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stream::ForEach can no longer block indefinitely #2224

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stream::ForEach can no longer block indefinitely #2224

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ea589a6
stream::ForEach can no longer block indefinitely
Lucretiel Oct 2, 2020
d40e242
Merge branch 'master' into foreach-noloop
Lucretiel Oct 6, 2020
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43 changes: 24 additions & 19 deletions futures-util/src/stream/stream/for_each.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,10 @@ where
}

impl<St, Fut, F> ForEach<St, Fut, F>
where St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
where
St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
pub(super) fn new(stream: St, f: F) -> ForEach<St, Fut, F> {
ForEach {
Expand All @@ -44,34 +45,38 @@ where St: Stream,
}

impl<St, Fut, F> FusedFuture for ForEach<St, Fut, F>
where St: FusedStream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
where
St: FusedStream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
fn is_terminated(&self) -> bool {
self.future.is_none() && self.stream.is_terminated()
}
}

impl<St, Fut, F> Future for ForEach<St, Fut, F>
where St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
where
St: Stream,
F: FnMut(St::Item) -> Fut,
Fut: Future<Output = ()>,
{
type Output = ();

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
let mut this = self.project();
loop {
if let Some(fut) = this.future.as_mut().as_pin_mut() {
ready!(fut.poll(cx));
this.future.set(None);
} else if let Some(item) = ready!(this.stream.as_mut().poll_next(cx)) {
this.future.set(Some((this.f)(item)));
} else {
break;
}

if let Some(fut) = this.future.as_mut().as_pin_mut() {
ready!(fut.poll(cx));
cx.waker().wake_by_ref();
this.future.set(None);
Poll::Pending
} else if let Some(item) = ready!(this.stream.as_mut().poll_next(cx)) {
cx.waker().wake_by_ref();
this.future.set(Some((this.f)(item)));
Poll::Pending
} else {
Poll::Ready(())
}
Poll::Ready(())
}
}