tokio_stream/stream_ext/
try_next.rs

1use crate::stream_ext::Next;
2use crate::Stream;
3
4use core::future::Future;
5use core::marker::PhantomPinned;
6use core::pin::Pin;
7use core::task::{Context, Poll};
8use pin_project_lite::pin_project;
9
10pin_project! {
11    /// Future for the [`try_next`](super::StreamExt::try_next) method.
12    ///
13    /// # Cancel safety
14    ///
15    /// This method is cancel safe. It only
16    /// holds onto a reference to the underlying stream,
17    /// so dropping it will never lose a value.
18    #[derive(Debug)]
19    #[must_use = "futures do nothing unless you `.await` or poll them"]
20    pub struct TryNext<'a, St: ?Sized> {
21        #[pin]
22        inner: Next<'a, St>,
23        // Make this future `!Unpin` for compatibility with async trait methods.
24        #[pin]
25        _pin: PhantomPinned,
26    }
27}
28
29impl<'a, St: ?Sized> TryNext<'a, St> {
30    pub(super) fn new(stream: &'a mut St) -> Self {
31        Self {
32            inner: Next::new(stream),
33            _pin: PhantomPinned,
34        }
35    }
36}
37
38impl<T, E, St: ?Sized + Stream<Item = Result<T, E>> + Unpin> Future for TryNext<'_, St> {
39    type Output = Result<Option<T>, E>;
40
41    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
42        let me = self.project();
43        me.inner.poll(cx).map(Option::transpose)
44    }
45}
tokio_stream/stream_ext/try_next.rs

tokio_stream/stream_ext/
try_next.rs
