futures_util/stream/try_stream/
try_for_each.rs

1use core::fmt;
2use core::pin::Pin;
3use futures_core::future::{Future, TryFuture};
4use futures_core::ready;
5use futures_core::stream::TryStream;
6use futures_core::task::{Context, Poll};
7use pin_project_lite::pin_project;
8
9pin_project! {
10    /// Future for the [`try_for_each`](super::TryStreamExt::try_for_each) method.
11    #[must_use = "futures do nothing unless you `.await` or poll them"]
12    pub struct TryForEach<St, Fut, F> {
13        #[pin]
14        stream: St,
15        f: F,
16        #[pin]
17        future: Option<Fut>,
18    }
19}
20
21impl<St, Fut, F> fmt::Debug for TryForEach<St, Fut, F>
22where
23    St: fmt::Debug,
24    Fut: fmt::Debug,
25{
26    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
27        f.debug_struct("TryForEach")
28            .field("stream", &self.stream)
29            .field("future", &self.future)
30            .finish()
31    }
32}
33
34impl<St, Fut, F> TryForEach<St, Fut, F>
35where
36    St: TryStream,
37    F: FnMut(St::Ok) -> Fut,
38    Fut: TryFuture<Ok = (), Error = St::Error>,
39{
40    pub(super) fn new(stream: St, f: F) -> Self {
41        Self { stream, f, future: None }
42    }
43}
44
45impl<St, Fut, F> Future for TryForEach<St, Fut, F>
46where
47    St: TryStream,
48    F: FnMut(St::Ok) -> Fut,
49    Fut: TryFuture<Ok = (), Error = St::Error>,
50{
51    type Output = Result<(), St::Error>;
52
53    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
54        let mut this = self.project();
55        loop {
56            if let Some(fut) = this.future.as_mut().as_pin_mut() {
57                ready!(fut.try_poll(cx))?;
58                this.future.set(None);
59            } else {
60                match ready!(this.stream.as_mut().try_poll_next(cx)?) {
61                    Some(e) => this.future.set(Some((this.f)(e))),
62                    None => break,
63                }
64            }
65        }
66        Poll::Ready(Ok(()))
67    }
68}