forked from mirror/async-std
86 lines
2.1 KiB
Rust
86 lines
2.1 KiB
Rust
use std::error::Error;
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use std::fmt;
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use std::future::Future;
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use std::pin::Pin;
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use std::time::Duration;
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use pin_project_lite::pin_project;
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use crate::task::{Context, Poll};
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use crate::utils::Timer;
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/// Awaits a future or times out after a duration of time.
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///
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/// If you want to await an I/O future consider using
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/// [`io::timeout`](../io/fn.timeout.html) instead.
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///
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/// # Examples
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///
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/// ```
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/// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
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/// #
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/// use std::time::Duration;
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///
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/// use async_std::future;
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///
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/// let never = future::pending::<()>();
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/// let dur = Duration::from_millis(5);
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/// assert!(future::timeout(dur, never).await.is_err());
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/// #
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/// # Ok(()) }) }
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/// ```
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pub async fn timeout<F, T>(dur: Duration, f: F) -> Result<T, TimeoutError>
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where
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F: Future<Output = T>,
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{
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TimeoutFuture::new(f, dur).await
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}
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pin_project! {
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/// A future that times out after a duration of time.
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pub struct TimeoutFuture<F> {
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#[pin]
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future: F,
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#[pin]
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delay: Timer,
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}
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}
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impl<F> TimeoutFuture<F> {
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#[allow(dead_code)]
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pub(super) fn new(future: F, dur: Duration) -> TimeoutFuture<F> {
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TimeoutFuture {
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future,
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delay: Timer::after(dur),
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}
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}
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}
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impl<F: Future> Future for TimeoutFuture<F> {
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type Output = Result<F::Output, TimeoutError>;
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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let this = self.project();
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match this.future.poll(cx) {
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Poll::Ready(v) => Poll::Ready(Ok(v)),
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Poll::Pending => match this.delay.poll(cx) {
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Poll::Ready(_) => Poll::Ready(Err(TimeoutError { _private: () })),
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Poll::Pending => Poll::Pending,
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},
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}
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}
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}
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/// An error returned when a future times out.
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#[derive(Clone, Copy, Debug, Eq, PartialEq)]
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pub struct TimeoutError {
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_private: (),
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}
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impl Error for TimeoutError {}
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impl fmt::Display for TimeoutError {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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"future has timed out".fmt(f)
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}
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}
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