Add timeout

examples/async-echo.rs

@@ -7,7 +7,7 @@ async fn echo_to(port: u16) -> Result<(), Box<dyn std::error::Error>> {
 
     let stream = TcpStream::connect(sockaddr)?;
     stream.set_nonblocking(true)?;
-    let mut stream = Async::new(stream);
+    let mut stream = Async::new(stream)?;
 
     println!("Connected");
 

src/time.rs

@@ -20,6 +20,18 @@ pub fn interval_at(instant: Instant, duration: Duration) -> Interval {
     }
 }
 
+pub fn timeout<F: std::future::Future + Unpin>(duration: Duration, future: F) -> Timeout<F> {
+    Timeout {
+        timer: Timer::new(duration),
+        future,
+    }
+}
+
+pub struct Timeout<F> {
+    timer: Timer,
+    future: F,
+}
+
 pub struct Interval {
     next: Instant,
     duration: Duration,
@@ -46,3 +58,23 @@ impl Interval {
         Timer::new(duration)
     }
 }
+
+impl<F> std::future::Future for Timeout<F>
+where
+    F: std::future::Future + Unpin,
+{
+    type Output = std::io::Result<F::Output>;
+
+    fn poll(
+        self: std::pin::Pin<&mut Self>,
+        cx: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Self::Output> {
+        let this = self.get_mut();
+
+        if std::pin::Pin::new(&mut this.timer).poll(cx).is_ready() {
+            return std::task::Poll::Ready(Err(std::io::ErrorKind::TimedOut.into()));
+        }
+
+        std::pin::Pin::new(&mut this.future).poll(cx).map(Ok)
+    }
+}