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use std::cell::UnsafeCell;
use std::fmt;
use std::ops;
/// `AtomicUsize` providing an additional `unsync_load` function.
pub(crate) struct AtomicUsize {
inner: UnsafeCell<std::sync::atomic::AtomicUsize>,
}
unsafe impl Send for AtomicUsize {}
unsafe impl Sync for AtomicUsize {}
impl AtomicUsize {
pub(crate) const fn new(val: usize) -> AtomicUsize {
let inner = UnsafeCell::new(std::sync::atomic::AtomicUsize::new(val));
AtomicUsize { inner }
}
/// Performs an unsynchronized load.
///
/// # Safety
///
/// All mutations must have happened before the unsynchronized load.
/// Additionally, there must be no concurrent mutations.
pub(crate) unsafe fn unsync_load(&self) -> usize {
core::ptr::read(self.inner.get() as *const usize)
}
pub(crate) fn with_mut<R>(&mut self, f: impl FnOnce(&mut usize) -> R) -> R {
// safety: we have mutable access
f(unsafe { (*self.inner.get()).get_mut() })
}
}
impl ops::Deref for AtomicUsize {
type Target = std::sync::atomic::AtomicUsize;
fn deref(&self) -> &Self::Target {
// safety: it is always safe to access `&self` fns on the inner value as
// we never perform unsafe mutations.
unsafe { &*self.inner.get() }
}
}
impl ops::DerefMut for AtomicUsize {
fn deref_mut(&mut self) -> &mut Self::Target {
// safety: we hold `&mut self`
unsafe { &mut *self.inner.get() }
}
}
impl fmt::Debug for AtomicUsize {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
(**self).fmt(fmt)
}
}