58 lines
1.6 KiB
Rust
58 lines
1.6 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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extern crate core;
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extern crate std;
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use self::std::prelude::v1::*;
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use self::std::cell::Cell;
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use self::std::hint::unreachable_unchecked;
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use self::std::sync::Once;
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#[allow(deprecated)]
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pub use self::std::sync::ONCE_INIT;
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// FIXME: Replace Option<T> with MaybeUninit<T> (stable since 1.36.0)
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pub struct Lazy<T: Sync>(Cell<Option<T>>, Once);
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impl<T: Sync> Lazy<T> {
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#[allow(deprecated)]
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pub const INIT: Self = Lazy(Cell::new(None), ONCE_INIT);
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#[inline(always)]
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pub fn get<F>(&'static self, f: F) -> &T
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where
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F: FnOnce() -> T,
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{
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self.1.call_once(|| {
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self.0.set(Some(f()));
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});
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// `self.0` is guaranteed to be `Some` by this point
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// The `Once` will catch and propagate panics
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unsafe {
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match *self.0.as_ptr() {
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Some(ref x) => x,
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None => {
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debug_assert!(false, "attempted to derefence an uninitialized lazy static. This is a bug");
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unreachable_unchecked()
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},
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}
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}
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}
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}
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unsafe impl<T: Sync> Sync for Lazy<T> {}
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#[macro_export]
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#[doc(hidden)]
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macro_rules! __lazy_static_create {
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($NAME:ident, $T:ty) => {
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static $NAME: $crate::lazy::Lazy<$T> = $crate::lazy::Lazy::INIT;
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};
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}
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