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: ::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}
43