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Diffstat (limited to 'rand/rand_core')
| -rw-r--r-- | rand/rand_core/CHANGELOG.md | 33 | ||||
| -rw-r--r-- | rand/rand_core/COPYRIGHT | 12 | ||||
| -rw-r--r-- | rand/rand_core/Cargo.toml | 28 | ||||
| -rw-r--r-- | rand/rand_core/LICENSE-APACHE | 201 | ||||
| -rw-r--r-- | rand/rand_core/LICENSE-MIT | 26 | ||||
| -rw-r--r-- | rand/rand_core/README.md | 65 | ||||
| -rw-r--r-- | rand/rand_core/src/block.rs | 508 | ||||
| -rw-r--r-- | rand/rand_core/src/error.rs | 177 | ||||
| -rw-r--r-- | rand/rand_core/src/impls.rs | 165 | ||||
| -rw-r--r-- | rand/rand_core/src/le.rs | 68 | ||||
| -rw-r--r-- | rand/rand_core/src/lib.rs | 486 |
11 files changed, 1769 insertions, 0 deletions
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 + Version 2.0, January 2004 + https://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. 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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_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 + +[](https://travis-ci.org/rust-random/rand) +[](https://ci.appveyor.com/project/rust-random/rand) +[](https://crates.io/crates/rand_core) +[](https://rust-random.github.io/book/) +[](https://rust-random.github.io/rand/rand_core) +[](https://docs.rs/rand_core) +[](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); + } +} |