smol-rs
/
concurrent-queue
mirror of https://github.com/smol-rs/concurrent-queue
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Merge fetch_and andthe prev_value check 

cc https://github.com/smol-rs/concurrent-queue/pull/58#discussion_r1574686897

Signed-off-by: John Nunley <dev@notgull.net>
This commit is contained in:
John Nunley 2024-04-25 22:53:55 -07:00 committed by GitHub
parent 05e7bff8e5
commit 5b74dc8acc
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 16 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
src/single.rs
View File

@ -65,23 +65,27 @@ impl<T> Single<T> {
}
if prev == state {
// Swap out the value.
// SAFETY: We have locked the state.
let prev_value = unsafe {
self.slot
.with_mut(move |slot| ptr::replace(slot, MaybeUninit::new(value)))
// If the value was pushed, swap out the value.
let prev_value = if prev & PUSHED == 0 {
// SAFETY: write is safe because we have locked the state.
self.slot.with_mut(|slot| unsafe {
slot.write(MaybeUninit::new(value));
});
None
} else {
// SAFETY: replace is safe because we have locked the state, and
// assume_init is safe because we have checked that the value was pushed.
let prev_value = unsafe {
self.slot.with_mut(move |slot| {
ptr::replace(slot, MaybeUninit::new(value)).assume_init()
})
};
Some(prev_value)
};
// We can unlock the slot now.
self.state.fetch_and(!LOCKED, Ordering::Release);
// If the value was pushed, initialize it and return it.
let prev_value = if prev & PUSHED == 0 {
None
} else {
Some(unsafe { prev_value.assume_init() })
};
// Return the old value.
return Ok(prev_value);
}