1 | use std::cell::UnsafeCell; |
---|---|
2 | use std::fmt; |
3 | use std::ops; |
4 | use std::panic; |
5 | |
6 | /// `AtomicUsize` providing an additional `unsync_load` function. |
7 | pub(crate) struct AtomicUsize { |
8 | inner: UnsafeCell<std::sync::atomic::AtomicUsize>, |
9 | } |
10 | |
11 | unsafe impl Send for AtomicUsize {} |
12 | unsafe impl Sync for AtomicUsize {} |
13 | impl panic::RefUnwindSafe for AtomicUsize {} |
14 | impl panic::UnwindSafe for AtomicUsize {} |
15 | |
16 | impl AtomicUsize { |
17 | pub(crate) const fn new(val: usize) -> AtomicUsize { |
18 | let inner: UnsafeCell |
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 | |
38 | impl 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 | |
48 | impl 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 | |
55 | impl fmt::Debug for AtomicUsize { |
56 | fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { |
57 | (**self).fmt(fmt) |
58 | } |
59 | } |
60 |