1use std::cell::UnsafeCell;
2use std::fmt;
3use std::ops;
4use std::panic;
5
6/// `AtomicUsize` providing an additional `unsync_load` function.
7pub(crate) struct AtomicUsize {
8 inner: UnsafeCell<std::sync::atomic::AtomicUsize>,
9}
10
11unsafe impl Send for AtomicUsize {}
12unsafe impl Sync for AtomicUsize {}
13impl panic::RefUnwindSafe for AtomicUsize {}
14impl panic::UnwindSafe for AtomicUsize {}
15
16impl AtomicUsize {
17 pub(crate) const fn new(val: usize) -> AtomicUsize {
18 let inner: UnsafeCell = UnsafeCell::new(std::sync::atomic::AtomicUsize::new(val));
19 AtomicUsize { inner }
20 }
21
22 /// Performs an unsynchronized load.
23 ///
24 /// # Safety
25 ///
26 /// All mutations must have happened before the unsynchronized load.
27 /// Additionally, there must be no concurrent mutations.
28 pub(crate) unsafe fn unsync_load(&self) -> usize {
29 core::ptr::read(self.inner.get() as *const usize)
30 }
31
32 pub(crate) fn with_mut<R>(&mut self, f: impl FnOnce(&mut usize) -> R) -> R {
33 // safety: we have mutable access
34 f(unsafe { (*self.inner.get()).get_mut() })
35 }
36}
37
38impl ops::Deref for AtomicUsize {
39 type Target = std::sync::atomic::AtomicUsize;
40
41 fn deref(&self) -> &Self::Target {
42 // safety: it is always safe to access `&self` fns on the inner value as
43 // we never perform unsafe mutations.
44 unsafe { &*self.inner.get() }
45 }
46}
47
48impl ops::DerefMut for AtomicUsize {
49 fn deref_mut(&mut self) -> &mut Self::Target {
50 // safety: we hold `&mut self`
51 unsafe { &mut *self.inner.get() }
52 }
53}
54
55impl fmt::Debug for AtomicUsize {
56 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
57 (**self).fmt(fmt)
58 }
59}
60