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use core::ptr;
use core::ptr::NonNull;
use core::sync::atomic::{AtomicPtr, Ordering};
use core::task::Waker;
/// Utility struct to register and wake a waker.
/// If a waker is registered, registering another waker will replace the previous one without waking it.
/// The intended use case is to wake tasks from interrupts. Therefore, it is generally not expected,
/// that multiple tasks register try to register a waker simultaneously.
#[derive(Debug)]
pub struct AtomicWaker {
waker: AtomicPtr<()>,
}
impl AtomicWaker {
/// Create a new `AtomicWaker`.
pub const fn new() -> Self {
Self {
waker: AtomicPtr::new(ptr::null_mut()),
}
}
/// Register a waker. Overwrites the previous waker, if any.
pub fn register(&self, w: &Waker) {
self.waker.store(w.as_turbo_ptr().as_ptr() as _, Ordering::Release);
}
/// Wake the registered waker, if any.
pub fn wake(&self) {
if let Some(ptr) = NonNull::new(self.waker.load(Ordering::Acquire)) {
unsafe { Waker::from_turbo_ptr(ptr) }.wake();
}
}
}
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