tokio/loom/std/
atomic_usize.rs

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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}
tokio/loom/std/atomic_usize.rs

tokio/loom/std/
atomic_usize.rs
