1use core::fmt;
2use core::pin::Pin;
3use futures_core::future::{FusedFuture, Future};
4use futures_core::ready;
5use futures_core::stream::{FusedStream, Stream};
6use futures_core::task::{Context, Poll};
7use pin_project_lite::pin_project;
8
9pin_project! {
10 /// Future for the [`count`](super::StreamExt::count) method.
11 #[must_use = "futures do nothing unless you `.await` or poll them"]
12 pub struct Count<St> {
13 #[pin]
14 stream: St,
15 count: usize
16 }
17}
18
19impl<St> fmt::Debug for Count<St>
20where
21 St: fmt::Debug,
22{
23 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
24 f.debug_struct("Count").field("stream", &self.stream).field("count", &self.count).finish()
25 }
26}
27
28impl<St: Stream> Count<St> {
29 pub(super) fn new(stream: St) -> Self {
30 Self { stream, count: 0 }
31 }
32}
33
34impl<St: FusedStream> FusedFuture for Count<St> {
35 fn is_terminated(&self) -> bool {
36 self.stream.is_terminated()
37 }
38}
39
40impl<St: Stream> Future for Count<St> {
41 type Output = usize;
42
43 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
44 let mut this = self.project();
45
46 Poll::Ready(loop {
47 match ready!(this.stream.as_mut().poll_next(cx)) {
48 Some(_) => *this.count += 1,
49 None => break *this.count,
50 }
51 })
52 }
53}
54