diff options
Diffstat (limited to 'third_party/rust/tokio-stream/src/stream_ext/try_next.rs')
-rw-r--r-- | third_party/rust/tokio-stream/src/stream_ext/try_next.rs | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/third_party/rust/tokio-stream/src/stream_ext/try_next.rs b/third_party/rust/tokio-stream/src/stream_ext/try_next.rs new file mode 100644 index 0000000000..93aa3bc15f --- /dev/null +++ b/third_party/rust/tokio-stream/src/stream_ext/try_next.rs @@ -0,0 +1,45 @@ +use crate::stream_ext::Next; +use crate::Stream; + +use core::future::Future; +use core::marker::PhantomPinned; +use core::pin::Pin; +use core::task::{Context, Poll}; +use pin_project_lite::pin_project; + +pin_project! { + /// Future for the [`try_next`](super::StreamExt::try_next) method. + /// + /// # Cancel safety + /// + /// This method is cancel safe. It only + /// holds onto a reference to the underlying stream, + /// so dropping it will never lose a value. + #[derive(Debug)] + #[must_use = "futures do nothing unless you `.await` or poll them"] + pub struct TryNext<'a, St: ?Sized> { + #[pin] + inner: Next<'a, St>, + // Make this future `!Unpin` for compatibility with async trait methods. + #[pin] + _pin: PhantomPinned, + } +} + +impl<'a, St: ?Sized> TryNext<'a, St> { + pub(super) fn new(stream: &'a mut St) -> Self { + Self { + inner: Next::new(stream), + _pin: PhantomPinned, + } + } +} + +impl<T, E, St: ?Sized + Stream<Item = Result<T, E>> + Unpin> Future for TryNext<'_, St> { + type Output = Result<Option<T>, E>; + + fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { + let me = self.project(); + me.inner.poll(cx).map(Option::transpose) + } +} |