - We fill `results` backwards. The reference implementation reads values
+    ///   from `results` in reverse. We read them in the normal direction, to
+    ///   make `fill_bytes` a memcopy. To maintain compatibility we fill in
+    ///   reverse.
+    /// 
+    /// [`IsaacRng`]: struct.IsaacRng.html
+    fn generate(&mut self, results: &mut IsaacArray<Self::Item>) {
+        self.c += w(1);
+        // abbreviations
+        let mut a = self.a;
+        let mut b = self.b + self.c;
+        const MIDPOINT: usize = RAND_SIZE / 2;
+
+        #[inline]
+        fn ind(mem:&[w32; RAND_SIZE], v: w32, amount: usize) -> w32 {
+            let index = (v >> amount).0 as usize % RAND_SIZE;
+            mem[index]
+        }
+
+        #[inline]
+        fn rngstep(mem: &mut [w32; RAND_SIZE],
+                   results: &mut [u32; RAND_SIZE],
+                   mix: w32,
+                   a: &mut w32,
+                   b: &mut w32,
+                   base: usize,
+                   m: usize,
+                   m2: usize) {
+            let x = mem[base + m];
+            *a = mix + mem[base + m2];
+            let y = *a + *b + ind(&mem, x, 2);
+            mem[base + m] = y;
+            *b = x + ind(&mem, y, 2 + RAND_SIZE_LEN);
+            results[RAND_SIZE - 1 - base - m] = (*b).0;
+        }
+
+        let mut m = 0;
+        let mut m2 = MIDPOINT;
+        for i in (0..MIDPOINT/4).map(|i| i * 4) {
+            rngstep(&mut self.mem, results, a ^ (a << 13), &mut a, &mut b, i + 0, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a >> 6 ),  &mut a, &mut b, i + 1, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a << 2 ),  &mut a, &mut b, i + 2, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a >> 16),  &mut a, &mut b, i + 3, m, m2);
+        }
+
+        m = MIDPOINT;
+        m2 = 0;
+        for i in (0..MIDPOINT/4).map(|i| i * 4) {
+            rngstep(&mut self.mem, results, a ^ (a << 13), &mut a, &mut b, i + 0, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a >> 6 ),  &mut a, &mut b, i + 1, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a << 2 ),  &mut a, &mut b, i + 2, m, m2);
+            rngstep(&mut self.mem, results, a ^ (a >> 16),  &mut a, &mut b, i + 3, m, m2);
+        }
+
+        self.a = a;
+        self.b = b;
+    }
+}
+
+impl IsaacCore {
+    /// Create a new ISAAC random number generator.
+    ///
+    /// The author Bob Jenkins describes how to best initialize ISAAC here:
+    /// <https://rt.cpan.org/Public/Bug/Display.html?id=64324>
+    /// The answer is included here just in case:
+    ///
+    /// "No, you don't need a full 8192 bits of seed data. Normal key sizes will
+    /// do fine, and they should have their expected strength (eg a 40-bit key
+    /// will take as much time to brute force as 40-bit keys usually will). You
+    /// could fill the remainder with 0, but set the last array element to the
+    /// length of the key provided (to distinguish keys that differ only by
+    /// different amounts of 0 padding). You do still need to call `randinit()`
+    /// to make sure the initial state isn't uniform-looking."
+    /// "After publishing ISAAC, I wanted to limit the key to half the size of
+    /// `r[]`, and repeat it twice. That would have made it hard to provide a
+    /// key that sets the whole internal state to anything convenient. But I'd
+    /// already published it."
+    ///
+    /// And his answer to the question "For my code, would repeating the key
+    /// over and over to fill 256 integers be a better solution than
+    /// zero-filling, or would they essentially be the same?":
+    /// "If the seed is under 32 bytes, they're essentially the same, otherwise
+    /// repeating the seed would be stronger. randinit() takes a chunk of 32
+    /// bytes, mixes it, and combines that with the next 32 bytes, et cetera.
+    /// Then loops over all the elements the same way a second time."
+    #[inline]
+    fn init(mut mem: [w32; RAND_SIZE], rounds: u32) -> Self {
+        fn mix(a: &mut w32, b: &mut w32, c: &mut w32, d: &mut w32,
+               e: &mut w32, f: &mut w32, g: &mut w32, h: &mut w32) {
+            *a ^= *b << 11; *d += *a; *b += *c;
+            *b ^= *c >> 2;  *e += *b; *c += *d;
+            *c ^= *d << 8;  *f += *c; *d += *e;
+            *d ^= *e >> 16; *g += *d; *e += *f;
+            *e ^= *f << 10; *h += *e; *f += *g;
+            *f ^= *g >> 4;  *a += *f; *g += *h;
+            *g ^= *h << 8;  *b += *g; *h += *a;
+            *h ^= *a >> 9;  *c += *h; *a += *b;
+        }
+
+        // These numbers are the result of initializing a...h with the
+        // fractional part of the golden ratio in binary (0x9e3779b9)
+        // and applying mix() 4 times.
+        let mut a = w(0x1367df5a);
+        let mut b = w(0x95d90059);
+        let mut c = w(0xc3163e4b);
+        let mut d = w(0x0f421ad8);
+        let mut e = w(0xd92a4a78);
+        let mut f = w(0xa51a3c49);
+        let mut g = w(0xc4efea1b);
+        let mut h = w(0x30609119);
+
+        // Normally this should do two passes, to make all of the seed effect
+        // all of `mem`
+        for _ in 0..rounds {
+            for i in (0..RAND_SIZE/8).map(|i| i * 8) {
+                a += mem[i  ]; b += mem[i+1];
+                c += mem[i+2]; d += mem[i+3];
+                e += mem[i+4]; f += mem[i+5];
+                g += mem[i+6]; h += mem[i+7];
+                mix(&mut a, &mut b, &mut c, &mut d,
+                    &mut e, &mut f, &mut g, &mut h);
+                mem[i  ] = a; mem[i+1] = b;
+                mem[i+2] = c; mem[i+3] = d;
+                mem[i+4] = e; mem[i+5] = f;
+                mem[i+6] = g; mem[i+7] = h;
+            }
+        }
+
+        Self { mem, a: w(0), b: w(0), c: w(0) }
+    }
+}
+
+impl SeedableRng for IsaacCore {
+    type Seed = [u8; 32];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_u32 = [0u32; 8];
+        le::read_u32_into(&seed, &mut seed_u32);
+        // Convert the seed to `Wrapping<u32>` and zero-extend to `RAND_SIZE`.
+        let mut seed_extended = [w(0); RAND_SIZE];
+        for (x, y) in seed_extended.iter_mut().zip(seed_u32.iter()) {
+            *x = w(*y);
+        }
+        Self::init(seed_extended, 2)
+    }
+    
+    /// Create an ISAAC random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    fn seed_from_u64(seed: u64) -> Self {
+        let mut key = [w(0); RAND_SIZE];
+        key[0] = w(seed as u32);
+        key[1] = w((seed >> 32) as u32);
+        // Initialize with only one pass.
+        // A second pass does not improve the quality here, because all of the
+        // seed was already available in the first round.
+        // Not doing the second pass has the small advantage that if
+        // `seed == 0` this method produces exactly the same state as the
+        // reference implementation when used unseeded.
+        Self::init(key, 1)
+    }
+
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> {
+        // Custom `from_rng` implementation that fills a seed with the same size
+        // as the entire state.
+        let mut seed = [w(0u32); RAND_SIZE];
+        unsafe {
+            let ptr = seed.as_mut_ptr() as *mut u8;
+
+            let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE * 4);
+            rng.try_fill_bytes(slice)?;
+        }
+        for i in seed.iter_mut() {
+            *i = w(i.0.to_le());
+        }
+
+        Ok(Self::init(seed, 2))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use rand_core::{RngCore, SeedableRng};
+    use super::IsaacRng;
+
+    #[test]
+    fn test_isaac_construction() {
+        // Test that various construction techniques produce a working RNG.
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = IsaacRng::from_seed(seed);
+        assert_eq!(rng1.next_u32(), 2869442790);
+
+        let mut rng2 = IsaacRng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u32(), 3094074039);
+    }
+
+    #[test]
+    fn test_isaac_true_values_32() {
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                     57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = IsaacRng::from_seed(seed);
+        let mut results = [0u32; 10];
+        for i in results.iter_mut() { *i = rng1.next_u32(); }
+        let expected = [
+            2558573138, 873787463, 263499565, 2103644246, 3595684709,
+            4203127393, 264982119, 2765226902, 2737944514, 3900253796];
+        assert_eq!(results, expected);
+
+        let seed = [57,48,0,0, 50,9,1,0, 49,212,0,0, 148,38,0,0,
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng2 = IsaacRng::from_seed(seed);
+        // skip forward to the 10000th number
+        for _ in 0..10000 { rng2.next_u32(); }
+
+        for i in results.iter_mut() { *i = rng2.next_u32(); }
+        let expected = [
+            3676831399, 3183332890, 2834741178, 3854698763, 2717568474,
+            1576568959, 3507990155, 179069555, 141456972, 2478885421];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac_true_values_64() {
+        // As above, using little-endian versions of above values
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                    57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng = IsaacRng::from_seed(seed);
+        let mut results = [0u64; 5];
+        for i in results.iter_mut() { *i = rng.next_u64(); }
+        let expected = [
+            3752888579798383186, 9035083239252078381,18052294697452424037,
+            11876559110374379111, 16751462502657800130];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac_true_bytes() {
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                     57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng = IsaacRng::from_seed(seed);
+        let mut results = [0u8; 32];
+        rng.fill_bytes(&mut results);
+        // Same as first values in test_isaac_true_values as bytes in LE order
+        let expected = [82, 186, 128, 152, 71, 240, 20, 52,
+                        45, 175, 180, 15, 86, 16, 99, 125,
+                        101, 203, 81, 214, 97, 162, 134, 250,
+                        103, 78, 203, 15, 150, 3, 210, 164];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac_new_uninitialized() {
+        // Compare the results from initializing `IsaacRng` with
+        // `seed_from_u64(0)`, to make sure it is the same as the reference
+        // implementation when used uninitialized.
+        // Note: We only test the first 16 integers, not the full 256 of the
+        // first block.
+        let mut rng = IsaacRng::seed_from_u64(0);
+        let mut results = [0u32; 16];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        let expected: [u32; 16] = [
+            0x71D71FD2, 0xB54ADAE7, 0xD4788559, 0xC36129FA,
+            0x21DC1EA9, 0x3CB879CA, 0xD83B237F, 0xFA3CE5BD,
+            0x8D048509, 0xD82E9489, 0xDB452848, 0xCA20E846,
+            0x500F972E, 0x0EEFF940, 0x00D6B993, 0xBC12C17F];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac_clone() {
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                     57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = IsaacRng::from_seed(seed);
+        let mut rng2 = rng1.clone();
+        for _ in 0..16 {
+            assert_eq!(rng1.next_u32(), rng2.next_u32());
+        }
+    }
+
+    #[test]
+    #[cfg(feature="serde1")]
+    fn test_isaac_serde() {
+        use bincode;
+        use std::io::{BufWriter, BufReader};
+
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                     57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng = IsaacRng::from_seed(seed);
+
+        let buf: Vec<u8> = Vec::new();
+        let mut buf = BufWriter::new(buf);
+        bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
+
+        let buf = buf.into_inner().unwrap();
+        let mut read = BufReader::new(&buf[..]);
+        let mut deserialized: IsaacRng = bincode::deserialize_from(&mut read).expect("Could not deserialize");
+
+        for _ in 0..300 { // more than the 256 buffered results
+            assert_eq!(rng.next_u32(), deserialized.next_u32());
+        }
+    }
+}
diff --git a/rand/rand_isaac/src/isaac64.rs b/rand/rand_isaac/src/isaac64.rs
new file mode 100644
index 0000000..2712762
--- /dev/null
+++ b/rand/rand_isaac/src/isaac64.rs
@@ -0,0 +1,481 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The ISAAC-64 random number generator.
+
+use core::{fmt, slice};
+use core::num::Wrapping as w;
+use rand_core::{RngCore, SeedableRng, Error, le};
+use rand_core::block::{BlockRngCore, BlockRng64};
+use isaac_array::IsaacArray;
+
+#[allow(non_camel_case_types)]
+type w64 = w<u64>;
+
+const RAND_SIZE_LEN: usize = 8;
+const RAND_SIZE: usize = 1 << RAND_SIZE_LEN;
+
+/// A random number generator that uses ISAAC-64, the 64-bit variant of the
+/// ISAAC algorithm.
+///
+/// ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are
+/// the principal bitwise operations employed. It is the most advanced of a
+/// series of array based random number generator designed by Robert Jenkins
+/// in 1996[^1].
+///
+/// ISAAC-64 is mostly similar to ISAAC. Because it operates on 64-bit integers
+/// instead of 32-bit, it uses twice as much memory to hold its state and
+/// results. Also it uses different constants for shifts and indirect indexing,
+/// optimized to give good results for 64bit arithmetic.
+///
+/// ISAAC-64 is notably fast and produces excellent quality random numbers for
+/// non-cryptographic applications.
+///
+/// In spite of being designed with cryptographic security in mind, ISAAC hasn't
+/// been stringently cryptanalyzed and thus cryptographers do not not
+/// consensually trust it to be secure. When looking for a secure RNG, prefer
+/// [`Hc128Rng`] instead, which, like ISAAC, is an array-based RNG and one of
+/// the stream-ciphers selected the by eSTREAM contest.
+///
+/// ## Overview of the ISAAC-64 algorithm:
+/// (in pseudo-code)
+///
+/// ```text
+/// Input: a, b, c, s[256] // state
+/// Output: r[256] // results
+///
+/// mix(a,i) = !(a ^ a << 21)  if i = 0 mod 4
+///              a ^ a >>  5   if i = 1 mod 4
+///              a ^ a << 12   if i = 2 mod 4
+///              a ^ a >> 33   if i = 3 mod 4
+///
+/// c = c + 1
+/// b = b + c
+///
+/// for i in 0..256 {
+///     x = s_[i]
+///     a = mix(a,i) + s[i+128 mod 256]
+///     y = a + b + s[x>>3 mod 256]
+///     s[i] = y
+///     b = x + s[y>>11 mod 256]
+///     r[i] = b
+/// }
+/// ```
+///
+/// This implementation uses [`BlockRng64`] to implement the [`RngCore`] methods.
+///
+/// See for more information the documentation of [`IsaacRng`].
+///
+/// [^1]: Bob Jenkins, [*ISAAC and RC4*](
+///       http://burtleburtle.net/bob/rand/isaac.html)
+///
+/// [`IsaacRng`]: ../isaac/struct.IsaacRng.html
+/// [`Hc128Rng`]: ../../rand_hc/struct.Hc128Rng.html
+/// [`BlockRng64`]: ../../rand_core/block/struct.BlockRng64.html
+/// [`RngCore`]: ../../rand_core/trait.RngCore.html
+#[derive(Clone, Debug)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct Isaac64Rng(BlockRng64<Isaac64Core>);
+
+impl RngCore for Isaac64Rng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for Isaac64Rng {
+    type Seed = <Isaac64Core as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Isaac64Rng(BlockRng64::<Isaac64Core>::from_seed(seed))
+    }
+
+    /// Create an ISAAC random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    fn seed_from_u64(seed: u64) -> Self {
+        Isaac64Rng(BlockRng64::<Isaac64Core>::seed_from_u64(seed))
+    }
+
+    fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error> {
+        BlockRng64::<Isaac64Core>::from_rng(rng).map(|rng| Isaac64Rng(rng))
+    }
+}
+
+impl Isaac64Rng {
+    /// Create an ISAAC-64 random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    #[deprecated(since="0.6.0", note="use SeedableRng::seed_from_u64 instead")]
+    pub fn new_from_u64(seed: u64) -> Self {
+        Self::seed_from_u64(seed)
+    }
+}
+
+/// The core of `Isaac64Rng`, used with `BlockRng`.
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct Isaac64Core {
+    #[cfg_attr(feature="serde1",serde(with="super::isaac_array::isaac_array_serde"))]
+    mem: [w64; RAND_SIZE],
+    a: w64,
+    b: w64,
+    c: w64,
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for Isaac64Core {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Isaac64Core {{}}")
+    }
+}
+
+impl BlockRngCore for Isaac64Core {
+    type Item = u64;
+    type Results = IsaacArray<Self::Item>;
+
+    /// Refills the output buffer, `results`. See also the pseudocode desciption
+    /// of the algorithm in the [`Isaac64Rng`] documentation.
+    ///
+    /// Optimisations used (similar to the reference implementation):
+    /// 
+    /// - The loop is unrolled 4 times, once for every constant of mix().
+    /// - The contents of the main loop are moved to a function `rngstep`, to
+    ///   reduce code duplication.
+    /// - We use local variables for a and b, which helps with optimisations.
+    /// - We split the main loop in two, one that operates over 0..128 and one
+    ///   over 128..256. This way we can optimise out the addition and modulus
+    ///   from `s[i+128 mod 256]`.
+    /// - We maintain one index `i` and add `m` or `m2` as base (m2 for the
+    ///   `s[i+128 mod 256]`), relying on the optimizer to turn it into pointer
+    ///   arithmetic.
+    /// - We fill `results` backwards. The reference implementation reads values
+    ///   from `results` in reverse. We read them in the normal direction, to
+    ///   make `fill_bytes` a memcopy. To maintain compatibility we fill in
+    ///   reverse.
+    /// 
+    /// [`Isaac64Rng`]: struct.Isaac64Rng.html
+    fn generate(&mut self, results: &mut IsaacArray<Self::Item>) {
+        self.c += w(1);
+        // abbreviations
+        let mut a = self.a;
+        let mut b = self.b + self.c;
+        const MIDPOINT: usize = RAND_SIZE / 2;
+
+        #[inline]
+        fn ind(mem:&[w64; RAND_SIZE], v: w64, amount: usize) -> w64 {
+            let index = (v >> amount).0 as usize % RAND_SIZE;
+            mem[index]
+        }
+
+        #[inline]
+        fn rngstep(mem: &mut [w64; RAND_SIZE],
+                   results: &mut [u64; RAND_SIZE],
+                   mix: w64,
+                   a: &mut w64,
+                   b: &mut w64,
+                   base: usize,
+                   m: usize,
+                   m2: usize) {
+            let x = mem[base + m];
+            *a = mix + mem[base + m2];
+            let y = *a + *b + ind(&mem, x, 3);
+            mem[base + m] = y;
+            *b = x + ind(&mem, y, 3 + RAND_SIZE_LEN);
+            results[RAND_SIZE - 1 - base - m] = (*b).0;
+        }
+
+        let mut m = 0;
+        let mut m2 = MIDPOINT;
+        for i in (0..MIDPOINT/4).map(|i| i * 4) {
+            rngstep(&mut self.mem, results, !(a ^ (a << 21)), &mut a, &mut b, i + 0, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a >> 5 ),  &mut a, &mut b, i + 1, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a << 12),  &mut a, &mut b, i + 2, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a >> 33),  &mut a, &mut b, i + 3, m, m2);
+        }
+
+        m = MIDPOINT;
+        m2 = 0;
+        for i in (0..MIDPOINT/4).map(|i| i * 4) {
+            rngstep(&mut self.mem, results, !(a ^ (a << 21)), &mut a, &mut b, i + 0, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a >> 5 ),  &mut a, &mut b, i + 1, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a << 12),  &mut a, &mut b, i + 2, m, m2);
+            rngstep(&mut self.mem, results,   a ^ (a >> 33),  &mut a, &mut b, i + 3, m, m2);
+        }
+
+        self.a = a;
+        self.b = b;
+    }
+}
+
+impl Isaac64Core {
+    /// Create a new ISAAC-64 random number generator.
+    fn init(mut mem: [w64; RAND_SIZE], rounds: u32) -> Self {
+        fn mix(a: &mut w64, b: &mut w64, c: &mut w64, d: &mut w64,
+               e: &mut w64, f: &mut w64, g: &mut w64, h: &mut w64) {
+            *a -= *e; *f ^= *h >> 9;  *h += *a;
+            *b -= *f; *g ^= *a << 9;  *a += *b;
+            *c -= *g; *h ^= *b >> 23; *b += *c;
+            *d -= *h; *a ^= *c << 15; *c += *d;
+            *e -= *a; *b ^= *d >> 14; *d += *e;
+            *f -= *b; *c ^= *e << 20; *e += *f;
+            *g -= *c; *d ^= *f >> 17; *f += *g;
+            *h -= *d; *e ^= *g << 14; *g += *h;
+        }
+
+        // These numbers are the result of initializing a...h with the
+        // fractional part of the golden ratio in binary (0x9e3779b97f4a7c13)
+        // and applying mix() 4 times.
+        let mut a = w(0x647c4677a2884b7c);
+        let mut b = w(0xb9f8b322c73ac862);
+        let mut c = w(0x8c0ea5053d4712a0);
+        let mut d = w(0xb29b2e824a595524);
+        let mut e = w(0x82f053db8355e0ce);
+        let mut f = w(0x48fe4a0fa5a09315);
+        let mut g = w(0xae985bf2cbfc89ed);
+        let mut h = w(0x98f5704f6c44c0ab);
+
+        // Normally this should do two passes, to make all of the seed effect
+        // all of `mem`
+        for _ in 0..rounds {
+            for i in (0..RAND_SIZE/8).map(|i| i * 8) {
+                a += mem[i  ]; b += mem[i+1];
+                c += mem[i+2]; d += mem[i+3];
+                e += mem[i+4]; f += mem[i+5];
+                g += mem[i+6]; h += mem[i+7];
+                mix(&mut a, &mut b, &mut c, &mut d,
+                    &mut e, &mut f, &mut g, &mut h);
+                mem[i  ] = a; mem[i+1] = b;
+                mem[i+2] = c; mem[i+3] = d;
+                mem[i+4] = e; mem[i+5] = f;
+                mem[i+6] = g; mem[i+7] = h;
+            }
+        }
+
+        Self { mem, a: w(0), b: w(0), c: w(0) }
+    }
+
+    /// Create an ISAAC-64 random number generator using an `u64` as seed.
+    /// If `seed == 0` this will produce the same stream of random numbers as
+    /// the reference implementation when used unseeded.
+    #[deprecated(since="0.6.0", note="use SeedableRng::seed_from_u64 instead")]
+    pub fn new_from_u64(seed: u64) -> Self {
+        Self::seed_from_u64(seed)
+    }
+}
+
+impl SeedableRng for Isaac64Core {
+    type Seed = [u8; 32];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_u64 = [0u64; 4];
+        le::read_u64_into(&seed, &mut seed_u64);
+        // Convert the seed to `Wrapping<u64>` and zero-extend to `RAND_SIZE`.
+        let mut seed_extended = [w(0); RAND_SIZE];
+        for (x, y) in seed_extended.iter_mut().zip(seed_u64.iter()) {
+            *x = w(*y);
+        }
+        Self::init(seed_extended, 2)
+    }
+    
+    fn seed_from_u64(seed: u64) -> Self {
+        let mut key = [w(0); RAND_SIZE];
+        key[0] = w(seed);
+        // Initialize with only one pass.
+        // A second pass does not improve the quality here, because all of the
+        // seed was already available in the first round.
+        // Not doing the second pass has the small advantage that if
+        // `seed == 0` this method produces exactly the same state as the
+        // reference implementation when used unseeded.
+        Self::init(key, 1)
+    }
+
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> {
+        // Custom `from_rng` implementation that fills a seed with the same size
+        // as the entire state.
+        let mut seed = [w(0u64); RAND_SIZE];
+        unsafe {
+            let ptr = seed.as_mut_ptr() as *mut u8;
+            let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE * 8);
+            rng.try_fill_bytes(slice)?;
+        }
+        for i in seed.iter_mut() {
+            *i = w(i.0.to_le());
+        }
+
+        Ok(Self::init(seed, 2))
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use rand_core::{RngCore, SeedableRng};
+    use super::Isaac64Rng;
+
+    #[test]
+    fn test_isaac64_construction() {
+        // Test that various construction techniques produce a working RNG.
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = Isaac64Rng::from_seed(seed);
+        assert_eq!(rng1.next_u64(), 14964555543728284049);
+
+        let mut rng2 = Isaac64Rng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u64(), 919595328260451758);
+    }
+
+    #[test]
+    fn test_isaac64_true_values_64() {
+        let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0,
+                    200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0];
+        let mut rng1 = Isaac64Rng::from_seed(seed);
+        let mut results = [0u64; 10];
+        for i in results.iter_mut() { *i = rng1.next_u64(); }
+        let expected = [
+                   15071495833797886820, 7720185633435529318,
+                   10836773366498097981, 5414053799617603544,
+                   12890513357046278984, 17001051845652595546,
+                   9240803642279356310, 12558996012687158051,
+                   14673053937227185542, 1677046725350116783];
+        assert_eq!(results, expected);
+
+        let seed = [57,48,0,0, 0,0,0,0, 50,9,1,0, 0,0,0,0,
+                    49,212,0,0, 0,0,0,0, 148,38,0,0, 0,0,0,0];
+        let mut rng2 = Isaac64Rng::from_seed(seed);
+        // skip forward to the 10000th number
+        for _ in 0..10000 { rng2.next_u64(); }
+
+        for i in results.iter_mut() { *i = rng2.next_u64(); }
+        let expected = [
+            18143823860592706164, 8491801882678285927, 2699425367717515619,
+            17196852593171130876, 2606123525235546165, 15790932315217671084,
+            596345674630742204, 9947027391921273664, 11788097613744130851,
+            10391409374914919106];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac64_true_values_32() {
+        let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0,
+                    200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0];
+        let mut rng = Isaac64Rng::from_seed(seed);
+        let mut results = [0u32; 12];
+        for i in results.iter_mut() { *i = rng.next_u32(); }
+        // Subset of above values, as an LE u32 sequence
+        let expected = [
+                    3477963620, 3509106075,
+                    687845478, 1797495790,
+                    227048253, 2523132918,
+                    4044335064, 1260557630,
+                    4079741768, 3001306521,
+                    69157722, 3958365844];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac64_true_values_mixed() {
+        let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0,
+                    200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0];
+        let mut rng = Isaac64Rng::from_seed(seed);
+        // Test alternating between `next_u64` and `next_u32` works as expected.
+        // Values are the same as `test_isaac64_true_values` and
+        // `test_isaac64_true_values_32`.
+        assert_eq!(rng.next_u64(), 15071495833797886820);
+        assert_eq!(rng.next_u32(), 687845478);
+        assert_eq!(rng.next_u32(), 1797495790);
+        assert_eq!(rng.next_u64(), 10836773366498097981);
+        assert_eq!(rng.next_u32(), 4044335064);
+        // Skip one u32
+        assert_eq!(rng.next_u64(), 12890513357046278984);
+        assert_eq!(rng.next_u32(), 69157722);
+    }
+
+    #[test]
+    fn test_isaac64_true_bytes() {
+        let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0,
+                    200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0];
+        let mut rng = Isaac64Rng::from_seed(seed);
+        let mut results = [0u8; 32];
+        rng.fill_bytes(&mut results);
+        // Same as first values in test_isaac64_true_values as bytes in LE order
+        let expected = [100, 131, 77, 207, 155, 181, 40, 209,
+                        102, 176, 255, 40, 238, 155, 35, 107,
+                        61, 123, 136, 13, 246, 243, 99, 150,
+                        216, 167, 15, 241, 62, 149, 34, 75];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac64_new_uninitialized() {
+        // Compare the results from initializing `IsaacRng` with
+        // `seed_from_u64(0)`, to make sure it is the same as the reference
+        // implementation when used uninitialized.
+        // Note: We only test the first 16 integers, not the full 256 of the
+        // first block.
+        let mut rng = Isaac64Rng::seed_from_u64(0);
+        let mut results = [0u64; 16];
+        for i in results.iter_mut() { *i = rng.next_u64(); }
+        let expected: [u64; 16] = [
+            0xF67DFBA498E4937C, 0x84A5066A9204F380, 0xFEE34BD5F5514DBB,
+            0x4D1664739B8F80D6, 0x8607459AB52A14AA, 0x0E78BC5A98529E49,
+            0xFE5332822AD13777, 0x556C27525E33D01A, 0x08643CA615F3149F,
+            0xD0771FAF3CB04714, 0x30E86F68A37B008D, 0x3074EBC0488A3ADF,
+            0x270645EA7A2790BC, 0x5601A0A8D3763C6A, 0x2F83071F53F325DD,
+            0xB9090F3D42D2D2EA];
+        assert_eq!(results, expected);
+    }
+
+    #[test]
+    fn test_isaac64_clone() {
+        let seed = [1,0,0,0, 0,0,0,0, 23,0,0,0, 0,0,0,0,
+                    200,1,0,0, 0,0,0,0, 210,30,0,0, 0,0,0,0];
+        let mut rng1 = Isaac64Rng::from_seed(seed);
+        let mut rng2 = rng1.clone();
+        for _ in 0..16 {
+            assert_eq!(rng1.next_u64(), rng2.next_u64());
+        }
+    }
+
+    #[test]
+    #[cfg(feature="serde1")]
+    fn test_isaac64_serde() {
+        use bincode;
+        use std::io::{BufWriter, BufReader};
+
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                     57,48,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng = Isaac64Rng::from_seed(seed);
+
+        let buf: Vec<u8> = Vec::new();
+        let mut buf = BufWriter::new(buf);
+        bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
+
+        let buf = buf.into_inner().unwrap();
+        let mut read = BufReader::new(&buf[..]);
+        let mut deserialized: Isaac64Rng = bincode::deserialize_from(&mut read).expect("Could not deserialize");
+
+        for _ in 0..300 { // more than the 256 buffered results
+            assert_eq!(rng.next_u64(), deserialized.next_u64());
+        }
+    }
+}
diff --git a/rand/rand_isaac/src/isaac_array.rs b/rand/rand_isaac/src/isaac_array.rs
new file mode 100644
index 0000000..0fa6147
--- /dev/null
+++ b/rand/rand_isaac/src/isaac_array.rs
@@ -0,0 +1,136 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017-2018 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! ISAAC helper functions for 256-element arrays.
+
+// Terrible workaround because arrays with more than 32 elements do not
+// implement `AsRef`, `Default`, `Serialize`, `Deserialize`, or any other
+// traits for that matter.
+
+#[cfg(feature="serde1")] use serde::{Serialize, Deserialize};
+
+const RAND_SIZE_LEN: usize = 8;
+const RAND_SIZE: usize = 1 << RAND_SIZE_LEN;
+
+
+#[derive(Copy, Clone)]
+#[allow(missing_debug_implementations)]
+#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))]
+pub struct IsaacArray<T> {
+    #[cfg_attr(feature="serde1",serde(with="isaac_array_serde"))]
+    #[cfg_attr(feature="serde1", serde(bound(
+        serialize = "T: Serialize",
+        deserialize = "T: Deserialize<'de> + Copy + Default")))]
+    inner: [T; RAND_SIZE]
+}
+
+impl<T> ::core::convert::AsRef<[T]> for IsaacArray<T> {
+    #[inline(always)]
+    fn as_ref(&self) -> &[T] {
+        &self.inner[..]
+    }
+}
+
+impl<T> ::core::convert::AsMut<[T]> for IsaacArray<T> {
+    #[inline(always)]
+    fn as_mut(&mut self) -> &mut [T] {
+        &mut self.inner[..]
+    }
+}
+
+impl<T> ::core::ops::Deref for IsaacArray<T> {
+    type Target = [T; RAND_SIZE];
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl<T> ::core::ops::DerefMut for IsaacArray<T> {
+    #[inline(always)]
+    fn deref_mut(&mut self) -> &mut [T; RAND_SIZE] {
+        &mut self.inner
+    }
+}
+
+impl<T> ::core::default::Default for IsaacArray<T> where T: Copy + Default {
+    fn default() -> IsaacArray<T> {
+        IsaacArray { inner: [T::default(); RAND_SIZE] }
+    }
+}
+
+
+#[cfg(feature="serde1")]
+pub(super) mod isaac_array_serde {
+    const RAND_SIZE_LEN: usize = 8;
+    const RAND_SIZE: usize = 1 << RAND_SIZE_LEN;
+
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+    use serde::de::{Visitor,SeqAccess};
+    use serde::de;
+
+    use core::fmt;
+
+    pub fn serialize<T, S>(arr: &[T;RAND_SIZE], ser: S) -> Result<S::Ok, S::Error>
+    where
+        T: Serialize,
+        S: Serializer
+    {
+        use serde::ser::SerializeTuple;
+
+        let mut seq = ser.serialize_tuple(RAND_SIZE)?;
+
+        for e in arr.iter() {
+            seq.serialize_element(&e)?;
+        }
+
+        seq.end()
+    }
+
+    #[inline]
+    pub fn deserialize<'de, T, D>(de: D) -> Result<[T;RAND_SIZE], D::Error>
+    where
+        T: Deserialize<'de>+Default+Copy,
+        D: Deserializer<'de>,
+    {
+        use core::marker::PhantomData;
+        struct ArrayVisitor<T> {
+            _pd: PhantomData<T>,
+        };
+        impl<'de,T> Visitor<'de> for ArrayVisitor<T>
+        where
+            T: Deserialize<'de>+Default+Copy
+        {
+            type Value = [T; RAND_SIZE];
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("Isaac state array")
+            }
+
+            #[inline]
+            fn visit_seq<A>(self, mut seq: A) -> Result<[T; RAND_SIZE], A::Error>
+            where
+                A: SeqAccess<'de>,
+            {
+                let mut out = [Default::default();RAND_SIZE];
+
+                for i in 0..RAND_SIZE {
+                    match seq.next_element()? {
+                        Some(val) => out[i] = val,
+                        None => return Err(de::Error::invalid_length(i, &self)),
+                    };
+                }
+
+                Ok(out)
+            }
+        }
+
+        de.deserialize_tuple(RAND_SIZE, ArrayVisitor{_pd: PhantomData})
+    }
+}
diff --git a/rand/rand_isaac/src/lib.rs b/rand/rand_isaac/src/lib.rs
new file mode 100644
index 0000000..ec82d8e
--- /dev/null
+++ b/rand/rand_isaac/src/lib.rs
@@ -0,0 +1,36 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The ISAAC and ISAAC-64 random number generators.
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
+
+#![cfg_attr(not(all(feature="serde1", test)), no_std)]
+
+extern crate rand_core;
+
+#[cfg(feature="serde1")] extern crate serde;
+#[cfg(feature="serde1")] #[macro_use] extern crate serde_derive;
+
+// To test serialization we need bincode and the standard library
+#[cfg(all(feature="serde1", test))] extern crate bincode;
+#[cfg(all(feature="serde1", test))] extern crate std as core;
+
+pub mod isaac;
+pub mod isaac64;
+
+mod isaac_array;
+
+pub use self::isaac::IsaacRng;
+pub use self::isaac64::Isaac64Rng;
diff --git a/rand/rand_pcg/CHANGELOG.md b/rand/rand_pcg/CHANGELOG.md
new file mode 100644
index 0000000..d37408d
--- /dev/null
+++ b/rand/rand_pcg/CHANGELOG.md
@@ -0,0 +1,14 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.1] - 2018-10-04
+- make `bincode` an explicit dependency when using Serde
+
+## [0.1.0] - 2018-10-04
+Initial release, including:
+
+- `Lcg64Xsh32` aka `Pcg32`
+- `Mcg128Xsl64` aka `Pcg64Mcg`
diff --git a/rand/rand_pcg/COPYRIGHT b/rand/rand_pcg/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_pcg/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_pcg/Cargo.toml b/rand/rand_pcg/Cargo.toml
new file mode 100644
index 0000000..c8a29fc
--- /dev/null
+++ b/rand/rand_pcg/Cargo.toml
@@ -0,0 +1,37 @@
+[package]
+name = "rand_pcg"
+version = "0.1.1"
+authors = ["The Rand Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_pcg"
+homepage = "https://crates.io/crates/rand_pcg"
+description = """
+Selected PCG random number generators
+"""
+keywords = ["random", "rng", "pcg"]
+categories = ["algorithms", "no-std"]
+build = "build.rs"
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[features]
+serde1 = ["serde", "serde_derive"]
+
+[dependencies]
+rand_core = { path = "../rand_core", version = "0.3", default-features=false }
+serde = { version = "1", optional = true }
+serde_derive = { version = "^1.0.38", optional = true }
+
+[dev-dependencies]
+# This is for testing serde, unfortunately we can't specify feature-gated dev
+# deps yet, see: https://github.com/rust-lang/cargo/issues/1596
+# TODO: we shouldn't have to depend on i128 directly; it breaks tests on old
+# compilers. `bincode` should automatically support this.
+bincode = { version = "1", features = ["i128"] }
+
+[build-dependencies]
+rustc_version = "0.2"
diff --git a/rand/rand_pcg/LICENSE-APACHE b/rand/rand_pcg/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_pcg/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     https://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
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diff --git a/rand/rand_pcg/LICENSE-MIT b/rand/rand_pcg/LICENSE-MIT
new file mode 100644
index 0000000..d46f058
--- /dev/null
+++ b/rand/rand_pcg/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright (c) 2014-2017 Melissa O'Neill and PCG Project contributors
+Copyright 2018 Developers of the Rand project
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_pcg/README.md b/rand/rand_pcg/README.md
new file mode 100644
index 0000000..4599813
--- /dev/null
+++ b/rand/rand_pcg/README.md
@@ -0,0 +1,51 @@
+# rand_pcg
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg?branch=master)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_pcg.svg)](https://crates.io/crates/rand_pcg)
+[[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_pcg)
+[![API](https://docs.rs/rand_pcg/badge.svg)](https://docs.rs/rand_pcg)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+Implements a selection of PCG random number generators.
+
+> PCG is a family of simple fast space-efficient statistically good algorithms
+> for random number generation. [Melissa O'Neill, Harvey Mudd College, 2014].
+
+The PCG algorithms are not suitable for cryptographic uses, but perform well
+in statistical tests, use little memory and are fairly fast.
+See the [pcg-random website](http://www.pcg-random.org/).
+
+This crate depends on [rand_core](https://crates.io/crates/rand_core) and is
+part of the [Rand project](https://github.com/rust-random/rand).
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_pcg)
+-   [API documentation (docs.rs)](https://docs.rs/rand_pcg)
+-   [Changelog](CHANGELOG.md)
+
+
+## Crate Features
+
+`rand_pcg` is `no_std` compatible. It does not require any functionality
+outside of the `core` lib, thus there are no features to configure.
+
+The `serde1` feature includes implementations of `Serialize` and `Deserialize`
+for the included RNGs. NOTE: to use binary serialisation with any of the 64-bit
+output (128-bit internal) RNGs, you must add the following dependency, since the
+`i128` feature is not current enabled by default (this should be fixed soon):
+
+```
+bincode = { version = "1", features = ["i128"] }
+```
+
+
+## License
+
+`rand_pcg` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_pcg/build.rs b/rand/rand_pcg/build.rs
new file mode 100644
index 0000000..cb3ae20
--- /dev/null
+++ b/rand/rand_pcg/build.rs
@@ -0,0 +1,8 @@
+extern crate rustc_version;
+use rustc_version::{version, Version};
+
+fn main() {
+    if version().unwrap() >= Version::parse("1.26.0").unwrap() {
+        println!("cargo:rustc-cfg=rust_1_26");
+    }
+}
diff --git a/rand/rand_pcg/src/lib.rs b/rand/rand_pcg/src/lib.rs
new file mode 100644
index 0000000..5160e87
--- /dev/null
+++ b/rand/rand_pcg/src/lib.rs
@@ -0,0 +1,48 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The PCG random number generators.
+//!
+//! This is a native Rust implementation of a small selection of PCG generators.
+//! The primary goal of this crate is simple, minimal, well-tested code; in
+//! other words it is explicitly not a goal to re-implement all of PCG.
+//!
+//! This crate provides:
+//!
+//! -   `Pcg32` aka `Lcg64Xsh32`, officially known as `pcg32`, a general
+//!     purpose RNG. This is a good choice on both 32-bit and 64-bit CPUs
+//!     (for 32-bit output).
+//! -   `Pcg64Mcg` aka `Mcg128Xsl64`, officially known as `mcg_xsl_rr_128_64`,
+//!     a general purpose RNG using 128-bit multiplications. This has poor
+//!     performance on 32-bit CPUs but is a good choice on 64-bit CPUs for
+//!     both 32-bit and 64-bit output. (Note: this RNG is only available using
+//!     Rust 1.26 or later.)
+//!
+//! Both of these use 16 bytes of state and 128-bit seeds, and are considered
+//! value-stable (i.e. any change affecting the output given a fixed seed would
+//! be considered a breaking change to the crate).
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+
+#![no_std]
+
+extern crate rand_core;
+
+#[cfg(feature="serde1")] extern crate serde;
+#[cfg(feature="serde1")] #[macro_use] extern crate serde_derive;
+
+mod pcg64;
+#[cfg(rust_1_26)] mod pcg128;
+
+pub use self::pcg64::{Pcg32, Lcg64Xsh32};
+#[cfg(rust_1_26)] pub use self::pcg128::{Pcg64Mcg, Mcg128Xsl64};
diff --git a/rand/rand_pcg/src/pcg128.rs b/rand/rand_pcg/src/pcg128.rs
new file mode 100644
index 0000000..9aff506
--- /dev/null
+++ b/rand/rand_pcg/src/pcg128.rs
@@ -0,0 +1,122 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017 Paul Dicker.
+// Copyright 2014-2017 Melissa O'Neill and PCG Project contributors
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! PCG random number generators
+
+// This is the default multiplier used by PCG for 64-bit state.
+const MULTIPLIER: u128 = 0x2360_ED05_1FC6_5DA4_4385_DF64_9FCC_F645;
+
+use core::fmt;
+use core::mem::transmute;
+use rand_core::{RngCore, SeedableRng, Error, le};
+
+/// A PCG random number generator (XSL 128/64 (MCG) variant).
+///
+/// Permuted Congruential Generator with 128-bit state, internal Multiplicative
+/// Congruential Generator, and 64-bit output via "xorshift low (bits),
+/// random rotation" output function.
+///
+/// This is a 128-bit MCG with the PCG-XSL-RR output function.
+/// Note that compared to the standard `pcg64` (128-bit LCG with PCG-XSL-RR
+/// output function), this RNG is faster, also has a long cycle, and still has
+/// good performance on statistical tests.
+///
+/// Note: this RNG is only available using Rust 1.26 or later.
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize,Deserialize))]
+pub struct Mcg128Xsl64 {
+    state: u128,
+}
+
+/// A friendly name for `Mcg128Xsl64`.
+pub type Pcg64Mcg = Mcg128Xsl64;
+
+impl Mcg128Xsl64 {
+    /// Construct an instance compatible with PCG seed.
+    ///
+    /// Note that PCG specifies a default value for the parameter:
+    ///
+    /// - `state = 0xcafef00dd15ea5e5`
+    pub fn new(state: u128) -> Self {
+        // Force low bit to 1, as in C version (C++ uses `state | 3` instead).
+        Mcg128Xsl64 { state: state | 1 }
+    }
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for Mcg128Xsl64 {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Mcg128Xsl64 {{}}")
+    }
+}
+
+/// We use a single 126-bit seed to initialise the state and select a stream.
+/// Two `seed` bits (lowest order of last byte) are ignored.
+impl SeedableRng for Mcg128Xsl64 {
+    type Seed = [u8; 16];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        // Read as if a little-endian u128 value:
+        let mut seed_u64 = [0u64; 2];
+        le::read_u64_into(&seed, &mut seed_u64);
+        let state = (seed_u64[0] as u128) |
+                    (seed_u64[1] as u128) << 64;
+        Mcg128Xsl64::new(state)
+    }
+}
+
+impl RngCore for Mcg128Xsl64 {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        self.next_u64() as u32
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        // prepare the LCG for the next round
+        let state = self.state.wrapping_mul(MULTIPLIER);
+        self.state = state;
+
+        // Output function XSL RR ("xorshift low (bits), random rotation")
+        // Constants are for 128-bit state, 64-bit output
+        const XSHIFT: u32 = 64;     // (128 - 64 + 64) / 2
+        const ROTATE: u32 = 122;    // 128 - 6
+
+        let rot = (state >> ROTATE) as u32;
+        let xsl = ((state >> XSHIFT) as u64) ^ (state as u64);
+        xsl.rotate_right(rot)
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        // specialisation of impls::fill_bytes_via_next; approx 3x faster
+        let mut left = dest;
+        while left.len() >= 8 {
+            let (l, r) = {left}.split_at_mut(8);
+            left = r;
+            let chunk: [u8; 8] = unsafe {
+                transmute(self.next_u64().to_le())
+            };
+            l.copy_from_slice(&chunk);
+        }
+        let n = left.len();
+        if n > 0 {
+            let chunk: [u8; 8] = unsafe {
+                transmute(self.next_u64().to_le())
+            };
+            left.copy_from_slice(&chunk[..n]);
+        }
+    }
+
+    #[inline]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
diff --git a/rand/rand_pcg/src/pcg64.rs b/rand/rand_pcg/src/pcg64.rs
new file mode 100644
index 0000000..9177ec2
--- /dev/null
+++ b/rand/rand_pcg/src/pcg64.rs
@@ -0,0 +1,141 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017 Paul Dicker.
+// Copyright 2014-2017 Melissa O'Neill and PCG Project contributors
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! PCG random number generators
+
+use core::fmt;
+use core::mem::transmute;
+use rand_core::{RngCore, SeedableRng, Error, le, impls};
+
+// This is the default multiplier used by PCG for 64-bit state.
+const MULTIPLIER: u64 = 6364136223846793005;
+
+/// A PCG random number generator (XSH RR 64/32 (LCG) variant).
+///
+/// Permuted Congruential Generator with 64-bit state, internal Linear
+/// Congruential Generator, and 32-bit output via "xorshift high (bits),
+/// random rotation" output function.
+///
+/// This is a 64-bit LCG with explicitly chosen stream with the PCG-XSH-RR
+/// output function. This combination is the standard `pcg32`.
+///
+/// Despite the name, this implementation uses 16 bytes (128 bit) space
+/// comprising 64 bits of state and 64 bits stream selector. These are both set
+/// by `SeedableRng`, using a 128-bit seed.
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize,Deserialize))]
+pub struct Lcg64Xsh32 {
+    state: u64,
+    increment: u64,
+}
+
+/// `Lcg64Xsh32` is also officially known as `pcg32`.
+pub type Pcg32 = Lcg64Xsh32;
+
+impl Lcg64Xsh32 {
+    /// Construct an instance compatible with PCG seed and stream.
+    ///
+    /// Note that PCG specifies default values for both parameters:
+    ///
+    /// - `state = 0xcafef00dd15ea5e5`
+    /// - `stream = 721347520444481703`
+    pub fn new(state: u64, stream: u64) -> Self {
+        // The increment must be odd, hence we discard one bit:
+        let increment = (stream << 1) | 1;
+        Lcg64Xsh32::from_state_incr(state, increment)
+    }
+
+    #[inline]
+    fn from_state_incr(state: u64, increment: u64) -> Self {
+        let mut pcg = Lcg64Xsh32 { state, increment };
+        // Move away from inital value:
+        pcg.state = pcg.state.wrapping_add(pcg.increment);
+        pcg.step();
+        pcg
+    }
+
+    #[inline]
+    fn step(&mut self) {
+        // prepare the LCG for the next round
+        self.state = self.state
+            .wrapping_mul(MULTIPLIER)
+            .wrapping_add(self.increment);
+    }
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for Lcg64Xsh32 {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "Lcg64Xsh32 {{}}")
+    }
+}
+
+/// We use a single 127-bit seed to initialise the state and select a stream.
+/// One `seed` bit (lowest bit of `seed[8]`) is ignored.
+impl SeedableRng for Lcg64Xsh32 {
+    type Seed = [u8; 16];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_u64 = [0u64; 2];
+        le::read_u64_into(&seed, &mut seed_u64);
+
+        // The increment must be odd, hence we discard one bit:
+        Lcg64Xsh32::from_state_incr(seed_u64[0], seed_u64[1] | 1)
+    }
+}
+
+impl RngCore for Lcg64Xsh32 {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        let state = self.state;
+        self.step();
+
+        // Output function XSH RR: xorshift high (bits), followed by a random rotate
+        // Constants are for 64-bit state, 32-bit output
+        const ROTATE: u32 = 59; // 64 - 5
+        const XSHIFT: u32 = 18; // (5 + 32) / 2
+        const SPARE: u32 = 27;  // 64 - 32 - 5
+
+        let rot = (state >> ROTATE) as u32;
+        let xsh = (((state >> XSHIFT) ^ state) >> SPARE) as u32;
+        xsh.rotate_right(rot)
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_u32(self)
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        // specialisation of impls::fill_bytes_via_next; approx 40% faster
+        let mut left = dest;
+        while left.len() >= 4 {
+            let (l, r) = {left}.split_at_mut(4);
+            left = r;
+            let chunk: [u8; 4] = unsafe {
+                transmute(self.next_u32().to_le())
+            };
+            l.copy_from_slice(&chunk);
+        }
+        let n = left.len();
+        if n > 0 {
+            let chunk: [u8; 4] = unsafe {
+                transmute(self.next_u32().to_le())
+            };
+            left.copy_from_slice(&chunk[..n]);
+        }
+    }
+
+    #[inline]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
diff --git a/rand/rand_pcg/tests/lcg64xsh32.rs b/rand/rand_pcg/tests/lcg64xsh32.rs
new file mode 100644
index 0000000..775b12c
--- /dev/null
+++ b/rand/rand_pcg/tests/lcg64xsh32.rs
@@ -0,0 +1,58 @@
+extern crate rand_pcg;
+extern crate rand_core;
+#[cfg(all(feature="serde1", test))] extern crate bincode;
+
+use rand_core::{RngCore, SeedableRng};
+use rand_pcg::{Lcg64Xsh32, Pcg32};
+
+#[test]
+fn test_lcg64xsh32_construction() {
+    // Test that various construction techniques produce a working RNG.
+    let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
+    let mut rng1 = Lcg64Xsh32::from_seed(seed);
+    assert_eq!(rng1.next_u64(), 1204678643940597513);
+
+    let mut rng2 = Lcg64Xsh32::from_rng(&mut rng1).unwrap();
+    assert_eq!(rng2.next_u64(), 12384929573776311845);
+
+    let mut rng3 = Lcg64Xsh32::seed_from_u64(0);
+    assert_eq!(rng3.next_u64(), 18195738587432868099);
+
+    // This is the same as Lcg64Xsh32, so we only have a single test:
+    let mut rng4 = Pcg32::seed_from_u64(0);
+    assert_eq!(rng4.next_u64(), 18195738587432868099);
+}
+
+#[test]
+fn test_lcg64xsh32_true_values() {
+    // Numbers copied from official test suite.
+    let mut rng = Lcg64Xsh32::new(42, 54);
+
+    let mut results = [0u32; 6];
+    for i in results.iter_mut() { *i = rng.next_u32(); }
+    let expected: [u32; 6] = [0xa15c02b7, 0x7b47f409, 0xba1d3330,
+        0x83d2f293, 0xbfa4784b, 0xcbed606e];
+    assert_eq!(results, expected);
+}
+
+#[cfg(feature="serde1")]
+#[test]
+fn test_lcg64xsh32_serde() {
+    use bincode;
+    use std::io::{BufWriter, BufReader};
+
+    let mut rng = Lcg64Xsh32::seed_from_u64(0);
+
+    let buf: Vec<u8> = Vec::new();
+    let mut buf = BufWriter::new(buf);
+    bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
+
+    let buf = buf.into_inner().unwrap();
+    let mut read = BufReader::new(&buf[..]);
+    let mut deserialized: Lcg64Xsh32 = bincode::deserialize_from(&mut read)
+        .expect("Could not deserialize");
+
+    for _ in 0..16 {
+        assert_eq!(rng.next_u64(), deserialized.next_u64());
+    }
+}
diff --git a/rand/rand_pcg/tests/mcg128xsl64.rs b/rand/rand_pcg/tests/mcg128xsl64.rs
new file mode 100644
index 0000000..2508917
--- /dev/null
+++ b/rand/rand_pcg/tests/mcg128xsl64.rs
@@ -0,0 +1,59 @@
+#![cfg(rust_1_26)]
+extern crate rand_pcg;
+extern crate rand_core;
+#[cfg(all(feature="serde1", test))] extern crate bincode;
+
+use rand_core::{RngCore, SeedableRng};
+use rand_pcg::{Mcg128Xsl64, Pcg64Mcg};
+
+#[test]
+fn test_mcg128xsl64_construction() {
+    // Test that various construction techniques produce a working RNG.
+    let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
+    let mut rng1 = Mcg128Xsl64::from_seed(seed);
+    assert_eq!(rng1.next_u64(), 7071994460355047496);
+
+    let mut rng2 = Mcg128Xsl64::from_rng(&mut rng1).unwrap();
+    assert_eq!(rng2.next_u64(), 12300796107712034932);
+
+    let mut rng3 = Mcg128Xsl64::seed_from_u64(0);
+    assert_eq!(rng3.next_u64(), 6198063878555692194);
+
+    // This is the same as Mcg128Xsl64, so we only have a single test:
+    let mut rng4 = Pcg64Mcg::seed_from_u64(0);
+    assert_eq!(rng4.next_u64(), 6198063878555692194);
+}
+
+#[test]
+fn test_mcg128xsl64_true_values() {
+    // Numbers copied from official test suite (C version).
+    let mut rng = Mcg128Xsl64::new(42);
+
+    let mut results = [0u64; 6];
+    for i in results.iter_mut() { *i = rng.next_u64(); }
+    let expected: [u64; 6] = [0x63b4a3a813ce700a, 0x382954200617ab24,
+        0xa7fd85ae3fe950ce, 0xd715286aa2887737, 0x60c92fee2e59f32c, 0x84c4e96beff30017];
+    assert_eq!(results, expected);
+}
+
+#[cfg(feature="serde1")]
+#[test]
+fn test_mcg128xsl64_serde() {
+    use bincode;
+    use std::io::{BufWriter, BufReader};
+
+    let mut rng = Mcg128Xsl64::seed_from_u64(0);
+
+    let buf: Vec<u8> = Vec::new();
+    let mut buf = BufWriter::new(buf);
+    bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
+
+    let buf = buf.into_inner().unwrap();
+    let mut read = BufReader::new(&buf[..]);
+    let mut deserialized: Mcg128Xsl64 = bincode::deserialize_from(&mut read)
+        .expect("Could not deserialize");
+
+    for _ in 0..16 {
+        assert_eq!(rng.next_u64(), deserialized.next_u64());
+    }
+}
diff --git a/rand/rand_xorshift/CHANGELOG.md b/rand/rand_xorshift/CHANGELOG.md
new file mode 100644
index 0000000..9a896a5
--- /dev/null
+++ b/rand/rand_xorshift/CHANGELOG.md
@@ -0,0 +1,8 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [0.1.0] - 2018-07-16
+- Pulled out of the Rand crate
diff --git a/rand/rand_xorshift/COPYRIGHT b/rand/rand_xorshift/COPYRIGHT
new file mode 100644
index 0000000..468d907
--- /dev/null
+++ b/rand/rand_xorshift/COPYRIGHT
@@ -0,0 +1,12 @@
+Copyrights in the Rand project are retained by their contributors. No
+copyright assignment is required to contribute to the Rand project.
+
+For full authorship information, see the version control history.
+
+Except as otherwise noted (below and/or in individual files), Rand is
+licensed under the Apache License, Version 2.0 <LICENSE-APACHE> or
+<http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+<LICENSE-MIT> or <http://opensource.org/licenses/MIT>, at your option.
+
+The Rand project includes code from the Rust project
+published under these same licenses.
diff --git a/rand/rand_xorshift/Cargo.toml b/rand/rand_xorshift/Cargo.toml
new file mode 100644
index 0000000..b763bfc
--- /dev/null
+++ b/rand/rand_xorshift/Cargo.toml
@@ -0,0 +1,31 @@
+[package]
+name = "rand_xorshift"
+version = "0.1.0"
+authors = ["The Rand Project Developers", "The Rust Project Developers"]
+license = "MIT/Apache-2.0"
+readme = "README.md"
+repository = "https://github.com/rust-random/rand"
+documentation = "https://rust-random.github.io/rand/rand_xorshift"
+homepage = "https://crates.io/crates/rand_xorshift"
+description = """
+Xorshift random number generator
+"""
+keywords = ["random", "rng", "xorshift"]
+categories = ["algorithms", "no-std"]
+
+[badges]
+travis-ci = { repository = "rust-random/rand" }
+appveyor = { repository = "rust-random/rand" }
+
+[features]
+serde1 = ["serde", "serde_derive"]
+
+[dependencies]
+rand_core = { path = "../rand_core", version = ">=0.2, <0.4", default-features=false }
+serde = { version = "1", optional = true }
+serde_derive = { version = "^1.0.38", optional = true }
+
+[dev-dependencies]
+# This is for testing serde, unfortunately we can't specify feature-gated dev
+# deps yet, see: https://github.com/rust-lang/cargo/issues/1596
+bincode = "1"
diff --git a/rand/rand_xorshift/LICENSE-APACHE b/rand/rand_xorshift/LICENSE-APACHE
new file mode 100644
index 0000000..17d7468
--- /dev/null
+++ b/rand/rand_xorshift/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     https://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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+6. Trademarks. This License does not grant permission to use the trade
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+Unless required by applicable law or agreed to in writing, software
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diff --git a/rand/rand_xorshift/LICENSE-MIT b/rand/rand_xorshift/LICENSE-MIT
new file mode 100644
index 0000000..d93b5ba
--- /dev/null
+++ b/rand/rand_xorshift/LICENSE-MIT
@@ -0,0 +1,26 @@
+Copyright 2018 Developers of the Rand project
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rand/rand_xorshift/README.md b/rand/rand_xorshift/README.md
new file mode 100644
index 0000000..573ee12
--- /dev/null
+++ b/rand/rand_xorshift/README.md
@@ -0,0 +1,45 @@
+# rand_xorshift
+
+[![Build Status](https://travis-ci.org/rust-random/rand.svg)](https://travis-ci.org/rust-random/rand)
+[![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-random/rand?svg=true)](https://ci.appveyor.com/project/rust-random/rand)
+[![Latest version](https://img.shields.io/crates/v/rand_xorshift.svg)](https://crates.io/crates/rand_xorshift)
+[![Book](https://img.shields.io/badge/book-master-yellow.svg)](https://rust-random.github.io/book/)
+[![API](https://img.shields.io/badge/api-master-yellow.svg)](https://rust-random.github.io/rand/rand_xorshift)
+[![API](https://docs.rs/rand_xorshift/badge.svg)](https://docs.rs/rand_xorshift)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.22+-lightgray.svg)](https://github.com/rust-random/rand#rust-version-requirements)
+
+Implements the Xorshift random number generator.
+
+The Xorshift[^1] algorithm is not suitable for cryptographic purposes
+but is very fast. If you do not know for sure that it fits your
+requirements, use a more secure one such as `StdRng` or `OsRng`.
+
+[^1]: Marsaglia, George (July 2003).
+      ["Xorshift RNGs"](https://www.jstatsoft.org/v08/i14/paper).
+      *Journal of Statistical Software*. Vol. 8 (Issue 14).
+
+Links:
+
+-   [API documentation (master)](https://rust-random.github.io/rand/rand_xorshift)
+-   [API documentation (docs.rs)](https://docs.rs/rand_xorshift)
+-   [Changelog](CHANGELOG.md)
+
+[rand]: https://crates.io/crates/rand
+
+
+## Crate Features
+
+`rand_xorshift` is `no_std` compatible. It does not require any functionality
+outside of the `core` lib, thus there are no features to configure.
+
+The `serde1` feature includes implementations of `Serialize` and `Deserialize`
+for the included RNGs.
+
+
+## License
+
+`rand_xorshift` is distributed under the terms of both the MIT license and the
+Apache License (Version 2.0).
+
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT), and
+[COPYRIGHT](COPYRIGHT) for details.
diff --git a/rand/rand_xorshift/src/lib.rs b/rand/rand_xorshift/src/lib.rs
new file mode 100644
index 0000000..aad74e4
--- /dev/null
+++ b/rand/rand_xorshift/src/lib.rs
@@ -0,0 +1,123 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The xorshift random number generator.
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico",
+       html_root_url = "https://rust-random.github.io/rand/")]
+
+#![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
+
+#![no_std]
+
+extern crate rand_core;
+
+#[cfg(feature="serde1")] extern crate serde;
+#[cfg(feature="serde1")] #[macro_use] extern crate serde_derive;
+
+use core::num::Wrapping as w;
+use core::{fmt, slice};
+use rand_core::{RngCore, SeedableRng, Error, impls, le};
+
+/// An Xorshift random number generator.
+///
+/// The Xorshift[^1] algorithm is not suitable for cryptographic purposes
+/// but is very fast. If you do not know for sure that it fits your
+/// requirements, use a more secure one such as `StdRng` or `OsRng`.
+///
+/// [^1]: Marsaglia, George (July 2003).
+///       ["Xorshift RNGs"](https://www.jstatsoft.org/v08/i14/paper).
+///       *Journal of Statistical Software*. Vol. 8 (Issue 14).
+#[derive(Clone)]
+#[cfg_attr(feature="serde1", derive(Serialize,Deserialize))]
+pub struct XorShiftRng {
+    x: w<u32>,
+    y: w<u32>,
+    z: w<u32>,
+    w: w<u32>,
+}
+
+// Custom Debug implementation that does not expose the internal state
+impl fmt::Debug for XorShiftRng {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "XorShiftRng {{}}")
+    }
+}
+
+impl RngCore for XorShiftRng {
+    #[inline]
+    fn next_u32(&mut self) -> u32 {
+        let x = self.x;
+        let t = x ^ (x << 11);
+        self.x = self.y;
+        self.y = self.z;
+        self.z = self.w;
+        let w_ = self.w;
+        self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
+        self.w.0
+    }
+
+    #[inline]
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_u32(self)
+    }
+
+    #[inline]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        impls::fill_bytes_via_next(self, dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
+
+impl SeedableRng for XorShiftRng {
+    type Seed = [u8; 16];
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        let mut seed_u32 = [0u32; 4];
+        le::read_u32_into(&seed, &mut seed_u32);
+
+        // Xorshift cannot be seeded with 0 and we cannot return an Error, but
+        // also do not wish to panic (because a random seed can legitimately be
+        // 0); our only option is therefore to use a preset value.
+        if seed_u32.iter().all(|&x| x == 0) {
+            seed_u32 = [0xBAD_5EED, 0xBAD_5EED, 0xBAD_5EED, 0xBAD_5EED];
+        }
+
+        XorShiftRng {
+            x: w(seed_u32[0]),
+            y: w(seed_u32[1]),
+            z: w(seed_u32[2]),
+            w: w(seed_u32[3]),
+        }
+    }
+
+    fn from_rng<R: RngCore>(mut rng: R) -> Result<Self, Error> {
+        let mut seed_u32 = [0u32; 4];
+        loop {
+            unsafe {
+                let ptr = seed_u32.as_mut_ptr() as *mut u8;
+
+                let slice = slice::from_raw_parts_mut(ptr, 4 * 4);
+                rng.try_fill_bytes(slice)?;
+            }
+            if !seed_u32.iter().all(|&x| x == 0) { break; }
+        }
+
+        Ok(XorShiftRng {
+            x: w(seed_u32[0]),
+            y: w(seed_u32[1]),
+            z: w(seed_u32[2]),
+            w: w(seed_u32[3]),
+        })
+    }
+}
diff --git a/rand/rand_xorshift/tests/mod.rs b/rand/rand_xorshift/tests/mod.rs
new file mode 100644
index 0000000..8374b64
--- /dev/null
+++ b/rand/rand_xorshift/tests/mod.rs
@@ -0,0 +1,92 @@
+extern crate rand_core;
+extern crate rand_xorshift;
+#[cfg(all(feature="serde1", test))] extern crate bincode;
+
+use rand_core::{RngCore, SeedableRng};
+use rand_xorshift::XorShiftRng;
+
+#[test]
+fn test_xorshift_construction() {
+    // Test that various construction techniques produce a working RNG.
+    let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
+    let mut rng1 = XorShiftRng::from_seed(seed);
+    assert_eq!(rng1.next_u64(), 4325440999699518727);
+
+    let _rng2 = XorShiftRng::from_rng(rng1).unwrap();
+    // Note: we cannot test the state of _rng2 because from_rng does not
+    // fix Endianness. This is allowed in the trait specification.
+}
+
+#[test]
+fn test_xorshift_true_values() {
+    let seed = [16,15,14,13, 12,11,10,9, 8,7,6,5, 4,3,2,1];
+    let mut rng = XorShiftRng::from_seed(seed);
+
+    let mut results = [0u32; 9];
+    for i in results.iter_mut() { *i = rng.next_u32(); }
+    let expected: [u32; 9] = [
+        2081028795, 620940381, 269070770, 16943764, 854422573, 29242889,
+        1550291885, 1227154591, 271695242];
+    assert_eq!(results, expected);
+
+    let mut results = [0u64; 9];
+    for i in results.iter_mut() { *i = rng.next_u64(); }
+    let expected: [u64; 9] = [
+        9247529084182843387, 8321512596129439293, 14104136531997710878,
+        6848554330849612046, 343577296533772213, 17828467390962600268,
+        9847333257685787782, 7717352744383350108, 1133407547287910111];
+    assert_eq!(results, expected);
+
+    let mut results = [0u8; 32];
+    rng.fill_bytes(&mut results);
+    let expected = [102, 57, 212, 16, 233, 130, 49, 183,
+                    158, 187, 44, 203, 63, 149, 45, 17,
+                    117, 129, 131, 160, 70, 121, 158, 155,
+                    224, 209, 192, 53, 10, 62, 57, 72];
+    assert_eq!(results, expected);
+}
+
+#[test]
+fn test_xorshift_zero_seed() {
+    // Xorshift does not work with an all zero seed.
+    // Assert it does not panic.
+    let seed = [0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+    let mut rng = XorShiftRng::from_seed(seed);
+    let a = rng.next_u64();
+    let b = rng.next_u64();
+    assert!(a != 0);
+    assert!(b != a);
+}
+
+#[test]
+fn test_xorshift_clone() {
+    let seed = [1,2,3,4, 5,5,7,8, 8,7,6,5, 4,3,2,1];
+    let mut rng1 = XorShiftRng::from_seed(seed);
+    let mut rng2 = rng1.clone();
+    for _ in 0..16 {
+        assert_eq!(rng1.next_u64(), rng2.next_u64());
+    }
+}
+
+#[cfg(feature="serde1")]
+#[test]
+fn test_xorshift_serde() {
+    use bincode;
+    use std::io::{BufWriter, BufReader};
+
+    let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16];
+    let mut rng = XorShiftRng::from_seed(seed);
+
+    let buf: Vec<u8> = Vec::new();
+    let mut buf = BufWriter::new(buf);
+    bincode::serialize_into(&mut buf, &rng).expect("Could not serialize");
+
+    let buf = buf.into_inner().unwrap();
+    let mut read = BufReader::new(&buf[..]);
+    let mut deserialized: XorShiftRng = bincode::deserialize_from(&mut read)
+        .expect("Could not deserialize");
+
+    for _ in 0..16 {
+        assert_eq!(rng.next_u64(), deserialized.next_u64());
+    }
+}
diff --git a/rand/src/deprecated.rs b/rand/src/deprecated.rs
new file mode 100644
index 0000000..985ae61
--- /dev/null
+++ b/rand/src/deprecated.rs
@@ -0,0 +1,611 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Deprecated re-exports (we can't add deprecation warnings otherwise)
+
+#![allow(deprecated)]
+
+use rngs;
+use {RngCore, CryptoRng, SeedableRng, Error};
+use rand_core::block::BlockRngCore;
+use rand_isaac;
+use rand_chacha;
+use rand_hc;
+
+#[cfg(feature="std")]
+use std::io::Read;
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0",
+    note="import from rand_isaac crate instead, or use the newer Hc128Rng")]
+pub struct IsaacRng(rand_isaac::IsaacRng);
+
+impl RngCore for IsaacRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for IsaacRng {
+    type Seed = <rand_isaac::IsaacRng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        IsaacRng(rand_isaac::IsaacRng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        rand_isaac::IsaacRng::from_rng(rng).map(IsaacRng)
+    }
+}
+
+impl IsaacRng {
+    pub fn new_from_u64(seed: u64) -> Self {
+        IsaacRng(rand_isaac::IsaacRng::new_from_u64(seed))
+    }
+}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0",
+    note="import from rand_isaac crate instead, or use newer Hc128Rng")]
+pub struct Isaac64Rng(rand_isaac::Isaac64Rng);
+
+impl RngCore for Isaac64Rng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for Isaac64Rng {
+    type Seed = <rand_isaac::Isaac64Rng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Isaac64Rng(rand_isaac::Isaac64Rng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        rand_isaac::Isaac64Rng::from_rng(rng).map(Isaac64Rng)
+    }
+}
+
+impl Isaac64Rng {
+    pub fn new_from_u64(seed: u64) -> Self {
+        Isaac64Rng(rand_isaac::Isaac64Rng::new_from_u64(seed))
+    }
+}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0", note="import from rand_chacha crate instead")]
+pub struct ChaChaRng(rand_chacha::ChaChaRng);
+
+impl RngCore for ChaChaRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for ChaChaRng {
+    type Seed = <rand_chacha::ChaChaRng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        ChaChaRng(rand_chacha::ChaChaRng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        rand_chacha::ChaChaRng::from_rng(rng).map(ChaChaRng)
+    }
+}
+
+impl ChaChaRng {
+    #[cfg(rust_1_26)]
+    pub fn get_word_pos(&self) -> u128 {
+        self.0.get_word_pos()
+    }
+
+    #[cfg(rust_1_26)]
+    pub fn set_word_pos(&mut self, word_offset: u128) {
+        self.0.set_word_pos(word_offset)
+    }
+
+    pub fn set_stream(&mut self, stream: u64) {
+        self.0.set_stream(stream)
+    }
+}
+
+impl CryptoRng for ChaChaRng {}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0", note="import from rand_hc crate instead")]
+pub struct Hc128Rng(rand_hc::Hc128Rng);
+
+impl RngCore for Hc128Rng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for Hc128Rng {
+    type Seed = <rand_hc::Hc128Rng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        Hc128Rng(rand_hc::Hc128Rng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        rand_hc::Hc128Rng::from_rng(rng).map(Hc128Rng)
+    }
+}
+
+impl CryptoRng for Hc128Rng {}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0", note="import from rand_xorshift crate instead")]
+pub struct XorShiftRng(::rand_xorshift::XorShiftRng);
+
+impl RngCore for XorShiftRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for XorShiftRng {
+    type Seed = <::rand_xorshift::XorShiftRng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        XorShiftRng(::rand_xorshift::XorShiftRng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        ::rand_xorshift::XorShiftRng::from_rng(rng).map(XorShiftRng)
+    }
+}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0",
+    note="import with rand::prelude::* or rand::rngs::StdRng instead")]
+pub struct StdRng(rngs::StdRng);
+
+impl RngCore for StdRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for StdRng {
+    type Seed = <rngs::StdRng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        StdRng(rngs::StdRng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        rngs::StdRng::from_rng(rng).map(StdRng)
+    }
+}
+
+impl CryptoRng for StdRng {}
+
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0", note="import with rand::rngs::OsRng instead")]
+pub struct OsRng(rngs::OsRng);
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[cfg(feature="std")]
+impl RngCore for OsRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[cfg(feature="std")]
+impl OsRng {
+    pub fn new() -> Result<Self, Error> {
+        rngs::OsRng::new().map(OsRng)
+    }
+}
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[cfg(feature="std")]
+impl CryptoRng for OsRng {}
+
+
+#[cfg(feature="std")]
+#[derive(Debug)]
+#[deprecated(since="0.6.0", note="import with rand::rngs::EntropyRng instead")]
+pub struct EntropyRng(rngs::EntropyRng);
+
+#[cfg(feature="std")]
+impl RngCore for EntropyRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(feature="std")]
+impl EntropyRng {
+    pub fn new() -> Self {
+        EntropyRng(rngs::EntropyRng::new())
+    }
+}
+
+#[cfg(feature="std")]
+impl Default for EntropyRng {
+    fn default() -> Self {
+        EntropyRng::new()
+    }
+}
+
+#[cfg(feature="std")]
+impl CryptoRng for EntropyRng {}
+
+
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0", note="import with rand::rngs::JitterRng instead")]
+pub struct JitterRng(rngs::JitterRng);
+
+impl RngCore for JitterRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl JitterRng {
+    #[cfg(all(feature="std", not(target_arch = "wasm32")))]
+    pub fn new() -> Result<JitterRng, rngs::TimerError> {
+        rngs::JitterRng::new().map(JitterRng)
+    }
+
+    pub fn new_with_timer(timer: fn() -> u64) -> JitterRng {
+        JitterRng(rngs::JitterRng::new_with_timer(timer))
+    }
+
+    pub fn set_rounds(&mut self, rounds: u8) {
+        self.0.set_rounds(rounds)
+    }
+
+    pub fn test_timer(&mut self) -> Result<u8, rngs::TimerError> {
+        self.0.test_timer()
+    }
+
+    #[cfg(feature="std")]
+    pub fn timer_stats(&mut self, var_rounds: bool) -> i64 {
+        self.0.timer_stats(var_rounds)
+    }
+}
+
+impl CryptoRng for JitterRng {}
+
+
+#[cfg(feature="std")]
+#[derive(Clone, Debug)]
+#[deprecated(since="0.6.0",
+    note="import with rand::prelude::* or rand::rngs::ThreadRng instead")]
+pub struct ThreadRng(rngs::ThreadRng);
+
+#[cfg(feature="std")]
+impl RngCore for ThreadRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(feature="std")]
+impl CryptoRng for ThreadRng {}
+
+
+#[cfg(feature="std")]
+#[derive(Debug)]
+#[deprecated(since="0.6.0", note="import with rand::rngs::adapter::ReadRng instead")]
+pub struct ReadRng<R>(rngs::adapter::ReadRng<R>);
+
+#[cfg(feature="std")]
+impl<R: Read> RngCore for ReadRng<R> {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    #[inline(always)]
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    #[inline(always)]
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(feature="std")]
+impl<R: Read> ReadRng<R> {
+    pub fn new(r: R) -> ReadRng<R> {
+        ReadRng(rngs::adapter::ReadRng::new(r))
+    }
+}
+
+
+#[derive(Clone, Debug)]
+pub struct ReseedingRng<R, Rsdr>(rngs::adapter::ReseedingRng<R, Rsdr>)
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore;
+
+impl<R, Rsdr: RngCore> RngCore for ReseedingRng<R, Rsdr>
+where R: BlockRngCore<Item = u32> + SeedableRng,
+    <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
+{
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl<R, Rsdr> ReseedingRng<R, Rsdr>
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore
+{
+    pub fn new(rng: R, threshold: u64, reseeder: Rsdr) -> Self {
+        ReseedingRng(rngs::adapter::ReseedingRng::new(rng, threshold, reseeder))
+    }
+
+    pub fn reseed(&mut self) -> Result<(), Error> {
+        self.0.reseed()
+    }
+}
+
+impl<R, Rsdr> CryptoRng for ReseedingRng<R, Rsdr>
+where R: BlockRngCore + SeedableRng + CryptoRng,
+      Rsdr: RngCore + CryptoRng {}
diff --git a/rand/src/distributions/bernoulli.rs b/rand/src/distributions/bernoulli.rs
new file mode 100644
index 0000000..f49618c
--- /dev/null
+++ b/rand/src/distributions/bernoulli.rs
@@ -0,0 +1,165 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Bernoulli distribution.
+
+use Rng;
+use distributions::Distribution;
+
+/// The Bernoulli distribution.
+///
+/// This is a special case of the Binomial distribution where `n = 1`.
+///
+/// # Example
+///
+/// ```rust
+/// use rand::distributions::{Bernoulli, Distribution};
+///
+/// let d = Bernoulli::new(0.3);
+/// let v = d.sample(&mut rand::thread_rng());
+/// println!("{} is from a Bernoulli distribution", v);
+/// ```
+///
+/// # Precision
+///
+/// This `Bernoulli` distribution uses 64 bits from the RNG (a `u64`),
+/// so only probabilities that are multiples of 2<sup>-64</sup> can be
+/// represented.
+#[derive(Clone, Copy, Debug)]
+pub struct Bernoulli {
+    /// Probability of success, relative to the maximal integer.
+    p_int: u64,
+}
+
+// To sample from the Bernoulli distribution we use a method that compares a
+// random `u64` value `v < (p * 2^64)`.
+//
+// If `p == 1.0`, the integer `v` to compare against can not represented as a
+// `u64`. We manually set it to `u64::MAX` instead (2^64 - 1 instead of 2^64).
+// Note that  value of `p < 1.0` can never result in `u64::MAX`, because an
+// `f64` only has 53 bits of precision, and the next largest value of `p` will
+// result in `2^64 - 2048`.
+//
+// Also there is a 100% theoretical concern: if someone consistenly wants to
+// generate `true` using the Bernoulli distribution (i.e. by using a probability
+// of `1.0`), just using `u64::MAX` is not enough. On average it would return
+// false once every 2^64 iterations. Some people apparently care about this
+// case.
+//
+// That is why we special-case `u64::MAX` to always return `true`, without using
+// the RNG, and pay the performance price for all uses that *are* reasonable.
+// Luckily, if `new()` and `sample` are close, the compiler can optimize out the
+// extra check.
+const ALWAYS_TRUE: u64 = ::core::u64::MAX;
+
+// This is just `2.0.powi(64)`, but written this way because it is not available
+// in `no_std` mode.
+const SCALE: f64 = 2.0 * (1u64 << 63) as f64;
+
+impl Bernoulli {
+    /// Construct a new `Bernoulli` with the given probability of success `p`.
+    ///
+    /// # Panics
+    ///
+    /// If `p < 0` or `p > 1`.
+    ///
+    /// # Precision
+    ///
+    /// For `p = 1.0`, the resulting distribution will always generate true.
+    /// For `p = 0.0`, the resulting distribution will always generate false.
+    ///
+    /// This method is accurate for any input `p` in the range `[0, 1]` which is
+    /// a multiple of 2<sup>-64</sup>. (Note that not all multiples of
+    /// 2<sup>-64</sup> in `[0, 1]` can be represented as a `f64`.)
+    #[inline]
+    pub fn new(p: f64) -> Bernoulli {
+        if p < 0.0 || p >= 1.0 {
+            if p == 1.0 { return Bernoulli { p_int: ALWAYS_TRUE } }
+            panic!("Bernoulli::new not called with 0.0 <= p <= 1.0");
+        }
+        Bernoulli { p_int: (p * SCALE) as u64 }
+    }
+
+    /// Construct a new `Bernoulli` with the probability of success of
+    /// `numerator`-in-`denominator`. I.e. `new_ratio(2, 3)` will return
+    /// a `Bernoulli` with a 2-in-3 chance, or about 67%, of returning `true`.
+    ///
+    /// If `numerator == denominator` then the returned `Bernoulli` will always
+    /// return `true`. If `numerator == 0` it will always return `false`.
+    ///
+    /// # Panics
+    ///
+    /// If `denominator == 0` or `numerator > denominator`.
+    ///
+    #[inline]
+    pub fn from_ratio(numerator: u32, denominator: u32) -> Bernoulli {
+        assert!(numerator <= denominator);
+        if numerator == denominator {
+            return Bernoulli { p_int: ::core::u64::MAX }
+        }
+        let p_int = ((numerator as f64 / denominator as f64) * SCALE) as u64;
+        Bernoulli { p_int }
+    }
+}
+
+impl Distribution<bool> for Bernoulli {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> bool {
+        // Make sure to always return true for p = 1.0.
+        if self.p_int == ALWAYS_TRUE { return true; }
+        let v: u64 = rng.gen();
+        v < self.p_int
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use Rng;
+    use distributions::Distribution;
+    use super::Bernoulli;
+
+    #[test]
+    fn test_trivial() {
+        let mut r = ::test::rng(1);
+        let always_false = Bernoulli::new(0.0);
+        let always_true = Bernoulli::new(1.0);
+        for _ in 0..5 {
+            assert_eq!(r.sample::<bool, _>(&always_false), false);
+            assert_eq!(r.sample::<bool, _>(&always_true), true);
+            assert_eq!(Distribution::<bool>::sample(&always_false, &mut r), false);
+            assert_eq!(Distribution::<bool>::sample(&always_true, &mut r), true);
+        }
+    }
+
+    #[test]
+    fn test_average() {
+        const P: f64 = 0.3;
+        const NUM: u32 = 3;
+        const DENOM: u32 = 10;
+        let d1 = Bernoulli::new(P);
+        let d2 = Bernoulli::from_ratio(NUM, DENOM);
+        const N: u32 = 100_000;
+
+        let mut sum1: u32 = 0;
+        let mut sum2: u32 = 0;
+        let mut rng = ::test::rng(2);
+        for _ in 0..N {
+            if d1.sample(&mut rng) {
+                sum1 += 1;
+            }
+            if d2.sample(&mut rng) {
+                sum2 += 1;
+            }
+        }
+        let avg1 = (sum1 as f64) / (N as f64);
+        assert!((avg1 - P).abs() < 5e-3);
+
+        let avg2 = (sum2 as f64) / (N as f64);
+        assert!((avg2 - (NUM as f64)/(DENOM as f64)).abs() < 5e-3);
+    }
+}
diff --git a/rand/src/distributions/binomial.rs b/rand/src/distributions/binomial.rs
new file mode 100644
index 0000000..2df393e
--- /dev/null
+++ b/rand/src/distributions/binomial.rs
@@ -0,0 +1,177 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2016-2017 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The binomial distribution.
+
+use Rng;
+use distributions::{Distribution, Bernoulli, Cauchy};
+use distributions::utils::log_gamma;
+
+/// The binomial distribution `Binomial(n, p)`.
+///
+/// This distribution has density function:
+/// `f(k) = n!/(k! (n-k)!) p^k (1-p)^(n-k)` for `k >= 0`.
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Binomial, Distribution};
+///
+/// let bin = Binomial::new(20, 0.3);
+/// let v = bin.sample(&mut rand::thread_rng());
+/// println!("{} is from a binomial distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Binomial {
+    /// Number of trials.
+    n: u64,
+    /// Probability of success.
+    p: f64,
+}
+
+impl Binomial {
+    /// Construct a new `Binomial` with the given shape parameters `n` (number
+    /// of trials) and `p` (probability of success).
+    ///
+    /// Panics if `p < 0` or `p > 1`.
+    pub fn new(n: u64, p: f64) -> Binomial {
+        assert!(p >= 0.0, "Binomial::new called with p < 0");
+        assert!(p <= 1.0, "Binomial::new called with p > 1");
+        Binomial { n, p }
+    }
+}
+
+impl Distribution<u64> for Binomial {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64 {
+        // Handle these values directly.
+        if self.p == 0.0 {
+            return 0;
+        } else if self.p == 1.0 {
+            return self.n;
+        }
+        
+        // For low n, it is faster to sample directly. For both methods,
+        // performance is independent of p. On Intel Haswell CPU this method
+        // appears to be faster for approx n < 300.
+        if self.n < 300 {
+            let mut result = 0;
+            let d = Bernoulli::new(self.p);
+            for _ in 0 .. self.n {
+                result += rng.sample(d) as u32;
+            }
+            return result as u64;
+        }
+        
+        // binomial distribution is symmetrical with respect to p -> 1-p, k -> n-k
+        // switch p so that it is less than 0.5 - this allows for lower expected values
+        // we will just invert the result at the end
+        let p = if self.p <= 0.5 {
+            self.p
+        } else {
+            1.0 - self.p
+        };
+
+        // prepare some cached values
+        let float_n = self.n as f64;
+        let ln_fact_n = log_gamma(float_n + 1.0);
+        let pc = 1.0 - p;
+        let log_p = p.ln();
+        let log_pc = pc.ln();
+        let expected = self.n as f64 * p;
+        let sq = (expected * (2.0 * pc)).sqrt();
+
+        let mut lresult;
+
+        // we use the Cauchy distribution as the comparison distribution
+        // f(x) ~ 1/(1+x^2)
+        let cauchy = Cauchy::new(0.0, 1.0);
+        loop {
+            let mut comp_dev: f64;
+            loop {
+                // draw from the Cauchy distribution
+                comp_dev = rng.sample(cauchy);
+                // shift the peak of the comparison ditribution
+                lresult = expected + sq * comp_dev;
+                // repeat the drawing until we are in the range of possible values
+                if lresult >= 0.0 && lresult < float_n + 1.0 {
+                    break;
+                }
+            }
+
+            // the result should be discrete
+            lresult = lresult.floor();
+
+            let log_binomial_dist = ln_fact_n - log_gamma(lresult+1.0) -
+                log_gamma(float_n - lresult + 1.0) + lresult*log_p + (float_n - lresult)*log_pc;
+            // this is the binomial probability divided by the comparison probability
+            // we will generate a uniform random value and if it is larger than this,
+            // we interpret it as a value falling out of the distribution and repeat
+            let comparison_coeff = (log_binomial_dist.exp() * sq) * (1.2 * (1.0 + comp_dev*comp_dev));
+
+            if comparison_coeff >= rng.gen() {
+                break;
+            }
+        }
+
+        // invert the result for p < 0.5
+        if p != self.p {
+            self.n - lresult as u64
+        } else {
+            lresult as u64
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use Rng;
+    use distributions::Distribution;
+    use super::Binomial;
+
+    fn test_binomial_mean_and_variance<R: Rng>(n: u64, p: f64, rng: &mut R) {
+        let binomial = Binomial::new(n, p);
+
+        let expected_mean = n as f64 * p;
+        let expected_variance = n as f64 * p * (1.0 - p);
+
+        let mut results = [0.0; 1000];
+        for i in results.iter_mut() { *i = binomial.sample(rng) as f64; }
+
+        let mean = results.iter().sum::<f64>() / results.len() as f64;
+        assert!((mean as f64 - expected_mean).abs() < expected_mean / 50.0);
+
+        let variance =
+            results.iter().map(|x| (x - mean) * (x - mean)).sum::<f64>()
+            / results.len() as f64;
+        assert!((variance - expected_variance).abs() < expected_variance / 10.0);
+    }
+
+    #[test]
+    fn test_binomial() {
+        let mut rng = ::test::rng(351);
+        test_binomial_mean_and_variance(150, 0.1, &mut rng);
+        test_binomial_mean_and_variance(70, 0.6, &mut rng);
+        test_binomial_mean_and_variance(40, 0.5, &mut rng);
+        test_binomial_mean_and_variance(20, 0.7, &mut rng);
+        test_binomial_mean_and_variance(20, 0.5, &mut rng);
+    }
+
+    #[test]
+    fn test_binomial_end_points() {
+        let mut rng = ::test::rng(352);
+        assert_eq!(rng.sample(Binomial::new(20, 0.0)), 0);
+        assert_eq!(rng.sample(Binomial::new(20, 1.0)), 20);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_binomial_invalid_lambda_neg() {
+        Binomial::new(20, -10.0);
+    }
+}
diff --git a/rand/src/distributions/cauchy.rs b/rand/src/distributions/cauchy.rs
new file mode 100644
index 0000000..feef015
--- /dev/null
+++ b/rand/src/distributions/cauchy.rs
@@ -0,0 +1,115 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2016-2017 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Cauchy distribution.
+
+use Rng;
+use distributions::Distribution;
+use std::f64::consts::PI;
+
+/// The Cauchy distribution `Cauchy(median, scale)`.
+///
+/// This distribution has a density function:
+/// `f(x) = 1 / (pi * scale * (1 + ((x - median) / scale)^2))`
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Cauchy, Distribution};
+///
+/// let cau = Cauchy::new(2.0, 5.0);
+/// let v = cau.sample(&mut rand::thread_rng());
+/// println!("{} is from a Cauchy(2, 5) distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Cauchy {
+    median: f64,
+    scale: f64
+}
+
+impl Cauchy {
+    /// Construct a new `Cauchy` with the given shape parameters
+    /// `median` the peak location and `scale` the scale factor.
+    /// Panics if `scale <= 0`.
+    pub fn new(median: f64, scale: f64) -> Cauchy {
+        assert!(scale > 0.0, "Cauchy::new called with scale factor <= 0");
+        Cauchy {
+            median,
+            scale
+        }
+    }
+}
+
+impl Distribution<f64> for Cauchy {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        // sample from [0, 1)
+        let x = rng.gen::<f64>();
+        // get standard cauchy random number
+        // note that π/2 is not exactly representable, even if x=0.5 the result is finite
+        let comp_dev = (PI * x).tan();
+        // shift and scale according to parameters
+        let result = self.median + self.scale * comp_dev;
+        result
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use distributions::Distribution;
+    use super::Cauchy;
+
+    fn median(mut numbers: &mut [f64]) -> f64 {
+        sort(&mut numbers);
+        let mid = numbers.len() / 2;
+        numbers[mid]
+    }
+
+    fn sort(numbers: &mut [f64]) {
+        numbers.sort_by(|a, b| a.partial_cmp(b).unwrap());
+    }
+
+    #[test]
+    fn test_cauchy_median() {
+        let cauchy = Cauchy::new(10.0, 5.0);
+        let mut rng = ::test::rng(123);
+        let mut numbers: [f64; 1000] = [0.0; 1000];
+        for i in 0..1000 {
+            numbers[i] = cauchy.sample(&mut rng);
+        }
+        let median = median(&mut numbers);
+        println!("Cauchy median: {}", median);
+        assert!((median - 10.0).abs() < 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    fn test_cauchy_mean() {
+        let cauchy = Cauchy::new(10.0, 5.0);
+        let mut rng = ::test::rng(123);
+        let mut sum = 0.0;
+        for _ in 0..1000 {
+            sum += cauchy.sample(&mut rng);
+        }
+        let mean = sum / 1000.0;
+        println!("Cauchy mean: {}", mean);
+        // for a Cauchy distribution the mean should not converge
+        assert!((mean - 10.0).abs() > 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_cauchy_invalid_scale_zero() {
+        Cauchy::new(0.0, 0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_cauchy_invalid_scale_neg() {
+        Cauchy::new(0.0, -10.0);
+    }
+}
diff --git a/rand/src/distributions/dirichlet.rs b/rand/src/distributions/dirichlet.rs
new file mode 100644
index 0000000..19384b8
--- /dev/null
+++ b/rand/src/distributions/dirichlet.rs
@@ -0,0 +1,137 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The dirichlet distribution.
+
+use Rng;
+use distributions::Distribution;
+use distributions::gamma::Gamma;
+
+/// The dirichelet distribution `Dirichlet(alpha)`.
+///
+/// The Dirichlet distribution is a family of continuous multivariate
+/// probability distributions parameterized by a vector alpha of positive reals.
+/// It is a multivariate generalization of the beta distribution.
+///
+/// # Example
+///
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::Dirichlet;
+///
+/// let dirichlet = Dirichlet::new(vec![1.0, 2.0, 3.0]);
+/// let samples = dirichlet.sample(&mut rand::thread_rng());
+/// println!("{:?} is from a Dirichlet([1.0, 2.0, 3.0]) distribution", samples);
+/// ```
+
+#[derive(Clone, Debug)]
+pub struct Dirichlet {
+    /// Concentration parameters (alpha)
+    alpha: Vec<f64>,
+}
+
+impl Dirichlet {
+    /// Construct a new `Dirichlet` with the given alpha parameter `alpha`.
+    ///
+    /// # Panics
+    /// - if `alpha.len() < 2`
+    ///
+    #[inline]
+    pub fn new<V: Into<Vec<f64>>>(alpha: V) -> Dirichlet {
+        let a = alpha.into();
+        assert!(a.len() > 1);
+        for i in 0..a.len() {
+            assert!(a[i] > 0.0);
+        }
+
+        Dirichlet { alpha: a }
+    }
+
+    /// Construct a new `Dirichlet` with the given shape parameter `alpha` and `size`.
+    ///
+    /// # Panics
+    /// - if `alpha <= 0.0`
+    /// - if `size < 2`
+    ///
+    #[inline]
+    pub fn new_with_param(alpha: f64, size: usize) -> Dirichlet {
+        assert!(alpha > 0.0);
+        assert!(size > 1);
+        Dirichlet {
+            alpha: vec![alpha; size],
+        }
+    }
+}
+
+impl Distribution<Vec<f64>> for Dirichlet {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Vec<f64> {
+        let n = self.alpha.len();
+        let mut samples = vec![0.0f64; n];
+        let mut sum = 0.0f64;
+
+        for i in 0..n {
+            let g = Gamma::new(self.alpha[i], 1.0);
+            samples[i] = g.sample(rng);
+            sum += samples[i];
+        }
+        let invacc = 1.0 / sum;
+        for i in 0..n {
+            samples[i] *= invacc;
+        }
+        samples
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Dirichlet;
+    use distributions::Distribution;
+
+    #[test]
+    fn test_dirichlet() {
+        let d = Dirichlet::new(vec![1.0, 2.0, 3.0]);
+        let mut rng = ::test::rng(221);
+        let samples = d.sample(&mut rng);
+        let _: Vec<f64> = samples
+            .into_iter()
+            .map(|x| {
+                assert!(x > 0.0);
+                x
+            })
+            .collect();
+    }
+
+    #[test]
+    fn test_dirichlet_with_param() {
+        let alpha = 0.5f64;
+        let size = 2;
+        let d = Dirichlet::new_with_param(alpha, size);
+        let mut rng = ::test::rng(221);
+        let samples = d.sample(&mut rng);
+        let _: Vec<f64> = samples
+            .into_iter()
+            .map(|x| {
+                assert!(x > 0.0);
+                x
+            })
+            .collect();
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_dirichlet_invalid_length() {
+        Dirichlet::new_with_param(0.5f64, 1);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_dirichlet_invalid_alpha() {
+        Dirichlet::new_with_param(0.0f64, 2);
+    }
+}
diff --git a/rand/src/distributions/exponential.rs b/rand/src/distributions/exponential.rs
index c3c924c..a7d0500 100644
--- a/rand/src/distributions/exponential.rs
+++ b/rand/src/distributions/exponential.rs
@@ -1,74 +1,78 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
 //! The exponential distribution.
 
-use {Rng, Rand};
-use distributions::{ziggurat, ziggurat_tables, Sample, IndependentSample};
+use {Rng};
+use distributions::{ziggurat_tables, Distribution};
+use distributions::utils::ziggurat;
 
-/// A wrapper around an `f64` to generate Exp(1) random numbers.
+/// Samples floating-point numbers according to the exponential distribution,
+/// with rate parameter `λ = 1`. This is equivalent to `Exp::new(1.0)` or
+/// sampling with `-rng.gen::<f64>().ln()`, but faster.
 ///
 /// See `Exp` for the general exponential distribution.
 ///
-/// Implemented via the ZIGNOR variant[1] of the Ziggurat method. The
-/// exact description in the paper was adjusted to use tables for the
-/// exponential distribution rather than normal.
+/// Implemented via the ZIGNOR variant[^1] of the Ziggurat method. The exact
+/// description in the paper was adjusted to use tables for the exponential
+/// distribution rather than normal.
 ///
-/// [1]: Jurgen A. Doornik (2005). [*An Improved Ziggurat Method to
-/// Generate Normal Random
-/// Samples*](http://www.doornik.com/research/ziggurat.pdf). Nuffield
-/// College, Oxford
+/// [^1]: Jurgen A. Doornik (2005). [*An Improved Ziggurat Method to
+///       Generate Normal Random Samples*](
+///       https://www.doornik.com/research/ziggurat.pdf).
+///       Nuffield College, Oxford
 ///
 /// # Example
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::Exp1;
 ///
-/// ```rust
-/// use rand::distributions::exponential::Exp1;
-///
-/// let Exp1(x) = rand::random();
-/// println!("{}", x);
+/// let val: f64 = SmallRng::from_entropy().sample(Exp1);
+/// println!("{}", val);
 /// ```
 #[derive(Clone, Copy, Debug)]
-pub struct Exp1(pub f64);
+pub struct Exp1;
 
 // This could be done via `-rng.gen::<f64>().ln()` but that is slower.
-impl Rand for Exp1 {
+impl Distribution<f64> for Exp1 {
     #[inline]
-    fn rand<R:Rng>(rng: &mut R) -> Exp1 {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
         #[inline]
         fn pdf(x: f64) -> f64 {
             (-x).exp()
         }
         #[inline]
-        fn zero_case<R:Rng>(rng: &mut R, _u: f64) -> f64 {
+        fn zero_case<R: Rng + ?Sized>(rng: &mut R, _u: f64) -> f64 {
             ziggurat_tables::ZIG_EXP_R - rng.gen::<f64>().ln()
         }
 
-        Exp1(ziggurat(rng, false,
-                      &ziggurat_tables::ZIG_EXP_X,
-                      &ziggurat_tables::ZIG_EXP_F,
-                      pdf, zero_case))
+        ziggurat(rng, false,
+                 &ziggurat_tables::ZIG_EXP_X,
+                 &ziggurat_tables::ZIG_EXP_F,
+                 pdf, zero_case)
     }
 }
 
 /// The exponential distribution `Exp(lambda)`.
 ///
-/// This distribution has density function: `f(x) = lambda *
-/// exp(-lambda * x)` for `x > 0`.
+/// This distribution has density function: `f(x) = lambda * exp(-lambda * x)`
+/// for `x > 0`.
+/// 
+/// Note that [`Exp1`](struct.Exp1.html) is an optimised implementation for `lambda = 1`.
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{Exp, IndependentSample};
+/// ```
+/// use rand::distributions::{Exp, Distribution};
 ///
 /// let exp = Exp::new(2.0);
-/// let v = exp.ind_sample(&mut rand::thread_rng());
+/// let v = exp.sample(&mut rand::thread_rng());
 /// println!("{} is from a Exp(2) distribution", v);
 /// ```
 #[derive(Clone, Copy, Debug)]
@@ -87,28 +91,24 @@ impl Exp {
     }
 }
 
-impl Sample<f64> for Exp {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl IndependentSample<f64> for Exp {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        let Exp1(n) = rng.gen::<Exp1>();
+impl Distribution<f64> for Exp {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let n: f64 = rng.sample(Exp1);
         n * self.lambda_inverse
     }
 }
 
 #[cfg(test)]
 mod test {
-    use distributions::{Sample, IndependentSample};
+    use distributions::Distribution;
     use super::Exp;
 
     #[test]
     fn test_exp() {
-        let mut exp = Exp::new(10.0);
-        let mut rng = ::test::rng();
+        let exp = Exp::new(10.0);
+        let mut rng = ::test::rng(221);
         for _ in 0..1000 {
             assert!(exp.sample(&mut rng) >= 0.0);
-            assert!(exp.ind_sample(&mut rng) >= 0.0);
         }
     }
     #[test]
diff --git a/rand/src/distributions/float.rs b/rand/src/distributions/float.rs
new file mode 100644
index 0000000..ece12f5
--- /dev/null
+++ b/rand/src/distributions/float.rs
@@ -0,0 +1,259 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Basic floating-point number distributions
+
+use core::mem;
+use Rng;
+use distributions::{Distribution, Standard};
+use distributions::utils::FloatSIMDUtils;
+#[cfg(feature="simd_support")]
+use packed_simd::*;
+
+/// A distribution to sample floating point numbers uniformly in the half-open
+/// interval `(0, 1]`, i.e. including 1 but not 0.
+///
+/// All values that can be generated are of the form `n * ε/2`. For `f32`
+/// the 23 most significant random bits of a `u32` are used and for `f64` the
+/// 53 most significant bits of a `u64` are used. The conversion uses the
+/// multiplicative method.
+///
+/// See also: [`Standard`] which samples from `[0, 1)`, [`Open01`]
+/// which samples from `(0, 1)` and [`Uniform`] which samples from arbitrary
+/// ranges.
+///
+/// # Example
+/// ```
+/// use rand::{thread_rng, Rng};
+/// use rand::distributions::OpenClosed01;
+///
+/// let val: f32 = thread_rng().sample(OpenClosed01);
+/// println!("f32 from (0, 1): {}", val);
+/// ```
+///
+/// [`Standard`]: struct.Standard.html
+/// [`Open01`]: struct.Open01.html
+/// [`Uniform`]: uniform/struct.Uniform.html
+#[derive(Clone, Copy, Debug)]
+pub struct OpenClosed01;
+
+/// A distribution to sample floating point numbers uniformly in the open
+/// interval `(0, 1)`, i.e. not including either endpoint.
+///
+/// All values that can be generated are of the form `n * ε + ε/2`. For `f32`
+/// the 22 most significant random bits of an `u32` are used, for `f64` 52 from
+/// an `u64`. The conversion uses a transmute-based method.
+///
+/// See also: [`Standard`] which samples from `[0, 1)`, [`OpenClosed01`]
+/// which samples from `(0, 1]` and [`Uniform`] which samples from arbitrary
+/// ranges.
+///
+/// # Example
+/// ```
+/// use rand::{thread_rng, Rng};
+/// use rand::distributions::Open01;
+///
+/// let val: f32 = thread_rng().sample(Open01);
+/// println!("f32 from (0, 1): {}", val);
+/// ```
+///
+/// [`Standard`]: struct.Standard.html
+/// [`OpenClosed01`]: struct.OpenClosed01.html
+/// [`Uniform`]: uniform/struct.Uniform.html
+#[derive(Clone, Copy, Debug)]
+pub struct Open01;
+
+
+pub(crate) trait IntoFloat {
+    type F;
+
+    /// Helper method to combine the fraction and a contant exponent into a
+    /// float.
+    ///
+    /// Only the least significant bits of `self` may be set, 23 for `f32` and
+    /// 52 for `f64`.
+    /// The resulting value will fall in a range that depends on the exponent.
+    /// As an example the range with exponent 0 will be
+    /// [2<sup>0</sup>..2<sup>1</sup>), which is [1..2).
+    fn into_float_with_exponent(self, exponent: i32) -> Self::F;
+}
+
+macro_rules! float_impls {
+    ($ty:ident, $uty:ident, $f_scalar:ident, $u_scalar:ty,
+     $fraction_bits:expr, $exponent_bias:expr) => {
+        impl IntoFloat for $uty {
+            type F = $ty;
+            #[inline(always)]
+            fn into_float_with_exponent(self, exponent: i32) -> $ty {
+                // The exponent is encoded using an offset-binary representation
+                let exponent_bits: $u_scalar =
+                    (($exponent_bias + exponent) as $u_scalar) << $fraction_bits;
+                // TODO: use from_bits when min compiler > 1.25 (see #545)
+                // $ty::from_bits(self | exponent_bits)
+                unsafe{ mem::transmute(self | exponent_bits) }
+            }
+        }
+
+        impl Distribution<$ty> for Standard {
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
+                // Multiply-based method; 24/53 random bits; [0, 1) interval.
+                // We use the most significant bits because for simple RNGs
+                // those are usually more random.
+                let float_size = mem::size_of::<$f_scalar>() as u32 * 8;
+                let precision = $fraction_bits + 1;
+                let scale = 1.0 / ((1 as $u_scalar << precision) as $f_scalar);
+
+                let value: $uty = rng.gen();
+                let value = value >> (float_size - precision);
+                scale * $ty::cast_from_int(value)
+            }
+        }
+
+        impl Distribution<$ty> for OpenClosed01 {
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
+                // Multiply-based method; 24/53 random bits; (0, 1] interval.
+                // We use the most significant bits because for simple RNGs
+                // those are usually more random.
+                let float_size = mem::size_of::<$f_scalar>() as u32 * 8;
+                let precision = $fraction_bits + 1;
+                let scale = 1.0 / ((1 as $u_scalar << precision) as $f_scalar);
+
+                let value: $uty = rng.gen();
+                let value = value >> (float_size - precision);
+                // Add 1 to shift up; will not overflow because of right-shift:
+                scale * $ty::cast_from_int(value + 1)
+            }
+        }
+
+        impl Distribution<$ty> for Open01 {
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
+                // Transmute-based method; 23/52 random bits; (0, 1) interval.
+                // We use the most significant bits because for simple RNGs
+                // those are usually more random.
+                use core::$f_scalar::EPSILON;
+                let float_size = mem::size_of::<$f_scalar>() as u32 * 8;
+
+                let value: $uty = rng.gen();
+                let fraction = value >> (float_size - $fraction_bits);
+                fraction.into_float_with_exponent(0) - (1.0 - EPSILON / 2.0)
+            }
+        }
+    }
+}
+
+float_impls! { f32, u32, f32, u32, 23, 127 }
+float_impls! { f64, u64, f64, u64, 52, 1023 }
+
+#[cfg(feature="simd_support")]
+float_impls! { f32x2, u32x2, f32, u32, 23, 127 }
+#[cfg(feature="simd_support")]
+float_impls! { f32x4, u32x4, f32, u32, 23, 127 }
+#[cfg(feature="simd_support")]
+float_impls! { f32x8, u32x8, f32, u32, 23, 127 }
+#[cfg(feature="simd_support")]
+float_impls! { f32x16, u32x16, f32, u32, 23, 127 }
+
+#[cfg(feature="simd_support")]
+float_impls! { f64x2, u64x2, f64, u64, 52, 1023 }
+#[cfg(feature="simd_support")]
+float_impls! { f64x4, u64x4, f64, u64, 52, 1023 }
+#[cfg(feature="simd_support")]
+float_impls! { f64x8, u64x8, f64, u64, 52, 1023 }
+
+
+#[cfg(test)]
+mod tests {
+    use Rng;
+    use distributions::{Open01, OpenClosed01};
+    use rngs::mock::StepRng;
+    #[cfg(feature="simd_support")]
+    use packed_simd::*;
+
+    const EPSILON32: f32 = ::core::f32::EPSILON;
+    const EPSILON64: f64 = ::core::f64::EPSILON;
+
+    macro_rules! test_f32 {
+        ($fnn:ident, $ty:ident, $ZERO:expr, $EPSILON:expr) => {
+            #[test]
+            fn $fnn() {
+                // Standard
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.gen::<$ty>(), $ZERO);
+                let mut one = StepRng::new(1 << 8 | 1 << (8 + 32), 0);
+                assert_eq!(one.gen::<$ty>(), $EPSILON / 2.0);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.gen::<$ty>(), 1.0 - $EPSILON / 2.0);
+
+                // OpenClosed01
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.sample::<$ty, _>(OpenClosed01),
+                           0.0 + $EPSILON / 2.0);
+                let mut one = StepRng::new(1 << 8 | 1 << (8 + 32), 0);
+                assert_eq!(one.sample::<$ty, _>(OpenClosed01), $EPSILON);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.sample::<$ty, _>(OpenClosed01), $ZERO + 1.0);
+
+                // Open01
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.sample::<$ty, _>(Open01), 0.0 + $EPSILON / 2.0);
+                let mut one = StepRng::new(1 << 9 | 1 << (9 + 32), 0);
+                assert_eq!(one.sample::<$ty, _>(Open01), $EPSILON / 2.0 * 3.0);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.sample::<$ty, _>(Open01), 1.0 - $EPSILON / 2.0);
+            }
+        }
+    }
+    test_f32! { f32_edge_cases, f32, 0.0, EPSILON32 }
+    #[cfg(feature="simd_support")]
+    test_f32! { f32x2_edge_cases, f32x2, f32x2::splat(0.0), f32x2::splat(EPSILON32) }
+    #[cfg(feature="simd_support")]
+    test_f32! { f32x4_edge_cases, f32x4, f32x4::splat(0.0), f32x4::splat(EPSILON32) }
+    #[cfg(feature="simd_support")]
+    test_f32! { f32x8_edge_cases, f32x8, f32x8::splat(0.0), f32x8::splat(EPSILON32) }
+    #[cfg(feature="simd_support")]
+    test_f32! { f32x16_edge_cases, f32x16, f32x16::splat(0.0), f32x16::splat(EPSILON32) }
+
+    macro_rules! test_f64 {
+        ($fnn:ident, $ty:ident, $ZERO:expr, $EPSILON:expr) => {
+            #[test]
+            fn $fnn() {
+                // Standard
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.gen::<$ty>(), $ZERO);
+                let mut one = StepRng::new(1 << 11, 0);
+                assert_eq!(one.gen::<$ty>(), $EPSILON / 2.0);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.gen::<$ty>(), 1.0 - $EPSILON / 2.0);
+
+                // OpenClosed01
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.sample::<$ty, _>(OpenClosed01),
+                           0.0 + $EPSILON / 2.0);
+                let mut one = StepRng::new(1 << 11, 0);
+                assert_eq!(one.sample::<$ty, _>(OpenClosed01), $EPSILON);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.sample::<$ty, _>(OpenClosed01), $ZERO + 1.0);
+
+                // Open01
+                let mut zeros = StepRng::new(0, 0);
+                assert_eq!(zeros.sample::<$ty, _>(Open01), 0.0 + $EPSILON / 2.0);
+                let mut one = StepRng::new(1 << 12, 0);
+                assert_eq!(one.sample::<$ty, _>(Open01), $EPSILON / 2.0 * 3.0);
+                let mut max = StepRng::new(!0, 0);
+                assert_eq!(max.sample::<$ty, _>(Open01), 1.0 - $EPSILON / 2.0);
+            }
+        }
+    }
+    test_f64! { f64_edge_cases, f64, 0.0, EPSILON64 }
+    #[cfg(feature="simd_support")]
+    test_f64! { f64x2_edge_cases, f64x2, f64x2::splat(0.0), f64x2::splat(EPSILON64) }
+    #[cfg(feature="simd_support")]
+    test_f64! { f64x4_edge_cases, f64x4, f64x4::splat(0.0), f64x4::splat(EPSILON64) }
+    #[cfg(feature="simd_support")]
+    test_f64! { f64x8_edge_cases, f64x8, f64x8::splat(0.0), f64x8::splat(EPSILON64) }
+}
diff --git a/rand/src/distributions/gamma.rs b/rand/src/distributions/gamma.rs
index 2806495..43ac2bc 100644
--- a/rand/src/distributions/gamma.rs
+++ b/rand/src/distributions/gamma.rs
@@ -1,23 +1,20 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
-//
-// ignore-lexer-test FIXME #15679
 
 //! The Gamma and derived distributions.
 
 use self::GammaRepr::*;
 use self::ChiSquaredRepr::*;
 
-use {Rng, Open01};
-use super::normal::StandardNormal;
-use super::{IndependentSample, Sample, Exp};
+use Rng;
+use distributions::normal::StandardNormal;
+use distributions::{Distribution, Exp, Open01};
 
 /// The Gamma distribution `Gamma(shape, scale)` distribution.
 ///
@@ -30,25 +27,25 @@ use super::{IndependentSample, Sample, Exp};
 /// where `Γ` is the Gamma function, `k` is the shape and `θ` is the
 /// scale and both `k` and `θ` are strictly positive.
 ///
-/// The algorithm used is that described by Marsaglia & Tsang 2000[1],
+/// The algorithm used is that described by Marsaglia & Tsang 2000[^1],
 /// falling back to directly sampling from an Exponential for `shape
-/// == 1`, and using the boosting technique described in [1] for
+/// == 1`, and using the boosting technique described in that paper for
 /// `shape < 1`.
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{IndependentSample, Gamma};
+/// ```
+/// use rand::distributions::{Distribution, Gamma};
 ///
 /// let gamma = Gamma::new(2.0, 5.0);
-/// let v = gamma.ind_sample(&mut rand::thread_rng());
+/// let v = gamma.sample(&mut rand::thread_rng());
 /// println!("{} is from a Gamma(2, 5) distribution", v);
 /// ```
 ///
-/// [1]: George Marsaglia and Wai Wan Tsang. 2000. "A Simple Method
-/// for Generating Gamma Variables" *ACM Trans. Math. Softw.* 26, 3
-/// (September 2000),
-/// 363-372. DOI:[10.1145/358407.358414](http://doi.acm.org/10.1145/358407.358414)
+/// [^1]: George Marsaglia and Wai Wan Tsang. 2000. "A Simple Method for
+///       Generating Gamma Variables" *ACM Trans. Math. Softw.* 26, 3
+///       (September 2000), 363-372.
+///       DOI:[10.1145/358407.358414](https://doi.acm.org/10.1145/358407.358414)
 #[derive(Clone, Copy, Debug)]
 pub struct Gamma {
     repr: GammaRepr,
@@ -109,7 +106,7 @@ impl Gamma {
         } else {
             Large(GammaLargeShape::new_raw(shape, scale))
         };
-        Gamma { repr: repr }
+        Gamma { repr }
     }
 }
 
@@ -126,50 +123,40 @@ impl GammaLargeShape {
     fn new_raw(shape: f64, scale: f64) -> GammaLargeShape {
         let d = shape - 1. / 3.;
         GammaLargeShape {
-            scale: scale,
+            scale,
             c: 1. / (9. * d).sqrt(),
-            d: d
+            d
         }
     }
 }
 
-impl Sample<f64> for Gamma {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl Sample<f64> for GammaSmallShape {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl Sample<f64> for GammaLargeShape {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-
-impl IndependentSample<f64> for Gamma {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
+impl Distribution<f64> for Gamma {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
         match self.repr {
-            Small(ref g) => g.ind_sample(rng),
-            One(ref g) => g.ind_sample(rng),
-            Large(ref g) => g.ind_sample(rng),
+            Small(ref g) => g.sample(rng),
+            One(ref g) => g.sample(rng),
+            Large(ref g) => g.sample(rng),
         }
     }
 }
-impl IndependentSample<f64> for GammaSmallShape {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        let Open01(u) = rng.gen::<Open01<f64>>();
+impl Distribution<f64> for GammaSmallShape {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let u: f64 = rng.sample(Open01);
 
-        self.large_shape.ind_sample(rng) * u.powf(self.inv_shape)
+        self.large_shape.sample(rng) * u.powf(self.inv_shape)
     }
 }
-impl IndependentSample<f64> for GammaLargeShape {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
+impl Distribution<f64> for GammaLargeShape {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
         loop {
-            let StandardNormal(x) = rng.gen::<StandardNormal>();
+            let x = rng.sample(StandardNormal);
             let v_cbrt = 1.0 + self.c * x;
             if v_cbrt <= 0.0 { // a^3 <= 0 iff a <= 0
                 continue
             }
 
             let v = v_cbrt * v_cbrt * v_cbrt;
-            let Open01(u) = rng.gen::<Open01<f64>>();
+            let u: f64 = rng.sample(Open01);
 
             let x_sqr = x * x;
             if u < 1.0 - 0.0331 * x_sqr * x_sqr ||
@@ -190,11 +177,11 @@ impl IndependentSample<f64> for GammaLargeShape {
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{ChiSquared, IndependentSample};
+/// ```
+/// use rand::distributions::{ChiSquared, Distribution};
 ///
 /// let chi = ChiSquared::new(11.0);
-/// let v = chi.ind_sample(&mut rand::thread_rng());
+/// let v = chi.sample(&mut rand::thread_rng());
 /// println!("{} is from a χ²(11) distribution", v)
 /// ```
 #[derive(Clone, Copy, Debug)]
@@ -221,21 +208,18 @@ impl ChiSquared {
             assert!(k > 0.0, "ChiSquared::new called with `k` < 0");
             DoFAnythingElse(Gamma::new(0.5 * k, 2.0))
         };
-        ChiSquared { repr: repr }
+        ChiSquared { repr }
     }
 }
-impl Sample<f64> for ChiSquared {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl IndependentSample<f64> for ChiSquared {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
+impl Distribution<f64> for ChiSquared {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
         match self.repr {
             DoFExactlyOne => {
                 // k == 1 => N(0,1)^2
-                let StandardNormal(norm) = rng.gen::<StandardNormal>();
+                let norm = rng.sample(StandardNormal);
                 norm * norm
             }
-            DoFAnythingElse(ref g) => g.ind_sample(rng)
+            DoFAnythingElse(ref g) => g.sample(rng)
         }
     }
 }
@@ -248,11 +232,11 @@ impl IndependentSample<f64> for ChiSquared {
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{FisherF, IndependentSample};
+/// ```
+/// use rand::distributions::{FisherF, Distribution};
 ///
 /// let f = FisherF::new(2.0, 32.0);
-/// let v = f.ind_sample(&mut rand::thread_rng());
+/// let v = f.sample(&mut rand::thread_rng());
 /// println!("{} is from an F(2, 32) distribution", v)
 /// ```
 #[derive(Clone, Copy, Debug)]
@@ -278,12 +262,9 @@ impl FisherF {
         }
     }
 }
-impl Sample<f64> for FisherF {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl IndependentSample<f64> for FisherF {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        self.numer.ind_sample(rng) / self.denom.ind_sample(rng) * self.dof_ratio
+impl Distribution<f64> for FisherF {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        self.numer.sample(rng) / self.denom.sample(rng) * self.dof_ratio
     }
 }
 
@@ -292,11 +273,11 @@ impl IndependentSample<f64> for FisherF {
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{StudentT, IndependentSample};
+/// ```
+/// use rand::distributions::{StudentT, Distribution};
 ///
 /// let t = StudentT::new(11.0);
-/// let v = t.ind_sample(&mut rand::thread_rng());
+/// let v = t.sample(&mut rand::thread_rng());
 /// println!("{} is from a t(11) distribution", v)
 /// ```
 #[derive(Clone, Copy, Debug)]
@@ -316,46 +297,79 @@ impl StudentT {
         }
     }
 }
-impl Sample<f64> for StudentT {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
+impl Distribution<f64> for StudentT {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let norm = rng.sample(StandardNormal);
+        norm * (self.dof / self.chi.sample(rng)).sqrt()
+    }
+}
+
+/// The Beta distribution with shape parameters `alpha` and `beta`.
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Distribution, Beta};
+///
+/// let beta = Beta::new(2.0, 5.0);
+/// let v = beta.sample(&mut rand::thread_rng());
+/// println!("{} is from a Beta(2, 5) distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Beta {
+    gamma_a: Gamma,
+    gamma_b: Gamma,
+}
+
+impl Beta {
+    /// Construct an object representing the `Beta(alpha, beta)`
+    /// distribution.
+    ///
+    /// Panics if `shape <= 0` or `scale <= 0`.
+    pub fn new(alpha: f64, beta: f64) -> Beta {
+        assert!((alpha > 0.) & (beta > 0.));
+        Beta {
+            gamma_a: Gamma::new(alpha, 1.),
+            gamma_b: Gamma::new(beta, 1.),
+        }
+    }
 }
-impl IndependentSample<f64> for StudentT {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        let StandardNormal(norm) = rng.gen::<StandardNormal>();
-        norm * (self.dof / self.chi.ind_sample(rng)).sqrt()
+
+impl Distribution<f64> for Beta {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let x = self.gamma_a.sample(rng);
+        let y = self.gamma_b.sample(rng);
+        x / (x + y)
     }
 }
 
 #[cfg(test)]
 mod test {
-    use distributions::{Sample, IndependentSample};
-    use super::{ChiSquared, StudentT, FisherF};
+    use distributions::Distribution;
+    use super::{Beta, ChiSquared, StudentT, FisherF};
 
     #[test]
     fn test_chi_squared_one() {
-        let mut chi = ChiSquared::new(1.0);
-        let mut rng = ::test::rng();
+        let chi = ChiSquared::new(1.0);
+        let mut rng = ::test::rng(201);
         for _ in 0..1000 {
             chi.sample(&mut rng);
-            chi.ind_sample(&mut rng);
         }
     }
     #[test]
     fn test_chi_squared_small() {
-        let mut chi = ChiSquared::new(0.5);
-        let mut rng = ::test::rng();
+        let chi = ChiSquared::new(0.5);
+        let mut rng = ::test::rng(202);
         for _ in 0..1000 {
             chi.sample(&mut rng);
-            chi.ind_sample(&mut rng);
         }
     }
     #[test]
     fn test_chi_squared_large() {
-        let mut chi = ChiSquared::new(30.0);
-        let mut rng = ::test::rng();
+        let chi = ChiSquared::new(30.0);
+        let mut rng = ::test::rng(203);
         for _ in 0..1000 {
             chi.sample(&mut rng);
-            chi.ind_sample(&mut rng);
         }
     }
     #[test]
@@ -366,21 +380,34 @@ mod test {
 
     #[test]
     fn test_f() {
-        let mut f = FisherF::new(2.0, 32.0);
-        let mut rng = ::test::rng();
+        let f = FisherF::new(2.0, 32.0);
+        let mut rng = ::test::rng(204);
         for _ in 0..1000 {
             f.sample(&mut rng);
-            f.ind_sample(&mut rng);
         }
     }
 
     #[test]
     fn test_t() {
-        let mut t = StudentT::new(11.0);
-        let mut rng = ::test::rng();
+        let t = StudentT::new(11.0);
+        let mut rng = ::test::rng(205);
         for _ in 0..1000 {
             t.sample(&mut rng);
-            t.ind_sample(&mut rng);
         }
     }
+
+    #[test]
+    fn test_beta() {
+        let beta = Beta::new(1.0, 2.0);
+        let mut rng = ::test::rng(201);
+        for _ in 0..1000 {
+            beta.sample(&mut rng);
+        }
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_beta_invalid_dof() {
+        Beta::new(0., 0.);
+    }
 }
diff --git a/rand/src/distributions/integer.rs b/rand/src/distributions/integer.rs
new file mode 100644
index 0000000..4e6604d
--- /dev/null
+++ b/rand/src/distributions/integer.rs
@@ -0,0 +1,161 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The implementations of the `Standard` distribution for integer types.
+
+use {Rng};
+use distributions::{Distribution, Standard};
+#[cfg(feature="simd_support")]
+use packed_simd::*;
+#[cfg(all(target_arch = "x86", feature="nightly"))]
+use core::arch::x86::*;
+#[cfg(all(target_arch = "x86_64", feature="nightly"))]
+use core::arch::x86_64::*;
+
+impl Distribution<u8> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u8 {
+        rng.next_u32() as u8
+    }
+}
+
+impl Distribution<u16> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u16 {
+        rng.next_u32() as u16
+    }
+}
+
+impl Distribution<u32> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u32 {
+        rng.next_u32()
+    }
+}
+
+impl Distribution<u64> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64 {
+        rng.next_u64()
+    }
+}
+
+#[cfg(rust_1_26)]
+impl Distribution<u128> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u128 {
+        // Use LE; we explicitly generate one value before the next.
+        let x = rng.next_u64() as u128;
+        let y = rng.next_u64() as u128;
+        (y << 64) | x
+    }
+}
+
+impl Distribution<usize> for Standard {
+    #[inline]
+    #[cfg(any(target_pointer_width = "32", target_pointer_width = "16"))]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
+        rng.next_u32() as usize
+    }
+
+    #[inline]
+    #[cfg(target_pointer_width = "64")]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
+        rng.next_u64() as usize
+    }
+}
+
+macro_rules! impl_int_from_uint {
+    ($ty:ty, $uty:ty) => {
+        impl Distribution<$ty> for Standard {
+            #[inline]
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
+                rng.gen::<$uty>() as $ty
+            }
+        }
+    }
+}
+
+impl_int_from_uint! { i8, u8 }
+impl_int_from_uint! { i16, u16 }
+impl_int_from_uint! { i32, u32 }
+impl_int_from_uint! { i64, u64 }
+#[cfg(rust_1_26)] impl_int_from_uint! { i128, u128 }
+impl_int_from_uint! { isize, usize }
+
+#[cfg(feature="simd_support")]
+macro_rules! simd_impl {
+    ($(($intrinsic:ident, $vec:ty),)+) => {$(
+        impl Distribution<$intrinsic> for Standard {
+            #[inline]
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $intrinsic {
+                $intrinsic::from_bits(rng.gen::<$vec>())
+            }
+        }
+    )+};
+
+    ($bits:expr,) => {};
+    ($bits:expr, $ty:ty, $($ty_more:ty,)*) => {
+        simd_impl!($bits, $($ty_more,)*);
+
+        impl Distribution<$ty> for Standard {
+            #[inline]
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> $ty {
+                let mut vec: $ty = Default::default();
+                unsafe {
+                    let ptr = &mut vec;
+                    let b_ptr = &mut *(ptr as *mut $ty as *mut [u8; $bits/8]);
+                    rng.fill_bytes(b_ptr);
+                }
+                vec.to_le()
+            }
+        }
+    };
+}
+
+#[cfg(feature="simd_support")]
+simd_impl!(16, u8x2, i8x2,);
+#[cfg(feature="simd_support")]
+simd_impl!(32, u8x4, i8x4, u16x2, i16x2,);
+#[cfg(feature="simd_support")]
+simd_impl!(64, u8x8, i8x8, u16x4, i16x4, u32x2, i32x2,);
+#[cfg(feature="simd_support")]
+simd_impl!(128, u8x16, i8x16, u16x8, i16x8, u32x4, i32x4, u64x2, i64x2,);
+#[cfg(feature="simd_support")]
+simd_impl!(256, u8x32, i8x32, u16x16, i16x16, u32x8, i32x8, u64x4, i64x4,);
+#[cfg(feature="simd_support")]
+simd_impl!(512, u8x64, i8x64, u16x32, i16x32, u32x16, i32x16, u64x8, i64x8,);
+#[cfg(all(feature="simd_support", feature="nightly", any(target_arch="x86", target_arch="x86_64")))]
+simd_impl!((__m64, u8x8), (__m128i, u8x16), (__m256i, u8x32),);
+
+#[cfg(test)]
+mod tests {
+    use Rng;
+    use distributions::{Standard};
+    
+    #[test]
+    fn test_integers() {
+        let mut rng = ::test::rng(806);
+        
+        rng.sample::<isize, _>(Standard);
+        rng.sample::<i8, _>(Standard);
+        rng.sample::<i16, _>(Standard);
+        rng.sample::<i32, _>(Standard);
+        rng.sample::<i64, _>(Standard);
+        #[cfg(rust_1_26)]
+        rng.sample::<i128, _>(Standard);
+        
+        rng.sample::<usize, _>(Standard);
+        rng.sample::<u8, _>(Standard);
+        rng.sample::<u16, _>(Standard);
+        rng.sample::<u32, _>(Standard);
+        rng.sample::<u64, _>(Standard);
+        #[cfg(rust_1_26)]
+        rng.sample::<u128, _>(Standard);
+    }
+}
diff --git a/rand/src/distributions/mod.rs b/rand/src/distributions/mod.rs
index 5de8efb..160cd31 100644
--- a/rand/src/distributions/mod.rs
+++ b/rand/src/distributions/mod.rs
@@ -1,94 +1,394 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2017 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Sampling from random distributions.
+//! Generating random samples from probability distributions.
 //!
-//! This is a generalization of `Rand` to allow parameters to control the
-//! exact properties of the generated values, e.g. the mean and standard
-//! deviation of a normal distribution. The `Sample` trait is the most
-//! general, and allows for generating values that change some state
-//! internally. The `IndependentSample` trait is for generating values
-//! that do not need to record state.
-
-use core::marker;
-
-use {Rng, Rand};
-
-pub use self::range::Range;
-#[cfg(feature="std")]
-pub use self::gamma::{Gamma, ChiSquared, FisherF, StudentT};
-#[cfg(feature="std")]
-pub use self::normal::{Normal, LogNormal};
-#[cfg(feature="std")]
-pub use self::exponential::Exp;
-
-pub mod range;
-#[cfg(feature="std")]
-pub mod gamma;
-#[cfg(feature="std")]
-pub mod normal;
-#[cfg(feature="std")]
-pub mod exponential;
-
-#[cfg(feature="std")]
-mod ziggurat_tables;
-
-/// Types that can be used to create a random instance of `Support`.
-pub trait Sample<Support> {
-    /// Generate a random value of `Support`, using `rng` as the
-    /// source of randomness.
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> Support;
-}
-
-/// `Sample`s that do not require keeping track of state.
+//! This module is the home of the [`Distribution`] trait and several of its
+//! implementations. It is the workhorse behind some of the convenient
+//! functionality of the [`Rng`] trait, including [`gen`], [`gen_range`] and
+//! of course [`sample`].
+//!
+//! Abstractly, a [probability distribution] describes the probability of
+//! occurance of each value in its sample space.
+//!
+//! More concretely, an implementation of `Distribution<T>` for type `X` is an
+//! algorithm for choosing values from the sample space (a subset of `T`)
+//! according to the distribution `X` represents, using an external source of
+//! randomness (an RNG supplied to the `sample` function).
+//!
+//! A type `X` may implement `Distribution<T>` for multiple types `T`.
+//! Any type implementing [`Distribution`] is stateless (i.e. immutable),
+//! but it may have internal parameters set at construction time (for example,
+//! [`Uniform`] allows specification of its sample space as a range within `T`).
+//!
+//!
+//! # The `Standard` distribution
+//!
+//! The [`Standard`] distribution is important to mention. This is the
+//! distribution used by [`Rng::gen()`] and represents the "default" way to
+//! produce a random value for many different types, including most primitive
+//! types, tuples, arrays, and a few derived types. See the documentation of
+//! [`Standard`] for more details.
+//!
+//! Implementing `Distribution<T>` for [`Standard`] for user types `T` makes it
+//! possible to generate type `T` with [`Rng::gen()`], and by extension also
+//! with the [`random()`] function.
+//!
+//!
+//! # Distribution to sample from a `Uniform` range
+//!
+//! The [`Uniform`] distribution is more flexible than [`Standard`], but also
+//! more specialised: it supports fewer target types, but allows the sample
+//! space to be specified as an arbitrary range within its target type `T`.
+//! Both [`Standard`] and [`Uniform`] are in some sense uniform distributions.
+//!
+//! Values may be sampled from this distribution using [`Rng::gen_range`] or
+//! by creating a distribution object with [`Uniform::new`],
+//! [`Uniform::new_inclusive`] or `From<Range>`. When the range limits are not
+//! known at compile time it is typically faster to reuse an existing
+//! distribution object than to call [`Rng::gen_range`].
+//!
+//! User types `T` may also implement `Distribution<T>` for [`Uniform`],
+//! although this is less straightforward than for [`Standard`] (see the
+//! documentation in the [`uniform` module]. Doing so enables generation of
+//! values of type `T` with  [`Rng::gen_range`].
+//!
+//!
+//! # Other distributions
+//!
+//! There are surprisingly many ways to uniformly generate random floats. A
+//! range between 0 and 1 is standard, but the exact bounds (open vs closed)
+//! and accuracy differ. In addition to the [`Standard`] distribution Rand offers
+//! [`Open01`] and [`OpenClosed01`]. See [Floating point implementation] for
+//! more details.
+//!
+//! [`Alphanumeric`] is a simple distribution to sample random letters and
+//! numbers of the `char` type; in contrast [`Standard`] may sample any valid
+//! `char`.
+//!
+//! [`WeightedIndex`] can be used to do weighted sampling from a set of items,
+//! such as from an array.
+//!
+//! # Non-uniform probability distributions
+//!
+//! Rand currently provides the following probability distributions:
+//!
+//! - Related to real-valued quantities that grow linearly
+//!   (e.g. errors, offsets):
+//!   - [`Normal`] distribution, and [`StandardNormal`] as a primitive
+//!   - [`Cauchy`] distribution
+//! - Related to Bernoulli trials (yes/no events, with a given probability):
+//!   - [`Binomial`] distribution
+//!   - [`Bernoulli`] distribution, similar to [`Rng::gen_bool`].
+//! - Related to positive real-valued quantities that grow exponentially
+//!   (e.g. prices, incomes, populations):
+//!   - [`LogNormal`] distribution
+//! - Related to the occurrence of independent events at a given rate:
+//!   - [`Pareto`] distribution
+//!   - [`Poisson`] distribution
+//!   - [`Exp`]onential distribution, and [`Exp1`] as a primitive
+//!   - [`Weibull`] distribution
+//! - Gamma and derived distributions:
+//!   - [`Gamma`] distribution
+//!   - [`ChiSquared`] distribution
+//!   - [`StudentT`] distribution
+//!   - [`FisherF`] distribution
+//! - Triangular distribution:
+//!   - [`Beta`] distribution
+//!   - [`Triangular`] distribution
+//! - Multivariate probability distributions
+//!   - [`Dirichlet`] distribution
+//!   - [`UnitSphereSurface`] distribution
+//!   - [`UnitCircle`] distribution
+//!
+//! # Examples
+//!
+//! Sampling from a distribution:
+//!
+//! ```
+//! use rand::{thread_rng, Rng};
+//! use rand::distributions::Exp;
+//!
+//! let exp = Exp::new(2.0);
+//! let v = thread_rng().sample(exp);
+//! println!("{} is from an Exp(2) distribution", v);
+//! ```
+//!
+//! Implementing the [`Standard`] distribution for a user type:
+//!
+//! ```
+//! # #![allow(dead_code)]
+//! use rand::Rng;
+//! use rand::distributions::{Distribution, Standard};
+//!
+//! struct MyF32 {
+//!     x: f32,
+//! }
+//!
+//! impl Distribution<MyF32> for Standard {
+//!     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> MyF32 {
+//!         MyF32 { x: rng.gen() }
+//!     }
+//! }
+//! ```
+//!
+//!
+//! [probability distribution]: https://en.wikipedia.org/wiki/Probability_distribution
+//! [`Distribution`]: trait.Distribution.html
+//! [`gen_range`]: ../trait.Rng.html#method.gen_range
+//! [`gen`]: ../trait.Rng.html#method.gen
+//! [`sample`]: ../trait.Rng.html#method.sample
+//! [`new_inclusive`]: struct.Uniform.html#method.new_inclusive
+//! [`random()`]: ../fn.random.html
+//! [`Rng::gen_bool`]: ../trait.Rng.html#method.gen_bool
+//! [`Rng::gen_range`]: ../trait.Rng.html#method.gen_range
+//! [`Rng::gen()`]: ../trait.Rng.html#method.gen
+//! [`Rng`]: ../trait.Rng.html
+//! [`uniform` module]: uniform/index.html
+//! [Floating point implementation]: struct.Standard.html#floating-point-implementation
+// distributions
+//! [`Alphanumeric`]: struct.Alphanumeric.html
+//! [`Bernoulli`]: struct.Bernoulli.html
+//! [`Beta`]: struct.Beta.html
+//! [`Binomial`]: struct.Binomial.html
+//! [`Cauchy`]: struct.Cauchy.html
+//! [`ChiSquared`]: struct.ChiSquared.html
+//! [`Dirichlet`]: struct.Dirichlet.html
+//! [`Exp`]: struct.Exp.html
+//! [`Exp1`]: struct.Exp1.html
+//! [`FisherF`]: struct.FisherF.html
+//! [`Gamma`]: struct.Gamma.html
+//! [`LogNormal`]: struct.LogNormal.html
+//! [`Normal`]: struct.Normal.html
+//! [`Open01`]: struct.Open01.html
+//! [`OpenClosed01`]: struct.OpenClosed01.html
+//! [`Pareto`]: struct.Pareto.html
+//! [`Poisson`]: struct.Poisson.html
+//! [`Standard`]: struct.Standard.html
+//! [`StandardNormal`]: struct.StandardNormal.html
+//! [`StudentT`]: struct.StudentT.html
+//! [`Triangular`]: struct.Triangular.html
+//! [`Uniform`]: struct.Uniform.html
+//! [`Uniform::new`]: struct.Uniform.html#method.new
+//! [`Uniform::new_inclusive`]: struct.Uniform.html#method.new_inclusive
+//! [`UnitSphereSurface`]: struct.UnitSphereSurface.html
+//! [`UnitCircle`]: struct.UnitCircle.html
+//! [`Weibull`]: struct.Weibull.html
+//! [`WeightedIndex`]: struct.WeightedIndex.html
+
+#[cfg(any(rust_1_26, features="nightly"))]
+use core::iter;
+use Rng;
+
+pub use self::other::Alphanumeric;
+#[doc(inline)] pub use self::uniform::Uniform;
+pub use self::float::{OpenClosed01, Open01};
+pub use self::bernoulli::Bernoulli;
+#[cfg(feature="alloc")] pub use self::weighted::{WeightedIndex, WeightedError};
+#[cfg(feature="std")] pub use self::unit_sphere::UnitSphereSurface;
+#[cfg(feature="std")] pub use self::unit_circle::UnitCircle;
+#[cfg(feature="std")] pub use self::gamma::{Gamma, ChiSquared, FisherF,
+    StudentT, Beta};
+#[cfg(feature="std")] pub use self::normal::{Normal, LogNormal, StandardNormal};
+#[cfg(feature="std")] pub use self::exponential::{Exp, Exp1};
+#[cfg(feature="std")] pub use self::pareto::Pareto;
+#[cfg(feature="std")] pub use self::poisson::Poisson;
+#[cfg(feature="std")] pub use self::binomial::Binomial;
+#[cfg(feature="std")] pub use self::cauchy::Cauchy;
+#[cfg(feature="std")] pub use self::dirichlet::Dirichlet;
+#[cfg(feature="std")] pub use self::triangular::Triangular;
+#[cfg(feature="std")] pub use self::weibull::Weibull;
+
+pub mod uniform;
+mod bernoulli;
+#[cfg(feature="alloc")] mod weighted;
+#[cfg(feature="std")] mod unit_sphere;
+#[cfg(feature="std")] mod unit_circle;
+#[cfg(feature="std")] mod gamma;
+#[cfg(feature="std")] mod normal;
+#[cfg(feature="std")] mod exponential;
+#[cfg(feature="std")] mod pareto;
+#[cfg(feature="std")] mod poisson;
+#[cfg(feature="std")] mod binomial;
+#[cfg(feature="std")] mod cauchy;
+#[cfg(feature="std")] mod dirichlet;
+#[cfg(feature="std")] mod triangular;
+#[cfg(feature="std")] mod weibull;
+
+mod float;
+mod integer;
+mod other;
+mod utils;
+#[cfg(feature="std")] mod ziggurat_tables;
+
+/// Types (distributions) that can be used to create a random instance of `T`.
+///
+/// It is possible to sample from a distribution through both the
+/// `Distribution` and [`Rng`] traits, via `distr.sample(&mut rng)` and
+/// `rng.sample(distr)`. They also both offer the [`sample_iter`] method, which
+/// produces an iterator that samples from the distribution.
+///
+/// All implementations are expected to be immutable; this has the significant
+/// advantage of not needing to consider thread safety, and for most
+/// distributions efficient state-less sampling algorithms are available.
 ///
-/// Since no state is recorded, each sample is (statistically)
-/// independent of all others, assuming the `Rng` used has this
-/// property.
-// FIXME maybe having this separate is overkill (the only reason is to
-// take &self rather than &mut self)? or maybe this should be the
-// trait called `Sample` and the other should be `DependentSample`.
-pub trait IndependentSample<Support>: Sample<Support> {
-    /// Generate a random value.
-    fn ind_sample<R: Rng>(&self, &mut R) -> Support;
+/// [`Rng`]: ../trait.Rng.html
+/// [`sample_iter`]: trait.Distribution.html#method.sample_iter
+pub trait Distribution<T> {
+    /// Generate a random value of `T`, using `rng` as the source of randomness.
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> T;
+
+    /// Create an iterator that generates random values of `T`, using `rng` as
+    /// the source of randomness.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rand::thread_rng;
+    /// use rand::distributions::{Distribution, Alphanumeric, Uniform, Standard};
+    ///
+    /// let mut rng = thread_rng();
+    ///
+    /// // Vec of 16 x f32:
+    /// let v: Vec<f32> = Standard.sample_iter(&mut rng).take(16).collect();
+    ///
+    /// // String:
+    /// let s: String = Alphanumeric.sample_iter(&mut rng).take(7).collect();
+    ///
+    /// // Dice-rolling:
+    /// let die_range = Uniform::new_inclusive(1, 6);
+    /// let mut roll_die = die_range.sample_iter(&mut rng);
+    /// while roll_die.next().unwrap() != 6 {
+    ///     println!("Not a 6; rolling again!");
+    /// }
+    /// ```
+    fn sample_iter<'a, R>(&'a self, rng: &'a mut R) -> DistIter<'a, Self, R, T>
+        where Self: Sized, R: Rng
+    {
+        DistIter {
+            distr: self,
+            rng: rng,
+            phantom: ::core::marker::PhantomData,
+        }
+    }
 }
 
-/// A wrapper for generating types that implement `Rand` via the
-/// `Sample` & `IndependentSample` traits.
-#[derive(Debug)]
-pub struct RandSample<Sup> {
-    _marker: marker::PhantomData<fn() -> Sup>,
+impl<'a, T, D: Distribution<T>> Distribution<T> for &'a D {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> T {
+        (*self).sample(rng)
+    }
 }
 
-impl<Sup> Copy for RandSample<Sup> {}
-impl<Sup> Clone for RandSample<Sup> {
-    fn clone(&self) -> Self { *self }
-}
 
-impl<Sup: Rand> Sample<Sup> for RandSample<Sup> {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> Sup { self.ind_sample(rng) }
+/// An iterator that generates random values of `T` with distribution `D`,
+/// using `R` as the source of randomness.
+///
+/// This `struct` is created by the [`sample_iter`] method on [`Distribution`].
+/// See its documentation for more.
+///
+/// [`Distribution`]: trait.Distribution.html
+/// [`sample_iter`]: trait.Distribution.html#method.sample_iter
+#[derive(Debug)]
+pub struct DistIter<'a, D: 'a, R: 'a, T> {
+    distr: &'a D,
+    rng: &'a mut R,
+    phantom: ::core::marker::PhantomData<T>,
 }
 
-impl<Sup: Rand> IndependentSample<Sup> for RandSample<Sup> {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> Sup {
-        rng.gen()
+impl<'a, D, R, T> Iterator for DistIter<'a, D, R, T>
+    where D: Distribution<T>, R: Rng + 'a
+{
+    type Item = T;
+
+    #[inline(always)]
+    fn next(&mut self) -> Option<T> {
+        Some(self.distr.sample(self.rng))
     }
-}
 
-impl<Sup> RandSample<Sup> {
-    pub fn new() -> RandSample<Sup> {
-        RandSample { _marker: marker::PhantomData }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (usize::max_value(), None)
     }
 }
 
+#[cfg(rust_1_26)]
+impl<'a, D, R, T> iter::FusedIterator for DistIter<'a, D, R, T>
+    where D: Distribution<T>, R: Rng + 'a {}
+
+#[cfg(features = "nightly")]
+impl<'a, D, R, T> iter::TrustedLen for DistIter<'a, D, R, T>
+    where D: Distribution<T>, R: Rng + 'a {}
+
+
+/// A generic random value distribution, implemented for many primitive types.
+/// Usually generates values with a numerically uniform distribution, and with a
+/// range appropriate to the type.
+/// 
+/// ## Built-in Implementations
+///
+/// Assuming the provided `Rng` is well-behaved, these implementations
+/// generate values with the following ranges and distributions:
+///
+/// * Integers (`i32`, `u32`, `isize`, `usize`, etc.): Uniformly distributed
+///   over all values of the type.
+/// * `char`: Uniformly distributed over all Unicode scalar values, i.e. all
+///   code points in the range `0...0x10_FFFF`, except for the range
+///   `0xD800...0xDFFF` (the surrogate code points). This includes
+///   unassigned/reserved code points.
+/// * `bool`: Generates `false` or `true`, each with probability 0.5.
+/// * Floating point types (`f32` and `f64`): Uniformly distributed in the
+///   half-open range `[0, 1)`. See notes below.
+/// * Wrapping integers (`Wrapping<T>`), besides the type identical to their
+///   normal integer variants.
+///
+/// The following aggregate types also implement the distribution `Standard` as
+/// long as their component types implement it:
+///
+/// * Tuples and arrays: Each element of the tuple or array is generated
+///   independently, using the `Standard` distribution recursively.
+/// * `Option<T>` where `Standard` is implemented for `T`: Returns `None` with
+///   probability 0.5; otherwise generates a random `x: T` and returns `Some(x)`.
+///
+/// # Example
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::Standard;
+///
+/// let val: f32 = SmallRng::from_entropy().sample(Standard);
+/// println!("f32 from [0, 1): {}", val);
+/// ```
+///
+/// # Floating point implementation
+/// The floating point implementations for `Standard` generate a random value in
+/// the half-open interval `[0, 1)`, i.e. including 0 but not 1.
+///
+/// All values that can be generated are of the form `n * ε/2`. For `f32`
+/// the 23 most significant random bits of a `u32` are used and for `f64` the
+/// 53 most significant bits of a `u64` are used. The conversion uses the
+/// multiplicative method: `(rng.gen::<$uty>() >> N) as $ty * (ε/2)`.
+///
+/// See also: [`Open01`] which samples from `(0, 1)`, [`OpenClosed01`] which
+/// samples from `(0, 1]` and `Rng::gen_range(0, 1)` which also samples from
+/// `[0, 1)`. Note that `Open01` and `gen_range` (which uses [`Uniform`]) use
+/// transmute-based methods which yield 1 bit less precision but may perform
+/// faster on some architectures (on modern Intel CPUs all methods have
+/// approximately equal performance).
+///
+/// [`Open01`]: struct.Open01.html
+/// [`OpenClosed01`]: struct.OpenClosed01.html
+/// [`Uniform`]: uniform/struct.Uniform.html
+#[derive(Clone, Copy, Debug)]
+pub struct Standard;
+
+
 /// A value with a particular weight for use with `WeightedChoice`.
+#[deprecated(since="0.6.0", note="use WeightedIndex instead")]
+#[allow(deprecated)]
 #[derive(Copy, Clone, Debug)]
 pub struct Weighted<T> {
     /// The numerical weight of this item
@@ -99,35 +399,19 @@ pub struct Weighted<T> {
 
 /// A distribution that selects from a finite collection of weighted items.
 ///
-/// Each item has an associated weight that influences how likely it
-/// is to be chosen: higher weight is more likely.
-///
-/// The `Clone` restriction is a limitation of the `Sample` and
-/// `IndependentSample` traits. Note that `&T` is (cheaply) `Clone` for
-/// all `T`, as is `u32`, so one can store references or indices into
-/// another vector.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::distributions::{Weighted, WeightedChoice, IndependentSample};
+/// Deprecated: use [`WeightedIndex`] instead.
 ///
-/// let mut items = vec!(Weighted { weight: 2, item: 'a' },
-///                      Weighted { weight: 4, item: 'b' },
-///                      Weighted { weight: 1, item: 'c' });
-/// let wc = WeightedChoice::new(&mut items);
-/// let mut rng = rand::thread_rng();
-/// for _ in 0..16 {
-///      // on average prints 'a' 4 times, 'b' 8 and 'c' twice.
-///      println!("{}", wc.ind_sample(&mut rng));
-/// }
-/// ```
+/// [`WeightedIndex`]: struct.WeightedIndex.html
+#[deprecated(since="0.6.0", note="use WeightedIndex instead")]
+#[allow(deprecated)]
 #[derive(Debug)]
 pub struct WeightedChoice<'a, T:'a> {
     items: &'a mut [Weighted<T>],
-    weight_range: Range<u32>
+    weight_range: Uniform<u32>,
 }
 
+#[deprecated(since="0.6.0", note="use WeightedIndex instead")]
+#[allow(deprecated)]
 impl<'a, T: Clone> WeightedChoice<'a, T> {
     /// Create a new `WeightedChoice`.
     ///
@@ -157,26 +441,24 @@ impl<'a, T: Clone> WeightedChoice<'a, T> {
         assert!(running_total != 0, "WeightedChoice::new called with a total weight of 0");
 
         WeightedChoice {
-            items: items,
+            items,
             // we're likely to be generating numbers in this range
             // relatively often, so might as well cache it
-            weight_range: Range::new(0, running_total)
+            weight_range: Uniform::new(0, running_total)
         }
     }
 }
 
-impl<'a, T: Clone> Sample<T> for WeightedChoice<'a, T> {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> T { self.ind_sample(rng) }
-}
-
-impl<'a, T: Clone> IndependentSample<T> for WeightedChoice<'a, T> {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> T {
+#[deprecated(since="0.6.0", note="use WeightedIndex instead")]
+#[allow(deprecated)]
+impl<'a, T: Clone> Distribution<T> for WeightedChoice<'a, T> {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> T {
         // we want to find the first element that has cumulative
         // weight > sample_weight, which we do by binary since the
         // cumulative weights of self.items are sorted.
 
         // choose a weight in [0, total_weight)
-        let sample_weight = self.weight_range.ind_sample(rng);
+        let sample_weight = self.weight_range.sample(rng);
 
         // short circuit when it's the first item
         if sample_weight < self.items[0].weight {
@@ -208,163 +490,78 @@ impl<'a, T: Clone> IndependentSample<T> for WeightedChoice<'a, T> {
             }
             modifier /= 2;
         }
-        return self.items[idx + 1].item.clone();
-    }
-}
-
-/// Sample a random number using the Ziggurat method (specifically the
-/// ZIGNOR variant from Doornik 2005). Most of the arguments are
-/// directly from the paper:
-///
-/// * `rng`: source of randomness
-/// * `symmetric`: whether this is a symmetric distribution, or one-sided with P(x < 0) = 0.
-/// * `X`: the $x_i$ abscissae.
-/// * `F`: precomputed values of the PDF at the $x_i$, (i.e. $f(x_i)$)
-/// * `F_DIFF`: precomputed values of $f(x_i) - f(x_{i+1})$
-/// * `pdf`: the probability density function
-/// * `zero_case`: manual sampling from the tail when we chose the
-///    bottom box (i.e. i == 0)
-
-// the perf improvement (25-50%) is definitely worth the extra code
-// size from force-inlining.
-#[cfg(feature="std")]
-#[inline(always)]
-fn ziggurat<R: Rng, P, Z>(
-            rng: &mut R,
-            symmetric: bool,
-            x_tab: ziggurat_tables::ZigTable,
-            f_tab: ziggurat_tables::ZigTable,
-            mut pdf: P,
-            mut zero_case: Z)
-            -> f64 where P: FnMut(f64) -> f64, Z: FnMut(&mut R, f64) -> f64 {
-    const SCALE: f64 = (1u64 << 53) as f64;
-    loop {
-        // reimplement the f64 generation as an optimisation suggested
-        // by the Doornik paper: we have a lot of precision-space
-        // (i.e. there are 11 bits of the 64 of a u64 to use after
-        // creating a f64), so we might as well reuse some to save
-        // generating a whole extra random number. (Seems to be 15%
-        // faster.)
-        //
-        // This unfortunately misses out on the benefits of direct
-        // floating point generation if an RNG like dSMFT is
-        // used. (That is, such RNGs create floats directly, highly
-        // efficiently and overload next_f32/f64, so by not calling it
-        // this may be slower than it would be otherwise.)
-        // FIXME: investigate/optimise for the above.
-        let bits: u64 = rng.gen();
-        let i = (bits & 0xff) as usize;
-        let f = (bits >> 11) as f64 / SCALE;
-
-        // u is either U(-1, 1) or U(0, 1) depending on if this is a
-        // symmetric distribution or not.
-        let u = if symmetric {2.0 * f - 1.0} else {f};
-        let x = u * x_tab[i];
-
-        let test_x = if symmetric { x.abs() } else {x};
-
-        // algebraically equivalent to |u| < x_tab[i+1]/x_tab[i] (or u < x_tab[i+1]/x_tab[i])
-        if test_x < x_tab[i + 1] {
-            return x;
-        }
-        if i == 0 {
-            return zero_case(rng, u);
-        }
-        // algebraically equivalent to f1 + DRanU()*(f0 - f1) < 1
-        if f_tab[i + 1] + (f_tab[i] - f_tab[i + 1]) * rng.gen::<f64>() < pdf(x) {
-            return x;
-        }
+        self.items[idx + 1].item.clone()
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use rngs::mock::StepRng;
+    #[allow(deprecated)]
+    use super::{WeightedChoice, Weighted, Distribution};
 
-    use {Rng, Rand};
-    use super::{RandSample, WeightedChoice, Weighted, Sample, IndependentSample};
-
-    #[derive(PartialEq, Debug)]
-    struct ConstRand(usize);
-    impl Rand for ConstRand {
-        fn rand<R: Rng>(_: &mut R) -> ConstRand {
-            ConstRand(0)
-        }
-    }
-
-    // 0, 1, 2, 3, ...
-    struct CountingRng { i: u32 }
-    impl Rng for CountingRng {
-        fn next_u32(&mut self) -> u32 {
-            self.i += 1;
-            self.i - 1
-        }
-        fn next_u64(&mut self) -> u64 {
-            self.next_u32() as u64
-        }
-    }
-
-    #[test]
-    fn test_rand_sample() {
-        let mut rand_sample = RandSample::<ConstRand>::new();
-
-        assert_eq!(rand_sample.sample(&mut ::test::rng()), ConstRand(0));
-        assert_eq!(rand_sample.ind_sample(&mut ::test::rng()), ConstRand(0));
-    }
     #[test]
+    #[allow(deprecated)]
     fn test_weighted_choice() {
         // this makes assumptions about the internal implementation of
-        // WeightedChoice, specifically: it doesn't reorder the items,
-        // it doesn't do weird things to the RNG (so 0 maps to 0, 1 to
-        // 1, internally; modulo a modulo operation).
+        // WeightedChoice. It may fail when the implementation in
+        // `distributions::uniform::UniformInt` changes.
 
         macro_rules! t {
             ($items:expr, $expected:expr) => {{
                 let mut items = $items;
+                let mut total_weight = 0;
+                for item in &items { total_weight += item.weight; }
+
                 let wc = WeightedChoice::new(&mut items);
                 let expected = $expected;
 
-                let mut rng = CountingRng { i: 0 };
+                // Use extremely large steps between the random numbers, because
+                // we test with small ranges and `UniformInt` is designed to prefer
+                // the most significant bits.
+                let mut rng = StepRng::new(0, !0 / (total_weight as u64));
 
                 for &val in expected.iter() {
-                    assert_eq!(wc.ind_sample(&mut rng), val)
+                    assert_eq!(wc.sample(&mut rng), val)
                 }
             }}
         }
 
-        t!(vec!(Weighted { weight: 1, item: 10}), [10]);
+        t!([Weighted { weight: 1, item: 10}], [10]);
 
         // skip some
-        t!(vec!(Weighted { weight: 0, item: 20},
-                Weighted { weight: 2, item: 21},
-                Weighted { weight: 0, item: 22},
-                Weighted { weight: 1, item: 23}),
-           [21,21, 23]);
+        t!([Weighted { weight: 0, item: 20},
+            Weighted { weight: 2, item: 21},
+            Weighted { weight: 0, item: 22},
+            Weighted { weight: 1, item: 23}],
+           [21, 21, 23]);
 
         // different weights
-        t!(vec!(Weighted { weight: 4, item: 30},
-                Weighted { weight: 3, item: 31}),
-           [30,30,30,30, 31,31,31]);
+        t!([Weighted { weight: 4, item: 30},
+            Weighted { weight: 3, item: 31}],
+           [30, 31, 30, 31, 30, 31, 30]);
 
         // check that we're binary searching
         // correctly with some vectors of odd
         // length.
-        t!(vec!(Weighted { weight: 1, item: 40},
-                Weighted { weight: 1, item: 41},
-                Weighted { weight: 1, item: 42},
-                Weighted { weight: 1, item: 43},
-                Weighted { weight: 1, item: 44}),
+        t!([Weighted { weight: 1, item: 40},
+            Weighted { weight: 1, item: 41},
+            Weighted { weight: 1, item: 42},
+            Weighted { weight: 1, item: 43},
+            Weighted { weight: 1, item: 44}],
            [40, 41, 42, 43, 44]);
-        t!(vec!(Weighted { weight: 1, item: 50},
-                Weighted { weight: 1, item: 51},
-                Weighted { weight: 1, item: 52},
-                Weighted { weight: 1, item: 53},
-                Weighted { weight: 1, item: 54},
-                Weighted { weight: 1, item: 55},
-                Weighted { weight: 1, item: 56}),
-           [50, 51, 52, 53, 54, 55, 56]);
+        t!([Weighted { weight: 1, item: 50},
+            Weighted { weight: 1, item: 51},
+            Weighted { weight: 1, item: 52},
+            Weighted { weight: 1, item: 53},
+            Weighted { weight: 1, item: 54},
+            Weighted { weight: 1, item: 55},
+            Weighted { weight: 1, item: 56}],
+           [50, 54, 51, 55, 52, 56, 53]);
     }
 
     #[test]
+    #[allow(deprecated)]
     fn test_weighted_clone_initialization() {
         let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
         let clone = initial.clone();
@@ -373,6 +570,7 @@ mod tests {
     }
 
     #[test] #[should_panic]
+    #[allow(deprecated)]
     fn test_weighted_clone_change_weight() {
         let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
         let mut clone = initial.clone();
@@ -381,6 +579,7 @@ mod tests {
     }
 
     #[test] #[should_panic]
+    #[allow(deprecated)]
     fn test_weighted_clone_change_item() {
         let initial : Weighted<u32> = Weighted {weight: 1, item: 1};
         let mut clone = initial.clone();
@@ -390,20 +589,33 @@ mod tests {
     }
 
     #[test] #[should_panic]
+    #[allow(deprecated)]
     fn test_weighted_choice_no_items() {
         WeightedChoice::<isize>::new(&mut []);
     }
     #[test] #[should_panic]
+    #[allow(deprecated)]
     fn test_weighted_choice_zero_weight() {
         WeightedChoice::new(&mut [Weighted { weight: 0, item: 0},
                                   Weighted { weight: 0, item: 1}]);
     }
     #[test] #[should_panic]
+    #[allow(deprecated)]
     fn test_weighted_choice_weight_overflows() {
-        let x = ::std::u32::MAX / 2; // x + x + 2 is the overflow
+        let x = ::core::u32::MAX / 2; // x + x + 2 is the overflow
         WeightedChoice::new(&mut [Weighted { weight: x, item: 0 },
                                   Weighted { weight: 1, item: 1 },
                                   Weighted { weight: x, item: 2 },
                                   Weighted { weight: 1, item: 3 }]);
     }
+
+    #[cfg(feature="std")]
+    #[test]
+    fn test_distributions_iter() {
+        use distributions::Normal;
+        let mut rng = ::test::rng(210);
+        let distr = Normal::new(10.0, 10.0);
+        let results: Vec<_> = distr.sample_iter(&mut rng).take(100).collect();
+        println!("{:?}", results);
+    }
 }
diff --git a/rand/src/distributions/normal.rs b/rand/src/distributions/normal.rs
index 280613d..b8d632e 100644
--- a/rand/src/distributions/normal.rs
+++ b/rand/src/distributions/normal.rs
@@ -1,49 +1,50 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
 //! The normal and derived distributions.
 
-use {Rng, Rand, Open01};
-use distributions::{ziggurat, ziggurat_tables, Sample, IndependentSample};
+use Rng;
+use distributions::{ziggurat_tables, Distribution, Open01};
+use distributions::utils::ziggurat;
 
-/// A wrapper around an `f64` to generate N(0, 1) random numbers
-/// (a.k.a.  a standard normal, or Gaussian).
+/// Samples floating-point numbers according to the normal distribution
+/// `N(0, 1)` (a.k.a. a standard normal, or Gaussian). This is equivalent to
+/// `Normal::new(0.0, 1.0)` but faster.
 ///
 /// See `Normal` for the general normal distribution.
 ///
-/// Implemented via the ZIGNOR variant[1] of the Ziggurat method.
+/// Implemented via the ZIGNOR variant[^1] of the Ziggurat method.
 ///
-/// [1]: Jurgen A. Doornik (2005). [*An Improved Ziggurat Method to
-/// Generate Normal Random
-/// Samples*](http://www.doornik.com/research/ziggurat.pdf). Nuffield
-/// College, Oxford
+/// [^1]: Jurgen A. Doornik (2005). [*An Improved Ziggurat Method to
+///       Generate Normal Random Samples*](
+///       https://www.doornik.com/research/ziggurat.pdf).
+///       Nuffield College, Oxford
 ///
 /// # Example
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::StandardNormal;
 ///
-/// ```rust
-/// use rand::distributions::normal::StandardNormal;
-///
-/// let StandardNormal(x) = rand::random();
-/// println!("{}", x);
+/// let val: f64 = SmallRng::from_entropy().sample(StandardNormal);
+/// println!("{}", val);
 /// ```
 #[derive(Clone, Copy, Debug)]
-pub struct StandardNormal(pub f64);
+pub struct StandardNormal;
 
-impl Rand for StandardNormal {
-    fn rand<R:Rng>(rng: &mut R) -> StandardNormal {
+impl Distribution<f64> for StandardNormal {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
         #[inline]
         fn pdf(x: f64) -> f64 {
             (-x*x/2.0).exp()
         }
         #[inline]
-        fn zero_case<R:Rng>(rng: &mut R, u: f64) -> f64 {
+        fn zero_case<R: Rng + ?Sized>(rng: &mut R, u: f64) -> f64 {
             // compute a random number in the tail by hand
 
             // strange initial conditions, because the loop is not
@@ -54,8 +55,8 @@ impl Rand for StandardNormal {
             let mut y = 0.0f64;
 
             while -2.0 * y < x * x {
-                let Open01(x_) = rng.gen::<Open01<f64>>();
-                let Open01(y_) = rng.gen::<Open01<f64>>();
+                let x_: f64 = rng.sample(Open01);
+                let y_: f64 = rng.sample(Open01);
 
                 x = x_.ln() / ziggurat_tables::ZIG_NORM_R;
                 y = y_.ln();
@@ -64,30 +65,33 @@ impl Rand for StandardNormal {
             if u < 0.0 { x - ziggurat_tables::ZIG_NORM_R } else { ziggurat_tables::ZIG_NORM_R - x }
         }
 
-        StandardNormal(ziggurat(
-            rng,
-            true, // this is symmetric
-            &ziggurat_tables::ZIG_NORM_X,
-            &ziggurat_tables::ZIG_NORM_F,
-            pdf, zero_case))
+        ziggurat(rng, true, // this is symmetric
+                 &ziggurat_tables::ZIG_NORM_X,
+                 &ziggurat_tables::ZIG_NORM_F,
+                 pdf, zero_case)
     }
 }
 
 /// The normal distribution `N(mean, std_dev**2)`.
 ///
-/// This uses the ZIGNOR variant of the Ziggurat method, see
-/// `StandardNormal` for more details.
+/// This uses the ZIGNOR variant of the Ziggurat method, see [`StandardNormal`]
+/// for more details.
+/// 
+/// Note that [`StandardNormal`] is an optimised implementation for mean 0, and
+/// standard deviation 1.
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{Normal, IndependentSample};
+/// ```
+/// use rand::distributions::{Normal, Distribution};
 ///
 /// // mean 2, standard deviation 3
 /// let normal = Normal::new(2.0, 3.0);
-/// let v = normal.ind_sample(&mut rand::thread_rng());
+/// let v = normal.sample(&mut rand::thread_rng());
 /// println!("{} is from a N(2, 9) distribution", v)
 /// ```
+///
+/// [`StandardNormal`]: struct.StandardNormal.html
 #[derive(Clone, Copy, Debug)]
 pub struct Normal {
     mean: f64,
@@ -105,17 +109,14 @@ impl Normal {
     pub fn new(mean: f64, std_dev: f64) -> Normal {
         assert!(std_dev >= 0.0, "Normal::new called with `std_dev` < 0");
         Normal {
-            mean: mean,
-            std_dev: std_dev
+            mean,
+            std_dev
         }
     }
 }
-impl Sample<f64> for Normal {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl IndependentSample<f64> for Normal {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        let StandardNormal(n) = rng.gen::<StandardNormal>();
+impl Distribution<f64> for Normal {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let n = rng.sample(StandardNormal);
         self.mean + self.std_dev * n
     }
 }
@@ -123,17 +124,17 @@ impl IndependentSample<f64> for Normal {
 
 /// The log-normal distribution `ln N(mean, std_dev**2)`.
 ///
-/// If `X` is log-normal distributed, then `ln(X)` is `N(mean,
-/// std_dev**2)` distributed.
+/// If `X` is log-normal distributed, then `ln(X)` is `N(mean, std_dev**2)`
+/// distributed.
 ///
 /// # Example
 ///
-/// ```rust
-/// use rand::distributions::{LogNormal, IndependentSample};
+/// ```
+/// use rand::distributions::{LogNormal, Distribution};
 ///
 /// // mean 2, standard deviation 3
 /// let log_normal = LogNormal::new(2.0, 3.0);
-/// let v = log_normal.ind_sample(&mut rand::thread_rng());
+/// let v = log_normal.sample(&mut rand::thread_rng());
 /// println!("{} is from an ln N(2, 9) distribution", v)
 /// ```
 #[derive(Clone, Copy, Debug)]
@@ -154,27 +155,23 @@ impl LogNormal {
         LogNormal { norm: Normal::new(mean, std_dev) }
     }
 }
-impl Sample<f64> for LogNormal {
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> f64 { self.ind_sample(rng) }
-}
-impl IndependentSample<f64> for LogNormal {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> f64 {
-        self.norm.ind_sample(rng).exp()
+impl Distribution<f64> for LogNormal {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        self.norm.sample(rng).exp()
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use distributions::{Sample, IndependentSample};
+    use distributions::Distribution;
     use super::{Normal, LogNormal};
 
     #[test]
     fn test_normal() {
-        let mut norm = Normal::new(10.0, 10.0);
-        let mut rng = ::test::rng();
+        let norm = Normal::new(10.0, 10.0);
+        let mut rng = ::test::rng(210);
         for _ in 0..1000 {
             norm.sample(&mut rng);
-            norm.ind_sample(&mut rng);
         }
     }
     #[test]
@@ -186,11 +183,10 @@ mod tests {
 
     #[test]
     fn test_log_normal() {
-        let mut lnorm = LogNormal::new(10.0, 10.0);
-        let mut rng = ::test::rng();
+        let lnorm = LogNormal::new(10.0, 10.0);
+        let mut rng = ::test::rng(211);
         for _ in 0..1000 {
             lnorm.sample(&mut rng);
-            lnorm.ind_sample(&mut rng);
         }
     }
     #[test]
diff --git a/rand/src/distributions/other.rs b/rand/src/distributions/other.rs
new file mode 100644
index 0000000..2295f79
--- /dev/null
+++ b/rand/src/distributions/other.rs
@@ -0,0 +1,219 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The implementations of the `Standard` distribution for other built-in types.
+
+use core::char;
+use core::num::Wrapping;
+
+use {Rng};
+use distributions::{Distribution, Standard, Uniform};
+
+// ----- Sampling distributions -----
+
+/// Sample a `char`, uniformly distributed over ASCII letters and numbers:
+/// a-z, A-Z and 0-9.
+/// 
+/// # Example
+///
+/// ```
+/// use std::iter;
+/// use rand::{Rng, thread_rng};
+/// use rand::distributions::Alphanumeric;
+/// 
+/// let mut rng = thread_rng();
+/// let chars: String = iter::repeat(())
+///         .map(|()| rng.sample(Alphanumeric))
+///         .take(7)
+///         .collect();
+/// println!("Random chars: {}", chars);
+/// ```
+#[derive(Debug)]
+pub struct Alphanumeric;
+
+
+// ----- Implementations of distributions -----
+
+impl Distribution<char> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> char {
+        // A valid `char` is either in the interval `[0, 0xD800)` or
+        // `(0xDFFF, 0x11_0000)`. All `char`s must therefore be in
+        // `[0, 0x11_0000)` but not in the "gap" `[0xD800, 0xDFFF]` which is
+        // reserved for surrogates. This is the size of that gap.
+        const GAP_SIZE: u32 = 0xDFFF - 0xD800 + 1;
+
+        // Uniform::new(0, 0x11_0000 - GAP_SIZE) can also be used but it
+        // seemed slower.
+        let range = Uniform::new(GAP_SIZE, 0x11_0000);
+
+        let mut n = range.sample(rng);
+        if n <= 0xDFFF {
+            n -= GAP_SIZE;
+        }
+        unsafe { char::from_u32_unchecked(n) }
+    }
+}
+
+impl Distribution<char> for Alphanumeric {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> char {
+        const RANGE: u32 = 26 + 26 + 10;
+        const GEN_ASCII_STR_CHARSET: &[u8] =
+            b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
+                abcdefghijklmnopqrstuvwxyz\
+                0123456789";
+        // We can pick from 62 characters. This is so close to a power of 2, 64,
+        // that we can do better than `Uniform`. Use a simple bitshift and
+        // rejection sampling. We do not use a bitmask, because for small RNGs
+        // the most significant bits are usually of higher quality.
+        loop {
+            let var = rng.next_u32() >> (32 - 6);
+            if var < RANGE {
+                return GEN_ASCII_STR_CHARSET[var as usize] as char
+            }
+        }
+    }
+}
+
+impl Distribution<bool> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> bool {
+        // We can compare against an arbitrary bit of an u32 to get a bool.
+        // Because the least significant bits of a lower quality RNG can have
+        // simple patterns, we compare against the most significant bit. This is
+        // easiest done using a sign test.
+        (rng.next_u32() as i32) < 0
+    }
+}
+
+macro_rules! tuple_impl {
+    // use variables to indicate the arity of the tuple
+    ($($tyvar:ident),* ) => {
+        // the trailing commas are for the 1 tuple
+        impl< $( $tyvar ),* >
+            Distribution<( $( $tyvar ),* , )>
+            for Standard
+            where $( Standard: Distribution<$tyvar> ),*
+        {
+            #[inline]
+            fn sample<R: Rng + ?Sized>(&self, _rng: &mut R) -> ( $( $tyvar ),* , ) {
+                (
+                    // use the $tyvar's to get the appropriate number of
+                    // repeats (they're not actually needed)
+                    $(
+                        _rng.gen::<$tyvar>()
+                    ),*
+                    ,
+                )
+            }
+        }
+    }
+}
+
+impl Distribution<()> for Standard {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, _: &mut R) -> () { () }
+}
+tuple_impl!{A}
+tuple_impl!{A, B}
+tuple_impl!{A, B, C}
+tuple_impl!{A, B, C, D}
+tuple_impl!{A, B, C, D, E}
+tuple_impl!{A, B, C, D, E, F}
+tuple_impl!{A, B, C, D, E, F, G}
+tuple_impl!{A, B, C, D, E, F, G, H}
+tuple_impl!{A, B, C, D, E, F, G, H, I}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J, K}
+tuple_impl!{A, B, C, D, E, F, G, H, I, J, K, L}
+
+macro_rules! array_impl {
+    // recursive, given at least one type parameter:
+    {$n:expr, $t:ident, $($ts:ident,)*} => {
+        array_impl!{($n - 1), $($ts,)*}
+
+        impl<T> Distribution<[T; $n]> for Standard where Standard: Distribution<T> {
+            #[inline]
+            fn sample<R: Rng + ?Sized>(&self, _rng: &mut R) -> [T; $n] {
+                [_rng.gen::<$t>(), $(_rng.gen::<$ts>()),*]
+            }
+        }
+    };
+    // empty case:
+    {$n:expr,} => {
+        impl<T> Distribution<[T; $n]> for Standard {
+            fn sample<R: Rng + ?Sized>(&self, _rng: &mut R) -> [T; $n] { [] }
+        }
+    };
+}
+
+array_impl!{32, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,}
+
+impl<T> Distribution<Option<T>> for Standard where Standard: Distribution<T> {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Option<T> {
+        // UFCS is needed here: https://github.com/rust-lang/rust/issues/24066
+        if rng.gen::<bool>() {
+            Some(rng.gen())
+        } else {
+            None
+        }
+    }
+}
+
+impl<T> Distribution<Wrapping<T>> for Standard where Standard: Distribution<T> {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Wrapping<T> {
+        Wrapping(rng.gen())
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use {Rng, RngCore, Standard};
+    use distributions::Alphanumeric;
+    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::string::String;
+
+    #[test]
+    fn test_misc() {
+        let rng: &mut RngCore = &mut ::test::rng(820);
+        
+        rng.sample::<char, _>(Standard);
+        rng.sample::<bool, _>(Standard);
+    }
+    
+    #[cfg(feature="alloc")]
+    #[test]
+    fn test_chars() {
+        use core::iter;
+        let mut rng = ::test::rng(805);
+
+        // Test by generating a relatively large number of chars, so we also
+        // take the rejection sampling path.
+        let word: String = iter::repeat(())
+                .map(|()| rng.gen::<char>()).take(1000).collect();
+        assert!(word.len() != 0);
+    }
+
+    #[test]
+    fn test_alphanumeric() {
+        let mut rng = ::test::rng(806);
+
+        // Test by generating a relatively large number of chars, so we also
+        // take the rejection sampling path.
+        let mut incorrect = false;
+        for _ in 0..100 {
+            let c = rng.sample(Alphanumeric);
+            incorrect |= !((c >= '0' && c <= '9') ||
+                           (c >= 'A' && c <= 'Z') ||
+                           (c >= 'a' && c <= 'z') );
+        }
+        assert!(incorrect == false);
+    }
+}
diff --git a/rand/src/distributions/pareto.rs b/rand/src/distributions/pareto.rs
new file mode 100644
index 0000000..744a157
--- /dev/null
+++ b/rand/src/distributions/pareto.rs
@@ -0,0 +1,74 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Pareto distribution.
+
+use Rng;
+use distributions::{Distribution, OpenClosed01};
+
+/// Samples floating-point numbers according to the Pareto distribution
+///
+/// # Example
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::Pareto;
+///
+/// let val: f64 = SmallRng::from_entropy().sample(Pareto::new(1., 2.));
+/// println!("{}", val);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Pareto {
+    scale: f64,
+    inv_neg_shape: f64,
+}
+
+impl Pareto {
+    /// Construct a new Pareto distribution with given `scale` and `shape`.
+    ///
+    /// In the literature, `scale` is commonly written as x<sub>m</sub> or k and
+    /// `shape` is often written as α.
+    ///
+    /// # Panics
+    ///
+    /// `scale` and `shape` have to be non-zero and positive.
+    pub fn new(scale: f64, shape: f64) -> Pareto {
+        assert!((scale > 0.) & (shape > 0.));
+        Pareto { scale, inv_neg_shape: -1.0 / shape }
+    }
+}
+
+impl Distribution<f64> for Pareto {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let u: f64 = rng.sample(OpenClosed01);
+        self.scale * u.powf(self.inv_neg_shape)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use distributions::Distribution;
+    use super::Pareto;
+
+    #[test]
+    #[should_panic]
+    fn invalid() {
+        Pareto::new(0., 0.);
+    }
+
+    #[test]
+    fn sample() {
+        let scale = 1.0;
+        let shape = 2.0;
+        let d = Pareto::new(scale, shape);
+        let mut rng = ::test::rng(1);
+        for _ in 0..1000 {
+            let r = d.sample(&mut rng);
+            assert!(r >= scale);
+        }
+    }
+}
diff --git a/rand/src/distributions/poisson.rs b/rand/src/distributions/poisson.rs
new file mode 100644
index 0000000..1244caa
--- /dev/null
+++ b/rand/src/distributions/poisson.rs
@@ -0,0 +1,157 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2016-2017 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Poisson distribution.
+
+use Rng;
+use distributions::{Distribution, Cauchy};
+use distributions::utils::log_gamma;
+
+/// The Poisson distribution `Poisson(lambda)`.
+///
+/// This distribution has a density function:
+/// `f(k) = lambda^k * exp(-lambda) / k!` for `k >= 0`.
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Poisson, Distribution};
+///
+/// let poi = Poisson::new(2.0);
+/// let v = poi.sample(&mut rand::thread_rng());
+/// println!("{} is from a Poisson(2) distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Poisson {
+    lambda: f64,
+    // precalculated values
+    exp_lambda: f64,
+    log_lambda: f64,
+    sqrt_2lambda: f64,
+    magic_val: f64,
+}
+
+impl Poisson {
+    /// Construct a new `Poisson` with the given shape parameter
+    /// `lambda`. Panics if `lambda <= 0`.
+    pub fn new(lambda: f64) -> Poisson {
+        assert!(lambda > 0.0, "Poisson::new called with lambda <= 0");
+        let log_lambda = lambda.ln();
+        Poisson {
+            lambda,
+            exp_lambda: (-lambda).exp(),
+            log_lambda,
+            sqrt_2lambda: (2.0 * lambda).sqrt(),
+            magic_val: lambda * log_lambda - log_gamma(1.0 + lambda),
+        }
+    }
+}
+
+impl Distribution<u64> for Poisson {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> u64 {
+        // using the algorithm from Numerical Recipes in C
+
+        // for low expected values use the Knuth method
+        if self.lambda < 12.0 {
+            let mut result = 0;
+            let mut p = 1.0;
+            while p > self.exp_lambda {
+                p *= rng.gen::<f64>();
+                result += 1;
+            }
+            result - 1
+        }
+        // high expected values - rejection method
+        else {
+            let mut int_result: u64;
+
+            // we use the Cauchy distribution as the comparison distribution
+            // f(x) ~ 1/(1+x^2)
+            let cauchy = Cauchy::new(0.0, 1.0);
+
+            loop {
+                let mut result;
+                let mut comp_dev;
+
+                loop {
+                    // draw from the Cauchy distribution
+                    comp_dev = rng.sample(cauchy);
+                    // shift the peak of the comparison ditribution
+                    result = self.sqrt_2lambda * comp_dev + self.lambda;
+                    // repeat the drawing until we are in the range of possible values
+                    if result >= 0.0 {
+                        break;
+                    }
+                }
+                // now the result is a random variable greater than 0 with Cauchy distribution
+                // the result should be an integer value
+                result = result.floor();
+                int_result = result as u64;
+
+                // this is the ratio of the Poisson distribution to the comparison distribution
+                // the magic value scales the distribution function to a range of approximately 0-1
+                // since it is not exact, we multiply the ratio by 0.9 to avoid ratios greater than 1
+                // this doesn't change the resulting distribution, only increases the rate of failed drawings
+                let check = 0.9 * (1.0 + comp_dev * comp_dev)
+                    * (result * self.log_lambda - log_gamma(1.0 + result) - self.magic_val).exp();
+
+                // check with uniform random value - if below the threshold, we are within the target distribution
+                if rng.gen::<f64>() <= check {
+                    break;
+                }
+            }
+            int_result
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use distributions::Distribution;
+    use super::Poisson;
+
+    #[test]
+    fn test_poisson_10() {
+        let poisson = Poisson::new(10.0);
+        let mut rng = ::test::rng(123);
+        let mut sum = 0;
+        for _ in 0..1000 {
+            sum += poisson.sample(&mut rng);
+        }
+        let avg = (sum as f64) / 1000.0;
+        println!("Poisson average: {}", avg);
+        assert!((avg - 10.0).abs() < 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    fn test_poisson_15() {
+        // Take the 'high expected values' path
+        let poisson = Poisson::new(15.0);
+        let mut rng = ::test::rng(123);
+        let mut sum = 0;
+        for _ in 0..1000 {
+            sum += poisson.sample(&mut rng);
+        }
+        let avg = (sum as f64) / 1000.0;
+        println!("Poisson average: {}", avg);
+        assert!((avg - 15.0).abs() < 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_poisson_invalid_lambda_zero() {
+        Poisson::new(0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_poisson_invalid_lambda_neg() {
+        Poisson::new(-10.0);
+    }
+}
diff --git a/rand/src/distributions/range.rs b/rand/src/distributions/range.rs
deleted file mode 100644
index 935a00a..0000000
--- a/rand/src/distributions/range.rs
+++ /dev/null
@@ -1,241 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Generating numbers between two others.
-
-// this is surprisingly complicated to be both generic & correct
-
-use core::num::Wrapping as w;
-
-use Rng;
-use distributions::{Sample, IndependentSample};
-
-/// Sample values uniformly between two bounds.
-///
-/// This gives a uniform distribution (assuming the RNG used to sample
-/// it is itself uniform & the `SampleRange` implementation for the
-/// given type is correct), even for edge cases like `low = 0u8`,
-/// `high = 170u8`, for which a naive modulo operation would return
-/// numbers less than 85 with double the probability to those greater
-/// than 85.
-///
-/// Types should attempt to sample in `[low, high)`, i.e., not
-/// including `high`, but this may be very difficult. All the
-/// primitive integer types satisfy this property, and the float types
-/// normally satisfy it, but rounding may mean `high` can occur.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::distributions::{IndependentSample, Range};
-///
-/// fn main() {
-///     let between = Range::new(10, 10000);
-///     let mut rng = rand::thread_rng();
-///     let mut sum = 0;
-///     for _ in 0..1000 {
-///         sum += between.ind_sample(&mut rng);
-///     }
-///     println!("{}", sum);
-/// }
-/// ```
-#[derive(Clone, Copy, Debug)]
-pub struct Range<X> {
-    low: X,
-    range: X,
-    accept_zone: X
-}
-
-impl<X: SampleRange + PartialOrd> Range<X> {
-    /// Create a new `Range` instance that samples uniformly from
-    /// `[low, high)`. Panics if `low >= high`.
-    pub fn new(low: X, high: X) -> Range<X> {
-        assert!(low < high, "Range::new called with `low >= high`");
-        SampleRange::construct_range(low, high)
-    }
-}
-
-impl<Sup: SampleRange> Sample<Sup> for Range<Sup> {
-    #[inline]
-    fn sample<R: Rng>(&mut self, rng: &mut R) -> Sup { self.ind_sample(rng) }
-}
-impl<Sup: SampleRange> IndependentSample<Sup> for Range<Sup> {
-    fn ind_sample<R: Rng>(&self, rng: &mut R) -> Sup {
-        SampleRange::sample_range(self, rng)
-    }
-}
-
-/// The helper trait for types that have a sensible way to sample
-/// uniformly between two values. This should not be used directly,
-/// and is only to facilitate `Range`.
-pub trait SampleRange : Sized {
-    /// Construct the `Range` object that `sample_range`
-    /// requires. This should not ever be called directly, only via
-    /// `Range::new`, which will check that `low < high`, so this
-    /// function doesn't have to repeat the check.
-    fn construct_range(low: Self, high: Self) -> Range<Self>;
-
-    /// Sample a value from the given `Range` with the given `Rng` as
-    /// a source of randomness.
-    fn sample_range<R: Rng>(r: &Range<Self>, rng: &mut R) -> Self;
-}
-
-macro_rules! integer_impl {
-    ($ty:ty, $unsigned:ident) => {
-        impl SampleRange for $ty {
-            // we play free and fast with unsigned vs signed here
-            // (when $ty is signed), but that's fine, since the
-            // contract of this macro is for $ty and $unsigned to be
-            // "bit-equal", so casting between them is a no-op & a
-            // bijection.
-
-            #[inline]
-            fn construct_range(low: $ty, high: $ty) -> Range<$ty> {
-                let range = (w(high as $unsigned) - w(low as $unsigned)).0;
-                let unsigned_max: $unsigned = ::core::$unsigned::MAX;
-
-                // this is the largest number that fits into $unsigned
-                // that `range` divides evenly, so, if we've sampled
-                // `n` uniformly from this region, then `n % range` is
-                // uniform in [0, range)
-                let zone = unsigned_max - unsigned_max % range;
-
-                Range {
-                    low: low,
-                    range: range as $ty,
-                    accept_zone: zone as $ty
-                }
-            }
-
-            #[inline]
-            fn sample_range<R: Rng>(r: &Range<$ty>, rng: &mut R) -> $ty {
-                loop {
-                    // rejection sample
-                    let v = rng.gen::<$unsigned>();
-                    // until we find something that fits into the
-                    // region which r.range evenly divides (this will
-                    // be uniformly distributed)
-                    if v < r.accept_zone as $unsigned {
-                        // and return it, with some adjustments
-                        return (w(r.low) + w((v % r.range as $unsigned) as $ty)).0;
-                    }
-                }
-            }
-        }
-    }
-}
-
-integer_impl! { i8, u8 }
-integer_impl! { i16, u16 }
-integer_impl! { i32, u32 }
-integer_impl! { i64, u64 }
-#[cfg(feature = "i128_support")]
-integer_impl! { i128, u128 }
-integer_impl! { isize, usize }
-integer_impl! { u8, u8 }
-integer_impl! { u16, u16 }
-integer_impl! { u32, u32 }
-integer_impl! { u64, u64 }
-#[cfg(feature = "i128_support")]
-integer_impl! { u128, u128 }
-integer_impl! { usize, usize }
-
-macro_rules! float_impl {
-    ($ty:ty) => {
-        impl SampleRange for $ty {
-            fn construct_range(low: $ty, high: $ty) -> Range<$ty> {
-                Range {
-                    low: low,
-                    range: high - low,
-                    accept_zone: 0.0 // unused
-                }
-            }
-            fn sample_range<R: Rng>(r: &Range<$ty>, rng: &mut R) -> $ty {
-                r.low + r.range * rng.gen::<$ty>()
-            }
-        }
-    }
-}
-
-float_impl! { f32 }
-float_impl! { f64 }
-
-#[cfg(test)]
-mod tests {
-    use distributions::{Sample, IndependentSample};
-    use super::Range as Range;
-
-    #[should_panic]
-    #[test]
-    fn test_range_bad_limits_equal() {
-        Range::new(10, 10);
-    }
-    #[should_panic]
-    #[test]
-    fn test_range_bad_limits_flipped() {
-        Range::new(10, 5);
-    }
-
-    #[test]
-    fn test_integers() {
-        let mut rng = ::test::rng();
-        macro_rules! t {
-            ($($ty:ident),*) => {{
-                $(
-                   let v: &[($ty, $ty)] = &[(0, 10),
-                                            (10, 127),
-                                            (::core::$ty::MIN, ::core::$ty::MAX)];
-                   for &(low, high) in v.iter() {
-                        let mut sampler: Range<$ty> = Range::new(low, high);
-                        for _ in 0..1000 {
-                            let v = sampler.sample(&mut rng);
-                            assert!(low <= v && v < high);
-                            let v = sampler.ind_sample(&mut rng);
-                            assert!(low <= v && v < high);
-                        }
-                    }
-                 )*
-            }}
-        }
-        #[cfg(not(feature = "i128_support"))]
-        t!(i8, i16, i32, i64, isize,
-           u8, u16, u32, u64, usize);
-        #[cfg(feature = "i128_support")]
-        t!(i8, i16, i32, i64, i128, isize,
-           u8, u16, u32, u64, u128, usize);
-    }
-
-    #[test]
-    fn test_floats() {
-        let mut rng = ::test::rng();
-        macro_rules! t {
-            ($($ty:ty),*) => {{
-                $(
-                   let v: &[($ty, $ty)] = &[(0.0, 100.0),
-                                            (-1e35, -1e25),
-                                            (1e-35, 1e-25),
-                                            (-1e35, 1e35)];
-                   for &(low, high) in v.iter() {
-                        let mut sampler: Range<$ty> = Range::new(low, high);
-                        for _ in 0..1000 {
-                            let v = sampler.sample(&mut rng);
-                            assert!(low <= v && v < high);
-                            let v = sampler.ind_sample(&mut rng);
-                            assert!(low <= v && v < high);
-                        }
-                    }
-                 )*
-            }}
-        }
-
-        t!(f32, f64)
-    }
-
-}
diff --git a/rand/src/distributions/triangular.rs b/rand/src/distributions/triangular.rs
new file mode 100644
index 0000000..a6eef5c
--- /dev/null
+++ b/rand/src/distributions/triangular.rs
@@ -0,0 +1,86 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//! The triangular distribution.
+
+use Rng;
+use distributions::{Distribution, Standard};
+
+/// The triangular distribution.
+///
+/// # Example
+///
+/// ```rust
+/// use rand::distributions::{Triangular, Distribution};
+///
+/// let d = Triangular::new(0., 5., 2.5);
+/// let v = d.sample(&mut rand::thread_rng());
+/// println!("{} is from a triangular distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Triangular {
+    min: f64,
+    max: f64,
+    mode: f64,
+}
+
+impl Triangular {
+    /// Construct a new `Triangular` with minimum `min`, maximum `max` and mode
+    /// `mode`.
+    ///
+    /// # Panics
+    ///
+    /// If `max < mode`, `mode < max` or `max == min`.
+    ///
+    #[inline]
+    pub fn new(min: f64, max: f64, mode: f64) -> Triangular {
+        assert!(max >= mode);
+        assert!(mode >= min);
+        assert!(max != min);
+        Triangular { min, max, mode }
+    }
+}
+
+impl Distribution<f64> for Triangular {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let f: f64 = rng.sample(Standard);
+        let diff_mode_min = self.mode - self.min;
+        let diff_max_min = self.max - self.min;
+        if f * diff_max_min < diff_mode_min {
+            self.min + (f * diff_max_min * diff_mode_min).sqrt()
+        } else {
+            self.max - ((1. - f) * diff_max_min * (self.max - self.mode)).sqrt()
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use distributions::Distribution;
+    use super::Triangular;
+
+    #[test]
+    fn test_new() {
+        for &(min, max, mode) in &[
+            (-1., 1., 0.), (1., 2., 1.), (5., 25., 25.), (1e-5, 1e5, 1e-3),
+            (0., 1., 0.9), (-4., -0.5, -2.), (-13.039, 8.41, 1.17),
+        ] {
+            println!("{} {} {}", min, max, mode);
+            let _ = Triangular::new(min, max, mode);
+        }
+    }
+
+    #[test]
+    fn test_sample() {
+        let norm = Triangular::new(0., 1., 0.5);
+        let mut rng = ::test::rng(1);
+        for _ in 0..1000 {
+            norm.sample(&mut rng);
+        }
+    }
+}
diff --git a/rand/src/distributions/uniform.rs b/rand/src/distributions/uniform.rs
new file mode 100644
index 0000000..5fb89e3
--- /dev/null
+++ b/rand/src/distributions/uniform.rs
@@ -0,0 +1,1297 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2017 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A distribution uniformly sampling numbers within a given range.
+//!
+//! [`Uniform`] is the standard distribution to sample uniformly from a range;
+//! e.g. `Uniform::new_inclusive(1, 6)` can sample integers from 1 to 6, like a
+//! standard die. [`Rng::gen_range`] supports any type supported by
+//! [`Uniform`].
+//!
+//! This distribution is provided with support for several primitive types
+//! (all integer and floating-point types) as well as `std::time::Duration`,
+//! and supports extension to user-defined types via a type-specific *back-end*
+//! implementation.
+//!
+//! The types [`UniformInt`], [`UniformFloat`] and [`UniformDuration`] are the
+//! back-ends supporting sampling from primitive integer and floating-point
+//! ranges as well as from `std::time::Duration`; these types do not normally
+//! need to be used directly (unless implementing a derived back-end).
+//!
+//! # Example usage
+//!
+//! ```
+//! use rand::{Rng, thread_rng};
+//! use rand::distributions::Uniform;
+//!
+//! let mut rng = thread_rng();
+//! let side = Uniform::new(-10.0, 10.0);
+//!
+//! // sample between 1 and 10 points
+//! for _ in 0..rng.gen_range(1, 11) {
+//!     // sample a point from the square with sides -10 - 10 in two dimensions
+//!     let (x, y) = (rng.sample(side), rng.sample(side));
+//!     println!("Point: {}, {}", x, y);
+//! }
+//! ```
+//!
+//! # Extending `Uniform` to support a custom type
+//!
+//! To extend [`Uniform`] to support your own types, write a back-end which
+//! implements the [`UniformSampler`] trait, then implement the [`SampleUniform`]
+//! helper trait to "register" your back-end. See the `MyF32` example below.
+//!
+//! At a minimum, the back-end needs to store any parameters needed for sampling
+//! (e.g. the target range) and implement `new`, `new_inclusive` and `sample`.
+//! Those methods should include an assert to check the range is valid (i.e.
+//! `low < high`). The example below merely wraps another back-end.
+//!
+//! The `new`, `new_inclusive` and `sample_single` functions use arguments of
+//! type SampleBorrow<X> in order to support passing in values by reference or
+//! by value. In the implementation of these functions, you can choose to
+//! simply use the reference returned by [`SampleBorrow::borrow`], or you can choose
+//! to copy or clone the value, whatever is appropriate for your type.
+//!
+//! ```
+//! use rand::prelude::*;
+//! use rand::distributions::uniform::{Uniform, SampleUniform,
+//!         UniformSampler, UniformFloat, SampleBorrow};
+//!
+//! struct MyF32(f32);
+//!
+//! #[derive(Clone, Copy, Debug)]
+//! struct UniformMyF32 {
+//!     inner: UniformFloat<f32>,
+//! }
+//!
+//! impl UniformSampler for UniformMyF32 {
+//!     type X = MyF32;
+//!     fn new<B1, B2>(low: B1, high: B2) -> Self
+//!         where B1: SampleBorrow<Self::X> + Sized,
+//!               B2: SampleBorrow<Self::X> + Sized
+//!     {
+//!         UniformMyF32 {
+//!             inner: UniformFloat::<f32>::new(low.borrow().0, high.borrow().0),
+//!         }
+//!     }
+//!     fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+//!         where B1: SampleBorrow<Self::X> + Sized,
+//!               B2: SampleBorrow<Self::X> + Sized
+//!     {
+//!         UniformSampler::new(low, high)
+//!     }
+//!     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
+//!         MyF32(self.inner.sample(rng))
+//!     }
+//! }
+//!
+//! impl SampleUniform for MyF32 {
+//!     type Sampler = UniformMyF32;
+//! }
+//!
+//! let (low, high) = (MyF32(17.0f32), MyF32(22.0f32));
+//! let uniform = Uniform::new(low, high);
+//! let x = uniform.sample(&mut thread_rng());
+//! ```
+//!
+//! [`Uniform`]: struct.Uniform.html
+//! [`Rng::gen_range`]: ../../trait.Rng.html#method.gen_range
+//! [`SampleUniform`]: trait.SampleUniform.html
+//! [`UniformSampler`]: trait.UniformSampler.html
+//! [`UniformInt`]: struct.UniformInt.html
+//! [`UniformFloat`]: struct.UniformFloat.html
+//! [`UniformDuration`]: struct.UniformDuration.html
+//! [`SampleBorrow::borrow`]: trait.SampleBorrow.html#method.borrow
+
+#[cfg(feature = "std")]
+use std::time::Duration;
+#[cfg(all(not(feature = "std"), rust_1_25))]
+use core::time::Duration;
+
+use Rng;
+use distributions::Distribution;
+use distributions::float::IntoFloat;
+use distributions::utils::{WideningMultiply, FloatSIMDUtils, FloatAsSIMD, BoolAsSIMD};
+
+#[cfg(not(feature = "std"))]
+#[allow(unused_imports)] // rustc doesn't detect that this is actually used
+use distributions::utils::Float;
+
+
+#[cfg(feature="simd_support")]
+use packed_simd::*;
+
+/// Sample values uniformly between two bounds.
+///
+/// [`Uniform::new`] and [`Uniform::new_inclusive`] construct a uniform
+/// distribution sampling from the given range; these functions may do extra
+/// work up front to make sampling of multiple values faster.
+///
+/// When sampling from a constant range, many calculations can happen at
+/// compile-time and all methods should be fast; for floating-point ranges and
+/// the full range of integer types this should have comparable performance to
+/// the `Standard` distribution.
+///
+/// Steps are taken to avoid bias which might be present in naive
+/// implementations; for example `rng.gen::<u8>() % 170` samples from the range
+/// `[0, 169]` but is twice as likely to select numbers less than 85 than other
+/// values. Further, the implementations here give more weight to the high-bits
+/// generated by the RNG than the low bits, since with some RNGs the low-bits
+/// are of lower quality than the high bits.
+///
+/// Implementations must sample in `[low, high)` range for
+/// `Uniform::new(low, high)`, i.e., excluding `high`. In particular care must
+/// be taken to ensure that rounding never results values `< low` or `>= high`.
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Distribution, Uniform};
+///
+/// fn main() {
+///     let between = Uniform::from(10..10000);
+///     let mut rng = rand::thread_rng();
+///     let mut sum = 0;
+///     for _ in 0..1000 {
+///         sum += between.sample(&mut rng);
+///     }
+///     println!("{}", sum);
+/// }
+/// ```
+///
+/// [`Uniform::new`]: struct.Uniform.html#method.new
+/// [`Uniform::new_inclusive`]: struct.Uniform.html#method.new_inclusive
+/// [`new`]: struct.Uniform.html#method.new
+/// [`new_inclusive`]: struct.Uniform.html#method.new_inclusive
+#[derive(Clone, Copy, Debug)]
+pub struct Uniform<X: SampleUniform> {
+    inner: X::Sampler,
+}
+
+impl<X: SampleUniform> Uniform<X> {
+    /// Create a new `Uniform` instance which samples uniformly from the half
+    /// open range `[low, high)` (excluding `high`). Panics if `low >= high`.
+    pub fn new<B1, B2>(low: B1, high: B2) -> Uniform<X>
+        where B1: SampleBorrow<X> + Sized,
+              B2: SampleBorrow<X> + Sized
+    {
+        Uniform { inner: X::Sampler::new(low, high) }
+    }
+
+    /// Create a new `Uniform` instance which samples uniformly from the closed
+    /// range `[low, high]` (inclusive). Panics if `low > high`.
+    pub fn new_inclusive<B1, B2>(low: B1, high: B2) -> Uniform<X>
+        where B1: SampleBorrow<X> + Sized,
+              B2: SampleBorrow<X> + Sized
+    {
+        Uniform { inner: X::Sampler::new_inclusive(low, high) }
+    }
+}
+
+impl<X: SampleUniform> Distribution<X> for Uniform<X> {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> X {
+        self.inner.sample(rng)
+    }
+}
+
+/// Helper trait for creating objects using the correct implementation of
+/// [`UniformSampler`] for the sampling type.
+///
+/// See the [module documentation] on how to implement [`Uniform`] range
+/// sampling for a custom type.
+///
+/// [`UniformSampler`]: trait.UniformSampler.html
+/// [module documentation]: index.html
+/// [`Uniform`]: struct.Uniform.html
+pub trait SampleUniform: Sized {
+    /// The `UniformSampler` implementation supporting type `X`.
+    type Sampler: UniformSampler<X = Self>;
+}
+
+/// Helper trait handling actual uniform sampling.
+///
+/// See the [module documentation] on how to implement [`Uniform`] range
+/// sampling for a custom type.
+///
+/// Implementation of [`sample_single`] is optional, and is only useful when
+/// the implementation can be faster than `Self::new(low, high).sample(rng)`.
+///
+/// [module documentation]: index.html
+/// [`Uniform`]: struct.Uniform.html
+/// [`sample_single`]: trait.UniformSampler.html#method.sample_single
+pub trait UniformSampler: Sized {
+    /// The type sampled by this implementation.
+    type X;
+
+    /// Construct self, with inclusive lower bound and exclusive upper bound
+    /// `[low, high)`.
+    ///
+    /// Usually users should not call this directly but instead use
+    /// `Uniform::new`, which asserts that `low < high` before calling this.
+    fn new<B1, B2>(low: B1, high: B2) -> Self
+        where B1: SampleBorrow<Self::X> + Sized,
+              B2: SampleBorrow<Self::X> + Sized;
+
+    /// Construct self, with inclusive bounds `[low, high]`.
+    ///
+    /// Usually users should not call this directly but instead use
+    /// `Uniform::new_inclusive`, which asserts that `low <= high` before
+    /// calling this.
+    fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+        where B1: SampleBorrow<Self::X> + Sized,
+              B2: SampleBorrow<Self::X> + Sized;
+
+    /// Sample a value.
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X;
+
+    /// Sample a single value uniformly from a range with inclusive lower bound
+    /// and exclusive upper bound `[low, high)`.
+    ///
+    /// Usually users should not call this directly but instead use
+    /// `Uniform::sample_single`, which asserts that `low < high` before calling
+    /// this.
+    ///
+    /// Via this method, implementations can provide a method optimized for
+    /// sampling only a single value from the specified range. The default
+    /// implementation simply calls `UniformSampler::new` then `sample` on the
+    /// result.
+    fn sample_single<R: Rng + ?Sized, B1, B2>(low: B1, high: B2, rng: &mut R)
+        -> Self::X
+        where B1: SampleBorrow<Self::X> + Sized,
+              B2: SampleBorrow<Self::X> + Sized
+    {
+        let uniform: Self = UniformSampler::new(low, high);
+        uniform.sample(rng)
+    }
+}
+
+impl<X: SampleUniform> From<::core::ops::Range<X>> for Uniform<X> {
+    fn from(r: ::core::ops::Range<X>) -> Uniform<X> {
+        Uniform::new(r.start, r.end)
+    }
+}
+
+#[cfg(rust_1_27)]
+impl<X: SampleUniform> From<::core::ops::RangeInclusive<X>> for Uniform<X> {
+    fn from(r: ::core::ops::RangeInclusive<X>) -> Uniform<X> {
+        Uniform::new_inclusive(r.start(), r.end())
+    }
+}
+
+/// Helper trait similar to [`Borrow`] but implemented
+/// only for SampleUniform and references to SampleUniform in
+/// order to resolve ambiguity issues.
+///
+/// [`Borrow`]: https://doc.rust-lang.org/std/borrow/trait.Borrow.html
+pub trait SampleBorrow<Borrowed> {
+    /// Immutably borrows from an owned value. See [`Borrow::borrow`]
+    ///
+    /// [`Borrow::borrow`]: https://doc.rust-lang.org/std/borrow/trait.Borrow.html#tymethod.borrow
+    fn borrow(&self) -> &Borrowed;
+}
+impl<Borrowed> SampleBorrow<Borrowed> for Borrowed where Borrowed: SampleUniform {
+    #[inline(always)]
+    fn borrow(&self) -> &Borrowed { self }
+}
+impl<'a, Borrowed> SampleBorrow<Borrowed> for &'a Borrowed where Borrowed: SampleUniform {
+    #[inline(always)]
+   fn borrow(&self) -> &Borrowed { *self }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+// What follows are all back-ends.
+
+
+/// The back-end implementing [`UniformSampler`] for integer types.
+///
+/// Unless you are implementing [`UniformSampler`] for your own type, this type
+/// should not be used directly, use [`Uniform`] instead.
+///
+/// # Implementation notes
+///
+/// For a closed range, the number of possible numbers we should generate is
+/// `range = (high - low + 1)`. It is not possible to end up with a uniform
+/// distribution if we map *all* the random integers that can be generated to
+/// this range. We have to map integers from a `zone` that is a multiple of the
+/// range. The rest of the integers, that cause a bias, are rejected.
+///
+/// The problem with `range` is that to cover the full range of the type, it has
+/// to store `unsigned_max + 1`, which can't be represented. But if the range
+/// covers the full range of the type, no modulus is needed. A range of size 0
+/// can't exist, so we use that to represent this special case. Wrapping
+/// arithmetic even makes representing `unsigned_max + 1` as 0 simple.
+///
+/// We don't calculate `zone` directly, but first calculate the number of
+/// integers to reject. To handle `unsigned_max + 1` not fitting in the type,
+/// we use:
+/// `ints_to_reject = (unsigned_max + 1) % range;`
+/// `ints_to_reject = (unsigned_max - range + 1) % range;`
+///
+/// The smallest integer PRNGs generate is `u32`. That is why for small integer
+/// sizes (`i8`/`u8` and `i16`/`u16`) there is an optimization: don't pick the
+/// largest zone that can fit in the small type, but pick the largest zone that
+/// can fit in an `u32`. `ints_to_reject` is always less than half the size of
+/// the small integer. This means the first bit of `zone` is always 1, and so
+/// are all the other preceding bits of a larger integer. The easiest way to
+/// grow the `zone` for the larger type is to simply sign extend it.
+///
+/// An alternative to using a modulus is widening multiply: After a widening
+/// multiply by `range`, the result is in the high word. Then comparing the low
+/// word against `zone` makes sure our distribution is uniform.
+///
+/// [`UniformSampler`]: trait.UniformSampler.html
+/// [`Uniform`]: struct.Uniform.html
+#[derive(Clone, Copy, Debug)]
+pub struct UniformInt<X> {
+    low: X,
+    range: X,
+    zone: X,
+}
+
+macro_rules! uniform_int_impl {
+    ($ty:ty, $signed:ty, $unsigned:ident,
+     $i_large:ident, $u_large:ident) => {
+        impl SampleUniform for $ty {
+            type Sampler = UniformInt<$ty>;
+        }
+
+        impl UniformSampler for UniformInt<$ty> {
+            // We play free and fast with unsigned vs signed here
+            // (when $ty is signed), but that's fine, since the
+            // contract of this macro is for $ty and $unsigned to be
+            // "bit-equal", so casting between them is a no-op.
+
+            type X = $ty;
+
+            #[inline] // if the range is constant, this helps LLVM to do the
+                      // calculations at compile-time.
+            fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low < high, "Uniform::new called with `low >= high`");
+                UniformSampler::new_inclusive(low, high - 1)
+            }
+
+            #[inline] // if the range is constant, this helps LLVM to do the
+                      // calculations at compile-time.
+            fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low <= high,
+                        "Uniform::new_inclusive called with `low > high`");
+                let unsigned_max = ::core::$unsigned::MAX;
+
+                let range = high.wrapping_sub(low).wrapping_add(1) as $unsigned;
+                let ints_to_reject =
+                    if range > 0 {
+                        (unsigned_max - range + 1) % range
+                    } else {
+                        0
+                    };
+                let zone = unsigned_max - ints_to_reject;
+
+                UniformInt {
+                    low: low,
+                    // These are really $unsigned values, but store as $ty:
+                    range: range as $ty,
+                    zone: zone as $ty
+                }
+            }
+
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
+                let range = self.range as $unsigned as $u_large;
+                if range > 0 {
+                    // Grow `zone` to fit a type of at least 32 bits, by
+                    // sign-extending it (the first bit is always 1, so are all
+                    // the preceding bits of the larger type).
+                    // For types that already have the right size, all the
+                    // casting is a no-op.
+                    let zone = self.zone as $signed as $i_large as $u_large;
+                    loop {
+                        let v: $u_large = rng.gen();
+                        let (hi, lo) = v.wmul(range);
+                        if lo <= zone {
+                            return self.low.wrapping_add(hi as $ty);
+                        }
+                    }
+                } else {
+                    // Sample from the entire integer range.
+                    rng.gen()
+                }
+            }
+
+            fn sample_single<R: Rng + ?Sized, B1, B2>(low_b: B1, high_b: B2, rng: &mut R)
+                -> Self::X
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low < high,
+                        "Uniform::sample_single called with low >= high");
+                let range = high.wrapping_sub(low) as $unsigned as $u_large;
+                let zone =
+                    if ::core::$unsigned::MAX <= ::core::u16::MAX as $unsigned {
+                        // Using a modulus is faster than the approximation for
+                        // i8 and i16. I suppose we trade the cost of one
+                        // modulus for near-perfect branch prediction.
+                        let unsigned_max: $u_large = ::core::$u_large::MAX;
+                        let ints_to_reject = (unsigned_max - range + 1) % range;
+                        unsigned_max - ints_to_reject
+                    } else {
+                        // conservative but fast approximation
+                       range << range.leading_zeros()
+                    };
+
+                loop {
+                    let v: $u_large = rng.gen();
+                    let (hi, lo) = v.wmul(range);
+                    if lo <= zone {
+                        return low.wrapping_add(hi as $ty);
+                    }
+                }
+            }
+        }
+    }
+}
+
+uniform_int_impl! { i8, i8, u8, i32, u32 }
+uniform_int_impl! { i16, i16, u16, i32, u32 }
+uniform_int_impl! { i32, i32, u32, i32, u32 }
+uniform_int_impl! { i64, i64, u64, i64, u64 }
+#[cfg(rust_1_26)]
+uniform_int_impl! { i128, i128, u128, u128, u128 }
+uniform_int_impl! { isize, isize, usize, isize, usize }
+uniform_int_impl! { u8, i8, u8, i32, u32 }
+uniform_int_impl! { u16, i16, u16, i32, u32 }
+uniform_int_impl! { u32, i32, u32, i32, u32 }
+uniform_int_impl! { u64, i64, u64, i64, u64 }
+uniform_int_impl! { usize, isize, usize, isize, usize }
+#[cfg(rust_1_26)]
+uniform_int_impl! { u128, u128, u128, i128, u128 }
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+macro_rules! uniform_simd_int_impl {
+    ($ty:ident, $unsigned:ident, $u_scalar:ident) => {
+        // The "pick the largest zone that can fit in an `u32`" optimization
+        // is less useful here. Multiple lanes complicate things, we don't
+        // know the PRNG's minimal output size, and casting to a larger vector
+        // is generally a bad idea for SIMD performance. The user can still
+        // implement it manually.
+
+        // TODO: look into `Uniform::<u32x4>::new(0u32, 100)` functionality
+        //       perhaps `impl SampleUniform for $u_scalar`?
+        impl SampleUniform for $ty {
+            type Sampler = UniformInt<$ty>;
+        }
+
+        impl UniformSampler for UniformInt<$ty> {
+            type X = $ty;
+
+            #[inline] // if the range is constant, this helps LLVM to do the
+                      // calculations at compile-time.
+            fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low.lt(high).all(), "Uniform::new called with `low >= high`");
+                UniformSampler::new_inclusive(low, high - 1)
+            }
+
+            #[inline] // if the range is constant, this helps LLVM to do the
+                      // calculations at compile-time.
+            fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low.le(high).all(),
+                        "Uniform::new_inclusive called with `low > high`");
+                let unsigned_max = ::core::$u_scalar::MAX;
+
+                // NOTE: these may need to be replaced with explicitly
+                // wrapping operations if `packed_simd` changes
+                let range: $unsigned = ((high - low) + 1).cast();
+                // `% 0` will panic at runtime.
+                let not_full_range = range.gt($unsigned::splat(0));
+                // replacing 0 with `unsigned_max` allows a faster `select`
+                // with bitwise OR
+                let modulo = not_full_range.select(range, $unsigned::splat(unsigned_max));
+                // wrapping addition
+                let ints_to_reject = (unsigned_max - range + 1) % modulo;
+                // When `range` is 0, `lo` of `v.wmul(range)` will always be
+                // zero which means only one sample is needed.
+                let zone = unsigned_max - ints_to_reject;
+
+                UniformInt {
+                    low: low,
+                    // These are really $unsigned values, but store as $ty:
+                    range: range.cast(),
+                    zone: zone.cast(),
+                }
+            }
+
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
+                let range: $unsigned = self.range.cast();
+                let zone: $unsigned = self.zone.cast();
+
+                // This might seem very slow, generating a whole new
+                // SIMD vector for every sample rejection. For most uses
+                // though, the chance of rejection is small and provides good
+                // general performance. With multiple lanes, that chance is
+                // multiplied. To mitigate this, we replace only the lanes of
+                // the vector which fail, iteratively reducing the chance of
+                // rejection. The replacement method does however add a little
+                // overhead. Benchmarking or calculating probabilities might
+                // reveal contexts where this replacement method is slower.
+                let mut v: $unsigned = rng.gen();
+                loop {
+                    let (hi, lo) = v.wmul(range);
+                    let mask = lo.le(zone);
+                    if mask.all() {
+                        let hi: $ty = hi.cast();
+                        // wrapping addition
+                        let result = self.low + hi;
+                        // `select` here compiles to a blend operation
+                        // When `range.eq(0).none()` the compare and blend
+                        // operations are avoided.
+                        let v: $ty = v.cast();
+                        return range.gt($unsigned::splat(0)).select(result, v);
+                    }
+                    // Replace only the failing lanes
+                    v = mask.select(v, rng.gen());
+                }
+            }
+        }
+    };
+
+    // bulk implementation
+    ($(($unsigned:ident, $signed:ident),)+ $u_scalar:ident) => {
+        $(
+            uniform_simd_int_impl!($unsigned, $unsigned, $u_scalar);
+            uniform_simd_int_impl!($signed, $unsigned, $u_scalar);
+        )+
+    };
+}
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+uniform_simd_int_impl! {
+    (u64x2, i64x2),
+    (u64x4, i64x4),
+    (u64x8, i64x8),
+    u64
+}
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+uniform_simd_int_impl! {
+    (u32x2, i32x2),
+    (u32x4, i32x4),
+    (u32x8, i32x8),
+    (u32x16, i32x16),
+    u32
+}
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+uniform_simd_int_impl! {
+    (u16x2, i16x2),
+    (u16x4, i16x4),
+    (u16x8, i16x8),
+    (u16x16, i16x16),
+    (u16x32, i16x32),
+    u16
+}
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+uniform_simd_int_impl! {
+    (u8x2, i8x2),
+    (u8x4, i8x4),
+    (u8x8, i8x8),
+    (u8x16, i8x16),
+    (u8x32, i8x32),
+    (u8x64, i8x64),
+    u8
+}
+
+
+/// The back-end implementing [`UniformSampler`] for floating-point types.
+///
+/// Unless you are implementing [`UniformSampler`] for your own type, this type
+/// should not be used directly, use [`Uniform`] instead.
+///
+/// # Implementation notes
+///
+/// Instead of generating a float in the `[0, 1)` range using [`Standard`], the
+/// `UniformFloat` implementation converts the output of an PRNG itself. This
+/// way one or two steps can be optimized out.
+///
+/// The floats are first converted to a value in the `[1, 2)` interval using a
+/// transmute-based method, and then mapped to the expected range with a
+/// multiply and addition. Values produced this way have what equals 22 bits of
+/// random digits for an `f32`, and 52 for an `f64`.
+///
+/// [`UniformSampler`]: trait.UniformSampler.html
+/// [`new`]: trait.UniformSampler.html#tymethod.new
+/// [`new_inclusive`]: trait.UniformSampler.html#tymethod.new_inclusive
+/// [`Uniform`]: struct.Uniform.html
+/// [`Standard`]: ../struct.Standard.html
+#[derive(Clone, Copy, Debug)]
+pub struct UniformFloat<X> {
+    low: X,
+    scale: X,
+}
+
+macro_rules! uniform_float_impl {
+    ($ty:ty, $uty:ident, $f_scalar:ident, $u_scalar:ident, $bits_to_discard:expr) => {
+        impl SampleUniform for $ty {
+            type Sampler = UniformFloat<$ty>;
+        }
+
+        impl UniformSampler for UniformFloat<$ty> {
+            type X = $ty;
+
+            fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low.all_lt(high),
+                        "Uniform::new called with `low >= high`");
+                assert!(low.all_finite() && high.all_finite(),
+                        "Uniform::new called with non-finite boundaries");
+                let max_rand = <$ty>::splat((::core::$u_scalar::MAX >> $bits_to_discard)
+                                            .into_float_with_exponent(0) - 1.0);
+
+                let mut scale = high - low;
+
+                loop {
+                    let mask = (scale * max_rand + low).ge_mask(high);
+                    if mask.none() {
+                        break;
+                    }
+                    scale = scale.decrease_masked(mask);
+                }
+
+                debug_assert!(<$ty>::splat(0.0).all_le(scale));
+
+                UniformFloat { low, scale }
+            }
+
+            fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low.all_le(high),
+                        "Uniform::new_inclusive called with `low > high`");
+                assert!(low.all_finite() && high.all_finite(),
+                        "Uniform::new_inclusive called with non-finite boundaries");
+                let max_rand = <$ty>::splat((::core::$u_scalar::MAX >> $bits_to_discard)
+                                            .into_float_with_exponent(0) - 1.0);
+
+                let mut scale = (high - low) / max_rand;
+
+                loop {
+                    let mask = (scale * max_rand + low).gt_mask(high);
+                    if mask.none() {
+                        break;
+                    }
+                    scale = scale.decrease_masked(mask);
+                }
+
+                debug_assert!(<$ty>::splat(0.0).all_le(scale));
+
+                UniformFloat { low, scale }
+            }
+
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
+                // Generate a value in the range [1, 2)
+                let value1_2 = (rng.gen::<$uty>() >> $bits_to_discard)
+                               .into_float_with_exponent(0);
+
+                // Get a value in the range [0, 1) in order to avoid
+                // overflowing into infinity when multiplying with scale
+                let value0_1 = value1_2 - 1.0;
+
+                // We don't use `f64::mul_add`, because it is not available with
+                // `no_std`. Furthermore, it is slower for some targets (but
+                // faster for others). However, the order of multiplication and
+                // addition is important, because on some platforms (e.g. ARM)
+                // it will be optimized to a single (non-FMA) instruction.
+                value0_1 * self.scale + self.low
+            }
+
+            #[inline]
+            fn sample_single<R: Rng + ?Sized, B1, B2>(low_b: B1, high_b: B2, rng: &mut R)
+                -> Self::X
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                let low = *low_b.borrow();
+                let high = *high_b.borrow();
+                assert!(low.all_lt(high),
+                        "Uniform::sample_single called with low >= high");
+                let mut scale = high - low;
+
+                loop {
+                    // Generate a value in the range [1, 2)
+                    let value1_2 = (rng.gen::<$uty>() >> $bits_to_discard)
+                                   .into_float_with_exponent(0);
+
+                    // Get a value in the range [0, 1) in order to avoid
+                    // overflowing into infinity when multiplying with scale
+                    let value0_1 = value1_2 - 1.0;
+
+                    // Doing multiply before addition allows some architectures
+                    // to use a single instruction.
+                    let res = value0_1 * scale + low;
+
+                    debug_assert!(low.all_le(res) || !scale.all_finite());
+                    if res.all_lt(high) {
+                        return res;
+                    }
+
+                    // This handles a number of edge cases.
+                    // * `low` or `high` is NaN. In this case `scale` and
+                    //   `res` are going to end up as NaN.
+                    // * `low` is negative infinity and `high` is finite.
+                    //   `scale` is going to be infinite and `res` will be
+                    //   NaN.
+                    // * `high` is positive infinity and `low` is finite.
+                    //   `scale` is going to be infinite and `res` will
+                    //   be infinite or NaN (if value0_1 is 0).
+                    // * `low` is negative infinity and `high` is positive
+                    //   infinity. `scale` will be infinite and `res` will
+                    //   be NaN.
+                    // * `low` and `high` are finite, but `high - low`
+                    //   overflows to infinite. `scale` will be infinite
+                    //   and `res` will be infinite or NaN (if value0_1 is 0).
+                    // So if `high` or `low` are non-finite, we are guaranteed
+                    // to fail the `res < high` check above and end up here.
+                    //
+                    // While we technically should check for non-finite `low`
+                    // and `high` before entering the loop, by doing the checks
+                    // here instead, we allow the common case to avoid these
+                    // checks. But we are still guaranteed that if `low` or
+                    // `high` are non-finite we'll end up here and can do the
+                    // appropriate checks.
+                    //
+                    // Likewise `high - low` overflowing to infinity is also
+                    // rare, so handle it here after the common case.
+                    let mask = !scale.finite_mask();
+                    if mask.any() {
+                        assert!(low.all_finite() && high.all_finite(),
+                                "Uniform::sample_single called with non-finite boundaries");
+                        scale = scale.decrease_masked(mask);
+                    }
+                }
+            }
+        }
+    }
+}
+
+uniform_float_impl! { f32, u32, f32, u32, 32 - 23 }
+uniform_float_impl! { f64, u64, f64, u64, 64 - 52 }
+
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f32x2, u32x2, f32, u32, 32 - 23 }
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f32x4, u32x4, f32, u32, 32 - 23 }
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f32x8, u32x8, f32, u32, 32 - 23 }
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f32x16, u32x16, f32, u32, 32 - 23 }
+
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f64x2, u64x2, f64, u64, 64 - 52 }
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f64x4, u64x4, f64, u64, 64 - 52 }
+#[cfg(feature="simd_support")]
+uniform_float_impl! { f64x8, u64x8, f64, u64, 64 - 52 }
+
+
+
+/// The back-end implementing [`UniformSampler`] for `Duration`.
+///
+/// Unless you are implementing [`UniformSampler`] for your own types, this type
+/// should not be used directly, use [`Uniform`] instead.
+///
+/// [`UniformSampler`]: trait.UniformSampler.html
+/// [`Uniform`]: struct.Uniform.html
+#[cfg(any(feature = "std", rust_1_25))]
+#[derive(Clone, Copy, Debug)]
+pub struct UniformDuration {
+    mode: UniformDurationMode,
+    offset: u32,
+}
+
+#[cfg(any(feature = "std", rust_1_25))]
+#[derive(Debug, Copy, Clone)]
+enum UniformDurationMode {
+    Small {
+        secs: u64,
+        nanos: Uniform<u32>,
+    },
+    Medium {
+        nanos: Uniform<u64>,
+    },
+    Large {
+        max_secs: u64,
+        max_nanos: u32,
+        secs: Uniform<u64>,
+    }
+}
+
+#[cfg(any(feature = "std", rust_1_25))]
+impl SampleUniform for Duration {
+    type Sampler = UniformDuration;
+}
+
+#[cfg(any(feature = "std", rust_1_25))]
+impl UniformSampler for UniformDuration {
+    type X = Duration;
+
+    #[inline]
+    fn new<B1, B2>(low_b: B1, high_b: B2) -> Self
+        where B1: SampleBorrow<Self::X> + Sized,
+              B2: SampleBorrow<Self::X> + Sized
+    {
+        let low = *low_b.borrow();
+        let high = *high_b.borrow();
+        assert!(low < high, "Uniform::new called with `low >= high`");
+        UniformDuration::new_inclusive(low, high - Duration::new(0, 1))
+    }
+
+    #[inline]
+    fn new_inclusive<B1, B2>(low_b: B1, high_b: B2) -> Self
+        where B1: SampleBorrow<Self::X> + Sized,
+              B2: SampleBorrow<Self::X> + Sized
+    {
+        let low = *low_b.borrow();
+        let high = *high_b.borrow();
+        assert!(low <= high, "Uniform::new_inclusive called with `low > high`");
+
+        let low_s = low.as_secs();
+        let low_n = low.subsec_nanos();
+        let mut high_s = high.as_secs();
+        let mut high_n = high.subsec_nanos();
+
+        if high_n < low_n {
+            high_s = high_s - 1;
+            high_n = high_n + 1_000_000_000;
+        }
+
+        let mode = if low_s == high_s {
+            UniformDurationMode::Small {
+                secs: low_s,
+                nanos: Uniform::new_inclusive(low_n, high_n),
+            }
+        } else {
+            let max = high_s
+                .checked_mul(1_000_000_000)
+                .and_then(|n| n.checked_add(high_n as u64));
+
+            if let Some(higher_bound) = max {
+                let lower_bound = low_s * 1_000_000_000 + low_n as u64;
+                UniformDurationMode::Medium {
+                    nanos: Uniform::new_inclusive(lower_bound, higher_bound),
+                }
+            } else {
+                // An offset is applied to simplify generation of nanoseconds
+                let max_nanos = high_n - low_n;
+                UniformDurationMode::Large {
+                    max_secs: high_s,
+                    max_nanos,
+                    secs: Uniform::new_inclusive(low_s, high_s),
+                }
+            }
+        };
+        UniformDuration {
+            mode,
+            offset: low_n,
+        }
+    }
+
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Duration {
+        match self.mode {
+            UniformDurationMode::Small { secs, nanos } => {
+                let n = nanos.sample(rng);
+                Duration::new(secs, n)
+            }
+            UniformDurationMode::Medium { nanos } => {
+                let nanos = nanos.sample(rng);
+                Duration::new(nanos / 1_000_000_000, (nanos % 1_000_000_000) as u32)
+            }
+            UniformDurationMode::Large { max_secs, max_nanos, secs } => {
+                // constant folding means this is at least as fast as `gen_range`
+                let nano_range = Uniform::new(0, 1_000_000_000);
+                loop {
+                    let s = secs.sample(rng);
+                    let n = nano_range.sample(rng);
+                    if !(s == max_secs && n > max_nanos) {
+                        let sum = n + self.offset;
+                        break Duration::new(s, sum);
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use Rng;
+    use rngs::mock::StepRng;
+    use distributions::uniform::Uniform;
+    use distributions::utils::FloatAsSIMD;
+    #[cfg(feature="simd_support")] use packed_simd::*;
+
+    #[should_panic]
+    #[test]
+    fn test_uniform_bad_limits_equal_int() {
+        Uniform::new(10, 10);
+    }
+
+    #[test]
+    fn test_uniform_good_limits_equal_int() {
+        let mut rng = ::test::rng(804);
+        let dist = Uniform::new_inclusive(10, 10);
+        for _ in 0..20 {
+            assert_eq!(rng.sample(dist), 10);
+        }
+    }
+
+    #[should_panic]
+    #[test]
+    fn test_uniform_bad_limits_flipped_int() {
+        Uniform::new(10, 5);
+    }
+
+    #[test]
+    fn test_integers() {
+        use core::{i8, i16, i32, i64, isize};
+        use core::{u8, u16, u32, u64, usize};
+        #[cfg(rust_1_26)]
+        use core::{i128, u128};
+
+        let mut rng = ::test::rng(251);
+        macro_rules! t {
+            ($ty:ident, $v:expr, $le:expr, $lt:expr) => {{
+                for &(low, high) in $v.iter() {
+                    let my_uniform = Uniform::new(low, high);
+                    for _ in 0..1000 {
+                        let v: $ty = rng.sample(my_uniform);
+                        assert!($le(low, v) && $lt(v, high));
+                    }
+
+                    let my_uniform = Uniform::new_inclusive(low, high);
+                    for _ in 0..1000 {
+                        let v: $ty = rng.sample(my_uniform);
+                        assert!($le(low, v) && $le(v, high));
+                    }
+
+                    let my_uniform = Uniform::new(&low, high);
+                    for _ in 0..1000 {
+                        let v: $ty = rng.sample(my_uniform);
+                        assert!($le(low, v) && $lt(v, high));
+                    }
+
+                    let my_uniform = Uniform::new_inclusive(&low, &high);
+                    for _ in 0..1000 {
+                        let v: $ty = rng.sample(my_uniform);
+                        assert!($le(low, v) && $le(v, high));
+                    }
+
+                    for _ in 0..1000 {
+                        let v: $ty = rng.gen_range(low, high);
+                        assert!($le(low, v) && $lt(v, high));
+                    }
+                }
+            }};
+
+            // scalar bulk
+            ($($ty:ident),*) => {{
+                $(t!(
+                    $ty,
+                    [(0, 10), (10, 127), ($ty::MIN, $ty::MAX)],
+                    |x, y| x <= y,
+                    |x, y| x < y
+                );)*
+            }};
+
+            // simd bulk
+            ($($ty:ident),* => $scalar:ident) => {{
+                $(t!(
+                    $ty,
+                    [
+                        ($ty::splat(0), $ty::splat(10)),
+                        ($ty::splat(10), $ty::splat(127)),
+                        ($ty::splat($scalar::MIN), $ty::splat($scalar::MAX)),
+                    ],
+                    |x: $ty, y| x.le(y).all(),
+                    |x: $ty, y| x.lt(y).all()
+                );)*
+            }};
+        }
+        t!(i8, i16, i32, i64, isize,
+           u8, u16, u32, u64, usize);
+        #[cfg(rust_1_26)]
+        t!(i128, u128);
+
+        #[cfg(all(feature = "simd_support", feature = "nightly"))]
+        {
+            t!(u8x2, u8x4, u8x8, u8x16, u8x32, u8x64 => u8);
+            t!(i8x2, i8x4, i8x8, i8x16, i8x32, i8x64 => i8);
+            t!(u16x2, u16x4, u16x8, u16x16, u16x32 => u16);
+            t!(i16x2, i16x4, i16x8, i16x16, i16x32 => i16);
+            t!(u32x2, u32x4, u32x8, u32x16 => u32);
+            t!(i32x2, i32x4, i32x8, i32x16 => i32);
+            t!(u64x2, u64x4, u64x8 => u64);
+            t!(i64x2, i64x4, i64x8 => i64);
+        }
+    }
+
+    #[test]
+    fn test_floats() {
+        let mut rng = ::test::rng(252);
+        let mut zero_rng = StepRng::new(0, 0);
+        let mut max_rng = StepRng::new(0xffff_ffff_ffff_ffff, 0);
+        macro_rules! t {
+            ($ty:ty, $f_scalar:ident, $bits_shifted:expr) => {{
+                let v: &[($f_scalar, $f_scalar)]=
+                    &[(0.0, 100.0),
+                      (-1e35, -1e25),
+                      (1e-35, 1e-25),
+                      (-1e35, 1e35),
+                      (<$f_scalar>::from_bits(0), <$f_scalar>::from_bits(3)),
+                      (-<$f_scalar>::from_bits(10), -<$f_scalar>::from_bits(1)),
+                      (-<$f_scalar>::from_bits(5), 0.0),
+                      (-<$f_scalar>::from_bits(7), -0.0),
+                      (10.0, ::core::$f_scalar::MAX),
+                      (-100.0, ::core::$f_scalar::MAX),
+                      (-::core::$f_scalar::MAX / 5.0, ::core::$f_scalar::MAX),
+                      (-::core::$f_scalar::MAX, ::core::$f_scalar::MAX / 5.0),
+                      (-::core::$f_scalar::MAX * 0.8, ::core::$f_scalar::MAX * 0.7),
+                      (-::core::$f_scalar::MAX, ::core::$f_scalar::MAX),
+                     ];
+                for &(low_scalar, high_scalar) in v.iter() {
+                    for lane in 0..<$ty>::lanes() {
+                        let low = <$ty>::splat(0.0 as $f_scalar).replace(lane, low_scalar);
+                        let high = <$ty>::splat(1.0 as $f_scalar).replace(lane, high_scalar);
+                        let my_uniform = Uniform::new(low, high);
+                        let my_incl_uniform = Uniform::new_inclusive(low, high);
+                        for _ in 0..100 {
+                            let v = rng.sample(my_uniform).extract(lane);
+                            assert!(low_scalar <= v && v < high_scalar);
+                            let v = rng.sample(my_incl_uniform).extract(lane);
+                            assert!(low_scalar <= v && v <= high_scalar);
+                            let v = rng.gen_range(low, high).extract(lane);
+                            assert!(low_scalar <= v && v < high_scalar);
+                        }
+
+                        assert_eq!(rng.sample(Uniform::new_inclusive(low, low)).extract(lane), low_scalar);
+
+                        assert_eq!(zero_rng.sample(my_uniform).extract(lane), low_scalar);
+                        assert_eq!(zero_rng.sample(my_incl_uniform).extract(lane), low_scalar);
+                        assert_eq!(zero_rng.gen_range(low, high).extract(lane), low_scalar);
+                        assert!(max_rng.sample(my_uniform).extract(lane) < high_scalar);
+                        assert!(max_rng.sample(my_incl_uniform).extract(lane) <= high_scalar);
+
+                        // Don't run this test for really tiny differences between high and low
+                        // since for those rounding might result in selecting high for a very
+                        // long time.
+                        if (high_scalar - low_scalar) > 0.0001 {
+                            let mut lowering_max_rng =
+                                StepRng::new(0xffff_ffff_ffff_ffff,
+                                             (-1i64 << $bits_shifted) as u64);
+                            assert!(lowering_max_rng.gen_range(low, high).extract(lane) < high_scalar);
+                        }
+                    }
+                }
+
+                assert_eq!(rng.sample(Uniform::new_inclusive(::core::$f_scalar::MAX,
+                                                             ::core::$f_scalar::MAX)),
+                           ::core::$f_scalar::MAX);
+                assert_eq!(rng.sample(Uniform::new_inclusive(-::core::$f_scalar::MAX,
+                                                             -::core::$f_scalar::MAX)),
+                           -::core::$f_scalar::MAX);
+            }}
+        }
+
+        t!(f32, f32, 32 - 23);
+        t!(f64, f64, 64 - 52);
+        #[cfg(feature="simd_support")]
+        {
+            t!(f32x2, f32, 32 - 23);
+            t!(f32x4, f32, 32 - 23);
+            t!(f32x8, f32, 32 - 23);
+            t!(f32x16, f32, 32 - 23);
+            t!(f64x2, f64, 64 - 52);
+            t!(f64x4, f64, 64 - 52);
+            t!(f64x8, f64, 64 - 52);
+        }
+    }
+
+    #[test]
+    #[cfg(all(feature="std",
+              not(target_arch = "wasm32"),
+              not(target_arch = "asmjs")))]
+    fn test_float_assertions() {
+        use std::panic::catch_unwind;
+        use super::SampleUniform;
+        fn range<T: SampleUniform>(low: T, high: T) {
+            let mut rng = ::test::rng(253);
+            rng.gen_range(low, high);
+        }
+
+        macro_rules! t {
+            ($ty:ident, $f_scalar:ident) => {{
+                let v: &[($f_scalar, $f_scalar)] =
+                    &[(::std::$f_scalar::NAN, 0.0),
+                      (1.0, ::std::$f_scalar::NAN),
+                      (::std::$f_scalar::NAN, ::std::$f_scalar::NAN),
+                      (1.0, 0.5),
+                      (::std::$f_scalar::MAX, -::std::$f_scalar::MAX),
+                      (::std::$f_scalar::INFINITY, ::std::$f_scalar::INFINITY),
+                      (::std::$f_scalar::NEG_INFINITY, ::std::$f_scalar::NEG_INFINITY),
+                      (::std::$f_scalar::NEG_INFINITY, 5.0),
+                      (5.0, ::std::$f_scalar::INFINITY),
+                      (::std::$f_scalar::NAN, ::std::$f_scalar::INFINITY),
+                      (::std::$f_scalar::NEG_INFINITY, ::std::$f_scalar::NAN),
+                      (::std::$f_scalar::NEG_INFINITY, ::std::$f_scalar::INFINITY),
+                     ];
+                for &(low_scalar, high_scalar) in v.iter() {
+                    for lane in 0..<$ty>::lanes() {
+                        let low = <$ty>::splat(0.0 as $f_scalar).replace(lane, low_scalar);
+                        let high = <$ty>::splat(1.0 as $f_scalar).replace(lane, high_scalar);
+                        assert!(catch_unwind(|| range(low, high)).is_err());
+                        assert!(catch_unwind(|| Uniform::new(low, high)).is_err());
+                        assert!(catch_unwind(|| Uniform::new_inclusive(low, high)).is_err());
+                        assert!(catch_unwind(|| range(low, low)).is_err());
+                        assert!(catch_unwind(|| Uniform::new(low, low)).is_err());
+                    }
+                }
+            }}
+        }
+
+        t!(f32, f32);
+        t!(f64, f64);
+        #[cfg(feature="simd_support")]
+        {
+            t!(f32x2, f32);
+            t!(f32x4, f32);
+            t!(f32x8, f32);
+            t!(f32x16, f32);
+            t!(f64x2, f64);
+            t!(f64x4, f64);
+            t!(f64x8, f64);
+        }
+    }
+
+
+    #[test]
+    #[cfg(any(feature = "std", rust_1_25))]
+    fn test_durations() {
+        #[cfg(feature = "std")]
+        use std::time::Duration;
+        #[cfg(all(not(feature = "std"), rust_1_25))]
+        use core::time::Duration;
+
+        let mut rng = ::test::rng(253);
+
+        let v = &[(Duration::new(10, 50000), Duration::new(100, 1234)),
+                  (Duration::new(0, 100), Duration::new(1, 50)),
+                  (Duration::new(0, 0), Duration::new(u64::max_value(), 999_999_999))];
+        for &(low, high) in v.iter() {
+            let my_uniform = Uniform::new(low, high);
+            for _ in 0..1000 {
+                let v = rng.sample(my_uniform);
+                assert!(low <= v && v < high);
+            }
+        }
+    }
+
+    #[test]
+    fn test_custom_uniform() {
+        use distributions::uniform::{UniformSampler, UniformFloat, SampleUniform, SampleBorrow};
+        #[derive(Clone, Copy, PartialEq, PartialOrd)]
+        struct MyF32 {
+            x: f32,
+        }
+        #[derive(Clone, Copy, Debug)]
+        struct UniformMyF32 {
+            inner: UniformFloat<f32>,
+        }
+        impl UniformSampler for UniformMyF32 {
+            type X = MyF32;
+            fn new<B1, B2>(low: B1, high: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                UniformMyF32 {
+                    inner: UniformFloat::<f32>::new(low.borrow().x, high.borrow().x),
+                }
+            }
+            fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
+                where B1: SampleBorrow<Self::X> + Sized,
+                      B2: SampleBorrow<Self::X> + Sized
+            {
+                UniformSampler::new(low, high)
+            }
+            fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
+                MyF32 { x: self.inner.sample(rng) }
+            }
+        }
+        impl SampleUniform for MyF32 {
+            type Sampler = UniformMyF32;
+        }
+
+        let (low, high) = (MyF32{ x: 17.0f32 }, MyF32{ x: 22.0f32 });
+        let uniform = Uniform::new(low, high);
+        let mut rng = ::test::rng(804);
+        for _ in 0..100 {
+            let x: MyF32 = rng.sample(uniform);
+            assert!(low <= x && x < high);
+        }
+    }
+
+    #[test]
+    fn test_uniform_from_std_range() {
+        let r = Uniform::from(2u32..7);
+        assert_eq!(r.inner.low, 2);
+        assert_eq!(r.inner.range, 5);
+        let r = Uniform::from(2.0f64..7.0);
+        assert_eq!(r.inner.low, 2.0);
+        assert_eq!(r.inner.scale, 5.0);
+    }
+
+    #[cfg(rust_1_27)]
+    #[test]
+    fn test_uniform_from_std_range_inclusive() {
+        let r = Uniform::from(2u32..=6);
+        assert_eq!(r.inner.low, 2);
+        assert_eq!(r.inner.range, 5);
+        let r = Uniform::from(2.0f64..=7.0);
+        assert_eq!(r.inner.low, 2.0);
+        assert!(r.inner.scale > 5.0);
+        assert!(r.inner.scale < 5.0 + 1e-14);
+    }
+}
diff --git a/rand/src/distributions/unit_circle.rs b/rand/src/distributions/unit_circle.rs
new file mode 100644
index 0000000..abb36dc
--- /dev/null
+++ b/rand/src/distributions/unit_circle.rs
@@ -0,0 +1,102 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use Rng;
+use distributions::{Distribution, Uniform};
+
+/// Samples uniformly from the edge of the unit circle in two dimensions.
+///
+/// Implemented via a method by von Neumann[^1].
+///
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{UnitCircle, Distribution};
+///
+/// let circle = UnitCircle::new();
+/// let v = circle.sample(&mut rand::thread_rng());
+/// println!("{:?} is from the unit circle.", v)
+/// ```
+///
+/// [^1]: von Neumann, J. (1951) [*Various Techniques Used in Connection with
+///       Random Digits.*](https://mcnp.lanl.gov/pdf_files/nbs_vonneumann.pdf)
+///       NBS Appl. Math. Ser., No. 12. Washington, DC: U.S. Government Printing
+///       Office, pp. 36-38.
+#[derive(Clone, Copy, Debug)]
+pub struct UnitCircle {
+    uniform: Uniform<f64>,
+}
+
+impl UnitCircle {
+    /// Construct a new `UnitCircle` distribution.
+    #[inline]
+    pub fn new() -> UnitCircle {
+        UnitCircle { uniform: Uniform::new(-1., 1.) }
+    }
+}
+
+impl Distribution<[f64; 2]> for UnitCircle {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [f64; 2] {
+        let mut x1;
+        let mut x2;
+        let mut sum;
+        loop {
+            x1 = self.uniform.sample(rng);
+            x2 = self.uniform.sample(rng);
+            sum = x1*x1 + x2*x2;
+            if sum < 1. {
+                break;
+            }
+        }
+        let diff = x1*x1 - x2*x2;
+        [diff / sum, 2.*x1*x2 / sum]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use distributions::Distribution;
+    use super::UnitCircle;
+
+    /// Assert that two numbers are almost equal to each other.
+    ///
+    /// On panic, this macro will print the values of the expressions with their
+    /// debug representations.
+    macro_rules! assert_almost_eq {
+        ($a:expr, $b:expr, $prec:expr) => (
+            let diff = ($a - $b).abs();
+            if diff > $prec {
+                panic!(format!(
+                    "assertion failed: `abs(left - right) = {:.1e} < {:e}`, \
+                     (left: `{}`, right: `{}`)",
+                    diff, $prec, $a, $b));
+            }
+        );
+    }
+
+    #[test]
+    fn norm() {
+        let mut rng = ::test::rng(1);
+        let dist = UnitCircle::new();
+        for _ in 0..1000 {
+            let x = dist.sample(&mut rng);
+            assert_almost_eq!(x[0]*x[0] + x[1]*x[1], 1., 1e-15);
+        }
+    }
+
+    #[test]
+    fn value_stability() {
+        let mut rng = ::test::rng(2);
+        let dist = UnitCircle::new();
+        assert_eq!(dist.sample(&mut rng), [-0.8032118336637037, 0.5956935036263119]);
+        assert_eq!(dist.sample(&mut rng), [-0.4742919588505423, -0.880367615130018]);
+        assert_eq!(dist.sample(&mut rng), [0.9297328981467168, 0.368234623716601]);
+    }
+}
diff --git a/rand/src/distributions/unit_sphere.rs b/rand/src/distributions/unit_sphere.rs
new file mode 100644
index 0000000..61cbda5
--- /dev/null
+++ b/rand/src/distributions/unit_sphere.rs
@@ -0,0 +1,100 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use Rng;
+use distributions::{Distribution, Uniform};
+
+/// Samples uniformly from the surface of the unit sphere in three dimensions.
+///
+/// Implemented via a method by Marsaglia[^1].
+///
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{UnitSphereSurface, Distribution};
+///
+/// let sphere = UnitSphereSurface::new();
+/// let v = sphere.sample(&mut rand::thread_rng());
+/// println!("{:?} is from the unit sphere surface.", v)
+/// ```
+///
+/// [^1]: Marsaglia, George (1972). [*Choosing a Point from the Surface of a
+///       Sphere.*](https://doi.org/10.1214/aoms/1177692644)
+///       Ann. Math. Statist. 43, no. 2, 645--646.
+#[derive(Clone, Copy, Debug)]
+pub struct UnitSphereSurface {
+    uniform: Uniform<f64>,
+}
+
+impl UnitSphereSurface {
+    /// Construct a new `UnitSphereSurface` distribution.
+    #[inline]
+    pub fn new() -> UnitSphereSurface {
+        UnitSphereSurface { uniform: Uniform::new(-1., 1.) }
+    }
+}
+
+impl Distribution<[f64; 3]> for UnitSphereSurface {
+    #[inline]
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> [f64; 3] {
+        loop {
+            let (x1, x2) = (self.uniform.sample(rng), self.uniform.sample(rng));
+            let sum = x1*x1 + x2*x2;
+            if sum >= 1. {
+                continue;
+            }
+            let factor = 2. * (1.0_f64 - sum).sqrt();
+            return [x1 * factor, x2 * factor, 1. - 2.*sum];
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use distributions::Distribution;
+    use super::UnitSphereSurface;
+
+    /// Assert that two numbers are almost equal to each other.
+    ///
+    /// On panic, this macro will print the values of the expressions with their
+    /// debug representations.
+    macro_rules! assert_almost_eq {
+        ($a:expr, $b:expr, $prec:expr) => (
+            let diff = ($a - $b).abs();
+            if diff > $prec {
+                panic!(format!(
+                    "assertion failed: `abs(left - right) = {:.1e} < {:e}`, \
+                     (left: `{}`, right: `{}`)",
+                    diff, $prec, $a, $b));
+            }
+        );
+    }
+
+    #[test]
+    fn norm() {
+        let mut rng = ::test::rng(1);
+        let dist = UnitSphereSurface::new();
+        for _ in 0..1000 {
+            let x = dist.sample(&mut rng);
+            assert_almost_eq!(x[0]*x[0] + x[1]*x[1] + x[2]*x[2], 1., 1e-15);
+        }
+    }
+
+    #[test]
+    fn value_stability() {
+        let mut rng = ::test::rng(2);
+        let dist = UnitSphereSurface::new();
+        assert_eq!(dist.sample(&mut rng),
+                   [-0.24950027180862533, -0.7552572587896719, 0.6060825747478084]);
+        assert_eq!(dist.sample(&mut rng),
+                   [0.47604534507233487, -0.797200864987207, -0.3712837328763685]);
+        assert_eq!(dist.sample(&mut rng),
+                   [0.9795722330927367, 0.18692349236651176, 0.07414747571708524]);
+    }
+}
diff --git a/rand/src/distributions/utils.rs b/rand/src/distributions/utils.rs
new file mode 100644
index 0000000..a2112fd
--- /dev/null
+++ b/rand/src/distributions/utils.rs
@@ -0,0 +1,504 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Math helper functions
+
+#[cfg(feature="simd_support")]
+use packed_simd::*;
+#[cfg(feature="std")]
+use distributions::ziggurat_tables;
+#[cfg(feature="std")]
+use Rng;
+
+
+pub trait WideningMultiply<RHS = Self> {
+    type Output;
+
+    fn wmul(self, x: RHS) -> Self::Output;
+}
+
+macro_rules! wmul_impl {
+    ($ty:ty, $wide:ty, $shift:expr) => {
+        impl WideningMultiply for $ty {
+            type Output = ($ty, $ty);
+
+            #[inline(always)]
+            fn wmul(self, x: $ty) -> Self::Output {
+                let tmp = (self as $wide) * (x as $wide);
+                ((tmp >> $shift) as $ty, tmp as $ty)
+            }
+        }
+    };
+
+    // simd bulk implementation
+    ($(($ty:ident, $wide:ident),)+, $shift:expr) => {
+        $(
+            impl WideningMultiply for $ty {
+                type Output = ($ty, $ty);
+
+                #[inline(always)]
+                fn wmul(self, x: $ty) -> Self::Output {
+                    // For supported vectors, this should compile to a couple
+                    // supported multiply & swizzle instructions (no actual
+                    // casting).
+                    // TODO: optimize
+                    let y: $wide = self.cast();
+                    let x: $wide = x.cast();
+                    let tmp = y * x;
+                    let hi: $ty = (tmp >> $shift).cast();
+                    let lo: $ty = tmp.cast();
+                    (hi, lo)
+                }
+            }
+        )+
+    };
+}
+wmul_impl! { u8, u16, 8 }
+wmul_impl! { u16, u32, 16 }
+wmul_impl! { u32, u64, 32 }
+#[cfg(rust_1_26)]
+wmul_impl! { u64, u128, 64 }
+
+// This code is a translation of the __mulddi3 function in LLVM's
+// compiler-rt. It is an optimised variant of the common method
+// `(a + b) * (c + d) = ac + ad + bc + bd`.
+//
+// For some reason LLVM can optimise the C version very well, but
+// keeps shuffling registers in this Rust translation.
+macro_rules! wmul_impl_large {
+    ($ty:ty, $half:expr) => {
+        impl WideningMultiply for $ty {
+            type Output = ($ty, $ty);
+
+            #[inline(always)]
+            fn wmul(self, b: $ty) -> Self::Output {
+                const LOWER_MASK: $ty = !0 >> $half;
+                let mut low = (self & LOWER_MASK).wrapping_mul(b & LOWER_MASK);
+                let mut t = low >> $half;
+                low &= LOWER_MASK;
+                t += (self >> $half).wrapping_mul(b & LOWER_MASK);
+                low += (t & LOWER_MASK) << $half;
+                let mut high = t >> $half;
+                t = low >> $half;
+                low &= LOWER_MASK;
+                t += (b >> $half).wrapping_mul(self & LOWER_MASK);
+                low += (t & LOWER_MASK) << $half;
+                high += t >> $half;
+                high += (self >> $half).wrapping_mul(b >> $half);
+
+                (high, low)
+            }
+        }
+    };
+
+    // simd bulk implementation
+    (($($ty:ty,)+) $scalar:ty, $half:expr) => {
+        $(
+            impl WideningMultiply for $ty {
+                type Output = ($ty, $ty);
+
+                #[inline(always)]
+                fn wmul(self, b: $ty) -> Self::Output {
+                    // needs wrapping multiplication
+                    const LOWER_MASK: $scalar = !0 >> $half;
+                    let mut low = (self & LOWER_MASK) * (b & LOWER_MASK);
+                    let mut t = low >> $half;
+                    low &= LOWER_MASK;
+                    t += (self >> $half) * (b & LOWER_MASK);
+                    low += (t & LOWER_MASK) << $half;
+                    let mut high = t >> $half;
+                    t = low >> $half;
+                    low &= LOWER_MASK;
+                    t += (b >> $half) * (self & LOWER_MASK);
+                    low += (t & LOWER_MASK) << $half;
+                    high += t >> $half;
+                    high += (self >> $half) * (b >> $half);
+
+                    (high, low)
+                }
+            }
+        )+
+    };
+}
+#[cfg(not(rust_1_26))]
+wmul_impl_large! { u64, 32 }
+#[cfg(rust_1_26)]
+wmul_impl_large! { u128, 64 }
+
+macro_rules! wmul_impl_usize {
+    ($ty:ty) => {
+        impl WideningMultiply for usize {
+            type Output = (usize, usize);
+
+            #[inline(always)]
+            fn wmul(self, x: usize) -> Self::Output {
+                let (high, low) = (self as $ty).wmul(x as $ty);
+                (high as usize, low as usize)
+            }
+        }
+    }
+}
+#[cfg(target_pointer_width = "32")]
+wmul_impl_usize! { u32 }
+#[cfg(target_pointer_width = "64")]
+wmul_impl_usize! { u64 }
+
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+mod simd_wmul {
+    #[cfg(target_arch = "x86")]
+    use core::arch::x86::*;
+    #[cfg(target_arch = "x86_64")]
+    use core::arch::x86_64::*;
+    use super::*;
+
+    wmul_impl! {
+        (u8x2, u16x2),
+        (u8x4, u16x4),
+        (u8x8, u16x8),
+        (u8x16, u16x16),
+        (u8x32, u16x32),,
+        8
+    }
+
+    wmul_impl! { (u16x2, u32x2),, 16 }
+    #[cfg(not(target_feature = "sse2"))]
+    wmul_impl! { (u16x4, u32x4),, 16 }
+    #[cfg(not(target_feature = "sse4.2"))]
+    wmul_impl! { (u16x8, u32x8),, 16 }
+    #[cfg(not(target_feature = "avx2"))]
+    wmul_impl! { (u16x16, u32x16),, 16 }
+
+    // 16-bit lane widths allow use of the x86 `mulhi` instructions, which
+    // means `wmul` can be implemented with only two instructions.
+    #[allow(unused_macros)]
+    macro_rules! wmul_impl_16 {
+        ($ty:ident, $intrinsic:ident, $mulhi:ident, $mullo:ident) => {
+            impl WideningMultiply for $ty {
+                type Output = ($ty, $ty);
+
+                #[inline(always)]
+                fn wmul(self, x: $ty) -> Self::Output {
+                    let b = $intrinsic::from_bits(x);
+                    let a = $intrinsic::from_bits(self);
+                    let hi = $ty::from_bits(unsafe { $mulhi(a, b) });
+                    let lo = $ty::from_bits(unsafe { $mullo(a, b) });
+                    (hi, lo)
+                }
+            }
+        };
+    }
+
+    #[cfg(target_feature = "sse2")]
+    wmul_impl_16! { u16x4, __m64, _mm_mulhi_pu16, _mm_mullo_pi16 }
+    #[cfg(target_feature = "sse4.2")]
+    wmul_impl_16! { u16x8, __m128i, _mm_mulhi_epu16, _mm_mullo_epi16 }
+    #[cfg(target_feature = "avx2")]
+    wmul_impl_16! { u16x16, __m256i, _mm256_mulhi_epu16, _mm256_mullo_epi16 }
+    // FIXME: there are no `__m512i` types in stdsimd yet, so `wmul::<u16x32>`
+    // cannot use the same implementation.
+
+    wmul_impl! {
+        (u32x2, u64x2),
+        (u32x4, u64x4),
+        (u32x8, u64x8),,
+        32
+    }
+
+    // TODO: optimize, this seems to seriously slow things down
+    wmul_impl_large! { (u8x64,) u8, 4 }
+    wmul_impl_large! { (u16x32,) u16, 8 }
+    wmul_impl_large! { (u32x16,) u32, 16 }
+    wmul_impl_large! { (u64x2, u64x4, u64x8,) u64, 32 }
+}
+#[cfg(all(feature = "simd_support", feature = "nightly"))]
+pub use self::simd_wmul::*;
+
+
+/// Helper trait when dealing with scalar and SIMD floating point types.
+pub(crate) trait FloatSIMDUtils {
+    // `PartialOrd` for vectors compares lexicographically. We want to compare all
+    // the individual SIMD lanes instead, and get the combined result over all
+    // lanes. This is possible using something like `a.lt(b).all()`, but we
+    // implement it as a trait so we can write the same code for `f32` and `f64`.
+    // Only the comparison functions we need are implemented.
+    fn all_lt(self, other: Self) -> bool;
+    fn all_le(self, other: Self) -> bool;
+    fn all_finite(self) -> bool;
+
+    type Mask;
+    fn finite_mask(self) -> Self::Mask;
+    fn gt_mask(self, other: Self) -> Self::Mask;
+    fn ge_mask(self, other: Self) -> Self::Mask;
+
+    // Decrease all lanes where the mask is `true` to the next lower value
+    // representable by the floating-point type. At least one of the lanes
+    // must be set.
+    fn decrease_masked(self, mask: Self::Mask) -> Self;
+
+    // Convert from int value. Conversion is done while retaining the numerical
+    // value, not by retaining the binary representation.
+    type UInt;
+    fn cast_from_int(i: Self::UInt) -> Self;
+}
+
+/// Implement functions available in std builds but missing from core primitives
+#[cfg(not(std))]
+pub(crate) trait Float : Sized {
+    type Bits;
+
+    fn is_nan(self) -> bool;
+    fn is_infinite(self) -> bool;
+    fn is_finite(self) -> bool;
+    fn to_bits(self) -> Self::Bits;
+    fn from_bits(v: Self::Bits) -> Self;
+}
+
+/// Implement functions on f32/f64 to give them APIs similar to SIMD types
+pub(crate) trait FloatAsSIMD : Sized {
+    #[inline(always)]
+    fn lanes() -> usize { 1 }
+    #[inline(always)]
+    fn splat(scalar: Self) -> Self { scalar }
+    #[inline(always)]
+    fn extract(self, index: usize) -> Self { debug_assert_eq!(index, 0); self }
+    #[inline(always)]
+    fn replace(self, index: usize, new_value: Self) -> Self { debug_assert_eq!(index, 0); new_value }
+}
+
+pub(crate) trait BoolAsSIMD : Sized {
+    fn any(self) -> bool;
+    fn all(self) -> bool;
+    fn none(self) -> bool;
+}
+
+impl BoolAsSIMD for bool {
+    #[inline(always)]
+    fn any(self) -> bool { self }
+    #[inline(always)]
+    fn all(self) -> bool { self }
+    #[inline(always)]
+    fn none(self) -> bool { !self }
+}
+
+macro_rules! scalar_float_impl {
+    ($ty:ident, $uty:ident) => {
+        #[cfg(not(std))]
+        impl Float for $ty {
+            type Bits = $uty;
+
+            #[inline]
+            fn is_nan(self) -> bool {
+                self != self
+            }
+
+            #[inline]
+            fn is_infinite(self) -> bool {
+                self == ::core::$ty::INFINITY || self == ::core::$ty::NEG_INFINITY
+            }
+
+            #[inline]
+            fn is_finite(self) -> bool {
+                !(self.is_nan() || self.is_infinite())
+            }
+
+            #[inline]
+            fn to_bits(self) -> Self::Bits {
+                unsafe { ::core::mem::transmute(self) }
+            }
+
+            #[inline]
+            fn from_bits(v: Self::Bits) -> Self {
+                // It turns out the safety issues with sNaN were overblown! Hooray!
+                unsafe { ::core::mem::transmute(v) }
+            }
+        }
+
+        impl FloatSIMDUtils for $ty {
+            type Mask = bool;
+            #[inline(always)]
+            fn all_lt(self, other: Self) -> bool { self < other }
+            #[inline(always)]
+            fn all_le(self, other: Self) -> bool { self <= other }
+            #[inline(always)]
+            fn all_finite(self) -> bool { self.is_finite() }
+            #[inline(always)]
+            fn finite_mask(self) -> Self::Mask { self.is_finite() }
+            #[inline(always)]
+            fn gt_mask(self, other: Self) -> Self::Mask { self > other }
+            #[inline(always)]
+            fn ge_mask(self, other: Self) -> Self::Mask { self >= other }
+            #[inline(always)]
+            fn decrease_masked(self, mask: Self::Mask) -> Self {
+                debug_assert!(mask, "At least one lane must be set");
+                <$ty>::from_bits(self.to_bits() - 1)
+            }
+            type UInt = $uty;
+            fn cast_from_int(i: Self::UInt) -> Self { i as $ty }
+        }
+
+        impl FloatAsSIMD for $ty {}
+    }
+}
+
+scalar_float_impl!(f32, u32);
+scalar_float_impl!(f64, u64);
+
+
+#[cfg(feature="simd_support")]
+macro_rules! simd_impl {
+    ($ty:ident, $f_scalar:ident, $mty:ident, $uty:ident) => {
+        impl FloatSIMDUtils for $ty {
+            type Mask = $mty;
+            #[inline(always)]
+            fn all_lt(self, other: Self) -> bool { self.lt(other).all() }
+            #[inline(always)]
+            fn all_le(self, other: Self) -> bool { self.le(other).all() }
+            #[inline(always)]
+            fn all_finite(self) -> bool { self.finite_mask().all() }
+            #[inline(always)]
+            fn finite_mask(self) -> Self::Mask {
+                // This can possibly be done faster by checking bit patterns
+                let neg_inf = $ty::splat(::core::$f_scalar::NEG_INFINITY);
+                let pos_inf = $ty::splat(::core::$f_scalar::INFINITY);
+                self.gt(neg_inf) & self.lt(pos_inf)
+            }
+            #[inline(always)]
+            fn gt_mask(self, other: Self) -> Self::Mask { self.gt(other) }
+            #[inline(always)]
+            fn ge_mask(self, other: Self) -> Self::Mask { self.ge(other) }
+            #[inline(always)]
+            fn decrease_masked(self, mask: Self::Mask) -> Self {
+                // Casting a mask into ints will produce all bits set for
+                // true, and 0 for false. Adding that to the binary
+                // representation of a float means subtracting one from
+                // the binary representation, resulting in the next lower
+                // value representable by $ty. This works even when the
+                // current value is infinity.
+                debug_assert!(mask.any(), "At least one lane must be set");
+                <$ty>::from_bits(<$uty>::from_bits(self) + <$uty>::from_bits(mask))
+            }
+            type UInt = $uty;
+            fn cast_from_int(i: Self::UInt) -> Self { i.cast() }
+        }
+    }
+}
+
+#[cfg(feature="simd_support")] simd_impl! { f32x2, f32, m32x2, u32x2 }
+#[cfg(feature="simd_support")] simd_impl! { f32x4, f32, m32x4, u32x4 }
+#[cfg(feature="simd_support")] simd_impl! { f32x8, f32, m32x8, u32x8 }
+#[cfg(feature="simd_support")] simd_impl! { f32x16, f32, m32x16, u32x16 }
+#[cfg(feature="simd_support")] simd_impl! { f64x2, f64, m64x2, u64x2 }
+#[cfg(feature="simd_support")] simd_impl! { f64x4, f64, m64x4, u64x4 }
+#[cfg(feature="simd_support")] simd_impl! { f64x8, f64, m64x8, u64x8 }
+
+/// Calculates ln(gamma(x)) (natural logarithm of the gamma
+/// function) using the Lanczos approximation.
+///
+/// The approximation expresses the gamma function as:
+/// `gamma(z+1) = sqrt(2*pi)*(z+g+0.5)^(z+0.5)*exp(-z-g-0.5)*Ag(z)`
+/// `g` is an arbitrary constant; we use the approximation with `g=5`.
+///
+/// Noting that `gamma(z+1) = z*gamma(z)` and applying `ln` to both sides:
+/// `ln(gamma(z)) = (z+0.5)*ln(z+g+0.5)-(z+g+0.5) + ln(sqrt(2*pi)*Ag(z)/z)`
+///
+/// `Ag(z)` is an infinite series with coefficients that can be calculated
+/// ahead of time - we use just the first 6 terms, which is good enough
+/// for most purposes.
+#[cfg(feature="std")]
+pub fn log_gamma(x: f64) -> f64 {
+    // precalculated 6 coefficients for the first 6 terms of the series
+    let coefficients: [f64; 6] = [
+        76.18009172947146,
+        -86.50532032941677,
+        24.01409824083091,
+        -1.231739572450155,
+        0.1208650973866179e-2,
+        -0.5395239384953e-5,
+    ];
+
+    // (x+0.5)*ln(x+g+0.5)-(x+g+0.5)
+    let tmp = x + 5.5;
+    let log = (x + 0.5) * tmp.ln() - tmp;
+
+    // the first few terms of the series for Ag(x)
+    let mut a = 1.000000000190015;
+    let mut denom = x;
+    for coeff in &coefficients {
+        denom += 1.0;
+        a += coeff / denom;
+    }
+
+    // get everything together
+    // a is Ag(x)
+    // 2.5066... is sqrt(2pi)
+    log + (2.5066282746310005 * a / x).ln()
+}
+
+/// Sample a random number using the Ziggurat method (specifically the
+/// ZIGNOR variant from Doornik 2005). Most of the arguments are
+/// directly from the paper:
+///
+/// * `rng`: source of randomness
+/// * `symmetric`: whether this is a symmetric distribution, or one-sided with P(x < 0) = 0.
+/// * `X`: the $x_i$ abscissae.
+/// * `F`: precomputed values of the PDF at the $x_i$, (i.e. $f(x_i)$)
+/// * `F_DIFF`: precomputed values of $f(x_i) - f(x_{i+1})$
+/// * `pdf`: the probability density function
+/// * `zero_case`: manual sampling from the tail when we chose the
+///    bottom box (i.e. i == 0)
+
+// the perf improvement (25-50%) is definitely worth the extra code
+// size from force-inlining.
+#[cfg(feature="std")]
+#[inline(always)]
+pub fn ziggurat<R: Rng + ?Sized, P, Z>(
+            rng: &mut R,
+            symmetric: bool,
+            x_tab: ziggurat_tables::ZigTable,
+            f_tab: ziggurat_tables::ZigTable,
+            mut pdf: P,
+            mut zero_case: Z)
+            -> f64 where P: FnMut(f64) -> f64, Z: FnMut(&mut R, f64) -> f64 {
+    use distributions::float::IntoFloat;
+    loop {
+        // As an optimisation we re-implement the conversion to a f64.
+        // From the remaining 12 most significant bits we use 8 to construct `i`.
+        // This saves us generating a whole extra random number, while the added
+        // precision of using 64 bits for f64 does not buy us much.
+        let bits = rng.next_u64();
+        let i = bits as usize & 0xff;
+
+        let u = if symmetric {
+            // Convert to a value in the range [2,4) and substract to get [-1,1)
+            // We can't convert to an open range directly, that would require
+            // substracting `3.0 - EPSILON`, which is not representable.
+            // It is possible with an extra step, but an open range does not
+            // seem neccesary for the ziggurat algorithm anyway.
+            (bits >> 12).into_float_with_exponent(1) - 3.0
+        } else {
+            // Convert to a value in the range [1,2) and substract to get (0,1)
+            (bits >> 12).into_float_with_exponent(0)
+            - (1.0 - ::core::f64::EPSILON / 2.0)
+        };
+        let x = u * x_tab[i];
+
+        let test_x = if symmetric { x.abs() } else {x};
+
+        // algebraically equivalent to |u| < x_tab[i+1]/x_tab[i] (or u < x_tab[i+1]/x_tab[i])
+        if test_x < x_tab[i + 1] {
+            return x;
+        }
+        if i == 0 {
+            return zero_case(rng, u);
+        }
+        // algebraically equivalent to f1 + DRanU()*(f0 - f1) < 1
+        if f_tab[i + 1] + (f_tab[i] - f_tab[i + 1]) * rng.gen::<f64>() < pdf(x) {
+            return x;
+        }
+    }
+}
diff --git a/rand/src/distributions/weibull.rs b/rand/src/distributions/weibull.rs
new file mode 100644
index 0000000..5fbe10a
--- /dev/null
+++ b/rand/src/distributions/weibull.rs
@@ -0,0 +1,71 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Weibull distribution.
+
+use Rng;
+use distributions::{Distribution, OpenClosed01};
+
+/// Samples floating-point numbers according to the Weibull distribution
+///
+/// # Example
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::Weibull;
+///
+/// let val: f64 = SmallRng::from_entropy().sample(Weibull::new(1., 10.));
+/// println!("{}", val);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Weibull {
+    inv_shape: f64,
+    scale: f64,
+}
+
+impl Weibull {
+    /// Construct a new `Weibull` distribution with given `scale` and `shape`.
+    ///
+    /// # Panics
+    ///
+    /// `scale` and `shape` have to be non-zero and positive.
+    pub fn new(scale: f64, shape: f64) -> Weibull {
+        assert!((scale > 0.) & (shape > 0.));
+        Weibull { inv_shape: 1./shape, scale }
+    }
+}
+
+impl Distribution<f64> for Weibull {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        let x: f64 = rng.sample(OpenClosed01);
+        self.scale * (-x.ln()).powf(self.inv_shape)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use distributions::Distribution;
+    use super::Weibull;
+
+    #[test]
+    #[should_panic]
+    fn invalid() {
+        Weibull::new(0., 0.);
+    }
+
+    #[test]
+    fn sample() {
+        let scale = 1.0;
+        let shape = 2.0;
+        let d = Weibull::new(scale, shape);
+        let mut rng = ::test::rng(1);
+        for _ in 0..1000 {
+            let r = d.sample(&mut rng);
+            assert!(r >= 0.);
+        }
+    }
+}
diff --git a/rand/src/distributions/weighted.rs b/rand/src/distributions/weighted.rs
new file mode 100644
index 0000000..01c8fe6
--- /dev/null
+++ b/rand/src/distributions/weighted.rs
@@ -0,0 +1,232 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use Rng;
+use distributions::Distribution;
+use distributions::uniform::{UniformSampler, SampleUniform, SampleBorrow};
+use ::core::cmp::PartialOrd;
+use core::fmt;
+
+// Note that this whole module is only imported if feature="alloc" is enabled.
+#[cfg(not(feature="std"))] use alloc::vec::Vec;
+
+/// A distribution using weighted sampling to pick a discretely selected
+/// item.
+///
+/// Sampling a `WeightedIndex` distribution returns the index of a randomly
+/// selected element from the iterator used when the `WeightedIndex` was
+/// created. The chance of a given element being picked is proportional to the
+/// value of the element. The weights can use any type `X` for which an
+/// implementation of [`Uniform<X>`] exists.
+///
+/// # Performance
+///
+/// A `WeightedIndex<X>` contains a `Vec<X>` and a [`Uniform<X>`] and so its
+/// size is the sum of the size of those objects, possibly plus some alignment.
+///
+/// Creating a `WeightedIndex<X>` will allocate enough space to hold `N - 1`
+/// weights of type `X`, where `N` is the number of weights. However, since
+/// `Vec` doesn't guarantee a particular growth strategy, additional memory
+/// might be allocated but not used. Since the `WeightedIndex` object also
+/// contains, this might cause additional allocations, though for primitive
+/// types, ['Uniform<X>`] doesn't allocate any memory.
+///
+/// Time complexity of sampling from `WeightedIndex` is `O(log N)` where
+/// `N` is the number of weights.
+///
+/// Sampling from `WeightedIndex` will result in a single call to
+/// [`Uniform<X>::sample`], which typically will request a single value from
+/// the underlying [`RngCore`], though the exact number depends on the
+/// implementaiton of [`Uniform<X>::sample`].
+///
+/// # Example
+///
+/// ```
+/// use rand::prelude::*;
+/// use rand::distributions::WeightedIndex;
+///
+/// let choices = ['a', 'b', 'c'];
+/// let weights = [2,   1,   1];
+/// let dist = WeightedIndex::new(&weights).unwrap();
+/// let mut rng = thread_rng();
+/// for _ in 0..100 {
+///     // 50% chance to print 'a', 25% chance to print 'b', 25% chance to print 'c'
+///     println!("{}", choices[dist.sample(&mut rng)]);
+/// }
+///
+/// let items = [('a', 0), ('b', 3), ('c', 7)];
+/// let dist2 = WeightedIndex::new(items.iter().map(|item| item.1)).unwrap();
+/// for _ in 0..100 {
+///     // 0% chance to print 'a', 30% chance to print 'b', 70% chance to print 'c'
+///     println!("{}", items[dist2.sample(&mut rng)].0);
+/// }
+/// ```
+///
+/// [`Uniform<X>`]: struct.Uniform.html
+/// [`Uniform<X>::sample`]: struct.Uniform.html#method.sample
+/// [`RngCore`]: ../trait.RngCore.html
+#[derive(Debug, Clone)]
+pub struct WeightedIndex<X: SampleUniform + PartialOrd> {
+    cumulative_weights: Vec<X>,
+    weight_distribution: X::Sampler,
+}
+
+impl<X: SampleUniform + PartialOrd> WeightedIndex<X> {
+    /// Creates a new a `WeightedIndex` [`Distribution`] using the values
+    /// in `weights`. The weights can use any type `X` for which an
+    /// implementation of [`Uniform<X>`] exists.
+    ///
+    /// Returns an error if the iterator is empty, if any weight is `< 0`, or
+    /// if its total value is 0.
+    ///
+    /// [`Distribution`]: trait.Distribution.html
+    /// [`Uniform<X>`]: struct.Uniform.html
+    pub fn new<I>(weights: I) -> Result<WeightedIndex<X>, WeightedError>
+        where I: IntoIterator,
+              I::Item: SampleBorrow<X>,
+              X: for<'a> ::core::ops::AddAssign<&'a X> +
+                 Clone +
+                 Default {
+        let mut iter = weights.into_iter();
+        let mut total_weight: X = iter.next()
+                                      .ok_or(WeightedError::NoItem)?
+                                      .borrow()
+                                      .clone();
+
+        let zero = <X as Default>::default();
+        if total_weight < zero {
+            return Err(WeightedError::NegativeWeight);
+        }
+
+        let mut weights = Vec::<X>::with_capacity(iter.size_hint().0);
+        for w in iter {
+            if *w.borrow() < zero {
+                return Err(WeightedError::NegativeWeight);
+            }
+            weights.push(total_weight.clone());
+            total_weight += w.borrow();
+        }
+
+        if total_weight == zero {
+            return Err(WeightedError::AllWeightsZero);
+        }
+        let distr = X::Sampler::new(zero, total_weight);
+
+        Ok(WeightedIndex { cumulative_weights: weights, weight_distribution: distr })
+    }
+}
+
+impl<X> Distribution<usize> for WeightedIndex<X> where
+    X: SampleUniform + PartialOrd {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> usize {
+        use ::core::cmp::Ordering;
+        let chosen_weight = self.weight_distribution.sample(rng);
+        // Find the first item which has a weight *higher* than the chosen weight.
+        self.cumulative_weights.binary_search_by(
+            |w| if *w <= chosen_weight { Ordering::Less } else { Ordering::Greater }).unwrap_err()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_weightedindex() {
+        let mut r = ::test::rng(700);
+        const N_REPS: u32 = 5000;
+        let weights = [1u32, 2, 3, 0, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7];
+        let total_weight = weights.iter().sum::<u32>() as f32;
+
+        let verify = |result: [i32; 14]| {
+            for (i, count) in result.iter().enumerate() {
+                let exp = (weights[i] * N_REPS) as f32 / total_weight;
+                let mut err = (*count as f32 - exp).abs();
+                if err != 0.0 {
+                    err /= exp;
+                }
+                assert!(err <= 0.25);
+            }
+        };
+
+        // WeightedIndex from vec
+        let mut chosen = [0i32; 14];
+        let distr = WeightedIndex::new(weights.to_vec()).unwrap();
+        for _ in 0..N_REPS {
+            chosen[distr.sample(&mut r)] += 1;
+        }
+        verify(chosen);
+
+        // WeightedIndex from slice
+        chosen = [0i32; 14];
+        let distr = WeightedIndex::new(&weights[..]).unwrap();
+        for _ in 0..N_REPS {
+            chosen[distr.sample(&mut r)] += 1;
+        }
+        verify(chosen);
+
+        // WeightedIndex from iterator
+        chosen = [0i32; 14];
+        let distr = WeightedIndex::new(weights.iter()).unwrap();
+        for _ in 0..N_REPS {
+            chosen[distr.sample(&mut r)] += 1;
+        }
+        verify(chosen);
+
+        for _ in 0..5 {
+            assert_eq!(WeightedIndex::new(&[0, 1]).unwrap().sample(&mut r), 1);
+            assert_eq!(WeightedIndex::new(&[1, 0]).unwrap().sample(&mut r), 0);
+            assert_eq!(WeightedIndex::new(&[0, 0, 0, 0, 10, 0]).unwrap().sample(&mut r), 4);
+        }
+
+        assert_eq!(WeightedIndex::new(&[10][0..0]).unwrap_err(), WeightedError::NoItem);
+        assert_eq!(WeightedIndex::new(&[0]).unwrap_err(), WeightedError::AllWeightsZero);
+        assert_eq!(WeightedIndex::new(&[10, 20, -1, 30]).unwrap_err(), WeightedError::NegativeWeight);
+        assert_eq!(WeightedIndex::new(&[-10, 20, 1, 30]).unwrap_err(), WeightedError::NegativeWeight);
+        assert_eq!(WeightedIndex::new(&[-10]).unwrap_err(), WeightedError::NegativeWeight);
+    }
+}
+
+/// Error type returned from `WeightedIndex::new`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum WeightedError {
+    /// The provided iterator contained no items.
+    NoItem,
+
+    /// A weight lower than zero was used.
+    NegativeWeight,
+
+    /// All items in the provided iterator had a weight of zero.
+    AllWeightsZero,
+}
+
+impl WeightedError {
+    fn msg(&self) -> &str {
+        match *self {
+            WeightedError::NoItem => "No items found",
+            WeightedError::NegativeWeight => "Item has negative weight",
+            WeightedError::AllWeightsZero => "All items had weight zero",
+        }
+    }
+}
+
+#[cfg(feature="std")]
+impl ::std::error::Error for WeightedError {
+    fn description(&self) -> &str {
+        self.msg()
+    }
+    fn cause(&self) -> Option<&::std::error::Error> {
+        None
+    }
+}
+
+impl fmt::Display for WeightedError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.msg())
+    }
+}
diff --git a/rand/src/distributions/ziggurat_tables.rs b/rand/src/distributions/ziggurat_tables.rs
index b6de4bf..ca1ce30 100644
--- a/rand/src/distributions/ziggurat_tables.rs
+++ b/rand/src/distributions/ziggurat_tables.rs
@@ -1,10 +1,9 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
diff --git a/rand/src/lib.rs b/rand/src/lib.rs
index 7b22dd4..d364bd1 100644
--- a/rand/src/lib.rs
+++ b/rand/src/lib.rs
@@ -1,921 +1,673 @@
-// Copyright 2013-2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2017 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
 //! Utilities for random number generation
 //!
-//! The key functions are `random()` and `Rng::gen()`. These are polymorphic and
-//! so can be used to generate any type that implements `Rand`. Type inference
-//! means that often a simple call to `rand::random()` or `rng.gen()` will
-//! suffice, but sometimes an annotation is required, e.g.
-//! `rand::random::<f64>()`.
+//! Rand provides utilities to generate random numbers, to convert them to
+//! useful types and distributions, and some randomness-related algorithms.
 //!
-//! See the `distributions` submodule for sampling random numbers from
-//! distributions like normal and exponential.
+//! # Quick Start
+//! 
+//! To get you started quickly, the easiest and highest-level way to get
+//! a random value is to use [`random()`]; alternatively you can use
+//! [`thread_rng()`]. The [`Rng`] trait provides a useful API on all RNGs, while
+//! the [`distributions` module] and [`seq` module] provide further
+//! functionality on top of RNGs.
 //!
-//! # Usage
-//!
-//! This crate is [on crates.io](https://crates.io/crates/rand) and can be
-//! used by adding `rand` to the dependencies in your project's `Cargo.toml`.
-//!
-//! ```toml
-//! [dependencies]
-//! rand = "0.4"
-//! ```
-//!
-//! and this to your crate root:
-//!
-//! ```rust
-//! extern crate rand;
 //! ```
-//!
-//! # Thread-local RNG
-//!
-//! There is built-in support for a RNG associated with each thread stored
-//! in thread-local storage. This RNG can be accessed via `thread_rng`, or
-//! used implicitly via `random`. This RNG is normally randomly seeded
-//! from an operating-system source of randomness, e.g. `/dev/urandom` on
-//! Unix systems, and will automatically reseed itself from this source
-//! after generating 32 KiB of random data.
-//!
-//! # Cryptographic security
-//!
-//! An application that requires an entropy source for cryptographic purposes
-//! must use `OsRng`, which reads randomness from the source that the operating
-//! system provides (e.g. `/dev/urandom` on Unixes or `CryptGenRandom()` on
-//! Windows).
-//! The other random number generators provided by this module are not suitable
-//! for such purposes.
-//!
-//! *Note*: many Unix systems provide `/dev/random` as well as `/dev/urandom`.
-//! This module uses `/dev/urandom` for the following reasons:
-//!
-//! -   On Linux, `/dev/random` may block if entropy pool is empty;
-//!     `/dev/urandom` will not block.  This does not mean that `/dev/random`
-//!     provides better output than `/dev/urandom`; the kernel internally runs a
-//!     cryptographically secure pseudorandom number generator (CSPRNG) based on
-//!     entropy pool for random number generation, so the "quality" of
-//!     `/dev/random` is not better than `/dev/urandom` in most cases.  However,
-//!     this means that `/dev/urandom` can yield somewhat predictable randomness
-//!     if the entropy pool is very small, such as immediately after first
-//!     booting.  Linux 3.17 added the `getrandom(2)` system call which solves
-//!     the issue: it blocks if entropy pool is not initialized yet, but it does
-//!     not block once initialized.  `OsRng` tries to use `getrandom(2)` if
-//!     available, and use `/dev/urandom` fallback if not.  If an application
-//!     does not have `getrandom` and likely to be run soon after first booting,
-//!     or on a system with very few entropy sources, one should consider using
-//!     `/dev/random` via `ReadRng`.
-//! -   On some systems (e.g. FreeBSD, OpenBSD and Mac OS X) there is no
-//!     difference between the two sources. (Also note that, on some systems
-//!     e.g.  FreeBSD, both `/dev/random` and `/dev/urandom` may block once if
-//!     the CSPRNG has not seeded yet.)
-//!
-//! # Examples
-//!
-//! ```rust
-//! use rand::Rng;
-//!
-//! let mut rng = rand::thread_rng();
-//! if rng.gen() { // random bool
-//!     println!("i32: {}, u32: {}", rng.gen::<i32>(), rng.gen::<u32>())
+//! use rand::prelude::*;
+//! 
+//! if rand::random() { // generates a boolean
+//!     // Try printing a random unicode code point (probably a bad idea)!
+//!     println!("char: {}", rand::random::<char>());
 //! }
-//! ```
-//!
-//! ```rust
-//! let tuple = rand::random::<(f64, char)>();
-//! println!("{:?}", tuple)
-//! ```
-//!
-//! ## Monte Carlo estimation of π
-//!
-//! For this example, imagine we have a square with sides of length 2 and a unit
-//! circle, both centered at the origin. Since the area of a unit circle is π,
-//! we have:
-//!
-//! ```text
-//!     (area of unit circle) / (area of square) = π / 4
-//! ```
 //!
-//! So if we sample many points randomly from the square, roughly π / 4 of them
-//! should be inside the circle.
-//!
-//! We can use the above fact to estimate the value of π: pick many points in
-//! the square at random, calculate the fraction that fall within the circle,
-//! and multiply this fraction by 4.
-//!
-//! ```
-//! use rand::distributions::{IndependentSample, Range};
-//!
-//! fn main() {
-//!    let between = Range::new(-1f64, 1.);
-//!    let mut rng = rand::thread_rng();
-//!
-//!    let total = 1_000_000;
-//!    let mut in_circle = 0;
-//!
-//!    for _ in 0..total {
-//!        let a = between.ind_sample(&mut rng);
-//!        let b = between.ind_sample(&mut rng);
-//!        if a*a + b*b <= 1. {
-//!            in_circle += 1;
-//!        }
-//!    }
-//!
-//!    // prints something close to 3.14159...
-//!    println!("{}", 4. * (in_circle as f64) / (total as f64));
-//! }
-//! ```
-//!
-//! ## Monty Hall Problem
-//!
-//! This is a simulation of the [Monty Hall Problem][]:
-//!
-//! > Suppose you're on a game show, and you're given the choice of three doors:
-//! > Behind one door is a car; behind the others, goats. You pick a door, say
-//! > No. 1, and the host, who knows what's behind the doors, opens another
-//! > door, say No. 3, which has a goat. He then says to you, "Do you want to
-//! > pick door No. 2?" Is it to your advantage to switch your choice?
-//!
-//! The rather unintuitive answer is that you will have a 2/3 chance of winning
-//! if you switch and a 1/3 chance of winning if you don't, so it's better to
-//! switch.
-//!
-//! This program will simulate the game show and with large enough simulation
-//! steps it will indeed confirm that it is better to switch.
-//!
-//! [Monty Hall Problem]: http://en.wikipedia.org/wiki/Monty_Hall_problem
+//! let mut rng = rand::thread_rng();
+//! let y: f64 = rng.gen(); // generates a float between 0 and 1
 //!
+//! let mut nums: Vec<i32> = (1..100).collect();
+//! nums.shuffle(&mut rng);
 //! ```
-//! use rand::Rng;
-//! use rand::distributions::{IndependentSample, Range};
-//!
-//! struct SimulationResult {
-//!     win: bool,
-//!     switch: bool,
-//! }
-//!
-//! // Run a single simulation of the Monty Hall problem.
-//! fn simulate<R: Rng>(random_door: &Range<u32>, rng: &mut R)
-//!                     -> SimulationResult {
-//!     let car = random_door.ind_sample(rng);
-//!
-//!     // This is our initial choice
-//!     let mut choice = random_door.ind_sample(rng);
-//!
-//!     // The game host opens a door
-//!     let open = game_host_open(car, choice, rng);
 //!
-//!     // Shall we switch?
-//!     let switch = rng.gen();
-//!     if switch {
-//!         choice = switch_door(choice, open);
-//!     }
+//! # The Book
+//! 
+//! For the user guide and futher documentation, please read
+//! [The Rust Rand Book](https://rust-random.github.io/book).
 //!
-//!     SimulationResult { win: choice == car, switch: switch }
-//! }
-//!
-//! // Returns the door the game host opens given our choice and knowledge of
-//! // where the car is. The game host will never open the door with the car.
-//! fn game_host_open<R: Rng>(car: u32, choice: u32, rng: &mut R) -> u32 {
-//!     let choices = free_doors(&[car, choice]);
-//!     rand::seq::sample_slice(rng, &choices, 1)[0]
-//! }
-//!
-//! // Returns the door we switch to, given our current choice and
-//! // the open door. There will only be one valid door.
-//! fn switch_door(choice: u32, open: u32) -> u32 {
-//!     free_doors(&[choice, open])[0]
-//! }
-//!
-//! fn free_doors(blocked: &[u32]) -> Vec<u32> {
-//!     (0..3).filter(|x| !blocked.contains(x)).collect()
-//! }
-//!
-//! fn main() {
-//!     // The estimation will be more accurate with more simulations
-//!     let num_simulations = 10000;
-//!
-//!     let mut rng = rand::thread_rng();
-//!     let random_door = Range::new(0, 3);
-//!
-//!     let (mut switch_wins, mut switch_losses) = (0, 0);
-//!     let (mut keep_wins, mut keep_losses) = (0, 0);
-//!
-//!     println!("Running {} simulations...", num_simulations);
-//!     for _ in 0..num_simulations {
-//!         let result = simulate(&random_door, &mut rng);
-//!
-//!         match (result.win, result.switch) {
-//!             (true, true) => switch_wins += 1,
-//!             (true, false) => keep_wins += 1,
-//!             (false, true) => switch_losses += 1,
-//!             (false, false) => keep_losses += 1,
-//!         }
-//!     }
-//!
-//!     let total_switches = switch_wins + switch_losses;
-//!     let total_keeps = keep_wins + keep_losses;
-//!
-//!     println!("Switched door {} times with {} wins and {} losses",
-//!              total_switches, switch_wins, switch_losses);
-//!
-//!     println!("Kept our choice {} times with {} wins and {} losses",
-//!              total_keeps, keep_wins, keep_losses);
-//!
-//!     // With a large number of simulations, the values should converge to
-//!     // 0.667 and 0.333 respectively.
-//!     println!("Estimated chance to win if we switch: {}",
-//!              switch_wins as f32 / total_switches as f32);
-//!     println!("Estimated chance to win if we don't: {}",
-//!              keep_wins as f32 / total_keeps as f32);
-//! }
-//! ```
+//! [`distributions` module]: distributions/index.html
+//! [`random()`]: fn.random.html
+//! [`Rng`]: trait.Rng.html
+//! [`seq` module]: seq/index.html
+//! [`thread_rng()`]: fn.thread_rng.html
+
 
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
        html_favicon_url = "https://www.rust-lang.org/favicon.ico",
-       html_root_url = "https://docs.rs/rand/0.4")]
+       html_root_url = "https://rust-random.github.io/rand/")]
 
+#![deny(missing_docs)]
 #![deny(missing_debug_implementations)]
+#![doc(test(attr(allow(unused_variables), deny(warnings))))]
 
 #![cfg_attr(not(feature="std"), no_std)]
 #![cfg_attr(all(feature="alloc", not(feature="std")), feature(alloc))]
-#![cfg_attr(feature = "i128_support", feature(i128_type, i128))]
+#![cfg_attr(all(feature="simd_support", feature="nightly"), feature(stdsimd))]
+#![cfg_attr(feature = "stdweb", recursion_limit="128")]
 
-#[cfg(feature="std")] extern crate std as core;
-#[cfg(all(feature = "alloc", not(feature="std")))] extern crate alloc;
+#[cfg(feature = "std")] extern crate core;
+#[cfg(all(feature = "alloc", not(feature="std")))] #[macro_use] extern crate alloc;
 
-use core::marker;
-use core::mem;
-#[cfg(feature="std")] use std::cell::RefCell;
-#[cfg(feature="std")] use std::io;
-#[cfg(feature="std")] use std::rc::Rc;
+#[cfg(feature="simd_support")] extern crate packed_simd;
 
-// external rngs
-pub use jitter::JitterRng;
-#[cfg(feature="std")] pub use os::OsRng;
+#[cfg(all(target_arch="wasm32", not(target_os="emscripten"), feature="stdweb"))]
+#[macro_use]
+extern crate stdweb;
 
-// pseudo rngs
-pub use isaac::{IsaacRng, Isaac64Rng};
-pub use chacha::ChaChaRng;
-pub use prng::XorShiftRng;
+#[cfg(all(target_arch = "wasm32", feature = "wasm-bindgen"))]
+extern crate wasm_bindgen;
 
-// local use declarations
-#[cfg(target_pointer_width = "32")]
-use prng::IsaacRng as IsaacWordRng;
-#[cfg(target_pointer_width = "64")]
-use prng::Isaac64Rng as IsaacWordRng;
+extern crate rand_core;
+extern crate rand_isaac;    // only for deprecations
+extern crate rand_chacha;    // only for deprecations
+extern crate rand_hc;
+extern crate rand_pcg;
+extern crate rand_xorshift;
 
-use distributions::{Range, IndependentSample};
-use distributions::range::SampleRange;
+#[cfg(feature = "log")] #[macro_use] extern crate log;
+#[allow(unused)]
+#[cfg(not(feature = "log"))] macro_rules! trace { ($($x:tt)*) => () }
+#[allow(unused)]
+#[cfg(not(feature = "log"))] macro_rules! debug { ($($x:tt)*) => () }
+#[allow(unused)]
+#[cfg(not(feature = "log"))] macro_rules! info { ($($x:tt)*) => () }
+#[allow(unused)]
+#[cfg(not(feature = "log"))] macro_rules! warn { ($($x:tt)*) => () }
+#[allow(unused)]
+#[cfg(not(feature = "log"))] macro_rules! error { ($($x:tt)*) => () }
 
-// public modules
-pub mod distributions;
-pub mod jitter;
-#[cfg(feature="std")] pub mod os;
-#[cfg(feature="std")] pub mod read;
-pub mod reseeding;
-#[cfg(any(feature="std", feature = "alloc"))] pub mod seq;
 
-// These tiny modules are here to avoid API breakage, probably only temporarily
+// Re-exports from rand_core
+pub use rand_core::{RngCore, CryptoRng, SeedableRng};
+pub use rand_core::{ErrorKind, Error};
+
+// Public exports
+#[cfg(feature="std")] pub use rngs::thread::thread_rng;
+
+// Public modules
+pub mod distributions;
+pub mod prelude;
+#[deprecated(since="0.6.0")]
+pub mod prng;
+pub mod rngs;
+pub mod seq;
+
+////////////////////////////////////////////////////////////////////////////////
+// Compatibility re-exports. Documentation is hidden; will be removed eventually.
+
+#[doc(hidden)] mod deprecated;
+
+#[allow(deprecated)]
+#[doc(hidden)] pub use deprecated::ReseedingRng;
+
+#[allow(deprecated)]
+#[cfg(feature="std")] #[doc(hidden)] pub use deprecated::EntropyRng;
+
+#[allow(deprecated)]
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[doc(hidden)]
+pub use deprecated::OsRng;
+
+#[allow(deprecated)]
+#[doc(hidden)] pub use deprecated::{ChaChaRng, IsaacRng, Isaac64Rng, XorShiftRng};
+#[allow(deprecated)]
+#[doc(hidden)] pub use deprecated::StdRng;
+
+
+#[allow(deprecated)]
+#[doc(hidden)]
+pub mod jitter {
+    pub use deprecated::JitterRng;
+    pub use rngs::TimerError;
+}
+#[allow(deprecated)]
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[doc(hidden)]
+pub mod os {
+    pub use deprecated::OsRng;
+}
+#[allow(deprecated)]
+#[doc(hidden)]
 pub mod chacha {
-    //! The ChaCha random number generator.
-    pub use prng::ChaChaRng;
+    pub use deprecated::ChaChaRng;
 }
+#[allow(deprecated)]
+#[doc(hidden)]
 pub mod isaac {
-    //! The ISAAC random number generator.
-    pub use prng::{IsaacRng, Isaac64Rng};
+    pub use deprecated::{IsaacRng, Isaac64Rng};
 }
+#[allow(deprecated)]
+#[cfg(feature="std")]
+#[doc(hidden)]
+pub mod read {
+    pub use deprecated::ReadRng;
+}
+
+#[allow(deprecated)]
+#[cfg(feature="std")] #[doc(hidden)] pub use deprecated::ThreadRng;
 
-// private modules
-mod rand_impls;
-mod prng;
+////////////////////////////////////////////////////////////////////////////////
 
 
-/// A type that can be randomly generated using an `Rng`.
+use core::{mem, slice};
+use distributions::{Distribution, Standard};
+use distributions::uniform::{SampleUniform, UniformSampler, SampleBorrow};
+
+/// An automatically-implemented extension trait on [`RngCore`] providing high-level
+/// generic methods for sampling values and other convenience methods.
 ///
-/// ## Built-in Implementations
+/// This is the primary trait to use when generating random values.
 ///
-/// This crate implements `Rand` for various primitive types.  Assuming the
-/// provided `Rng` is well-behaved, these implementations generate values with
-/// the following ranges and distributions:
+/// # Generic usage
 ///
-/// * Integers (`i32`, `u32`, `isize`, `usize`, etc.): Uniformly distributed
-///   over all values of the type.
-/// * `char`: Uniformly distributed over all Unicode scalar values, i.e. all
-///   code points in the range `0...0x10_FFFF`, except for the range
-///   `0xD800...0xDFFF` (the surrogate code points).  This includes
-///   unassigned/reserved code points.
-/// * `bool`: Generates `false` or `true`, each with probability 0.5.
-/// * Floating point types (`f32` and `f64`): Uniformly distributed in the
-///   half-open range `[0, 1)`.  (The [`Open01`], [`Closed01`], [`Exp1`], and
-///   [`StandardNormal`] wrapper types produce floating point numbers with
-///   alternative ranges or distributions.)
+/// The basic pattern is `fn foo<R: Rng + ?Sized>(rng: &mut R)`. Some
+/// things are worth noting here:
 ///
-/// [`Open01`]: struct.Open01.html
-/// [`Closed01`]: struct.Closed01.html
-/// [`Exp1`]: distributions/exponential/struct.Exp1.html
-/// [`StandardNormal`]: distributions/normal/struct.StandardNormal.html
+/// - Since `Rng: RngCore` and every `RngCore` implements `Rng`, it makes no
+///   difference whether we use `R: Rng` or `R: RngCore`.
+/// - The `+ ?Sized` un-bounding allows functions to be called directly on
+///   type-erased references; i.e. `foo(r)` where `r: &mut RngCore`. Without
+///   this it would be necessary to write `foo(&mut r)`.
 ///
-/// The following aggregate types also implement `Rand` as long as their
-/// component types implement it:
+/// An alternative pattern is possible: `fn foo<R: Rng>(rng: R)`. This has some
+/// trade-offs. It allows the argument to be consumed directly without a `&mut`
+/// (which is how `from_rng(thread_rng())` works); also it still works directly
+/// on references (including type-erased references). Unfortunately within the
+/// function `foo` it is not known whether `rng` is a reference type or not,
+/// hence many uses of `rng` require an extra reference, either explicitly
+/// (`distr.sample(&mut rng)`) or implicitly (`rng.gen()`); one may hope the
+/// optimiser can remove redundant references later.
 ///
-/// * Tuples and arrays: Each element of the tuple or array is generated
-///   independently, using its own `Rand` implementation.
-/// * `Option<T>`: Returns `None` with probability 0.5; otherwise generates a
-///   random `T` and returns `Some(T)`.
-pub trait Rand : Sized {
-    /// Generates a random instance of this type using the specified source of
-    /// randomness.
-    fn rand<R: Rng>(rng: &mut R) -> Self;
-}
-
-/// A random number generator.
-pub trait Rng {
-    /// Return the next random u32.
-    ///
-    /// This rarely needs to be called directly, prefer `r.gen()` to
-    /// `r.next_u32()`.
-    // FIXME #rust-lang/rfcs#628: Should be implemented in terms of next_u64
-    fn next_u32(&mut self) -> u32;
-
-    /// Return the next random u64.
-    ///
-    /// By default this is implemented in terms of `next_u32`. An
-    /// implementation of this trait must provide at least one of
-    /// these two methods. Similarly to `next_u32`, this rarely needs
-    /// to be called directly, prefer `r.gen()` to `r.next_u64()`.
-    fn next_u64(&mut self) -> u64 {
-        ((self.next_u32() as u64) << 32) | (self.next_u32() as u64)
-    }
-
-    /// Return the next random f32 selected from the half-open
-    /// interval `[0, 1)`.
-    ///
-    /// This uses a technique described by Saito and Matsumoto at
-    /// MCQMC'08. Given that the IEEE floating point numbers are
-    /// uniformly distributed over [1,2), we generate a number in
-    /// this range and then offset it onto the range [0,1). Our
-    /// choice of bits (masking v. shifting) is arbitrary and
-    /// should be immaterial for high quality generators. For low
-    /// quality generators (ex. LCG), prefer bitshifting due to
-    /// correlation between sequential low order bits.
-    ///
-    /// See:
-    /// A PRNG specialized in double precision floating point numbers using
-    /// an affine transition
-    ///
-    /// * <http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/ARTICLES/dSFMT.pdf>
-    /// * <http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/dSFMT-slide-e.pdf>
+/// Example:
+///
+/// ```
+/// # use rand::thread_rng;
+/// use rand::Rng;
+///
+/// fn foo<R: Rng + ?Sized>(rng: &mut R) -> f32 {
+///     rng.gen()
+/// }
+///
+/// # let v = foo(&mut thread_rng());
+/// ```
+///
+/// [`RngCore`]: trait.RngCore.html
+pub trait Rng: RngCore {
+    /// Return a random value supporting the [`Standard`] distribution.
     ///
-    /// By default this is implemented in terms of `next_u32`, but a
-    /// random number generator which can generate numbers satisfying
-    /// the requirements directly can overload this for performance.
-    /// It is required that the return value lies in `[0, 1)`.
+    /// [`Standard`]: distributions/struct.Standard.html
     ///
-    /// See `Closed01` for the closed interval `[0,1]`, and
-    /// `Open01` for the open interval `(0,1)`.
-    fn next_f32(&mut self) -> f32 {
-        const UPPER_MASK: u32 = 0x3F800000;
-        const LOWER_MASK: u32 = 0x7FFFFF;
-        let tmp = UPPER_MASK | (self.next_u32() & LOWER_MASK);
-        let result: f32 = unsafe { mem::transmute(tmp) };
-        result - 1.0
-    }
-
-    /// Return the next random f64 selected from the half-open
-    /// interval `[0, 1)`.
+    /// # Example
     ///
-    /// By default this is implemented in terms of `next_u64`, but a
-    /// random number generator which can generate numbers satisfying
-    /// the requirements directly can overload this for performance.
-    /// It is required that the return value lies in `[0, 1)`.
+    /// ```
+    /// use rand::{thread_rng, Rng};
     ///
-    /// See `Closed01` for the closed interval `[0,1]`, and
-    /// `Open01` for the open interval `(0,1)`.
-    fn next_f64(&mut self) -> f64 {
-        const UPPER_MASK: u64 = 0x3FF0000000000000;
-        const LOWER_MASK: u64 = 0xFFFFFFFFFFFFF;
-        let tmp = UPPER_MASK | (self.next_u64() & LOWER_MASK);
-        let result: f64 = unsafe { mem::transmute(tmp) };
-        result - 1.0
+    /// let mut rng = thread_rng();
+    /// let x: u32 = rng.gen();
+    /// println!("{}", x);
+    /// println!("{:?}", rng.gen::<(f64, bool)>());
+    /// ```
+    #[inline]
+    fn gen<T>(&mut self) -> T where Standard: Distribution<T> {
+        Standard.sample(self)
     }
 
-    /// Fill `dest` with random data.
+    /// Generate a random value in the range [`low`, `high`), i.e. inclusive of
+    /// `low` and exclusive of `high`.
     ///
-    /// This has a default implementation in terms of `next_u64` and
-    /// `next_u32`, but should be overridden by implementations that
-    /// offer a more efficient solution than just calling those
-    /// methods repeatedly.
+    /// This function is optimised for the case that only a single sample is
+    /// made from the given range. See also the [`Uniform`] distribution
+    /// type which may be faster if sampling from the same range repeatedly.
     ///
-    /// This method does *not* have a requirement to bear any fixed
-    /// relationship to the other methods, for example, it does *not*
-    /// have to result in the same output as progressively filling
-    /// `dest` with `self.gen::<u8>()`, and any such behaviour should
-    /// not be relied upon.
+    /// # Panics
     ///
-    /// This method should guarantee that `dest` is entirely filled
-    /// with new data, and may panic if this is impossible
-    /// (e.g. reading past the end of a file that is being used as the
-    /// source of randomness).
+    /// Panics if `low >= high`.
     ///
     /// # Example
     ///
-    /// ```rust
+    /// ```
     /// use rand::{thread_rng, Rng};
     ///
-    /// let mut v = [0u8; 13579];
-    /// thread_rng().fill_bytes(&mut v);
-    /// println!("{:?}", &v[..]);
+    /// let mut rng = thread_rng();
+    /// let n: u32 = rng.gen_range(0, 10);
+    /// println!("{}", n);
+    /// let m: f64 = rng.gen_range(-40.0f64, 1.3e5f64);
+    /// println!("{}", m);
     /// ```
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        // this could, in theory, be done by transmuting dest to a
-        // [u64], but this is (1) likely to be undefined behaviour for
-        // LLVM, (2) has to be very careful about alignment concerns,
-        // (3) adds more `unsafe` that needs to be checked, (4)
-        // probably doesn't give much performance gain if
-        // optimisations are on.
-        let mut count = 0;
-        let mut num = 0;
-        for byte in dest.iter_mut() {
-            if count == 0 {
-                // we could micro-optimise here by generating a u32 if
-                // we only need a few more bytes to fill the vector
-                // (i.e. at most 4).
-                num = self.next_u64();
-                count = 8;
-            }
-
-            *byte = (num & 0xff) as u8;
-            num >>= 8;
-            count -= 1;
-        }
+    ///
+    /// [`Uniform`]: distributions/uniform/struct.Uniform.html
+    fn gen_range<T: SampleUniform, B1, B2>(&mut self, low: B1, high: B2) -> T
+        where B1: SampleBorrow<T> + Sized,
+              B2: SampleBorrow<T> + Sized {
+        T::Sampler::sample_single(low, high, self)
     }
 
-    /// Return a random value of a `Rand` type.
+    /// Sample a new value, using the given distribution.
     ///
-    /// # Example
+    /// ### Example
     ///
-    /// ```rust
+    /// ```
     /// use rand::{thread_rng, Rng};
+    /// use rand::distributions::Uniform;
     ///
     /// let mut rng = thread_rng();
-    /// let x: u32 = rng.gen();
-    /// println!("{}", x);
-    /// println!("{:?}", rng.gen::<(f64, bool)>());
+    /// let x = rng.sample(Uniform::new(10u32, 15));
+    /// // Type annotation requires two types, the type and distribution; the
+    /// // distribution can be inferred.
+    /// let y = rng.sample::<u16, _>(Uniform::new(10, 15));
     /// ```
-    #[inline(always)]
-    fn gen<T: Rand>(&mut self) -> T where Self: Sized {
-        Rand::rand(self)
+    fn sample<T, D: Distribution<T>>(&mut self, distr: D) -> T {
+        distr.sample(self)
     }
 
-    /// Return an iterator that will yield an infinite number of randomly
-    /// generated items.
+    /// Create an iterator that generates values using the given distribution.
     ///
     /// # Example
     ///
     /// ```
     /// use rand::{thread_rng, Rng};
+    /// use rand::distributions::{Alphanumeric, Uniform, Standard};
     ///
     /// let mut rng = thread_rng();
-    /// let x = rng.gen_iter::<u32>().take(10).collect::<Vec<u32>>();
-    /// println!("{:?}", x);
-    /// println!("{:?}", rng.gen_iter::<(f64, bool)>().take(5)
-    ///                     .collect::<Vec<(f64, bool)>>());
-    /// ```
-    fn gen_iter<'a, T: Rand>(&'a mut self) -> Generator<'a, T, Self> where Self: Sized {
-        Generator { rng: self, _marker: marker::PhantomData }
-    }
-
-    /// Generate a random value in the range [`low`, `high`).
-    ///
-    /// This is a convenience wrapper around
-    /// `distributions::Range`. If this function will be called
-    /// repeatedly with the same arguments, one should use `Range`, as
-    /// that will amortize the computations that allow for perfect
-    /// uniformity, as they only happen on initialization.
-    ///
-    /// # Panics
     ///
-    /// Panics if `low >= high`.
+    /// // Vec of 16 x f32:
+    /// let v: Vec<f32> = thread_rng().sample_iter(&Standard).take(16).collect();
     ///
-    /// # Example
+    /// // String:
+    /// let s: String = rng.sample_iter(&Alphanumeric).take(7).collect();
     ///
-    /// ```rust
-    /// use rand::{thread_rng, Rng};
+    /// // Combined values
+    /// println!("{:?}", thread_rng().sample_iter(&Standard).take(5)
+    ///                              .collect::<Vec<(f64, bool)>>());
     ///
-    /// let mut rng = thread_rng();
-    /// let n: u32 = rng.gen_range(0, 10);
-    /// println!("{}", n);
-    /// let m: f64 = rng.gen_range(-40.0f64, 1.3e5f64);
-    /// println!("{}", m);
+    /// // Dice-rolling:
+    /// let die_range = Uniform::new_inclusive(1, 6);
+    /// let mut roll_die = rng.sample_iter(&die_range);
+    /// while roll_die.next().unwrap() != 6 {
+    ///     println!("Not a 6; rolling again!");
+    /// }
     /// ```
-    fn gen_range<T: PartialOrd + SampleRange>(&mut self, low: T, high: T) -> T where Self: Sized {
-        assert!(low < high, "Rng.gen_range called with low >= high");
-        Range::new(low, high).ind_sample(self)
+    fn sample_iter<'a, T, D: Distribution<T>>(&'a mut self, distr: &'a D)
+        -> distributions::DistIter<'a, D, Self, T> where Self: Sized
+    {
+        distr.sample_iter(self)
     }
 
-    /// Return a bool with a 1 in n chance of true
+    /// Fill `dest` entirely with random bytes (uniform value distribution),
+    /// where `dest` is any type supporting [`AsByteSliceMut`], namely slices
+    /// and arrays over primitive integer types (`i8`, `i16`, `u32`, etc.).
+    ///
+    /// On big-endian platforms this performs byte-swapping to ensure
+    /// portability of results from reproducible generators.
+    ///
+    /// This uses [`fill_bytes`] internally which may handle some RNG errors
+    /// implicitly (e.g. waiting if the OS generator is not ready), but panics
+    /// on other errors. See also [`try_fill`] which returns errors.
     ///
     /// # Example
     ///
-    /// ```rust
+    /// ```
     /// use rand::{thread_rng, Rng};
     ///
-    /// let mut rng = thread_rng();
-    /// println!("{}", rng.gen_weighted_bool(3));
+    /// let mut arr = [0i8; 20];
+    /// thread_rng().fill(&mut arr[..]);
     /// ```
-    fn gen_weighted_bool(&mut self, n: u32) -> bool where Self: Sized {
-        n <= 1 || self.gen_range(0, n) == 0
+    ///
+    /// [`fill_bytes`]: trait.RngCore.html#method.fill_bytes
+    /// [`try_fill`]: trait.Rng.html#method.try_fill
+    /// [`AsByteSliceMut`]: trait.AsByteSliceMut.html
+    fn fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T) {
+        self.fill_bytes(dest.as_byte_slice_mut());
+        dest.to_le();
     }
 
-    /// Return an iterator of random characters from the set A-Z,a-z,0-9.
+    /// Fill `dest` entirely with random bytes (uniform value distribution),
+    /// where `dest` is any type supporting [`AsByteSliceMut`], namely slices
+    /// and arrays over primitive integer types (`i8`, `i16`, `u32`, etc.).
+    ///
+    /// On big-endian platforms this performs byte-swapping to ensure
+    /// portability of results from reproducible generators.
+    ///
+    /// This uses [`try_fill_bytes`] internally and forwards all RNG errors. In
+    /// some cases errors may be resolvable; see [`ErrorKind`] and
+    /// documentation for the RNG in use. If you do not plan to handle these
+    /// errors you may prefer to use [`fill`].
     ///
     /// # Example
     ///
-    /// ```rust
+    /// ```
+    /// # use rand::Error;
     /// use rand::{thread_rng, Rng};
     ///
-    /// let s: String = thread_rng().gen_ascii_chars().take(10).collect();
-    /// println!("{}", s);
+    /// # fn try_inner() -> Result<(), Error> {
+    /// let mut arr = [0u64; 4];
+    /// thread_rng().try_fill(&mut arr[..])?;
+    /// # Ok(())
+    /// # }
+    ///
+    /// # try_inner().unwrap()
     /// ```
-    fn gen_ascii_chars<'a>(&'a mut self) -> AsciiGenerator<'a, Self> where Self: Sized {
-        AsciiGenerator { rng: self }
+    ///
+    /// [`ErrorKind`]: enum.ErrorKind.html
+    /// [`try_fill_bytes`]: trait.RngCore.html#method.try_fill_bytes
+    /// [`fill`]: trait.Rng.html#method.fill
+    /// [`AsByteSliceMut`]: trait.AsByteSliceMut.html
+    fn try_fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T) -> Result<(), Error> {
+        self.try_fill_bytes(dest.as_byte_slice_mut())?;
+        dest.to_le();
+        Ok(())
     }
 
-    /// Return a random element from `values`.
+    /// Return a bool with a probability `p` of being true.
     ///
-    /// Return `None` if `values` is empty.
+    /// See also the [`Bernoulli`] distribution, which may be faster if
+    /// sampling from the same probability repeatedly.
     ///
     /// # Example
     ///
     /// ```
     /// use rand::{thread_rng, Rng};
     ///
-    /// let choices = [1, 2, 4, 8, 16, 32];
     /// let mut rng = thread_rng();
-    /// println!("{:?}", rng.choose(&choices));
-    /// assert_eq!(rng.choose(&choices[..0]), None);
+    /// println!("{}", rng.gen_bool(1.0 / 3.0));
     /// ```
-    fn choose<'a, T>(&mut self, values: &'a [T]) -> Option<&'a T> where Self: Sized {
-        if values.is_empty() {
-            None
-        } else {
-            Some(&values[self.gen_range(0, values.len())])
-        }
-    }
-
-    /// Return a mutable pointer to a random element from `values`.
     ///
-    /// Return `None` if `values` is empty.
-    fn choose_mut<'a, T>(&mut self, values: &'a mut [T]) -> Option<&'a mut T> where Self: Sized {
-        if values.is_empty() {
-            None
-        } else {
-            let len = values.len();
-            Some(&mut values[self.gen_range(0, len)])
-        }
+    /// # Panics
+    ///
+    /// If `p < 0` or `p > 1`.
+    ///
+    /// [`Bernoulli`]: distributions/bernoulli/struct.Bernoulli.html
+    #[inline]
+    fn gen_bool(&mut self, p: f64) -> bool {
+        let d = distributions::Bernoulli::new(p);
+        self.sample(d)
     }
 
-    /// Shuffle a mutable slice in place.
+    /// Return a bool with a probability of `numerator/denominator` of being
+    /// true. I.e. `gen_ratio(2, 3)` has chance of 2 in 3, or about 67%, of
+    /// returning true. If `numerator == denominator`, then the returned value
+    /// is guaranteed to be `true`. If `numerator == 0`, then the returned
+    /// value is guaranteed to be `false`.
+    ///
+    /// See also the [`Bernoulli`] distribution, which may be faster if
+    /// sampling from the same `numerator` and `denominator` repeatedly.
     ///
-    /// This applies Durstenfeld's algorithm for the [Fisher–Yates shuffle](https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm)
-    /// which produces an unbiased permutation.
+    /// # Panics
+    ///
+    /// If `denominator == 0` or `numerator > denominator`.
     ///
     /// # Example
     ///
-    /// ```rust
+    /// ```
     /// use rand::{thread_rng, Rng};
     ///
     /// let mut rng = thread_rng();
-    /// let mut y = [1, 2, 3];
-    /// rng.shuffle(&mut y);
-    /// println!("{:?}", y);
-    /// rng.shuffle(&mut y);
-    /// println!("{:?}", y);
+    /// println!("{}", rng.gen_ratio(2, 3));
     /// ```
-    fn shuffle<T>(&mut self, values: &mut [T]) where Self: Sized {
-        let mut i = values.len();
-        while i >= 2 {
-            // invariant: elements with index >= i have been locked in place.
-            i -= 1;
-            // lock element i in place.
-            values.swap(i, self.gen_range(0, i + 1));
-        }
-    }
-}
-
-impl<'a, R: ?Sized> Rng for &'a mut R where R: Rng {
-    fn next_u32(&mut self) -> u32 {
-        (**self).next_u32()
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        (**self).next_u64()
+    ///
+    /// [`Bernoulli`]: distributions/bernoulli/struct.Bernoulli.html
+    #[inline]
+    fn gen_ratio(&mut self, numerator: u32, denominator: u32) -> bool {
+        let d = distributions::Bernoulli::from_ratio(numerator, denominator);
+        self.sample(d)
     }
 
-    fn next_f32(&mut self) -> f32 {
-        (**self).next_f32()
+    /// Return a random element from `values`.
+    ///
+    /// Deprecated: use [`SliceRandom::choose`] instead.
+    ///
+    /// [`SliceRandom::choose`]: seq/trait.SliceRandom.html#method.choose
+    #[deprecated(since="0.6.0", note="use SliceRandom::choose instead")]
+    fn choose<'a, T>(&mut self, values: &'a [T]) -> Option<&'a T> {
+        use seq::SliceRandom;
+        values.choose(self)
     }
 
-    fn next_f64(&mut self) -> f64 {
-        (**self).next_f64()
+    /// Return a mutable pointer to a random element from `values`.
+    ///
+    /// Deprecated: use [`SliceRandom::choose_mut`] instead.
+    ///
+    /// [`SliceRandom::choose_mut`]: seq/trait.SliceRandom.html#method.choose_mut
+    #[deprecated(since="0.6.0", note="use SliceRandom::choose_mut instead")]
+    fn choose_mut<'a, T>(&mut self, values: &'a mut [T]) -> Option<&'a mut T> {
+        use seq::SliceRandom;
+        values.choose_mut(self)
     }
 
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        (**self).fill_bytes(dest)
+    /// Shuffle a mutable slice in place.
+    ///
+    /// Deprecated: use [`SliceRandom::shuffle`] instead.
+    ///
+    /// [`SliceRandom::shuffle`]: seq/trait.SliceRandom.html#method.shuffle
+    #[deprecated(since="0.6.0", note="use SliceRandom::shuffle instead")]
+    fn shuffle<T>(&mut self, values: &mut [T]) {
+        use seq::SliceRandom;
+        values.shuffle(self)
     }
 }
 
-#[cfg(feature="std")]
-impl<R: ?Sized> Rng for Box<R> where R: Rng {
-    fn next_u32(&mut self) -> u32 {
-        (**self).next_u32()
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        (**self).next_u64()
-    }
-
-    fn next_f32(&mut self) -> f32 {
-        (**self).next_f32()
-    }
-
-    fn next_f64(&mut self) -> f64 {
-        (**self).next_f64()
-    }
-
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        (**self).fill_bytes(dest)
-    }
-}
+impl<R: RngCore + ?Sized> Rng for R {}
 
-/// Iterator which will generate a stream of random items.
+/// Trait for casting types to byte slices
 ///
-/// This iterator is created via the [`gen_iter`] method on [`Rng`].
+/// This is used by the [`fill`] and [`try_fill`] methods.
 ///
-/// [`gen_iter`]: trait.Rng.html#method.gen_iter
-/// [`Rng`]: trait.Rng.html
-#[derive(Debug)]
-pub struct Generator<'a, T, R:'a> {
-    rng: &'a mut R,
-    _marker: marker::PhantomData<fn() -> T>,
-}
-
-impl<'a, T: Rand, R: Rng> Iterator for Generator<'a, T, R> {
-    type Item = T;
+/// [`fill`]: trait.Rng.html#method.fill
+/// [`try_fill`]: trait.Rng.html#method.try_fill
+pub trait AsByteSliceMut {
+    /// Return a mutable reference to self as a byte slice
+    fn as_byte_slice_mut(&mut self) -> &mut [u8];
 
-    fn next(&mut self) -> Option<T> {
-        Some(self.rng.gen())
-    }
-}
-
-/// Iterator which will continuously generate random ascii characters.
-///
-/// This iterator is created via the [`gen_ascii_chars`] method on [`Rng`].
-///
-/// [`gen_ascii_chars`]: trait.Rng.html#method.gen_ascii_chars
-/// [`Rng`]: trait.Rng.html
-#[derive(Debug)]
-pub struct AsciiGenerator<'a, R:'a> {
-    rng: &'a mut R,
+    /// Call `to_le` on each element (i.e. byte-swap on Big Endian platforms).
+    fn to_le(&mut self);
 }
 
-impl<'a, R: Rng> Iterator for AsciiGenerator<'a, R> {
-    type Item = char;
-
-    fn next(&mut self) -> Option<char> {
-        const GEN_ASCII_STR_CHARSET: &'static [u8] =
-            b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
-              abcdefghijklmnopqrstuvwxyz\
-              0123456789";
-        Some(*self.rng.choose(GEN_ASCII_STR_CHARSET).unwrap() as char)
+impl AsByteSliceMut for [u8] {
+    fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+        self
     }
-}
 
-/// A random number generator that can be explicitly seeded to produce
-/// the same stream of randomness multiple times.
-pub trait SeedableRng<Seed>: Rng {
-    /// Reseed an RNG with the given seed.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use rand::{Rng, SeedableRng, StdRng};
-    ///
-    /// let seed: &[_] = &[1, 2, 3, 4];
-    /// let mut rng: StdRng = SeedableRng::from_seed(seed);
-    /// println!("{}", rng.gen::<f64>());
-    /// rng.reseed(&[5, 6, 7, 8]);
-    /// println!("{}", rng.gen::<f64>());
-    /// ```
-    fn reseed(&mut self, Seed);
-
-    /// Create a new RNG with the given seed.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use rand::{Rng, SeedableRng, StdRng};
-    ///
-    /// let seed: &[_] = &[1, 2, 3, 4];
-    /// let mut rng: StdRng = SeedableRng::from_seed(seed);
-    /// println!("{}", rng.gen::<f64>());
-    /// ```
-    fn from_seed(seed: Seed) -> Self;
-}
-
-/// A wrapper for generating floating point numbers uniformly in the
-/// open interval `(0,1)` (not including either endpoint).
-///
-/// Use `Closed01` for the closed interval `[0,1]`, and the default
-/// `Rand` implementation for `f32` and `f64` for the half-open
-/// `[0,1)`.
-///
-/// # Example
-/// ```rust
-/// use rand::{random, Open01};
-///
-/// let Open01(val) = random::<Open01<f32>>();
-/// println!("f32 from (0,1): {}", val);
-/// ```
-#[derive(Debug)]
-pub struct Open01<F>(pub F);
-
-/// A wrapper for generating floating point numbers uniformly in the
-/// closed interval `[0,1]` (including both endpoints).
-///
-/// Use `Open01` for the closed interval `(0,1)`, and the default
-/// `Rand` implementation of `f32` and `f64` for the half-open
-/// `[0,1)`.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{random, Closed01};
-///
-/// let Closed01(val) = random::<Closed01<f32>>();
-/// println!("f32 from [0,1]: {}", val);
-/// ```
-#[derive(Debug)]
-pub struct Closed01<F>(pub F);
-
-/// The standard RNG. This is designed to be efficient on the current
-/// platform.
-#[derive(Copy, Clone, Debug)]
-pub struct StdRng {
-    rng: IsaacWordRng,
+    fn to_le(&mut self) {}
 }
 
-impl StdRng {
-    /// Create a randomly seeded instance of `StdRng`.
-    ///
-    /// This is a very expensive operation as it has to read
-    /// randomness from the operating system and use this in an
-    /// expensive seeding operation. If one is only generating a small
-    /// number of random numbers, or doesn't need the utmost speed for
-    /// generating each number, `thread_rng` and/or `random` may be more
-    /// appropriate.
-    ///
-    /// Reading the randomness from the OS may fail, and any error is
-    /// propagated via the `io::Result` return value.
-    #[cfg(feature="std")]
-    pub fn new() -> io::Result<StdRng> {
-        match OsRng::new() {
-            Ok(mut r) => Ok(StdRng { rng: r.gen() }),
-            Err(e1) => {
-                match JitterRng::new() {
-                    Ok(mut r) => Ok(StdRng { rng: r.gen() }),
-                    Err(_) => {
-                        Err(e1)
+macro_rules! impl_as_byte_slice {
+    ($t:ty) => {
+        impl AsByteSliceMut for [$t] {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                if self.len() == 0 {
+                    unsafe {
+                        // must not use null pointer
+                        slice::from_raw_parts_mut(0x1 as *mut u8, 0)
+                    }
+                } else {
+                    unsafe {
+                        slice::from_raw_parts_mut(&mut self[0]
+                            as *mut $t
+                            as *mut u8,
+                            self.len() * mem::size_of::<$t>()
+                        )
                     }
                 }
             }
-        }
-    }
-}
 
-impl Rng for StdRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        self.rng.next_u32()
-    }
-
-    #[inline]
-    fn next_u64(&mut self) -> u64 {
-        self.rng.next_u64()
-    }
-}
-
-impl<'a> SeedableRng<&'a [usize]> for StdRng {
-    fn reseed(&mut self, seed: &'a [usize]) {
-        // the internal RNG can just be seeded from the above
-        // randomness.
-        self.rng.reseed(unsafe {mem::transmute(seed)})
-    }
-
-    fn from_seed(seed: &'a [usize]) -> StdRng {
-        StdRng { rng: SeedableRng::from_seed(unsafe {mem::transmute(seed)}) }
+            fn to_le(&mut self) {
+                for x in self {
+                    *x = x.to_le();
+                }
+            }
+        }
     }
 }
 
-/// Create a weak random number generator with a default algorithm and seed.
-///
-/// It returns the fastest `Rng` algorithm currently available in Rust without
-/// consideration for cryptography or security. If you require a specifically
-/// seeded `Rng` for consistency over time you should pick one algorithm and
-/// create the `Rng` yourself.
-///
-/// This will seed the generator with randomness from thread_rng.
-#[cfg(feature="std")]
-pub fn weak_rng() -> XorShiftRng {
-    thread_rng().gen()
-}
+impl_as_byte_slice!(u16);
+impl_as_byte_slice!(u32);
+impl_as_byte_slice!(u64);
+#[cfg(rust_1_26)] impl_as_byte_slice!(u128);
+impl_as_byte_slice!(usize);
+impl_as_byte_slice!(i8);
+impl_as_byte_slice!(i16);
+impl_as_byte_slice!(i32);
+impl_as_byte_slice!(i64);
+#[cfg(rust_1_26)] impl_as_byte_slice!(i128);
+impl_as_byte_slice!(isize);
+
+macro_rules! impl_as_byte_slice_arrays {
+    ($n:expr,) => {};
+    ($n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!($n - 1, $($NN,)*);
+
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
 
-/// Controls how the thread-local RNG is reseeded.
-#[cfg(feature="std")]
-#[derive(Debug)]
-struct ThreadRngReseeder;
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
+        }
+    };
+    (!div $n:expr,) => {};
+    (!div $n:expr, $N:ident, $($NN:ident,)*) => {
+        impl_as_byte_slice_arrays!(!div $n / 2, $($NN,)*);
+
+        impl<T> AsByteSliceMut for [T; $n] where [T]: AsByteSliceMut {
+            fn as_byte_slice_mut(&mut self) -> &mut [u8] {
+                self[..].as_byte_slice_mut()
+            }
 
-#[cfg(feature="std")]
-impl reseeding::Reseeder<StdRng> for ThreadRngReseeder {
-    fn reseed(&mut self, rng: &mut StdRng) {
-        match StdRng::new() {
-            Ok(r) => *rng = r,
-            Err(e) => panic!("No entropy available: {}", e),
+            fn to_le(&mut self) {
+                self[..].to_le()
+            }
         }
-    }
+    };
 }
-#[cfg(feature="std")]
-const THREAD_RNG_RESEED_THRESHOLD: u64 = 32_768;
-#[cfg(feature="std")]
-type ThreadRngInner = reseeding::ReseedingRng<StdRng, ThreadRngReseeder>;
+impl_as_byte_slice_arrays!(32, N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,);
+impl_as_byte_slice_arrays!(!div 4096, N,N,N,N,N,N,N,);
 
-/// The thread-local RNG.
-#[cfg(feature="std")]
-#[derive(Clone, Debug)]
-pub struct ThreadRng {
-    rng: Rc<RefCell<ThreadRngInner>>,
-}
 
-/// Retrieve the lazily-initialized thread-local random number
-/// generator, seeded by the system. Intended to be used in method
-/// chaining style, e.g. `thread_rng().gen::<i32>()`.
+/// A convenience extension to [`SeedableRng`] allowing construction from fresh
+/// entropy. This trait is automatically implemented for any PRNG implementing
+/// [`SeedableRng`] and is not intended to be implemented by users.
+///
+/// This is equivalent to using `SeedableRng::from_rng(EntropyRng::new())` then
+/// unwrapping the result.
+///
+/// Since this is convenient and secure, it is the recommended way to create
+/// PRNGs, though two alternatives may be considered:
+///
+/// *   Deterministic creation using [`SeedableRng::from_seed`] with a fixed seed
+/// *   Seeding from `thread_rng`: `SeedableRng::from_rng(thread_rng())?`;
+///     this will usually be faster and should also be secure, but requires
+///     trusting one extra component.
 ///
-/// After generating a certain amount of randomness, the RNG will reseed itself
-/// from the operating system or, if the operating system RNG returns an error,
-/// a seed based on the current system time.
+/// ## Example
 ///
-/// The internal RNG used is platform and architecture dependent, even
-/// if the operating system random number generator is rigged to give
-/// the same sequence always. If absolute consistency is required,
-/// explicitly select an RNG, e.g. `IsaacRng` or `Isaac64Rng`.
+/// ```
+/// use rand::{Rng, FromEntropy};
+/// use rand::rngs::StdRng;
+///
+/// let mut rng = StdRng::from_entropy();
+/// println!("Random die roll: {}", rng.gen_range(1, 7));
+/// ```
+///
+/// [`EntropyRng`]: rngs/struct.EntropyRng.html
+/// [`SeedableRng`]: trait.SeedableRng.html
+/// [`SeedableRng::from_seed`]: trait.SeedableRng.html#tymethod.from_seed
 #[cfg(feature="std")]
-pub fn thread_rng() -> ThreadRng {
-    // used to make space in TLS for a random number generator
-    thread_local!(static THREAD_RNG_KEY: Rc<RefCell<ThreadRngInner>> = {
-        let r = match StdRng::new() {
-            Ok(r) => r,
-            Err(e) => panic!("No entropy available: {}", e),
-        };
-        let rng = reseeding::ReseedingRng::new(r,
-                                               THREAD_RNG_RESEED_THRESHOLD,
-                                               ThreadRngReseeder);
-        Rc::new(RefCell::new(rng))
-    });
-
-    ThreadRng { rng: THREAD_RNG_KEY.with(|t| t.clone()) }
+pub trait FromEntropy: SeedableRng {
+    /// Creates a new instance, automatically seeded with fresh entropy.
+    ///
+    /// Normally this will use `OsRng`, but if that fails `JitterRng` will be
+    /// used instead. Both should be suitable for cryptography. It is possible
+    /// that both entropy sources will fail though unlikely; failures would
+    /// almost certainly be platform limitations or build issues, i.e. most
+    /// applications targetting PC/mobile platforms should not need to worry
+    /// about this failing.
+    ///
+    /// # Panics
+    ///
+    /// If all entropy sources fail this will panic. If you need to handle
+    /// errors, use the following code, equivalent aside from error handling:
+    ///
+    /// ```
+    /// # use rand::Error;
+    /// use rand::prelude::*;
+    /// use rand::rngs::EntropyRng;
+    ///
+    /// # fn try_inner() -> Result<(), Error> {
+    /// // This uses StdRng, but is valid for any R: SeedableRng
+    /// let mut rng = StdRng::from_rng(EntropyRng::new())?;
+    ///
+    /// println!("random number: {}", rng.gen_range(1, 10));
+    /// # Ok(())
+    /// # }
+    ///
+    /// # try_inner().unwrap()
+    /// ```
+    fn from_entropy() -> Self;
 }
 
 #[cfg(feature="std")]
-impl Rng for ThreadRng {
-    fn next_u32(&mut self) -> u32 {
-        self.rng.borrow_mut().next_u32()
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        self.rng.borrow_mut().next_u64()
-    }
-
-    #[inline]
-    fn fill_bytes(&mut self, bytes: &mut [u8]) {
-        self.rng.borrow_mut().fill_bytes(bytes)
+impl<R: SeedableRng> FromEntropy for R {
+    fn from_entropy() -> R {
+        R::from_rng(rngs::EntropyRng::new()).unwrap_or_else(|err|
+            panic!("FromEntropy::from_entropy() failed: {}", err))
     }
 }
 
+
 /// Generates a random value using the thread-local random number generator.
 ///
-/// `random()` can generate various types of random things, and so may require
-/// type hinting to generate the specific type you want.
-///
-/// This function uses the thread local random number generator. This means
-/// that if you're calling `random()` in a loop, caching the generator can
-/// increase performance. An example is shown below.
+/// This is simply a shortcut for `thread_rng().gen()`. See [`thread_rng`] for
+/// documentation of the entropy source and [`Standard`] for documentation of
+/// distributions and type-specific generation.
 ///
 /// # Examples
 ///
@@ -931,7 +683,8 @@ impl Rng for ThreadRng {
 /// }
 /// ```
 ///
-/// Caching the thread local random number generator:
+/// If you're calling `random()` in a loop, caching the generator as in the
+/// following example can increase performance.
 ///
 /// ```
 /// use rand::Rng;
@@ -950,93 +703,109 @@ impl Rng for ThreadRng {
 ///     *x = rng.gen();
 /// }
 /// ```
+///
+/// [`thread_rng`]: fn.thread_rng.html
+/// [`Standard`]: distributions/struct.Standard.html
 #[cfg(feature="std")]
 #[inline]
-pub fn random<T: Rand>() -> T {
+pub fn random<T>() -> T where Standard: Distribution<T> {
     thread_rng().gen()
 }
 
-/// DEPRECATED: use `seq::sample_iter` instead.
-///
-/// Randomly sample up to `amount` elements from a finite iterator.
-/// The order of elements in the sample is not random.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{thread_rng, sample};
-///
-/// let mut rng = thread_rng();
-/// let sample = sample(&mut rng, 1..100, 5);
-/// println!("{:?}", sample);
-/// ```
-#[cfg(feature="std")]
-#[inline(always)]
-#[deprecated(since="0.4.0", note="renamed to seq::sample_iter")]
-pub fn sample<T, I, R>(rng: &mut R, iterable: I, amount: usize) -> Vec<T>
-    where I: IntoIterator<Item=T>,
-          R: Rng,
-{
-    // the legacy sample didn't care whether amount was met
-    seq::sample_iter(rng, iterable, amount)
-        .unwrap_or_else(|e| e)
+// Due to rustwasm/wasm-bindgen#201 this can't be defined in the inner os
+// modules, so hack around it for now and place it at the root.
+#[cfg(all(feature = "wasm-bindgen", target_arch = "wasm32"))]
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+pub mod __wbg_shims {
+
+    // `extern { type Foo; }` isn't supported on 1.22 syntactically, so use a
+    // macro to work around that.
+    macro_rules! rust_122_compat {
+        ($($t:tt)*) => ($($t)*)
+    }
+
+    rust_122_compat! {
+        extern crate wasm_bindgen;
+
+        pub use wasm_bindgen::prelude::*;
+
+        #[wasm_bindgen]
+        extern "C" {
+            pub type Function;
+            #[wasm_bindgen(constructor)]
+            pub fn new(s: &str) -> Function;
+            #[wasm_bindgen(method)]
+            pub fn call(this: &Function, self_: &JsValue) -> JsValue;
+
+            pub type This;
+            #[wasm_bindgen(method, getter, structural, js_name = self)]
+            pub fn self_(me: &This) -> JsValue;
+            #[wasm_bindgen(method, getter, structural)]
+            pub fn crypto(me: &This) -> JsValue;
+
+            #[derive(Clone, Debug)]
+            pub type BrowserCrypto;
+
+            // TODO: these `structural` annotations here ideally wouldn't be here to
+            // avoid a JS shim, but for now with feature detection they're
+            // unavoidable.
+            #[wasm_bindgen(method, js_name = getRandomValues, structural, getter)]
+            pub fn get_random_values_fn(me: &BrowserCrypto) -> JsValue;
+            #[wasm_bindgen(method, js_name = getRandomValues, structural)]
+            pub fn get_random_values(me: &BrowserCrypto, buf: &mut [u8]);
+
+            #[wasm_bindgen(js_name = require)]
+            pub fn node_require(s: &str) -> NodeCrypto;
+
+            #[derive(Clone, Debug)]
+            pub type NodeCrypto;
+
+            #[wasm_bindgen(method, js_name = randomFillSync, structural)]
+            pub fn random_fill_sync(me: &NodeCrypto, buf: &mut [u8]);
+        }
+    }
 }
 
 #[cfg(test)]
 mod test {
-    use super::{Rng, thread_rng, random, SeedableRng, StdRng, weak_rng};
-    use std::iter::repeat;
+    use rngs::mock::StepRng;
+    use rngs::StdRng;
+    use super::*;
+    #[cfg(all(not(feature="std"), feature="alloc"))] use alloc::boxed::Box;
 
-    pub struct MyRng<R> { inner: R }
+    pub struct TestRng<R> { inner: R }
 
-    impl<R: Rng> Rng for MyRng<R> {
+    impl<R: RngCore> RngCore for TestRng<R> {
         fn next_u32(&mut self) -> u32 {
-            fn next<T: Rng>(t: &mut T) -> u32 {
-                t.next_u32()
-            }
-            next(&mut self.inner)
+            self.inner.next_u32()
+        }
+        fn next_u64(&mut self) -> u64 {
+            self.inner.next_u64()
+        }
+        fn fill_bytes(&mut self, dest: &mut [u8]) {
+            self.inner.fill_bytes(dest)
+        }
+        fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            self.inner.try_fill_bytes(dest)
         }
     }
 
-    pub fn rng() -> MyRng<::ThreadRng> {
-        MyRng { inner: ::thread_rng() }
-    }
-
-    struct ConstRng { i: u64 }
-    impl Rng for ConstRng {
-        fn next_u32(&mut self) -> u32 { self.i as u32 }
-        fn next_u64(&mut self) -> u64 { self.i }
-
-        // no fill_bytes on purpose
-    }
-
-    pub fn iter_eq<I, J>(i: I, j: J) -> bool
-        where I: IntoIterator,
-              J: IntoIterator<Item=I::Item>,
-              I::Item: Eq
-    {
-        // make sure the iterators have equal length
-        let mut i = i.into_iter();
-        let mut j = j.into_iter();
-        loop {
-            match (i.next(), j.next()) {
-                (Some(ref ei), Some(ref ej)) if ei == ej => { }
-                (None, None) => return true,
-                _ => return false,
-            }
-        }
+    pub fn rng(seed: u64) -> TestRng<StdRng> {
+        TestRng { inner: StdRng::seed_from_u64(seed) }
     }
 
     #[test]
     fn test_fill_bytes_default() {
-        let mut r = ConstRng { i: 0x11_22_33_44_55_66_77_88 };
+        let mut r = StepRng::new(0x11_22_33_44_55_66_77_88, 0);
 
         // check every remainder mod 8, both in small and big vectors.
         let lengths = [0, 1, 2, 3, 4, 5, 6, 7,
                        80, 81, 82, 83, 84, 85, 86, 87];
         for &n in lengths.iter() {
-            let mut v = repeat(0u8).take(n).collect::<Vec<_>>();
-            r.fill_bytes(&mut v);
+            let mut buffer = [0u8; 87];
+            let v = &mut buffer[0..n];
+            r.fill_bytes(v);
 
             // use this to get nicer error messages.
             for (i, &byte) in v.iter().enumerate() {
@@ -1048,127 +817,100 @@ mod test {
     }
 
     #[test]
-    fn test_gen_range() {
-        let mut r = thread_rng();
-        for _ in 0..1000 {
-            let a = r.gen_range(-3, 42);
-            assert!(a >= -3 && a < 42);
-            assert_eq!(r.gen_range(0, 1), 0);
-            assert_eq!(r.gen_range(-12, -11), -12);
-        }
+    fn test_fill() {
+        let x = 9041086907909331047;    // a random u64
+        let mut rng = StepRng::new(x, 0);
+
+        // Convert to byte sequence and back to u64; byte-swap twice if BE.
+        let mut array = [0u64; 2];
+        rng.fill(&mut array[..]);
+        assert_eq!(array, [x, x]);
+        assert_eq!(rng.next_u64(), x);
 
+        // Convert to bytes then u32 in LE order
+        let mut array = [0u32; 2];
+        rng.fill(&mut array[..]);
+        assert_eq!(array, [x as u32, (x >> 32) as u32]);
+        assert_eq!(rng.next_u32(), x as u32);
+    }
+
+    #[test]
+    fn test_fill_empty() {
+        let mut array = [0u32; 0];
+        let mut rng = StepRng::new(0, 1);
+        rng.fill(&mut array);
+        rng.fill(&mut array[..]);
+    }
+
+    #[test]
+    fn test_gen_range() {
+        let mut r = rng(101);
         for _ in 0..1000 {
-            let a = r.gen_range(10, 42);
-            assert!(a >= 10 && a < 42);
-            assert_eq!(r.gen_range(0, 1), 0);
+            let a = r.gen_range(-4711, 17);
+            assert!(a >= -4711 && a < 17);
+            let a = r.gen_range(-3i8, 42);
+            assert!(a >= -3i8 && a < 42i8);
+            let a = r.gen_range(&10u16, 99);
+            assert!(a >= 10u16 && a < 99u16);
+            let a = r.gen_range(-100i32, &2000);
+            assert!(a >= -100i32 && a < 2000i32);
+            let a = r.gen_range(&12u32, &24u32);
+            assert!(a >= 12u32 && a < 24u32);
+
+            assert_eq!(r.gen_range(0u32, 1), 0u32);
+            assert_eq!(r.gen_range(-12i64, -11), -12i64);
             assert_eq!(r.gen_range(3_000_000, 3_000_001), 3_000_000);
         }
-
     }
 
     #[test]
     #[should_panic]
     fn test_gen_range_panic_int() {
-        let mut r = thread_rng();
+        let mut r = rng(102);
         r.gen_range(5, -2);
     }
 
     #[test]
     #[should_panic]
     fn test_gen_range_panic_usize() {
-        let mut r = thread_rng();
+        let mut r = rng(103);
         r.gen_range(5, 2);
     }
 
     #[test]
-    fn test_gen_weighted_bool() {
-        let mut r = thread_rng();
-        assert_eq!(r.gen_weighted_bool(0), true);
-        assert_eq!(r.gen_weighted_bool(1), true);
-    }
-
-    #[test]
-    fn test_gen_ascii_str() {
-        let mut r = thread_rng();
-        assert_eq!(r.gen_ascii_chars().take(0).count(), 0);
-        assert_eq!(r.gen_ascii_chars().take(10).count(), 10);
-        assert_eq!(r.gen_ascii_chars().take(16).count(), 16);
-    }
-
-    #[test]
-    fn test_gen_vec() {
-        let mut r = thread_rng();
-        assert_eq!(r.gen_iter::<u8>().take(0).count(), 0);
-        assert_eq!(r.gen_iter::<u8>().take(10).count(), 10);
-        assert_eq!(r.gen_iter::<f64>().take(16).count(), 16);
-    }
-
-    #[test]
-    fn test_choose() {
-        let mut r = thread_rng();
-        assert_eq!(r.choose(&[1, 1, 1]).map(|&x|x), Some(1));
-
-        let v: &[isize] = &[];
-        assert_eq!(r.choose(v), None);
-    }
-
-    #[test]
-    fn test_shuffle() {
-        let mut r = thread_rng();
-        let empty: &mut [isize] = &mut [];
-        r.shuffle(empty);
-        let mut one = [1];
-        r.shuffle(&mut one);
-        let b: &[_] = &[1];
-        assert_eq!(one, b);
-
-        let mut two = [1, 2];
-        r.shuffle(&mut two);
-        assert!(two == [1, 2] || two == [2, 1]);
-
-        let mut x = [1, 1, 1];
-        r.shuffle(&mut x);
-        let b: &[_] = &[1, 1, 1];
-        assert_eq!(x, b);
+    fn test_gen_bool() {
+        let mut r = rng(105);
+        for _ in 0..5 {
+            assert_eq!(r.gen_bool(0.0), false);
+            assert_eq!(r.gen_bool(1.0), true);
+        }
     }
 
     #[test]
-    fn test_thread_rng() {
-        let mut r = thread_rng();
+    fn test_rng_trait_object() {
+        use distributions::{Distribution, Standard};
+        let mut rng = rng(109);
+        let mut r = &mut rng as &mut RngCore;
+        r.next_u32();
         r.gen::<i32>();
-        let mut v = [1, 1, 1];
-        r.shuffle(&mut v);
-        let b: &[_] = &[1, 1, 1];
-        assert_eq!(v, b);
         assert_eq!(r.gen_range(0, 1), 0);
+        let _c: u8 = Standard.sample(&mut r);
     }
 
     #[test]
-    fn test_rng_trait_object() {
-        let mut rng = thread_rng();
-        {
-            let mut r = &mut rng as &mut Rng;
-            r.next_u32();
-            (&mut r).gen::<i32>();
-            let mut v = [1, 1, 1];
-            (&mut r).shuffle(&mut v);
-            let b: &[_] = &[1, 1, 1];
-            assert_eq!(v, b);
-            assert_eq!((&mut r).gen_range(0, 1), 0);
-        }
-        {
-            let mut r = Box::new(rng) as Box<Rng>;
-            r.next_u32();
-            r.gen::<i32>();
-            let mut v = [1, 1, 1];
-            r.shuffle(&mut v);
-            let b: &[_] = &[1, 1, 1];
-            assert_eq!(v, b);
-            assert_eq!(r.gen_range(0, 1), 0);
-        }
+    #[cfg(feature="alloc")]
+    fn test_rng_boxed_trait() {
+        use distributions::{Distribution, Standard};
+        let rng = rng(110);
+        let mut r = Box::new(rng) as Box<RngCore>;
+        r.next_u32();
+        r.gen::<i32>();
+        assert_eq!(r.gen_range(0, 1), 0);
+        let _c: u8 = Standard.sample(&mut r);
     }
 
     #[test]
+    #[cfg(feature="std")]
     fn test_random() {
         // not sure how to test this aside from just getting some values
         let _n : usize = random();
@@ -1183,32 +925,20 @@ mod test {
     }
 
     #[test]
-    fn test_std_rng_seeded() {
-        let s = thread_rng().gen_iter::<usize>().take(256).collect::<Vec<usize>>();
-        let mut ra: StdRng = SeedableRng::from_seed(&s[..]);
-        let mut rb: StdRng = SeedableRng::from_seed(&s[..]);
-        assert!(iter_eq(ra.gen_ascii_chars().take(100),
-                        rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_std_rng_reseed() {
-        let s = thread_rng().gen_iter::<usize>().take(256).collect::<Vec<usize>>();
-        let mut r: StdRng = SeedableRng::from_seed(&s[..]);
-        let string1 = r.gen_ascii_chars().take(100).collect::<String>();
-
-        r.reseed(&s);
-
-        let string2 = r.gen_ascii_chars().take(100).collect::<String>();
-        assert_eq!(string1, string2);
-    }
-
-    #[test]
-    fn test_weak_rng() {
-        let s = weak_rng().gen_iter::<usize>().take(256).collect::<Vec<usize>>();
-        let mut ra: StdRng = SeedableRng::from_seed(&s[..]);
-        let mut rb: StdRng = SeedableRng::from_seed(&s[..]);
-        assert!(iter_eq(ra.gen_ascii_chars().take(100),
-                        rb.gen_ascii_chars().take(100)));
+    fn test_gen_ratio_average() {
+        const NUM: u32 = 3;
+        const DENOM: u32 = 10;
+        const N: u32 = 100_000;
+
+        let mut sum: u32 = 0;
+        let mut rng = rng(111);
+        for _ in 0..N {
+            if rng.gen_ratio(NUM, DENOM) {
+                sum += 1;
+            }
+        }
+        // Have Binomial(N, NUM/DENOM) distribution
+        let expected = (NUM * N) / DENOM;   // exact integer
+        assert!(((sum - expected) as i32).abs() < 500);
     }
 }
diff --git a/rand/src/os.rs b/rand/src/os.rs
deleted file mode 100644
index 10022fb..0000000
--- a/rand/src/os.rs
+++ /dev/null
@@ -1,617 +0,0 @@
-// Copyright 2013-2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Interfaces to the operating system provided random number
-//! generators.
-
-use std::{io, mem, fmt};
-use Rng;
-
-/// A random number generator that retrieves randomness straight from
-/// the operating system. Platform sources:
-///
-/// - Unix-like systems (Linux, Android, Mac OSX): read directly from
-///   `/dev/urandom`, or from `getrandom(2)` system call if available.
-/// - OpenBSD: calls `getentropy(2)`
-/// - FreeBSD: uses the `kern.arandom` `sysctl(2)` mib
-/// - Windows: calls `RtlGenRandom`, exported from `advapi32.dll` as
-///   `SystemFunction036`.
-/// - iOS: calls SecRandomCopyBytes as /dev/(u)random is sandboxed.
-/// - PNaCl: calls into the `nacl-irt-random-0.1` IRT interface.
-///
-/// This usually does not block. On some systems (e.g. FreeBSD, OpenBSD,
-/// Max OS X, and modern Linux) this may block very early in the init
-/// process, if the CSPRNG has not been seeded yet.[1]
-///
-/// [1] See <https://www.python.org/dev/peps/pep-0524/> for a more
-///     in-depth discussion.
-pub struct OsRng(imp::OsRng);
-
-impl OsRng {
-    /// Create a new `OsRng`.
-    pub fn new() -> io::Result<OsRng> {
-        imp::OsRng::new().map(OsRng)
-    }
-}
-
-impl Rng for OsRng {
-    fn next_u32(&mut self) -> u32 { self.0.next_u32() }
-    fn next_u64(&mut self) -> u64 { self.0.next_u64() }
-    fn fill_bytes(&mut self, v: &mut [u8]) { self.0.fill_bytes(v) }
-}
-
-impl fmt::Debug for OsRng {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "OsRng {{}}")
-    }
-}
-
-fn next_u32(fill_buf: &mut FnMut(&mut [u8])) -> u32 {
-    let mut buf: [u8; 4] = [0; 4];
-    fill_buf(&mut buf);
-    unsafe { mem::transmute::<[u8; 4], u32>(buf) }
-}
-
-fn next_u64(fill_buf: &mut FnMut(&mut [u8])) -> u64 {
-    let mut buf: [u8; 8] = [0; 8];
-    fill_buf(&mut buf);
-    unsafe { mem::transmute::<[u8; 8], u64>(buf) }
-}
-
-#[cfg(all(unix, not(target_os = "ios"),
-          not(target_os = "nacl"),
-          not(target_os = "freebsd"),
-          not(target_os = "fuchsia"),
-          not(target_os = "openbsd"),
-          not(target_os = "redox")))]
-mod imp {
-    extern crate libc;
-
-    use super::{next_u32, next_u64};
-    use self::OsRngInner::*;
-
-    use std::io;
-    use std::fs::File;
-    use Rng;
-    use read::ReadRng;
-
-    #[cfg(all(target_os = "linux",
-              any(target_arch = "x86_64",
-                  target_arch = "x86",
-                  target_arch = "arm",
-                  target_arch = "aarch64",
-                  target_arch = "powerpc")))]
-    fn getrandom(buf: &mut [u8]) -> libc::c_long {
-        extern "C" {
-            fn syscall(number: libc::c_long, ...) -> libc::c_long;
-        }
-
-        #[cfg(target_arch = "x86_64")]
-        const NR_GETRANDOM: libc::c_long = 318;
-        #[cfg(target_arch = "x86")]
-        const NR_GETRANDOM: libc::c_long = 355;
-        #[cfg(target_arch = "arm")]
-        const NR_GETRANDOM: libc::c_long = 384;
-        #[cfg(target_arch = "aarch64")]
-        const NR_GETRANDOM: libc::c_long = 278;
-        #[cfg(target_arch = "powerpc")]
-        const NR_GETRANDOM: libc::c_long = 359;
-
-        unsafe {
-            syscall(NR_GETRANDOM, buf.as_mut_ptr(), buf.len(), 0)
-        }
-    }
-
-    #[cfg(not(all(target_os = "linux",
-                  any(target_arch = "x86_64",
-                      target_arch = "x86",
-                      target_arch = "arm",
-                      target_arch = "aarch64",
-                      target_arch = "powerpc"))))]
-    fn getrandom(_buf: &mut [u8]) -> libc::c_long { -1 }
-
-    fn getrandom_fill_bytes(v: &mut [u8]) {
-        let mut read = 0;
-        let len = v.len();
-        while read < len {
-            let result = getrandom(&mut v[read..]);
-            if result == -1 {
-                let err = io::Error::last_os_error();
-                if err.kind() == io::ErrorKind::Interrupted {
-                    continue
-                } else {
-                    panic!("unexpected getrandom error: {}", err);
-                }
-            } else {
-                read += result as usize;
-            }
-        }
-    }
-
-    #[cfg(all(target_os = "linux",
-              any(target_arch = "x86_64",
-                  target_arch = "x86",
-                  target_arch = "arm",
-                  target_arch = "aarch64",
-                  target_arch = "powerpc")))]
-    fn is_getrandom_available() -> bool {
-        use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
-        use std::sync::{Once, ONCE_INIT};
-
-        static CHECKER: Once = ONCE_INIT;
-        static AVAILABLE: AtomicBool = ATOMIC_BOOL_INIT;
-
-        CHECKER.call_once(|| {
-            let mut buf: [u8; 0] = [];
-            let result = getrandom(&mut buf);
-            let available = if result == -1 {
-                let err = io::Error::last_os_error().raw_os_error();
-                err != Some(libc::ENOSYS)
-            } else {
-                true
-            };
-            AVAILABLE.store(available, Ordering::Relaxed);
-        });
-
-        AVAILABLE.load(Ordering::Relaxed)
-    }
-
-    #[cfg(not(all(target_os = "linux",
-                  any(target_arch = "x86_64",
-                      target_arch = "x86",
-                      target_arch = "arm",
-                      target_arch = "aarch64",
-                      target_arch = "powerpc"))))]
-    fn is_getrandom_available() -> bool { false }
-
-    pub struct OsRng {
-        inner: OsRngInner,
-    }
-
-    enum OsRngInner {
-        OsGetrandomRng,
-        OsReadRng(ReadRng<File>),
-    }
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            if is_getrandom_available() {
-                return Ok(OsRng { inner: OsGetrandomRng });
-            }
-
-            let reader = try!(File::open("/dev/urandom"));
-            let reader_rng = ReadRng::new(reader);
-
-            Ok(OsRng { inner: OsReadRng(reader_rng) })
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            match self.inner {
-                OsGetrandomRng => next_u32(&mut getrandom_fill_bytes),
-                OsReadRng(ref mut rng) => rng.next_u32(),
-            }
-        }
-        fn next_u64(&mut self) -> u64 {
-            match self.inner {
-                OsGetrandomRng => next_u64(&mut getrandom_fill_bytes),
-                OsReadRng(ref mut rng) => rng.next_u64(),
-            }
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            match self.inner {
-                OsGetrandomRng => getrandom_fill_bytes(v),
-                OsReadRng(ref mut rng) => rng.fill_bytes(v)
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "ios")]
-mod imp {
-    extern crate libc;
-
-    use super::{next_u32, next_u64};
-
-    use std::io;
-    use Rng;
-    use self::libc::{c_int, size_t};
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    enum SecRandom {}
-
-    #[allow(non_upper_case_globals)]
-    const kSecRandomDefault: *const SecRandom = 0 as *const SecRandom;
-
-    #[link(name = "Security", kind = "framework")]
-    extern {
-        fn SecRandomCopyBytes(rnd: *const SecRandom,
-                              count: size_t, bytes: *mut u8) -> c_int;
-    }
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Ok(OsRng)
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            let ret = unsafe {
-                SecRandomCopyBytes(kSecRandomDefault, v.len() as size_t, v.as_mut_ptr())
-            };
-            if ret == -1 {
-                panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "freebsd")]
-mod imp {
-    extern crate libc;
-
-    use std::{io, ptr};
-    use Rng;
-
-    use super::{next_u32, next_u64};
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Ok(OsRng)
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            let mib = [libc::CTL_KERN, libc::KERN_ARND];
-            // kern.arandom permits a maximum buffer size of 256 bytes
-            for s in v.chunks_mut(256) {
-                let mut s_len = s.len();
-                let ret = unsafe {
-                    libc::sysctl(mib.as_ptr(), mib.len() as libc::c_uint,
-                                 s.as_mut_ptr() as *mut _, &mut s_len,
-                                 ptr::null(), 0)
-                };
-                if ret == -1 || s_len != s.len() {
-                    panic!("kern.arandom sysctl failed! (returned {}, s.len() {}, oldlenp {})",
-                           ret, s.len(), s_len);
-                }
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "openbsd")]
-mod imp {
-    extern crate libc;
-
-    use std::io;
-    use Rng;
-
-    use super::{next_u32, next_u64};
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Ok(OsRng)
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            // getentropy(2) permits a maximum buffer size of 256 bytes
-            for s in v.chunks_mut(256) {
-                let ret = unsafe {
-                    libc::getentropy(s.as_mut_ptr() as *mut libc::c_void, s.len())
-                };
-                if ret == -1 {
-                    let err = io::Error::last_os_error();
-                    panic!("getentropy failed: {}", err);
-                }
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "redox")]
-mod imp {
-    use std::io;
-    use std::fs::File;
-    use Rng;
-    use read::ReadRng;
-
-    #[derive(Debug)]
-    pub struct OsRng {
-        inner: ReadRng<File>,
-    }
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            let reader = try!(File::open("rand:"));
-            let reader_rng = ReadRng::new(reader);
-
-            Ok(OsRng { inner: reader_rng })
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            self.inner.next_u32()
-        }
-        fn next_u64(&mut self) -> u64 {
-            self.inner.next_u64()
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            self.inner.fill_bytes(v)
-        }
-    }
-}
-
-#[cfg(target_os = "fuchsia")]
-mod imp {
-    extern crate fuchsia_zircon;
-
-    use std::io;
-    use Rng;
-
-    use super::{next_u32, next_u64};
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Ok(OsRng)
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            for s in v.chunks_mut(fuchsia_zircon::sys::ZX_CPRNG_DRAW_MAX_LEN) {
-                let mut filled = 0;
-                while filled < s.len() {
-                    match fuchsia_zircon::cprng_draw(&mut s[filled..]) {
-                        Ok(actual) => filled += actual,
-                        Err(e) => panic!("cprng_draw failed: {:?}", e),
-                    };
-                }
-            }
-        }
-    }
-}
-
-#[cfg(windows)]
-mod imp {
-    extern crate winapi;
-
-    use std::io;
-    use Rng;
-
-    use super::{next_u32, next_u64};
-
-    use self::winapi::shared::minwindef::ULONG;
-    use self::winapi::um::ntsecapi::RtlGenRandom;
-    use self::winapi::um::winnt::PVOID;
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Ok(OsRng)
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            // RtlGenRandom takes an ULONG (u32) for the length so we need to
-            // split up the buffer.
-            for slice in v.chunks_mut(<ULONG>::max_value() as usize) {
-                let ret = unsafe {
-                    RtlGenRandom(slice.as_mut_ptr() as PVOID, slice.len() as ULONG)
-                };
-                if ret == 0 {
-                    panic!("couldn't generate random bytes: {}",
-                           io::Error::last_os_error());
-                }
-            }
-        }
-    }
-}
-
-#[cfg(target_os = "nacl")]
-mod imp {
-    extern crate libc;
-
-    use std::io;
-    use std::mem;
-    use Rng;
-
-    use super::{next_u32, next_u64};
-
-    #[derive(Debug)]
-    pub struct OsRng(extern fn(dest: *mut libc::c_void,
-                               bytes: libc::size_t,
-                               read: *mut libc::size_t) -> libc::c_int);
-
-    extern {
-        fn nacl_interface_query(name: *const libc::c_char,
-                                table: *mut libc::c_void,
-                                table_size: libc::size_t) -> libc::size_t;
-    }
-
-    const INTERFACE: &'static [u8] = b"nacl-irt-random-0.1\0";
-
-    #[repr(C)]
-    struct NaClIRTRandom {
-        get_random_bytes: Option<extern fn(dest: *mut libc::c_void,
-                                           bytes: libc::size_t,
-                                           read: *mut libc::size_t) -> libc::c_int>,
-    }
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            let mut iface = NaClIRTRandom {
-                get_random_bytes: None,
-            };
-            let result = unsafe {
-                nacl_interface_query(INTERFACE.as_ptr() as *const _,
-                                     mem::transmute(&mut iface),
-                                     mem::size_of::<NaClIRTRandom>() as libc::size_t)
-            };
-            if result != 0 {
-                assert!(iface.get_random_bytes.is_some());
-                let result = OsRng(iface.get_random_bytes.take().unwrap());
-                Ok(result)
-            } else {
-                let error = io::ErrorKind::NotFound;
-                let error = io::Error::new(error, "IRT random interface missing");
-                Err(error)
-            }
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            next_u32(&mut |v| self.fill_bytes(v))
-        }
-        fn next_u64(&mut self) -> u64 {
-            next_u64(&mut |v| self.fill_bytes(v))
-        }
-        fn fill_bytes(&mut self, v: &mut [u8]) {
-            let mut read = 0;
-            loop {
-                let mut r: libc::size_t = 0;
-                let len = v.len();
-                let error = (self.0)(v[read..].as_mut_ptr() as *mut _,
-                                     (len - read) as libc::size_t,
-                                     &mut r as *mut _);
-                assert!(error == 0, "`get_random_bytes` failed!");
-                read += r as usize;
-
-                if read >= v.len() { break; }
-            }
-        }
-    }
-}
-
-#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
-mod imp {
-    use std::io;
-    use Rng;
-
-    #[derive(Debug)]
-    pub struct OsRng;
-
-    impl OsRng {
-        pub fn new() -> io::Result<OsRng> {
-            Err(io::Error::new(io::ErrorKind::Other, "Not supported"))
-        }
-    }
-
-    impl Rng for OsRng {
-        fn next_u32(&mut self) -> u32 {
-            panic!("Not supported")
-        }
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use std::sync::mpsc::channel;
-    use Rng;
-    use OsRng;
-    use std::thread;
-
-    #[test]
-    fn test_os_rng() {
-        let mut r = OsRng::new().unwrap();
-
-        r.next_u32();
-        r.next_u64();
-
-        let mut v = [0u8; 1000];
-        r.fill_bytes(&mut v);
-    }
-
-    #[test]
-    fn test_os_rng_tasks() {
-
-        let mut txs = vec!();
-        for _ in 0..20 {
-            let (tx, rx) = channel();
-            txs.push(tx);
-
-            thread::spawn(move|| {
-                // wait until all the tasks are ready to go.
-                rx.recv().unwrap();
-
-                // deschedule to attempt to interleave things as much
-                // as possible (XXX: is this a good test?)
-                let mut r = OsRng::new().unwrap();
-                thread::yield_now();
-                let mut v = [0u8; 1000];
-
-                for _ in 0..100 {
-                    r.next_u32();
-                    thread::yield_now();
-                    r.next_u64();
-                    thread::yield_now();
-                    r.fill_bytes(&mut v);
-                    thread::yield_now();
-                }
-            });
-        }
-
-        // start all the tasks
-        for tx in txs.iter() {
-            tx.send(()).unwrap();
-        }
-    }
-}
diff --git a/rand/src/prelude.rs b/rand/src/prelude.rs
new file mode 100644
index 0000000..5d8a0e9
--- /dev/null
+++ b/rand/src/prelude.rs
@@ -0,0 +1,27 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Convenience re-export of common members
+//!
+//! Like the standard library's prelude, this module simplifies importing of
+//! common items. Unlike the standard prelude, the contents of this module must
+//! be imported manually:
+//!
+//! ```
+//! use rand::prelude::*;
+//! # let _ = StdRng::from_entropy();
+//! # let mut r = SmallRng::from_rng(thread_rng()).unwrap();
+//! # let _: f32 = r.gen();
+//! ```
+
+#[doc(no_inline)] pub use distributions::Distribution;
+#[doc(no_inline)] pub use rngs::{SmallRng, StdRng};
+#[doc(no_inline)] #[cfg(feature="std")] pub use rngs::ThreadRng;
+#[doc(no_inline)] pub use {Rng, RngCore, CryptoRng, SeedableRng};
+#[doc(no_inline)] #[cfg(feature="std")] pub use {FromEntropy, random, thread_rng};
+#[doc(no_inline)] pub use seq::{SliceRandom, IteratorRandom};
diff --git a/rand/src/prng/chacha.rs b/rand/src/prng/chacha.rs
deleted file mode 100644
index a73e8e7..0000000
--- a/rand/src/prng/chacha.rs
+++ /dev/null
@@ -1,321 +0,0 @@
-// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! The ChaCha random number generator.
-
-use core::num::Wrapping as w;
-use {Rng, SeedableRng, Rand};
-
-#[allow(bad_style)]
-type w32 = w<u32>;
-
-const KEY_WORDS    : usize =  8; // 8 words for the 256-bit key
-const STATE_WORDS  : usize = 16;
-const CHACHA_ROUNDS: u32 = 20; // Cryptographically secure from 8 upwards as of this writing
-
-/// A random number generator that uses the ChaCha20 algorithm [1].
-///
-/// The ChaCha algorithm is widely accepted as suitable for
-/// cryptographic purposes, but this implementation has not been
-/// verified as such. Prefer a generator like `OsRng` that defers to
-/// the operating system for cases that need high security.
-///
-/// [1]: D. J. Bernstein, [*ChaCha, a variant of
-/// Salsa20*](http://cr.yp.to/chacha.html)
-#[derive(Copy, Clone, Debug)]
-pub struct ChaChaRng {
-    buffer:  [w32; STATE_WORDS], // Internal buffer of output
-    state:   [w32; STATE_WORDS], // Initial state
-    index:   usize,                 // Index into state
-}
-
-static EMPTY: ChaChaRng = ChaChaRng {
-    buffer:  [w(0); STATE_WORDS],
-    state:   [w(0); STATE_WORDS],
-    index:   STATE_WORDS
-};
-
-
-macro_rules! quarter_round{
-    ($a: expr, $b: expr, $c: expr, $d: expr) => {{
-        $a = $a + $b; $d = $d ^ $a; $d = w($d.0.rotate_left(16));
-        $c = $c + $d; $b = $b ^ $c; $b = w($b.0.rotate_left(12));
-        $a = $a + $b; $d = $d ^ $a; $d = w($d.0.rotate_left( 8));
-        $c = $c + $d; $b = $b ^ $c; $b = w($b.0.rotate_left( 7));
-    }}
-}
-
-macro_rules! double_round{
-    ($x: expr) => {{
-        // Column round
-        quarter_round!($x[ 0], $x[ 4], $x[ 8], $x[12]);
-        quarter_round!($x[ 1], $x[ 5], $x[ 9], $x[13]);
-        quarter_round!($x[ 2], $x[ 6], $x[10], $x[14]);
-        quarter_round!($x[ 3], $x[ 7], $x[11], $x[15]);
-        // Diagonal round
-        quarter_round!($x[ 0], $x[ 5], $x[10], $x[15]);
-        quarter_round!($x[ 1], $x[ 6], $x[11], $x[12]);
-        quarter_round!($x[ 2], $x[ 7], $x[ 8], $x[13]);
-        quarter_round!($x[ 3], $x[ 4], $x[ 9], $x[14]);
-    }}
-}
-
-#[inline]
-fn core(output: &mut [w32; STATE_WORDS], input: &[w32; STATE_WORDS]) {
-    *output = *input;
-
-    for _ in 0..CHACHA_ROUNDS / 2 {
-        double_round!(output);
-    }
-
-    for i in 0..STATE_WORDS {
-        output[i] = output[i] + input[i];
-    }
-}
-
-impl ChaChaRng {
-
-    /// Create an ChaCha random number generator using the default
-    /// fixed key of 8 zero words.
-    ///
-    /// # Examples
-    ///
-    /// ```rust
-    /// use rand::{Rng, ChaChaRng};
-    ///
-    /// let mut ra = ChaChaRng::new_unseeded();
-    /// println!("{:?}", ra.next_u32());
-    /// println!("{:?}", ra.next_u32());
-    /// ```
-    ///
-    /// Since this equivalent to a RNG with a fixed seed, repeated executions
-    /// of an unseeded RNG will produce the same result. This code sample will
-    /// consistently produce:
-    ///
-    /// - 2917185654
-    /// - 2419978656
-    pub fn new_unseeded() -> ChaChaRng {
-        let mut rng = EMPTY;
-        rng.init(&[0; KEY_WORDS]);
-        rng
-    }
-
-    /// Sets the internal 128-bit ChaCha counter to
-    /// a user-provided value. This permits jumping
-    /// arbitrarily ahead (or backwards) in the pseudorandom stream.
-    ///
-    /// Since the nonce words are used to extend the counter to 128 bits,
-    /// users wishing to obtain the conventional ChaCha pseudorandom stream
-    /// associated with a particular nonce can call this function with
-    /// arguments `0, desired_nonce`.
-    ///
-    /// # Examples
-    ///
-    /// ```rust
-    /// use rand::{Rng, ChaChaRng};
-    ///
-    /// let mut ra = ChaChaRng::new_unseeded();
-    /// ra.set_counter(0u64, 1234567890u64);
-    /// println!("{:?}", ra.next_u32());
-    /// println!("{:?}", ra.next_u32());
-    /// ```
-    pub fn set_counter(&mut self, counter_low: u64, counter_high: u64) {
-        self.state[12] = w((counter_low >>  0) as u32);
-        self.state[13] = w((counter_low >> 32) as u32);
-        self.state[14] = w((counter_high >>  0) as u32);
-        self.state[15] = w((counter_high >> 32) as u32);
-        self.index = STATE_WORDS; // force recomputation
-    }
-
-    /// Initializes `self.state` with the appropriate key and constants
-    ///
-    /// We deviate slightly from the ChaCha specification regarding
-    /// the nonce, which is used to extend the counter to 128 bits.
-    /// This is provably as strong as the original cipher, though,
-    /// since any distinguishing attack on our variant also works
-    /// against ChaCha with a chosen-nonce. See the XSalsa20 [1]
-    /// security proof for a more involved example of this.
-    ///
-    /// The modified word layout is:
-    /// ```text
-    /// constant constant constant constant
-    /// key      key      key      key
-    /// key      key      key      key
-    /// counter  counter  counter  counter
-    /// ```
-    /// [1]: Daniel J. Bernstein. [*Extending the Salsa20
-    /// nonce.*](http://cr.yp.to/papers.html#xsalsa)
-    fn init(&mut self, key: &[u32; KEY_WORDS]) {
-        self.state[0] = w(0x61707865);
-        self.state[1] = w(0x3320646E);
-        self.state[2] = w(0x79622D32);
-        self.state[3] = w(0x6B206574);
-
-        for i in 0..KEY_WORDS {
-            self.state[4+i] = w(key[i]);
-        }
-
-        self.state[12] = w(0);
-        self.state[13] = w(0);
-        self.state[14] = w(0);
-        self.state[15] = w(0);
-
-        self.index = STATE_WORDS;
-    }
-
-    /// Refill the internal output buffer (`self.buffer`)
-    fn update(&mut self) {
-        core(&mut self.buffer, &self.state);
-        self.index = 0;
-        // update 128-bit counter
-        self.state[12] = self.state[12] + w(1);
-        if self.state[12] != w(0) { return };
-        self.state[13] = self.state[13] + w(1);
-        if self.state[13] != w(0) { return };
-        self.state[14] = self.state[14] + w(1);
-        if self.state[14] != w(0) { return };
-        self.state[15] = self.state[15] + w(1);
-    }
-}
-
-impl Rng for ChaChaRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        if self.index == STATE_WORDS {
-            self.update();
-        }
-
-        let value = self.buffer[self.index % STATE_WORDS];
-        self.index += 1;
-        value.0
-    }
-}
-
-impl<'a> SeedableRng<&'a [u32]> for ChaChaRng {
-
-    fn reseed(&mut self, seed: &'a [u32]) {
-        // reset state
-        self.init(&[0u32; KEY_WORDS]);
-        // set key in place
-        let key = &mut self.state[4 .. 4+KEY_WORDS];
-        for (k, s) in key.iter_mut().zip(seed.iter()) {
-            *k = w(*s);
-        }
-    }
-
-    /// Create a ChaCha generator from a seed,
-    /// obtained from a variable-length u32 array.
-    /// Only up to 8 words are used; if less than 8
-    /// words are used, the remaining are set to zero.
-    fn from_seed(seed: &'a [u32]) -> ChaChaRng {
-        let mut rng = EMPTY;
-        rng.reseed(seed);
-        rng
-    }
-}
-
-impl Rand for ChaChaRng {
-    fn rand<R: Rng>(other: &mut R) -> ChaChaRng {
-        let mut key : [u32; KEY_WORDS] = [0; KEY_WORDS];
-        for word in key.iter_mut() {
-            *word = other.gen();
-        }
-        SeedableRng::from_seed(&key[..])
-    }
-}
-
-
-#[cfg(test)]
-mod test {
-    use {Rng, SeedableRng};
-    use super::ChaChaRng;
-
-    #[test]
-    fn test_rng_rand_seeded() {
-        let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
-        let mut ra: ChaChaRng = SeedableRng::from_seed(&s[..]);
-        let mut rb: ChaChaRng = SeedableRng::from_seed(&s[..]);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_seeded() {
-        let seed : &[_] = &[0,1,2,3,4,5,6,7];
-        let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
-        let mut rb: ChaChaRng = SeedableRng::from_seed(seed);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_reseed() {
-        let s = ::test::rng().gen_iter::<u32>().take(8).collect::<Vec<u32>>();
-        let mut r: ChaChaRng = SeedableRng::from_seed(&s[..]);
-        let string1: String = r.gen_ascii_chars().take(100).collect();
-
-        r.reseed(&s);
-
-        let string2: String = r.gen_ascii_chars().take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
-    #[test]
-    fn test_rng_true_values() {
-        // Test vectors 1 and 2 from
-        // http://tools.ietf.org/html/draft-nir-cfrg-chacha20-poly1305-04
-        let seed : &[_] = &[0u32; 8];
-        let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
-
-        let v = (0..16).map(|_| ra.next_u32()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(0xade0b876, 0x903df1a0, 0xe56a5d40, 0x28bd8653,
-                        0xb819d2bd, 0x1aed8da0, 0xccef36a8, 0xc70d778b,
-                        0x7c5941da, 0x8d485751, 0x3fe02477, 0x374ad8b8,
-                        0xf4b8436a, 0x1ca11815, 0x69b687c3, 0x8665eeb2));
-
-        let v = (0..16).map(|_| ra.next_u32()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(0xbee7079f, 0x7a385155, 0x7c97ba98, 0x0d082d73,
-                        0xa0290fcb, 0x6965e348, 0x3e53c612, 0xed7aee32,
-                        0x7621b729, 0x434ee69c, 0xb03371d5, 0xd539d874,
-                        0x281fed31, 0x45fb0a51, 0x1f0ae1ac, 0x6f4d794b));
-
-
-        let seed : &[_] = &[0,1,2,3,4,5,6,7];
-        let mut ra: ChaChaRng = SeedableRng::from_seed(seed);
-
-        // Store the 17*i-th 32-bit word,
-        // i.e., the i-th word of the i-th 16-word block
-        let mut v : Vec<u32> = Vec::new();
-        for _ in 0..16 {
-            v.push(ra.next_u32());
-            for _ in 0..16 {
-                ra.next_u32();
-            }
-        }
-
-        assert_eq!(v,
-                   vec!(0xf225c81a, 0x6ab1be57, 0x04d42951, 0x70858036,
-                        0x49884684, 0x64efec72, 0x4be2d186, 0x3615b384,
-                        0x11cfa18e, 0xd3c50049, 0x75c775f6, 0x434c6530,
-                        0x2c5bad8f, 0x898881dc, 0x5f1c86d9, 0xc1f8e7f4));
-    }
-
-    #[test]
-    fn test_rng_clone() {
-        let seed : &[_] = &[0u32; 8];
-        let mut rng: ChaChaRng = SeedableRng::from_seed(seed);
-        let mut clone = rng.clone();
-        for _ in 0..16 {
-            assert_eq!(rng.next_u64(), clone.next_u64());
-        }
-    }
-}
diff --git a/rand/src/prng/isaac.rs b/rand/src/prng/isaac.rs
deleted file mode 100644
index cf5eb67..0000000
--- a/rand/src/prng/isaac.rs
+++ /dev/null
@@ -1,328 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! The ISAAC random number generator.
-
-#![allow(non_camel_case_types)]
-
-use core::slice;
-use core::iter::repeat;
-use core::num::Wrapping as w;
-use core::fmt;
-
-use {Rng, SeedableRng, Rand};
-
-#[allow(bad_style)]
-type w32 = w<u32>;
-
-const RAND_SIZE_LEN: usize = 8;
-const RAND_SIZE: u32 = 1 << RAND_SIZE_LEN;
-const RAND_SIZE_USIZE: usize = 1 << RAND_SIZE_LEN;
-
-/// A random number generator that uses the ISAAC algorithm[1].
-///
-/// The ISAAC algorithm is generally accepted as suitable for
-/// cryptographic purposes, but this implementation has not be
-/// verified as such. Prefer a generator like `OsRng` that defers to
-/// the operating system for cases that need high security.
-///
-/// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
-/// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
-#[derive(Copy)]
-pub struct IsaacRng {
-    cnt: u32,
-    rsl: [w32; RAND_SIZE_USIZE],
-    mem: [w32; RAND_SIZE_USIZE],
-    a: w32,
-    b: w32,
-    c: w32,
-}
-
-static EMPTY: IsaacRng = IsaacRng {
-    cnt: 0,
-    rsl: [w(0); RAND_SIZE_USIZE],
-    mem: [w(0); RAND_SIZE_USIZE],
-    a: w(0), b: w(0), c: w(0),
-};
-
-impl IsaacRng {
-
-    /// Create an ISAAC random number generator using the default
-    /// fixed seed.
-    pub fn new_unseeded() -> IsaacRng {
-        let mut rng = EMPTY;
-        rng.init(false);
-        rng
-    }
-
-    /// Initialises `self`. If `use_rsl` is true, then use the current value
-    /// of `rsl` as a seed, otherwise construct one algorithmically (not
-    /// randomly).
-    fn init(&mut self, use_rsl: bool) {
-        let mut a = w(0x9e3779b9);
-        let mut b = a;
-        let mut c = a;
-        let mut d = a;
-        let mut e = a;
-        let mut f = a;
-        let mut g = a;
-        let mut h = a;
-
-        macro_rules! mix {
-            () => {{
-                a=a^(b<<11); d=d+a; b=b+c;
-                b=b^(c>>2);  e=e+b; c=c+d;
-                c=c^(d<<8);  f=f+c; d=d+e;
-                d=d^(e>>16); g=g+d; e=e+f;
-                e=e^(f<<10); h=h+e; f=f+g;
-                f=f^(g>>4);  a=a+f; g=g+h;
-                g=g^(h<<8);  b=b+g; h=h+a;
-                h=h^(a>>9);  c=c+h; a=a+b;
-            }}
-        }
-
-        for _ in 0..4 {
-            mix!();
-        }
-
-        if use_rsl {
-            macro_rules! memloop {
-                ($arr:expr) => {{
-                    for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
-                        a=a+$arr[i  ]; b=b+$arr[i+1];
-                        c=c+$arr[i+2]; d=d+$arr[i+3];
-                        e=e+$arr[i+4]; f=f+$arr[i+5];
-                        g=g+$arr[i+6]; h=h+$arr[i+7];
-                        mix!();
-                        self.mem[i  ]=a; self.mem[i+1]=b;
-                        self.mem[i+2]=c; self.mem[i+3]=d;
-                        self.mem[i+4]=e; self.mem[i+5]=f;
-                        self.mem[i+6]=g; self.mem[i+7]=h;
-                    }
-                }}
-            }
-
-            memloop!(self.rsl);
-            memloop!(self.mem);
-        } else {
-            for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
-                mix!();
-                self.mem[i  ]=a; self.mem[i+1]=b;
-                self.mem[i+2]=c; self.mem[i+3]=d;
-                self.mem[i+4]=e; self.mem[i+5]=f;
-                self.mem[i+6]=g; self.mem[i+7]=h;
-            }
-        }
-
-        self.isaac();
-    }
-
-    /// Refills the output buffer (`self.rsl`)
-    #[inline]
-    fn isaac(&mut self) {
-        self.c = self.c + w(1);
-        // abbreviations
-        let mut a = self.a;
-        let mut b = self.b + self.c;
-
-        const MIDPOINT: usize = RAND_SIZE_USIZE / 2;
-
-        macro_rules! ind {
-            ($x:expr) => ( self.mem[($x >> 2usize).0 as usize & (RAND_SIZE_USIZE - 1)] )
-        }
-
-        let r = [(0, MIDPOINT), (MIDPOINT, 0)];
-        for &(mr_offset, m2_offset) in r.iter() {
-
-            macro_rules! rngstepp {
-                ($j:expr, $shift:expr) => {{
-                    let base = $j;
-                    let mix = a << $shift;
-
-                    let x = self.mem[base  + mr_offset];
-                    a = (a ^ mix) + self.mem[base + m2_offset];
-                    let y = ind!(x) + a + b;
-                    self.mem[base + mr_offset] = y;
-
-                    b = ind!(y >> RAND_SIZE_LEN) + x;
-                    self.rsl[base + mr_offset] = b;
-                }}
-            }
-
-            macro_rules! rngstepn {
-                ($j:expr, $shift:expr) => {{
-                    let base = $j;
-                    let mix = a >> $shift;
-
-                    let x = self.mem[base  + mr_offset];
-                    a = (a ^ mix) + self.mem[base + m2_offset];
-                    let y = ind!(x) + a + b;
-                    self.mem[base + mr_offset] = y;
-
-                    b = ind!(y >> RAND_SIZE_LEN) + x;
-                    self.rsl[base + mr_offset] = b;
-                }}
-            }
-
-            for i in (0..MIDPOINT/4).map(|i| i * 4) {
-                rngstepp!(i + 0, 13);
-                rngstepn!(i + 1, 6);
-                rngstepp!(i + 2, 2);
-                rngstepn!(i + 3, 16);
-            }
-        }
-
-        self.a = a;
-        self.b = b;
-        self.cnt = RAND_SIZE;
-    }
-}
-
-// Cannot be derived because [u32; 256] does not implement Clone
-impl Clone for IsaacRng {
-    fn clone(&self) -> IsaacRng {
-        *self
-    }
-}
-
-impl Rng for IsaacRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        if self.cnt == 0 {
-            // make some more numbers
-            self.isaac();
-        }
-        self.cnt -= 1;
-
-        // self.cnt is at most RAND_SIZE, but that is before the
-        // subtraction above. We want to index without bounds
-        // checking, but this could lead to incorrect code if someone
-        // misrefactors, so we check, sometimes.
-        //
-        // (Changes here should be reflected in Isaac64Rng.next_u64.)
-        debug_assert!(self.cnt < RAND_SIZE);
-
-        // (the % is cheaply telling the optimiser that we're always
-        // in bounds, without unsafe. NB. this is a power of two, so
-        // it optimises to a bitwise mask).
-        self.rsl[(self.cnt % RAND_SIZE) as usize].0
-    }
-}
-
-impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
-    fn reseed(&mut self, seed: &'a [u32]) {
-        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
-        // - 1], 0, 0, ...], to fill rng.rsl.
-        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));
-
-        for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
-            *rsl_elem = w(seed_elem);
-        }
-        self.cnt = 0;
-        self.a = w(0);
-        self.b = w(0);
-        self.c = w(0);
-
-        self.init(true);
-    }
-
-    /// Create an ISAAC random number generator with a seed. This can
-    /// be any length, although the maximum number of elements used is
-    /// 256 and any more will be silently ignored. A generator
-    /// constructed with a given seed will generate the same sequence
-    /// of values as all other generators constructed with that seed.
-    fn from_seed(seed: &'a [u32]) -> IsaacRng {
-        let mut rng = EMPTY;
-        rng.reseed(seed);
-        rng
-    }
-}
-
-impl Rand for IsaacRng {
-    fn rand<R: Rng>(other: &mut R) -> IsaacRng {
-        let mut ret = EMPTY;
-        unsafe {
-            let ptr = ret.rsl.as_mut_ptr() as *mut u8;
-
-            let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_USIZE * 4);
-            other.fill_bytes(slice);
-        }
-        ret.cnt = 0;
-        ret.a = w(0);
-        ret.b = w(0);
-        ret.c = w(0);
-
-        ret.init(true);
-        return ret;
-    }
-}
-
-impl fmt::Debug for IsaacRng {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "IsaacRng {{}}")
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use {Rng, SeedableRng};
-    use super::IsaacRng;
-
-    #[test]
-    fn test_rng_32_rand_seeded() {
-        let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
-        let mut ra: IsaacRng = SeedableRng::from_seed(&s[..]);
-        let mut rb: IsaacRng = SeedableRng::from_seed(&s[..]);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_32_seeded() {
-        let seed: &[_] = &[1, 23, 456, 7890, 12345];
-        let mut ra: IsaacRng = SeedableRng::from_seed(seed);
-        let mut rb: IsaacRng = SeedableRng::from_seed(seed);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_32_reseed() {
-        let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
-        let mut r: IsaacRng = SeedableRng::from_seed(&s[..]);
-        let string1: String = r.gen_ascii_chars().take(100).collect();
-
-        r.reseed(&s[..]);
-
-        let string2: String = r.gen_ascii_chars().take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
-    #[test]
-    fn test_rng_32_true_values() {
-        let seed: &[_] = &[1, 23, 456, 7890, 12345];
-        let mut ra: IsaacRng = SeedableRng::from_seed(seed);
-        // Regression test that isaac is actually using the above vector
-        let v = (0..10).map(|_| ra.next_u32()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(2558573138, 873787463, 263499565, 2103644246, 3595684709,
-                        4203127393, 264982119, 2765226902, 2737944514, 3900253796));
-
-        let seed: &[_] = &[12345, 67890, 54321, 9876];
-        let mut rb: IsaacRng = SeedableRng::from_seed(seed);
-        // skip forward to the 10000th number
-        for _ in 0..10000 { rb.next_u32(); }
-
-        let v = (0..10).map(|_| rb.next_u32()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(3676831399, 3183332890, 2834741178, 3854698763, 2717568474,
-                        1576568959, 3507990155, 179069555, 141456972, 2478885421));
-    }
-}
diff --git a/rand/src/prng/isaac64.rs b/rand/src/prng/isaac64.rs
deleted file mode 100644
index b98e3fe..0000000
--- a/rand/src/prng/isaac64.rs
+++ /dev/null
@@ -1,340 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! The ISAAC-64 random number generator.
-
-use core::slice;
-use core::iter::repeat;
-use core::num::Wrapping as w;
-use core::fmt;
-
-use {Rng, SeedableRng, Rand};
-
-#[allow(bad_style)]
-type w64 = w<u64>;
-
-const RAND_SIZE_64_LEN: usize = 8;
-const RAND_SIZE_64: usize = 1 << RAND_SIZE_64_LEN;
-
-/// A random number generator that uses ISAAC-64[1], the 64-bit
-/// variant of the ISAAC algorithm.
-///
-/// The ISAAC algorithm is generally accepted as suitable for
-/// cryptographic purposes, but this implementation has not be
-/// verified as such. Prefer a generator like `OsRng` that defers to
-/// the operating system for cases that need high security.
-///
-/// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
-/// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
-#[derive(Copy)]
-pub struct Isaac64Rng {
-    cnt: usize,
-    rsl: [w64; RAND_SIZE_64],
-    mem: [w64; RAND_SIZE_64],
-    a: w64,
-    b: w64,
-    c: w64,
-}
-
-static EMPTY_64: Isaac64Rng = Isaac64Rng {
-    cnt: 0,
-    rsl: [w(0); RAND_SIZE_64],
-    mem: [w(0); RAND_SIZE_64],
-    a: w(0), b: w(0), c: w(0),
-};
-
-impl Isaac64Rng {
-    /// Create a 64-bit ISAAC random number generator using the
-    /// default fixed seed.
-    pub fn new_unseeded() -> Isaac64Rng {
-        let mut rng = EMPTY_64;
-        rng.init(false);
-        rng
-    }
-
-    /// Initialises `self`. If `use_rsl` is true, then use the current value
-    /// of `rsl` as a seed, otherwise construct one algorithmically (not
-    /// randomly).
-    fn init(&mut self, use_rsl: bool) {
-        macro_rules! init {
-            ($var:ident) => (
-                let mut $var = w(0x9e3779b97f4a7c13);
-            )
-        }
-        init!(a); init!(b); init!(c); init!(d);
-        init!(e); init!(f); init!(g); init!(h);
-
-        macro_rules! mix {
-            () => {{
-                a=a-e; f=f^(h>>9);  h=h+a;
-                b=b-f; g=g^(a<<9);  a=a+b;
-                c=c-g; h=h^(b>>23); b=b+c;
-                d=d-h; a=a^(c<<15); c=c+d;
-                e=e-a; b=b^(d>>14); d=d+e;
-                f=f-b; c=c^(e<<20); e=e+f;
-                g=g-c; d=d^(f>>17); f=f+g;
-                h=h-d; e=e^(g<<14); g=g+h;
-            }}
-        }
-
-        for _ in 0..4 {
-            mix!();
-        }
-
-        if use_rsl {
-            macro_rules! memloop {
-                ($arr:expr) => {{
-                    for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
-                        a=a+$arr[i  ]; b=b+$arr[i+1];
-                        c=c+$arr[i+2]; d=d+$arr[i+3];
-                        e=e+$arr[i+4]; f=f+$arr[i+5];
-                        g=g+$arr[i+6]; h=h+$arr[i+7];
-                        mix!();
-                        self.mem[i  ]=a; self.mem[i+1]=b;
-                        self.mem[i+2]=c; self.mem[i+3]=d;
-                        self.mem[i+4]=e; self.mem[i+5]=f;
-                        self.mem[i+6]=g; self.mem[i+7]=h;
-                    }
-                }}
-            }
-
-            memloop!(self.rsl);
-            memloop!(self.mem);
-        } else {
-            for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
-                mix!();
-                self.mem[i  ]=a; self.mem[i+1]=b;
-                self.mem[i+2]=c; self.mem[i+3]=d;
-                self.mem[i+4]=e; self.mem[i+5]=f;
-                self.mem[i+6]=g; self.mem[i+7]=h;
-            }
-        }
-
-        self.isaac64();
-    }
-
-    /// Refills the output buffer (`self.rsl`)
-    fn isaac64(&mut self) {
-        self.c = self.c + w(1);
-        // abbreviations
-        let mut a = self.a;
-        let mut b = self.b + self.c;
-        const MIDPOINT: usize =  RAND_SIZE_64 / 2;
-        const MP_VEC: [(usize, usize); 2] = [(0,MIDPOINT), (MIDPOINT, 0)];
-        macro_rules! ind {
-            ($x:expr) => {
-                *self.mem.get_unchecked((($x >> 3usize).0 as usize) & (RAND_SIZE_64 - 1))
-            }
-        }
-
-        for &(mr_offset, m2_offset) in MP_VEC.iter() {
-            for base in (0..MIDPOINT / 4).map(|i| i * 4) {
-
-                macro_rules! rngstepp {
-                    ($j:expr, $shift:expr) => {{
-                        let base = base + $j;
-                        let mix = a ^ (a << $shift);
-                        let mix = if $j == 0 {!mix} else {mix};
-
-                        unsafe {
-                            let x = *self.mem.get_unchecked(base + mr_offset);
-                            a = mix + *self.mem.get_unchecked(base + m2_offset);
-                            let y = ind!(x) + a + b;
-                            *self.mem.get_unchecked_mut(base + mr_offset) = y;
-
-                            b = ind!(y >> RAND_SIZE_64_LEN) + x;
-                            *self.rsl.get_unchecked_mut(base + mr_offset) = b;
-                        }
-                    }}
-                }
-
-                macro_rules! rngstepn {
-                    ($j:expr, $shift:expr) => {{
-                        let base = base + $j;
-                        let mix = a ^ (a >> $shift);
-                        let mix = if $j == 0 {!mix} else {mix};
-
-                        unsafe {
-                            let x = *self.mem.get_unchecked(base + mr_offset);
-                            a = mix + *self.mem.get_unchecked(base + m2_offset);
-                            let y = ind!(x) + a + b;
-                            *self.mem.get_unchecked_mut(base + mr_offset) = y;
-
-                            b = ind!(y >> RAND_SIZE_64_LEN) + x;
-                            *self.rsl.get_unchecked_mut(base + mr_offset) = b;
-                        }
-                    }}
-                }
-
-                rngstepp!(0, 21);
-                rngstepn!(1, 5);
-                rngstepp!(2, 12);
-                rngstepn!(3, 33);
-            }
-        }
-
-        self.a = a;
-        self.b = b;
-        self.cnt = RAND_SIZE_64;
-    }
-}
-
-// Cannot be derived because [u32; 256] does not implement Clone
-impl Clone for Isaac64Rng {
-    fn clone(&self) -> Isaac64Rng {
-        *self
-    }
-}
-
-impl Rng for Isaac64Rng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        self.next_u64() as u32
-    }
-
-    #[inline]
-    fn next_u64(&mut self) -> u64 {
-        if self.cnt == 0 {
-            // make some more numbers
-            self.isaac64();
-        }
-        self.cnt -= 1;
-
-        // See corresponding location in IsaacRng.next_u32 for
-        // explanation.
-        debug_assert!(self.cnt < RAND_SIZE_64);
-        self.rsl[(self.cnt % RAND_SIZE_64) as usize].0
-    }
-}
-
-impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
-    fn reseed(&mut self, seed: &'a [u64]) {
-        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
-        // - 1], 0, 0, ...], to fill rng.rsl.
-        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u64));
-
-        for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
-            *rsl_elem = w(seed_elem);
-        }
-        self.cnt = 0;
-        self.a = w(0);
-        self.b = w(0);
-        self.c = w(0);
-
-        self.init(true);
-    }
-
-    /// Create an ISAAC random number generator with a seed. This can
-    /// be any length, although the maximum number of elements used is
-    /// 256 and any more will be silently ignored. A generator
-    /// constructed with a given seed will generate the same sequence
-    /// of values as all other generators constructed with that seed.
-    fn from_seed(seed: &'a [u64]) -> Isaac64Rng {
-        let mut rng = EMPTY_64;
-        rng.reseed(seed);
-        rng
-    }
-}
-
-impl Rand for Isaac64Rng {
-    fn rand<R: Rng>(other: &mut R) -> Isaac64Rng {
-        let mut ret = EMPTY_64;
-        unsafe {
-            let ptr = ret.rsl.as_mut_ptr() as *mut u8;
-
-            let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_64 * 8);
-            other.fill_bytes(slice);
-        }
-        ret.cnt = 0;
-        ret.a = w(0);
-        ret.b = w(0);
-        ret.c = w(0);
-
-        ret.init(true);
-        return ret;
-    }
-}
-
-impl fmt::Debug for Isaac64Rng {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "Isaac64Rng {{}}")
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use {Rng, SeedableRng};
-    use super::Isaac64Rng;
-
-    #[test]
-    fn test_rng_64_rand_seeded() {
-        let s = ::test::rng().gen_iter::<u64>().take(256).collect::<Vec<u64>>();
-        let mut ra: Isaac64Rng = SeedableRng::from_seed(&s[..]);
-        let mut rb: Isaac64Rng = SeedableRng::from_seed(&s[..]);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_64_seeded() {
-        let seed: &[_] = &[1, 23, 456, 7890, 12345];
-        let mut ra: Isaac64Rng = SeedableRng::from_seed(seed);
-        let mut rb: Isaac64Rng = SeedableRng::from_seed(seed);
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_64_reseed() {
-        let s = ::test::rng().gen_iter::<u64>().take(256).collect::<Vec<u64>>();
-        let mut r: Isaac64Rng = SeedableRng::from_seed(&s[..]);
-        let string1: String = r.gen_ascii_chars().take(100).collect();
-
-        r.reseed(&s[..]);
-
-        let string2: String = r.gen_ascii_chars().take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
-    #[test]
-    fn test_rng_64_true_values() {
-        let seed: &[_] = &[1, 23, 456, 7890, 12345];
-        let mut ra: Isaac64Rng = SeedableRng::from_seed(seed);
-        // Regression test that isaac is actually using the above vector
-        let v = (0..10).map(|_| ra.next_u64()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(547121783600835980, 14377643087320773276, 17351601304698403469,
-                        1238879483818134882, 11952566807690396487, 13970131091560099343,
-                        4469761996653280935, 15552757044682284409, 6860251611068737823,
-                        13722198873481261842));
-
-        let seed: &[_] = &[12345, 67890, 54321, 9876];
-        let mut rb: Isaac64Rng = SeedableRng::from_seed(seed);
-        // skip forward to the 10000th number
-        for _ in 0..10000 { rb.next_u64(); }
-
-        let v = (0..10).map(|_| rb.next_u64()).collect::<Vec<_>>();
-        assert_eq!(v,
-                   vec!(18143823860592706164, 8491801882678285927, 2699425367717515619,
-                        17196852593171130876, 2606123525235546165, 15790932315217671084,
-                        596345674630742204, 9947027391921273664, 11788097613744130851,
-                        10391409374914919106));
-    }
-
-    #[test]
-    fn test_rng_clone() {
-        let seed: &[_] = &[1, 23, 456, 7890, 12345];
-        let mut rng: Isaac64Rng = SeedableRng::from_seed(seed);
-        let mut clone = rng.clone();
-        for _ in 0..16 {
-            assert_eq!(rng.next_u64(), clone.next_u64());
-        }
-    }
-}
diff --git a/rand/src/prng/mod.rs b/rand/src/prng/mod.rs
index ed3e018..3c0d27b 100644
--- a/rand/src/prng/mod.rs
+++ b/rand/src/prng/mod.rs
@@ -1,51 +1,37 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//! Pseudo random number generators are algorithms to produce *apparently
-//! random* numbers deterministically, and usually fairly quickly.
+//! Pseudo-random number generators.
+//!
+//! This module is deprecated:
 //! 
-//! So long as the algorithm is computationally secure, is initialised with
-//! sufficient entropy (i.e. unknown by an attacker), and its internal state is
-//! also protected (unknown to an attacker), the output will also be
-//! *computationally secure*. Computationally Secure Pseudo Random Number
-//! Generators (CSPRNGs) are thus suitable sources of random numbers for
-//! cryptography. There are a couple of gotchas here, however. First, the seed
-//! used for initialisation must be unknown. Usually this should be provided by
-//! the operating system and should usually be secure, however this may not
-//! always be the case (especially soon after startup). Second, user-space
-//! memory may be vulnerable, for example when written to swap space, and after
-//! forking a child process should reinitialise any user-space PRNGs. For this
-//! reason it may be preferable to source random numbers directly from the OS
-//! for cryptographic applications.
-//! 
-//! PRNGs are also widely used for non-cryptographic uses: randomised
-//! algorithms, simulations, games. In these applications it is usually not
-//! important for numbers to be cryptographically *unguessable*, but even
-//! distribution and independence from other samples (from the point of view
-//! of someone unaware of the algorithm used, at least) may still be important.
-//! Good PRNGs should satisfy these properties, but do not take them for
-//! granted; Wikipedia's article on 
-//! [Pseudorandom number generators](https://en.wikipedia.org/wiki/Pseudorandom_number_generator)
-//! provides some background on this topic.
-//! 
-//! Care should be taken when seeding (initialising) PRNGs. Some PRNGs have
-//! short periods for some seeds. If one PRNG is seeded from another using the
-//! same algorithm, it is possible that both will yield the same sequence of
-//! values (with some lag).
-
-mod chacha;
-mod isaac;
-mod isaac64;
-mod xorshift;
+//! -   documentation has moved to
+//!     [The Book](https://rust-random.github.io/book/guide-rngs.html),
+//! -   PRNGs have moved to other `rand_*` crates.
 
-pub use self::chacha::ChaChaRng;
-pub use self::isaac::IsaacRng;
-pub use self::isaac64::Isaac64Rng;
-pub use self::xorshift::XorShiftRng;
+// Deprecations (to be removed in 0.7)
+#[doc(hidden)] #[allow(deprecated)]
+pub use deprecated::XorShiftRng;
+#[doc(hidden)] pub mod isaac {
+    // Note: we miss `IsaacCore` here but probably unimportant.
+    #[allow(deprecated)] pub use deprecated::IsaacRng;
+}
+#[doc(hidden)] pub mod isaac64 {
+    #[allow(deprecated)] pub use deprecated::Isaac64Rng;
+}
+#[doc(hidden)] #[allow(deprecated)] pub use deprecated::{IsaacRng, Isaac64Rng};
+#[doc(hidden)] pub mod chacha {
+    // Note: we miss `ChaChaCore` here but probably unimportant.
+    #[allow(deprecated)] pub use deprecated::ChaChaRng;
+}
+#[doc(hidden)] #[allow(deprecated)] pub use deprecated::ChaChaRng;
+#[doc(hidden)] pub mod hc128 {
+    // Note: we miss `Hc128Core` here but probably unimportant.
+    #[allow(deprecated)] pub use deprecated::Hc128Rng;
+}
+#[doc(hidden)] #[allow(deprecated)] pub use deprecated::Hc128Rng;
diff --git a/rand/src/prng/xorshift.rs b/rand/src/prng/xorshift.rs
deleted file mode 100644
index dd367e9..0000000
--- a/rand/src/prng/xorshift.rs
+++ /dev/null
@@ -1,101 +0,0 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Xorshift generators
-
-use core::num::Wrapping as w;
-use {Rng, SeedableRng, Rand};
-
-/// An Xorshift[1] random number
-/// generator.
-///
-/// The Xorshift algorithm is not suitable for cryptographic purposes
-/// but is very fast. If you do not know for sure that it fits your
-/// requirements, use a more secure one such as `IsaacRng` or `OsRng`.
-///
-/// [1]: Marsaglia, George (July 2003). ["Xorshift
-/// RNGs"](http://www.jstatsoft.org/v08/i14/paper). *Journal of
-/// Statistical Software*. Vol. 8 (Issue 14).
-#[allow(missing_copy_implementations)]
-#[derive(Clone, Debug)]
-pub struct XorShiftRng {
-    x: w<u32>,
-    y: w<u32>,
-    z: w<u32>,
-    w: w<u32>,
-}
-
-impl XorShiftRng {
-    /// Creates a new XorShiftRng instance which is not seeded.
-    ///
-    /// The initial values of this RNG are constants, so all generators created
-    /// by this function will yield the same stream of random numbers. It is
-    /// highly recommended that this is created through `SeedableRng` instead of
-    /// this function
-    pub fn new_unseeded() -> XorShiftRng {
-        XorShiftRng {
-            x: w(0x193a6754),
-            y: w(0xa8a7d469),
-            z: w(0x97830e05),
-            w: w(0x113ba7bb),
-        }
-    }
-}
-
-impl Rng for XorShiftRng {
-    #[inline]
-    fn next_u32(&mut self) -> u32 {
-        let x = self.x;
-        let t = x ^ (x << 11);
-        self.x = self.y;
-        self.y = self.z;
-        self.z = self.w;
-        let w_ = self.w;
-        self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
-        self.w.0
-    }
-}
-
-impl SeedableRng<[u32; 4]> for XorShiftRng {
-    /// Reseed an XorShiftRng. This will panic if `seed` is entirely 0.
-    fn reseed(&mut self, seed: [u32; 4]) {
-        assert!(!seed.iter().all(|&x| x == 0),
-                "XorShiftRng.reseed called with an all zero seed.");
-
-        self.x = w(seed[0]);
-        self.y = w(seed[1]);
-        self.z = w(seed[2]);
-        self.w = w(seed[3]);
-    }
-
-    /// Create a new XorShiftRng. This will panic if `seed` is entirely 0.
-    fn from_seed(seed: [u32; 4]) -> XorShiftRng {
-        assert!(!seed.iter().all(|&x| x == 0),
-                "XorShiftRng::from_seed called with an all zero seed.");
-
-        XorShiftRng {
-            x: w(seed[0]),
-            y: w(seed[1]),
-            z: w(seed[2]),
-            w: w(seed[3]),
-        }
-    }
-}
-
-impl Rand for XorShiftRng {
-    fn rand<R: Rng>(rng: &mut R) -> XorShiftRng {
-        let mut tuple: (u32, u32, u32, u32) = rng.gen();
-        while tuple == (0, 0, 0, 0) {
-            tuple = rng.gen();
-        }
-        let (x, y, z, w_) = tuple;
-        XorShiftRng { x: w(x), y: w(y), z: w(z), w: w(w_) }
-    }
-}
diff --git a/rand/src/rand_impls.rs b/rand/src/rand_impls.rs
deleted file mode 100644
index a865bb6..0000000
--- a/rand/src/rand_impls.rs
+++ /dev/null
@@ -1,299 +0,0 @@
-// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! The implementations of `Rand` for the built-in types.
-
-use core::{char, mem};
-
-use {Rand,Rng};
-
-impl Rand for isize {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> isize {
-        if mem::size_of::<isize>() == 4 {
-            rng.gen::<i32>() as isize
-        } else {
-            rng.gen::<i64>() as isize
-        }
-    }
-}
-
-impl Rand for i8 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> i8 {
-        rng.next_u32() as i8
-    }
-}
-
-impl Rand for i16 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> i16 {
-        rng.next_u32() as i16
-    }
-}
-
-impl Rand for i32 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> i32 {
-        rng.next_u32() as i32
-    }
-}
-
-impl Rand for i64 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> i64 {
-        rng.next_u64() as i64
-    }
-}
-
-#[cfg(feature = "i128_support")]
-impl Rand for i128 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> i128 {
-        rng.gen::<u128>() as i128
-    }
-}
-
-impl Rand for usize {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> usize {
-        if mem::size_of::<usize>() == 4 {
-            rng.gen::<u32>() as usize
-        } else {
-            rng.gen::<u64>() as usize
-        }
-    }
-}
-
-impl Rand for u8 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> u8 {
-        rng.next_u32() as u8
-    }
-}
-
-impl Rand for u16 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> u16 {
-        rng.next_u32() as u16
-    }
-}
-
-impl Rand for u32 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> u32 {
-        rng.next_u32()
-    }
-}
-
-impl Rand for u64 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> u64 {
-        rng.next_u64()
-    }
-}
-
-#[cfg(feature = "i128_support")]
-impl Rand for u128 {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> u128 {
-        ((rng.next_u64() as u128) << 64) | (rng.next_u64() as u128)
-    }
-}
-
-
-macro_rules! float_impls {
-    ($mod_name:ident, $ty:ty, $mantissa_bits:expr, $method_name:ident) => {
-        mod $mod_name {
-            use {Rand, Rng, Open01, Closed01};
-
-            const SCALE: $ty = (1u64 << $mantissa_bits) as $ty;
-
-            impl Rand for $ty {
-                /// Generate a floating point number in the half-open
-                /// interval `[0,1)`.
-                ///
-                /// See `Closed01` for the closed interval `[0,1]`,
-                /// and `Open01` for the open interval `(0,1)`.
-                #[inline]
-                fn rand<R: Rng>(rng: &mut R) -> $ty {
-                    rng.$method_name()
-                }
-            }
-            impl Rand for Open01<$ty> {
-                #[inline]
-                fn rand<R: Rng>(rng: &mut R) -> Open01<$ty> {
-                    // add a small amount (specifically 2 bits below
-                    // the precision of f64/f32 at 1.0), so that small
-                    // numbers are larger than 0, but large numbers
-                    // aren't pushed to/above 1.
-                    Open01(rng.$method_name() + 0.25 / SCALE)
-                }
-            }
-            impl Rand for Closed01<$ty> {
-                #[inline]
-                fn rand<R: Rng>(rng: &mut R) -> Closed01<$ty> {
-                    // rescale so that 1.0 - epsilon becomes 1.0
-                    // precisely.
-                    Closed01(rng.$method_name() * SCALE / (SCALE - 1.0))
-                }
-            }
-        }
-    }
-}
-float_impls! { f64_rand_impls, f64, 53, next_f64 }
-float_impls! { f32_rand_impls, f32, 24, next_f32 }
-
-impl Rand for char {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> char {
-        // a char is 21 bits
-        const CHAR_MASK: u32 = 0x001f_ffff;
-        loop {
-            // Rejection sampling. About 0.2% of numbers with at most
-            // 21-bits are invalid codepoints (surrogates), so this
-            // will succeed first go almost every time.
-            match char::from_u32(rng.next_u32() & CHAR_MASK) {
-                Some(c) => return c,
-                None => {}
-            }
-        }
-    }
-}
-
-impl Rand for bool {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> bool {
-        rng.gen::<u8>() & 1 == 1
-    }
-}
-
-macro_rules! tuple_impl {
-    // use variables to indicate the arity of the tuple
-    ($($tyvar:ident),* ) => {
-        // the trailing commas are for the 1 tuple
-        impl<
-            $( $tyvar : Rand ),*
-            > Rand for ( $( $tyvar ),* , ) {
-
-            #[inline]
-            fn rand<R: Rng>(_rng: &mut R) -> ( $( $tyvar ),* , ) {
-                (
-                    // use the $tyvar's to get the appropriate number of
-                    // repeats (they're not actually needed)
-                    $(
-                        _rng.gen::<$tyvar>()
-                    ),*
-                    ,
-                )
-            }
-        }
-    }
-}
-
-impl Rand for () {
-    #[inline]
-    fn rand<R: Rng>(_: &mut R) -> () { () }
-}
-tuple_impl!{A}
-tuple_impl!{A, B}
-tuple_impl!{A, B, C}
-tuple_impl!{A, B, C, D}
-tuple_impl!{A, B, C, D, E}
-tuple_impl!{A, B, C, D, E, F}
-tuple_impl!{A, B, C, D, E, F, G}
-tuple_impl!{A, B, C, D, E, F, G, H}
-tuple_impl!{A, B, C, D, E, F, G, H, I}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J, K}
-tuple_impl!{A, B, C, D, E, F, G, H, I, J, K, L}
-
-macro_rules! array_impl {
-    {$n:expr, $t:ident, $($ts:ident,)*} => {
-        array_impl!{($n - 1), $($ts,)*}
-
-        impl<T> Rand for [T; $n] where T: Rand {
-            #[inline]
-            fn rand<R: Rng>(_rng: &mut R) -> [T; $n] {
-                [_rng.gen::<$t>(), $(_rng.gen::<$ts>()),*]
-            }
-        }
-    };
-    {$n:expr,} => {
-        impl<T> Rand for [T; $n] {
-            fn rand<R: Rng>(_rng: &mut R) -> [T; $n] { [] }
-        }
-    };
-}
-
-array_impl!{32, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,}
-
-impl<T:Rand> Rand for Option<T> {
-    #[inline]
-    fn rand<R: Rng>(rng: &mut R) -> Option<T> {
-        if rng.gen() {
-            Some(rng.gen())
-        } else {
-            None
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use {Rng, thread_rng, Open01, Closed01};
-
-    struct ConstantRng(u64);
-    impl Rng for ConstantRng {
-        fn next_u32(&mut self) -> u32 {
-            let ConstantRng(v) = *self;
-            v as u32
-        }
-        fn next_u64(&mut self) -> u64 {
-            let ConstantRng(v) = *self;
-            v
-        }
-    }
-
-    #[test]
-    fn floating_point_edge_cases() {
-        // the test for exact equality is correct here.
-        assert!(ConstantRng(0xffff_ffff).gen::<f32>() != 1.0);
-        assert!(ConstantRng(0xffff_ffff_ffff_ffff).gen::<f64>() != 1.0);
-    }
-
-    #[test]
-    fn rand_open() {
-        // this is unlikely to catch an incorrect implementation that
-        // generates exactly 0 or 1, but it keeps it sane.
-        let mut rng = thread_rng();
-        for _ in 0..1_000 {
-            // strict inequalities
-            let Open01(f) = rng.gen::<Open01<f64>>();
-            assert!(0.0 < f && f < 1.0);
-
-            let Open01(f) = rng.gen::<Open01<f32>>();
-            assert!(0.0 < f && f < 1.0);
-        }
-    }
-
-    #[test]
-    fn rand_closed() {
-        let mut rng = thread_rng();
-        for _ in 0..1_000 {
-            // strict inequalities
-            let Closed01(f) = rng.gen::<Closed01<f64>>();
-            assert!(0.0 <= f && f <= 1.0);
-
-            let Closed01(f) = rng.gen::<Closed01<f32>>();
-            assert!(0.0 <= f && f <= 1.0);
-        }
-    }
-}
diff --git a/rand/src/read.rs b/rand/src/read.rs
deleted file mode 100644
index c7351b7..0000000
--- a/rand/src/read.rs
+++ /dev/null
@@ -1,123 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! A wrapper around any Read to treat it as an RNG.
-
-use std::io::{self, Read};
-use std::mem;
-use Rng;
-
-/// An RNG that reads random bytes straight from a `Read`. This will
-/// work best with an infinite reader, but this is not required.
-///
-/// # Panics
-///
-/// It will panic if it there is insufficient data to fulfill a request.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{read, Rng};
-///
-/// let data = vec![1, 2, 3, 4, 5, 6, 7, 8];
-/// let mut rng = read::ReadRng::new(&data[..]);
-/// println!("{:x}", rng.gen::<u32>());
-/// ```
-#[derive(Debug)]
-pub struct ReadRng<R> {
-    reader: R
-}
-
-impl<R: Read> ReadRng<R> {
-    /// Create a new `ReadRng` from a `Read`.
-    pub fn new(r: R) -> ReadRng<R> {
-        ReadRng {
-            reader: r
-        }
-    }
-}
-
-impl<R: Read> Rng for ReadRng<R> {
-    fn next_u32(&mut self) -> u32 {
-        // This is designed for speed: reading a LE integer on a LE
-        // platform just involves blitting the bytes into the memory
-        // of the u32, similarly for BE on BE; avoiding byteswapping.
-        let mut buf = [0; 4];
-        fill(&mut self.reader, &mut buf).unwrap();
-        unsafe { *(buf.as_ptr() as *const u32) }
-    }
-    fn next_u64(&mut self) -> u64 {
-        // see above for explanation.
-        let mut buf = [0; 8];
-        fill(&mut self.reader, &mut buf).unwrap();
-        unsafe { *(buf.as_ptr() as *const u64) }
-    }
-    fn fill_bytes(&mut self, v: &mut [u8]) {
-        if v.len() == 0 { return }
-        fill(&mut self.reader, v).unwrap();
-    }
-}
-
-fn fill(r: &mut Read, mut buf: &mut [u8]) -> io::Result<()> {
-    while buf.len() > 0 {
-        match try!(r.read(buf)) {
-            0 => return Err(io::Error::new(io::ErrorKind::Other,
-                                           "end of file reached")),
-            n => buf = &mut mem::replace(&mut buf, &mut [])[n..],
-        }
-    }
-    Ok(())
-}
-
-#[cfg(test)]
-mod test {
-    use super::ReadRng;
-    use Rng;
-
-    #[test]
-    fn test_reader_rng_u64() {
-        // transmute from the target to avoid endianness concerns.
-        let v = vec![0u8, 0, 0, 0, 0, 0, 0, 1,
-                     0  , 0, 0, 0, 0, 0, 0, 2,
-                     0,   0, 0, 0, 0, 0, 0, 3];
-        let mut rng = ReadRng::new(&v[..]);
-
-        assert_eq!(rng.next_u64(), 1_u64.to_be());
-        assert_eq!(rng.next_u64(), 2_u64.to_be());
-        assert_eq!(rng.next_u64(), 3_u64.to_be());
-    }
-    #[test]
-    fn test_reader_rng_u32() {
-        let v = vec![0u8, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3];
-        let mut rng = ReadRng::new(&v[..]);
-
-        assert_eq!(rng.next_u32(), 1_u32.to_be());
-        assert_eq!(rng.next_u32(), 2_u32.to_be());
-        assert_eq!(rng.next_u32(), 3_u32.to_be());
-    }
-    #[test]
-    fn test_reader_rng_fill_bytes() {
-        let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
-        let mut w = [0u8; 8];
-
-        let mut rng = ReadRng::new(&v[..]);
-        rng.fill_bytes(&mut w);
-
-        assert!(v == w);
-    }
-
-    #[test]
-    #[should_panic]
-    fn test_reader_rng_insufficient_bytes() {
-        let mut rng = ReadRng::new(&[][..]);
-        let mut v = [0u8; 3];
-        rng.fill_bytes(&mut v);
-    }
-}
diff --git a/rand/src/reseeding.rs b/rand/src/reseeding.rs
deleted file mode 100644
index 1f24e20..0000000
--- a/rand/src/reseeding.rs
+++ /dev/null
@@ -1,229 +0,0 @@
-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! A wrapper around another RNG that reseeds it after it
-//! generates a certain number of random bytes.
-
-use core::default::Default;
-
-use {Rng, SeedableRng};
-
-/// How many bytes of entropy the underling RNG is allowed to generate
-/// before it is reseeded
-const DEFAULT_GENERATION_THRESHOLD: u64 = 32 * 1024;
-
-/// A wrapper around any RNG which reseeds the underlying RNG after it
-/// has generated a certain number of random bytes.
-#[derive(Debug)]
-pub struct ReseedingRng<R, Rsdr> {
-    rng: R,
-    generation_threshold: u64,
-    bytes_generated: u64,
-    /// Controls the behaviour when reseeding the RNG.
-    pub reseeder: Rsdr,
-}
-
-impl<R: Rng, Rsdr: Reseeder<R>> ReseedingRng<R, Rsdr> {
-    /// Create a new `ReseedingRng` with the given parameters.
-    ///
-    /// # Arguments
-    ///
-    /// * `rng`: the random number generator to use.
-    /// * `generation_threshold`: the number of bytes of entropy at which to reseed the RNG.
-    /// * `reseeder`: the reseeding object to use.
-    pub fn new(rng: R, generation_threshold: u64, reseeder: Rsdr) -> ReseedingRng<R,Rsdr> {
-        ReseedingRng {
-            rng: rng,
-            generation_threshold: generation_threshold,
-            bytes_generated: 0,
-            reseeder: reseeder
-        }
-    }
-
-    /// Reseed the internal RNG if the number of bytes that have been
-    /// generated exceed the threshold.
-    pub fn reseed_if_necessary(&mut self) {
-        if self.bytes_generated >= self.generation_threshold {
-            self.reseeder.reseed(&mut self.rng);
-            self.bytes_generated = 0;
-        }
-    }
-}
-
-
-impl<R: Rng, Rsdr: Reseeder<R>> Rng for ReseedingRng<R, Rsdr> {
-    fn next_u32(&mut self) -> u32 {
-        self.reseed_if_necessary();
-        self.bytes_generated += 4;
-        self.rng.next_u32()
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        self.reseed_if_necessary();
-        self.bytes_generated += 8;
-        self.rng.next_u64()
-    }
-
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        self.reseed_if_necessary();
-        self.bytes_generated += dest.len() as u64;
-        self.rng.fill_bytes(dest)
-    }
-}
-
-impl<S, R: SeedableRng<S>, Rsdr: Reseeder<R> + Default>
-     SeedableRng<(Rsdr, S)> for ReseedingRng<R, Rsdr> {
-    fn reseed(&mut self, (rsdr, seed): (Rsdr, S)) {
-        self.rng.reseed(seed);
-        self.reseeder = rsdr;
-        self.bytes_generated = 0;
-    }
-
-    /// Create a new `ReseedingRng` from the given reseeder and
-    /// seed. This uses a default value for `generation_threshold`.
-    fn from_seed((rsdr, seed): (Rsdr, S)) -> ReseedingRng<R, Rsdr> {
-        ReseedingRng {
-            rng: SeedableRng::from_seed(seed),
-            generation_threshold: DEFAULT_GENERATION_THRESHOLD,
-            bytes_generated: 0,
-            reseeder: rsdr
-        }
-    }
-}
-
-/// Something that can be used to reseed an RNG via `ReseedingRng`.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{Rng, SeedableRng, StdRng};
-/// use rand::reseeding::{Reseeder, ReseedingRng};
-///
-/// struct TickTockReseeder { tick: bool }
-/// impl Reseeder<StdRng> for TickTockReseeder {
-///     fn reseed(&mut self, rng: &mut StdRng) {
-///         let val = if self.tick {0} else {1};
-///         rng.reseed(&[val]);
-///         self.tick = !self.tick;
-///     }
-/// }
-/// fn main() {
-///     let rsdr = TickTockReseeder { tick: true };
-///
-///     let inner = StdRng::new().unwrap();
-///     let mut rng = ReseedingRng::new(inner, 10, rsdr);
-///
-///     // this will repeat, because it gets reseeded very regularly.
-///     let s: String = rng.gen_ascii_chars().take(100).collect();
-///     println!("{}", s);
-/// }
-///
-/// ```
-pub trait Reseeder<R> {
-    /// Reseed the given RNG.
-    fn reseed(&mut self, rng: &mut R);
-}
-
-/// Reseed an RNG using a `Default` instance. This reseeds by
-/// replacing the RNG with the result of a `Default::default` call.
-#[derive(Clone, Copy, Debug)]
-pub struct ReseedWithDefault;
-
-impl<R: Rng + Default> Reseeder<R> for ReseedWithDefault {
-    fn reseed(&mut self, rng: &mut R) {
-        *rng = Default::default();
-    }
-}
-impl Default for ReseedWithDefault {
-    fn default() -> ReseedWithDefault { ReseedWithDefault }
-}
-
-#[cfg(test)]
-mod test {
-    use std::default::Default;
-    use std::iter::repeat;
-    use super::{ReseedingRng, ReseedWithDefault};
-    use {SeedableRng, Rng};
-
-    struct Counter {
-        i: u32
-    }
-
-    impl Rng for Counter {
-        fn next_u32(&mut self) -> u32 {
-            self.i += 1;
-            // very random
-            self.i - 1
-        }
-    }
-    impl Default for Counter {
-        fn default() -> Counter {
-            Counter { i: 0 }
-        }
-    }
-    impl SeedableRng<u32> for Counter {
-        fn reseed(&mut self, seed: u32) {
-            self.i = seed;
-        }
-        fn from_seed(seed: u32) -> Counter {
-            Counter { i: seed }
-        }
-    }
-    type MyRng = ReseedingRng<Counter, ReseedWithDefault>;
-
-    #[test]
-    fn test_reseeding() {
-        let mut rs = ReseedingRng::new(Counter {i:0}, 400, ReseedWithDefault);
-
-        let mut i = 0;
-        for _ in 0..1000 {
-            assert_eq!(rs.next_u32(), i % 100);
-            i += 1;
-        }
-    }
-
-    #[test]
-    fn test_rng_seeded() {
-        let mut ra: MyRng = SeedableRng::from_seed((ReseedWithDefault, 2));
-        let mut rb: MyRng = SeedableRng::from_seed((ReseedWithDefault, 2));
-        assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
-                                rb.gen_ascii_chars().take(100)));
-    }
-
-    #[test]
-    fn test_rng_reseed() {
-        let mut r: MyRng = SeedableRng::from_seed((ReseedWithDefault, 3));
-        let string1: String = r.gen_ascii_chars().take(100).collect();
-
-        r.reseed((ReseedWithDefault, 3));
-
-        let string2: String = r.gen_ascii_chars().take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
-    const FILL_BYTES_V_LEN: usize = 13579;
-    #[test]
-    fn test_rng_fill_bytes() {
-        let mut v = repeat(0u8).take(FILL_BYTES_V_LEN).collect::<Vec<_>>();
-        ::test::rng().fill_bytes(&mut v);
-
-        // Sanity test: if we've gotten here, `fill_bytes` has not infinitely
-        // recursed.
-        assert_eq!(v.len(), FILL_BYTES_V_LEN);
-
-        // To test that `fill_bytes` actually did something, check that the
-        // average of `v` is not 0.
-        let mut sum = 0.0;
-        for &x in v.iter() {
-            sum += x as f64;
-        }
-        assert!(sum / v.len() as f64 != 0.0);
-    }
-}
diff --git a/rand/src/rngs/adapter/mod.rs b/rand/src/rngs/adapter/mod.rs
new file mode 100644
index 0000000..60b832e
--- /dev/null
+++ b/rand/src/rngs/adapter/mod.rs
@@ -0,0 +1,15 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Wrappers / adapters forming RNGs
+
+#[cfg(feature="std")] #[doc(hidden)] pub mod read;
+mod reseeding;
+
+#[cfg(feature="std")] pub use self::read::ReadRng;
+pub use self::reseeding::ReseedingRng;
diff --git a/rand/src/rngs/adapter/read.rs b/rand/src/rngs/adapter/read.rs
new file mode 100644
index 0000000..30b6de6
--- /dev/null
+++ b/rand/src/rngs/adapter/read.rs
@@ -0,0 +1,137 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A wrapper around any Read to treat it as an RNG.
+
+use std::io::Read;
+
+use rand_core::{RngCore, Error, ErrorKind, impls};
+
+
+/// An RNG that reads random bytes straight from any type supporting
+/// `std::io::Read`, for example files.
+///
+/// This will work best with an infinite reader, but that is not required.
+///
+/// This can be used with `/dev/urandom` on Unix but it is recommended to use
+/// [`OsRng`] instead.
+///
+/// # Panics
+///
+/// `ReadRng` uses `std::io::read_exact`, which retries on interrupts. All other
+/// errors from the underlying reader, including when it does not have enough
+/// data, will only be reported through [`try_fill_bytes`]. The other
+/// [`RngCore`] methods will panic in case of an error.
+///
+/// # Example
+///
+/// ```
+/// use rand::Rng;
+/// use rand::rngs::adapter::ReadRng;
+///
+/// let data = vec![1, 2, 3, 4, 5, 6, 7, 8];
+/// let mut rng = ReadRng::new(&data[..]);
+/// println!("{:x}", rng.gen::<u32>());
+/// ```
+///
+/// [`OsRng`]: ../struct.OsRng.html
+/// [`RngCore`]: ../../trait.RngCore.html
+/// [`try_fill_bytes`]: ../../trait.RngCore.html#method.tymethod.try_fill_bytes
+#[derive(Debug)]
+pub struct ReadRng<R> {
+    reader: R
+}
+
+impl<R: Read> ReadRng<R> {
+    /// Create a new `ReadRng` from a `Read`.
+    pub fn new(r: R) -> ReadRng<R> {
+        ReadRng {
+            reader: r
+        }
+    }
+}
+
+impl<R: Read> RngCore for ReadRng<R> {
+    fn next_u32(&mut self) -> u32 {
+        impls::next_u32_via_fill(self)
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_fill(self)
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.try_fill_bytes(dest).unwrap_or_else(|err|
+                panic!("reading random bytes from Read implementation failed; error: {}", err));
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        if dest.len() == 0 { return Ok(()); }
+        // Use `std::io::read_exact`, which retries on `ErrorKind::Interrupted`.
+        self.reader.read_exact(dest).map_err(|err| {
+            match err.kind() {
+                ::std::io::ErrorKind::UnexpectedEof => Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "not enough bytes available, reached end of source", err),
+                _ => Error::with_cause(ErrorKind::Unavailable,
+                    "error reading from Read source", err)
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::ReadRng;
+    use {RngCore, ErrorKind};
+
+    #[test]
+    fn test_reader_rng_u64() {
+        // transmute from the target to avoid endianness concerns.
+        let v = vec![0u8, 0, 0, 0, 0, 0, 0, 1,
+                     0  , 0, 0, 0, 0, 0, 0, 2,
+                     0,   0, 0, 0, 0, 0, 0, 3];
+        let mut rng = ReadRng::new(&v[..]);
+
+        assert_eq!(rng.next_u64(), 1_u64.to_be());
+        assert_eq!(rng.next_u64(), 2_u64.to_be());
+        assert_eq!(rng.next_u64(), 3_u64.to_be());
+    }
+
+    #[test]
+    fn test_reader_rng_u32() {
+        let v = vec![0u8, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3];
+        let mut rng = ReadRng::new(&v[..]);
+
+        assert_eq!(rng.next_u32(), 1_u32.to_be());
+        assert_eq!(rng.next_u32(), 2_u32.to_be());
+        assert_eq!(rng.next_u32(), 3_u32.to_be());
+    }
+
+    #[test]
+    fn test_reader_rng_fill_bytes() {
+        let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
+        let mut w = [0u8; 8];
+
+        let mut rng = ReadRng::new(&v[..]);
+        rng.fill_bytes(&mut w);
+
+        assert!(v == w);
+    }
+
+    #[test]
+    fn test_reader_rng_insufficient_bytes() {
+        let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
+        let mut w = [0u8; 9];
+
+        let mut rng = ReadRng::new(&v[..]);
+
+        assert!(rng.try_fill_bytes(&mut w).err().unwrap().kind == ErrorKind::Unavailable);
+    }
+}
diff --git a/rand/src/rngs/adapter/reseeding.rs b/rand/src/rngs/adapter/reseeding.rs
new file mode 100644
index 0000000..016afab
--- /dev/null
+++ b/rand/src/rngs/adapter/reseeding.rs
@@ -0,0 +1,370 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A wrapper around another PRNG that reseeds it after it
+//! generates a certain number of random bytes.
+
+use core::mem::size_of;
+
+use rand_core::{RngCore, CryptoRng, SeedableRng, Error, ErrorKind};
+use rand_core::block::{BlockRngCore, BlockRng};
+
+/// A wrapper around any PRNG that implements [`BlockRngCore`], that adds the
+/// ability to reseed it.
+///
+/// `ReseedingRng` reseeds the underlying PRNG in the following cases:
+///
+/// - On a manual call to [`reseed()`].
+/// - After `clone()`, the clone will be reseeded on first use.
+/// - After a process is forked, the RNG in the child process is reseeded within
+///   the next few generated values, depending on the block size of the
+///   underlying PRNG. For [`ChaChaCore`] and [`Hc128Core`] this is a maximum of
+///   15 `u32` values before reseeding.
+/// - After the PRNG has generated a configurable number of random bytes.
+///
+/// # When should reseeding after a fixed number of generated bytes be used?
+///
+/// Reseeding after a fixed number of generated bytes is never strictly
+/// *necessary*. Cryptographic PRNGs don't have a limited number of bytes they
+/// can output, or at least not a limit reachable in any practical way. There is
+/// no such thing as 'running out of entropy'.
+///
+/// Occasionally reseeding can be seen as some form of 'security in depth'. Even
+/// if in the future a cryptographic weakness is found in the CSPRNG being used,
+/// or a flaw in the implementation, occasionally reseeding should make
+/// exploiting it much more difficult or even impossible.
+///
+/// Use [`ReseedingRng::new`] with a `threshold` of `0` to disable reseeding
+/// after a fixed number of generated bytes.
+///
+/// # Error handling
+///
+/// Although unlikely, reseeding the wrapped PRNG can fail. `ReseedingRng` will
+/// never panic but try to handle the error intelligently through some
+/// combination of retrying and delaying reseeding until later.
+/// If handling the source error fails `ReseedingRng` will continue generating
+/// data from the wrapped PRNG without reseeding.
+///
+/// Manually calling [`reseed()`] will not have this retry or delay logic, but
+/// reports the error.
+///
+/// # Example
+///
+/// ```
+/// # extern crate rand;
+/// # extern crate rand_chacha;
+/// # fn main() {
+/// use rand::prelude::*;
+/// use rand_chacha::ChaChaCore; // Internal part of ChaChaRng that
+///                              // implements BlockRngCore
+/// use rand::rngs::OsRng;
+/// use rand::rngs::adapter::ReseedingRng;
+///
+/// let prng = ChaChaCore::from_entropy();
+// FIXME: it is better to use EntropyRng as reseeder, but that doesn't implement
+// clone yet.
+/// let reseeder = OsRng::new().unwrap();
+/// let mut reseeding_rng = ReseedingRng::new(prng, 0, reseeder);
+///
+/// println!("{}", reseeding_rng.gen::<u64>());
+///
+/// let mut cloned_rng = reseeding_rng.clone();
+/// assert!(reseeding_rng.gen::<u64>() != cloned_rng.gen::<u64>());
+/// # }
+/// ```
+///
+/// [`ChaChaCore`]: ../../../rand_chacha/struct.ChaChaCore.html
+/// [`Hc128Core`]: ../../../rand_hc/struct.Hc128Core.html
+/// [`BlockRngCore`]: ../../../rand_core/block/trait.BlockRngCore.html
+/// [`ReseedingRng::new`]: struct.ReseedingRng.html#method.new
+/// [`reseed()`]: struct.ReseedingRng.html#method.reseed
+#[derive(Debug)]
+pub struct ReseedingRng<R, Rsdr>(BlockRng<ReseedingCore<R, Rsdr>>)
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore;
+
+impl<R, Rsdr> ReseedingRng<R, Rsdr>
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore
+{
+    /// Create a new `ReseedingRng` from an existing PRNG, combined with a RNG
+    /// to use as reseeder.
+    ///
+    /// `threshold` sets the number of generated bytes after which to reseed the
+    /// PRNG. Set it to zero to never reseed based on the number of generated
+    /// values.
+    pub fn new(rng: R, threshold: u64, reseeder: Rsdr) -> Self {
+        ReseedingRng(BlockRng::new(ReseedingCore::new(rng, threshold, reseeder)))
+    }
+
+    /// Reseed the internal PRNG.
+    pub fn reseed(&mut self) -> Result<(), Error> {
+        self.0.core.reseed()
+    }
+}
+
+// TODO: this should be implemented for any type where the inner type
+// implements RngCore, but we can't specify that because ReseedingCore is private
+impl<R, Rsdr: RngCore> RngCore for ReseedingRng<R, Rsdr>
+where R: BlockRngCore<Item = u32> + SeedableRng,
+    <R as BlockRngCore>::Results: AsRef<[u32]> + AsMut<[u32]>
+{
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl<R, Rsdr> Clone for ReseedingRng<R, Rsdr>
+where R: BlockRngCore + SeedableRng + Clone,
+      Rsdr: RngCore + Clone
+{
+    fn clone(&self) -> ReseedingRng<R, Rsdr> {
+        // Recreating `BlockRng` seems easier than cloning it and resetting
+        // the index.
+        ReseedingRng(BlockRng::new(self.0.core.clone()))
+    }
+}
+
+impl<R, Rsdr> CryptoRng for ReseedingRng<R, Rsdr>
+where R: BlockRngCore + SeedableRng + CryptoRng,
+      Rsdr: RngCore + CryptoRng {}
+
+#[derive(Debug)]
+struct ReseedingCore<R, Rsdr> {
+    inner: R,
+    reseeder: Rsdr,
+    threshold: i64,
+    bytes_until_reseed: i64,
+    fork_counter: usize,
+}
+
+impl<R, Rsdr> BlockRngCore for ReseedingCore<R, Rsdr>
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore
+{
+    type Item = <R as BlockRngCore>::Item;
+    type Results = <R as BlockRngCore>::Results;
+
+    fn generate(&mut self, results: &mut Self::Results) {
+        let global_fork_counter = fork::get_fork_counter();
+        if self.bytes_until_reseed <= 0 ||
+           self.is_forked(global_fork_counter) {
+            // We get better performance by not calling only `reseed` here
+            // and continuing with the rest of the function, but by directly
+            // returning from a non-inlined function.
+            return self.reseed_and_generate(results, global_fork_counter);
+        }
+        let num_bytes = results.as_ref().len() * size_of::<Self::Item>();
+        self.bytes_until_reseed -= num_bytes as i64;
+        self.inner.generate(results);
+    }
+}
+
+impl<R, Rsdr> ReseedingCore<R, Rsdr>
+where R: BlockRngCore + SeedableRng,
+      Rsdr: RngCore
+{
+    /// Create a new `ReseedingCore`.
+    fn new(rng: R, threshold: u64, reseeder: Rsdr) -> Self {
+        use ::core::i64::MAX;
+        fork::register_fork_handler();
+
+        // Because generating more values than `i64::MAX` takes centuries on
+        // current hardware, we just clamp to that value.
+        // Also we set a threshold of 0, which indicates no limit, to that
+        // value.
+        let threshold =
+            if threshold == 0 { MAX }
+            else if threshold <= MAX as u64 { threshold as i64 }
+            else { MAX };
+
+        ReseedingCore {
+            inner: rng,
+            reseeder,
+            threshold: threshold as i64,
+            bytes_until_reseed: threshold as i64,
+            fork_counter: 0,
+        }
+    }
+
+    /// Reseed the internal PRNG.
+    fn reseed(&mut self) -> Result<(), Error> {
+        R::from_rng(&mut self.reseeder).map(|result| {
+            self.bytes_until_reseed = self.threshold;
+            self.inner = result
+        })
+    }
+
+    fn is_forked(&self, global_fork_counter: usize) -> bool {
+        // In theory, on 32-bit platforms, it is possible for
+        // `global_fork_counter` to wrap around after ~4e9 forks.
+        //
+        // This check will detect a fork in the normal case where
+        // `fork_counter < global_fork_counter`, and also when the difference
+        // between both is greater than `isize::MAX` (wrapped around).
+        //
+        // It will still fail to detect a fork if there have been more than
+        // `isize::MAX` forks, without any reseed in between. Seems unlikely
+        // enough.
+        (self.fork_counter.wrapping_sub(global_fork_counter) as isize) < 0
+    }
+
+    #[inline(never)]
+    fn reseed_and_generate(&mut self,
+                           results: &mut <Self as BlockRngCore>::Results,
+                           global_fork_counter: usize)
+    {
+        if self.is_forked(global_fork_counter) {
+            info!("Fork detected, reseeding RNG");
+        } else {
+            trace!("Reseeding RNG (periodic reseed)");
+        }
+
+        let num_bytes =
+            results.as_ref().len() * size_of::<<R as BlockRngCore>::Item>();
+
+        let threshold = if let Err(e) = self.reseed() {
+            let delay = match e.kind {
+                ErrorKind::Transient => num_bytes as i64,
+                kind @ _ if kind.should_retry() => self.threshold >> 8,
+                _ => self.threshold,
+            };
+            warn!("Reseeding RNG delayed reseeding by {} bytes due to \
+                   error from source: {}", delay, e);
+            delay
+        } else {
+            self.fork_counter = global_fork_counter;
+            self.threshold
+        };
+
+        self.bytes_until_reseed = threshold - num_bytes as i64;
+        self.inner.generate(results);
+    }
+}
+
+impl<R, Rsdr> Clone for ReseedingCore<R, Rsdr>
+where R: BlockRngCore + SeedableRng + Clone,
+      Rsdr: RngCore + Clone
+{
+    fn clone(&self) -> ReseedingCore<R, Rsdr> {
+        ReseedingCore {
+            inner: self.inner.clone(),
+            reseeder: self.reseeder.clone(),
+            threshold: self.threshold,
+            bytes_until_reseed: 0, // reseed clone on first use
+            fork_counter: self.fork_counter,
+        }
+    }
+}
+
+impl<R, Rsdr> CryptoRng for ReseedingCore<R, Rsdr>
+where R: BlockRngCore + SeedableRng + CryptoRng,
+      Rsdr: RngCore + CryptoRng {}
+
+
+#[cfg(all(feature="std", unix, not(target_os="emscripten")))]
+mod fork {
+    extern crate libc;
+
+    use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+    use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT};
+
+    // Fork protection
+    //
+    // We implement fork protection on Unix using `pthread_atfork`.
+    // When the process is forked, we increment `RESEEDING_RNG_FORK_COUNTER`.
+    // Every `ReseedingRng` stores the last known value of the static in
+    // `fork_counter`. If the cached `fork_counter` is less than
+    // `RESEEDING_RNG_FORK_COUNTER`, it is time to reseed this RNG.
+    //
+    // If reseeding fails, we don't deal with this by setting a delay, but just
+    // don't update `fork_counter`, so a reseed is attempted as soon as
+    // possible.
+
+    static RESEEDING_RNG_FORK_COUNTER: AtomicUsize = ATOMIC_USIZE_INIT;
+
+    pub fn get_fork_counter() -> usize {
+        RESEEDING_RNG_FORK_COUNTER.load(Ordering::Relaxed)
+    }
+
+    static FORK_HANDLER_REGISTERED: AtomicBool = ATOMIC_BOOL_INIT;
+
+    extern fn fork_handler() {
+        // Note: fetch_add is defined to wrap on overflow
+        // (which is what we want).
+        RESEEDING_RNG_FORK_COUNTER.fetch_add(1, Ordering::Relaxed);
+    }
+
+    pub fn register_fork_handler() {
+        if FORK_HANDLER_REGISTERED.load(Ordering::Relaxed) == false {
+            unsafe { libc::pthread_atfork(None, None, Some(fork_handler)) };
+            FORK_HANDLER_REGISTERED.store(true, Ordering::Relaxed);
+        }
+    }
+}
+
+#[cfg(not(all(feature="std", unix, not(target_os="emscripten"))))]
+mod fork {
+    pub fn get_fork_counter() -> usize { 0 }
+    pub fn register_fork_handler() {}
+}
+
+
+#[cfg(test)]
+mod test {
+    use {Rng, SeedableRng};
+    use rand_chacha::ChaChaCore;
+    use rngs::mock::StepRng;
+    use super::ReseedingRng;
+
+    #[test]
+    fn test_reseeding() {
+        let mut zero = StepRng::new(0, 0);
+        let rng = ChaChaCore::from_rng(&mut zero).unwrap();
+        let mut reseeding = ReseedingRng::new(rng, 32*4, zero);
+
+        // Currently we only support for arrays up to length 32.
+        // TODO: cannot generate seq via Rng::gen because it uses different alg
+        let mut buf = [0u32; 32]; // Needs to be a multiple of the RNGs result
+                                  // size to test exactly.
+        reseeding.fill(&mut buf);
+        let seq = buf;
+        for _ in 0..10 {
+            reseeding.fill(&mut buf);
+            assert_eq!(buf, seq);
+        }
+    }
+
+    #[test]
+    fn test_clone_reseeding() {
+        let mut zero = StepRng::new(0, 0);
+        let rng = ChaChaCore::from_rng(&mut zero).unwrap();
+        let mut rng1 = ReseedingRng::new(rng, 32*4, zero);
+
+        let first: u32 = rng1.gen();
+        for _ in 0..10 { let _ = rng1.gen::<u32>(); }
+
+        let mut rng2 = rng1.clone();
+        assert_eq!(first, rng2.gen::<u32>());
+    }
+}
diff --git a/rand/src/rngs/entropy.rs b/rand/src/rngs/entropy.rs
new file mode 100644
index 0000000..8736324
--- /dev/null
+++ b/rand/src/rngs/entropy.rs
@@ -0,0 +1,297 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Entropy generator, or wrapper around external generators
+
+use rand_core::{RngCore, CryptoRng, Error, ErrorKind, impls};
+#[allow(unused)]
+use rngs;
+
+/// An interface returning random data from external source(s), provided
+/// specifically for securely seeding algorithmic generators (PRNGs).
+///
+/// Where possible, `EntropyRng` retrieves random data from the operating
+/// system's interface for random numbers ([`OsRng`]); if that fails it will
+/// fall back to the [`JitterRng`] entropy collector. In the latter case it will
+/// still try to use [`OsRng`] on the next usage.
+///
+/// If no secure source of entropy is available `EntropyRng` will panic on use;
+/// i.e. it should never output predictable data.
+///
+/// This is either a little slow ([`OsRng`] requires a system call) or extremely
+/// slow ([`JitterRng`] must use significant CPU time to generate sufficient
+/// jitter); for better performance it is common to seed a local PRNG from
+/// external entropy then primarily use the local PRNG ([`thread_rng`] is
+/// provided as a convenient, local, automatically-seeded CSPRNG).
+///
+/// # Panics
+///
+/// On most systems, like Windows, Linux, macOS and *BSD on common hardware, it
+/// is highly unlikely for both [`OsRng`] and [`JitterRng`] to fail. But on
+/// combinations like webassembly without Emscripten or stdweb both sources are
+/// unavailable. If both sources fail, only [`try_fill_bytes`] is able to
+/// report the error, and only the one from `OsRng`. The other [`RngCore`]
+/// methods will panic in case of an error.
+///
+/// [`OsRng`]: struct.OsRng.html
+/// [`JitterRng`]: jitter/struct.JitterRng.html
+/// [`thread_rng`]: ../fn.thread_rng.html
+/// [`RngCore`]: ../trait.RngCore.html
+/// [`try_fill_bytes`]: ../trait.RngCore.html#method.tymethod.try_fill_bytes
+#[derive(Debug)]
+pub struct EntropyRng {
+    source: Source,
+}
+
+#[derive(Debug)]
+enum Source {
+    Os(Os),
+    Custom(Custom),
+    Jitter(Jitter),
+    None,
+}
+
+impl EntropyRng {
+    /// Create a new `EntropyRng`.
+    ///
+    /// This method will do no system calls or other initialization routines,
+    /// those are done on first use. This is done to make `new` infallible,
+    /// and `try_fill_bytes` the only place to report errors.
+    pub fn new() -> Self {
+        EntropyRng { source: Source::None }
+    }
+}
+
+impl Default for EntropyRng {
+    fn default() -> Self {
+        EntropyRng::new()
+    }
+}
+
+impl RngCore for EntropyRng {
+    fn next_u32(&mut self) -> u32 {
+        impls::next_u32_via_fill(self)
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_fill(self)
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.try_fill_bytes(dest).unwrap_or_else(|err|
+                panic!("all entropy sources failed; first error: {}", err))
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        let mut reported_error = None;
+
+        if let Source::Os(ref mut os_rng) = self.source {
+            match os_rng.fill(dest) {
+                Ok(()) => return Ok(()),
+                Err(err) => {
+                    warn!("EntropyRng: OsRng failed \
+                          [trying other entropy sources]: {}", err);
+                    reported_error = Some(err);
+                },
+            }
+        } else if Os::is_supported() {
+            match Os::new_and_fill(dest) {
+                Ok(os_rng) => {
+                    debug!("EntropyRng: using OsRng");
+                    self.source = Source::Os(os_rng);
+                    return Ok(());
+                },
+                Err(err) => { reported_error = reported_error.or(Some(err)) },
+            }
+        }
+
+        if let Source::Custom(ref mut rng) = self.source {
+            match rng.fill(dest) {
+                Ok(()) => return Ok(()),
+                Err(err) => {
+                    warn!("EntropyRng: custom entropy source failed \
+                          [trying other entropy sources]: {}", err);
+                    reported_error = Some(err);
+                },
+            }
+        } else if Custom::is_supported() {
+            match Custom::new_and_fill(dest) {
+                Ok(custom) => {
+                    debug!("EntropyRng: using custom entropy source");
+                    self.source = Source::Custom(custom);
+                    return Ok(());
+                },
+                Err(err) => { reported_error = reported_error.or(Some(err)) },
+            }
+        }
+
+        if let Source::Jitter(ref mut jitter_rng) = self.source {
+            match jitter_rng.fill(dest) {
+                Ok(()) => return Ok(()),
+                Err(err) => {
+                    warn!("EntropyRng: JitterRng failed: {}", err);
+                    reported_error = Some(err);
+                },
+            }
+        } else if Jitter::is_supported() {
+            match Jitter::new_and_fill(dest) {
+                Ok(jitter_rng) => {
+                    debug!("EntropyRng: using JitterRng");
+                    self.source = Source::Jitter(jitter_rng);
+                    return Ok(());
+                },
+                Err(err) => { reported_error = reported_error.or(Some(err)) },
+            }
+        }
+
+        if let Some(err) = reported_error {
+            Err(Error::with_cause(ErrorKind::Unavailable,
+                                  "All entropy sources failed",
+                                  err))
+        } else {
+            Err(Error::new(ErrorKind::Unavailable,
+                           "No entropy sources available"))
+        }
+    }
+}
+
+impl CryptoRng for EntropyRng {}
+
+
+
+trait EntropySource {
+    fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error>
+        where Self: Sized;
+
+    fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error>;
+
+    fn is_supported() -> bool { true }
+}
+
+#[allow(unused)]
+#[derive(Clone, Debug)]
+struct NoSource;
+
+#[allow(unused)]
+impl EntropySource for NoSource {
+    fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
+        Err(Error::new(ErrorKind::Unavailable, "Source not supported"))
+    }
+
+    fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        unreachable!()
+    }
+
+    fn is_supported() -> bool { false }
+}
+
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+#[derive(Clone, Debug)]
+pub struct Os(rngs::OsRng);
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+impl EntropySource for Os {
+    fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
+        let mut rng = rngs::OsRng::new()?;
+        rng.try_fill_bytes(dest)?;
+        Ok(Os(rng))
+    }
+
+    fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(not(all(feature="std",
+              any(target_os = "linux", target_os = "android",
+                  target_os = "netbsd",
+                  target_os = "dragonfly",
+                  target_os = "haiku",
+                  target_os = "emscripten",
+                  target_os = "solaris",
+                  target_os = "cloudabi",
+                  target_os = "macos", target_os = "ios",
+                  target_os = "freebsd",
+                  target_os = "openbsd", target_os = "bitrig",
+                  target_os = "redox",
+                  target_os = "fuchsia",
+                  windows,
+                  all(target_arch = "wasm32", feature = "stdweb"),
+                  all(target_arch = "wasm32", feature = "wasm-bindgen"),
+))))]
+type Os = NoSource;
+
+
+type Custom = NoSource;
+
+
+#[cfg(not(target_arch = "wasm32"))]
+#[derive(Clone, Debug)]
+pub struct Jitter(rngs::JitterRng);
+
+#[cfg(not(target_arch = "wasm32"))]
+impl EntropySource for Jitter {
+    fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
+        let mut rng = rngs::JitterRng::new()?;
+        rng.try_fill_bytes(dest)?;
+        Ok(Jitter(rng))
+    }
+
+    fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+#[cfg(target_arch = "wasm32")]
+type Jitter = NoSource;
+
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_entropy() {
+        let mut rng = EntropyRng::new();
+        let n = (rng.next_u32() ^ rng.next_u32()).count_ones();
+        assert!(n >= 2);    // p(failure) approx 1e-7
+    }
+}
diff --git a/rand/src/jitter.rs b/rand/src/rngs/jitter.rs
index 3693481..3e93477 100644
--- a/rand/src/jitter.rs
+++ b/rand/src/rngs/jitter.rs
@@ -1,10 +1,8 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+// Copyright 2018 Developers of the Rand project.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 //
@@ -16,10 +14,15 @@
 
 //! Non-physical true random number generator based on timing jitter.
 
-use Rng;
+// Note: the C implementation of `Jitterentropy` relies on being compiled
+// without optimizations. This implementation goes through lengths to make the
+// compiler not optimize out code which does influence timing jitter, but is
+// technically dead code.
+
+use rand_core::{RngCore, CryptoRng, Error, ErrorKind, impls};
 
 use core::{fmt, mem, ptr};
-#[cfg(feature="std")]
+#[cfg(all(feature="std", not(target_arch = "wasm32")))]
 use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
 
 const MEMORY_BLOCKS: usize = 64;
@@ -31,8 +34,8 @@ const MEMORY_SIZE: usize = MEMORY_BLOCKS * MEMORY_BLOCKSIZE;
 ///
 /// This is a true random number generator, as opposed to pseudo-random
 /// generators. Random numbers generated by `JitterRng` can be seen as fresh
-/// entropy. A consequence is that is orders of magnitude slower than `OsRng`
-/// and PRNGs (about 10^3 .. 10^6 slower).
+/// entropy. A consequence is that is orders of magnitude slower than [`OsRng`]
+/// and PRNGs (about 10<sup>3</sup>..10<sup>6</sup> slower).
 ///
 /// There are very few situations where using this RNG is appropriate. Only very
 /// few applications require true entropy. A normal PRNG can be statistically
@@ -40,29 +43,155 @@ const MEMORY_SIZE: usize = MEMORY_BLOCKS * MEMORY_BLOCKSIZE;
 /// predict.
 ///
 /// Use of `JitterRng` is recommended for initializing cryptographic PRNGs when
-/// `OsRng` is not available.
+/// [`OsRng`] is not available.
+///
+/// `JitterRng` can be used without the standard library, but not conveniently,
+/// you must provide a high-precision timer and carefully have to follow the
+/// instructions of [`new_with_timer`].
 ///
 /// This implementation is based on
 /// [Jitterentropy](http://www.chronox.de/jent.html) version 2.1.0.
-//
-// Note: the C implementation relies on being compiled without optimizations.
-// This implementation goes through lengths to make the compiler not optimise
-// out what is technically dead code, but that does influence timing jitter.
+///
+/// Note: There is no accurate timer available on Wasm platforms, to help
+/// prevent fingerprinting or timing side-channel attacks. Therefore
+/// [`JitterRng::new()`] is not available on Wasm.
+///
+/// # Quality testing
+///
+/// [`JitterRng::new()`] has build-in, but limited, quality testing, however
+/// before using `JitterRng` on untested hardware, or after changes that could
+/// effect how the code is optimized (such as a new LLVM version), it is
+/// recommend to run the much more stringent
+/// [NIST SP 800-90B Entropy Estimation Suite](
+/// https://github.com/usnistgov/SP800-90B_EntropyAssessment).
+///
+/// Use the following code using [`timer_stats`] to collect the data:
+///
+/// ```no_run
+/// use rand::rngs::JitterRng;
+/// #
+/// # use std::error::Error;
+/// # use std::fs::File;
+/// # use std::io::Write;
+/// #
+/// # fn try_main() -> Result<(), Box<Error>> {
+/// let mut rng = JitterRng::new()?;
+///
+/// // 1_000_000 results are required for the
+/// // NIST SP 800-90B Entropy Estimation Suite
+/// const ROUNDS: usize = 1_000_000;
+/// let mut deltas_variable: Vec<u8> = Vec::with_capacity(ROUNDS);
+/// let mut deltas_minimal: Vec<u8> = Vec::with_capacity(ROUNDS);
+///
+/// for _ in 0..ROUNDS {
+///     deltas_variable.push(rng.timer_stats(true) as u8);
+///     deltas_minimal.push(rng.timer_stats(false) as u8);
+/// }
+///
+/// // Write out after the statistics collection loop, to not disturb the
+/// // test results.
+/// File::create("jitter_rng_var.bin")?.write(&deltas_variable)?;
+/// File::create("jitter_rng_min.bin")?.write(&deltas_minimal)?;
+/// #
+/// # Ok(())
+/// # }
+/// #
+/// # fn main() {
+/// #     try_main().unwrap();
+/// # }
+/// ```
+///
+/// This will produce two files: `jitter_rng_var.bin` and `jitter_rng_min.bin`.
+/// Run the Entropy Estimation Suite in three configurations, as outlined below.
+/// Every run has two steps. One step to produce an estimation, another to
+/// validate the estimation.
+///
+/// 1. Estimate the expected amount of entropy that is at least available with
+///    each round of the entropy collector. This number should be greater than
+///    the amount estimated with `64 / test_timer()`.
+///    ```sh
+///    python noniid_main.py -v jitter_rng_var.bin 8
+///    restart.py -v jitter_rng_var.bin 8 <min-entropy>
+///    ```
+/// 2. Estimate the expected amount of entropy that is available in the last 4
+///    bits of the timer delta after running noice sources. Note that a value of
+///    `3.70` is the minimum estimated entropy for true randomness.
+///    ```sh
+///    python noniid_main.py -v -u 4 jitter_rng_var.bin 4
+///    restart.py -v -u 4 jitter_rng_var.bin 4 <min-entropy>
+///    ```
+/// 3. Estimate the expected amount of entropy that is available to the entropy
+///    collector if both noice sources only run their minimal number of times.
+///    This measures the absolute worst-case, and gives a lower bound for the
+///    available entropy.
+///    ```sh
+///    python noniid_main.py -v -u 4 jitter_rng_min.bin 4
+///    restart.py -v -u 4 jitter_rng_min.bin 4 <min-entropy>
+///    ```
+///
+/// [`OsRng`]: struct.OsRng.html
+/// [`JitterRng::new()`]: struct.JitterRng.html#method.new
+/// [`new_with_timer`]: struct.JitterRng.html#method.new_with_timer
+/// [`timer_stats`]: struct.JitterRng.html#method.timer_stats
 pub struct JitterRng {
     data: u64, // Actual random number
     // Number of rounds to run the entropy collector per 64 bits
-    rounds: u32,
-    // Timer and previous time stamp, used by `measure_jitter`
+    rounds: u8,
+    // Timer used by `measure_jitter`
     timer: fn() -> u64,
+    // Memory for the Memory Access noise source
+    mem_prev_index: u16,
+    // Make `next_u32` not waste 32 bits
+    data_half_used: bool,
+}
+
+// Note: `JitterRng` maintains a small 64-bit entropy pool. With every
+// `generate` 64 new bits should be integrated in the pool. If a round of
+// `generate` were to collect less than the expected 64 bit, then the returned
+// value, and the new state of the entropy pool, would be in some way related to
+// the initial state. It is therefore better if the initial state of the entropy
+// pool is different on each call to `generate`. This has a few implications:
+// - `generate` should be called once before using `JitterRng` to produce the
+//   first usable value (this is done by default in `new`);
+// - We do not zero the entropy pool after generating a result. The reference
+//   implementation also does not support zeroing, but recommends generating a
+//   new value without using it if you want to protect a previously generated
+//   'secret' value from someone inspecting the memory;
+// - Implementing `Clone` seems acceptable, as it would not cause the systematic
+//   bias a constant might cause. Only instead of one value that could be
+//   potentially related to the same initial state, there are now two.
+
+// Entropy collector state.
+// These values are not necessary to preserve across runs.
+struct EcState {
+    // Previous time stamp to determine the timer delta
     prev_time: u64,
     // Deltas used for the stuck test
-    last_delta: i64,
-    last_delta2: i64,
+    last_delta: i32,
+    last_delta2: i32,
     // Memory for the Memory Access noise source
-    mem_prev_index: usize,
     mem: [u8; MEMORY_SIZE],
-    // Make `next_u32` not waste 32 bits
-    data_remaining: Option<u32>,
+}
+
+impl EcState {
+    // Stuck test by checking the:
+    // - 1st derivation of the jitter measurement (time delta)
+    // - 2nd derivation of the jitter measurement (delta of time deltas)
+    // - 3rd derivation of the jitter measurement (delta of delta of time
+    //   deltas)
+    //
+    // All values must always be non-zero.
+    // This test is a heuristic to see whether the last measurement holds
+    // entropy.
+    fn stuck(&mut self, current_delta: i32) -> bool {
+        let delta2 = self.last_delta - current_delta;
+        let delta3 = delta2 - self.last_delta2;
+
+        self.last_delta = current_delta;
+        self.last_delta2 = delta2;
+
+        current_delta == 0 || delta2 == 0 || delta3 == 0
+    }
 }
 
 // Custom Debug implementation that does not expose the internal state
@@ -72,7 +201,23 @@ impl fmt::Debug for JitterRng {
     }
 }
 
-/// An error that can occur when `test_timer` fails.
+impl Clone for JitterRng {
+    fn clone(&self) -> JitterRng {
+        JitterRng {
+            data: self.data,
+            rounds: self.rounds,
+            timer: self.timer,
+            mem_prev_index: self.mem_prev_index,
+            // The 32 bits that may still be unused from the previous round are
+            // for the original to use, not for the clone.
+            data_half_used: false,
+        }
+    }
+}
+
+/// An error that can occur when [`JitterRng::test_timer`] fails.
+///
+/// [`JitterRng::test_timer`]: struct.JitterRng.html#method.test_timer
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum TimerError {
     /// No timer available.
@@ -115,29 +260,43 @@ impl ::std::error::Error for TimerError {
     }
 }
 
+impl From<TimerError> for Error {
+    fn from(err: TimerError) -> Error {
+        // Timer check is already quite permissive of failures so we don't
+        // expect false-positive failures, i.e. any error is irrecoverable.
+        Error::with_cause(ErrorKind::Unavailable,
+                              "timer jitter failed basic quality tests", err)
+    }
+}
+
 // Initialise to zero; must be positive
-#[cfg(feature="std")]
+#[cfg(all(feature="std", not(target_arch = "wasm32")))]
 static JITTER_ROUNDS: AtomicUsize = ATOMIC_USIZE_INIT;
 
 impl JitterRng {
-    /// Create a new `JitterRng`.
-    /// Makes use of `std::time` for a timer.
+    /// Create a new `JitterRng`. Makes use of `std::time` for a timer, or a
+    /// platform-specific function with higher accuracy if necessary and
+    /// available.
     ///
     /// During initialization CPU execution timing jitter is measured a few
     /// hundred times. If this does not pass basic quality tests, an error is
     /// returned. The test result is cached to make subsequent calls faster.
-    #[cfg(feature="std")]
+    #[cfg(all(feature="std", not(target_arch = "wasm32")))]
     pub fn new() -> Result<JitterRng, TimerError> {
-        let mut ec = JitterRng::new_with_timer(platform::get_nstime);
-        let mut rounds = JITTER_ROUNDS.load(Ordering::Relaxed) as u32;
+        let mut state = JitterRng::new_with_timer(platform::get_nstime);
+        let mut rounds = JITTER_ROUNDS.load(Ordering::Relaxed) as u8;
         if rounds == 0 {
             // No result yet: run test.
             // This allows the timer test to run multiple times; we don't care.
-            rounds = ec.test_timer()?;
+            rounds = state.test_timer()?;
             JITTER_ROUNDS.store(rounds as usize, Ordering::Relaxed);
+            info!("JitterRng: using {} rounds per u64 output", rounds);
         }
-        ec.set_rounds(rounds);
-        Ok(ec)
+        state.set_rounds(rounds);
+
+        // Fill `data` with a non-zero value.
+        state.gen_entropy();
+        Ok(state)
     }
 
     /// Create a new `JitterRng`.
@@ -147,44 +306,65 @@ impl JitterRng {
     /// The timer must have nanosecond precision.
     ///
     /// This method is more low-level than `new()`. It is the responsibility of
-    /// the caller to run `test_timer` before using any numbers generated with
-    /// `JitterRng`, and optionally call `set_rounds()`.
+    /// the caller to run [`test_timer`] before using any numbers generated with
+    /// `JitterRng`, and optionally call [`set_rounds`]. Also it is important to
+    /// consume at least one `u64` before using the first result to initialize
+    /// the entropy collection pool.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use rand::{Rng, Error};
+    /// use rand::rngs::JitterRng;
+    ///
+    /// # fn try_inner() -> Result<(), Error> {
+    /// fn get_nstime() -> u64 {
+    ///     use std::time::{SystemTime, UNIX_EPOCH};
+    ///
+    ///     let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
+    ///     // The correct way to calculate the current time is
+    ///     // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
+    ///     // But this is faster, and the difference in terms of entropy is
+    ///     // negligible (log2(10^9) == 29.9).
+    ///     dur.as_secs() << 30 | dur.subsec_nanos() as u64
+    /// }
+    ///
+    /// let mut rng = JitterRng::new_with_timer(get_nstime);
+    /// let rounds = rng.test_timer()?;
+    /// rng.set_rounds(rounds); // optional
+    /// let _ = rng.gen::<u64>();
+    ///
+    /// // Ready for use
+    /// let v: u64 = rng.gen();
+    /// # Ok(())
+    /// # }
+    ///
+    /// # let _ = try_inner();
+    /// ```
+    ///
+    /// [`test_timer`]: struct.JitterRng.html#method.test_timer
+    /// [`set_rounds`]: struct.JitterRng.html#method.set_rounds
     pub fn new_with_timer(timer: fn() -> u64) -> JitterRng {
-        let mut ec = JitterRng {
+        JitterRng {
             data: 0,
             rounds: 64,
-            timer: timer,
-            prev_time: 0,
-            last_delta: 0,
-            last_delta2: 0,
+            timer,
             mem_prev_index: 0,
-            mem: [0; MEMORY_SIZE],
-            data_remaining: None,
-        };
-
-        // Fill `data`, `prev_time`, `last_delta` and `last_delta2` with
-        // non-zero values.
-        ec.prev_time = timer();
-        ec.gen_entropy();
-
-        // Do a single read from `self.mem` to make sure the Memory Access noise
-        // source is not optimised out.
-        // Note: this read is important, it effects optimisations for the entire
-        // module!
-        black_box(ec.mem[0]);
-
-        ec
+            data_half_used: false,
+        }
     }
 
     /// Configures how many rounds are used to generate each 64-bit value.
     /// This must be greater than zero, and has a big impact on performance
     /// and output quality.
     ///
-    /// `new_with_timer` conservatively uses 64 rounds, but often less rounds
+    /// [`new_with_timer`] conservatively uses 64 rounds, but often less rounds
     /// can be used. The `test_timer()` function returns the minimum number of
     /// rounds required for full strength (platform dependent), so one may use
     /// `rng.set_rounds(rng.test_timer()?);` or cache the value.
-    pub fn set_rounds(&mut self, rounds: u32) {
+    ///
+    /// [`new_with_timer`]: struct.JitterRng.html#method.new_with_timer
+    pub fn set_rounds(&mut self, rounds: u8) {
         assert!(rounds > 0);
         self.rounds = rounds;
     }
@@ -212,7 +392,7 @@ impl JitterRng {
         let mask = (1 << n_bits) - 1;
         for _ in 0..folds {
             rounds ^= time & mask;
-            time = time >> n_bits;
+            time >>= n_bits;
         }
 
         rounds as u32
@@ -233,7 +413,7 @@ impl JitterRng {
         fn lfsr(mut data: u64, time: u64) -> u64{
             for i in 1..65 {
                 let mut tmp = time << (64 - i);
-                tmp = tmp >> (64 - 1);
+                tmp >>= 64 - 1;
 
                 // Fibonacci LSFR with polynomial of
                 // x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
@@ -288,11 +468,11 @@ impl JitterRng {
     // range of wait states. However, to reliably access either L3 or memory,
     // the `self.mem` memory must be quite large which is usually not desirable.
     #[inline(never)]
-    fn memaccess(&mut self, var_rounds: bool) {
+    fn memaccess(&mut self, mem: &mut [u8; MEMORY_SIZE], var_rounds: bool) {
         let mut acc_loop_cnt = 128;
         if var_rounds { acc_loop_cnt += self.random_loop_cnt(4) };
 
-        let mut index = self.mem_prev_index;
+        let mut index = self.mem_prev_index as usize;
         for _ in 0..acc_loop_cnt {
             // Addition of memblocksize - 1 to index with wrap around logic to
             // ensure that every memory location is hit evenly.
@@ -302,42 +482,21 @@ impl JitterRng {
 
             // memory access: just add 1 to one byte
             // memory access implies read from and write to memory location
-            let tmp = self.mem[index];
-            self.mem[index] = tmp.wrapping_add(1);
+            mem[index] = mem[index].wrapping_add(1);
         }
-        self.mem_prev_index = index;
-    }
-
-
-    // Stuck test by checking the:
-    // - 1st derivation of the jitter measurement (time delta)
-    // - 2nd derivation of the jitter measurement (delta of time deltas)
-    // - 3rd derivation of the jitter measurement (delta of delta of time
-    //   deltas)
-    //
-    // All values must always be non-zero.
-    // This test is a heuristic to see whether the last measurement holds
-    // entropy.
-    fn stuck(&mut self, current_delta: i64) -> bool {
-        let delta2 = self.last_delta - current_delta;
-        let delta3 = delta2 - self.last_delta2;
-
-        self.last_delta = current_delta;
-        self.last_delta2 = delta2;
-
-        current_delta == 0 || delta2 == 0 || delta3 == 0
+        self.mem_prev_index = index as u16;
     }
 
     // This is the heart of the entropy generation: calculate time deltas and
     // use the CPU jitter in the time deltas. The jitter is injected into the
     // entropy pool.
     //
-    // Ensure that `self.prev_time` is primed before using the output of this
+    // Ensure that `ec.prev_time` is primed before using the output of this
     // function. This can be done by calling this function and not using its
     // result.
-    fn measure_jitter(&mut self) -> Option<()> {
+    fn measure_jitter(&mut self, ec: &mut EcState) -> Option<()> {
         // Invoke one noise source before time measurement to add variations
-        self.memaccess(true);
+        self.memaccess(&mut ec.mem, true);
 
         // Get time stamp and calculate time delta to previous
         // invocation to measure the timing variations
@@ -345,15 +504,15 @@ impl JitterRng {
         // Note: wrapping_sub combined with a cast to `i64` generates a correct
         // delta, even in the unlikely case this is a timer that is not strictly
         // monotonic.
-        let current_delta = time.wrapping_sub(self.prev_time) as i64;
-        self.prev_time = time;
+        let current_delta = time.wrapping_sub(ec.prev_time) as i64 as i32;
+        ec.prev_time = time;
 
         // Call the next noise source which also injects the data
         self.lfsr_time(current_delta as u64, true);
 
         // Check whether we have a stuck measurement (i.e. does the last
         // measurement holds entropy?).
-        if self.stuck(current_delta) { return None };
+        if ec.stuck(current_delta) { return None };
 
         // Rotate the data buffer by a prime number (any odd number would
         // do) to ensure that every bit position of the input time stamp
@@ -415,35 +574,47 @@ impl JitterRng {
     }
 
     fn gen_entropy(&mut self) -> u64 {
-        // Prime `self.prev_time`, and run the noice sources to make sure the
+        trace!("JitterRng: collecting entropy");
+
+        // Prime `ec.prev_time`, and run the noice sources to make sure the
         // first loop round collects the expected entropy.
-        let _ = self.measure_jitter();
+        let mut ec = EcState {
+            prev_time: (self.timer)(),
+            last_delta: 0,
+            last_delta2: 0,
+            mem: [0; MEMORY_SIZE],
+        };
+        let _ = self.measure_jitter(&mut ec);
 
         for _ in 0..self.rounds {
             // If a stuck measurement is received, repeat measurement
             // Note: we do not guard against an infinite loop, that would mean
             // the timer suddenly became broken.
-            while self.measure_jitter().is_none() {}
+            while self.measure_jitter(&mut ec).is_none() {}
         }
 
+        // Do a single read from `self.mem` to make sure the Memory Access noise
+        // source is not optimised out.
+        black_box(ec.mem[0]);
+
         self.stir_pool();
         self.data
     }
-
+    
     /// Basic quality tests on the timer, by measuring CPU timing jitter a few
     /// hundred times.
     ///
     /// If succesful, this will return the estimated number of rounds necessary
-    /// to collect 64 bits of entropy. Otherwise a `TimerError` with the cause
+    /// to collect 64 bits of entropy. Otherwise a [`TimerError`] with the cause
     /// of the failure will be returned.
-    pub fn test_timer(&mut self) -> Result<u32, TimerError> {
+    ///
+    /// [`TimerError`]: enum.TimerError.html
+    pub fn test_timer(&mut self) -> Result<u8, TimerError> {
+        debug!("JitterRng: testing timer ...");
         // We could add a check for system capabilities such as `clock_getres`
         // or check for `CONFIG_X86_TSC`, but it does not make much sense as the
         // following sanity checks verify that we have a high-resolution timer.
 
-        #[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
-        return Err(TimerError::NoTimer);
-
         let mut delta_sum = 0;
         let mut old_delta = 0;
 
@@ -451,6 +622,13 @@ impl JitterRng {
         let mut count_mod = 0;
         let mut count_stuck = 0;
 
+        let mut ec = EcState {
+            prev_time: (self.timer)(),
+            last_delta: 0,
+            last_delta2: 0,
+            mem: [0; MEMORY_SIZE],
+        };
+
         // TESTLOOPCOUNT needs some loops to identify edge systems.
         // 100 is definitely too little.
         const TESTLOOPCOUNT: u64 = 300;
@@ -459,7 +637,7 @@ impl JitterRng {
         for i in 0..(CLEARCACHE + TESTLOOPCOUNT) {
             // Measure time delta of core entropy collection logic
             let time = (self.timer)();
-            self.memaccess(true);
+            self.memaccess(&mut ec.mem, true);
             self.lfsr_time(time, true);
             let time2 = (self.timer)();
 
@@ -467,7 +645,7 @@ impl JitterRng {
             if time == 0 || time2 == 0 {
                 return Err(TimerError::NoTimer);
             }
-            let delta = time2.wrapping_sub(time) as i64;
+            let delta = time2.wrapping_sub(time) as i64 as i32;
 
             // Test whether timer is fine grained enough to provide delta even
             // when called shortly after each other -- this implies that we also
@@ -483,7 +661,7 @@ impl JitterRng {
             // measurements.
             if i < CLEARCACHE { continue; }
 
-            if self.stuck(delta) { count_stuck += 1; }
+            if ec.stuck(delta) { count_stuck += 1; }
 
             // Test whether we have an increasing timer.
             if !(time2 > time) { time_backwards += 1; }
@@ -499,6 +677,10 @@ impl JitterRng {
             old_delta = delta;
         }
 
+        // Do a single read from `self.mem` to make sure the Memory Access noise
+        // source is not optimised out.
+        black_box(ec.mem[0]);
+
         // We allow the time to run backwards for up to three times.
         // This can happen if the clock is being adjusted by NTP operations.
         // If such an operation just happens to interfere with our test, it
@@ -539,140 +721,69 @@ impl JitterRng {
         // available bits of entropy per round here for two reasons:
         // 1. Simple estimates of the available bits (like Shannon entropy) are
         //    too optimistic.
-        // 2)  Unless we want to waste a lot of time during intialization, there
-        //     only a small number of samples are available.
+        // 2. Unless we want to waste a lot of time during intialization, there
+        //    only a small number of samples are available.
         //
         // Therefore we use a very simple and conservative estimate:
         // `let bits_of_entropy = log2(delta_average) / 2`.
         //
         // The number of rounds `measure_jitter` should run to collect 64 bits
         // of entropy is `64 / bits_of_entropy`.
-        //
-        // To have smaller rounding errors, intermediate values are multiplied
-        // by `FACTOR`. To compensate for `log2` and division rounding down,
-        // add 1.
         let delta_average = delta_sum / TESTLOOPCOUNT;
-        // println!("delta_average: {}", delta_average);
-
-        const FACTOR: u32  = 3;
-        fn log2(x: u64) -> u32 { 64 - x.leading_zeros() }
 
-        // pow(δ, FACTOR) must be representable; if you have overflow reduce FACTOR
-        Ok(64 * 2 * FACTOR / (log2(delta_average.pow(FACTOR)) + 1))
+        if delta_average >= 16 {
+            let log2 = 64 - delta_average.leading_zeros();
+            // Do something similar to roundup(64/(log2/2)):
+            Ok( ((64u32 * 2 + log2 - 1) / log2) as u8)
+        } else {
+            // For values < 16 the rounding error becomes too large, use a
+            // lookup table.
+            // Values 0 and 1 are invalid, and filtered out by the
+            // `delta_sum < TESTLOOPCOUNT` test above.
+            let log2_lookup = [0,  0, 128, 81, 64, 56, 50, 46,
+                               43, 41, 39, 38, 36, 35, 34, 33];
+            Ok(log2_lookup[delta_average as usize])
+        }
     }
 
     /// Statistical test: return the timer delta of one normal run of the
-    /// `JitterEntropy` entropy collector.
+    /// `JitterRng` entropy collector.
     ///
     /// Setting `var_rounds` to `true` will execute the memory access and the
     /// CPU jitter noice sources a variable amount of times (just like a real
-    /// `JitterEntropy` round).
+    /// `JitterRng` round).
     ///
     /// Setting `var_rounds` to `false` will execute the noice sources the
     /// minimal number of times. This can be used to measure the minimum amount
-    /// of entropy one round of entropy collector can collect in the worst case.
-    ///
-    /// # Example
-    ///
-    /// Use `timer_stats` to run the [NIST SP 800-90B Entropy Estimation Suite]
-    /// (https://github.com/usnistgov/SP800-90B_EntropyAssessment).
-    ///
-    /// This is the recommended way to test the quality of `JitterRng`. It
-    /// should be run before using the RNG on untested hardware, after changes
-    /// that could effect how the code is optimised, and after major compiler
-    /// compiler changes, like a new LLVM version.
-    ///
-    /// First generate two files `jitter_rng_var.bin` and `jitter_rng_var.min`.
-    ///
-    /// Execute `python noniid_main.py -v jitter_rng_var.bin 8`, and validate it
-    /// with `restart.py -v jitter_rng_var.bin 8 <min-entropy>`.
-    /// This number is the expected amount of entropy that is at least available
-    /// for each round of the entropy collector. This number should be greater
-    /// than the amount estimated with `64 / test_timer()`.
-    ///
-    /// Execute `python noniid_main.py -v -u 4 jitter_rng_var.bin 4`, and
-    /// validate it with `restart.py -v -u 4 jitter_rng_var.bin 4 <min-entropy>`.
-    /// This number is the expected amount of entropy that is available in the
-    /// last 4 bits of the timer delta after running noice sources. Note that
-    /// a value of 3.70 is the minimum estimated entropy for true randomness.
-    ///
-    /// Execute `python noniid_main.py -v -u 4 jitter_rng_var.bin 4`, and
-    /// validate it with `restart.py -v -u 4 jitter_rng_var.bin 4 <min-entropy>`.
-    /// This number is the expected amount of entropy that is available to the
-    /// entropy collecter if both noice sources only run their minimal number of
-    /// times. This measures the absolute worst-case, and gives a lower bound
-    /// for the available entropy.
-    ///
-    /// ```rust,no_run
-    /// use rand::JitterRng;
-    ///
-    /// # use std::error::Error;
-    /// # use std::fs::File;
-    /// # use std::io::Write;
-    /// #
-    /// # fn try_main() -> Result<(), Box<Error>> {
-    /// fn get_nstime() -> u64 {
-    ///     use std::time::{SystemTime, UNIX_EPOCH};
-    ///
-    ///     let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
-    ///     // The correct way to calculate the current time is
-    ///     // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
-    ///     // But this is faster, and the difference in terms of entropy is
-    ///     // negligible (log2(10^9) == 29.9).
-    ///     dur.as_secs() << 30 | dur.subsec_nanos() as u64
-    /// }
-    ///
-    /// // Do not initialize with `JitterRng::new`, but with `new_with_timer`.
-    /// // 'new' always runst `test_timer`, and can therefore fail to
-    /// // initialize. We want to be able to get the statistics even when the
-    /// // timer test fails.
-    /// let mut rng = JitterRng::new_with_timer(get_nstime);
-    ///
-    /// // 1_000_000 results are required for the NIST SP 800-90B Entropy
-    /// // Estimation Suite
-    /// // FIXME: this number is smaller here, otherwise the Doc-test is too slow
-    /// const ROUNDS: usize = 10_000;
-    /// let mut deltas_variable: Vec<u8> = Vec::with_capacity(ROUNDS);
-    /// let mut deltas_minimal: Vec<u8> = Vec::with_capacity(ROUNDS);
+    /// of entropy one round of the entropy collector can collect in the worst
+    /// case.
     ///
-    /// for _ in 0..ROUNDS {
-    ///     deltas_variable.push(rng.timer_stats(true) as u8);
-    ///     deltas_minimal.push(rng.timer_stats(false) as u8);
-    /// }
-    ///
-    /// // Write out after the statistics collection loop, to not disturb the
-    /// // test results.
-    /// File::create("jitter_rng_var.bin")?.write(&deltas_variable)?;
-    /// File::create("jitter_rng_min.bin")?.write(&deltas_minimal)?;
-    /// #
-    /// # Ok(())
-    /// # }
-    /// #
-    /// # fn main() {
-    /// #     try_main().unwrap();
-    /// # }
-    /// ```
-    #[cfg(feature="std")]
+    /// See [Quality testing](struct.JitterRng.html#quality-testing) on how to
+    /// use `timer_stats` to test the quality of `JitterRng`.
     pub fn timer_stats(&mut self, var_rounds: bool) -> i64 {
-        let time = platform::get_nstime();
-        self.memaccess(var_rounds);
+        let mut mem = [0; MEMORY_SIZE];
+
+        let time = (self.timer)();
+        self.memaccess(&mut mem, var_rounds);
         self.lfsr_time(time, var_rounds);
-        let time2 = platform::get_nstime();
+        let time2 = (self.timer)();
         time2.wrapping_sub(time) as i64
     }
 }
 
 #[cfg(feature="std")]
 mod platform {
-    #[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "windows", all(target_arch = "wasm32", not(target_os = "emscripten")))))]
+    #[cfg(not(any(target_os = "macos", target_os = "ios",
+                  target_os = "windows",
+                  target_arch = "wasm32")))]
     pub fn get_nstime() -> u64 {
         use std::time::{SystemTime, UNIX_EPOCH};
 
         let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
         // The correct way to calculate the current time is
         // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
-        // But this is faster, and the difference in terms of entropy is negligible
-        // (log2(10^9) == 29.9).
+        // But this is faster, and the difference in terms of entropy is
+        // negligible (log2(10^9) == 29.9).
         dur.as_secs() << 30 | dur.subsec_nanos() as u64
     }
 
@@ -680,11 +791,11 @@ mod platform {
     pub fn get_nstime() -> u64 {
         extern crate libc;
         // On Mac OS and iOS std::time::SystemTime only has 1000ns resolution.
-        // We use `mach_absolute_time` instead. This provides a CPU dependent unit,
-        // to get real nanoseconds the result should by multiplied by numer/denom
-        // from `mach_timebase_info`.
-        // But we are not interested in the exact nanoseconds, just entropy. So we
-        // use the raw result.
+        // We use `mach_absolute_time` instead. This provides a CPU dependent
+        // unit, to get real nanoseconds the result should by multiplied by
+        // numer/denom from `mach_timebase_info`.
+        // But we are not interested in the exact nanoseconds, just entropy. So
+        // we use the raw result.
         unsafe { libc::mach_absolute_time() }
     }
 
@@ -697,11 +808,6 @@ mod platform {
             *t.QuadPart() as u64
         }
     }
-
-    #[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
-    pub fn get_nstime() -> u64 {
-        unreachable!()
-    }
 }
 
 // A function that is opaque to the optimizer to assist in avoiding dead-code
@@ -714,41 +820,66 @@ fn black_box<T>(dummy: T) -> T {
     }
 }
 
-impl Rng for JitterRng {
+impl RngCore for JitterRng {
     fn next_u32(&mut self) -> u32 {
         // We want to use both parts of the generated entropy
-        if let Some(high) = self.data_remaining.take() {
-            high
+        if self.data_half_used {
+            self.data_half_used = false;
+            (self.data >> 32) as u32
         } else {
-            let data = self.next_u64();
-            self.data_remaining = Some((data >> 32) as u32);
-            data as u32
+            self.data = self.next_u64();
+            self.data_half_used = true;
+            self.data as u32
         }
     }
 
     fn next_u64(&mut self) -> u64 {
+       self.data_half_used = false;
        self.gen_entropy()
     }
 
     fn fill_bytes(&mut self, dest: &mut [u8]) {
-        let mut left = dest;
-        while left.len() >= 8 {
-            let (l, r) = {left}.split_at_mut(8);
-            left = r;
-            let chunk: [u8; 8] = unsafe {
-                mem::transmute(self.next_u64().to_le())
-            };
-            l.copy_from_slice(&chunk);
-        }
-        let n = left.len();
-        if n > 0 {
-            let chunk: [u8; 8] = unsafe {
-                mem::transmute(self.next_u64().to_le())
-            };
-            left.copy_from_slice(&chunk[..n]);
-        }
+        // Fill using `next_u32`. This is faster for filling small slices (four
+        // bytes or less), while the overhead is negligible.
+        //
+        // This is done especially for wrappers that implement `next_u32`
+        // themselves via `fill_bytes`.
+        impls::fill_bytes_via_next(self, dest)
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
     }
 }
 
-// There are no tests included because (1) this is an "external" RNG, so output
-// is not reproducible and (2) `test_timer` *will* fail on some platforms.
+impl CryptoRng for JitterRng {}
+
+#[cfg(test)]
+mod test_jitter_init {
+    use super::JitterRng;
+
+    #[cfg(all(feature="std", not(target_arch = "wasm32")))]
+    #[test]
+    fn test_jitter_init() {
+        use RngCore;
+        // Because this is a debug build, measurements here are not representive
+        // of the final release build.
+        // Don't fail this test if initializing `JitterRng` fails because of a
+        // bad timer (the timer from the standard library may not have enough
+        // accuracy on all platforms).
+        match JitterRng::new() {
+            Ok(ref mut rng) => {
+                // false positives are possible, but extremely unlikely
+                assert!(rng.next_u32() | rng.next_u32() != 0);
+            },
+            Err(_) => {},
+        }
+    }
+
+    #[test]
+    fn test_jitter_bad_timer() {
+        fn bad_timer() -> u64 { 0 }
+        let mut rng = JitterRng::new_with_timer(bad_timer);
+        assert!(rng.test_timer().is_err());
+    }
+}
diff --git a/rand/src/rngs/mock.rs b/rand/src/rngs/mock.rs
new file mode 100644
index 0000000..3c9a994
--- /dev/null
+++ b/rand/src/rngs/mock.rs
@@ -0,0 +1,59 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Mock random number generator
+
+use rand_core::{RngCore, Error, impls};
+
+/// A simple implementation of `RngCore` for testing purposes.
+/// 
+/// This generates an arithmetic sequence (i.e. adds a constant each step)
+/// over a `u64` number, using wrapping arithmetic. If the increment is 0
+/// the generator yields a constant.
+/// 
+/// ```
+/// use rand::Rng;
+/// use rand::rngs::mock::StepRng;
+/// 
+/// let mut my_rng = StepRng::new(2, 1);
+/// let sample: [u64; 3] = my_rng.gen();
+/// assert_eq!(sample, [2, 3, 4]);
+/// ```
+#[derive(Debug, Clone)]
+pub struct StepRng {
+    v: u64,
+    a: u64,
+}
+
+impl StepRng {
+    /// Create a `StepRng`, yielding an arithmetic sequence starting with
+    /// `initial` and incremented by `increment` each time.
+    pub fn new(initial: u64, increment: u64) -> Self {
+        StepRng { v: initial, a: increment }
+    }
+}
+
+impl RngCore for StepRng {
+    fn next_u32(&mut self) -> u32 {
+        self.next_u64() as u32
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        let result = self.v;
+        self.v = self.v.wrapping_add(self.a);
+        result
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        impls::fill_bytes_via_next(self, dest);
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        Ok(self.fill_bytes(dest))
+    }
+}
diff --git a/rand/src/rngs/mod.rs b/rand/src/rngs/mod.rs
new file mode 100644
index 0000000..70c4506
--- /dev/null
+++ b/rand/src/rngs/mod.rs
@@ -0,0 +1,217 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Random number generators and adapters for common usage:
+//!
+//! - [`ThreadRng`], a fast, secure, auto-seeded thread-local generator
+//! - [`StdRng`] and [`SmallRng`], algorithms to cover typical usage
+//! - [`EntropyRng`], [`OsRng`] and [`JitterRng`] as entropy sources
+//! - [`mock::StepRng`] as a simple counter for tests
+//! - [`adapter::ReadRng`] to read from a file/stream
+//! - [`adapter::ReseedingRng`] to reseed a PRNG on clone / process fork etc.
+//!
+//! # Background — Random number generators (RNGs)
+//!
+//! Computers are inherently deterministic, so to get *random* numbers one
+//! either has to use a hardware generator or collect bits of *entropy* from
+//! various sources (e.g. event timestamps, or jitter). This is a relatively
+//! slow and complicated operation.
+//!
+//! Generally the operating system will collect some entropy, remove bias, and
+//! use that to seed its own PRNG; [`OsRng`] provides an interface to this.
+//! [`JitterRng`] is an entropy collector included with Rand that measures
+//! jitter in the CPU execution time, and jitter in memory access time.
+//! [`EntropyRng`] is a wrapper that uses the best entropy source that is
+//! available.
+//!
+//! ## Pseudo-random number generators
+//!
+//! What is commonly used instead of "true" random number renerators, are
+//! *pseudo-random number generators* (PRNGs), deterministic algorithms that
+//! produce an infinite stream of pseudo-random numbers from a small random
+//! seed. PRNGs are faster, and have better provable properties. The numbers
+//! produced can be statistically of very high quality and can be impossible to
+//! predict. (They can also have obvious correlations and be trivial to predict;
+//! quality varies.)
+//!
+//! There are two different types of PRNGs: those developed for simulations
+//! and statistics, and those developed for use in cryptography; the latter are
+//! called Cryptographically Secure PRNGs (CSPRNG or CPRNG). Both types can
+//! have good statistical quality but the latter also have to be impossible to
+//! predict, even after seeing many previous output values. Rand provides a good
+//! default algorithm from each class:
+//!
+//! - [`SmallRng`] is a PRNG chosen for low memory usage, high performance and
+//!   good statistical quality.
+//! - [`StdRng`] is a CSPRNG chosen for good performance and trust of security
+//!   (based on reviews, maturity and usage). The current algorithm is HC-128,
+//!   which is one of the recommendations by ECRYPT's eSTREAM project.
+//!
+//! The above PRNGs do not cover all use-cases; more algorithms can be found in
+//! the [`prng` module], as well as in several other crates. For example, you
+//! may wish a CSPRNG with significantly lower memory usage than [`StdRng`]
+//! while being less concerned about performance, in which case [`ChaChaRng`]
+//! is a good choice.
+//!
+//! One complexity is that the internal state of a PRNG must change with every
+//! generated number. For APIs this generally means a mutable reference to the
+//! state of the PRNG has to be passed around.
+//!
+//! A solution is [`ThreadRng`]. This is a thread-local implementation of
+//! [`StdRng`] with automatic seeding on first use. It is the best choice if you
+//! "just" want a convenient, secure, fast random number source. Use via the
+//! [`thread_rng`] function, which gets a reference to the current thread's
+//! local instance.
+//!
+//! ## Seeding
+//!
+//! As mentioned above, PRNGs require a random seed in order to produce random
+//! output. This is especially important for CSPRNGs, which are still
+//! deterministic algorithms, thus can only be secure if their seed value is
+//! also secure. To seed a PRNG, use one of:
+//!
+//! - [`FromEntropy::from_entropy`]; this is the most convenient way to seed
+//!   with fresh, secure random data.
+//! - [`SeedableRng::from_rng`]; this allows seeding from another PRNG or
+//!   from an entropy source such as [`EntropyRng`].
+//! - [`SeedableRng::from_seed`]; this is mostly useful if you wish to be able
+//!   to reproduce the output sequence by using a fixed seed. (Don't use
+//!   [`StdRng`] or [`SmallRng`] in this case since different algorithms may be
+//!   used by future versions of Rand; use an algorithm from the
+//!   [`prng` module].)
+//!
+//! ## Conclusion
+//!
+//! - [`thread_rng`] is what you often want to use.
+//! - If you want more control, flexibility, or better performance, use
+//!   [`StdRng`], [`SmallRng`] or an algorithm from the [`prng` module].
+//! - Use [`FromEntropy::from_entropy`] to seed new PRNGs.
+//! - If you need reproducibility, use [`SeedableRng::from_seed`] combined with
+//!   a named PRNG.
+//!
+//! More information and notes on cryptographic security can be found
+//! in the [`prng` module].
+//!
+//! ## Examples
+//!
+//! Examples of seeding PRNGs:
+//!
+//! ```
+//! use rand::prelude::*;
+//! # use rand::Error;
+//!
+//! // StdRng seeded securely by the OS or local entropy collector:
+//! let mut rng = StdRng::from_entropy();
+//! # let v: u32 = rng.gen();
+//!
+//! // SmallRng seeded from thread_rng:
+//! # fn try_inner() -> Result<(), Error> {
+//! let mut rng = SmallRng::from_rng(thread_rng())?;
+//! # let v: u32 = rng.gen();
+//! # Ok(())
+//! # }
+//! # try_inner().unwrap();
+//!
+//! // SmallRng seeded by a constant, for deterministic results:
+//! let seed = [1,2,3,4, 5,6,7,8, 9,10,11,12, 13,14,15,16]; // byte array
+//! let mut rng = SmallRng::from_seed(seed);
+//! # let v: u32 = rng.gen();
+//! ```
+//!
+//!
+//! # Implementing custom RNGs
+//!
+//! If you want to implement custom RNG, see the [`rand_core`] crate. The RNG
+//! will have to implement the [`RngCore`] trait, where the [`Rng`] trait is
+//! build on top of.
+//!
+//! If the RNG needs seeding, also implement the [`SeedableRng`] trait.
+//!
+//! [`CryptoRng`] is a marker trait cryptographically secure PRNGs can
+//! implement.
+//!
+//!
+// This module:
+//! [`ThreadRng`]: struct.ThreadRng.html
+//! [`StdRng`]: struct.StdRng.html
+//! [`SmallRng`]: struct.SmallRng.html
+//! [`EntropyRng`]: struct.EntropyRng.html
+//! [`OsRng`]: struct.OsRng.html
+//! [`JitterRng`]: struct.JitterRng.html
+// Other traits and functions:
+//! [`rand_core`]: https://crates.io/crates/rand_core
+//! [`prng` module]: ../prng/index.html
+//! [`CryptoRng`]: ../trait.CryptoRng.html
+//! [`FromEntropy`]: ../trait.FromEntropy.html
+//! [`FromEntropy::from_entropy`]: ../trait.FromEntropy.html#tymethod.from_entropy
+//! [`RngCore`]: ../trait.RngCore.html
+//! [`Rng`]: ../trait.Rng.html
+//! [`SeedableRng`]: ../trait.SeedableRng.html
+//! [`SeedableRng::from_rng`]: ../trait.SeedableRng.html#tymethod.from_rng
+//! [`SeedableRng::from_seed`]: ../trait.SeedableRng.html#tymethod.from_seed
+//! [`thread_rng`]: ../fn.thread_rng.html
+//! [`mock::StepRng`]: mock/struct.StepRng.html
+//! [`adapter::ReadRng`]: adapter/struct.ReadRng.html
+//! [`adapter::ReseedingRng`]: adapter/struct.ReseedingRng.html
+//! [`ChaChaRng`]: ../../rand_chacha/struct.ChaChaRng.html
+
+pub mod adapter;
+
+#[cfg(feature="std")] mod entropy;
+mod jitter;
+pub mod mock;   // Public so we don't export `StepRng` directly, making it a bit
+                // more clear it is intended for testing.
+mod small;
+mod std;
+#[cfg(feature="std")] pub(crate) mod thread;
+
+
+pub use self::jitter::{JitterRng, TimerError};
+#[cfg(feature="std")] pub use self::entropy::EntropyRng;
+
+pub use self::small::SmallRng;
+pub use self::std::StdRng;
+#[cfg(feature="std")] pub use self::thread::ThreadRng;
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+mod os;
+
+#[cfg(all(feature="std",
+          any(target_os = "linux", target_os = "android",
+              target_os = "netbsd",
+              target_os = "dragonfly",
+              target_os = "haiku",
+              target_os = "emscripten",
+              target_os = "solaris",
+              target_os = "cloudabi",
+              target_os = "macos", target_os = "ios",
+              target_os = "freebsd",
+              target_os = "openbsd", target_os = "bitrig",
+              target_os = "redox",
+              target_os = "fuchsia",
+              windows,
+              all(target_arch = "wasm32", feature = "stdweb"),
+              all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+pub use self::os::OsRng;
diff --git a/rand/src/rngs/os.rs b/rand/src/rngs/os.rs
new file mode 100644
index 0000000..e609c50
--- /dev/null
+++ b/rand/src/rngs/os.rs
@@ -0,0 +1,1275 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2013-2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Interface to the random number generator of the operating system.
+
+use std::fmt;
+use rand_core::{CryptoRng, RngCore, Error, impls};
+
+/// A random number generator that retrieves randomness straight from the
+/// operating system.
+///
+/// This is the preferred external source of entropy for most applications.
+/// Commonly it is used to initialize a user-space RNG, which can then be used
+/// to generate random values with much less overhead than `OsRng`.
+///
+/// You may prefer to use [`EntropyRng`] instead of `OsRng`. It is unlikely, but
+/// not entirely theoretical, for `OsRng` to fail. In such cases [`EntropyRng`]
+/// falls back on a good alternative entropy source.
+///
+/// `OsRng::new()` is guaranteed to be very cheap (after the first successful
+/// call), and will never consume more than one file handle per process.
+///
+/// # Platform sources
+///
+/// | OS               | interface
+/// |------------------|---------------------------------------------------------
+/// | Linux, Android   | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after reading from `/dev/random` once
+/// | Windows          | [`RtlGenRandom`][3]
+/// | macOS, iOS       | [`SecRandomCopyBytes`][4]
+/// | FreeBSD          | [`kern.arandom`][5]
+/// | OpenBSD, Bitrig  | [`getentropy`][6]
+/// | NetBSD           | [`/dev/urandom`][7] after reading from `/dev/random` once
+/// | Dragonfly BSD    | [`/dev/random`][8]
+/// | Solaris, illumos | [`getrandom`][9] system call if available, otherwise [`/dev/random`][10]
+/// | Fuchsia OS       | [`cprng_draw`][11]
+/// | Redox            | [`rand:`][12]
+/// | CloudABI         | [`random_get`][13]
+/// | Haiku            | `/dev/random` (identical to `/dev/urandom`)
+/// | Web browsers     | [`Crypto.getRandomValues`][14] (see [Support for WebAssembly and ams.js][14])
+/// | Node.js          | [`crypto.randomBytes`][15] (see [Support for WebAssembly and ams.js][16])
+///
+/// Rand doesn't have a blanket implementation for all Unix-like operating
+/// systems that reads from `/dev/urandom`. This ensures all supported operating
+/// systems are using the recommended interface and respect maximum buffer
+/// sizes.
+///
+/// ## Support for WebAssembly and ams.js
+///
+/// The three Emscripten targets `asmjs-unknown-emscripten`,
+/// `wasm32-unknown-emscripten` and `wasm32-experimental-emscripten` use
+/// Emscripten's emulation of `/dev/random` on web browsers and Node.js.
+///
+/// The bare Wasm target `wasm32-unknown-unknown` tries to call the javascript
+/// methods directly, using either `stdweb` in combination with `cargo-web` or
+/// `wasm-bindgen` depending on what features are activated for this crate.
+///
+/// ## Early boot
+///
+/// It is possible that early in the boot process the OS hasn't had enough time
+/// yet to collect entropy to securely seed its RNG, especially on virtual
+/// machines.
+///
+/// Some operating systems always block the thread until the RNG is securely
+/// seeded. This can take anywhere from a few seconds to more than a minute.
+/// Others make a best effort to use a seed from before the shutdown and don't
+/// document much.
+///
+/// A few, Linux, NetBSD and Solaris, offer a choice between blocking, and
+/// getting an error. With `try_fill_bytes` we choose to get the error
+/// ([`ErrorKind::NotReady`]), while the other methods use a blocking interface.
+///
+/// On Linux (when the `genrandom` system call is not available) and on NetBSD
+/// reading from `/dev/urandom` never blocks, even when the OS hasn't collected
+/// enough entropy yet. As a countermeasure we try to do a single read from
+/// `/dev/random` until we know the OS RNG is initialized (and store this in a
+/// global static).
+///
+/// # Panics
+///
+/// `OsRng` is extremely unlikely to fail if `OsRng::new()`, and one read from
+/// it, where succesfull. But in case it does fail, only [`try_fill_bytes`] is
+/// able to report the cause. Depending on the error the other [`RngCore`]
+/// methods will retry several times, and panic in case the error remains.
+///
+/// [`EntropyRng`]: struct.EntropyRng.html
+/// [`RngCore`]: ../trait.RngCore.html
+/// [`try_fill_bytes`]: ../trait.RngCore.html#method.tymethod.try_fill_bytes
+/// [`ErrorKind::NotReady`]: ../enum.ErrorKind.html#variant.NotReady
+///
+/// [1]: http://man7.org/linux/man-pages/man2/getrandom.2.html
+/// [2]: http://man7.org/linux/man-pages/man4/urandom.4.html
+/// [3]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
+/// [4]: https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
+/// [5]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
+/// [6]: https://man.openbsd.org/getentropy.2
+/// [7]: http://netbsd.gw.com/cgi-bin/man-cgi?random+4+NetBSD-current
+/// [8]: https://leaf.dragonflybsd.org/cgi/web-man?command=random&section=4
+/// [9]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
+/// [10]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
+/// [11]: https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_draw.md
+/// [12]: https://github.com/redox-os/randd/blob/master/src/main.rs
+/// [13]: https://github.com/NuxiNL/cloudabi/blob/v0.20/cloudabi.txt#L1826
+/// [14]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
+/// [15]: https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback
+/// [16]: #support-for-webassembly-and-amsjs
+
+
+#[derive(Clone)]
+pub struct OsRng(imp::OsRng);
+
+impl fmt::Debug for OsRng {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl OsRng {
+    /// Create a new `OsRng`.
+    pub fn new() -> Result<OsRng, Error> {
+        imp::OsRng::new().map(OsRng)
+    }
+}
+
+impl CryptoRng for OsRng {}
+
+impl RngCore for OsRng {
+    fn next_u32(&mut self) -> u32 {
+        impls::next_u32_via_fill(self)
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_fill(self)
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        use std::{time, thread};
+
+        // We cannot return Err(..), so we try to handle before panicking.
+        const MAX_RETRY_PERIOD: u32 = 10; // max 10s
+        const WAIT_DUR_MS: u32 = 100; // retry every 100ms
+        let wait_dur = time::Duration::from_millis(WAIT_DUR_MS as u64);
+        const RETRY_LIMIT: u32 = (MAX_RETRY_PERIOD * 1000) / WAIT_DUR_MS;
+        const TRANSIENT_RETRIES: u32 = 8;
+        let mut err_count = 0;
+        let mut error_logged = false;
+
+        // Maybe block until the OS RNG is initialized
+        let mut read = 0;
+        if let Ok(n) = self.0.test_initialized(dest, true) { read = n };
+        let dest = &mut dest[read..];
+
+        loop {
+            if let Err(e) = self.try_fill_bytes(dest) {
+                if err_count >= RETRY_LIMIT {
+                    error!("OsRng failed too many times; last error: {}", e);
+                    panic!("OsRng failed too many times; last error: {}", e);
+                }
+
+                if e.kind.should_wait() {
+                    if !error_logged {
+                        warn!("OsRng failed; waiting up to {}s and retrying. Error: {}",
+                                MAX_RETRY_PERIOD, e);
+                        error_logged = true;
+                    }
+                    err_count += 1;
+                    thread::sleep(wait_dur);
+                    continue;
+                } else if e.kind.should_retry() {
+                    if !error_logged {
+                        warn!("OsRng failed; retrying up to {} times. Error: {}",
+                                TRANSIENT_RETRIES, e);
+                        error_logged = true;
+                    }
+                    err_count += (RETRY_LIMIT + TRANSIENT_RETRIES - 1)
+                            / TRANSIENT_RETRIES;    // round up
+                    continue;
+                } else {
+                    error!("OsRng failed: {}", e);
+                    panic!("OsRng fatal error: {}", e);
+                }
+            }
+
+            break;
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        // Some systems do not support reading 0 random bytes.
+        // (And why waste a system call?)
+        if dest.len() == 0 { return Ok(()); }
+
+        let read = self.0.test_initialized(dest, false)?;
+        let dest = &mut dest[read..];
+
+        let max = self.0.max_chunk_size();
+        if dest.len() <= max {
+            trace!("OsRng: reading {} bytes via {}",
+                   dest.len(), self.0.method_str());
+        } else {
+            trace!("OsRng: reading {} bytes via {} in {} chunks of {} bytes",
+                   dest.len(), self.0.method_str(), (dest.len() + max) / max, max);
+        }
+        for slice in dest.chunks_mut(max) {
+            self.0.fill_chunk(slice)?;
+        }
+        Ok(())
+    }
+}
+
+trait OsRngImpl where Self: Sized {
+    // Create a new `OsRng` platform interface.
+    fn new() -> Result<Self, Error>;
+
+    // Fill a chunk with random bytes.
+    fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error>;
+
+    // Test whether the OS RNG is initialized. This method may not be possible
+    // to support cheaply (or at all) on all operating systems.
+    //
+    // If `blocking` is set, this will cause the OS the block execution until
+    // its RNG is initialized.
+    //
+    // Random values that are read while this are stored in `dest`, the amount
+    // of read bytes is returned.
+    fn test_initialized(&mut self, _dest: &mut [u8], _blocking: bool)
+        -> Result<usize, Error> { Ok(0) }
+
+    // Maximum chunk size supported.
+    fn max_chunk_size(&self) -> usize { ::core::usize::MAX }
+
+    // Name of the OS interface (used for logging).
+    fn method_str(&self) -> &'static str;
+}
+
+
+
+
+// Helper functions to read from a random device such as `/dev/urandom`.
+//
+// All instances use a single internal file handle, to prevent possible
+// exhaustion of file descriptors.
+#[cfg(any(target_os = "linux", target_os = "android",
+          target_os = "netbsd", target_os = "dragonfly",
+          target_os = "solaris", target_os = "redox",
+          target_os = "haiku", target_os = "emscripten"))]
+mod random_device {
+    use {Error, ErrorKind};
+    use std::fs::File;
+    use std::io;
+    use std::io::Read;
+    use std::sync::{Once, Mutex, ONCE_INIT};
+
+    // TODO: remove outer Option when `Mutex::new(None)` is a constant expression
+    static mut READ_RNG_FILE: Option<Mutex<Option<File>>> = None;
+    static READ_RNG_ONCE: Once = ONCE_INIT;
+
+    #[allow(unused)]
+    pub fn open<F>(path: &'static str, open_fn: F) -> Result<(), Error>
+        where F: Fn(&'static str) -> Result<File, io::Error>
+    {
+        READ_RNG_ONCE.call_once(|| {
+            unsafe { READ_RNG_FILE = Some(Mutex::new(None)) }
+        });
+
+        // We try opening the file outside the `call_once` fn because we cannot
+        // clone the error, thus we must retry on failure.
+
+        let mutex = unsafe { READ_RNG_FILE.as_ref().unwrap() };
+        let mut guard = mutex.lock().unwrap();
+        if (*guard).is_none() {
+            info!("OsRng: opening random device {}", path);
+            let file = open_fn(path).map_err(map_err)?;
+            *guard = Some(file);
+        };
+        Ok(())
+    }
+
+    pub fn read(dest: &mut [u8]) -> Result<(), Error> {
+        // We expect this function only to be used after `random_device::open`
+        // was succesful. Therefore we can assume that our memory was set with a
+        // valid object.
+        let mutex = unsafe { READ_RNG_FILE.as_ref().unwrap() };
+        let mut guard = mutex.lock().unwrap();
+        let file = (*guard).as_mut().unwrap();
+
+        // Use `std::io::read_exact`, which retries on `ErrorKind::Interrupted`.
+        file.read_exact(dest).map_err(|err| {
+            Error::with_cause(ErrorKind::Unavailable,
+                              "error reading random device", err)
+        })
+
+    }
+
+    pub fn map_err(err: io::Error) -> Error {
+        match err.kind() {
+            io::ErrorKind::Interrupted =>
+                    Error::new(ErrorKind::Transient, "interrupted"),
+            io::ErrorKind::WouldBlock =>
+                    Error::with_cause(ErrorKind::NotReady,
+                    "OS RNG not yet seeded", err),
+            _ => Error::with_cause(ErrorKind::Unavailable,
+                    "error while opening random device", err)
+        }
+    }
+}
+
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+mod imp {
+    extern crate libc;
+
+    use {Error, ErrorKind};
+    use super::random_device;
+    use super::OsRngImpl;
+
+    use std::io;
+    use std::io::Read;
+    use std::fs::{File, OpenOptions};
+    use std::os::unix::fs::OpenOptionsExt;
+    use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+    use std::sync::{Once, ONCE_INIT};
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng {
+        method: OsRngMethod,
+        initialized: bool,
+    }
+
+    #[derive(Clone, Debug)]
+    enum OsRngMethod {
+        GetRandom,
+        RandomDevice,
+    }
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            if is_getrandom_available() {
+                return Ok(OsRng { method: OsRngMethod::GetRandom,
+                                  initialized: false });
+            }
+            random_device::open("/dev/urandom", &|p| File::open(p))?;
+            Ok(OsRng { method: OsRngMethod::RandomDevice, initialized: false })
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            match self.method {
+                OsRngMethod::GetRandom => getrandom_try_fill(dest, false),
+                OsRngMethod::RandomDevice => random_device::read(dest),
+            }
+        }
+
+        fn test_initialized(&mut self, dest: &mut [u8], blocking: bool)
+            -> Result<usize, Error>
+        {
+            static OS_RNG_INITIALIZED: AtomicBool = ATOMIC_BOOL_INIT;
+            if !self.initialized {
+                self.initialized = OS_RNG_INITIALIZED.load(Ordering::Relaxed);
+            }
+            if self.initialized { return Ok(0); }
+
+            let result = match self.method {
+                OsRngMethod::GetRandom => {
+                    getrandom_try_fill(dest, blocking)?;
+                    Ok(dest.len())
+                }
+                OsRngMethod::RandomDevice => {
+                    info!("OsRng: testing random device /dev/random");
+                    let mut file = OpenOptions::new()
+                        .read(true)
+                        .custom_flags(if blocking { 0 } else { libc::O_NONBLOCK })
+                        .open("/dev/random")
+                        .map_err(random_device::map_err)?;
+                    file.read(&mut dest[..1]).map_err(random_device::map_err)?;
+                    Ok(1)
+                }
+            };
+            OS_RNG_INITIALIZED.store(true, Ordering::Relaxed);
+            self.initialized = true;
+            result
+        }
+
+        fn method_str(&self) -> &'static str {
+            match self.method {
+                OsRngMethod::GetRandom => "getrandom",
+                OsRngMethod::RandomDevice => "/dev/urandom",
+            }
+        }
+    }
+
+    #[cfg(target_arch = "x86_64")]
+    const NR_GETRANDOM: libc::c_long = 318;
+    #[cfg(target_arch = "x86")]
+    const NR_GETRANDOM: libc::c_long = 355;
+    #[cfg(target_arch = "arm")]
+    const NR_GETRANDOM: libc::c_long = 384;
+    #[cfg(target_arch = "aarch64")]
+    const NR_GETRANDOM: libc::c_long = 278;
+     #[cfg(target_arch = "s390x")]
+    const NR_GETRANDOM: libc::c_long = 349;
+    #[cfg(target_arch = "powerpc")]
+    const NR_GETRANDOM: libc::c_long = 359;
+    #[cfg(target_arch = "powerpc64")]
+    const NR_GETRANDOM: libc::c_long = 359;
+    #[cfg(target_arch = "mips")] // old ABI
+    const NR_GETRANDOM: libc::c_long = 4353;
+    #[cfg(target_arch = "mips64")]
+    const NR_GETRANDOM: libc::c_long = 5313;
+    #[cfg(target_arch = "sparc")]
+    const NR_GETRANDOM: libc::c_long = 347;
+    #[cfg(target_arch = "sparc64")]
+    const NR_GETRANDOM: libc::c_long = 347;
+    #[cfg(not(any(target_arch = "x86_64", target_arch = "x86",
+                  target_arch = "arm", target_arch = "aarch64",
+                  target_arch = "s390x", target_arch = "powerpc",
+                  target_arch = "powerpc64", target_arch = "mips",
+                  target_arch = "mips64", target_arch = "sparc",
+                  target_arch = "sparc64")))]
+    const NR_GETRANDOM: libc::c_long = 0;
+
+    fn getrandom(buf: &mut [u8], blocking: bool) -> libc::c_long {
+        const GRND_NONBLOCK: libc::c_uint = 0x0001;
+
+        if NR_GETRANDOM == 0 { return -1 };
+
+        unsafe {
+            libc::syscall(NR_GETRANDOM, buf.as_mut_ptr(), buf.len(),
+                          if blocking { 0 } else { GRND_NONBLOCK })
+        }
+    }
+
+    fn getrandom_try_fill(dest: &mut [u8], blocking: bool) -> Result<(), Error> {
+        let mut read = 0;
+        while read < dest.len() {
+            let result = getrandom(&mut dest[read..], blocking);
+            if result == -1 {
+                let err = io::Error::last_os_error();
+                let kind = err.kind();
+                if kind == io::ErrorKind::Interrupted {
+                    continue;
+                } else if kind == io::ErrorKind::WouldBlock {
+                    return Err(Error::with_cause(
+                        ErrorKind::NotReady,
+                        "getrandom not ready",
+                        err,
+                    ));
+                } else {
+                    return Err(Error::with_cause(
+                        ErrorKind::Unavailable,
+                        "unexpected getrandom error",
+                        err,
+                    ));
+                }
+            } else {
+                read += result as usize;
+            }
+        }
+        Ok(())
+    }
+
+    fn is_getrandom_available() -> bool {
+        static CHECKER: Once = ONCE_INIT;
+        static AVAILABLE: AtomicBool = ATOMIC_BOOL_INIT;
+
+        if NR_GETRANDOM == 0 { return false };
+
+        CHECKER.call_once(|| {
+            debug!("OsRng: testing getrandom");
+            let mut buf: [u8; 0] = [];
+            let result = getrandom(&mut buf, false);
+            let available = if result == -1 {
+                let err = io::Error::last_os_error().raw_os_error();
+                err != Some(libc::ENOSYS)
+            } else {
+                true
+            };
+            AVAILABLE.store(available, Ordering::Relaxed);
+            info!("OsRng: using {}", if available { "getrandom" } else { "/dev/urandom" });
+        });
+
+        AVAILABLE.load(Ordering::Relaxed)
+    }
+}
+
+
+#[cfg(target_os = "netbsd")]
+mod imp {
+    use Error;
+    use super::random_device;
+    use super::OsRngImpl;
+
+    use std::fs::File;
+    use std::io::Read;
+    use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng { initialized: bool }
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            random_device::open("/dev/urandom", &|p| File::open(p))?;
+            Ok(OsRng { initialized: false })
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            random_device::read(dest)
+        }
+
+        // Read a single byte from `/dev/random` to determine if the OS RNG is
+        // already seeded. NetBSD always blocks if not yet ready.
+        fn test_initialized(&mut self, dest: &mut [u8], _blocking: bool)
+            -> Result<usize, Error>
+        {
+            static OS_RNG_INITIALIZED: AtomicBool = ATOMIC_BOOL_INIT;
+            if !self.initialized {
+                self.initialized = OS_RNG_INITIALIZED.load(Ordering::Relaxed);
+            }
+            if self.initialized { return Ok(0); }
+
+            info!("OsRng: testing random device /dev/random");
+            let mut file =
+                File::open("/dev/random").map_err(random_device::map_err)?;
+            file.read(&mut dest[..1]).map_err(random_device::map_err)?;
+
+            OS_RNG_INITIALIZED.store(true, Ordering::Relaxed);
+            self.initialized = true;
+            Ok(1)
+        }
+
+        fn method_str(&self) -> &'static str { "/dev/urandom" }
+    }
+}
+
+
+#[cfg(any(target_os = "dragonfly",
+          target_os = "haiku",
+          target_os = "emscripten"))]
+mod imp {
+    use Error;
+    use super::random_device;
+    use super::OsRngImpl;
+    use std::fs::File;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng();
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            random_device::open("/dev/random", &|p| File::open(p))?;
+            Ok(OsRng())
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            random_device::read(dest)
+        }
+
+        #[cfg(target_os = "emscripten")]
+        fn max_chunk_size(&self) -> usize {
+            // `Crypto.getRandomValues` documents `dest` should be at most 65536
+            // bytes. `crypto.randomBytes` documents: "To minimize threadpool
+            // task length variation, partition large randomBytes requests when
+            // doing so as part of fulfilling a client request.
+            65536
+        }
+
+        fn method_str(&self) -> &'static str { "/dev/random" }
+    }
+}
+
+
+// Read from `/dev/random`, with chunks of limited size (1040 bytes).
+// `/dev/random` uses the Hash_DRBG with SHA512 algorithm from NIST SP 800-90A.
+// `/dev/urandom` uses the FIPS 186-2 algorithm, which is considered less
+// secure. We choose to read from `/dev/random`.
+//
+// Since Solaris 11.3 the `getrandom` syscall is available. To make sure we can
+// compile on both Solaris and on OpenSolaris derivatives, that do not have the
+// function, we do a direct syscall instead of calling a library function.
+//
+// We have no way to differentiate between Solaris, illumos, SmartOS, etc.
+#[cfg(target_os = "solaris")]
+mod imp {
+    extern crate libc;
+
+    use {Error, ErrorKind};
+    use super::random_device;
+    use super::OsRngImpl;
+
+    use std::io;
+    use std::io::Read;
+    use std::fs::{File, OpenOptions};
+    use std::os::unix::fs::OpenOptionsExt;
+    use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng {
+        method: OsRngMethod,
+        initialized: bool,
+    }
+
+    #[derive(Clone, Debug)]
+    enum OsRngMethod {
+        GetRandom,
+        RandomDevice,
+    }
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            if is_getrandom_available() {
+                return Ok(OsRng { method: OsRngMethod::GetRandom,
+                                  initialized: false });
+            }
+            let open = |p| OpenOptions::new()
+                .read(true)
+                .custom_flags(libc::O_NONBLOCK)
+                .open(p);
+            random_device::open("/dev/random", &open)?;
+            Ok(OsRng { method: OsRngMethod::RandomDevice, initialized: false })
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            match self.method {
+                OsRngMethod::GetRandom => getrandom_try_fill(dest, false),
+                OsRngMethod::RandomDevice => random_device::read(dest),
+            }
+        }
+
+        fn test_initialized(&mut self, dest: &mut [u8], blocking: bool)
+            -> Result<usize, Error>
+        {
+            static OS_RNG_INITIALIZED: AtomicBool = ATOMIC_BOOL_INIT;
+            if !self.initialized {
+                self.initialized = OS_RNG_INITIALIZED.load(Ordering::Relaxed);
+            }
+            if self.initialized { return Ok(0); }
+
+            let chunk_len = ::core::cmp::min(1024, dest.len());
+            let dest = &mut dest[..chunk_len];
+
+            match self.method {
+                OsRngMethod::GetRandom => getrandom_try_fill(dest, blocking)?,
+                OsRngMethod::RandomDevice => {
+                    if blocking {
+                        info!("OsRng: testing random device /dev/random");
+                        // We already have a non-blocking handle, but now need a
+                        // blocking one. Not much choice except opening it twice
+                        let mut file = File::open("/dev/random")
+                            .map_err(random_device::map_err)?;
+                        file.read(dest).map_err(random_device::map_err)?;
+                    } else {
+                        self.fill_chunk(dest)?;
+                    }
+                }
+            };
+            OS_RNG_INITIALIZED.store(true, Ordering::Relaxed);
+            self.initialized = true;
+            Ok(chunk_len)
+        }
+
+        fn max_chunk_size(&self) -> usize {
+            // The documentation says 1024 is the maximum for getrandom, but
+            // 1040 for /dev/random.
+            1024
+        }
+
+        fn method_str(&self) -> &'static str {
+            match self.method {
+                OsRngMethod::GetRandom => "getrandom",
+                OsRngMethod::RandomDevice => "/dev/random",
+            }
+        }
+    }
+
+    fn getrandom(buf: &mut [u8], blocking: bool) -> libc::c_long {
+        extern "C" {
+            fn syscall(number: libc::c_long, ...) -> libc::c_long;
+        }
+
+        const SYS_GETRANDOM: libc::c_long = 143;
+        const GRND_NONBLOCK: libc::c_uint = 0x0001;
+        const GRND_RANDOM: libc::c_uint = 0x0002;
+
+        unsafe {
+            syscall(SYS_GETRANDOM, buf.as_mut_ptr(), buf.len(),
+                    if blocking { 0 } else { GRND_NONBLOCK } | GRND_RANDOM)
+        }
+    }
+
+    fn getrandom_try_fill(dest: &mut [u8], blocking: bool) -> Result<(), Error> {
+        let result = getrandom(dest, blocking);
+        if result == -1 || result == 0 {
+            let err = io::Error::last_os_error();
+            let kind = err.kind();
+            if kind == io::ErrorKind::WouldBlock {
+                return Err(Error::with_cause(
+                    ErrorKind::NotReady,
+                    "getrandom not ready",
+                    err,
+                ));
+            } else {
+                return Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "unexpected getrandom error",
+                    err,
+                ));
+            }
+        } else if result != dest.len() as i64 {
+            return Err(Error::new(ErrorKind::Unavailable,
+                                  "unexpected getrandom error"));
+        }
+        Ok(())
+    }
+
+    fn is_getrandom_available() -> bool {
+        use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+        use std::sync::{Once, ONCE_INIT};
+
+        static CHECKER: Once = ONCE_INIT;
+        static AVAILABLE: AtomicBool = ATOMIC_BOOL_INIT;
+
+        CHECKER.call_once(|| {
+            debug!("OsRng: testing getrandom");
+            let mut buf: [u8; 0] = [];
+            let result = getrandom(&mut buf, false);
+            let available = if result == -1 {
+                let err = io::Error::last_os_error().raw_os_error();
+                err != Some(libc::ENOSYS)
+            } else {
+                true
+            };
+            AVAILABLE.store(available, Ordering::Relaxed);
+            info!("OsRng: using {}", if available { "getrandom" } else { "/dev/random" });
+        });
+
+        AVAILABLE.load(Ordering::Relaxed)
+    }
+}
+
+
+#[cfg(target_os = "cloudabi")]
+mod imp {
+    extern crate cloudabi;
+
+    use std::io;
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let errno = unsafe { cloudabi::random_get(dest) };
+            if errno == cloudabi::errno::SUCCESS {
+                Ok(())
+            } else {
+                // Cloudlibc provides its own `strerror` implementation so we
+                // can use `from_raw_os_error` here.
+                Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "random_get() system call failed",
+                    io::Error::from_raw_os_error(errno as i32),
+                ))
+            }
+        }
+
+        fn method_str(&self) -> &'static str { "cloudabi::random_get" }
+    }
+}
+
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
+mod imp {
+    extern crate libc;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    use std::io;
+    use self::libc::{c_int, size_t};
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    enum SecRandom {}
+
+    #[allow(non_upper_case_globals)]
+    const kSecRandomDefault: *const SecRandom = 0 as *const SecRandom;
+
+    #[link(name = "Security", kind = "framework")]
+    extern {
+        fn SecRandomCopyBytes(rnd: *const SecRandom,
+                              count: size_t, bytes: *mut u8) -> c_int;
+    }
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let ret = unsafe {
+                SecRandomCopyBytes(kSecRandomDefault,
+                                   dest.len() as size_t,
+                                   dest.as_mut_ptr())
+            };
+            if ret == -1 {
+                Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "couldn't generate random bytes",
+                    io::Error::last_os_error()))
+            } else {
+                Ok(())
+            }
+        }
+
+        fn method_str(&self) -> &'static str { "SecRandomCopyBytes" }
+    }
+}
+
+
+#[cfg(target_os = "freebsd")]
+mod imp {
+    extern crate libc;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    use std::ptr;
+    use std::io;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let mib = [libc::CTL_KERN, libc::KERN_ARND];
+            let mut len = dest.len();
+            let ret = unsafe {
+                libc::sysctl(mib.as_ptr(), mib.len() as libc::c_uint,
+                             dest.as_mut_ptr() as *mut _, &mut len,
+                             ptr::null(), 0)
+            };
+            if ret == -1 || len != dest.len() {
+                return Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "kern.arandom sysctl failed",
+                    io::Error::last_os_error()));
+            }
+            Ok(())
+        }
+
+        fn max_chunk_size(&self) -> usize { 256 }
+
+        fn method_str(&self) -> &'static str { "kern.arandom" }
+    }
+}
+
+
+#[cfg(any(target_os = "openbsd", target_os = "bitrig"))]
+mod imp {
+    extern crate libc;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    use std::io;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let ret = unsafe {
+                libc::getentropy(dest.as_mut_ptr() as *mut libc::c_void, dest.len())
+            };
+            if ret == -1 {
+                return Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "getentropy failed",
+                    io::Error::last_os_error()));
+            }
+            Ok(())
+        }
+
+        fn max_chunk_size(&self) -> usize { 256 }
+
+        fn method_str(&self) -> &'static str { "getentropy" }
+    }
+}
+
+
+#[cfg(target_os = "redox")]
+mod imp {
+    use Error;
+    use super::random_device;
+    use super::OsRngImpl;
+    use std::fs::File;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng();
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            random_device::open("rand:", &|p| File::open(p))?;
+            Ok(OsRng())
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            random_device::read(dest)
+        }
+
+        fn method_str(&self) -> &'static str { "'rand:'" }
+    }
+}
+
+
+#[cfg(target_os = "fuchsia")]
+mod imp {
+    extern crate fuchsia_zircon;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let mut read = 0;
+            while read < dest.len() {
+                match fuchsia_zircon::cprng_draw(&mut dest[read..]) {
+                    Ok(actual) => read += actual,
+                    Err(e) => {
+                        return Err(Error::with_cause(
+                            ErrorKind::Unavailable,
+                            "cprng_draw failed",
+                            e.into_io_error()));
+                    }
+                };
+            }
+            Ok(())
+        }
+
+        fn max_chunk_size(&self) -> usize {
+            fuchsia_zircon::sys::ZX_CPRNG_DRAW_MAX_LEN
+        }
+
+        fn method_str(&self) -> &'static str { "cprng_draw" }
+    }
+}
+
+
+#[cfg(windows)]
+mod imp {
+    extern crate winapi;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    use std::io;
+
+    use self::winapi::shared::minwindef::ULONG;
+    use self::winapi::um::ntsecapi::RtlGenRandom;
+    use self::winapi::um::winnt::PVOID;
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng;
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> { Ok(OsRng) }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            let ret = unsafe {
+                RtlGenRandom(dest.as_mut_ptr() as PVOID, dest.len() as ULONG)
+            };
+            if ret == 0 {
+                return Err(Error::with_cause(
+                    ErrorKind::Unavailable,
+                    "couldn't generate random bytes",
+                    io::Error::last_os_error()));
+            }
+            Ok(())
+        }
+
+        fn max_chunk_size(&self) -> usize { <ULONG>::max_value() as usize }
+
+        fn method_str(&self) -> &'static str { "RtlGenRandom" }
+    }
+}
+
+
+#[cfg(all(target_arch = "wasm32",
+          not(target_os = "emscripten"),
+          feature = "stdweb"))]
+mod imp {
+    use std::mem;
+    use stdweb::unstable::TryInto;
+    use stdweb::web::error::Error as WebError;
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    #[derive(Clone, Debug)]
+    enum OsRngMethod {
+        Browser,
+        Node
+    }
+
+    #[derive(Clone, Debug)]
+    pub struct OsRng(OsRngMethod);
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            let result = js! {
+                try {
+                    if (
+                        typeof self === "object" &&
+                        typeof self.crypto === "object" &&
+                        typeof self.crypto.getRandomValues === "function"
+                    ) {
+                        return { success: true, ty: 1 };
+                    }
+
+                    if (typeof require("crypto").randomBytes === "function") {
+                        return { success: true, ty: 2 };
+                    }
+
+                    return { success: false, error: new Error("not supported") };
+                } catch(err) {
+                    return { success: false, error: err };
+                }
+            };
+
+            if js!{ return @{ result.as_ref() }.success } == true {
+                let ty = js!{ return @{ result }.ty };
+
+                if ty == 1 { Ok(OsRng(OsRngMethod::Browser)) }
+                else if ty == 2 { Ok(OsRng(OsRngMethod::Node)) }
+                else { unreachable!() }
+            } else {
+                let err: WebError = js!{ return @{ result }.error }.try_into().unwrap();
+                Err(Error::with_cause(ErrorKind::Unavailable, "WASM Error", err))
+            }
+        }
+
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            assert_eq!(mem::size_of::<usize>(), 4);
+
+            let len = dest.len() as u32;
+            let ptr = dest.as_mut_ptr() as i32;
+
+            let result = match self.0 {
+                OsRngMethod::Browser => js! {
+                    try {
+                        let array = new Uint8Array(@{ len });
+                        self.crypto.getRandomValues(array);
+                        HEAPU8.set(array, @{ ptr });
+
+                        return { success: true };
+                    } catch(err) {
+                        return { success: false, error: err };
+                    }
+                },
+                OsRngMethod::Node => js! {
+                    try {
+                        let bytes = require("crypto").randomBytes(@{ len });
+                        HEAPU8.set(new Uint8Array(bytes), @{ ptr });
+
+                        return { success: true };
+                    } catch(err) {
+                        return { success: false, error: err };
+                    }
+                }
+            };
+
+            if js!{ return @{ result.as_ref() }.success } == true {
+                Ok(())
+            } else {
+                let err: WebError = js!{ return @{ result }.error }.try_into().unwrap();
+                Err(Error::with_cause(ErrorKind::Unexpected, "WASM Error", err))
+            }
+        }
+
+        fn max_chunk_size(&self) -> usize { 65536 }
+
+        fn method_str(&self) -> &'static str {
+            match self.0 {
+                OsRngMethod::Browser => "Crypto.getRandomValues",
+                OsRngMethod::Node => "crypto.randomBytes",
+            }
+        }
+    }
+}
+
+#[cfg(all(target_arch = "wasm32",
+          not(target_os = "emscripten"),
+          not(feature = "stdweb"),
+          feature = "wasm-bindgen"))]
+mod imp {
+    use __wbg_shims::*;
+
+    use {Error, ErrorKind};
+    use super::OsRngImpl;
+
+    #[derive(Clone, Debug)]
+    pub enum OsRng {
+        Node(NodeCrypto),
+        Browser(BrowserCrypto),
+    }
+
+    impl OsRngImpl for OsRng {
+        fn new() -> Result<OsRng, Error> {
+            // First up we need to detect if we're running in node.js or a
+            // browser. To do this we get ahold of the `this` object (in a bit
+            // of a roundabout fashion).
+            //
+            // Once we have `this` we look at its `self` property, which is
+            // only defined on the web (either a main window or web worker).
+            let this = Function::new("return this").call(&JsValue::undefined());
+            assert!(this != JsValue::undefined());
+            let this = This::from(this);
+            let is_browser = this.self_() != JsValue::undefined();
+
+            if !is_browser {
+                return Ok(OsRng::Node(node_require("crypto")))
+            }
+
+            // If `self` is defined then we're in a browser somehow (main window
+            // or web worker). Here we want to try to use
+            // `crypto.getRandomValues`, but if `crypto` isn't defined we assume
+            // we're in an older web browser and the OS RNG isn't available.
+            let crypto = this.crypto();
+            if crypto.is_undefined() {
+                let msg = "self.crypto is undefined";
+                return Err(Error::new(ErrorKind::Unavailable, msg))
+            }
+
+            // Test if `crypto.getRandomValues` is undefined as well
+            let crypto: BrowserCrypto = crypto.into();
+            if crypto.get_random_values_fn().is_undefined() {
+                let msg = "crypto.getRandomValues is undefined";
+                return Err(Error::new(ErrorKind::Unavailable, msg))
+            }
+
+            // Ok! `self.crypto.getRandomValues` is a defined value, so let's
+            // assume we can do browser crypto.
+            Ok(OsRng::Browser(crypto))
+        }
+
+        fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            match *self {
+                OsRng::Node(ref n) => n.random_fill_sync(dest),
+                OsRng::Browser(ref n) => n.get_random_values(dest),
+            }
+            Ok(())
+        }
+
+        fn max_chunk_size(&self) -> usize {
+            match *self {
+                OsRng::Node(_) => usize::max_value(),
+                OsRng::Browser(_) => {
+                    // see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
+                    //
+                    // where it says:
+                    //
+                    // > A QuotaExceededError DOMException is thrown if the
+                    // > requested length is greater than 65536 bytes.
+                    65536
+                }
+            }
+        }
+
+        fn method_str(&self) -> &'static str {
+            match *self {
+                OsRng::Node(_) => "crypto.randomFillSync",
+                OsRng::Browser(_) => "crypto.getRandomValues",
+            }
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod test {
+    use RngCore;
+    use super::OsRng;
+
+    #[test]
+    fn test_os_rng() {
+        let mut r = OsRng::new().unwrap();
+
+        r.next_u32();
+        r.next_u64();
+
+        let mut v1 = [0u8; 1000];
+        r.fill_bytes(&mut v1);
+
+        let mut v2 = [0u8; 1000];
+        r.fill_bytes(&mut v2);
+
+        let mut n_diff_bits = 0;
+        for i in 0..v1.len() {
+            n_diff_bits += (v1[i] ^ v2[i]).count_ones();
+        }
+
+        // Check at least 1 bit per byte differs. p(failure) < 1e-1000 with random input.
+        assert!(n_diff_bits >= v1.len() as u32);
+    }
+
+    #[test]
+    fn test_os_rng_empty() {
+        let mut r = OsRng::new().unwrap();
+
+        let mut empty = [0u8; 0];
+        r.fill_bytes(&mut empty);
+    }
+
+    #[test]
+    fn test_os_rng_huge() {
+        let mut r = OsRng::new().unwrap();
+
+        let mut huge = [0u8; 100_000];
+        r.fill_bytes(&mut huge);
+    }
+
+    #[cfg(not(any(target_arch = "wasm32", target_arch = "asmjs")))]
+    #[test]
+    fn test_os_rng_tasks() {
+        use std::sync::mpsc::channel;
+        use std::thread;
+
+        let mut txs = vec!();
+        for _ in 0..20 {
+            let (tx, rx) = channel();
+            txs.push(tx);
+
+            thread::spawn(move|| {
+                // wait until all the tasks are ready to go.
+                rx.recv().unwrap();
+
+                // deschedule to attempt to interleave things as much
+                // as possible (XXX: is this a good test?)
+                let mut r = OsRng::new().unwrap();
+                thread::yield_now();
+                let mut v = [0u8; 1000];
+
+                for _ in 0..100 {
+                    r.next_u32();
+                    thread::yield_now();
+                    r.next_u64();
+                    thread::yield_now();
+                    r.fill_bytes(&mut v);
+                    thread::yield_now();
+                }
+            });
+        }
+
+        // start all the tasks
+        for tx in txs.iter() {
+            tx.send(()).unwrap();
+        }
+    }
+}
diff --git a/rand/src/rngs/small.rs b/rand/src/rngs/small.rs
new file mode 100644
index 0000000..e74a83e
--- /dev/null
+++ b/rand/src/rngs/small.rs
@@ -0,0 +1,105 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A small fast RNG
+
+use {RngCore, SeedableRng, Error};
+
+#[cfg(all(rust_1_26, target_pointer_width = "64"))]
+type Rng = ::rand_pcg::Pcg64Mcg;
+#[cfg(not(all(rust_1_26, target_pointer_width = "64")))]
+type Rng = ::rand_pcg::Pcg32;
+
+/// An RNG recommended when small state, cheap initialization and good
+/// performance are required. The PRNG algorithm in `SmallRng` is chosen to be
+/// efficient on the current platform, **without consideration for cryptography
+/// or security**. The size of its state is much smaller than for [`StdRng`].
+///
+/// Reproducibility of output from this generator is however not required, thus
+/// future library versions may use a different internal generator with
+/// different output. Further, this generator may not be portable and can
+/// produce different output depending on the architecture. If you require
+/// reproducible output, use a named RNG. Refer to the documentation on the
+/// [`prng` module](../prng/index.html).
+///
+/// The current algorithm is [`Pcg64Mcg`] on 64-bit platforms with Rust version
+/// 1.26 and later, or [`Pcg32`] otherwise.
+///
+/// # Examples
+///
+/// Initializing `SmallRng` with a random seed can be done using [`FromEntropy`]:
+///
+/// ```
+/// # use rand::Rng;
+/// use rand::FromEntropy;
+/// use rand::rngs::SmallRng;
+///
+/// // Create small, cheap to initialize and fast RNG with a random seed.
+/// // The randomness is supplied by the operating system.
+/// let mut small_rng = SmallRng::from_entropy();
+/// # let v: u32 = small_rng.gen();
+/// ```
+///
+/// When initializing a lot of `SmallRng`'s, using [`thread_rng`] can be more
+/// efficient:
+///
+/// ```
+/// use std::iter;
+/// use rand::{SeedableRng, thread_rng};
+/// use rand::rngs::SmallRng;
+///
+/// // Create a big, expensive to initialize and slower, but unpredictable RNG.
+/// // This is cached and done only once per thread.
+/// let mut thread_rng = thread_rng();
+/// // Create small, cheap to initialize and fast RNGs with random seeds.
+/// // One can generally assume this won't fail.
+/// let rngs: Vec<SmallRng> = iter::repeat(())
+///     .map(|()| SmallRng::from_rng(&mut thread_rng).unwrap())
+///     .take(10)
+///     .collect();
+/// ```
+///
+/// [`FromEntropy`]: ../trait.FromEntropy.html
+/// [`StdRng`]: struct.StdRng.html
+/// [`thread_rng`]: ../fn.thread_rng.html
+/// [`Pcg64Mcg`]: ../../rand_pcg/type.Pcg64Mcg.html
+/// [`Pcg32`]: ../../rand_pcg/type.Pcg32.html
+#[derive(Clone, Debug)]
+pub struct SmallRng(Rng);
+
+impl RngCore for SmallRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for SmallRng {
+    type Seed = <Rng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        SmallRng(Rng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        Rng::from_rng(rng).map(SmallRng)
+    }
+}
diff --git a/rand/src/rngs/std.rs b/rand/src/rngs/std.rs
new file mode 100644
index 0000000..ce1658b
--- /dev/null
+++ b/rand/src/rngs/std.rs
@@ -0,0 +1,81 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The standard RNG
+
+use {RngCore, CryptoRng, Error, SeedableRng};
+use rand_hc::Hc128Rng;
+
+/// The standard RNG. The PRNG algorithm in `StdRng` is chosen to be efficient
+/// on the current platform, to be statistically strong and unpredictable
+/// (meaning a cryptographically secure PRNG).
+///
+/// The current algorithm used on all platforms is [HC-128].
+///
+/// Reproducibility of output from this generator is however not required, thus
+/// future library versions may use a different internal generator with
+/// different output. Further, this generator may not be portable and can
+/// produce different output depending on the architecture. If you require
+/// reproducible output, use a named RNG, for example [`ChaChaRng`].
+///
+/// [HC-128]: ../../rand_hc/struct.Hc128Rng.html
+/// [`ChaChaRng`]: ../../rand_chacha/struct.ChaChaRng.html
+#[derive(Clone, Debug)]
+pub struct StdRng(Hc128Rng);
+
+impl RngCore for StdRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        self.0.next_u32()
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        self.0.next_u64()
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        self.0.fill_bytes(dest);
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        self.0.try_fill_bytes(dest)
+    }
+}
+
+impl SeedableRng for StdRng {
+    type Seed = <Hc128Rng as SeedableRng>::Seed;
+
+    fn from_seed(seed: Self::Seed) -> Self {
+        StdRng(Hc128Rng::from_seed(seed))
+    }
+
+    fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
+        Hc128Rng::from_rng(rng).map(StdRng)
+    }
+}
+
+impl CryptoRng for StdRng {}
+
+
+#[cfg(test)]
+mod test {
+    use {RngCore, SeedableRng};
+    use rngs::StdRng;
+
+    #[test]
+    fn test_stdrng_construction() {
+        let seed = [1,0,0,0, 23,0,0,0, 200,1,0,0, 210,30,0,0,
+                    0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0];
+        let mut rng1 = StdRng::from_seed(seed);
+        assert_eq!(rng1.next_u64(), 15759097995037006553);
+
+        let mut rng2 = StdRng::from_rng(rng1).unwrap();
+        assert_eq!(rng2.next_u64(), 6766915756997287454);
+    }
+}
diff --git a/rand/src/rngs/thread.rs b/rand/src/rngs/thread.rs
new file mode 100644
index 0000000..ff772e3
--- /dev/null
+++ b/rand/src/rngs/thread.rs
@@ -0,0 +1,135 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Thread-local random number generator
+
+use std::cell::UnsafeCell;
+
+use {RngCore, CryptoRng, SeedableRng, Error};
+use rngs::adapter::ReseedingRng;
+use rngs::EntropyRng;
+use rand_hc::Hc128Core;
+
+// Rationale for using `UnsafeCell` in `ThreadRng`:
+//
+// Previously we used a `RefCell`, with an overhead of ~15%. There will only
+// ever be one mutable reference to the interior of the `UnsafeCell`, because
+// we only have such a reference inside `next_u32`, `next_u64`, etc. Within a
+// single thread (which is the definition of `ThreadRng`), there will only ever
+// be one of these methods active at a time.
+//
+// A possible scenario where there could be multiple mutable references is if
+// `ThreadRng` is used inside `next_u32` and co. But the implementation is
+// completely under our control. We just have to ensure none of them use
+// `ThreadRng` internally, which is nonsensical anyway. We should also never run
+// `ThreadRng` in destructors of its implementation, which is also nonsensical.
+//
+// The additional `Rc` is not strictly neccesary, and could be removed. For now
+// it ensures `ThreadRng` stays `!Send` and `!Sync`, and implements `Clone`.
+
+
+// Number of generated bytes after which to reseed `TreadRng`.
+//
+// The time it takes to reseed HC-128 is roughly equivalent to generating 7 KiB.
+// We pick a treshold here that is large enough to not reduce the average
+// performance too much, but also small enough to not make reseeding something
+// that basically never happens.
+const THREAD_RNG_RESEED_THRESHOLD: u64 = 32*1024*1024; // 32 MiB
+
+/// The type returned by [`thread_rng`], essentially just a reference to the
+/// PRNG in thread-local memory.
+///
+/// `ThreadRng` uses [`ReseedingRng`] wrapping the same PRNG as [`StdRng`],
+/// which is reseeded after generating 32 MiB of random data. A single instance
+/// is cached per thread and the returned `ThreadRng` is a reference to this
+/// instance — hence `ThreadRng` is neither `Send` nor `Sync` but is safe to use
+/// within a single thread. This RNG is seeded and reseeded via [`EntropyRng`]
+/// as required.
+///
+/// Note that the reseeding is done as an extra precaution against entropy
+/// leaks and is in theory unnecessary — to predict `ThreadRng`'s output, an
+/// attacker would have to either determine most of the RNG's seed or internal
+/// state, or crack the algorithm used.
+///
+/// Like [`StdRng`], `ThreadRng` is a cryptographically secure PRNG. The current
+/// algorithm used is [HC-128], which is an array-based PRNG that trades memory
+/// usage for better performance. This makes it similar to ISAAC, the algorithm
+/// used in `ThreadRng` before rand 0.5.
+///
+/// Cloning this handle just produces a new reference to the same thread-local
+/// generator.
+/// 
+/// [`thread_rng`]: ../fn.thread_rng.html
+/// [`ReseedingRng`]: adapter/struct.ReseedingRng.html
+/// [`StdRng`]: struct.StdRng.html
+/// [`EntropyRng`]: struct.EntropyRng.html
+/// [HC-128]: ../../rand_hc/struct.Hc128Rng.html
+#[derive(Clone, Debug)]
+pub struct ThreadRng {
+    // use of raw pointer implies type is neither Send nor Sync
+    rng: *mut ReseedingRng<Hc128Core, EntropyRng>,
+}
+
+thread_local!(
+    static THREAD_RNG_KEY: UnsafeCell<ReseedingRng<Hc128Core, EntropyRng>> = {
+        let mut entropy_source = EntropyRng::new();
+        let r = Hc128Core::from_rng(&mut entropy_source).unwrap_or_else(|err|
+                panic!("could not initialize thread_rng: {}", err));
+        let rng = ReseedingRng::new(r,
+                                    THREAD_RNG_RESEED_THRESHOLD,
+                                    entropy_source);
+        UnsafeCell::new(rng)
+    }
+);
+
+/// Retrieve the lazily-initialized thread-local random number
+/// generator, seeded by the system. Intended to be used in method
+/// chaining style, e.g. `thread_rng().gen::<i32>()`, or cached locally, e.g.
+/// `let mut rng = thread_rng();`.
+///
+/// For more information see [`ThreadRng`].
+///
+/// [`ThreadRng`]: rngs/struct.ThreadRng.html
+pub fn thread_rng() -> ThreadRng {
+    ThreadRng { rng: THREAD_RNG_KEY.with(|t| t.get()) }
+}
+
+impl RngCore for ThreadRng {
+    #[inline(always)]
+    fn next_u32(&mut self) -> u32 {
+        unsafe { (*self.rng).next_u32() }
+    }
+
+    #[inline(always)]
+    fn next_u64(&mut self) -> u64 {
+        unsafe { (*self.rng).next_u64() }
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        unsafe { (*self.rng).fill_bytes(dest) }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        unsafe { (*self.rng).try_fill_bytes(dest) }
+    }
+}
+
+impl CryptoRng for ThreadRng {}
+
+
+#[cfg(test)]
+mod test {
+    #[test]
+    #[cfg(not(feature="stdweb"))]
+    fn test_thread_rng() {
+        use Rng;
+        let mut r = ::thread_rng();
+        r.gen::<i32>();
+        assert_eq!(r.gen_range(0, 1), 0);
+    }
+}
diff --git a/rand/src/seq.rs b/rand/src/seq.rs
deleted file mode 100644
index a7889fe..0000000
--- a/rand/src/seq.rs
+++ /dev/null
@@ -1,337 +0,0 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Functions for randomly accessing and sampling sequences.
-
-use super::Rng;
-
-// This crate is only enabled when either std or alloc is available.
-// BTreeMap is not as fast in tests, but better than nothing.
-#[cfg(feature="std")] use std::collections::HashMap;
-#[cfg(not(feature="std"))] use alloc::btree_map::BTreeMap;
-
-#[cfg(not(feature="std"))] use alloc::Vec;
-
-/// Randomly sample `amount` elements from a finite iterator.
-///
-/// The following can be returned:
-/// - `Ok`: `Vec` of `amount` non-repeating randomly sampled elements. The order is not random.
-/// - `Err`: `Vec` of all the elements from `iterable` in sequential order. This happens when the
-///   length of `iterable` was less than `amount`. This is considered an error since exactly
-///   `amount` elements is typically expected.
-///
-/// This implementation uses `O(len(iterable))` time and `O(amount)` memory.
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{thread_rng, seq};
-///
-/// let mut rng = thread_rng();
-/// let sample = seq::sample_iter(&mut rng, 1..100, 5).unwrap();
-/// println!("{:?}", sample);
-/// ```
-pub fn sample_iter<T, I, R>(rng: &mut R, iterable: I, amount: usize) -> Result<Vec<T>, Vec<T>>
-    where I: IntoIterator<Item=T>,
-          R: Rng,
-{
-    let mut iter = iterable.into_iter();
-    let mut reservoir = Vec::with_capacity(amount);
-    reservoir.extend(iter.by_ref().take(amount));
-
-    // Continue unless the iterator was exhausted
-    //
-    // note: this prevents iterators that "restart" from causing problems.
-    // If the iterator stops once, then so do we.
-    if reservoir.len() == amount {
-        for (i, elem) in iter.enumerate() {
-            let k = rng.gen_range(0, i + 1 + amount);
-            if let Some(spot) = reservoir.get_mut(k) {
-                *spot = elem;
-            }
-        }
-        Ok(reservoir)
-    } else {
-        // Don't hang onto extra memory. There is a corner case where
-        // `amount` was much less than `len(iterable)`.
-        reservoir.shrink_to_fit();
-        Err(reservoir)
-    }
-}
-
-/// Randomly sample exactly `amount` values from `slice`.
-///
-/// The values are non-repeating and in random order.
-///
-/// This implementation uses `O(amount)` time and memory.
-///
-/// Panics if `amount > slice.len()`
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{thread_rng, seq};
-///
-/// let mut rng = thread_rng();
-/// let values = vec![5, 6, 1, 3, 4, 6, 7];
-/// println!("{:?}", seq::sample_slice(&mut rng, &values, 3));
-/// ```
-pub fn sample_slice<R, T>(rng: &mut R, slice: &[T], amount: usize) -> Vec<T>
-    where R: Rng,
-          T: Clone
-{
-    let indices = sample_indices(rng, slice.len(), amount);
-
-    let mut out = Vec::with_capacity(amount);
-    out.extend(indices.iter().map(|i| slice[*i].clone()));
-    out
-}
-
-/// Randomly sample exactly `amount` references from `slice`.
-///
-/// The references are non-repeating and in random order.
-///
-/// This implementation uses `O(amount)` time and memory.
-///
-/// Panics if `amount > slice.len()`
-///
-/// # Example
-///
-/// ```rust
-/// use rand::{thread_rng, seq};
-///
-/// let mut rng = thread_rng();
-/// let values = vec![5, 6, 1, 3, 4, 6, 7];
-/// println!("{:?}", seq::sample_slice_ref(&mut rng, &values, 3));
-/// ```
-pub fn sample_slice_ref<'a, R, T>(rng: &mut R, slice: &'a [T], amount: usize) -> Vec<&'a T>
-    where R: Rng
-{
-    let indices = sample_indices(rng, slice.len(), amount);
-
-    let mut out = Vec::with_capacity(amount);
-    out.extend(indices.iter().map(|i| &slice[*i]));
-    out
-}
-
-/// Randomly sample exactly `amount` indices from `0..length`.
-///
-/// The values are non-repeating and in random order.
-///
-/// This implementation uses `O(amount)` time and memory.
-///
-/// This method is used internally by the slice sampling methods, but it can sometimes be useful to
-/// have the indices themselves so this is provided as an alternative.
-///
-/// Panics if `amount > length`
-pub fn sample_indices<R>(rng: &mut R, length: usize, amount: usize) -> Vec<usize>
-    where R: Rng,
-{
-    if amount > length {
-        panic!("`amount` must be less than or equal to `slice.len()`");
-    }
-
-    // We are going to have to allocate at least `amount` for the output no matter what. However,
-    // if we use the `cached` version we will have to allocate `amount` as a HashMap as well since
-    // it inserts an element for every loop.
-    //
-    // Therefore, if `amount >= length / 2` then inplace will be both faster and use less memory.
-    // In fact, benchmarks show the inplace version is faster for length up to about 20 times
-    // faster than amount.
-    //
-    // TODO: there is probably even more fine-tuning that can be done here since
-    // `HashMap::with_capacity(amount)` probably allocates more than `amount` in practice,
-    // and a trade off could probably be made between memory/cpu, since hashmap operations
-    // are slower than array index swapping.
-    if amount >= length / 20 {
-        sample_indices_inplace(rng, length, amount)
-    } else {
-        sample_indices_cache(rng, length, amount)
-    }
-}
-
-/// Sample an amount of indices using an inplace partial fisher yates method.
-///
-/// This allocates the entire `length` of indices and randomizes only the first `amount`.
-/// It then truncates to `amount` and returns.
-///
-/// This is better than using a HashMap "cache" when `amount >= length / 2` since it does not
-/// require allocating an extra cache and is much faster.
-fn sample_indices_inplace<R>(rng: &mut R, length: usize, amount: usize) -> Vec<usize>
-    where R: Rng,
-{
-    debug_assert!(amount <= length);
-    let mut indices: Vec<usize> = Vec::with_capacity(length);
-    indices.extend(0..length);
-    for i in 0..amount {
-        let j: usize = rng.gen_range(i, length);
-        let tmp = indices[i];
-        indices[i] = indices[j];
-        indices[j] = tmp;
-    }
-    indices.truncate(amount);
-    debug_assert_eq!(indices.len(), amount);
-    indices
-}
-
-
-/// This method performs a partial fisher-yates on a range of indices using a HashMap
-/// as a cache to record potential collisions.
-///
-/// The cache avoids allocating the entire `length` of values. This is especially useful when
-/// `amount <<< length`, i.e. select 3 non-repeating from 1_000_000
-fn sample_indices_cache<R>(
-    rng: &mut R,
-    length: usize,
-    amount: usize,
-) -> Vec<usize>
-    where R: Rng,
-{
-    debug_assert!(amount <= length);
-    #[cfg(feature="std")] let mut cache = HashMap::with_capacity(amount);
-    #[cfg(not(feature="std"))] let mut cache = BTreeMap::new();
-    let mut out = Vec::with_capacity(amount);
-    for i in 0..amount {
-        let j: usize = rng.gen_range(i, length);
-
-        // equiv: let tmp = slice[i];
-        let tmp = match cache.get(&i) {
-            Some(e) => *e,
-            None => i,
-        };
-
-        // equiv: slice[i] = slice[j];
-        let x = match cache.get(&j) {
-            Some(x) => *x,
-            None => j,
-        };
-
-        // equiv: slice[j] = tmp;
-        cache.insert(j, tmp);
-
-        // note that in the inplace version, slice[i] is automatically "returned" value
-        out.push(x);
-    }
-    debug_assert_eq!(out.len(), amount);
-    out
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    use {thread_rng, XorShiftRng, SeedableRng};
-
-    #[test]
-    fn test_sample_iter() {
-        let min_val = 1;
-        let max_val = 100;
-
-        let mut r = thread_rng();
-        let vals = (min_val..max_val).collect::<Vec<i32>>();
-        let small_sample = sample_iter(&mut r, vals.iter(), 5).unwrap();
-        let large_sample = sample_iter(&mut r, vals.iter(), vals.len() + 5).unwrap_err();
-
-        assert_eq!(small_sample.len(), 5);
-        assert_eq!(large_sample.len(), vals.len());
-        // no randomization happens when amount >= len
-        assert_eq!(large_sample, vals.iter().collect::<Vec<_>>());
-
-        assert!(small_sample.iter().all(|e| {
-            **e >= min_val && **e <= max_val
-        }));
-    }
-    #[test]
-    fn test_sample_slice_boundaries() {
-        let empty: &[u8] = &[];
-
-        let mut r = thread_rng();
-
-        // sample 0 items
-        assert_eq!(sample_slice(&mut r, empty, 0), vec![]);
-        assert_eq!(sample_slice(&mut r, &[42, 2, 42], 0), vec![]);
-
-        // sample 1 item
-        assert_eq!(sample_slice(&mut r, &[42], 1), vec![42]);
-        let v = sample_slice(&mut r, &[1, 42], 1)[0];
-        assert!(v == 1 || v == 42);
-
-        // sample "all" the items
-        let v = sample_slice(&mut r, &[42, 133], 2);
-        assert!(v == vec![42, 133] || v == vec![133, 42]);
-
-        assert_eq!(sample_indices_inplace(&mut r, 0, 0), vec![]);
-        assert_eq!(sample_indices_inplace(&mut r, 1, 0), vec![]);
-        assert_eq!(sample_indices_inplace(&mut r, 1, 1), vec![0]);
-
-        assert_eq!(sample_indices_cache(&mut r, 0, 0), vec![]);
-        assert_eq!(sample_indices_cache(&mut r, 1, 0), vec![]);
-        assert_eq!(sample_indices_cache(&mut r, 1, 1), vec![0]);
-
-        // Make sure lucky 777's aren't lucky
-        let slice = &[42, 777];
-        let mut num_42 = 0;
-        let total = 1000;
-        for _ in 0..total {
-            let v = sample_slice(&mut r, slice, 1);
-            assert_eq!(v.len(), 1);
-            let v = v[0];
-            assert!(v == 42 || v == 777);
-            if v == 42 {
-                num_42 += 1;
-            }
-        }
-        let ratio_42 = num_42 as f64 / 1000 as f64;
-        assert!(0.4 <= ratio_42 || ratio_42 <= 0.6, "{}", ratio_42);
-    }
-
-    #[test]
-    fn test_sample_slice() {
-        let xor_rng = XorShiftRng::from_seed;
-
-        let max_range = 100;
-        let mut r = thread_rng();
-
-        for length in 1usize..max_range {
-            let amount = r.gen_range(0, length);
-            let seed: [u32; 4] = [
-                r.next_u32(), r.next_u32(), r.next_u32(), r.next_u32()
-            ];
-
-            println!("Selecting indices: len={}, amount={}, seed={:?}", length, amount, seed);
-
-            // assert that the two index methods give exactly the same result
-            let inplace = sample_indices_inplace(
-                &mut xor_rng(seed), length, amount);
-            let cache = sample_indices_cache(
-                &mut xor_rng(seed), length, amount);
-            assert_eq!(inplace, cache);
-
-            // assert the basics work
-            let regular = sample_indices(
-                &mut xor_rng(seed), length, amount);
-            assert_eq!(regular.len(), amount);
-            assert!(regular.iter().all(|e| *e < length));
-            assert_eq!(regular, inplace);
-
-            // also test that sampling the slice works
-            let vec: Vec<usize> = (0..length).collect();
-            {
-                let result = sample_slice(&mut xor_rng(seed), &vec, amount);
-                assert_eq!(result, regular);
-            }
-
-            {
-                let result = sample_slice_ref(&mut xor_rng(seed), &vec, amount);
-                let expected = regular.iter().map(|v| v).collect::<Vec<_>>();
-                assert_eq!(result, expected);
-            }
-        }
-    }
-}
diff --git a/rand/src/seq/index.rs b/rand/src/seq/index.rs
new file mode 100644
index 0000000..3d4df3a
--- /dev/null
+++ b/rand/src/seq/index.rs
@@ -0,0 +1,378 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Index sampling
+
+#[cfg(feature="alloc")] use core::slice;
+
+#[cfg(feature="std")] use std::vec;
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::vec::{self, Vec};
+// BTreeMap is not as fast in tests, but better than nothing.
+#[cfg(feature="std")] use std::collections::{HashSet};
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::collections::BTreeSet;
+
+#[cfg(feature="alloc")] use distributions::{Distribution, Uniform};
+use Rng;
+
+/// A vector of indices.
+///
+/// Multiple internal representations are possible.
+#[derive(Clone, Debug)]
+pub enum IndexVec {
+    #[doc(hidden)] U32(Vec<u32>),
+    #[doc(hidden)] USize(Vec<usize>),
+}
+
+impl IndexVec {
+    /// Returns the number of indices
+    pub fn len(&self) -> usize {
+        match self {
+            &IndexVec::U32(ref v) => v.len(),
+            &IndexVec::USize(ref v) => v.len(),
+        }
+    }
+
+    /// Return the value at the given `index`.
+    ///
+    /// (Note: we cannot implement `std::ops::Index` because of lifetime
+    /// restrictions.)
+    pub fn index(&self, index: usize) -> usize {
+        match self {
+            &IndexVec::U32(ref v) => v[index] as usize,
+            &IndexVec::USize(ref v) => v[index],
+        }
+    }
+
+    /// Return result as a `Vec<usize>`. Conversion may or may not be trivial.
+    pub fn into_vec(self) -> Vec<usize> {
+        match self {
+            IndexVec::U32(v) => v.into_iter().map(|i| i as usize).collect(),
+            IndexVec::USize(v) => v,
+        }
+    }
+
+    /// Iterate over the indices as a sequence of `usize` values
+    pub fn iter<'a>(&'a self) -> IndexVecIter<'a> {
+        match self {
+            &IndexVec::U32(ref v) => IndexVecIter::U32(v.iter()),
+            &IndexVec::USize(ref v) => IndexVecIter::USize(v.iter()),
+        }
+    }
+
+    /// Convert into an iterator over the indices as a sequence of `usize` values
+    pub fn into_iter(self) -> IndexVecIntoIter {
+        match self {
+            IndexVec::U32(v) => IndexVecIntoIter::U32(v.into_iter()),
+            IndexVec::USize(v) => IndexVecIntoIter::USize(v.into_iter()),
+        }
+    }
+}
+
+impl PartialEq for IndexVec {
+    fn eq(&self, other: &IndexVec) -> bool {
+        use self::IndexVec::*;
+        match (self, other) {
+            (&U32(ref v1), &U32(ref v2)) => v1 == v2,
+            (&USize(ref v1), &USize(ref v2)) => v1 == v2,
+            (&U32(ref v1), &USize(ref v2)) => (v1.len() == v2.len())
+                && (v1.iter().zip(v2.iter()).all(|(x, y)| *x as usize == *y)),
+            (&USize(ref v1), &U32(ref v2)) => (v1.len() == v2.len())
+                && (v1.iter().zip(v2.iter()).all(|(x, y)| *x == *y as usize)),
+        }
+    }
+}
+
+impl From<Vec<u32>> for IndexVec {
+    fn from(v: Vec<u32>) -> Self {
+        IndexVec::U32(v)
+    }
+}
+
+impl From<Vec<usize>> for IndexVec {
+    fn from(v: Vec<usize>) -> Self {
+        IndexVec::USize(v)
+    }
+}
+
+/// Return type of `IndexVec::iter`.
+#[derive(Debug)]
+pub enum IndexVecIter<'a> {
+    #[doc(hidden)] U32(slice::Iter<'a, u32>),
+    #[doc(hidden)] USize(slice::Iter<'a, usize>),
+}
+
+impl<'a> Iterator for IndexVecIter<'a> {
+    type Item = usize;
+    fn next(&mut self) -> Option<usize> {
+        use self::IndexVecIter::*;
+        match self {
+            &mut U32(ref mut iter) => iter.next().map(|i| *i as usize),
+            &mut USize(ref mut iter) => iter.next().cloned(),
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match self {
+            &IndexVecIter::U32(ref v) => v.size_hint(),
+            &IndexVecIter::USize(ref v) => v.size_hint(),
+        }
+    }
+}
+
+impl<'a> ExactSizeIterator for IndexVecIter<'a> {}
+
+/// Return type of `IndexVec::into_iter`.
+#[derive(Clone, Debug)]
+pub enum IndexVecIntoIter {
+    #[doc(hidden)] U32(vec::IntoIter<u32>),
+    #[doc(hidden)] USize(vec::IntoIter<usize>),
+}
+
+impl Iterator for IndexVecIntoIter {
+    type Item = usize;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        use self::IndexVecIntoIter::*;
+        match self {
+            &mut U32(ref mut v) => v.next().map(|i| i as usize),
+            &mut USize(ref mut v) => v.next(),
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        use self::IndexVecIntoIter::*;
+        match self {
+            &U32(ref v) => v.size_hint(),
+            &USize(ref v) => v.size_hint(),
+        }
+    }
+}
+
+impl ExactSizeIterator for IndexVecIntoIter {}
+
+
+/// Randomly sample exactly `amount` distinct indices from `0..length`, and
+/// return them in random order (fully shuffled).
+///
+/// This method is used internally by the slice sampling methods, but it can
+/// sometimes be useful to have the indices themselves so this is provided as
+/// an alternative.
+///
+/// The implementation used is not specified; we automatically select the
+/// fastest available algorithm for the `length` and `amount` parameters
+/// (based on detailed profiling on an Intel Haswell CPU). Roughly speaking,
+/// complexity is `O(amount)`, except that when `amount` is small, performance
+/// is closer to `O(amount^2)`, and when `length` is close to `amount` then
+/// `O(length)`.
+///
+/// Note that performance is significantly better over `u32` indices than over
+/// `u64` indices. Because of this we hide the underlying type behind an
+/// abstraction, `IndexVec`.
+/// 
+/// If an allocation-free `no_std` function is required, it is suggested
+/// to adapt the internal `sample_floyd` implementation.
+///
+/// Panics if `amount > length`.
+pub fn sample<R>(rng: &mut R, length: usize, amount: usize) -> IndexVec
+    where R: Rng + ?Sized,
+{
+    if amount > length {
+        panic!("`amount` of samples must be less than or equal to `length`");
+    }
+    if length > (::core::u32::MAX as usize) {
+        // We never want to use inplace here, but could use floyd's alg
+        // Lazy version: always use the cache alg.
+        return sample_rejection(rng, length, amount);
+    }
+    let amount = amount as u32;
+    let length = length as u32;
+
+    // Choice of algorithm here depends on both length and amount. See:
+    // https://github.com/rust-random/rand/pull/479
+    // We do some calculations with f32. Accuracy is not very important.
+
+    if amount < 163 {
+        const C: [[f32; 2]; 2] = [[1.6, 8.0/45.0], [10.0, 70.0/9.0]];
+        let j = if length < 500_000 { 0 } else { 1 };
+        let amount_fp = amount as f32;
+        let m4 = C[0][j] * amount_fp;
+        // Short-cut: when amount < 12, floyd's is always faster
+        if amount > 11 && (length as f32) < (C[1][j] + m4) * amount_fp {
+            sample_inplace(rng, length, amount)
+        } else {
+            sample_floyd(rng, length, amount)
+        }
+    } else {
+        const C: [f32; 2] = [270.0, 330.0/9.0];
+        let j = if length < 500_000 { 0 } else { 1 };
+        if (length as f32) < C[j] * (amount as f32) {
+            sample_inplace(rng, length, amount)
+        } else {
+            // note: could have a specific u32 impl, but I'm lazy and
+            // generics don't have usable conversions
+            sample_rejection(rng, length as usize, amount as usize)
+        }
+    }
+}
+
+/// Randomly sample exactly `amount` indices from `0..length`, using Floyd's
+/// combination algorithm.
+///
+/// The output values are fully shuffled. (Overhead is under 50%.)
+///
+/// This implementation uses `O(amount)` memory and `O(amount^2)` time.
+fn sample_floyd<R>(rng: &mut R, length: u32, amount: u32) -> IndexVec
+    where R: Rng + ?Sized,
+{
+    // For small amount we use Floyd's fully-shuffled variant. For larger
+    // amounts this is slow due to Vec::insert performance, so we shuffle
+    // afterwards. Benchmarks show little overhead from extra logic.
+    let floyd_shuffle = amount < 50;
+
+    debug_assert!(amount <= length);
+    let mut indices = Vec::with_capacity(amount as usize);
+    for j in length - amount .. length {
+        let t = rng.gen_range(0, j + 1);
+        if floyd_shuffle {
+            if let Some(pos) = indices.iter().position(|&x| x == t) {
+                indices.insert(pos, j);
+                continue;
+            }
+        } else {
+            if indices.contains(&t) {
+                indices.push(j);
+                continue;
+            }
+        }
+        indices.push(t);
+    }
+    if !floyd_shuffle {
+        // Reimplement SliceRandom::shuffle with smaller indices
+        for i in (1..amount).rev() {
+            // invariant: elements with index > i have been locked in place.
+            indices.swap(i as usize, rng.gen_range(0, i + 1) as usize);
+        }
+    }
+    IndexVec::from(indices)
+}
+
+/// Randomly sample exactly `amount` indices from `0..length`, using an inplace
+/// partial Fisher-Yates method.
+/// Sample an amount of indices using an inplace partial fisher yates method.
+///
+/// This allocates the entire `length` of indices and randomizes only the first `amount`.
+/// It then truncates to `amount` and returns.
+///
+/// This method is not appropriate for large `length` and potentially uses a lot
+/// of memory; because of this we only implement for `u32` index (which improves
+/// performance in all cases).
+///
+/// Set-up is `O(length)` time and memory and shuffling is `O(amount)` time.
+fn sample_inplace<R>(rng: &mut R, length: u32, amount: u32) -> IndexVec
+    where R: Rng + ?Sized,
+{
+    debug_assert!(amount <= length);
+    let mut indices: Vec<u32> = Vec::with_capacity(length as usize);
+    indices.extend(0..length);
+    for i in 0..amount {
+        let j: u32 = rng.gen_range(i, length);
+        indices.swap(i as usize, j as usize);
+    }
+    indices.truncate(amount as usize);
+    debug_assert_eq!(indices.len(), amount as usize);
+    IndexVec::from(indices)
+}
+
+/// Randomly sample exactly `amount` indices from `0..length`, using rejection
+/// sampling.
+/// 
+/// Since `amount <<< length` there is a low chance of a random sample in
+/// `0..length` being a duplicate. We test for duplicates and resample where
+/// necessary. The algorithm is `O(amount)` time and memory.
+fn sample_rejection<R>(rng: &mut R, length: usize, amount: usize) -> IndexVec
+    where R: Rng + ?Sized,
+{
+    debug_assert!(amount < length);
+    #[cfg(feature="std")] let mut cache = HashSet::with_capacity(amount);
+    #[cfg(not(feature="std"))] let mut cache = BTreeSet::new();
+    let distr = Uniform::new(0, length);
+    let mut indices = Vec::with_capacity(amount);
+    for _ in 0..amount {
+        let mut pos = distr.sample(rng);
+        while !cache.insert(pos) {
+            pos = distr.sample(rng);
+        }
+        indices.push(pos);
+    }
+
+    debug_assert_eq!(indices.len(), amount);
+    IndexVec::from(indices)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_sample_boundaries() {
+        let mut r = ::test::rng(404);
+
+        assert_eq!(sample_inplace(&mut r, 0, 0).len(), 0);
+        assert_eq!(sample_inplace(&mut r, 1, 0).len(), 0);
+        assert_eq!(sample_inplace(&mut r, 1, 1).into_vec(), vec![0]);
+
+        assert_eq!(sample_rejection(&mut r, 1, 0).len(), 0);
+
+        assert_eq!(sample_floyd(&mut r, 0, 0).len(), 0);
+        assert_eq!(sample_floyd(&mut r, 1, 0).len(), 0);
+        assert_eq!(sample_floyd(&mut r, 1, 1).into_vec(), vec![0]);
+
+        // These algorithms should be fast with big numbers. Test average.
+        let sum: usize = sample_rejection(&mut r, 1 << 25, 10)
+                .into_iter().sum();
+        assert!(1 << 25 < sum && sum < (1 << 25) * 25);
+
+        let sum: usize = sample_floyd(&mut r, 1 << 25, 10)
+                .into_iter().sum();
+        assert!(1 << 25 < sum && sum < (1 << 25) * 25);
+    }
+
+    #[test]
+    fn test_sample_alg() {
+        let seed_rng = ::test::rng;
+
+        // We can't test which algorithm is used directly, but Floyd's alg
+        // should produce different results from the others. (Also, `inplace`
+        // and `cached` currently use different sizes thus produce different results.)
+
+        // A small length and relatively large amount should use inplace
+        let (length, amount): (usize, usize) = (100, 50);
+        let v1 = sample(&mut seed_rng(420), length, amount);
+        let v2 = sample_inplace(&mut seed_rng(420), length as u32, amount as u32);
+        assert!(v1.iter().all(|e| e < length));
+        assert_eq!(v1, v2);
+
+        // Test Floyd's alg does produce different results
+        let v3 = sample_floyd(&mut seed_rng(420), length as u32, amount as u32);
+        assert!(v1 != v3);
+
+        // A large length and small amount should use Floyd
+        let (length, amount): (usize, usize) = (1<<20, 50);
+        let v1 = sample(&mut seed_rng(421), length, amount);
+        let v2 = sample_floyd(&mut seed_rng(421), length as u32, amount as u32);
+        assert!(v1.iter().all(|e| e < length));
+        assert_eq!(v1, v2);
+
+        // A large length and larger amount should use cache
+        let (length, amount): (usize, usize) = (1<<20, 600);
+        let v1 = sample(&mut seed_rng(422), length, amount);
+        let v2 = sample_rejection(&mut seed_rng(422), length, amount);
+        assert!(v1.iter().all(|e| e < length));
+        assert_eq!(v1, v2);
+    }
+}
diff --git a/rand/src/seq/mod.rs b/rand/src/seq/mod.rs
new file mode 100644
index 0000000..9959602
--- /dev/null
+++ b/rand/src/seq/mod.rs
@@ -0,0 +1,836 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Functions for randomly accessing and sampling sequences.
+//! 
+//! TODO: module doc
+
+
+#[cfg(feature="alloc")] pub mod index;
+
+#[cfg(feature="alloc")] use core::ops::Index;
+
+#[cfg(all(feature="alloc", not(feature="std")))] use alloc::vec::Vec;
+
+use Rng;
+#[cfg(feature="alloc")] use distributions::WeightedError;
+#[cfg(feature="alloc")] use distributions::uniform::{SampleUniform, SampleBorrow};
+
+/// Extension trait on slices, providing random mutation and sampling methods.
+/// 
+/// An implementation is provided for slices. This may also be implementable for
+/// other types.
+pub trait SliceRandom {
+    /// The element type.
+    type Item;
+
+    /// Returns a reference to one random element of the slice, or `None` if the
+    /// slice is empty.
+    /// 
+    /// Depending on the implementation, complexity is expected to be `O(1)`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rand::thread_rng;
+    /// use rand::seq::SliceRandom;
+    ///
+    /// let choices = [1, 2, 4, 8, 16, 32];
+    /// let mut rng = thread_rng();
+    /// println!("{:?}", choices.choose(&mut rng));
+    /// assert_eq!(choices[..0].choose(&mut rng), None);
+    /// ```
+    fn choose<R>(&self, rng: &mut R) -> Option<&Self::Item>
+        where R: Rng + ?Sized;
+
+    /// Returns a mutable reference to one random element of the slice, or
+    /// `None` if the slice is empty.
+    /// 
+    /// Depending on the implementation, complexity is expected to be `O(1)`.
+    fn choose_mut<R>(&mut self, rng: &mut R) -> Option<&mut Self::Item>
+        where R: Rng + ?Sized;
+
+    /// Produces an iterator that chooses `amount` elements from the slice at
+    /// random without repeating any, and returns them in random order.
+    /// 
+    /// In case this API is not sufficiently flexible, use `index::sample` then
+    /// apply the indices to the slice.
+    /// 
+    /// Complexity is expected to be the same as `index::sample`.
+    /// 
+    /// # Example
+    /// ```
+    /// use rand::seq::SliceRandom;
+    /// 
+    /// let mut rng = &mut rand::thread_rng();
+    /// let sample = "Hello, audience!".as_bytes();
+    /// 
+    /// // collect the results into a vector:
+    /// let v: Vec<u8> = sample.choose_multiple(&mut rng, 3).cloned().collect();
+    /// 
+    /// // store in a buffer:
+    /// let mut buf = [0u8; 5];
+    /// for (b, slot) in sample.choose_multiple(&mut rng, buf.len()).zip(buf.iter_mut()) {
+    ///     *slot = *b;
+    /// }
+    /// ```
+    #[cfg(feature = "alloc")]
+    fn choose_multiple<R>(&self, rng: &mut R, amount: usize) -> SliceChooseIter<Self, Self::Item>
+        where R: Rng + ?Sized;
+
+    /// Similar to [`choose`], where the likelihood of each outcome may be
+    /// specified. The specified function `weight` maps items `x` to a relative
+    /// likelihood `weight(x)`. The probability of each item being selected is
+    /// therefore `weight(x) / s`, where `s` is the sum of all `weight(x)`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rand::prelude::*;
+    ///
+    /// let choices = [('a', 2), ('b', 1), ('c', 1)];
+    /// let mut rng = thread_rng();
+    /// // 50% chance to print 'a', 25% chance to print 'b', 25% chance to print 'c'
+    /// println!("{:?}", choices.choose_weighted(&mut rng, |item| item.1).unwrap().0);
+    /// ```
+    /// [`choose`]: trait.SliceRandom.html#method.choose
+    #[cfg(feature = "alloc")]
+    fn choose_weighted<R, F, B, X>(&self, rng: &mut R, weight: F) -> Result<&Self::Item, WeightedError>
+        where R: Rng + ?Sized,
+              F: Fn(&Self::Item) -> B,
+              B: SampleBorrow<X>,
+              X: SampleUniform +
+                 for<'a> ::core::ops::AddAssign<&'a X> +
+                 ::core::cmp::PartialOrd<X> +
+                 Clone +
+                 Default;
+
+    /// Similar to [`choose_mut`], where the likelihood of each outcome may be
+    /// specified. The specified function `weight` maps items `x` to a relative
+    /// likelihood `weight(x)`. The probability of each item being selected is
+    /// therefore `weight(x) / s`, where `s` is the sum of all `weight(x)`.
+    ///
+    /// See also [`choose_weighted`].
+    ///
+    /// [`choose_mut`]: trait.SliceRandom.html#method.choose_mut
+    /// [`choose_weighted`]: trait.SliceRandom.html#method.choose_weighted
+    #[cfg(feature = "alloc")]
+    fn choose_weighted_mut<R, F, B, X>(&mut self, rng: &mut R, weight: F) -> Result<&mut Self::Item, WeightedError>
+        where R: Rng + ?Sized,
+              F: Fn(&Self::Item) -> B,
+              B: SampleBorrow<X>,
+              X: SampleUniform +
+                 for<'a> ::core::ops::AddAssign<&'a X> +
+                 ::core::cmp::PartialOrd<X> +
+                 Clone +
+                 Default;
+
+    /// Shuffle a mutable slice in place.
+    /// 
+    /// Depending on the implementation, complexity is expected to be `O(1)`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rand::thread_rng;
+    /// use rand::seq::SliceRandom;
+    ///
+    /// let mut rng = thread_rng();
+    /// let mut y = [1, 2, 3, 4, 5];
+    /// println!("Unshuffled: {:?}", y);
+    /// y.shuffle(&mut rng);
+    /// println!("Shuffled:   {:?}", y);
+    /// ```
+    fn shuffle<R>(&mut self, rng: &mut R) where R: Rng + ?Sized;
+
+    /// Shuffle a slice in place, but exit early.
+    ///
+    /// Returns two mutable slices from the source slice. The first contains
+    /// `amount` elements randomly permuted. The second has the remaining
+    /// elements that are not fully shuffled.
+    ///
+    /// This is an efficient method to select `amount` elements at random from
+    /// the slice, provided the slice may be mutated.
+    ///
+    /// If you only need to choose elements randomly and `amount > self.len()/2`
+    /// then you may improve performance by taking
+    /// `amount = values.len() - amount` and using only the second slice.
+    ///
+    /// If `amount` is greater than the number of elements in the slice, this
+    /// will perform a full shuffle.
+    ///
+    /// Complexity is expected to be `O(m)` where `m = amount`.
+    fn partial_shuffle<R>(&mut self, rng: &mut R, amount: usize)
+        -> (&mut [Self::Item], &mut [Self::Item]) where R: Rng + ?Sized;
+}
+
+/// Extension trait on iterators, providing random sampling methods.
+pub trait IteratorRandom: Iterator + Sized {
+    /// Choose one element at random from the iterator. If you have a slice,
+    /// it's significantly faster to call the [`choose`] or [`choose_mut`]
+    /// functions using the slice instead.
+    ///
+    /// Returns `None` if and only if the iterator is empty.
+    /// 
+    /// Complexity is `O(n)`, where `n` is the length of the iterator.
+    /// This likely consumes multiple random numbers, but the exact number
+    /// is unspecified.
+    ///
+    /// [`choose`]: trait.SliceRandom.html#method.choose
+    /// [`choose_mut`]: trait.SliceRandom.html#method.choose_mut
+    fn choose<R>(mut self, rng: &mut R) -> Option<Self::Item>
+        where R: Rng + ?Sized
+    {
+        let (mut lower, mut upper) = self.size_hint();
+        let mut consumed = 0;
+        let mut result = None;
+
+        if upper == Some(lower) {
+            return if lower == 0 { None } else { self.nth(rng.gen_range(0, lower)) };
+        }
+
+        // Continue until the iterator is exhausted
+        loop {
+            if lower > 1 {
+                let ix = rng.gen_range(0, lower + consumed);
+                let skip;
+                if ix < lower {
+                    result = self.nth(ix);
+                    skip = lower - (ix + 1);
+                } else {
+                    skip = lower;
+                }
+                if upper == Some(lower) {
+                    return result;
+                }
+                consumed += lower;
+                if skip > 0 {
+                    self.nth(skip - 1);
+                }
+            } else {
+                let elem = self.next();
+                if elem.is_none() {
+                    return result;
+                }
+                consumed += 1;
+                let denom = consumed as f64; // accurate to 2^53 elements
+                if rng.gen_bool(1.0 / denom) {
+                    result = elem;
+                }
+            }
+
+            let hint = self.size_hint();
+            lower = hint.0;
+            upper = hint.1;
+        }
+    }
+
+    /// Collects `amount` values at random from the iterator into a supplied
+    /// buffer.
+    /// 
+    /// Although the elements are selected randomly, the order of elements in
+    /// the buffer is neither stable nor fully random. If random ordering is
+    /// desired, shuffle the result.
+    /// 
+    /// Returns the number of elements added to the buffer. This equals `amount`
+    /// unless the iterator contains insufficient elements, in which case this
+    /// equals the number of elements available.
+    /// 
+    /// Complexity is `O(n)` where `n` is the length of the iterator.
+    fn choose_multiple_fill<R>(mut self, rng: &mut R, buf: &mut [Self::Item])
+        -> usize where R: Rng + ?Sized
+    {
+        let amount = buf.len();
+        let mut len = 0;
+        while len < amount {
+            if let Some(elem) = self.next() {
+                buf[len] = elem;
+                len += 1;
+            } else {
+                // Iterator exhausted; stop early
+                return len;
+            }
+        }
+
+        // Continue, since the iterator was not exhausted
+        for (i, elem) in self.enumerate() {
+            let k = rng.gen_range(0, i + 1 + amount);
+            if let Some(slot) = buf.get_mut(k) {
+                *slot = elem;
+            }
+        }
+        len
+    }
+
+    /// Collects `amount` values at random from the iterator into a vector.
+    ///
+    /// This is equivalent to `choose_multiple_fill` except for the result type.
+    ///
+    /// Although the elements are selected randomly, the order of elements in
+    /// the buffer is neither stable nor fully random. If random ordering is
+    /// desired, shuffle the result.
+    /// 
+    /// The length of the returned vector equals `amount` unless the iterator
+    /// contains insufficient elements, in which case it equals the number of
+    /// elements available.
+    /// 
+    /// Complexity is `O(n)` where `n` is the length of the iterator.
+    #[cfg(feature = "alloc")]
+    fn choose_multiple<R>(mut self, rng: &mut R, amount: usize) -> Vec<Self::Item>
+        where R: Rng + ?Sized
+    {
+        let mut reservoir = Vec::with_capacity(amount);
+        reservoir.extend(self.by_ref().take(amount));
+
+        // Continue unless the iterator was exhausted
+        //
+        // note: this prevents iterators that "restart" from causing problems.
+        // If the iterator stops once, then so do we.
+        if reservoir.len() == amount {
+            for (i, elem) in self.enumerate() {
+                let k = rng.gen_range(0, i + 1 + amount);
+                if let Some(slot) = reservoir.get_mut(k) {
+                    *slot = elem;
+                }
+            }
+        } else {
+            // Don't hang onto extra memory. There is a corner case where
+            // `amount` was much less than `self.len()`.
+            reservoir.shrink_to_fit();
+        }
+        reservoir
+    }
+}
+
+
+impl<T> SliceRandom for [T] {
+    type Item = T;
+
+    fn choose<R>(&self, rng: &mut R) -> Option<&Self::Item>
+        where R: Rng + ?Sized
+    {
+        if self.is_empty() {
+            None
+        } else {
+            Some(&self[rng.gen_range(0, self.len())])
+        }
+    }
+
+    fn choose_mut<R>(&mut self, rng: &mut R) -> Option<&mut Self::Item>
+        where R: Rng + ?Sized
+    {
+        if self.is_empty() {
+            None
+        } else {
+            let len = self.len();
+            Some(&mut self[rng.gen_range(0, len)])
+        }
+    }
+
+    #[cfg(feature = "alloc")]
+    fn choose_multiple<R>(&self, rng: &mut R, amount: usize)
+        -> SliceChooseIter<Self, Self::Item>
+        where R: Rng + ?Sized
+    {
+        let amount = ::core::cmp::min(amount, self.len());
+        SliceChooseIter {
+            slice: self,
+            _phantom: Default::default(),
+            indices: index::sample(rng, self.len(), amount).into_iter(),
+        }
+    }
+
+    #[cfg(feature = "alloc")]
+    fn choose_weighted<R, F, B, X>(&self, rng: &mut R, weight: F) -> Result<&Self::Item, WeightedError>
+        where R: Rng + ?Sized,
+              F: Fn(&Self::Item) -> B,
+              B: SampleBorrow<X>,
+              X: SampleUniform +
+                 for<'a> ::core::ops::AddAssign<&'a X> +
+                 ::core::cmp::PartialOrd<X> +
+                 Clone +
+                 Default {
+        use distributions::{Distribution, WeightedIndex};
+        let distr = WeightedIndex::new(self.iter().map(weight))?;
+        Ok(&self[distr.sample(rng)])
+    }
+
+    #[cfg(feature = "alloc")]
+    fn choose_weighted_mut<R, F, B, X>(&mut self, rng: &mut R, weight: F) -> Result<&mut Self::Item, WeightedError>
+        where R: Rng + ?Sized,
+              F: Fn(&Self::Item) -> B,
+              B: SampleBorrow<X>,
+              X: SampleUniform +
+                 for<'a> ::core::ops::AddAssign<&'a X> +
+                 ::core::cmp::PartialOrd<X> +
+                 Clone +
+                 Default {
+        use distributions::{Distribution, WeightedIndex};
+        let distr = WeightedIndex::new(self.iter().map(weight))?;
+        Ok(&mut self[distr.sample(rng)])
+    }
+
+    fn shuffle<R>(&mut self, rng: &mut R) where R: Rng + ?Sized
+    {
+        for i in (1..self.len()).rev() {
+            // invariant: elements with index > i have been locked in place.
+            self.swap(i, rng.gen_range(0, i + 1));
+        }
+    }
+
+    fn partial_shuffle<R>(&mut self, rng: &mut R, amount: usize)
+        -> (&mut [Self::Item], &mut [Self::Item]) where R: Rng + ?Sized
+    {
+        // This applies Durstenfeld's algorithm for the
+        // [Fisher–Yates shuffle](https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm)
+        // for an unbiased permutation, but exits early after choosing `amount`
+        // elements.
+        
+        let len = self.len();
+        let end = if amount >= len { 0 } else { len - amount };
+        
+        for i in (end..len).rev() {
+            // invariant: elements with index > i have been locked in place.
+            self.swap(i, rng.gen_range(0, i + 1));
+        }
+        let r = self.split_at_mut(end);
+        (r.1, r.0)
+    }
+}
+
+impl<I> IteratorRandom for I where I: Iterator + Sized {}
+
+
+/// Iterator over multiple choices, as returned by [`SliceRandom::choose_multiple](
+/// trait.SliceRandom.html#method.choose_multiple).
+#[cfg(feature = "alloc")]
+#[derive(Debug)]
+pub struct SliceChooseIter<'a, S: ?Sized + 'a, T: 'a> {
+    slice: &'a S,
+    _phantom: ::core::marker::PhantomData<T>,
+    indices: index::IndexVecIntoIter,
+}
+
+#[cfg(feature = "alloc")]
+impl<'a, S: Index<usize, Output = T> + ?Sized + 'a, T: 'a> Iterator for SliceChooseIter<'a, S, T> {
+    type Item = &'a T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // TODO: investigate using SliceIndex::get_unchecked when stable
+        self.indices.next().map(|i| &self.slice[i as usize])
+    }
+    
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.indices.len(), Some(self.indices.len()))
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl<'a, S: Index<usize, Output = T> + ?Sized + 'a, T: 'a> ExactSizeIterator
+    for SliceChooseIter<'a, S, T>
+{
+    fn len(&self) -> usize {
+        self.indices.len()
+    }
+}
+
+
+/// Randomly sample `amount` elements from a finite iterator.
+///
+/// Deprecated: use [`IteratorRandom::choose_multiple`] instead.
+/// 
+/// [`IteratorRandom::choose_multiple`]: trait.IteratorRandom.html#method.choose_multiple
+#[cfg(feature = "alloc")]
+#[deprecated(since="0.6.0", note="use IteratorRandom::choose_multiple instead")]
+pub fn sample_iter<T, I, R>(rng: &mut R, iterable: I, amount: usize) -> Result<Vec<T>, Vec<T>>
+    where I: IntoIterator<Item=T>,
+          R: Rng + ?Sized,
+{
+    use seq::IteratorRandom;
+    let iter = iterable.into_iter();
+    let result = iter.choose_multiple(rng, amount);
+    if result.len() == amount {
+        Ok(result)
+    } else {
+        Err(result)
+    }
+}
+
+/// Randomly sample exactly `amount` values from `slice`.
+///
+/// The values are non-repeating and in random order.
+///
+/// This implementation uses `O(amount)` time and memory.
+///
+/// Panics if `amount > slice.len()`
+///
+/// Deprecated: use [`SliceRandom::choose_multiple`] instead.
+/// 
+/// [`SliceRandom::choose_multiple`]: trait.SliceRandom.html#method.choose_multiple
+#[cfg(feature = "alloc")]
+#[deprecated(since="0.6.0", note="use SliceRandom::choose_multiple instead")]
+pub fn sample_slice<R, T>(rng: &mut R, slice: &[T], amount: usize) -> Vec<T>
+    where R: Rng + ?Sized,
+          T: Clone
+{
+    let indices = index::sample(rng, slice.len(), amount).into_iter();
+
+    let mut out = Vec::with_capacity(amount);
+    out.extend(indices.map(|i| slice[i].clone()));
+    out
+}
+
+/// Randomly sample exactly `amount` references from `slice`.
+///
+/// The references are non-repeating and in random order.
+///
+/// This implementation uses `O(amount)` time and memory.
+///
+/// Panics if `amount > slice.len()`
+///
+/// Deprecated: use [`SliceRandom::choose_multiple`] instead.
+/// 
+/// [`SliceRandom::choose_multiple`]: trait.SliceRandom.html#method.choose_multiple
+#[cfg(feature = "alloc")]
+#[deprecated(since="0.6.0", note="use SliceRandom::choose_multiple instead")]
+pub fn sample_slice_ref<'a, R, T>(rng: &mut R, slice: &'a [T], amount: usize) -> Vec<&'a T>
+    where R: Rng + ?Sized
+{
+    let indices = index::sample(rng, slice.len(), amount).into_iter();
+
+    let mut out = Vec::with_capacity(amount);
+    out.extend(indices.map(|i| &slice[i]));
+    out
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    #[cfg(feature = "alloc")] use {Rng, SeedableRng};
+    #[cfg(feature = "alloc")] use rngs::SmallRng;
+    #[cfg(all(feature="alloc", not(feature="std")))]
+    use alloc::vec::Vec;
+
+    #[test]
+    fn test_slice_choose() {
+        let mut r = ::test::rng(107);
+        let chars = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n'];
+        let mut chosen = [0i32; 14];
+        for _ in 0..1000 {
+            let picked = *chars.choose(&mut r).unwrap();
+            chosen[(picked as usize) - ('a' as usize)] += 1;
+        }
+        for count in chosen.iter() {
+            let err = *count - (1000 / (chars.len() as i32));
+            assert!(-20 <= err && err <= 20);
+        }
+
+        chosen.iter_mut().for_each(|x| *x = 0);
+        for _ in 0..1000 {
+            *chosen.choose_mut(&mut r).unwrap() += 1;
+        }
+        for count in chosen.iter() {
+            let err = *count - (1000 / (chosen.len() as i32));
+            assert!(-20 <= err && err <= 20);
+        }
+
+        let mut v: [isize; 0] = [];
+        assert_eq!(v.choose(&mut r), None);
+        assert_eq!(v.choose_mut(&mut r), None);
+    }
+
+    #[derive(Clone)]
+    struct UnhintedIterator<I: Iterator + Clone> {
+        iter: I,
+    }
+    impl<I: Iterator + Clone> Iterator for UnhintedIterator<I> {
+        type Item = I::Item;
+        fn next(&mut self) -> Option<Self::Item> {
+            self.iter.next()
+        }
+    }
+
+    #[derive(Clone)]
+    struct ChunkHintedIterator<I: ExactSizeIterator + Iterator + Clone> {
+        iter: I,
+        chunk_remaining: usize,
+        chunk_size: usize,
+        hint_total_size: bool,
+    }
+    impl<I: ExactSizeIterator + Iterator + Clone> Iterator for ChunkHintedIterator<I> {
+        type Item = I::Item;
+        fn next(&mut self) -> Option<Self::Item> {
+            if self.chunk_remaining == 0 {
+                self.chunk_remaining = ::core::cmp::min(self.chunk_size,
+                                                        self.iter.len());
+            }
+            self.chunk_remaining = self.chunk_remaining.saturating_sub(1);
+
+            self.iter.next()
+        }
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            (self.chunk_remaining,
+             if self.hint_total_size { Some(self.iter.len()) } else { None })
+        }
+    }
+
+    #[derive(Clone)]
+    struct WindowHintedIterator<I: ExactSizeIterator + Iterator + Clone> {
+        iter: I,
+        window_size: usize,
+        hint_total_size: bool,
+    }
+    impl<I: ExactSizeIterator + Iterator + Clone> Iterator for WindowHintedIterator<I> {
+        type Item = I::Item;
+        fn next(&mut self) -> Option<Self::Item> {
+            self.iter.next()
+        }
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            (::core::cmp::min(self.iter.len(), self.window_size),
+             if self.hint_total_size { Some(self.iter.len()) } else { None })
+        }
+    }
+
+    #[test]
+    fn test_iterator_choose() {
+        let r = &mut ::test::rng(109);
+        fn test_iter<R: Rng + ?Sized, Iter: Iterator<Item=usize> + Clone>(r: &mut R, iter: Iter) {
+            let mut chosen = [0i32; 9];
+            for _ in 0..1000 {
+                let picked = iter.clone().choose(r).unwrap();
+                chosen[picked] += 1;
+            }
+            for count in chosen.iter() {
+                // Samples should follow Binomial(1000, 1/9)
+                // Octave: binopdf(x, 1000, 1/9) gives the prob of *count == x
+                // Note: have seen 153, which is unlikely but not impossible.
+                assert!(72 < *count && *count < 154, "count not close to 1000/9: {}", count);
+            }
+        }
+
+        test_iter(r, 0..9);
+        test_iter(r, [0, 1, 2, 3, 4, 5, 6, 7, 8].iter().cloned());
+        #[cfg(feature = "alloc")]
+        test_iter(r, (0..9).collect::<Vec<_>>().into_iter());
+        test_iter(r, UnhintedIterator { iter: 0..9 });
+        test_iter(r, ChunkHintedIterator { iter: 0..9, chunk_size: 4, chunk_remaining: 4, hint_total_size: false });
+        test_iter(r, ChunkHintedIterator { iter: 0..9, chunk_size: 4, chunk_remaining: 4, hint_total_size: true });
+        test_iter(r, WindowHintedIterator { iter: 0..9, window_size: 2, hint_total_size: false });
+        test_iter(r, WindowHintedIterator { iter: 0..9, window_size: 2, hint_total_size: true });
+
+        assert_eq!((0..0).choose(r), None);
+        assert_eq!(UnhintedIterator{ iter: 0..0 }.choose(r), None);
+    }
+
+    #[test]
+    fn test_shuffle() {
+        let mut r = ::test::rng(108);
+        let empty: &mut [isize] = &mut [];
+        empty.shuffle(&mut r);
+        let mut one = [1];
+        one.shuffle(&mut r);
+        let b: &[_] = &[1];
+        assert_eq!(one, b);
+
+        let mut two = [1, 2];
+        two.shuffle(&mut r);
+        assert!(two == [1, 2] || two == [2, 1]);
+
+        fn move_last(slice: &mut [usize], pos: usize) {
+            // use slice[pos..].rotate_left(1); once we can use that
+            let last_val = slice[pos];
+            for i in pos..slice.len() - 1 {
+                slice[i] = slice[i + 1];
+            }
+            *slice.last_mut().unwrap() = last_val;
+        }
+        let mut counts = [0i32; 24];
+        for _ in 0..10000 {
+            let mut arr: [usize; 4] = [0, 1, 2, 3];
+            arr.shuffle(&mut r);
+            let mut permutation = 0usize;
+            let mut pos_value = counts.len();
+            for i in 0..4 {
+                pos_value /= 4 - i;
+                let pos = arr.iter().position(|&x| x == i).unwrap();
+                assert!(pos < (4 - i));
+                permutation += pos * pos_value;
+                move_last(&mut arr, pos);
+                assert_eq!(arr[3], i);
+            }
+            for i in 0..4 {
+                assert_eq!(arr[i], i);
+            }
+            counts[permutation] += 1;
+        }
+        for count in counts.iter() {
+            let err = *count - 10000i32 / 24;
+            assert!(-50 <= err && err <= 50);
+        }
+    }
+    
+    #[test]
+    fn test_partial_shuffle() {
+        let mut r = ::test::rng(118);
+        
+        let mut empty: [u32; 0] = [];
+        let res = empty.partial_shuffle(&mut r, 10);
+        assert_eq!((res.0.len(), res.1.len()), (0, 0));
+        
+        let mut v = [1, 2, 3, 4, 5];
+        let res = v.partial_shuffle(&mut r, 2);
+        assert_eq!((res.0.len(), res.1.len()), (2, 3));
+        assert!(res.0[0] != res.0[1]);
+        // First elements are only modified if selected, so at least one isn't modified:
+        assert!(res.1[0] == 1 || res.1[1] == 2 || res.1[2] == 3);
+    }
+
+    #[test]
+    #[cfg(feature = "alloc")]
+    fn test_sample_iter() {
+        let min_val = 1;
+        let max_val = 100;
+
+        let mut r = ::test::rng(401);
+        let vals = (min_val..max_val).collect::<Vec<i32>>();
+        let small_sample = vals.iter().choose_multiple(&mut r, 5);
+        let large_sample = vals.iter().choose_multiple(&mut r, vals.len() + 5);
+
+        assert_eq!(small_sample.len(), 5);
+        assert_eq!(large_sample.len(), vals.len());
+        // no randomization happens when amount >= len
+        assert_eq!(large_sample, vals.iter().collect::<Vec<_>>());
+
+        assert!(small_sample.iter().all(|e| {
+            **e >= min_val && **e <= max_val
+        }));
+    }
+    
+    #[test]
+    #[cfg(feature = "alloc")]
+    #[allow(deprecated)]
+    fn test_sample_slice_boundaries() {
+        let empty: &[u8] = &[];
+
+        let mut r = ::test::rng(402);
+
+        // sample 0 items
+        assert_eq!(&sample_slice(&mut r, empty, 0)[..], [0u8; 0]);
+        assert_eq!(&sample_slice(&mut r, &[42, 2, 42], 0)[..], [0u8; 0]);
+
+        // sample 1 item
+        assert_eq!(&sample_slice(&mut r, &[42], 1)[..], [42]);
+        let v = sample_slice(&mut r, &[1, 42], 1)[0];
+        assert!(v == 1 || v == 42);
+
+        // sample "all" the items
+        let v = sample_slice(&mut r, &[42, 133], 2);
+        assert!(&v[..] == [42, 133] || v[..] == [133, 42]);
+
+        // Make sure lucky 777's aren't lucky
+        let slice = &[42, 777];
+        let mut num_42 = 0;
+        let total = 1000;
+        for _ in 0..total {
+            let v = sample_slice(&mut r, slice, 1);
+            assert_eq!(v.len(), 1);
+            let v = v[0];
+            assert!(v == 42 || v == 777);
+            if v == 42 {
+                num_42 += 1;
+            }
+        }
+        let ratio_42 = num_42 as f64 / 1000 as f64;
+        assert!(0.4 <= ratio_42 || ratio_42 <= 0.6, "{}", ratio_42);
+    }
+
+    #[test]
+    #[cfg(feature = "alloc")]
+    #[allow(deprecated)]
+    fn test_sample_slice() {
+        let seeded_rng = SmallRng::from_seed;
+
+        let mut r = ::test::rng(403);
+
+        for n in 1..20 {
+            let length = 5*n - 4;   // 1, 6, ...
+            let amount = r.gen_range(0, length);
+            let mut seed = [0u8; 16];
+            r.fill(&mut seed);
+
+            // assert the basics work
+            let regular = index::sample(&mut seeded_rng(seed), length, amount);
+            assert_eq!(regular.len(), amount);
+            assert!(regular.iter().all(|e| e < length));
+
+            // also test that sampling the slice works
+            let vec: Vec<u32> = (0..(length as u32)).collect();
+            let result = sample_slice(&mut seeded_rng(seed), &vec, amount);
+            assert_eq!(result, regular.iter().map(|i| i as u32).collect::<Vec<_>>());
+
+            let result = sample_slice_ref(&mut seeded_rng(seed), &vec, amount);
+            assert!(result.iter().zip(regular.iter()).all(|(i,j)| **i == j as u32));
+        }
+    }
+    
+    #[test]
+    #[cfg(feature = "alloc")]
+    fn test_weighted() {
+        let mut r = ::test::rng(406);
+        const N_REPS: u32 = 3000;
+        let weights = [1u32, 2, 3, 0, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7];
+        let total_weight = weights.iter().sum::<u32>() as f32;
+
+        let verify = |result: [i32; 14]| {
+            for (i, count) in result.iter().enumerate() {
+                let exp = (weights[i] * N_REPS) as f32 / total_weight;
+                let mut err = (*count as f32 - exp).abs();
+                if err != 0.0 {
+                    err /= exp;
+                }
+                assert!(err <= 0.25);
+            }
+        };
+
+        // choose_weighted
+        fn get_weight<T>(item: &(u32, T)) -> u32 {
+            item.0
+        }
+        let mut chosen = [0i32; 14];
+        let mut items = [(0u32, 0usize); 14]; // (weight, index)
+        for (i, item) in items.iter_mut().enumerate() {
+            *item = (weights[i], i);
+        }
+        for _ in 0..N_REPS {
+            let item = items.choose_weighted(&mut r, get_weight).unwrap();
+            chosen[item.1] += 1;
+        }
+        verify(chosen);
+
+        // choose_weighted_mut
+        let mut items = [(0u32, 0i32); 14]; // (weight, count)
+        for (i, item) in items.iter_mut().enumerate() {
+            *item = (weights[i], 0);
+        }
+        for _ in 0..N_REPS {
+            items.choose_weighted_mut(&mut r, get_weight).unwrap().1 += 1;
+        }
+        for (ch, item) in chosen.iter_mut().zip(items.iter()) {
+            *ch = item.1;
+        }
+        verify(chosen);
+
+        // Check error cases
+        let empty_slice = &mut [10][0..0];
+        assert_eq!(empty_slice.choose_weighted(&mut r, |_| 1), Err(WeightedError::NoItem));
+        assert_eq!(empty_slice.choose_weighted_mut(&mut r, |_| 1), Err(WeightedError::NoItem));
+        assert_eq!(['x'].choose_weighted_mut(&mut r, |_| 0), Err(WeightedError::AllWeightsZero));
+        assert_eq!([0, -1].choose_weighted_mut(&mut r, |x| *x), Err(WeightedError::NegativeWeight));
+        assert_eq!([-1, 0].choose_weighted_mut(&mut r, |x| *x), Err(WeightedError::NegativeWeight));
+    }
+}
diff --git a/rand/tests/uniformity.rs b/rand/tests/uniformity.rs
new file mode 100644
index 0000000..b8f74a6
--- /dev/null
+++ b/rand/tests/uniformity.rs
@@ -0,0 +1,67 @@
+// Copyright 2018 Developers of the Rand project.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![cfg(feature = "std")]
+
+#[macro_use]
+extern crate average;
+extern crate rand;
+
+use std as core;
+use rand::FromEntropy;
+use rand::distributions::Distribution;
+use average::Histogram;
+
+const N_BINS: usize = 100;
+const N_SAMPLES: u32 = 1_000_000;
+const TOL: f64 = 1e-3;
+define_histogram!(hist, 100);
+use hist::Histogram as Histogram100;
+
+#[test]
+fn unit_sphere() {
+    const N_DIM: usize = 3;
+    let h = Histogram100::with_const_width(-1., 1.);
+    let mut histograms = [h.clone(), h.clone(), h];
+    let dist = rand::distributions::UnitSphereSurface::new();
+    let mut rng = rand::rngs::SmallRng::from_entropy();
+    for _ in 0..N_SAMPLES {
+        let v = dist.sample(&mut rng);
+        for i in 0..N_DIM {
+            histograms[i].add(v[i]).map_err(
+                |e| { println!("v: {}", v[i]); e }
+            ).unwrap();
+        }
+    }
+    for h in &histograms {
+        let sum: u64 = h.bins().iter().sum();
+        println!("{:?}", h);
+        for &b in h.bins() {
+            let p = (b as f64) / (sum as f64);
+            assert!((p - 1.0 / (N_BINS as f64)).abs() < TOL, "{}", p);
+        }
+    }
+}
+
+#[test]
+fn unit_circle() {
+    use ::std::f64::consts::PI;
+    let mut h = Histogram100::with_const_width(-PI, PI);
+    let dist = rand::distributions::UnitCircle::new();
+    let mut rng = rand::rngs::SmallRng::from_entropy();
+    for _ in 0..N_SAMPLES {
+        let v = dist.sample(&mut rng);
+        h.add(v[0].atan2(v[1])).unwrap();
+    }
+    let sum: u64 = h.bins().iter().sum();
+    println!("{:?}", h);
+    for &b in h.bins() {
+        let p = (b as f64) / (sum as f64);
+        assert!((p - 1.0 / (N_BINS as f64)).abs() < TOL, "{}", p);
+    }
+}
diff --git a/rand/utils/ci/install.sh b/rand/utils/ci/install.sh
new file mode 100644
index 0000000..8e636e1
--- /dev/null
+++ b/rand/utils/ci/install.sh
@@ -0,0 +1,49 @@
+# From https://github.com/japaric/trust
+
+set -ex
+
+main() {
+    local target=
+    if [ $TRAVIS_OS_NAME = linux ]; then
+        target=x86_64-unknown-linux-musl
+        sort=sort
+    else
+        target=x86_64-apple-darwin
+        sort=gsort  # for `sort --sort-version`, from brew's coreutils.
+    fi
+
+    # Builds for iOS are done on OSX, but require the specific target to be
+    # installed.
+    case $TARGET in
+        aarch64-apple-ios)
+            rustup target install aarch64-apple-ios
+            ;;
+        armv7-apple-ios)
+            rustup target install armv7-apple-ios
+            ;;
+        armv7s-apple-ios)
+            rustup target install armv7s-apple-ios
+            ;;
+        i386-apple-ios)
+            rustup target install i386-apple-ios
+            ;;
+        x86_64-apple-ios)
+            rustup target install x86_64-apple-ios
+            ;;
+    esac
+
+    # This fetches latest stable release
+    local tag=$(git ls-remote --tags --refs --exit-code https://github.com/japaric/cross \
+                       | cut -d/ -f3 \
+                       | grep -E '^v[0.1.0-9.]+$' \
+                       | $sort --version-sort \
+                       | tail -n1)
+    curl -LSfs https://japaric.github.io/trust/install.sh | \
+        sh -s -- \
+           --force \
+           --git japaric/cross \
+           --tag $tag \
+           --target $target
+}
+
+main
diff --git a/rand/utils/ci/script.sh b/rand/utils/ci/script.sh
new file mode 100644
index 0000000..33786f6
--- /dev/null
+++ b/rand/utils/ci/script.sh
@@ -0,0 +1,22 @@
+# Derived from https://github.com/japaric/trust
+
+set -ex
+
+main() {
+    cross test --target $TARGET --lib --no-default-features
+  # TODO: add simd_support feature:
+    cross test --target $TARGET --features=serde1,log
+    cross test --target $TARGET --examples
+    cross test --target $TARGET --manifest-path rand_core/Cargo.toml
+    cross test --target $TARGET --manifest-path rand_core/Cargo.toml --no-default-features
+    cross test --target $TARGET --manifest-path rand_isaac/Cargo.toml --features=serde1
+    cross test --target $TARGET --manifest-path rand_pcg/Cargo.toml --features=serde1
+    cross test --target $TARGET --manifest-path rand_xorshift/Cargo.toml --features=serde1
+    cross test --target $TARGET --manifest-path rand_chacha/Cargo.toml
+    cross test --target $TARGET --manifest-path rand_hc/Cargo.toml
+}
+
+# we don't run the "test phase" when doing deploys
+if [ -z $TRAVIS_TAG ]; then
+    main
+fi
diff --git a/rand/utils/ziggurat_tables.py b/rand/utils/ziggurat_tables.py
index 762f956..88cfdab 100755
--- a/rand/utils/ziggurat_tables.py
+++ b/rand/utils/ziggurat_tables.py
@@ -1,12 +1,11 @@
 #!/usr/bin/env python
 #
-# Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-# file at the top-level directory of this distribution and at
-# http://rust-lang.org/COPYRIGHT.
+# Copyright 2018 Developers of the Rand project.
+# Copyright 2013 The Rust Project Developers.
 #
 # Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 # option. This file may not be copied, modified, or distributed
 # except according to those terms.
 
@@ -105,13 +104,12 @@ def render_table(name, values):
 
 
 with open('ziggurat_tables.rs', 'w') as f:
-    f.write('''// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
+    f.write('''// Copyright 2018 Developers of the Rand project.
+// Copyright 2013 The Rust Project Developers.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
diff --git a/rustc_version/.gitignore b/rustc_version/.gitignore
new file mode 100644
index 0000000..a9d37c5
--- /dev/null
+++ b/rustc_version/.gitignore
@@ -0,0 +1,2 @@
+target
+Cargo.lock
diff --git a/rustc_version/.travis.yml b/rustc_version/.travis.yml
new file mode 100644
index 0000000..ccb8411
--- /dev/null
+++ b/rustc_version/.travis.yml
@@ -0,0 +1,21 @@
+language: rust
+rust:
+- nightly
+- beta
+- stable
+before_script:
+- |
+  pip install 'travis-cargo<0.2' --user &&
+  export PATH=$HOME/.local/bin:$PATH
+script:
+- |
+  travis-cargo build &&
+  travis-cargo test &&
+  travis-cargo bench &&
+  travis-cargo --only stable doc
+after_success:
+- travis-cargo --only stable doc-upload
+env:
+  global:
+  - TRAVIS_CARGO_NIGHTLY_FEATURE=""
+  - secure: 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
diff --git a/rustc_version/Cargo.toml b/rustc_version/Cargo.toml
new file mode 100644
index 0000000..422a881
--- /dev/null
+++ b/rustc_version/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "rustc_version"
+version = "0.2.3"
+authors = ["Marvin Löbel <loebel.marvin@gmail.com>"]
+license = "MIT/Apache-2.0"
+
+description = "A library for querying the version of a installed rustc compiler"
+readme = "README.md"
+documentation = "https://docs.rs/rustc_version/"
+
+repository = "https://github.com/Kimundi/rustc-version-rs"
+keywords = ["version", "rustc"]
+
+[badges]
+travis-ci = { repository = "Kimundi/rustc-version-rs" }
+
+[dependencies]
+semver = "0.9"
diff --git a/rustc_version/LICENSE-APACHE b/rustc_version/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/rustc_version/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
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+   "Licensor" shall mean the copyright owner or entity authorized by
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+   "Legal Entity" shall mean the union of the acting entity and all
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+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
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+   including but not limited to software source code, documentation
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+   "Object" form shall mean any form resulting from mechanical
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+   "Work" shall mean the work of authorship, whether in Source or
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+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
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+   "Contribution" shall mean any work of authorship, including
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+   "Contributor" shall mean Licensor and any individual or Legal Entity
+   on behalf of whom a Contribution has been received by Licensor and
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+2. Grant of Copyright License. Subject to the terms and conditions of
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+4. Redistribution. You may reproduce and distribute copies of the
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+   meet the following conditions:
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+   (a) You must give any other recipients of the Work or
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+
+   (b) You must cause any modified files to carry prominent notices
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+
+   (c) You must retain, in the Source form of any Derivative Works
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+
+   (d) If the Work includes a "NOTICE" text file as part of its
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+       of the NOTICE file are for informational purposes only and
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+       notices within Derivative Works that You distribute, alongside
+       or as an addendum to the NOTICE text from the Work, provided
+       that such additional attribution notices cannot be construed
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+
+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
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+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
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+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
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+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
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+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
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+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/rustc_version/LICENSE-MIT b/rustc_version/LICENSE-MIT
new file mode 100644
index 0000000..40b8817
--- /dev/null
+++ b/rustc_version/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2016 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/rustc_version/README.md b/rustc_version/README.md
new file mode 100644
index 0000000..f491ca9
--- /dev/null
+++ b/rustc_version/README.md
@@ -0,0 +1,75 @@
+rustc-version-rs
+==============
+
+A library for querying the version of a `rustc` compiler.
+
+This can be used by build scripts or other tools dealing with Rust sources
+to make decisions based on the version of the compiler.
+
+[![Travis-CI Status](https://travis-ci.org/Kimundi/rustc-version-rs.png?branch=master)](https://travis-ci.org/Kimundi/rustc-version-rs)
+
+# Getting Started
+
+[rustc-version-rs is available on crates.io](https://crates.io/crates/rustc_version).
+It is recommended to look there for the newest released version, as well as links to the newest builds of the docs.
+
+At the point of the last update of this README, the latest published version could be used like this:
+
+Add the following dependency to your Cargo manifest...
+
+```toml
+[build-dependencies]
+rustc_version = "0.2"
+```
+
+...and see the [docs](http://kimundi.github.io/rustc-version-rs/rustc_version/index.html) for how to use it.
+
+# Example
+
+```rust
+// This could be a cargo build script
+
+extern crate rustc_version;
+use rustc_version::{version, version_meta, Channel, Version};
+
+fn main() {
+    // Assert we haven't travelled back in time
+    assert!(version().unwrap().major >= 1);
+
+    // Set cfg flags depending on release channel
+    match version_meta().unwrap().channel {
+        Channel::Stable => {
+            println!("cargo:rustc-cfg=RUSTC_IS_STABLE");
+        }
+        Channel::Beta => {
+            println!("cargo:rustc-cfg=RUSTC_IS_BETA");
+        }
+        Channel::Nightly => {
+            println!("cargo:rustc-cfg=RUSTC_IS_NIGHTLY");
+        }
+        Channel::Dev => {
+            println!("cargo:rustc-cfg=RUSTC_IS_DEV");
+        }
+    }
+
+    // Check for a minimum version
+    if version().unwrap() >= Version::parse("1.4.0").unwrap() {
+        println!("cargo:rustc-cfg=compiler_has_important_bugfix");
+    }
+}
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any
+additional terms or conditions.
diff --git a/rustc_version/src/errors.rs b/rustc_version/src/errors.rs
new file mode 100644
index 0000000..54557b6
--- /dev/null
+++ b/rustc_version/src/errors.rs
@@ -0,0 +1,79 @@
+use std::{self, error, fmt, io, str};
+use semver::{self, Identifier};
+
+/// The error type for this crate.
+#[derive(Debug)]
+pub enum Error {
+    /// An error ocurrend when executing the `rustc` command.
+    CouldNotExecuteCommand(io::Error),
+    /// The output of `rustc -vV` was not valid utf-8.
+    Utf8Error(str::Utf8Error),
+    /// The output of `rustc -vV` was not in the expected format.
+    UnexpectedVersionFormat,
+    /// An error ocurred in parsing a `VersionReq`.
+    ReqParseError(semver::ReqParseError),
+    /// An error ocurred in parsing the semver.
+    SemVerError(semver::SemVerError),
+    /// The pre-release tag is unknown.
+    UnknownPreReleaseTag(Identifier),
+}
+use Error::*;
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use std::error::Error;
+        match *self {
+            CouldNotExecuteCommand(ref e) => write!(f, "{}: {}", self.description(), e),
+            Utf8Error(_) => write!(f, "{}", self.description()),
+            UnexpectedVersionFormat => write!(f, "{}", self.description()),
+            ReqParseError(ref e) => write!(f, "{}: {}", self.description(), e),
+            SemVerError(ref e) => write!(f, "{}: {}", self.description(), e),
+            UnknownPreReleaseTag(ref i) => write!(f, "{}: {}", self.description(), i),
+        }
+    }
+}
+
+impl error::Error for Error {
+    fn cause(&self) -> Option<&error::Error> {
+        match *self {
+            CouldNotExecuteCommand(ref e) => Some(e),
+            Utf8Error(ref e) => Some(e),
+            UnexpectedVersionFormat => None,
+            ReqParseError(ref e) => Some(e),
+            SemVerError(ref e) => Some(e),
+            UnknownPreReleaseTag(_) => None,
+        }
+    }
+
+    fn description(&self) -> &str {
+        match *self {
+            CouldNotExecuteCommand(_) => "could not execute command",
+            Utf8Error(_) => "invalid UTF-8 output from `rustc -vV`",
+            UnexpectedVersionFormat => "unexpected `rustc -vV` format",
+            ReqParseError(_) => "error parsing version requirement",
+            SemVerError(_) => "error parsing version",
+            UnknownPreReleaseTag(_) => "unknown pre-release tag",
+        }
+    }
+}
+
+macro_rules! impl_from {
+    ($($err_ty:ty => $variant:ident),* $(,)*) => {
+        $(
+            impl From<$err_ty> for Error {
+                fn from(e: $err_ty) -> Error {
+                    Error::$variant(e)
+                }
+            }
+        )*
+    }
+}
+
+impl_from! {
+    str::Utf8Error => Utf8Error,
+    semver::SemVerError => SemVerError,
+    semver::ReqParseError => ReqParseError,
+}
+
+/// The result type for this crate.
+pub type Result<T> = std::result::Result<T, Error>;
diff --git a/rustc_version/src/lib.rs b/rustc_version/src/lib.rs
new file mode 100644
index 0000000..c038288
--- /dev/null
+++ b/rustc_version/src/lib.rs
@@ -0,0 +1,347 @@
+// Copyright 2016 rustc-version-rs developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![warn(missing_docs)]
+
+//! Simple library for getting the version information of a `rustc`
+//! compiler.
+//!
+//! This can be used by build scripts or other tools dealing with Rust sources
+//! to make decisions based on the version of the compiler.
+//!
+//! It calls `$RUSTC --version -v` and parses the output, falling
+//! back to `rustc` if `$RUSTC` is not set.
+//!
+//! # Example
+//!
+//! ```rust
+//! // This could be a cargo build script
+//!
+//! extern crate rustc_version;
+//! use rustc_version::{version, version_meta, Channel, Version};
+//!
+//! fn main() {
+//!     // Assert we haven't travelled back in time
+//!     assert!(version().unwrap().major >= 1);
+//!
+//!     // Set cfg flags depending on release channel
+//!     match version_meta().unwrap().channel {
+//!         Channel::Stable => {
+//!             println!("cargo:rustc-cfg=RUSTC_IS_STABLE");
+//!         }
+//!         Channel::Beta => {
+//!             println!("cargo:rustc-cfg=RUSTC_IS_BETA");
+//!         }
+//!         Channel::Nightly => {
+//!             println!("cargo:rustc-cfg=RUSTC_IS_NIGHTLY");
+//!         }
+//!         Channel::Dev => {
+//!             println!("cargo:rustc-cfg=RUSTC_IS_DEV");
+//!         }
+//!     }
+//!
+//!     // Check for a minimum version
+//!     if version().unwrap() >= Version::parse("1.4.0").unwrap() {
+//!         println!("cargo:rustc-cfg=compiler_has_important_bugfix");
+//!     }
+//! }
+//! ```
+
+extern crate semver;
+use semver::Identifier;
+use std::process::Command;
+use std::{env, str};
+use std::ffi::OsString;
+
+// Convenience re-export to allow version comparison without needing to add
+// semver crate.
+pub use semver::Version;
+
+mod errors;
+pub use errors::{Error, Result};
+
+/// Release channel of the compiler.
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
+pub enum Channel {
+    /// Development release channel
+    Dev,
+    /// Nightly release channel
+    Nightly,
+    /// Beta release channel
+    Beta,
+    /// Stable release channel
+    Stable,
+}
+
+/// Rustc version plus metada like git short hash and build date.
+#[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct VersionMeta {
+    /// Version of the compiler
+    pub semver: Version,
+
+    /// Git short hash of the build of the compiler
+    pub commit_hash: Option<String>,
+
+    /// Commit date of the compiler
+    pub commit_date: Option<String>,
+
+    /// Build date of the compiler; this was removed between Rust 1.0.0 and 1.1.0.
+    pub build_date: Option<String>,
+
+    /// Release channel of the compiler
+    pub channel: Channel,
+
+    /// Host target triple of the compiler
+    pub host: String,
+
+    /// Short version string of the compiler
+    pub short_version_string: String,
+}
+
+impl VersionMeta {
+    /// Returns the version metadata for `cmd`, which should be a `rustc` command.
+    pub fn for_command(cmd: Command) -> Result<VersionMeta> {
+        let mut cmd = cmd;
+
+        let out = cmd.arg("-vV").output().map_err(Error::CouldNotExecuteCommand)?;
+        let out = str::from_utf8(&out.stdout)?;
+
+        version_meta_for(out)
+    }
+}
+
+/// Returns the `rustc` SemVer version.
+pub fn version() -> Result<Version> {
+    Ok(version_meta()?.semver)
+}
+
+/// Returns the `rustc` SemVer version and additional metadata
+/// like the git short hash and build date.
+pub fn version_meta() -> Result<VersionMeta> {
+    let cmd = env::var_os("RUSTC").unwrap_or_else(|| OsString::from("rustc"));
+
+    VersionMeta::for_command(Command::new(cmd))
+}
+
+/// Parses a "rustc -vV" output string and returns
+/// the SemVer version and additional metadata
+/// like the git short hash and build date.
+pub fn version_meta_for(verbose_version_string: &str) -> Result<VersionMeta> {
+    let out: Vec<_> = verbose_version_string.lines().collect();
+
+    if !(out.len() >= 6 && out.len() <= 8) {
+        return Err(Error::UnexpectedVersionFormat);
+    }
+
+    let short_version_string = out[0];
+
+    fn expect_prefix<'a>(line: &'a str, prefix: &str) -> Result<&'a str> {
+        if line.starts_with(prefix) {
+            Ok(&line[prefix.len()..])
+        } else {
+            Err(Error::UnexpectedVersionFormat)
+        }
+    }
+
+    let commit_hash = match expect_prefix(out[2], "commit-hash: ")? {
+        "unknown" => None,
+        hash => Some(hash.to_owned()),
+    };
+
+    let commit_date = match expect_prefix(out[3], "commit-date: ")? {
+        "unknown" => None,
+        hash => Some(hash.to_owned()),
+    };
+
+    // Handle that the build date may or may not be present.
+    let mut idx = 4;
+    let mut build_date = None;
+    if out[idx].starts_with("build-date") {
+        build_date = match expect_prefix(out[idx], "build-date: ")? {
+            "unknown" => None,
+            s => Some(s.to_owned()),
+        };
+        idx += 1;
+    }
+
+    let host = expect_prefix(out[idx], "host: ")?;
+    idx += 1;
+    let release = expect_prefix(out[idx], "release: ")?;
+
+    let semver: Version = release.parse()?;
+
+    let channel = if semver.pre.is_empty() {
+        Channel::Stable
+    } else {
+        match semver.pre[0] {
+            Identifier::AlphaNumeric(ref s) if s == "dev" => Channel::Dev,
+            Identifier::AlphaNumeric(ref s) if s == "beta" => Channel::Beta,
+            Identifier::AlphaNumeric(ref s) if s == "nightly" => Channel::Nightly,
+            ref x => return Err(Error::UnknownPreReleaseTag(x.clone())),
+        }
+    };
+
+    Ok(VersionMeta {
+        semver: semver,
+        commit_hash: commit_hash,
+        commit_date: commit_date,
+        build_date: build_date,
+        channel: channel,
+        host: host.into(),
+        short_version_string: short_version_string.into(),
+    })
+}
+
+#[test]
+fn smoketest() {
+    let v = version().unwrap();
+    assert!(v.major >= 1);
+
+    let v = version_meta().unwrap();
+    assert!(v.semver.major >= 1);
+
+    assert!(version().unwrap() >= Version::parse("1.0.0").unwrap());
+}
+
+#[test]
+fn parse_unexpected() {
+    let res = version_meta_for(
+"rustc 1.0.0 (a59de37e9 2015-05-13) (built 2015-05-14)
+binary: rustc
+commit-hash: a59de37e99060162a2674e3ff45409ac73595c0e
+commit-date: 2015-05-13
+rust-birthday: 2015-05-14
+host: x86_64-unknown-linux-gnu
+release: 1.0.0");
+
+    assert!(match res {
+        Err(Error::UnexpectedVersionFormat) => true,
+        _ => false,
+    });
+
+}
+
+#[test]
+fn parse_1_0_0() {
+    let version = version_meta_for(
+"rustc 1.0.0 (a59de37e9 2015-05-13) (built 2015-05-14)
+binary: rustc
+commit-hash: a59de37e99060162a2674e3ff45409ac73595c0e
+commit-date: 2015-05-13
+build-date: 2015-05-14
+host: x86_64-unknown-linux-gnu
+release: 1.0.0").unwrap();
+
+    assert_eq!(version.semver, Version::parse("1.0.0").unwrap());
+    assert_eq!(version.commit_hash, Some("a59de37e99060162a2674e3ff45409ac73595c0e".into()));
+    assert_eq!(version.commit_date, Some("2015-05-13".into()));
+    assert_eq!(version.build_date, Some("2015-05-14".into()));
+    assert_eq!(version.channel, Channel::Stable);
+    assert_eq!(version.host, "x86_64-unknown-linux-gnu");
+    assert_eq!(version.short_version_string, "rustc 1.0.0 (a59de37e9 2015-05-13) (built 2015-05-14)");
+}
+
+
+#[test]
+fn parse_unknown() {
+    let version = version_meta_for(
+"rustc 1.3.0
+binary: rustc
+commit-hash: unknown
+commit-date: unknown
+host: x86_64-unknown-linux-gnu
+release: 1.3.0").unwrap();
+
+    assert_eq!(version.semver, Version::parse("1.3.0").unwrap());
+    assert_eq!(version.commit_hash, None);
+    assert_eq!(version.commit_date, None);
+    assert_eq!(version.channel, Channel::Stable);
+    assert_eq!(version.host, "x86_64-unknown-linux-gnu");
+    assert_eq!(version.short_version_string, "rustc 1.3.0");
+}
+
+#[test]
+fn parse_nightly() {
+    let version = version_meta_for(
+"rustc 1.5.0-nightly (65d5c0833 2015-09-29)
+binary: rustc
+commit-hash: 65d5c083377645a115c4ac23a620d3581b9562b6
+commit-date: 2015-09-29
+host: x86_64-unknown-linux-gnu
+release: 1.5.0-nightly").unwrap();
+
+    assert_eq!(version.semver, Version::parse("1.5.0-nightly").unwrap());
+    assert_eq!(version.commit_hash, Some("65d5c083377645a115c4ac23a620d3581b9562b6".into()));
+    assert_eq!(version.commit_date, Some("2015-09-29".into()));
+    assert_eq!(version.channel, Channel::Nightly);
+    assert_eq!(version.host, "x86_64-unknown-linux-gnu");
+    assert_eq!(version.short_version_string, "rustc 1.5.0-nightly (65d5c0833 2015-09-29)");
+}
+
+#[test]
+fn parse_stable() {
+    let version = version_meta_for(
+"rustc 1.3.0 (9a92aaf19 2015-09-15)
+binary: rustc
+commit-hash: 9a92aaf19a64603b02b4130fe52958cc12488900
+commit-date: 2015-09-15
+host: x86_64-unknown-linux-gnu
+release: 1.3.0").unwrap();
+
+    assert_eq!(version.semver, Version::parse("1.3.0").unwrap());
+    assert_eq!(version.commit_hash, Some("9a92aaf19a64603b02b4130fe52958cc12488900".into()));
+    assert_eq!(version.commit_date, Some("2015-09-15".into()));
+    assert_eq!(version.channel, Channel::Stable);
+    assert_eq!(version.host, "x86_64-unknown-linux-gnu");
+    assert_eq!(version.short_version_string, "rustc 1.3.0 (9a92aaf19 2015-09-15)");
+}
+
+#[test]
+fn parse_1_16_0_nightly() {
+    let version = version_meta_for(
+"rustc 1.16.0-nightly (5d994d8b7 2017-01-05)
+binary: rustc
+commit-hash: 5d994d8b7e482e87467d4a521911477bd8284ce3
+commit-date: 2017-01-05
+host: x86_64-unknown-linux-gnu
+release: 1.16.0-nightly
+LLVM version: 3.9").unwrap();
+
+    assert_eq!(version.semver, Version::parse("1.16.0-nightly").unwrap());
+    assert_eq!(version.commit_hash, Some("5d994d8b7e482e87467d4a521911477bd8284ce3".into()));
+    assert_eq!(version.commit_date, Some("2017-01-05".into()));
+    assert_eq!(version.channel, Channel::Nightly);
+    assert_eq!(version.host, "x86_64-unknown-linux-gnu");
+    assert_eq!(version.short_version_string, "rustc 1.16.0-nightly (5d994d8b7 2017-01-05)");
+}
+
+/*
+#[test]
+fn version_matches_replacement() {
+    let f = |s1: &str, s2: &str| {
+        let a = Version::parse(s1).unwrap();
+        let b = Version::parse(s2).unwrap();
+        println!("{} <= {} : {}", s1, s2, a <= b);
+    };
+
+    println!();
+
+    f("1.5.0",         "1.5.0");
+    f("1.5.0-nightly", "1.5.0");
+    f("1.5.0",         "1.5.0-nightly");
+    f("1.5.0-nightly", "1.5.0-nightly");
+
+    f("1.5.0",         "1.6.0");
+    f("1.5.0-nightly", "1.6.0");
+    f("1.5.0",         "1.6.0-nightly");
+    f("1.5.0-nightly", "1.6.0-nightly");
+
+    panic!();
+
+}
+*/
diff --git a/semver-parser/.gitignore b/semver-parser/.gitignore
new file mode 100644
index 0000000..a9d37c5
--- /dev/null
+++ b/semver-parser/.gitignore
@@ -0,0 +1,2 @@
+target
+Cargo.lock
diff --git a/semver-parser/Cargo.toml b/semver-parser/Cargo.toml
new file mode 100644
index 0000000..c2be878
--- /dev/null
+++ b/semver-parser/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "semver-parser"
+version = "0.7.0"
+authors = ["Steve Klabnik <steve@steveklabnik.com>"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/steveklabnik/semver-parser"
+homepage = "https://github.com/steveklabnik/semver-parser"
+documentation = "https://docs.rs/semver-parser"
+description = """
+Parsing of the semver spec.
+"""
diff --git a/semver-parser/LICENSE-APACHE b/semver-parser/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/semver-parser/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
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+   "License" shall mean the terms and conditions for use, reproduction,
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+
+   "You" (or "Your") shall mean an individual or Legal Entity
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+   "Work" shall mean the work of authorship, whether in Source or
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+   the conditions stated in this License.
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+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
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+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
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+6. Trademarks. This License does not grant permission to use the trade
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+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
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+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
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+APPENDIX: How to apply the Apache License to your work.
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+Copyright [yyyy] [name of copyright owner]
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+Licensed under the Apache License, Version 2.0 (the "License");
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+
+Unless required by applicable law or agreed to in writing, software
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diff --git a/semver-parser/LICENSE-MIT b/semver-parser/LICENSE-MIT
new file mode 100644
index 0000000..fb7494a
--- /dev/null
+++ b/semver-parser/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2016 Steve Klabnik
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/semver-parser/src/common.rs b/semver-parser/src/common.rs
new file mode 100644
index 0000000..267b4d9
--- /dev/null
+++ b/semver-parser/src/common.rs
@@ -0,0 +1,66 @@
+use version::Identifier;
+use recognize::{Recognize, Alt, OneOrMore, Inclusive, OneByte};
+use std::str::from_utf8;
+
+// by the time we get here, we know that it's all valid characters, so this doesn't need to return
+// a result or anything
+fn parse_meta(s: &str) -> Vec<Identifier> {
+    // Originally, I wanted to implement this method via calling parse, but parse is tolerant of
+    // leading zeroes, and we want anything with leading zeroes to be considered alphanumeric, not
+    // numeric. So the strategy is to check with a recognizer first, and then call parse once
+    // we've determined that it's a number without a leading zero.
+    s.split(".")
+        .map(|part| {
+            // another wrinkle: we made sure that any number starts with a
+            // non-zero. But there's a problem: an actual zero is a number, yet
+            // gets left out by this heuristic. So let's also check for the
+            // single, lone zero.
+            if is_alpha_numeric(part) {
+                Identifier::AlphaNumeric(part.to_string())
+            } else {
+                // we can unwrap here because we know it is only digits due to the regex
+                Identifier::Numeric(part.parse().unwrap())
+            }
+        }).collect()
+}
+
+// parse optional metadata (preceded by the prefix character)
+pub fn parse_optional_meta(s: &[u8], prefix_char: u8)-> Result<(Vec<Identifier>, usize), String> {
+    if let Some(len) = prefix_char.p(s) {
+        let start = len;
+        if let Some(len) = letters_numbers_dash_dot(&s[start..]) {
+            let end = start + len;
+            Ok((parse_meta(from_utf8(&s[start..end]).unwrap()), end))
+        } else {
+            Err("Error parsing prerelease".to_string())
+        }
+    } else {
+        Ok((Vec::new(), 0))
+    }
+}
+
+pub fn is_alpha_numeric(s: &str) -> bool {
+    if let Some((_val, len)) = numeric_identifier(s.as_bytes()) {
+        // Return true for number with leading zero
+        // Note: doing it this way also handily makes overflow fail over.
+        len != s.len()
+    } else {
+        true
+    }
+}
+
+// Note: could plumb overflow error up to return value as Result
+pub fn numeric_identifier(s: &[u8]) -> Option<(u64, usize)> {
+    if let Some(len) = Alt(b'0', OneOrMore(Inclusive(b'0'..b'9'))).p(s) {
+        from_utf8(&s[0..len]).unwrap().parse().ok().map(|val| (val, len))
+    } else {
+        None
+    }
+}
+
+pub fn letters_numbers_dash_dot(s: &[u8]) -> Option<usize> {
+    OneOrMore(OneByte(|c| c == b'-' || c == b'.' ||
+        (b'0' <= c && c <= b'9') ||
+        (b'a' <= c && c <= b'z') ||
+        (b'A' <= c && c <= b'Z'))).p(s)
+}
diff --git a/semver-parser/src/lib.rs b/semver-parser/src/lib.rs
new file mode 100644
index 0000000..3b0d8f0
--- /dev/null
+++ b/semver-parser/src/lib.rs
@@ -0,0 +1,8 @@
+pub mod version;
+pub mod range;
+
+// for private stuff the two share
+mod common;
+
+// for recognizer combinators
+mod recognize;
diff --git a/semver-parser/src/range.rs b/semver-parser/src/range.rs
new file mode 100644
index 0000000..858be9f
--- /dev/null
+++ b/semver-parser/src/range.rs
@@ -0,0 +1,696 @@
+use common::{self, numeric_identifier, letters_numbers_dash_dot};
+use version::Identifier;
+use std::str::{FromStr, from_utf8};
+use recognize::*;
+
+#[derive(Debug)]
+pub struct VersionReq {
+    pub predicates: Vec<Predicate>,
+}
+
+#[derive(PartialEq,Debug)]
+pub enum WildcardVersion {
+    Major,
+    Minor,
+    Patch,
+}
+
+#[derive(PartialEq,Debug)]
+pub enum Op {
+    Ex, // Exact
+    Gt, // Greater than
+    GtEq, // Greater than or equal to
+    Lt, // Less than
+    LtEq, // Less than or equal to
+    Tilde, // e.g. ~1.0.0
+    Compatible, // compatible by definition of semver, indicated by ^
+    Wildcard(WildcardVersion), // x.y.*, x.*, *
+}
+
+impl FromStr for Op {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Op, String> {
+        match s {
+            "=" => Ok(Op::Ex),
+            ">" => Ok(Op::Gt),
+            ">=" => Ok(Op::GtEq),
+            "<" => Ok(Op::Lt),
+            "<=" => Ok(Op::LtEq),
+            "~" => Ok(Op::Tilde),
+            "^" => Ok(Op::Compatible),
+            _ => Err(String::from("Could not parse Op")),
+        }
+    }
+}
+
+#[derive(PartialEq,Debug)]
+pub struct Predicate {
+    pub op: Op,
+    pub major: u64,
+    pub minor: Option<u64>,
+    pub patch: Option<u64>,
+    pub pre: Vec<Identifier>,
+}
+
+fn numeric_or_wild(s: &[u8]) -> Option<(Option<u64>, usize)> {
+    if let Some((val, len)) = numeric_identifier(s) {
+        Some((Some(val), len))
+    } else if let Some(len) = OneOf(b"*xX").p(s) {
+        Some((None, len))
+    } else {
+        None
+    }
+}
+
+fn dot_numeric_or_wild(s: &[u8]) -> Option<(Option<u64>, usize)> {
+    b'.'.p(s).and_then(|len|
+        numeric_or_wild(&s[len..]).map(|(val, len2)| (val, len + len2))
+    )
+}
+
+fn operation(s: &[u8]) -> Option<(Op, usize)> {
+    if let Some(len) = "=".p(s) {
+        Some((Op::Ex, len))
+    } else if let Some(len) = ">=".p(s) {
+        Some((Op::GtEq, len))
+    } else if let Some(len) = ">".p(s) {
+        Some((Op::Gt, len))
+    } else if let Some(len) = "<=".p(s) {
+        Some((Op::LtEq, len))
+    } else if let Some(len) = "<".p(s) {
+        Some((Op::Lt, len))
+    } else if let Some(len) = "~".p(s) {
+        Some((Op::Tilde, len))
+    } else if let Some(len) = "^".p(s) {
+        Some((Op::Compatible, len))
+    } else {
+        None
+    }
+}
+
+fn whitespace(s: &[u8]) -> Option<usize> {
+    ZeroOrMore(OneOf(b"\t\r\n ")).p(s)
+}
+
+pub fn parse_predicate(range: &str) -> Result<Predicate, String> {
+    let s = range.trim().as_bytes();
+    let mut i = 0;
+    let mut operation = if let Some((op, len)) = operation(&s[i..]) {
+        i += len;
+        op
+    } else {
+        // operations default to Compatible
+        Op::Compatible
+    };
+    if let Some(len) = whitespace.p(&s[i..]) {
+        i += len;
+    }
+    let major = if let Some((major, len)) = numeric_identifier(&s[i..]) {
+        i += len;
+        major
+    } else {
+        return Err("Error parsing major version number: ".to_string());
+    };
+    let minor = if let Some((minor, len)) = dot_numeric_or_wild(&s[i..]) {
+        i += len;
+        if minor.is_none() {
+            operation = Op::Wildcard(WildcardVersion::Minor);
+        }
+        minor
+    } else {
+        None
+    };
+    let patch = if let Some((patch, len)) = dot_numeric_or_wild(&s[i..]) {
+        i += len;
+        if patch.is_none() {
+            operation = Op::Wildcard(WildcardVersion::Patch);
+        }
+        patch
+    } else {
+        None
+    };
+    let (pre, pre_len) = common::parse_optional_meta(&s[i..], b'-')?;
+    i += pre_len;
+    if let Some(len) = (b'+', letters_numbers_dash_dot).p(&s[i..]) {
+        i += len;
+    }
+    if i != s.len() {
+        return Err("Extra junk after valid predicate: ".to_string() +
+            from_utf8(&s[i..]).unwrap());
+    }
+    Ok(Predicate {
+        op: operation,
+        major: major,
+        minor: minor,
+        patch: patch,
+        pre: pre,
+    })
+}
+
+pub fn parse(ranges: &str) -> Result<VersionReq, String> {
+    // null is an error
+    if ranges == "\0" {
+        return Err(String::from("Null is not a valid VersionReq"));
+    }
+
+    // an empty range is a major version wildcard
+    // so is a lone * or x of either capitalization
+    if (ranges == "")
+    || (ranges == "*")
+    || (ranges == "x")
+    || (ranges == "X") {
+        return Ok(VersionReq {
+            predicates: vec![Predicate {
+                op: Op::Wildcard(WildcardVersion::Major),
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            }],
+        });
+    }
+
+
+    let ranges = ranges.trim();
+
+    let predicates: Result<Vec<_>, String> = ranges
+        .split(",")
+        .map(|range| {
+            parse_predicate(range)
+        })
+        .collect();
+
+    let predicates = try!(predicates);
+
+    if predicates.len() == 0 {
+        return Err(String::from("VersionReq did not parse properly"));
+    }
+
+    Ok(VersionReq {
+        predicates: predicates,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use range;
+    use version::Identifier;
+
+    #[test]
+    fn test_parsing_default() {
+        let r = range::parse("1.0.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 1,
+                minor: Some(0),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_exact_01() {
+        let r = range::parse("=1.0.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Ex,
+                major: 1,
+                minor: Some(0),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_exact_02() {
+        let r = range::parse("=0.9.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Ex,
+                major: 0,
+                minor: Some(9),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_exact_03() {
+        let r = range::parse("=0.1.0-beta2.a").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Ex,
+                major: 0,
+                minor: Some(1),
+                patch: Some(0),
+                pre: vec![Identifier::AlphaNumeric(String::from("beta2")),
+                          Identifier::AlphaNumeric(String::from("a"))],
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_greater_than() {
+        let r = range::parse("> 1.0.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Gt,
+                major: 1,
+                minor: Some(0),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_greater_than_01() {
+        let r = range::parse(">= 1.0.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::GtEq,
+                major: 1,
+                minor: Some(0),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_greater_than_02() {
+        let r = range::parse(">= 2.1.0-alpha2").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::GtEq,
+                major: 2,
+                minor: Some(1),
+                patch: Some(0),
+                pre: vec![Identifier::AlphaNumeric(String::from("alpha2"))],
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_less_than() {
+        let r = range::parse("< 1.0.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Lt,
+                major: 1,
+                minor: Some(0),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_less_than_eq() {
+        let r = range::parse("<= 2.1.0-alpha2").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::LtEq,
+                major: 2,
+                minor: Some(1),
+                patch: Some(0),
+                pre: vec![Identifier::AlphaNumeric(String::from("alpha2"))],
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_tilde() {
+        let r = range::parse("~1").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Tilde,
+                major: 1,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_parsing_compatible() {
+        let r = range::parse("^0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_blank() {
+        let r = range::parse("").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Major),
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_wildcard() {
+        let r = range::parse("*").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Major),
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_x() {
+        let r = range::parse("x").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Major),
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_capital_x() {
+        let r = range::parse("X").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Major),
+                major: 0,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_minor_wildcard_star() {
+        let r = range::parse("1.*").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Minor),
+                major: 1,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_minor_wildcard_x() {
+        let r = range::parse("1.x").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Minor),
+                major: 1,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_minor_wildcard_capital_x() {
+        let r = range::parse("1.X").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Minor),
+                major: 1,
+                minor: None,
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_patch_wildcard_star() {
+        let r = range::parse("1.2.*").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Patch),
+                major: 1,
+                minor: Some(2),
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_patch_wildcard_x() {
+        let r = range::parse("1.2.x").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Patch),
+                major: 1,
+                minor: Some(2),
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    fn test_parsing_patch_wildcard_capital_x() {
+        let r = range::parse("1.2.X").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Wildcard(WildcardVersion::Patch),
+                major: 1,
+                minor: Some(2),
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+    }
+
+    #[test]
+    pub fn test_multiple_01() {
+        let r = range::parse("> 0.0.9, <= 2.5.3").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Gt,
+                major: 0,
+                minor: Some(0),
+                patch: Some(9),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::LtEq,
+                major: 2,
+                minor: Some(5),
+                patch: Some(3),
+                pre: Vec::new(),
+            },
+            r.predicates[1]
+        );
+    }
+
+    #[test]
+    pub fn test_multiple_02() {
+        let r = range::parse("0.3.0, 0.4.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: Some(3),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: Some(4),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[1]
+        );
+    }
+
+    #[test]
+    pub fn test_multiple_03() {
+        let r = range::parse("<= 0.2.0, >= 0.5.0").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::LtEq,
+                major: 0,
+                minor: Some(2),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::GtEq,
+                major: 0,
+                minor: Some(5),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[1]
+        );
+    }
+
+    #[test]
+    pub fn test_multiple_04() {
+        let r = range::parse("0.1.0, 0.1.4, 0.1.6").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: Some(1),
+                patch: Some(0),
+                pre: Vec::new(),
+            },
+            r.predicates[0]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: Some(1),
+                patch: Some(4),
+                pre: Vec::new(),
+            },
+            r.predicates[1]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::Compatible,
+                major: 0,
+                minor: Some(1),
+                patch: Some(6),
+                pre: Vec::new(),
+            },
+            r.predicates[2]
+        );
+    }
+
+    #[test]
+    pub fn test_multiple_05() {
+        let r = range::parse(">=0.5.1-alpha3, <0.6").unwrap();
+
+        assert_eq!(Predicate {
+                op: Op::GtEq,
+                major: 0,
+                minor: Some(5),
+                patch: Some(1),
+                pre: vec![Identifier::AlphaNumeric(String::from("alpha3"))],
+            },
+            r.predicates[0]
+        );
+
+        assert_eq!(Predicate {
+                op: Op::Lt,
+                major: 0,
+                minor: Some(6),
+                patch: None,
+                pre: Vec::new(),
+            },
+            r.predicates[1]
+        );
+    }
+
+    #[test]
+    fn test_parse_build_metadata_with_predicate() {
+        assert_eq!(range::parse("^1.2.3+meta").unwrap().predicates[0].op,
+                   Op::Compatible);
+        assert_eq!(range::parse("~1.2.3+meta").unwrap().predicates[0].op,
+                   Op::Tilde);
+        assert_eq!(range::parse("=1.2.3+meta").unwrap().predicates[0].op,
+                   Op::Ex);
+        assert_eq!(range::parse("<=1.2.3+meta").unwrap().predicates[0].op,
+                   Op::LtEq);
+        assert_eq!(range::parse(">=1.2.3+meta").unwrap().predicates[0].op,
+                   Op::GtEq);
+        assert_eq!(range::parse("<1.2.3+meta").unwrap().predicates[0].op,
+                   Op::Lt);
+        assert_eq!(range::parse(">1.2.3+meta").unwrap().predicates[0].op,
+                   Op::Gt);
+    }
+
+    #[test]
+    pub fn test_parse_errors() {
+        assert!(range::parse("\0").is_err());
+        assert!(range::parse(">= >= 0.0.2").is_err());
+        assert!(range::parse(">== 0.0.2").is_err());
+        assert!(range::parse("a.0.0").is_err());
+        assert!(range::parse("1.0.0-").is_err());
+        assert!(range::parse(">=").is_err());
+        assert!(range::parse("> 0.1.0,").is_err());
+        assert!(range::parse("> 0.3.0, ,").is_err());
+    }
+
+    #[test]
+    pub fn test_large_major_version() {
+        assert!(range::parse("18446744073709551617.0.0").is_err());
+    }
+
+    #[test]
+    pub fn test_large_minor_version() {
+        assert!(range::parse("0.18446744073709551617.0").is_err());
+    }
+
+    #[test]
+    pub fn test_large_patch_version() {
+        assert!(range::parse("0.0.18446744073709551617").is_err());
+    }
+}
diff --git a/semver-parser/src/recognize.rs b/semver-parser/src/recognize.rs
new file mode 100644
index 0000000..c0dd771
--- /dev/null
+++ b/semver-parser/src/recognize.rs
@@ -0,0 +1,154 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// Licensed under either of MIT or Apache License, Version 2.0,
+// at your option.
+//
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Simple recognizer combinators.
+
+// This version is similar to a similar one in the "lang" module of
+// xi-editor, but is stripped down to only the needed combinators.
+
+use std::ops;
+
+pub trait Recognize {
+    fn p(&self, s: &[u8]) -> Option<usize>;
+}
+
+impl<F: Fn(&[u8]) -> Option<usize>> Recognize for F {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        self(s)
+    }
+}
+
+pub struct OneByte<F>(pub F);
+
+impl<F: Fn(u8) -> bool> Recognize for OneByte<F> {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        if s.is_empty() || !self.0(s[0]) {
+            None
+        } else {
+            Some(1)
+        }
+    }
+}
+
+impl Recognize for u8 {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        OneByte(|b| b == *self).p(s)
+    }
+}
+
+/// Use Inclusive(a..b) to indicate an inclusive range. When a...b syntax becomes
+/// stable, we can get rid of this and switch to that.
+pub struct Inclusive<T>(pub T);
+
+impl Recognize for Inclusive<ops::Range<u8>> {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        OneByte(|x| x >= self.0.start && x <= self.0.end).p(s)
+    }
+}
+
+impl<'a> Recognize for &'a [u8] {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        let len = self.len();
+        if s.len() >= len && &s[..len] == *self {
+            Some(len)
+        } else {
+            None
+        }
+    }
+}
+
+impl<'a> Recognize for &'a str {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        self.as_bytes().p(s)
+    }
+}
+
+impl<P1: Recognize, P2: Recognize> Recognize for (P1, P2) {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        self.0.p(s).and_then(|len1|
+            self.1.p(&s[len1..]).map(|len2|
+                len1 + len2))
+    }
+}
+
+/// Choice from two heterogeneous alternatives.
+pub struct Alt<P1, P2>(pub P1, pub P2);
+
+impl<P1: Recognize, P2: Recognize> Recognize for Alt<P1, P2> {
+    #[inline(always)]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        self.0.p(s).or_else(|| self.1.p(s))
+    }
+}
+
+/// Choice from a homogenous slice of parsers.
+pub struct OneOf<'a, P: 'a>(pub &'a [P]);
+
+impl<'a, P: Recognize> Recognize for OneOf<'a, P> {
+    #[inline]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        for ref p in self.0 {
+            if let Some(len) = p.p(s) {
+                return Some(len);
+            }
+        }
+        None
+    }
+}
+
+pub struct OneOrMore<P>(pub P);
+
+impl<P: Recognize> Recognize for OneOrMore<P> {
+    #[inline]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        let mut i = 0;
+        let mut count = 0;
+        while let Some(len) = self.0.p(&s[i..]) {
+            i += len;
+            count += 1;
+        }
+        if count >= 1 {
+            Some(i)
+        } else {
+            None
+        }
+    }
+}
+
+pub struct ZeroOrMore<P>(pub P);
+
+impl<P: Recognize> Recognize for ZeroOrMore<P> {
+    #[inline]
+    fn p(&self, s: &[u8]) -> Option<usize> {
+        let mut i = 0;
+        while let Some(len) = self.0.p(&s[i..]) {
+            i += len;
+        }
+        Some(i)
+    }
+}
diff --git a/semver-parser/src/version.rs b/semver-parser/src/version.rs
new file mode 100644
index 0000000..570f947
--- /dev/null
+++ b/semver-parser/src/version.rs
@@ -0,0 +1,365 @@
+use std::fmt;
+use std::str::from_utf8;
+
+use recognize::*;
+
+use common::{self, numeric_identifier};
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Version {
+    pub major: u64,
+    pub minor: u64,
+    pub patch: u64,
+    pub pre: Vec<Identifier>,
+    pub build: Vec<Identifier>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum Identifier {
+    /// An identifier that's solely numbers.
+    Numeric(u64),
+    /// An identifier with letters and numbers.
+    AlphaNumeric(String),
+}
+
+pub fn parse(version: &str) -> Result<Version, String> {
+    let s = version.trim().as_bytes();
+    let mut i = 0;
+    let major = if let Some((major, len)) = numeric_identifier(&s[i..]) {
+        i += len;
+        major
+    } else {
+        return Err("Error parsing major identifier".to_string());
+    };
+    if let Some(len) = b'.'.p(&s[i..]) {
+        i += len;
+    } else {
+        return Err("Expected dot".to_string());
+    }
+    let minor = if let Some((minor, len)) = numeric_identifier(&s[i..]) {
+        i += len;
+        minor
+    } else {
+        return Err("Error parsing minor identifier".to_string());
+    };
+    if let Some(len) = b'.'.p(&s[i..]) {
+        i += len;
+    } else {
+        return Err("Expected dot".to_string());
+    }
+    let patch = if let Some((patch, len)) = numeric_identifier(&s[i..]) {
+        i += len;
+        patch
+    } else {
+        return Err("Error parsing patch identifier".to_string());
+    };
+    let (pre, pre_len) = common::parse_optional_meta(&s[i..], b'-')?;
+    i += pre_len;
+    let (build, build_len) = common::parse_optional_meta(&s[i..], b'+')?;
+    i += build_len;
+    if i != s.len() {
+        return Err("Extra junk after valid version: ".to_string() +
+            from_utf8(&s[i..]).unwrap());
+    }
+    Ok(Version {
+        major: major,
+        minor: minor,
+        patch: patch,
+        pre: pre,
+        build: build,
+    })
+}
+
+impl fmt::Display for Version {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "{}.{}.{}", self.major, self.minor, self.patch));
+        if !self.pre.is_empty() {
+            let strs: Vec<_> =
+                self.pre.iter().map(ToString::to_string).collect();
+            try!(write!(f, "-{}", strs.join(".")));
+        }
+        if !self.build.is_empty() {
+            let strs: Vec<_> =
+                self.build.iter().map(ToString::to_string).collect();
+            try!(write!(f, "+{}", strs.join(".")));
+        }
+        Ok(())
+    }
+}
+
+impl fmt::Display for Identifier {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Identifier::Numeric(ref id) => id.fmt(f),
+            Identifier::AlphaNumeric(ref id) => id.fmt(f),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use version;
+    use super::*;
+
+    #[test]
+    fn parse_empty() {
+        let version = "";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "empty string incorrectly considered a valid parse");
+    }
+
+    #[test]
+    fn parse_blank() {
+        let version = "  ";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "blank string incorrectly considered a valid parse");
+    }
+
+    #[test]
+    fn parse_no_minor_patch() {
+        let version = "1";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), format!("'{}' incorrectly considered a valid parse", version));
+    }
+
+    #[test]
+    fn parse_no_patch() {
+        let version = "1.2";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), format!("'{}' incorrectly considered a valid parse", version));
+    }
+
+    #[test]
+    fn parse_empty_pre() {
+        let version = "1.2.3-";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), format!("'{}' incorrectly considered a valid parse", version));
+    }
+
+    #[test]
+    fn parse_letters() {
+        let version = "a.b.c";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), format!("'{}' incorrectly considered a valid parse", version));
+    }
+
+    #[test]
+    fn parse_with_letters() {
+        let version = "1.2.3 a.b.c";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), format!("'{}' incorrectly considered a valid parse", version));
+    }
+
+    #[test]
+    fn parse_basic_version() {
+        let version = "1.2.3";
+
+        let parsed = version::parse(version).unwrap();
+
+        assert_eq!(1, parsed.major);
+        assert_eq!(2, parsed.minor);
+        assert_eq!(3, parsed.patch);
+    }
+
+    #[test]
+    fn parse_trims_input() {
+        let version = "  1.2.3  ";
+
+        let parsed = version::parse(version).unwrap();
+
+        assert_eq!(1, parsed.major);
+        assert_eq!(2, parsed.minor);
+        assert_eq!(3, parsed.patch);
+    }
+
+    #[test]
+    fn parse_no_major_leading_zeroes() {
+        let version = "01.0.0";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "01 incorrectly considered a valid major version");
+    }
+
+    #[test]
+    fn parse_no_minor_leading_zeroes() {
+        let version = "0.01.0";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "01 incorrectly considered a valid minor version");
+    }
+
+    #[test]
+    fn parse_no_patch_leading_zeroes() {
+        let version = "0.0.01";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "01 incorrectly considered a valid patch version");
+    }
+
+    #[test]
+    fn parse_no_major_overflow() {
+        let version = "98765432109876543210.0.0";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "98765432109876543210 incorrectly considered a valid major version");
+    }
+
+    #[test]
+    fn parse_no_minor_overflow() {
+        let version = "0.98765432109876543210.0";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "98765432109876543210 incorrectly considered a valid minor version");
+    }
+
+    #[test]
+    fn parse_no_patch_overflow() {
+        let version = "0.0.98765432109876543210";
+
+        let parsed = version::parse(version);
+
+        assert!(parsed.is_err(), "98765432109876543210 incorrectly considered a valid patch version");
+    }
+
+    #[test]
+    fn parse_basic_prerelease() {
+        let version = "1.2.3-pre";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("pre"))];
+        assert_eq!(expected_pre, parsed.pre);
+    }
+
+    #[test]
+    fn parse_prerelease_alphanumeric() {
+        let version = "1.2.3-alpha1";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("alpha1"))];
+        assert_eq!(expected_pre, parsed.pre);
+    }
+
+    #[test]
+    fn parse_prerelease_zero() {
+        let version = "1.2.3-pre.0";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("pre")),
+                                Identifier::Numeric(0)];
+        assert_eq!(expected_pre, parsed.pre);
+    }
+
+    #[test]
+    fn parse_basic_build() {
+        let version = "1.2.3+build";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("build"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_build_alphanumeric() {
+        let version = "1.2.3+build5";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("build5"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_pre_and_build() {
+        let version = "1.2.3-alpha1+build5";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("alpha1"))];
+        assert_eq!(expected_pre, parsed.pre);
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("build5"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_complex_metadata_01() {
+        let version = "1.2.3-1.alpha1.9+build5.7.3aedf  ";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::Numeric(1),
+                                Identifier::AlphaNumeric(String::from("alpha1")),
+                                Identifier::Numeric(9)];
+        assert_eq!(expected_pre, parsed.pre);
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("build5")),
+                                  Identifier::Numeric(7),
+                                  Identifier::AlphaNumeric(String::from("3aedf"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_complex_metadata_02() {
+        let version = "0.4.0-beta.1+0851523";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("beta")),
+                                Identifier::Numeric(1)];
+        assert_eq!(expected_pre, parsed.pre);
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("0851523"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_metadata_overflow() {
+        let version = "0.4.0-beta.1+98765432109876543210";
+
+        let parsed = version::parse(version).unwrap();
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("beta")),
+                                Identifier::Numeric(1)];
+        assert_eq!(expected_pre, parsed.pre);
+
+        let expected_build = vec![Identifier::AlphaNumeric(String::from("98765432109876543210"))];
+        assert_eq!(expected_build, parsed.build);
+    }
+
+    #[test]
+    fn parse_regression_01() {
+        let version = "0.0.0-WIP";
+
+        let parsed = version::parse(version).unwrap();
+
+        assert_eq!(0, parsed.major);
+        assert_eq!(0, parsed.minor);
+        assert_eq!(0, parsed.patch);
+
+        let expected_pre = vec![Identifier::AlphaNumeric(String::from("WIP"))];
+        assert_eq!(expected_pre, parsed.pre);
+    }
+}
diff --git a/semver/.gitignore b/semver/.gitignore
new file mode 100644
index 0000000..cc3b589
--- /dev/null
+++ b/semver/.gitignore
@@ -0,0 +1,3 @@
+target/
+*.sw?
+Cargo.lock
diff --git a/semver/.travis.yml b/semver/.travis.yml
new file mode 100644
index 0000000..bb4ba27
--- /dev/null
+++ b/semver/.travis.yml
@@ -0,0 +1,18 @@
+language: rust
+rust:
+  - nightly
+  - beta
+  - stable
+sudo: false
+script:
+  - cargo build --verbose
+  - cargo test --verbose --features ci
+addons:
+  apt:
+    sources:
+      - kalakris-cmake
+    packages:
+      - cmake
+notifications:
+  email:
+    on_success: never
diff --git a/semver/Cargo.toml b/semver/Cargo.toml
new file mode 100644
index 0000000..1a31f59
--- /dev/null
+++ b/semver/Cargo.toml
@@ -0,0 +1,32 @@
+[package]
+
+name = "semver"
+version = "0.9.0"
+authors = ["Steve Klabnik <steve@steveklabnik.com>", "The Rust Project Developers"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/steveklabnik/semver"
+homepage = "https://docs.rs/crate/semver/"
+documentation = "https://docs.rs/crate/semver/"
+description = """
+Semantic version parsing and comparison.
+"""
+readme = "README.md"
+
+[badges]
+travis-ci = { repository = "steveklabnik/semver" }
+
+[dependencies]
+semver-parser = "0.7.0"
+serde = { version = "1.0", optional = true }
+
+[features]
+default = []
+
+# are we testing on CI?
+ci = ["serde"]
+
+[dev-dependencies]
+crates-index = "0.5.0"
+tempdir = "0.3.4"
+serde_json = "1.0"
+serde_derive = "1.0"
diff --git a/semver/LICENSE-APACHE b/semver/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/semver/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
+   control with that entity. For the purposes of this definition,
+   "control" means (i) the power, direct or indirect, to cause the
+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
+   and conversions to other media types.
+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
+   (an example is provided in the Appendix below).
+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
+   submitted to Licensor for inclusion in the Work by the copyright owner
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+   to the Licensor or its representatives, including but not limited to
+   communication on electronic mailing lists, source code control systems,
+   and issue tracking systems that are managed by, or on behalf of, the
+   Licensor for the purpose of discussing and improving the Work, but
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+   designated in writing by the copyright owner as "Not a Contribution."
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+   "Contributor" shall mean Licensor and any individual or Legal Entity
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+   subsequently incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of
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+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
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+4. Redistribution. You may reproduce and distribute copies of the
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+   meet the following conditions:
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+       Derivative Works a copy of this License; and
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+5. Submission of Contributions. Unless You explicitly state otherwise,
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+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
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+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
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+   appropriateness of using or redistributing the Work and assume any
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+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
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+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
+   or other liability obligations and/or rights consistent with this
+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
+   the brackets!)  The text should be enclosed in the appropriate
+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
+   identification within third-party archives.
+
+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/semver/LICENSE-MIT b/semver/LICENSE-MIT
new file mode 100644
index 0000000..39d4bdb
--- /dev/null
+++ b/semver/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2014 The Rust Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/semver/README.md b/semver/README.md
new file mode 100644
index 0000000..2a5306d
--- /dev/null
+++ b/semver/README.md
@@ -0,0 +1,103 @@
+semver
+======
+
+Semantic version parsing and comparison.
+
+[![Build Status](https://api.travis-ci.org/steveklabnik/semver.svg?branch=master)](https://travis-ci.org/steveklabnik/semver)
+
+[Documentation](https://steveklabnik.github.io/semver)
+
+Semantic versioning (see http://semver.org/) is a set of rules for
+assigning version numbers.
+
+## SemVer and the Rust ecosystem
+
+Rust itself follows the SemVer specification, as does its standard libraries. The two are
+not tied together.
+
+[Cargo](https://crates.io), Rust's package manager, uses SemVer to determine which versions of
+packages you need installed.
+
+## Installation
+
+To use `semver`, add this to your `[dependencies]` section:
+
+```toml
+semver = "0.7.0"
+```
+
+And this to your crate root:
+
+```rust
+extern crate semver;
+```
+
+## Versions
+
+At its simplest, the `semver` crate allows you to construct `Version` objects using the `parse`
+method:
+
+```rust
+use semver::Version;
+
+assert!(Version::parse("1.2.3") == Ok(Version {
+   major: 1,
+   minor: 2,
+   patch: 3,
+   pre: vec!(),
+   build: vec!(),
+}));
+```
+
+If you have multiple `Version`s, you can use the usual comparison operators to compare them:
+
+```rust
+use semver::Version;
+
+assert!(Version::parse("1.2.3-alpha")  != Version::parse("1.2.3-beta"));
+assert!(Version::parse("1.2.3-alpha2") >  Version::parse("1.2.0"));
+```
+
+## Requirements
+
+The `semver` crate also provides the ability to compare requirements, which are more complex
+comparisons.
+
+For example, creating a requirement that only matches versions greater than or
+equal to 1.0.0:
+
+```rust
+use semver::Version;
+use semver::VersionReq;
+
+let r = VersionReq::parse(">= 1.0.0").unwrap();
+let v = Version::parse("1.0.0").unwrap();
+
+assert!(r.to_string() == ">= 1.0.0".to_string());
+assert!(r.matches(&v))
+```
+
+It also allows parsing of `~x.y.z` and `^x.y.z` requirements as defined at
+https://www.npmjs.org/doc/misc/semver.html
+
+**Tilde requirements** specify a minimal version with some updates:
+
+```notrust
+~1.2.3 := >=1.2.3 <1.3.0
+~1.2   := >=1.2.0 <1.3.0
+~1     := >=1.0.0 <2.0.0
+```
+
+**Caret requirements** allow SemVer compatible updates to a specified version,
+`0.x` and `0.x+1` are not considered compatible, but `1.x` and `1.x+1` are.
+
+`0.0.x` is not considered compatible with any other version.
+Missing minor and patch versions are desugared to `0` but allow flexibility for that value.
+
+```notrust
+^1.2.3 := >=1.2.3 <2.0.0
+^0.2.3 := >=0.2.3 <0.3.0
+^0.0.3 := >=0.0.3 <0.0.4
+^0.0   := >=0.0.0 <0.1.0
+^0     := >=0.0.0 <1.0.0
+```
diff --git a/semver/src/lib.rs b/semver/src/lib.rs
new file mode 100644
index 0000000..a38aae0
--- /dev/null
+++ b/semver/src/lib.rs
@@ -0,0 +1,182 @@
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Semantic version parsing and comparison.
+//!
+//! Semantic versioning (see http://semver.org/) is a set of rules for
+//! assigning version numbers.
+//!
+//! ## SemVer overview
+//!
+//! Given a version number MAJOR.MINOR.PATCH, increment the:
+//!
+//! 1. MAJOR version when you make incompatible API changes,
+//! 2. MINOR version when you add functionality in a backwards-compatible
+//!    manner, and
+//! 3. PATCH version when you make backwards-compatible bug fixes.
+//!
+//! Additional labels for pre-release and build metadata are available as
+//! extensions to the MAJOR.MINOR.PATCH format.
+//!
+//! Any references to 'the spec' in this documentation refer to [version 2.0 of
+//! the SemVer spec](http://semver.org/spec/v2.0.0.html).
+//!
+//! ## SemVer and the Rust ecosystem
+//!
+//! Rust itself follows the SemVer specification, as does its standard
+//! libraries. The two are not tied together.
+//!
+//! [Cargo](http://crates.io), Rust's package manager, uses SemVer to determine
+//! which versions of packages you need installed.
+//!
+//! ## Versions
+//!
+//! At its simplest, the `semver` crate allows you to construct `Version`
+//! objects using the `parse` method:
+//!
+//! ```{rust}
+//! use semver::Version;
+//!
+//! assert!(Version::parse("1.2.3") == Ok(Version {
+//!    major: 1,
+//!    minor: 2,
+//!    patch: 3,
+//!    pre: vec!(),
+//!    build: vec!(),
+//! }));
+//! ```
+//!
+//! If you have multiple `Version`s, you can use the usual comparison operators
+//! to compare them:
+//!
+//! ```{rust}
+//! use semver::Version;
+//!
+//! assert!(Version::parse("1.2.3-alpha") != Version::parse("1.2.3-beta"));
+//! assert!(Version::parse("1.2.3-alpha2") >  Version::parse("1.2.0"));
+//! ```
+//!
+//! If you explicitly need to modify a Version, SemVer also allows you to
+//! increment the major, minor, and patch numbers in accordance with the spec.
+//!
+//! Please note that in order to do this, you must use a mutable Version:
+//!
+//! ```{rust}
+//! use semver::Version;
+//!
+//! let mut bugfix_release = Version::parse("1.0.0").unwrap();
+//! bugfix_release.increment_patch();
+//!
+//! assert_eq!(Ok(bugfix_release), Version::parse("1.0.1"));
+//! ```
+//!
+//! When incrementing the minor version number, the patch number resets to zero
+//! (in accordance with section 7 of the spec)
+//!
+//! ```{rust}
+//! use semver::Version;
+//!
+//! let mut feature_release = Version::parse("1.4.6").unwrap();
+//! feature_release.increment_minor();
+//!
+//! assert_eq!(Ok(feature_release), Version::parse("1.5.0"));
+//! ```
+//!
+//! Similarly, when incrementing the major version number, the patch and minor
+//! numbers reset to zero (in accordance with section 8 of the spec)
+//!
+//! ```{rust}
+//! use semver::Version;
+//!
+//! let mut chrome_release = Version::parse("41.5.5377").unwrap();
+//! chrome_release.increment_major();
+//!
+//! assert_eq!(Ok(chrome_release), Version::parse("42.0.0"));
+//! ```
+//!
+//! ## Requirements
+//!
+//! The `semver` crate also provides the ability to compare requirements, which
+//! are more complex comparisons.
+//!
+//! For example, creating a requirement that only matches versions greater than
+//! or equal to 1.0.0:
+//!
+//! ```{rust}
+//! # #![allow(unstable)]
+//! use semver::Version;
+//! use semver::VersionReq;
+//!
+//! let r = VersionReq::parse(">= 1.0.0").unwrap();
+//! let v = Version::parse("1.0.0").unwrap();
+//!
+//! assert!(r.to_string() == ">= 1.0.0".to_string());
+//! assert!(r.matches(&v))
+//! ```
+//!
+//! It also allows parsing of `~x.y.z` and `^x.y.z` requirements as defined at
+//! https://www.npmjs.org/doc/misc/semver.html
+//!
+//! **Tilde requirements** specify a minimal version with some updates:
+//!
+//! ```notrust
+//! ~1.2.3 := >=1.2.3 <1.3.0
+//! ~1.2   := >=1.2.0 <1.3.0
+//! ~1     := >=1.0.0 <2.0.0
+//! ```
+//!
+//! **Caret requirements** allow SemVer compatible updates to a specified
+//! verion, `0.x` and `0.x+1` are not considered compatible, but `1.x` and
+//! `1.x+1` are.
+//!
+//! `0.0.x` is not considered compatible with any other version.
+//! Missing minor and patch versions are desugared to `0` but allow flexibility
+//! for that value.
+//!
+//! ```notrust
+//! ^1.2.3 := >=1.2.3 <2.0.0
+//! ^0.2.3 := >=0.2.3 <0.3.0
+//! ^0.0.3 := >=0.0.3 <0.0.4
+//! ^0.0   := >=0.0.0 <0.1.0
+//! ^0     := >=0.0.0 <1.0.0
+//! ```
+//!
+//! **Wildcard requirements** allows parsing of version requirements of the
+//! formats `*`, `x.*` and `x.y.*`.
+//!
+//! ```notrust
+//! *     := >=0.0.0
+//! 1.*   := >=1.0.0 <2.0.0
+//! 1.2.* := >=1.2.0 <1.3.0
+//! ```
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+       html_favicon_url = "https://www.rust-lang.org/favicon.ico")]
+#![deny(missing_docs)]
+#![cfg_attr(test, deny(warnings))]
+
+extern crate semver_parser;
+
+// Serialization and deserialization support for version numbers
+#[cfg(feature = "serde")]
+extern crate serde;
+
+// We take the common approach of keeping our own module system private, and
+// just re-exporting the interface that we want.
+
+pub use version::{Version, Identifier, SemVerError};
+pub use version::Identifier::{Numeric, AlphaNumeric};
+pub use version_req::{VersionReq, ReqParseError};
+
+// SemVer-compliant versions.
+mod version;
+
+// advanced version comparisons
+mod version_req;
diff --git a/semver/src/version.rs b/semver/src/version.rs
new file mode 100644
index 0000000..38de133
--- /dev/null
+++ b/semver/src/version.rs
@@ -0,0 +1,759 @@
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The `version` module gives you tools to create and compare SemVer-compliant
+//! versions.
+
+use std::cmp::{self, Ordering};
+use std::fmt;
+use std::hash;
+use std::error::Error;
+
+use std::result;
+use std::str;
+
+use semver_parser;
+
+#[cfg(feature = "serde")]
+use serde::ser::{Serialize, Serializer};
+#[cfg(feature = "serde")]
+use serde::de::{self, Deserialize, Deserializer, Visitor};
+
+/// An identifier in the pre-release or build metadata.
+///
+/// See sections 9 and 10 of the spec for more about pre-release identifers and
+/// build metadata.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum Identifier {
+    /// An identifier that's solely numbers.
+    Numeric(u64),
+    /// An identifier with letters and numbers.
+    AlphaNumeric(String),
+}
+
+impl From<semver_parser::version::Identifier> for Identifier {
+    fn from(other: semver_parser::version::Identifier) -> Identifier {
+        match other {
+            semver_parser::version::Identifier::Numeric(n) => Identifier::Numeric(n),
+            semver_parser::version::Identifier::AlphaNumeric(s) => Identifier::AlphaNumeric(s),
+        }
+    }
+}
+
+impl fmt::Display for Identifier {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Identifier::Numeric(ref n) => fmt::Display::fmt(n, f),
+            Identifier::AlphaNumeric(ref s) => fmt::Display::fmt(s, f),
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl Serialize for Identifier {
+    fn serialize<S>(&self, serializer: S) -> result::Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        // Serialize Identifier as a number or string.
+        match *self {
+            Identifier::Numeric(n) => serializer.serialize_u64(n),
+            Identifier::AlphaNumeric(ref s) => serializer.serialize_str(s),
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for Identifier {
+    fn deserialize<D>(deserializer: D) -> result::Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct IdentifierVisitor;
+
+        // Deserialize Identifier from a number or string.
+        impl<'de> Visitor<'de> for IdentifierVisitor {
+            type Value = Identifier;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("a SemVer pre-release or build identifier")
+            }
+
+            fn visit_u64<E>(self, numeric: u64) -> result::Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok(Identifier::Numeric(numeric))
+            }
+
+            fn visit_str<E>(self, alphanumeric: &str) -> result::Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok(Identifier::AlphaNumeric(alphanumeric.to_owned()))
+            }
+        }
+
+        deserializer.deserialize_any(IdentifierVisitor)
+    }
+}
+
+/// Represents a version number conforming to the semantic versioning scheme.
+#[derive(Clone, Eq, Debug)]
+pub struct Version {
+    /// The major version, to be incremented on incompatible changes.
+    pub major: u64,
+    /// The minor version, to be incremented when functionality is added in a
+    /// backwards-compatible manner.
+    pub minor: u64,
+    /// The patch version, to be incremented when backwards-compatible bug
+    /// fixes are made.
+    pub patch: u64,
+    /// The pre-release version identifier, if one exists.
+    pub pre: Vec<Identifier>,
+    /// The build metadata, ignored when determining version precedence.
+    pub build: Vec<Identifier>,
+}
+
+impl From<semver_parser::version::Version> for Version {
+    fn from(other: semver_parser::version::Version) -> Version {
+        Version {
+            major: other.major,
+            minor: other.minor,
+            patch: other.patch,
+            pre: other.pre.into_iter().map(From::from).collect(),
+            build: other.build.into_iter().map(From::from).collect(),
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl Serialize for Version {
+    fn serialize<S>(&self, serializer: S) -> result::Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        // Serialize Version as a string.
+        serializer.collect_str(self)
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for Version {
+    fn deserialize<D>(deserializer: D) -> result::Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct VersionVisitor;
+
+        // Deserialize Version from a string.
+        impl<'de> Visitor<'de> for VersionVisitor {
+            type Value = Version;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("a SemVer version as a string")
+            }
+
+            fn visit_str<E>(self, v: &str) -> result::Result<Self::Value, E>
+                where E: de::Error
+            {
+                Version::parse(v).map_err(de::Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(VersionVisitor)
+    }
+}
+
+/// An error type for this crate
+///
+/// Currently, just a generic error. Will make this nicer later.
+#[derive(Clone,PartialEq,Debug,PartialOrd)]
+pub enum SemVerError {
+    /// An error ocurred while parsing.
+    ParseError(String),
+}
+
+impl fmt::Display for SemVerError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            &SemVerError::ParseError(ref m) => write!(f, "{}", m),
+        }
+    }
+}
+
+impl Error for SemVerError {
+    fn description(&self) -> &str {
+        match self {
+            &SemVerError::ParseError(ref m) => m,
+        }
+    }
+}
+
+/// A Result type for errors
+pub type Result<T> = result::Result<T, SemVerError>;
+
+impl Version {
+
+    /// Contructs the simple case without pre or build.
+    pub fn new(major: u64, minor: u64, patch: u64) -> Version {
+        Version {
+            major: major,
+            minor: minor,
+            patch: patch,
+            pre: Vec::new(),
+            build: Vec::new()
+        }
+    }
+
+    /// Parse a string into a semver object.
+    pub fn parse(version: &str) -> Result<Version> {
+        let res = semver_parser::version::parse(version);
+
+        match res {
+            // Convert plain String error into proper ParseError
+            Err(e) => Err(SemVerError::ParseError(e)),
+            Ok(v) => Ok(From::from(v)),
+        }
+    }
+
+    /// Clears the build metadata
+    fn clear_metadata(&mut self) {
+        self.build = Vec::new();
+        self.pre = Vec::new();
+    }
+
+    /// Increments the patch number for this Version (Must be mutable)
+    pub fn increment_patch(&mut self) {
+        self.patch += 1;
+        self.clear_metadata();
+    }
+
+    /// Increments the minor version number for this Version (Must be mutable)
+    ///
+    /// As instructed by section 7 of the spec, the patch number is reset to 0.
+    pub fn increment_minor(&mut self) {
+        self.minor += 1;
+        self.patch = 0;
+        self.clear_metadata();
+    }
+
+    /// Increments the major version number for this Version (Must be mutable)
+    ///
+    /// As instructed by section 8 of the spec, the minor and patch numbers are
+    /// reset to 0
+    pub fn increment_major(&mut self) {
+        self.major += 1;
+        self.minor = 0;
+        self.patch = 0;
+        self.clear_metadata();
+    }
+
+    /// Checks to see if the current Version is in pre-release status
+    pub fn is_prerelease(&self) -> bool {
+        !self.pre.is_empty()
+    }
+}
+
+impl str::FromStr for Version {
+    type Err = SemVerError;
+
+    fn from_str(s: &str) -> Result<Version> {
+        Version::parse(s)
+    }
+}
+
+impl fmt::Display for Version {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "{}.{}.{}", self.major, self.minor, self.patch));
+        if !self.pre.is_empty() {
+            try!(write!(f, "-"));
+            for (i, x) in self.pre.iter().enumerate() {
+                if i != 0 {
+                    try!(write!(f, "."))
+                }
+                try!(write!(f, "{}", x));
+            }
+        }
+        if !self.build.is_empty() {
+            try!(write!(f, "+"));
+            for (i, x) in self.build.iter().enumerate() {
+                if i != 0 {
+                    try!(write!(f, "."))
+                }
+                try!(write!(f, "{}", x));
+            }
+        }
+        Ok(())
+    }
+}
+
+impl cmp::PartialEq for Version {
+    #[inline]
+    fn eq(&self, other: &Version) -> bool {
+        // We should ignore build metadata here, otherwise versions v1 and v2
+        // can exist such that !(v1 < v2) && !(v1 > v2) && v1 != v2, which
+        // violate strict total ordering rules.
+        self.major == other.major && self.minor == other.minor && self.patch == other.patch &&
+        self.pre == other.pre
+    }
+}
+
+impl cmp::PartialOrd for Version {
+    fn partial_cmp(&self, other: &Version) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl cmp::Ord for Version {
+    fn cmp(&self, other: &Version) -> Ordering {
+        match self.major.cmp(&other.major) {
+            Ordering::Equal => {}
+            r => return r,
+        }
+
+        match self.minor.cmp(&other.minor) {
+            Ordering::Equal => {}
+            r => return r,
+        }
+
+        match self.patch.cmp(&other.patch) {
+            Ordering::Equal => {}
+            r => return r,
+        }
+
+        // NB: semver spec says 0.0.0-pre < 0.0.0
+        // but the version of ord defined for vec
+        // says that [] < [pre] so we alter it here
+        match (self.pre.len(), other.pre.len()) {
+            (0, 0) => Ordering::Equal,
+            (0, _) => Ordering::Greater,
+            (_, 0) => Ordering::Less,
+            (_, _) => self.pre.cmp(&other.pre),
+        }
+    }
+}
+
+impl hash::Hash for Version {
+    fn hash<H: hash::Hasher>(&self, into: &mut H) {
+        self.major.hash(into);
+        self.minor.hash(into);
+        self.patch.hash(into);
+        self.pre.hash(into);
+    }
+}
+
+impl From<(u64,u64,u64)> for Version {
+    fn from(tuple: (u64,u64,u64)) -> Version {
+        let (major, minor, patch) = tuple;
+        Version::new(major, minor, patch)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::result;
+    use super::Version;
+    use super::Identifier;
+    use super::SemVerError;
+
+    #[test]
+    fn test_parse() {
+        fn parse_error(e: &str) -> result::Result<Version, SemVerError> {
+            return Err(SemVerError::ParseError(e.to_string()));
+        }
+
+        assert_eq!(Version::parse(""),
+                   parse_error("Error parsing major identifier"));
+        assert_eq!(Version::parse("  "),
+                   parse_error("Error parsing major identifier"));
+        assert_eq!(Version::parse("1"),
+                   parse_error("Expected dot"));
+        assert_eq!(Version::parse("1.2"),
+                   parse_error("Expected dot"));
+        assert_eq!(Version::parse("1.2.3-"),
+                   parse_error("Error parsing prerelease"));
+        assert_eq!(Version::parse("a.b.c"),
+                   parse_error("Error parsing major identifier"));
+        assert_eq!(Version::parse("1.2.3 abc"),
+                   parse_error("Extra junk after valid version:  abc"));
+
+        assert_eq!(Version::parse("1.2.3"),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: Vec::new(),
+                   }));
+
+        assert_eq!(Version::parse("1.2.3"),
+                   Ok(Version::new(1,2,3)));
+
+        assert_eq!(Version::parse("  1.2.3  "),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: Vec::new(),
+                   }));
+        assert_eq!(Version::parse("1.2.3-alpha1"),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: Vec::new(),
+                   }));
+        assert_eq!(Version::parse("  1.2.3-alpha1  "),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: Vec::new(),
+                   }));
+        assert_eq!(Version::parse("1.2.3+build5"),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!(Version::parse("  1.2.3+build5  "),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!(Version::parse("1.2.3-alpha1+build5"),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!(Version::parse("  1.2.3-alpha1+build5  "),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!(Version::parse("1.2.3-1.alpha1.9+build5.7.3aedf  "),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::Numeric(1),
+                      Identifier::AlphaNumeric(String::from("alpha1")),
+                      Identifier::Numeric(9),
+            ],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5")),
+                        Identifier::Numeric(7),
+                        Identifier::AlphaNumeric(String::from("3aedf")),
+            ],
+                   }));
+        assert_eq!(Version::parse("0.4.0-beta.1+0851523"),
+                   Ok(Version {
+                       major: 0,
+                       minor: 4,
+                       patch: 0,
+                       pre: vec![Identifier::AlphaNumeric(String::from("beta")),
+                      Identifier::Numeric(1),
+            ],
+                       build: vec![Identifier::AlphaNumeric(String::from("0851523"))],
+                   }));
+
+    }
+
+    #[test]
+    fn test_increment_patch() {
+        let mut buggy_release = Version::parse("0.1.0").unwrap();
+        buggy_release.increment_patch();
+        assert_eq!(buggy_release, Version::parse("0.1.1").unwrap());
+    }
+
+    #[test]
+    fn test_increment_minor() {
+        let mut feature_release = Version::parse("1.4.6").unwrap();
+        feature_release.increment_minor();
+        assert_eq!(feature_release, Version::parse("1.5.0").unwrap());
+    }
+
+    #[test]
+    fn test_increment_major() {
+        let mut chrome_release = Version::parse("46.1.246773").unwrap();
+        chrome_release.increment_major();
+        assert_eq!(chrome_release, Version::parse("47.0.0").unwrap());
+    }
+
+    #[test]
+    fn test_increment_keep_prerelease() {
+        let mut release = Version::parse("1.0.0-alpha").unwrap();
+        release.increment_patch();
+
+        assert_eq!(release, Version::parse("1.0.1").unwrap());
+
+        release.increment_minor();
+
+        assert_eq!(release, Version::parse("1.1.0").unwrap());
+
+        release.increment_major();
+
+        assert_eq!(release, Version::parse("2.0.0").unwrap());
+    }
+
+
+    #[test]
+    fn test_increment_clear_metadata() {
+        let mut release = Version::parse("1.0.0+4442").unwrap();
+        release.increment_patch();
+
+        assert_eq!(release, Version::parse("1.0.1").unwrap());
+        release = Version::parse("1.0.1+hello").unwrap();
+
+        release.increment_minor();
+
+        assert_eq!(release, Version::parse("1.1.0").unwrap());
+        release = Version::parse("1.1.3747+hello").unwrap();
+
+        release.increment_major();
+
+        assert_eq!(release, Version::parse("2.0.0").unwrap());
+    }
+
+    #[test]
+    fn test_eq() {
+        assert_eq!(Version::parse("1.2.3"), Version::parse("1.2.3"));
+        assert_eq!(Version::parse("1.2.3-alpha1"),
+                   Version::parse("1.2.3-alpha1"));
+        assert_eq!(Version::parse("1.2.3+build.42"),
+                   Version::parse("1.2.3+build.42"));
+        assert_eq!(Version::parse("1.2.3-alpha1+42"),
+                   Version::parse("1.2.3-alpha1+42"));
+        assert_eq!(Version::parse("1.2.3+23"), Version::parse("1.2.3+42"));
+    }
+
+    #[test]
+    fn test_ne() {
+        assert!(Version::parse("0.0.0") != Version::parse("0.0.1"));
+        assert!(Version::parse("0.0.0") != Version::parse("0.1.0"));
+        assert!(Version::parse("0.0.0") != Version::parse("1.0.0"));
+        assert!(Version::parse("1.2.3-alpha") != Version::parse("1.2.3-beta"));
+    }
+
+    #[test]
+    fn test_show() {
+        assert_eq!(format!("{}", Version::parse("1.2.3").unwrap()),
+                   "1.2.3".to_string());
+        assert_eq!(format!("{}", Version::parse("1.2.3-alpha1").unwrap()),
+                   "1.2.3-alpha1".to_string());
+        assert_eq!(format!("{}", Version::parse("1.2.3+build.42").unwrap()),
+                   "1.2.3+build.42".to_string());
+        assert_eq!(format!("{}", Version::parse("1.2.3-alpha1+42").unwrap()),
+                   "1.2.3-alpha1+42".to_string());
+    }
+
+    #[test]
+    fn test_to_string() {
+        assert_eq!(Version::parse("1.2.3").unwrap().to_string(),
+                   "1.2.3".to_string());
+        assert_eq!(Version::parse("1.2.3-alpha1").unwrap().to_string(),
+                   "1.2.3-alpha1".to_string());
+        assert_eq!(Version::parse("1.2.3+build.42").unwrap().to_string(),
+                   "1.2.3+build.42".to_string());
+        assert_eq!(Version::parse("1.2.3-alpha1+42").unwrap().to_string(),
+                   "1.2.3-alpha1+42".to_string());
+    }
+
+    #[test]
+    fn test_lt() {
+        assert!(Version::parse("0.0.0") < Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.0.0") < Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.0") < Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.3-alpha1") < Version::parse("1.2.3"));
+        assert!(Version::parse("1.2.3-alpha1") < Version::parse("1.2.3-alpha2"));
+        assert!(!(Version::parse("1.2.3-alpha2") < Version::parse("1.2.3-alpha2")));
+        assert!(!(Version::parse("1.2.3+23") < Version::parse("1.2.3+42")));
+    }
+
+    #[test]
+    fn test_le() {
+        assert!(Version::parse("0.0.0") <= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.0.0") <= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.0") <= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.3-alpha1") <= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.3-alpha2") <= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.3+23") <= Version::parse("1.2.3+42"));
+    }
+
+    #[test]
+    fn test_gt() {
+        assert!(Version::parse("1.2.3-alpha2") > Version::parse("0.0.0"));
+        assert!(Version::parse("1.2.3-alpha2") > Version::parse("1.0.0"));
+        assert!(Version::parse("1.2.3-alpha2") > Version::parse("1.2.0"));
+        assert!(Version::parse("1.2.3-alpha2") > Version::parse("1.2.3-alpha1"));
+        assert!(Version::parse("1.2.3") > Version::parse("1.2.3-alpha2"));
+        assert!(!(Version::parse("1.2.3-alpha2") > Version::parse("1.2.3-alpha2")));
+        assert!(!(Version::parse("1.2.3+23") > Version::parse("1.2.3+42")));
+    }
+
+    #[test]
+    fn test_ge() {
+        assert!(Version::parse("1.2.3-alpha2") >= Version::parse("0.0.0"));
+        assert!(Version::parse("1.2.3-alpha2") >= Version::parse("1.0.0"));
+        assert!(Version::parse("1.2.3-alpha2") >= Version::parse("1.2.0"));
+        assert!(Version::parse("1.2.3-alpha2") >= Version::parse("1.2.3-alpha1"));
+        assert!(Version::parse("1.2.3-alpha2") >= Version::parse("1.2.3-alpha2"));
+        assert!(Version::parse("1.2.3+23") >= Version::parse("1.2.3+42"));
+    }
+
+    #[test]
+    fn test_prerelease_check() {
+        assert!(Version::parse("1.0.0").unwrap().is_prerelease() == false);
+        assert!(Version::parse("0.0.1").unwrap().is_prerelease() == false);
+        assert!(Version::parse("4.1.4-alpha").unwrap().is_prerelease());
+        assert!(Version::parse("1.0.0-beta294296").unwrap().is_prerelease());
+    }
+
+    #[test]
+    fn test_spec_order() {
+        let vs = ["1.0.0-alpha",
+                  "1.0.0-alpha.1",
+                  "1.0.0-alpha.beta",
+                  "1.0.0-beta",
+                  "1.0.0-beta.2",
+                  "1.0.0-beta.11",
+                  "1.0.0-rc.1",
+                  "1.0.0"];
+        let mut i = 1;
+        while i < vs.len() {
+            let a = Version::parse(vs[i - 1]);
+            let b = Version::parse(vs[i]);
+            assert!(a < b, "nope {:?} < {:?}", a, b);
+            i += 1;
+        }
+    }
+
+    #[test]
+    fn test_from_str() {
+        assert_eq!("1.2.3".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: Vec::new(),
+                   }));
+        assert_eq!("  1.2.3  ".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: Vec::new(),
+                   }));
+        assert_eq!("1.2.3-alpha1".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: Vec::new(),
+                   }));
+        assert_eq!("  1.2.3-alpha1  ".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: Vec::new(),
+                   }));
+        assert_eq!("1.2.3+build5".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!("  1.2.3+build5  ".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: Vec::new(),
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!("1.2.3-alpha1+build5".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!("  1.2.3-alpha1+build5  ".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::AlphaNumeric(String::from("alpha1"))],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5"))],
+                   }));
+        assert_eq!("1.2.3-1.alpha1.9+build5.7.3aedf  ".parse(),
+                   Ok(Version {
+                       major: 1,
+                       minor: 2,
+                       patch: 3,
+                       pre: vec![Identifier::Numeric(1),
+                      Identifier::AlphaNumeric(String::from("alpha1")),
+                      Identifier::Numeric(9),
+            ],
+                       build: vec![Identifier::AlphaNumeric(String::from("build5")),
+                        Identifier::Numeric(7),
+                        Identifier::AlphaNumeric(String::from("3aedf")),
+            ],
+                   }));
+        assert_eq!("0.4.0-beta.1+0851523".parse(),
+                   Ok(Version {
+                       major: 0,
+                       minor: 4,
+                       patch: 0,
+                       pre: vec![Identifier::AlphaNumeric(String::from("beta")),
+                      Identifier::Numeric(1),
+            ],
+                       build: vec![Identifier::AlphaNumeric(String::from("0851523"))],
+                   }));
+
+    }
+
+    #[test]
+    fn test_from_str_errors() {
+        fn parse_error(e: &str) -> result::Result<Version, SemVerError> {
+            return Err(SemVerError::ParseError(e.to_string()));
+        }
+
+        assert_eq!("".parse(), parse_error("Error parsing major identifier"));
+        assert_eq!("  ".parse(), parse_error("Error parsing major identifier"));
+        assert_eq!("1".parse(), parse_error("Expected dot"));
+        assert_eq!("1.2".parse(),
+                   parse_error("Expected dot"));
+        assert_eq!("1.2.3-".parse(),
+                   parse_error("Error parsing prerelease"));
+        assert_eq!("a.b.c".parse(),
+                   parse_error("Error parsing major identifier"));
+        assert_eq!("1.2.3 abc".parse(),
+                   parse_error("Extra junk after valid version:  abc"));
+    }
+}
diff --git a/semver/src/version_req.rs b/semver/src/version_req.rs
new file mode 100644
index 0000000..6e6a542
--- /dev/null
+++ b/semver/src/version_req.rs
@@ -0,0 +1,895 @@
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::error::Error;
+use std::fmt;
+use std::result;
+use std::str;
+
+use Version;
+use version::Identifier;
+use semver_parser;
+
+#[cfg(feature = "serde")]
+use serde::ser::{Serialize, Serializer};
+#[cfg(feature = "serde")]
+use serde::de::{self, Deserialize, Deserializer, Visitor};
+
+use self::Op::{Ex, Gt, GtEq, Lt, LtEq, Tilde, Compatible, Wildcard};
+use self::WildcardVersion::{Major, Minor, Patch};
+use self::ReqParseError::*;
+
+/// A `VersionReq` is a struct containing a list of predicates that can apply to ranges of version
+/// numbers. Matching operations can then be done with the `VersionReq` against a particular
+/// version to see if it satisfies some or all of the constraints.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct VersionReq {
+    predicates: Vec<Predicate>,
+}
+
+impl From<semver_parser::range::VersionReq> for VersionReq {
+    fn from(other: semver_parser::range::VersionReq) -> VersionReq {
+        VersionReq { predicates: other.predicates.into_iter().map(From::from).collect() }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl Serialize for VersionReq {
+    fn serialize<S>(&self, serializer: S) -> result::Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        // Serialize VersionReq as a string.
+        serializer.collect_str(self)
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for VersionReq {
+    fn deserialize<D>(deserializer: D) -> result::Result<Self, D::Error>
+        where D: Deserializer<'de>
+    {
+        struct VersionReqVisitor;
+
+        /// Deserialize `VersionReq` from a string.
+        impl<'de> Visitor<'de> for VersionReqVisitor {
+            type Value = VersionReq;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("a SemVer version requirement as a string")
+            }
+
+            fn visit_str<E>(self, v: &str) -> result::Result<Self::Value, E>
+                where E: de::Error
+            {
+                VersionReq::parse(v).map_err(de::Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(VersionReqVisitor)
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+enum WildcardVersion {
+    Major,
+    Minor,
+    Patch,
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+enum Op {
+    Ex, // Exact
+    Gt, // Greater than
+    GtEq, // Greater than or equal to
+    Lt, // Less than
+    LtEq, // Less than or equal to
+    Tilde, // e.g. ~1.0.0
+    Compatible, // compatible by definition of semver, indicated by ^
+    Wildcard(WildcardVersion), // x.y.*, x.*, *
+}
+
+impl From<semver_parser::range::Op> for Op {
+    fn from(other: semver_parser::range::Op) -> Op {
+        use semver_parser::range;
+        match other {
+            range::Op::Ex => Op::Ex,
+            range::Op::Gt => Op::Gt,
+            range::Op::GtEq => Op::GtEq,
+            range::Op::Lt => Op::Lt,
+            range::Op::LtEq => Op::LtEq,
+            range::Op::Tilde => Op::Tilde,
+            range::Op::Compatible => Op::Compatible,
+            range::Op::Wildcard(version) => {
+                match version {
+                    range::WildcardVersion::Major => Op::Wildcard(WildcardVersion::Major),
+                    range::WildcardVersion::Minor => Op::Wildcard(WildcardVersion::Minor),
+                    range::WildcardVersion::Patch => Op::Wildcard(WildcardVersion::Patch),
+                }
+            }
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+struct Predicate {
+    op: Op,
+    major: u64,
+    minor: Option<u64>,
+    patch: Option<u64>,
+    pre: Vec<Identifier>,
+}
+
+impl From<semver_parser::range::Predicate> for Predicate {
+    fn from(other: semver_parser::range::Predicate) -> Predicate {
+        Predicate {
+            op: From::from(other.op),
+            major: other.major,
+            minor: other.minor,
+            patch: other.patch,
+            pre: other.pre.into_iter().map(From::from).collect(),
+        }
+    }
+}
+
+/// A `ReqParseError` is returned from methods which parse a string into a `VersionReq`. Each
+/// enumeration is one of the possible errors that can occur.
+#[derive(Clone, Debug, PartialEq)]
+pub enum ReqParseError {
+    /// The given version requirement is invalid.
+    InvalidVersionRequirement,
+    /// You have already provided an operation, such as `=`, `~`, or `^`. Only use one.
+    OpAlreadySet,
+    /// The sigil you have written is not correct.
+    InvalidSigil,
+    /// All components of a version must be numeric.
+    VersionComponentsMustBeNumeric,
+    /// There was an error parsing an identifier.
+    InvalidIdentifier,
+    /// At least a major version is required.
+    MajorVersionRequired,
+    /// An unimplemented version requirement.
+    UnimplementedVersionRequirement,
+    /// This form of requirement is deprecated.
+    DeprecatedVersionRequirement(VersionReq),
+}
+
+impl fmt::Display for ReqParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.description().fmt(f)
+    }
+}
+
+impl Error for ReqParseError {
+    fn description(&self) -> &str {
+        match self {
+            &InvalidVersionRequirement => "the given version requirement is invalid",
+            &OpAlreadySet => {
+                "you have already provided an operation, such as =, ~, or ^; only use one"
+            },
+            &InvalidSigil => "the sigil you have written is not correct",
+            &VersionComponentsMustBeNumeric => "version components must be numeric",
+            &InvalidIdentifier => "invalid identifier",
+            &MajorVersionRequired => "at least a major version number is required",
+            &UnimplementedVersionRequirement => {
+                "the given version requirement is not implemented, yet"
+            },
+            &DeprecatedVersionRequirement(_) => "This requirement is deprecated",
+        }
+    }
+}
+
+impl From<String> for ReqParseError {
+    fn from(other: String) -> ReqParseError {
+        match &*other {
+            "Null is not a valid VersionReq" => ReqParseError::InvalidVersionRequirement,
+            "VersionReq did not parse properly." => ReqParseError::OpAlreadySet,
+            _ => ReqParseError::InvalidVersionRequirement,
+        }
+    }
+}
+
+impl VersionReq {
+    /// `any()` is a factory method which creates a `VersionReq` with no constraints. In other
+    /// words, any version will match against it.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use semver::VersionReq;
+    ///
+    /// let anything = VersionReq::any();
+    /// ```
+    pub fn any() -> VersionReq {
+        VersionReq { predicates: vec![] }
+    }
+
+    /// `parse()` is the main constructor of a `VersionReq`. It takes a string like `"^1.2.3"`
+    /// and turns it into a `VersionReq` that matches that particular constraint.
+    ///
+    /// A `Result` is returned which contains a `ReqParseError` if there was a problem parsing the
+    /// `VersionReq`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use semver::VersionReq;
+    ///
+    /// let version = VersionReq::parse("=1.2.3");
+    /// let version = VersionReq::parse(">1.2.3");
+    /// let version = VersionReq::parse("<1.2.3");
+    /// let version = VersionReq::parse("~1.2.3");
+    /// let version = VersionReq::parse("^1.2.3");
+    /// let version = VersionReq::parse("1.2.3"); // synonym for ^1.2.3
+    /// let version = VersionReq::parse("<=1.2.3");
+    /// let version = VersionReq::parse(">=1.2.3");
+    /// ```
+    ///
+    /// This example demonstrates error handling, and will panic.
+    ///
+    /// ```should-panic
+    /// use semver::VersionReq;
+    ///
+    /// let version = match VersionReq::parse("not a version") {
+    ///     Ok(version) => version,
+    ///     Err(e) => panic!("There was a problem parsing: {}", e),
+    /// }
+    /// ```
+    pub fn parse(input: &str) -> Result<VersionReq, ReqParseError> {
+        let res = semver_parser::range::parse(input);
+
+        if let Ok(v) = res {
+            return Ok(From::from(v));
+        }
+
+        return match VersionReq::parse_deprecated(input) {
+            Some(v) => {
+                Err(ReqParseError::DeprecatedVersionRequirement(v))
+            }
+            None => Err(From::from(res.err().unwrap())),
+        }
+    }
+
+    fn parse_deprecated(version: &str) -> Option<VersionReq> {
+        return match version {
+            ".*" => Some(VersionReq::any()),
+            "0.1.0." => Some(VersionReq::parse("0.1.0").unwrap()),
+            "0.3.1.3" => Some(VersionReq::parse("0.3.13").unwrap()),
+            "0.2*" => Some(VersionReq::parse("0.2.*").unwrap()),
+            "*.0" => Some(VersionReq::any()),
+            _ => None,
+        }
+    }
+
+    /// `exact()` is a factory method which creates a `VersionReq` with one exact constraint.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use semver::VersionReq;
+    /// use semver::Version;
+    ///
+    /// let version = Version { major: 1, minor: 1, patch: 1, pre: vec![], build: vec![] };
+    /// let exact = VersionReq::exact(&version);
+    /// ```
+    pub fn exact(version: &Version) -> VersionReq {
+        VersionReq { predicates: vec![Predicate::exact(version)] }
+    }
+
+    /// `matches()` matches a given `Version` against this `VersionReq`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use semver::VersionReq;
+    /// use semver::Version;
+    ///
+    /// let version = Version { major: 1, minor: 1, patch: 1, pre: vec![], build: vec![] };
+    /// let exact = VersionReq::exact(&version);
+    ///
+    /// assert!(exact.matches(&version));
+    /// ```
+    pub fn matches(&self, version: &Version) -> bool {
+        // no predicates means anything matches
+        if self.predicates.is_empty() {
+            return true;
+        }
+
+        self.predicates.iter().all(|p| p.matches(version)) &&
+        self.predicates.iter().any(|p| p.pre_tag_is_compatible(version))
+    }
+}
+
+impl str::FromStr for VersionReq {
+    type Err = ReqParseError;
+
+    fn from_str(s: &str) -> Result<VersionReq, ReqParseError> {
+        VersionReq::parse(s)
+    }
+}
+
+impl Predicate {
+    fn exact(version: &Version) -> Predicate {
+        Predicate {
+            op: Ex,
+            major: version.major,
+            minor: Some(version.minor),
+            patch: Some(version.patch),
+            pre: version.pre.clone(),
+        }
+    }
+
+    /// `matches()` takes a `Version` and determines if it matches this particular `Predicate`.
+    pub fn matches(&self, ver: &Version) -> bool {
+        match self.op {
+            Ex => self.is_exact(ver),
+            Gt => self.is_greater(ver),
+            GtEq => self.is_exact(ver) || self.is_greater(ver),
+            Lt => !self.is_exact(ver) && !self.is_greater(ver),
+            LtEq => !self.is_greater(ver),
+            Tilde => self.matches_tilde(ver),
+            Compatible => self.is_compatible(ver),
+            Wildcard(_) => self.matches_wildcard(ver),
+        }
+    }
+
+    fn is_exact(&self, ver: &Version) -> bool {
+        if self.major != ver.major {
+            return false;
+        }
+
+        match self.minor {
+            Some(minor) => {
+                if minor != ver.minor {
+                    return false;
+                }
+            }
+            None => return true,
+        }
+
+        match self.patch {
+            Some(patch) => {
+                if patch != ver.patch {
+                    return false;
+                }
+            }
+            None => return true,
+        }
+
+        if self.pre != ver.pre {
+            return false;
+        }
+
+        true
+    }
+
+    // https://docs.npmjs.com/misc/semver#prerelease-tags
+    fn pre_tag_is_compatible(&self, ver: &Version) -> bool {
+        // If a version has a prerelease tag (for example, 1.2.3-alpha.3) then it will
+        // only be
+        // allowed to satisfy comparator sets if at least one comparator with the same
+        // [major,
+        // minor, patch] tuple also has a prerelease tag.
+        !ver.is_prerelease() ||
+        (self.major == ver.major && self.minor == Some(ver.minor) &&
+         self.patch == Some(ver.patch) && !self.pre.is_empty())
+    }
+
+    fn is_greater(&self, ver: &Version) -> bool {
+        if self.major != ver.major {
+            return ver.major > self.major;
+        }
+
+        match self.minor {
+            Some(minor) => {
+                if minor != ver.minor {
+                    return ver.minor > minor;
+                }
+            }
+            None => return false,
+        }
+
+        match self.patch {
+            Some(patch) => {
+                if patch != ver.patch {
+                    return ver.patch > patch;
+                }
+            }
+            None => return false,
+        }
+
+        if !self.pre.is_empty() {
+            return ver.pre.is_empty() || ver.pre > self.pre;
+        }
+
+        false
+    }
+
+    // see https://www.npmjs.org/doc/misc/semver.html for behavior
+    fn matches_tilde(&self, ver: &Version) -> bool {
+        let minor = match self.minor {
+            Some(n) => n,
+            None => return self.major == ver.major,
+        };
+
+        match self.patch {
+            Some(patch) => {
+                self.major == ver.major && minor == ver.minor &&
+                (ver.patch > patch || (ver.patch == patch && self.pre_is_compatible(ver)))
+            }
+            None => self.major == ver.major && minor == ver.minor,
+        }
+    }
+
+    // see https://www.npmjs.org/doc/misc/semver.html for behavior
+    fn is_compatible(&self, ver: &Version) -> bool {
+        if self.major != ver.major {
+            return false;
+        }
+
+        let minor = match self.minor {
+            Some(n) => n,
+            None => return self.major == ver.major,
+        };
+
+        match self.patch {
+            Some(patch) => {
+                if self.major == 0 {
+                    if minor == 0 {
+                        ver.minor == minor && ver.patch == patch && self.pre_is_compatible(ver)
+                    } else {
+                        ver.minor == minor &&
+                        (ver.patch > patch || (ver.patch == patch && self.pre_is_compatible(ver)))
+                    }
+                } else {
+                    ver.minor > minor ||
+                    (ver.minor == minor &&
+                     (ver.patch > patch || (ver.patch == patch && self.pre_is_compatible(ver))))
+                }
+            }
+            None => {
+                if self.major == 0 {
+                    ver.minor == minor
+                } else {
+                    ver.minor >= minor
+                }
+            }
+        }
+    }
+
+    fn pre_is_compatible(&self, ver: &Version) -> bool {
+        ver.pre.is_empty() || ver.pre >= self.pre
+    }
+
+    // see https://www.npmjs.org/doc/misc/semver.html for behavior
+    fn matches_wildcard(&self, ver: &Version) -> bool {
+        match self.op {
+            Wildcard(Major) => true,
+            Wildcard(Minor) => self.major == ver.major,
+            Wildcard(Patch) => {
+                match self.minor {
+                    Some(minor) => self.major == ver.major && minor == ver.minor,
+                    None => {
+                        // minor and patch version astericks mean match on major
+                        self.major == ver.major
+                    }
+                }
+            }
+            _ => false,  // unreachable
+        }
+    }
+}
+
+impl fmt::Display for VersionReq {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        if self.predicates.is_empty() {
+            try!(write!(fmt, "*"));
+        } else {
+            for (i, ref pred) in self.predicates.iter().enumerate() {
+                if i == 0 {
+                    try!(write!(fmt, "{}", pred));
+                } else {
+                    try!(write!(fmt, ", {}", pred));
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl fmt::Display for Predicate {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self.op {
+            Wildcard(Major) => try!(write!(fmt, "*")),
+            Wildcard(Minor) => try!(write!(fmt, "{}.*", self.major)),
+            Wildcard(Patch) => {
+                if let Some(minor) = self.minor {
+                    try!(write!(fmt, "{}.{}.*", self.major, minor))
+                } else {
+                    try!(write!(fmt, "{}.*.*", self.major))
+                }
+            }
+            _ => {
+                try!(write!(fmt, "{}{}", self.op, self.major));
+
+                match self.minor {
+                    Some(v) => try!(write!(fmt, ".{}", v)),
+                    None => (),
+                }
+
+                match self.patch {
+                    Some(v) => try!(write!(fmt, ".{}", v)),
+                    None => (),
+                }
+
+                if !self.pre.is_empty() {
+                    try!(write!(fmt, "-"));
+                    for (i, x) in self.pre.iter().enumerate() {
+                        if i != 0 {
+                            try!(write!(fmt, "."))
+                        }
+                        try!(write!(fmt, "{}", x));
+                    }
+                }
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl fmt::Display for Op {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Ex => try!(write!(fmt, "= ")),
+            Gt => try!(write!(fmt, "> ")),
+            GtEq => try!(write!(fmt, ">= ")),
+            Lt => try!(write!(fmt, "< ")),
+            LtEq => try!(write!(fmt, "<= ")),
+            Tilde => try!(write!(fmt, "~")),
+            Compatible => try!(write!(fmt, "^")),
+            // gets handled specially in Predicate::fmt
+            Wildcard(_) => try!(write!(fmt, "")),
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::{VersionReq, Op};
+    use super::super::version::Version;
+    use std::hash::{Hash, Hasher};
+
+    fn req(s: &str) -> VersionReq {
+        VersionReq::parse(s).unwrap()
+    }
+
+    fn version(s: &str) -> Version {
+        match Version::parse(s) {
+            Ok(v) => v,
+            Err(e) => panic!("`{}` is not a valid version. Reason: {:?}", s, e),
+        }
+    }
+
+    fn assert_match(req: &VersionReq, vers: &[&str]) {
+        for ver in vers.iter() {
+            assert!(req.matches(&version(*ver)), "did not match {}", ver);
+        }
+    }
+
+    fn assert_not_match(req: &VersionReq, vers: &[&str]) {
+        for ver in vers.iter() {
+            assert!(!req.matches(&version(*ver)), "matched {}", ver);
+        }
+    }
+
+    fn calculate_hash<T: Hash>(t: T) -> u64 {
+        use std::collections::hash_map::DefaultHasher;
+
+        let mut s = DefaultHasher::new();
+        t.hash(&mut s);
+        s.finish()
+    }
+
+    #[test]
+    fn test_parsing_default() {
+        let r = req("1.0.0");
+
+        assert_eq!(r.to_string(), "^1.0.0".to_string());
+
+        assert_match(&r, &["1.0.0", "1.0.1"]);
+        assert_not_match(&r, &["0.9.9", "0.10.0", "0.1.0"]);
+    }
+
+    #[test]
+    fn test_parsing_exact() {
+        let r = req("=1.0.0");
+
+        assert!(r.to_string() == "= 1.0.0".to_string());
+        assert_eq!(r.to_string(), "= 1.0.0".to_string());
+
+        assert_match(&r, &["1.0.0"]);
+        assert_not_match(&r, &["1.0.1", "0.9.9", "0.10.0", "0.1.0", "1.0.0-pre"]);
+
+        let r = req("=0.9.0");
+
+        assert_eq!(r.to_string(), "= 0.9.0".to_string());
+
+        assert_match(&r, &["0.9.0"]);
+        assert_not_match(&r, &["0.9.1", "1.9.0", "0.0.9"]);
+
+        let r = req("=0.1.0-beta2.a");
+
+        assert_eq!(r.to_string(), "= 0.1.0-beta2.a".to_string());
+
+        assert_match(&r, &["0.1.0-beta2.a"]);
+        assert_not_match(&r, &["0.9.1", "0.1.0", "0.1.1-beta2.a", "0.1.0-beta2"]);
+    }
+
+    #[test]
+    fn test_parse_metadata_see_issue_88_see_issue_88() {
+        for op in &[Op::Compatible, Op::Ex, Op::Gt, Op::GtEq, Op::Lt, Op::LtEq, Op::Tilde] {
+            req(&format!("{} 1.2.3+meta", op));
+        }
+    }
+
+    #[test]
+    pub fn test_parsing_greater_than() {
+        let r = req(">= 1.0.0");
+
+        assert_eq!(r.to_string(), ">= 1.0.0".to_string());
+
+        assert_match(&r, &["1.0.0", "2.0.0"]);
+        assert_not_match(&r, &["0.1.0", "0.0.1", "1.0.0-pre", "2.0.0-pre"]);
+
+        let r = req(">= 2.1.0-alpha2");
+
+        assert_match(&r, &["2.1.0-alpha2", "2.1.0-alpha3", "2.1.0", "3.0.0"]);
+        assert_not_match(&r,
+                         &["2.0.0", "2.1.0-alpha1", "2.0.0-alpha2", "3.0.0-alpha2"]);
+    }
+
+    #[test]
+    pub fn test_parsing_less_than() {
+        let r = req("< 1.0.0");
+
+        assert_eq!(r.to_string(), "< 1.0.0".to_string());
+
+        assert_match(&r, &["0.1.0", "0.0.1"]);
+        assert_not_match(&r, &["1.0.0", "1.0.0-beta", "1.0.1", "0.9.9-alpha"]);
+
+        let r = req("<= 2.1.0-alpha2");
+
+        assert_match(&r, &["2.1.0-alpha2", "2.1.0-alpha1", "2.0.0", "1.0.0"]);
+        assert_not_match(&r,
+                         &["2.1.0", "2.2.0-alpha1", "2.0.0-alpha2", "1.0.0-alpha2"]);
+    }
+
+    #[test]
+    pub fn test_multiple() {
+        let r = req("> 0.0.9, <= 2.5.3");
+        assert_eq!(r.to_string(), "> 0.0.9, <= 2.5.3".to_string());
+        assert_match(&r, &["0.0.10", "1.0.0", "2.5.3"]);
+        assert_not_match(&r, &["0.0.8", "2.5.4"]);
+
+        let r = req("0.3.0, 0.4.0");
+        assert_eq!(r.to_string(), "^0.3.0, ^0.4.0".to_string());
+        assert_not_match(&r, &["0.0.8", "0.3.0", "0.4.0"]);
+
+        let r = req("<= 0.2.0, >= 0.5.0");
+        assert_eq!(r.to_string(), "<= 0.2.0, >= 0.5.0".to_string());
+        assert_not_match(&r, &["0.0.8", "0.3.0", "0.5.1"]);
+
+        let r = req("0.1.0, 0.1.4, 0.1.6");
+        assert_eq!(r.to_string(), "^0.1.0, ^0.1.4, ^0.1.6".to_string());
+        assert_match(&r, &["0.1.6", "0.1.9"]);
+        assert_not_match(&r, &["0.1.0", "0.1.4", "0.2.0"]);
+
+        assert!(VersionReq::parse("> 0.1.0,").is_err());
+        assert!(VersionReq::parse("> 0.3.0, ,").is_err());
+
+        let r = req(">=0.5.1-alpha3, <0.6");
+        assert_eq!(r.to_string(), ">= 0.5.1-alpha3, < 0.6".to_string());
+        assert_match(&r,
+                     &["0.5.1-alpha3", "0.5.1-alpha4", "0.5.1-beta", "0.5.1", "0.5.5"]);
+        assert_not_match(&r,
+                         &["0.5.1-alpha1", "0.5.2-alpha3", "0.5.5-pre", "0.5.0-pre"]);
+        assert_not_match(&r, &["0.6.0", "0.6.0-pre"]);
+    }
+
+    #[test]
+    pub fn test_parsing_tilde() {
+        let r = req("~1");
+        assert_match(&r, &["1.0.0", "1.0.1", "1.1.1"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "0.0.9"]);
+
+        let r = req("~1.2");
+        assert_match(&r, &["1.2.0", "1.2.1"]);
+        assert_not_match(&r, &["1.1.1", "1.3.0", "0.0.9"]);
+
+        let r = req("~1.2.2");
+        assert_match(&r, &["1.2.2", "1.2.4"]);
+        assert_not_match(&r, &["1.2.1", "1.9.0", "1.0.9", "2.0.1", "0.1.3"]);
+
+        let r = req("~1.2.3-beta.2");
+        assert_match(&r, &["1.2.3", "1.2.4", "1.2.3-beta.2", "1.2.3-beta.4"]);
+        assert_not_match(&r, &["1.3.3", "1.1.4", "1.2.3-beta.1", "1.2.4-beta.2"]);
+    }
+
+    #[test]
+    pub fn test_parsing_compatible() {
+        let r = req("^1");
+        assert_match(&r, &["1.1.2", "1.1.0", "1.2.1", "1.0.1"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "0.1.4"]);
+        assert_not_match(&r, &["1.0.0-beta1", "0.1.0-alpha", "1.0.1-pre"]);
+
+        let r = req("^1.1");
+        assert_match(&r, &["1.1.2", "1.1.0", "1.2.1"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "1.0.1", "0.1.4"]);
+
+        let r = req("^1.1.2");
+        assert_match(&r, &["1.1.2", "1.1.4", "1.2.1"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "1.1.1", "0.0.1"]);
+        assert_not_match(&r, &["1.1.2-alpha1", "1.1.3-alpha1", "2.9.0-alpha1"]);
+
+        let r = req("^0.1.2");
+        assert_match(&r, &["0.1.2", "0.1.4"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "1.1.1", "0.0.1"]);
+        assert_not_match(&r, &["0.1.2-beta", "0.1.3-alpha", "0.2.0-pre"]);
+
+        let r = req("^0.5.1-alpha3");
+        assert_match(&r,
+                     &["0.5.1-alpha3", "0.5.1-alpha4", "0.5.1-beta", "0.5.1", "0.5.5"]);
+        assert_not_match(&r,
+                         &["0.5.1-alpha1", "0.5.2-alpha3", "0.5.5-pre", "0.5.0-pre", "0.6.0"]);
+
+        let r = req("^0.0.2");
+        assert_match(&r, &["0.0.2"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "1.1.1", "0.0.1", "0.1.4"]);
+
+        let r = req("^0.0");
+        assert_match(&r, &["0.0.2", "0.0.0"]);
+        assert_not_match(&r, &["0.9.1", "2.9.0", "1.1.1", "0.1.4"]);
+
+        let r = req("^0");
+        assert_match(&r, &["0.9.1", "0.0.2", "0.0.0"]);
+        assert_not_match(&r, &["2.9.0", "1.1.1"]);
+
+        let r = req("^1.4.2-beta.5");
+        assert_match(&r,
+                     &["1.4.2", "1.4.3", "1.4.2-beta.5", "1.4.2-beta.6", "1.4.2-c"]);
+        assert_not_match(&r,
+                         &["0.9.9", "2.0.0", "1.4.2-alpha", "1.4.2-beta.4", "1.4.3-beta.5"]);
+    }
+
+    #[test]
+    pub fn test_parsing_wildcard() {
+        let r = req("");
+        assert_match(&r, &["0.9.1", "2.9.0", "0.0.9", "1.0.1", "1.1.1"]);
+        assert_not_match(&r, &[]);
+        let r = req("*");
+        assert_match(&r, &["0.9.1", "2.9.0", "0.0.9", "1.0.1", "1.1.1"]);
+        assert_not_match(&r, &[]);
+        let r = req("x");
+        assert_match(&r, &["0.9.1", "2.9.0", "0.0.9", "1.0.1", "1.1.1"]);
+        assert_not_match(&r, &[]);
+        let r = req("X");
+        assert_match(&r, &["0.9.1", "2.9.0", "0.0.9", "1.0.1", "1.1.1"]);
+        assert_not_match(&r, &[]);
+
+        let r = req("1.*");
+        assert_match(&r, &["1.2.0", "1.2.1", "1.1.1", "1.3.0"]);
+        assert_not_match(&r, &["0.0.9"]);
+        let r = req("1.x");
+        assert_match(&r, &["1.2.0", "1.2.1", "1.1.1", "1.3.0"]);
+        assert_not_match(&r, &["0.0.9"]);
+        let r = req("1.X");
+        assert_match(&r, &["1.2.0", "1.2.1", "1.1.1", "1.3.0"]);
+        assert_not_match(&r, &["0.0.9"]);
+
+        let r = req("1.2.*");
+        assert_match(&r, &["1.2.0", "1.2.2", "1.2.4"]);
+        assert_not_match(&r, &["1.9.0", "1.0.9", "2.0.1", "0.1.3"]);
+        let r = req("1.2.x");
+        assert_match(&r, &["1.2.0", "1.2.2", "1.2.4"]);
+        assert_not_match(&r, &["1.9.0", "1.0.9", "2.0.1", "0.1.3"]);
+        let r = req("1.2.X");
+        assert_match(&r, &["1.2.0", "1.2.2", "1.2.4"]);
+        assert_not_match(&r, &["1.9.0", "1.0.9", "2.0.1", "0.1.3"]);
+    }
+
+    #[test]
+    pub fn test_any() {
+        let r = VersionReq::any();
+        assert_match(&r, &["0.0.1", "0.1.0", "1.0.0"]);
+    }
+
+    #[test]
+    pub fn test_pre() {
+        let r = req("=2.1.1-really.0");
+        assert_match(&r, &["2.1.1-really.0"]);
+    }
+
+    // #[test]
+    // pub fn test_parse_errors() {
+    //    assert_eq!(Err(InvalidVersionRequirement), VersionReq::parse("\0"));
+    //    assert_eq!(Err(OpAlreadySet), VersionReq::parse(">= >= 0.0.2"));
+    //    assert_eq!(Err(InvalidSigil), VersionReq::parse(">== 0.0.2"));
+    //    assert_eq!(Err(VersionComponentsMustBeNumeric),
+    //               VersionReq::parse("a.0.0"));
+    //    assert_eq!(Err(InvalidIdentifier), VersionReq::parse("1.0.0-"));
+    //    assert_eq!(Err(MajorVersionRequired), VersionReq::parse(">="));
+    // }
+
+    #[test]
+    pub fn test_from_str() {
+        assert_eq!("1.0.0".parse::<VersionReq>().unwrap().to_string(),
+                   "^1.0.0".to_string());
+        assert_eq!("=1.0.0".parse::<VersionReq>().unwrap().to_string(),
+                   "= 1.0.0".to_string());
+        assert_eq!("~1".parse::<VersionReq>().unwrap().to_string(),
+                   "~1".to_string());
+        assert_eq!("~1.2".parse::<VersionReq>().unwrap().to_string(),
+                   "~1.2".to_string());
+        assert_eq!("^1".parse::<VersionReq>().unwrap().to_string(),
+                   "^1".to_string());
+        assert_eq!("^1.1".parse::<VersionReq>().unwrap().to_string(),
+                   "^1.1".to_string());
+        assert_eq!("*".parse::<VersionReq>().unwrap().to_string(),
+                   "*".to_string());
+        assert_eq!("1.*".parse::<VersionReq>().unwrap().to_string(),
+                   "1.*".to_string());
+        assert_eq!("< 1.0.0".parse::<VersionReq>().unwrap().to_string(),
+                   "< 1.0.0".to_string());
+    }
+
+    // #[test]
+    // pub fn test_from_str_errors() {
+    //    assert_eq!(Err(InvalidVersionRequirement), "\0".parse::<VersionReq>());
+    //    assert_eq!(Err(OpAlreadySet), ">= >= 0.0.2".parse::<VersionReq>());
+    //    assert_eq!(Err(InvalidSigil), ">== 0.0.2".parse::<VersionReq>());
+    //    assert_eq!(Err(VersionComponentsMustBeNumeric),
+    //               "a.0.0".parse::<VersionReq>());
+    //    assert_eq!(Err(InvalidIdentifier), "1.0.0-".parse::<VersionReq>());
+    //    assert_eq!(Err(MajorVersionRequired), ">=".parse::<VersionReq>());
+    // }
+
+    #[test]
+    fn test_cargo3202() {
+        let v = "0.*.*".parse::<VersionReq>().unwrap();
+        assert_eq!("0.*.*", format!("{}", v.predicates[0]));
+
+        let v = "0.0.*".parse::<VersionReq>().unwrap();
+        assert_eq!("0.0.*", format!("{}", v.predicates[0]));
+
+        let r = req("0.*.*");
+        assert_match(&r, &["0.5.0"]);
+    }
+
+    #[test]
+    fn test_eq_hash() {
+        assert!(req("^1") == req("^1"));
+        assert!(calculate_hash(req("^1")) == calculate_hash(req("^1")));
+        assert!(req("^1") != req("^2"));
+    }
+
+    #[test]
+    fn test_ordering() {
+        assert!(req("=1") < req("*"));
+        assert!(req(">1") < req("*"));
+        assert!(req(">=1") < req("*"));
+        assert!(req("<1") < req("*"));
+        assert!(req("<=1") < req("*"));
+        assert!(req("~1") < req("*"));
+        assert!(req("^1") < req("*"));
+        assert!(req("*") == req("*"));
+    }
+}
diff --git a/semver/tests/deprecation.rs b/semver/tests/deprecation.rs
new file mode 100644
index 0000000..a5f533a
--- /dev/null
+++ b/semver/tests/deprecation.rs
@@ -0,0 +1,22 @@
+extern crate semver;
+
+#[test]
+fn test_regressions() {
+    use semver::VersionReq;
+    use semver::ReqParseError;
+
+    let versions = vec![
+        (".*", VersionReq::any()),
+        ("0.1.0.", VersionReq::parse("0.1.0").unwrap()),
+        ("0.3.1.3", VersionReq::parse("0.3.13").unwrap()),
+        ("0.2*", VersionReq::parse("0.2.*").unwrap()),
+        ("*.0", VersionReq::any()),
+    ];
+
+    for (version, requirement) in versions.into_iter() {
+        let parsed = VersionReq::parse(version);
+        let error = parsed.err().unwrap();
+
+        assert_eq!(ReqParseError::DeprecatedVersionRequirement(requirement), error);
+    }
+}
diff --git a/semver/tests/regression.rs b/semver/tests/regression.rs
new file mode 100644
index 0000000..ef568a7
--- /dev/null
+++ b/semver/tests/regression.rs
@@ -0,0 +1,25 @@
+extern crate semver;
+extern crate crates_index;
+extern crate tempdir;
+
+// This test checks to see if every existing crate parses successfully. Important to not break the
+// Rust universe!
+
+#[cfg(feature = "ci")]
+#[test]
+fn test_regressions() {
+    use tempdir::TempDir;
+    use crates_index::Index;
+    use semver::Version;
+
+    let dir = TempDir::new("semver").unwrap();
+    let index = Index::new(dir.into_path());
+    index.clone().unwrap();
+
+    for krate in index.crates() {
+        for version in krate.versions() {
+            let v = version.version();
+            assert!(Version::parse(v).is_ok(), "failed: {} ({})", version.name(), v);
+        }
+    }
+}
diff --git a/semver/tests/serde.rs b/semver/tests/serde.rs
new file mode 100644
index 0000000..bcb9264
--- /dev/null
+++ b/semver/tests/serde.rs
@@ -0,0 +1,90 @@
+#![cfg(feature = "serde")]
+
+#[macro_use]
+extern crate serde_derive;
+
+extern crate semver;
+extern crate serde_json;
+
+use semver::{Identifier, Version, VersionReq};
+
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+struct Identified {
+    name: String,
+    identifier: Identifier,
+}
+
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+struct Versioned {
+    name: String,
+    vers: Version,
+}
+
+#[test]
+fn serialize_identifier() {
+    let id = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::Numeric(100),
+    };
+    let j = serde_json::to_string(&id).unwrap();
+    assert_eq!(j, r#"{"name":"serde","identifier":100}"#);
+
+    let id = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::AlphaNumeric("b100".to_owned()),
+    };
+    let j = serde_json::to_string(&id).unwrap();
+    assert_eq!(j, r#"{"name":"serde","identifier":"b100"}"#);
+}
+
+#[test]
+fn deserialize_identifier() {
+    let j = r#"{"name":"serde","identifier":100}"#;
+    let id = serde_json::from_str::<Identified>(j).unwrap();
+    let expected = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::Numeric(100),
+    };
+    assert_eq!(id, expected);
+
+    let j = r#"{"name":"serde","identifier":"b100"}"#;
+    let id = serde_json::from_str::<Identified>(j).unwrap();
+    let expected = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::AlphaNumeric("b100".to_owned()),
+    };
+    assert_eq!(id, expected);
+}
+
+#[test]
+fn serialize_version() {
+    let v = Versioned {
+        name: "serde".to_owned(),
+        vers: Version::parse("1.0.0").unwrap(),
+    };
+    let j = serde_json::to_string(&v).unwrap();
+    assert_eq!(j, r#"{"name":"serde","vers":"1.0.0"}"#);
+}
+
+#[test]
+fn deserialize_version() {
+    let j = r#"{"name":"serde","vers":"1.0.0"}"#;
+    let v = serde_json::from_str::<Versioned>(j).unwrap();
+    let expected = Versioned {
+        name: "serde".to_owned(),
+        vers: Version::parse("1.0.0").unwrap(),
+    };
+    assert_eq!(v, expected);
+}
+
+#[test]
+fn serialize_versionreq() {
+    let v = VersionReq::exact(&Version::parse("1.0.0").unwrap());
+
+    assert_eq!(serde_json::to_string(&v).unwrap(), r#""= 1.0.0""#);
+}
+
+#[test]
+fn deserialize_versionreq() {
+    assert_eq!("1.0.0".parse::<VersionReq>().unwrap(), serde_json::from_str(r#""1.0.0""#).unwrap());
+}
author	Daniel Mueller <deso@posteo.net>	2019-01-02 21:14:10 -0800
committer	Daniel Mueller <deso@posteo.net>	2019-01-02 21:14:10 -0800
commit	ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb (patch)
tree	03134a683791176b49ef5c92e8d6acd24c3b5a9b
parent	686f61b75055ecb02baf9d9449525ae447a3bed1 (diff)
download	nitrocli-ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb.tar.gz nitrocli-ecf3474223ca3d16a10f12dc2272e3b0ed72c1bb.tar.bz2