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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
// This code was copied and then modified from Tokio.
/*
* Copyright (c) 2021 Tokio Contributors
*
* Permission is hereby granted, free of charge, to any
* person obtaining a copy of this software and associated
* documentation files (the "Software"), to deal in the
* Software without restriction, including without
* limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software
* is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice
* shall be included in all copies or substantial portions
* of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
* ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
* SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
* IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
//! Provides the [`Timeout`] future for adding a timeout to another future.
use pin_project_lite::pin_project;
use std::error::Error;
use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
/// Error returned when [`Timeout`] times out
#[derive(Debug)]
pub struct TimedOutError;
impl Error for TimedOutError {}
impl fmt::Display for TimedOutError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "timed out")
}
}
pin_project! {
/// Timeout Future
#[non_exhaustive]
#[must_use = "futures do nothing unless you `.await` or poll them"]
#[derive(Debug)]
pub struct Timeout<T, S> {
#[pin]
value: T,
#[pin]
sleep: S,
}
}
impl<T, S> Timeout<T, S> {
/// Create a new future that will race `value` and `sleep`.
///
/// If `sleep` resolves first, a timeout error is returned. Otherwise, the value is returned.
pub fn new(value: T, sleep: S) -> Timeout<T, S> {
Timeout { value, sleep }
}
}
impl<T, S> Future for Timeout<T, S>
where
T: Future,
S: Future,
{
type Output = Result<T::Output, TimedOutError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let me = self.project();
// First, try polling the future
if let Poll::Ready(v) = me.value.poll(cx) {
return Poll::Ready(Ok(v));
}
// Now check the timer
match me.sleep.poll(cx) {
Poll::Ready(_) => Poll::Ready(Err(TimedOutError)),
Poll::Pending => Poll::Pending,
}
}
}
#[cfg(test)]
mod tests {
use super::{TimedOutError, Timeout};
use crate::future::never::Never;
#[tokio::test]
async fn success() {
assert!(matches!(
Timeout::new(async { Ok::<isize, isize>(5) }, Never).await,
Ok(Ok(5))
));
}
#[tokio::test]
async fn failure() {
assert!(matches!(
Timeout::new(async { Err::<isize, isize>(0) }, Never).await,
Ok(Err(0))
));
}
#[tokio::test]
async fn timeout() {
assert!(matches!(
Timeout::new(Never, async {}).await,
Err(TimedOutError)
));
}
// If the value is available at the same time as the timeout, then return the value
#[tokio::test]
async fn prefer_value_to_timeout() {
assert!(matches!(Timeout::new(async { 5 }, async {}).await, Ok(5)));
}
}