1use std::future::Future;
2use std::pin::Pin;
3use std::task::{Context, Poll};
4use std::time::Duration;
5
6use pin_project_lite::pin_project;
7
8use crate::io;
9use crate::utils::{timer_after, Timer};
10
11/// Awaits an I/O future or times out after a duration of time.
12///
13/// If you want to await a non I/O future consider using
14/// [`future::timeout`](../future/fn.timeout.html) instead.
15///
16/// # Examples
17///
18/// ```no_run
19/// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
20/// #
21/// use std::time::Duration;
22///
23/// use async_std::io;
24///
25/// io::timeout(Duration::from_secs(5), async {
26/// let stdin = io::stdin();
27/// let mut line = String::new();
28/// let n = stdin.read_line(&mut line).await?;
29/// Ok(())
30/// })
31/// .await?;
32/// #
33/// # Ok(()) }) }
34/// ```
35pub async fn timeout<F, T>(dur: Duration, f: F) -> io::Result<T>
36where
37 F: Future<Output = io::Result<T>>,
38{
39 Timeout {
40 timeout: timer_after(dur),
41 future: f,
42 }
43 .await
44}
45
46pin_project! {
47 /// Future returned by the `FutureExt::timeout` method.
48 #[derive(Debug)]
49 pub struct Timeout<F, T>
50 where
51 F: Future<Output = io::Result<T>>,
52 {
53 #[pin]
54 future: F,
55 #[pin]
56 timeout: Timer,
57 }
58}
59
60impl<F, T> Future for Timeout<F, T>
61where
62 F: Future<Output = io::Result<T>>,
63{
64 type Output = io::Result<T>;
65
66 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
67 let this: Projection<'_, F, T> = self.project();
68 match this.future.poll(cx) {
69 Poll::Pending => {}
70 other: Poll> => return other,
71 }
72
73 if this.timeout.poll(cx).is_ready() {
74 let err: Result = Err(io::Error::new(kind:io::ErrorKind::TimedOut, error:"future timed out"));
75 Poll::Ready(err)
76 } else {
77 Poll::Pending
78 }
79 }
80}
81