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// Copyright 2016 lazy-static.rs Developers
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// 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::hint::unreachable_unchecked;
use self::std::sync::Once;
#[allow(deprecated)]
pub use self::std::sync::ONCE_INIT;
// FIXME: Replace Option<T> with MaybeUninit<T> (stable since 1.36.0)
pub struct Lazy<T: Sync>(Cell<Option<T>>, Once);
impl<T: Sync> Lazy<T> {
#[allow(deprecated)]
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 propagate 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;
};
}