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90 lines
3.3 KiB
Rust
90 lines
3.3 KiB
Rust
// Copyright 2016 lazy-static.rs Developers
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//
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// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
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// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
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// http://opensource.org/licenses/MIT>, at your option. This file may not be
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// copied, modified, or distributed except according to those terms.
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/*!
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A macro for declaring lazily evaluated statics.
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Using this macro, it is possible to have `static`s that require code to be
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executed at runtime in order to be initialized.
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This includes anything requiring heap allocations, like vectors or hash maps,
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as well as anything that requires function calls to be computed.
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*/
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#[path = "core_lazy.rs"]
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pub(crate) mod lazy;
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#[doc(hidden)]
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pub(crate) use core::ops::Deref as __Deref;
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#[macro_export]
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#[doc(hidden)]
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macro_rules! __lazy_static_internal {
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// optional visibility restrictions are wrapped in `()` to allow for
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// explicitly passing otherwise implicit information about private items
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($(#[$attr:meta])* ($($vis:tt)*) static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
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$crate::__lazy_static_internal!(@MAKE TY, $(#[$attr])*, ($($vis)*), $N);
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$crate::__lazy_static_internal!(@TAIL, $N : $T = $e);
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$crate::lazy_static!($($t)*);
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};
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(@TAIL, $N:ident : $T:ty = $e:expr) => {
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impl $crate::lazy_static::__Deref for $N {
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type Target = $T;
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fn deref(&self) -> &$T {
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#[inline(always)]
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fn __static_ref_initialize() -> $T { $e }
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#[inline(always)]
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fn __stability() -> &'static $T {
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$crate::__lazy_static_create!(LAZY, $T);
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LAZY.get(__static_ref_initialize)
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}
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__stability()
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}
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}
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impl $crate::lazy_static::LazyStatic for $N {
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fn initialize(lazy: &Self) {
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let _ = &**lazy;
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}
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}
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};
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// `vis` is wrapped in `()` to prevent parsing ambiguity
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(@MAKE TY, $(#[$attr:meta])*, ($($vis:tt)*), $N:ident) => {
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#[allow(missing_copy_implementations)]
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#[allow(non_camel_case_types)]
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#[allow(dead_code)]
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$(#[$attr])*
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$($vis)* struct $N {__private_field: ()}
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#[doc(hidden)]
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$($vis)* static $N: $N = $N {__private_field: ()};
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};
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() => ()
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}
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#[macro_export]
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#[doc(hidden)]
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macro_rules! lazy_static {
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($(#[$attr:meta])* static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
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// use `()` to explicitly forward the information about private items
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$crate::__lazy_static_internal!($(#[$attr])* () static ref $N : $T = $e; $($t)*);
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};
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($(#[$attr:meta])* pub static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
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$crate::__lazy_static_internal!($(#[$attr])* (pub) static ref $N : $T = $e; $($t)*);
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};
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($(#[$attr:meta])* pub ($($vis:tt)+) static ref $N:ident : $T:ty = $e:expr; $($t:tt)*) => {
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$crate::__lazy_static_internal!($(#[$attr])* (pub ($($vis)+)) static ref $N : $T = $e; $($t)*);
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};
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() => ()
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}
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/// Support trait for enabling a few common operation on lazy static values.
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///
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/// This is implemented by each defined lazy static, and
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/// used by the free functions in this crate.
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pub(crate) trait LazyStatic {
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#[doc(hidden)]
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fn initialize(lazy: &Self);
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}
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