futures_util/stream/stream/
select_next_some.rs

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1use crate::stream::StreamExt;
2use core::pin::Pin;
3use futures_core::future::{FusedFuture, Future};
4use futures_core::ready;
5use futures_core::stream::FusedStream;
6use futures_core::task::{Context, Poll};
7
8/// Future for the [`select_next_some`](super::StreamExt::select_next_some)
9/// method.
10#[derive(Debug)]
11#[must_use = "futures do nothing unless you `.await` or poll them"]
12pub struct SelectNextSome<'a, St: ?Sized> {
13    stream: &'a mut St,
14}
15
16impl<'a, St: ?Sized> SelectNextSome<'a, St> {
17    pub(super) fn new(stream: &'a mut St) -> Self {
18        Self { stream }
19    }
20}
21
22impl<St: ?Sized + FusedStream + Unpin> FusedFuture for SelectNextSome<'_, St> {
23    fn is_terminated(&self) -> bool {
24        self.stream.is_terminated()
25    }
26}
27
28impl<St: ?Sized + FusedStream + Unpin> Future for SelectNextSome<'_, St> {
29    type Output = St::Item;
30
31    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
32        assert!(!self.stream.is_terminated(), "SelectNextSome polled after terminated");
33
34        if let Some(item) = ready!(self.stream.poll_next_unpin(cx)) {
35            Poll::Ready(item)
36        } else {
37            debug_assert!(self.stream.is_terminated());
38            cx.waker().wake_by_ref();
39            Poll::Pending
40        }
41    }
42}
futures_util/stream/stream/select_next_some.rs

futures_util/stream/stream/
select_next_some.rs
