stream: add StreamExt::timeout() (#2149)

1 files changed, 65 insertions, 0 deletions

diff --git a/tokio/src/stream/timeout.rs b/tokio/src/stream/timeout.rs
new file mode 100644
index 00000000..b8a2024f
--- /dev/null
+++ b/tokio/src/stream/timeout.rs
@@ -0,0 +1,65 @@
+use crate::stream::{Fuse, Stream};
+use crate::time::{Delay, Elapsed, Instant};
+
+use core::future::Future;
+use core::pin::Pin;
+use core::task::{Context, Poll};
+use pin_project_lite::pin_project;
+use std::time::Duration;
+
+pin_project! {
+    /// Stream returned by the [`timeout`](super::StreamExt::timeout) method.
+    #[must_use = "streams do nothing unless polled"]
+    #[derive(Debug)]
+    pub struct Timeout<S> {
+        #[pin]
+        stream: Fuse<S>,
+        deadline: Delay,
+        duration: Duration,
+        poll_deadline: bool,
+    }
+}
+
+impl<S: Stream> Timeout<S> {
+    pub(super) fn new(stream: S, duration: Duration) -> Self {
+        let next = Instant::now() + duration;
+        let deadline = Delay::new_timeout(next, duration);
+
+        Timeout {
+            stream: Fuse::new(stream),
+            deadline,
+            duration,
+            poll_deadline: true,
+        }
+    }
+}
+
+impl<S: Stream> Stream for Timeout<S> {
+    type Item = Result<S::Item, Elapsed>;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        match self.as_mut().project().stream.poll_next(cx) {
+            Poll::Ready(v) => {
+                if v.is_some() {
+                    let next = Instant::now() + self.duration;
+                    self.as_mut().project().deadline.reset(next);
+                    *self.as_mut().project().poll_deadline = true;
+                }
+                return Poll::Ready(v.map(Ok));
+            }
+            Poll::Pending => {}
+        };
+
+        if self.poll_deadline {
+            ready!(Pin::new(self.as_mut().project().deadline).poll(cx));
+            *self.as_mut().project().poll_deadline = false;
+            return Poll::Ready(Some(Err(Elapsed::new())));
+        }
+
+        Poll::Pending
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.stream.size_hint()
+    }
+}