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pub(crate) mod one_shot_signal {
use std::{
cell::{Cell, RefCell},
rc::Rc,
task::Waker,
};
#[derive(Debug, Default)]
struct Inner {
set: Cell<bool>,
waker: RefCell<Option<Waker>>,
}
#[derive(Debug, Default)]
pub(crate) struct Sender {
inner: Rc<Inner>,
}
#[derive(Debug, Default)]
pub(crate) struct Receiver {
inner: Option<Rc<Inner>>,
}
impl std::future::Future for Receiver {
type Output = ();
fn poll(
mut self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Self::Output> {
if let Some(inner) = self.inner.as_mut() {
if inner.set.get() {
self.inner.take();
std::task::Poll::Ready(())
} else {
if inner
.waker
.borrow()
.as_ref()
.map(|waker| !waker.will_wake(cx.waker()))
.unwrap_or(true)
{
if let Some(old_waker) = std::mem::replace(
&mut *inner.waker.borrow_mut(),
Some(cx.waker().clone()),
) {
old_waker.wake();
}
}
std::task::Poll::Pending
}
} else {
std::task::Poll::Ready(())
}
}
}
impl futures_core::FusedFuture for Receiver {
fn is_terminated(&self) -> bool {
self.inner.is_none()
}
}
impl Sender {
pub fn send(&self) {
self.inner.set.set(true);
if let Some(waker) = self.inner.waker.borrow_mut().take() {
waker.wake();
}
}
}
pub(crate) fn new_pair() -> (Sender, Receiver) {
let inner = Rc::new(Inner::default());
(
Sender {
inner: inner.clone(),
},
Receiver { inner: Some(inner) },
)
}
}