futures_util/stream/try_stream/
try_flatten.rs

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1use core::pin::Pin;
2use futures_core::ready;
3use futures_core::stream::{FusedStream, Stream, TryStream};
4use futures_core::task::{Context, Poll};
5#[cfg(feature = "sink")]
6use futures_sink::Sink;
7use pin_project_lite::pin_project;
8
9pin_project! {
10    /// Stream for the [`try_flatten`](super::TryStreamExt::try_flatten) method.
11    #[derive(Debug)]
12    #[must_use = "streams do nothing unless polled"]
13    pub struct TryFlatten<St>
14    where
15        St: TryStream,
16    {
17        #[pin]
18        stream: St,
19        #[pin]
20        next: Option<St::Ok>,
21    }
22}
23
24impl<St> TryFlatten<St>
25where
26    St: TryStream,
27    St::Ok: TryStream,
28    <St::Ok as TryStream>::Error: From<St::Error>,
29{
30    pub(super) fn new(stream: St) -> Self {
31        Self { stream, next: None }
32    }
33
34    delegate_access_inner!(stream, St, ());
35}
36
37impl<St> FusedStream for TryFlatten<St>
38where
39    St: TryStream + FusedStream,
40    St::Ok: TryStream,
41    <St::Ok as TryStream>::Error: From<St::Error>,
42{
43    fn is_terminated(&self) -> bool {
44        self.next.is_none() && self.stream.is_terminated()
45    }
46}
47
48impl<St> Stream for TryFlatten<St>
49where
50    St: TryStream,
51    St::Ok: TryStream,
52    <St::Ok as TryStream>::Error: From<St::Error>,
53{
54    type Item = Result<<St::Ok as TryStream>::Ok, <St::Ok as TryStream>::Error>;
55
56    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
57        let mut this = self.project();
58
59        Poll::Ready(loop {
60            if let Some(s) = this.next.as_mut().as_pin_mut() {
61                if let Some(item) = ready!(s.try_poll_next(cx)?) {
62                    break Some(Ok(item));
63                } else {
64                    this.next.set(None);
65                }
66            } else if let Some(s) = ready!(this.stream.as_mut().try_poll_next(cx)?) {
67                this.next.set(Some(s));
68            } else {
69                break None;
70            }
71        })
72    }
73}
74
75// Forwarding impl of Sink from the underlying stream
76#[cfg(feature = "sink")]
77impl<S, Item> Sink<Item> for TryFlatten<S>
78where
79    S: TryStream + Sink<Item>,
80{
81    type Error = <S as Sink<Item>>::Error;
82
83    delegate_sink!(stream, Item);
84}
futures_util/stream/try_stream/try_flatten.rs

futures_util/stream/try_stream/
try_flatten.rs
