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feat(futures-util/stream): add StreamExt::unzip (#2263)
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Original file line number | Diff line number | Diff line change |
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use core::mem; | ||
use core::pin::Pin; | ||
use futures_core::future::{FusedFuture, Future}; | ||
use futures_core::stream::{FusedStream, Stream}; | ||
use futures_core::task::{Context, Poll}; | ||
use pin_project::pin_project; | ||
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/// Future for the [`unzip`](super::StreamExt::unzip) method. | ||
#[pin_project] | ||
#[derive(Debug)] | ||
#[must_use = "futures do nothing unless you `.await` or poll them"] | ||
pub struct Unzip<St, FromA, FromB> { | ||
#[pin] | ||
stream: St, | ||
left: FromA, | ||
right: FromB, | ||
} | ||
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impl<St: Stream, FromA: Default, FromB: Default> Unzip<St, FromA, FromB> { | ||
fn finish(self: Pin<&mut Self>) -> (FromA, FromB) { | ||
let this = self.project(); | ||
( | ||
mem::replace(this.left, Default::default()), | ||
mem::replace(this.right, Default::default()), | ||
) | ||
} | ||
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pub(super) fn new(stream: St) -> Self { | ||
Self { | ||
stream, | ||
left: Default::default(), | ||
right: Default::default(), | ||
} | ||
} | ||
} | ||
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impl<St, A, B, FromA, FromB> FusedFuture for Unzip<St, FromA, FromB> | ||
where St: FusedStream<Item = (A, B)>, | ||
FromA: Default + Extend<A>, | ||
FromB: Default + Extend<B>, | ||
{ | ||
fn is_terminated(&self) -> bool { | ||
self.stream.is_terminated() | ||
} | ||
} | ||
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impl<St, A, B, FromA, FromB> Future for Unzip<St, FromA, FromB> | ||
where St: Stream<Item = (A, B)>, | ||
FromA: Default + Extend<A>, | ||
FromB: Default + Extend<B>, | ||
{ | ||
type Output = (FromA, FromB); | ||
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fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<(FromA, FromB)> { | ||
let mut this = self.as_mut().project(); | ||
loop { | ||
match ready!(this.stream.as_mut().poll_next(cx)) { | ||
Some(e) => { | ||
this.left.extend(Some(e.0)); | ||
this.right.extend(Some(e.1)); | ||
}, | ||
None => return Poll::Ready(self.finish()), | ||
} | ||
} | ||
} | ||
} |
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