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-rw-r--r--lazy-static/src/core_lazy.rs31
-rw-r--r--lazy-static/src/inline_lazy.rs65
-rw-r--r--lazy-static/src/lib.rs212
3 files changed, 308 insertions, 0 deletions
diff --git a/lazy-static/src/core_lazy.rs b/lazy-static/src/core_lazy.rs
new file mode 100644
index 0000000..b66c3e0
--- /dev/null
+++ b/lazy-static/src/core_lazy.rs
@@ -0,0 +1,31 @@
+// Copyright 2016 lazy-static.rs Developers
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://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.
+
+extern crate spin;
+
+use self::spin::Once;
+
+pub struct Lazy<T: Sync>(Once<T>);
+
+impl<T: Sync> Lazy<T> {
+ pub const INIT: Self = Lazy(Once::INIT);
+
+ #[inline(always)]
+ pub fn get<F>(&'static self, builder: F) -> &T
+ where F: FnOnce() -> T
+ {
+ self.0.call_once(builder)
+ }
+}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __lazy_static_create {
+ ($NAME:ident, $T:ty) => {
+ static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::INIT;
+ }
+}
diff --git a/lazy-static/src/inline_lazy.rs b/lazy-static/src/inline_lazy.rs
new file mode 100644
index 0000000..268dd45
--- /dev/null
+++ b/lazy-static/src/inline_lazy.rs
@@ -0,0 +1,65 @@
+// Copyright 2016 lazy-static.rs Developers
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+extern crate core;
+extern crate std;
+
+use self::std::prelude::v1::*;
+use self::std::cell::Cell;
+use self::std::sync::Once;
+pub use self::std::sync::ONCE_INIT;
+
+// FIXME: Replace Option<T> with MaybeInitialized<T>
+pub struct Lazy<T: Sync>(Cell<Option<T>>, Once);
+
+impl<T: Sync> Lazy<T> {
+ pub const INIT: Self = Lazy(Cell::new(None), ONCE_INIT);
+
+ #[inline(always)]
+ pub fn get<F>(&'static self, f: F) -> &T
+ where
+ F: FnOnce() -> T,
+ {
+ self.1.call_once(|| {
+ self.0.set(Some(f()));
+ });
+
+ // `self.0` is guaranteed to be `Some` by this point
+ // The `Once` will catch and propegate panics
+ unsafe {
+ match *self.0.as_ptr() {
+ Some(ref x) => x,
+ None => {
+ debug_assert!(false, "attempted to derefence an uninitialized lazy static. This is a bug");
+
+ unreachable_unchecked()
+ },
+ }
+ }
+ }
+}
+
+unsafe impl<T: Sync> Sync for Lazy<T> {}
+
+#[macro_export]
+#[doc(hidden)]
+macro_rules! __lazy_static_create {
+ ($NAME:ident, $T:ty) => {
+ static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::INIT;
+ };
+}
+
+/// Polyfill for std::hint::unreachable_unchecked. There currently exists a
+/// [crate](https://docs.rs/unreachable) for an equivalent to std::hint::unreachable_unchecked, but
+/// lazy_static currently doesn't include any runtime dependencies and we've chosen to include this
+/// short polyfill rather than include a new crate in every consumer's build.
+///
+/// This should be replaced by std's version when lazy_static starts to require at least Rust 1.27.
+unsafe fn unreachable_unchecked() -> ! {
+ enum Void {}
+ match std::mem::uninitialized::<Void>() {}
+}
diff --git a/lazy-static/src/lib.rs b/lazy-static/src/lib.rs
new file mode 100644
index 0000000..42dc405
--- /dev/null
+++ b/lazy-static/src/lib.rs
@@ -0,0 +1,212 @@
+// Copyright 2016 lazy-static.rs Developers
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://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 macro for declaring lazily evaluated statics.
+
+Using this macro, it is possible to have `static`s that require code to be
+executed at runtime in order to be initialized.
+This includes anything requiring heap allocations, like vectors or hash maps,
+as well as anything that requires function calls to be computed.
+
+# Syntax
+
+```ignore
+lazy_static! {
+ [pub] static ref NAME_1: TYPE_1 = EXPR_1;
+ [pub] static ref NAME_2: TYPE_2 = EXPR_2;
+ ...
+ [pub] static ref NAME_N: TYPE_N = EXPR_N;
+}
+```
+
+Attributes (including doc comments) are supported as well:
+
+```rust
+# #[macro_use]
+# extern crate lazy_static;
+# fn main() {
+lazy_static! {
+ /// This is an example for using doc comment attributes
+ static ref EXAMPLE: u8 = 42;
+}
+# }
+```
+
+# Semantics
+
+For a given `static ref NAME: TYPE = EXPR;`, the macro generates a unique type that
+implements `Deref<TYPE>` and stores it in a static with name `NAME`. (Attributes end up
+attaching to this type.)
+
+On first deref, `EXPR` gets evaluated and stored internally, such that all further derefs
+can return a reference to the same object. Note that this can lead to deadlocks
+if you have multiple lazy statics that depend on each other in their initialization.
+
+Apart from the lazy initialization, the resulting "static ref" variables
+have generally the same properties as regular "static" variables:
+
+- Any type in them needs to fulfill the `Sync` trait.
+- If the type has a destructor, then it will not run when the process exits.
+
+# Example
+
+Using the macro:
+
+```rust
+#[macro_use]
+extern crate lazy_static;
+
+use std::collections::HashMap;
+
+lazy_static! {
+ static ref HASHMAP: HashMap<u32, &'static str> = {
+ let mut m = HashMap::new();
+ m.insert(0, "foo");
+ m.insert(1, "bar");
+ m.insert(2, "baz");
+ m
+ };
+ static ref COUNT: usize = HASHMAP.len();
+ static ref NUMBER: u32 = times_two(21);
+}
+
+fn times_two(n: u32) -> u32 { n * 2 }
+
+fn main() {
+ println!("The map has {} entries.", *COUNT);
+ println!("The entry for `0` is \"{}\".", HASHMAP.get(&0).unwrap());
+ println!("A expensive calculation on a static results in: {}.", *NUMBER);
+}
+```
+
+# Implementation details
+
+The `Deref` implementation uses a hidden static variable that is guarded by an atomic check on each access.
+
+# Cargo features
+
+This crate provides two cargo features:
+
+- `nightly`: This uses unstable language features only available on the nightly release channel for a more optimal implementation. In practice this currently means avoiding a heap allocation per static. This feature might get deprecated at a later point once all relevant optimizations are usable from stable.
+- `spin_no_std` (implies `nightly`): This allows using this crate in a no-std environment, by depending on the standalone `spin` crate.
+
+Both features depend on unstable language features, which means
+no guarantees can be made about them in regard to SemVer stability.
+
+*/
+
+#![doc(html_root_url = "https://docs.rs/lazy_static/1.2.0")]
+#![no_std]
+
+#[cfg(not(feature = "spin_no_std"))]
+#[path="inline_lazy.rs"]
+#[doc(hidden)]
+pub mod lazy;
+
+#[cfg(feature = "spin_no_std")]
+#[path="core_lazy.rs"]
+#[doc(hidden)]
+pub mod lazy;
+
+#[doc(hidden)]
+pub use core::ops::Deref as __Deref;
+
+#[macro_export(local_inner_macros)]
+#[doc(hidden)]
+macro_rules! __lazy_static_internal {
+ // optional visibility restrictions are wrapped in `()` to allow for
+ // explicitly passing otherwise implicit information about private items
+ ($(#[$attr:meta])* ($($vis:tt)*) static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
+ __lazy_static_internal!(@MAKE TY, $(#[$attr])*, ($($vis)*), $N);
+ __lazy_static_internal!(@TAIL, $N : $T = $e);
+ lazy_static!($($t)*);
+ };
+ (@TAIL, $N:ident : $T:ty = $e:expr) => {
+ impl $crate::__Deref for $N {
+ type Target = $T;
+ fn deref(&self) -> &$T {
+ #[inline(always)]
+ fn __static_ref_initialize() -> $T { $e }
+
+ #[inline(always)]
+ fn __stability() -> &'static $T {
+ __lazy_static_create!(LAZY, $T);
+ LAZY.get(__static_ref_initialize)
+ }
+ __stability()
+ }
+ }
+ impl $crate::LazyStatic for $N {
+ fn initialize(lazy: &Self) {
+ let _ = &**lazy;
+ }
+ }
+ };
+ // `vis` is wrapped in `()` to prevent parsing ambiguity
+ (@MAKE TY, $(#[$attr:meta])*, ($($vis:tt)*), $N:ident) => {
+ #[allow(missing_copy_implementations)]
+ #[allow(non_camel_case_types)]
+ #[allow(dead_code)]
+ $(#[$attr])*
+ $($vis)* struct $N {__private_field: ()}
+ #[doc(hidden)]
+ $($vis)* static $N: $N = $N {__private_field: ()};
+ };
+ () => ()
+}
+
+#[macro_export(local_inner_macros)]
+macro_rules! lazy_static {
+ ($(#[$attr:meta])* static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
+ // use `()` to explicitly forward the information about private items
+ __lazy_static_internal!($(#[$attr])* () static ref $N : $T = $e; $($t)*);
+ };
+ ($(#[$attr:meta])* pub static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
+ __lazy_static_internal!($(#[$attr])* (pub) static ref $N : $T = $e; $($t)*);
+ };
+ ($(#[$attr:meta])* pub ($($vis:tt)+) static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
+ __lazy_static_internal!($(#[$attr])* (pub ($($vis)+)) static ref $N : $T = $e; $($t)*);
+ };
+ () => ()
+}
+
+/// Support trait for enabling a few common operation on lazy static values.
+///
+/// This is implemented by each defined lazy static, and
+/// used by the free functions in this crate.
+pub trait LazyStatic {
+ #[doc(hidden)]
+ fn initialize(lazy: &Self);
+}
+
+/// Takes a shared reference to a lazy static and initializes
+/// it if it has not been already.
+///
+/// This can be used to control the initialization point of a lazy static.
+///
+/// Example:
+///
+/// ```rust
+/// #[macro_use]
+/// extern crate lazy_static;
+///
+/// lazy_static! {
+/// static ref BUFFER: Vec<u8> = (0..65537).collect();
+/// }
+///
+/// fn main() {
+/// lazy_static::initialize(&BUFFER);
+///
+/// // ...
+/// work_with_initialized_data(&BUFFER);
+/// }
+/// # fn work_with_initialized_data(_: &[u8]) {}
+/// ```
+pub fn initialize<T: LazyStatic>(lazy: &T) {
+ LazyStatic::initialize(lazy);
+}
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