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use std::error::Error;
use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::time::Duration;
use pin_project_lite::pin_project;
use crate::task::{Context, Poll};
use crate::utils::{timer_after, Timer};
pub async fn timeout<F, T>(dur: Duration, f: F) -> Result<T, TimeoutError>
where
F: Future<Output = T>,
{
TimeoutFuture::new(f, dur).await
}
pin_project! {
pub struct TimeoutFuture<F> {
#[pin]
future: F,
#[pin]
delay: Timer,
}
}
impl<F> TimeoutFuture<F> {
#[allow(dead_code)]
pub(super) fn new(future: F, dur: Duration) -> TimeoutFuture<F> {
TimeoutFuture {
future,
delay: timer_after(dur),
}
}
}
impl<F: Future> Future for TimeoutFuture<F> {
type Output = Result<F::Output, TimeoutError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.project();
match this.future.poll(cx) {
Poll::Ready(v) => Poll::Ready(Ok(v)),
Poll::Pending => match this.delay.poll(cx) {
Poll::Ready(_) => Poll::Ready(Err(TimeoutError { _private: () })),
Poll::Pending => Poll::Pending,
},
}
}
}
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct TimeoutError {
_private: (),
}
impl Error for TimeoutError {}
impl fmt::Display for TimeoutError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
"future has timed out".fmt(f)
}
}