1use core::future::Future;
2use core::pin::Pin;
3use core::task::{Context, Poll};
4
5use crate::stream::Stream;
6
7#[doc(hidden)]
8#[allow(missing_debug_implementations)]
9pub struct FindMapFuture<'a, S, F> {
10 stream: &'a mut S,
11 f: F,
12}
13
14impl<'a, S, F> FindMapFuture<'a, S, F> {
15 pub(super) fn new(stream: &'a mut S, f: F) -> Self {
16 Self { stream, f }
17 }
18}
19
20impl<S: Unpin, F> Unpin for FindMapFuture<'_, S, F> {}
21
22impl<'a, S, B, F> Future for FindMapFuture<'a, S, F>
23where
24 S: Stream + Unpin + Sized,
25 F: FnMut(S::Item) -> Option<B>,
26{
27 type Output = Option<B>;
28
29 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
30 let item: Option<::Item> = futures_core::ready!(Pin::new(&mut *self.stream).poll_next(cx));
31
32 match item {
33 Some(v: ::Item) => match (&mut self.f)(v) {
34 Some(v: B) => Poll::Ready(Some(v)),
35 None => {
36 cx.waker().wake_by_ref();
37 Poll::Pending
38 }
39 },
40 None => Poll::Ready(None),
41 }
42 }
43}
44