1use crate::Stream;
2
3use pin_project_lite::pin_project;
4use std::pin::Pin;
5use std::task::{Context, Poll};
6
7pin_project! {
8 /// Stream returned by [`fuse()`][super::StreamExt::fuse].
9 #[derive(Debug)]
10 pub struct Fuse<T> {
11 #[pin]
12 stream: Option<T>,
13 }
14}
15
16impl<T> Fuse<T>
17where
18 T: Stream,
19{
20 pub(crate) fn new(stream: T) -> Fuse<T> {
21 Fuse {
22 stream: Some(stream),
23 }
24 }
25}
26
27impl<T> Stream for Fuse<T>
28where
29 T: Stream,
30{
31 type Item = T::Item;
32
33 fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
34 let res = match Option::as_pin_mut(self.as_mut().project().stream) {
35 Some(stream) => ready!(stream.poll_next(cx)),
36 None => return Poll::Ready(None),
37 };
38
39 if res.is_none() {
40 // Do not poll the stream anymore
41 self.as_mut().project().stream.set(None);
42 }
43
44 Poll::Ready(res)
45 }
46
47 fn size_hint(&self) -> (usize, Option<usize>) {
48 match self.stream {
49 Some(ref stream) => stream.size_hint(),
50 None => (0, Some(0)),
51 }
52 }
53}
54