1use core::pin::Pin;
2use futures_core::future::Future;
3use futures_core::ready;
4use futures_core::stream::TryStream;
5use futures_core::task::{Context, Poll};
6use pin_project_lite::pin_project;
7
8pin_project! {
9 /// Future for the [`try_concat`](super::TryStreamExt::try_concat) method.
10 #[derive(Debug)]
11 #[must_use = "futures do nothing unless you `.await` or poll them"]
12 pub struct TryConcat<St: TryStream> {
13 #[pin]
14 stream: St,
15 accum: Option<St::Ok>,
16 }
17}
18
19impl<St> TryConcat<St>
20where
21 St: TryStream,
22 St::Ok: Extend<<St::Ok as IntoIterator>::Item> + IntoIterator + Default,
23{
24 pub(super) fn new(stream: St) -> Self {
25 Self { stream, accum: None }
26 }
27}
28
29impl<St> Future for TryConcat<St>
30where
31 St: TryStream,
32 St::Ok: Extend<<St::Ok as IntoIterator>::Item> + IntoIterator + Default,
33{
34 type Output = Result<St::Ok, St::Error>;
35
36 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
37 let mut this: Projection<'_, St> = self.project();
38
39 Poll::Ready(Ok(loop {
40 if let Some(x: impl Extend<<::Ok as IntoIterator>::Item> + IntoIterator + Default) = ready!(this.stream.as_mut().try_poll_next(cx)?) {
41 if let Some(a: &mut impl Extend<<::Ok as IntoIterator>::Item> + IntoIterator + Default) = this.accum {
42 a.extend(iter:x)
43 } else {
44 *this.accum = Some(x)
45 }
46 } else {
47 break this.accum.take().unwrap_or_default();
48 }
49 }))
50 }
51}
52