tokio/loom/std/
atomic_usize.rs

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::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        // See <https://github.com/tokio-rs/tokio/issues/6155>
30        self.load(std::sync::atomic::Ordering::Relaxed)
31    }
32
33    pub(crate) fn with_mut<R>(&mut self, f: impl FnOnce(&mut usize) -> R) -> R {
34        // safety: we have mutable access
35        f(unsafe { (*self.inner.get()).get_mut() })
36    }
37}
38
39impl ops::Deref for AtomicUsize {
40    type Target = std::sync::atomic::AtomicUsize;
41
42    fn deref(&self) -> &Self::Target {
43        // safety: it is always safe to access `&self` fns on the inner value as
44        // we never perform unsafe mutations.
45        unsafe { &*self.inner.get() }
46    }
47}
48
49impl ops::DerefMut for AtomicUsize {
50    fn deref_mut(&mut self) -> &mut Self::Target {
51        // safety: we hold `&mut self`
52        unsafe { &mut *self.inner.get() }
53    }
54}
55
56impl fmt::Debug for AtomicUsize {
57    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
58        (**self).fmt(fmt)
59    }
60}
tokio/loom/std/atomic_usize.rs

tokio/loom/std/
atomic_usize.rs
