1use core::fmt;
2use core::pin::Pin;
3use futures_core::future::{FusedFuture, Future};
4use futures_core::ready;
5use futures_core::stream::Stream;
6use futures_core::task::{Context, Poll};
7use pin_project_lite::pin_project;
8
9pin_project! {
10 /// Future for the [`any`](super::StreamExt::any) method.
11 #[must_use = "futures do nothing unless you `.await` or poll them"]
12 pub struct Any<St, Fut, F> {
13 #[pin]
14 stream: St,
15 f: F,
16 done: bool,
17 #[pin]
18 future: Option<Fut>,
19 }
20}
21
22impl<St, Fut, F> fmt::Debug for Any<St, Fut, F>
23where
24 St: fmt::Debug,
25 Fut: fmt::Debug,
26{
27 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
28 f.debug_struct("Any")
29 .field("stream", &self.stream)
30 .field("done", &self.done)
31 .field("future", &self.future)
32 .finish()
33 }
34}
35
36impl<St, Fut, F> Any<St, Fut, F>
37where
38 St: Stream,
39 F: FnMut(St::Item) -> Fut,
40 Fut: Future<Output = bool>,
41{
42 pub(super) fn new(stream: St, f: F) -> Self {
43 Self { stream, f, done: false, future: None }
44 }
45}
46
47impl<St, Fut, F> FusedFuture for Any<St, Fut, F>
48where
49 St: Stream,
50 F: FnMut(St::Item) -> Fut,
51 Fut: Future<Output = bool>,
52{
53 fn is_terminated(&self) -> bool {
54 self.done && self.future.is_none()
55 }
56}
57
58impl<St, Fut, F> Future for Any<St, Fut, F>
59where
60 St: Stream,
61 F: FnMut(St::Item) -> Fut,
62 Fut: Future<Output = bool>,
63{
64 type Output = bool;
65
66 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<bool> {
67 let mut this = self.project();
68 Poll::Ready(loop {
69 if let Some(fut) = this.future.as_mut().as_pin_mut() {
70 // we're currently processing a future to produce a new value
71 let res = ready!(fut.poll(cx));
72 this.future.set(None);
73 if res {
74 *this.done = true;
75 break true;
76 } // early exit
77 } else if !*this.done {
78 // we're waiting on a new item from the stream
79 match ready!(this.stream.as_mut().poll_next(cx)) {
80 Some(item) => {
81 this.future.set(Some((this.f)(item)));
82 }
83 None => {
84 *this.done = true;
85 break false;
86 }
87 }
88 } else {
89 panic!("Any polled after completion")
90 }
91 })
92 }
93}
94