1use std::cell::UnsafeCell;
2use std::fmt;
3use std::ops;
4
5/// `AtomicUsize` providing an additional `unsync_load` function.
6pub(crate) struct AtomicUsize {
7 inner: UnsafeCell<std::sync::atomic::AtomicUsize>,
8}
9
10unsafe impl Send for AtomicUsize {}
11unsafe impl Sync for AtomicUsize {}
12
13impl AtomicUsize {
14 pub(crate) const fn new(val: usize) -> AtomicUsize {
15 let inner = UnsafeCell::new(std::sync::atomic::AtomicUsize::new(val));
16 AtomicUsize { inner }
17 }
18
19 /// Performs an unsynchronized load.
20 ///
21 /// # Safety
22 ///
23 /// All mutations must have happened before the unsynchronized load.
24 /// Additionally, there must be no concurrent mutations.
25 pub(crate) unsafe fn unsync_load(&self) -> usize {
26 // See <https://github.com/tokio-rs/tokio/issues/6155>
27 self.load(std::sync::atomic::Ordering::Relaxed)
28 }
29
30 pub(crate) fn with_mut<R>(&mut self, f: impl FnOnce(&mut usize) -> R) -> R {
31 // safety: we have mutable access
32 f(unsafe { (*self.inner.get()).get_mut() })
33 }
34}
35
36impl ops::Deref for AtomicUsize {
37 type Target = std::sync::atomic::AtomicUsize;
38
39 fn deref(&self) -> &Self::Target {
40 // safety: it is always safe to access `&self` fns on the inner value as
41 // we never perform unsafe mutations.
42 unsafe { &*self.inner.get() }
43 }
44}
45
46impl ops::DerefMut for AtomicUsize {
47 fn deref_mut(&mut self) -> &mut Self::Target {
48 // safety: we hold `&mut self`
49 unsafe { &mut *self.inner.get() }
50 }
51}
52
53impl fmt::Debug for AtomicUsize {
54 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
55 (**self).fmt(fmt)
56 }
57}
58