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use super::{Inner, COMPLETE};
use crate::sync::spsc::SpscInner;
use alloc::sync::Arc;
use core::{
fmt,
future::Future,
pin::Pin,
sync::atomic::Ordering,
task::{Context, Poll},
};
const IS_TX_HALF: bool = false;
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Receiver<T> {
inner: Arc<Inner<T>>,
}
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub struct Canceled;
impl<T> Receiver<T> {
pub(super) fn new(inner: Arc<Inner<T>>) -> Self {
Self { inner }
}
#[inline]
pub fn close(&mut self) {
self.inner.close_half(IS_TX_HALF)
}
#[inline]
pub fn try_recv(&mut self) -> Result<Option<T>, Canceled> {
self.inner.try_recv()
}
}
impl<T> Future for Receiver<T> {
type Output = Result<T, Canceled>;
#[inline]
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
self.inner.poll_half(cx, IS_TX_HALF, Ordering::Acquire, Ordering::AcqRel, Inner::take)
}
}
impl<T> Drop for Receiver<T> {
#[inline]
fn drop(&mut self) {
self.inner.close_half(IS_TX_HALF);
}
}
impl<T> Inner<T> {
fn try_recv(&self) -> Result<Option<T>, Canceled> {
let state = self.state_load(Ordering::Acquire);
if state & COMPLETE == 0 {
Ok(None)
} else {
unsafe { &mut *self.data.get() }.take().ok_or(Canceled).map(Some)
}
}
fn take(&self, state: u8) -> Poll<Result<T, Canceled>> {
if state & COMPLETE == 0 {
Poll::Pending
} else {
Poll::Ready(unsafe { &mut *self.data.get() }.take().ok_or(Canceled))
}
}
}
impl fmt::Display for Canceled {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "oneshot canceled")
}
}