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Diffstat (limited to '')
-rw-r--r-- | vendor/futures-util/src/stream/try_stream/try_buffered.rs | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/vendor/futures-util/src/stream/try_stream/try_buffered.rs b/vendor/futures-util/src/stream/try_stream/try_buffered.rs new file mode 100644 index 000000000..45bd3f8c7 --- /dev/null +++ b/vendor/futures-util/src/stream/try_stream/try_buffered.rs @@ -0,0 +1,87 @@ +use crate::future::{IntoFuture, TryFutureExt}; +use crate::stream::{Fuse, FuturesOrdered, IntoStream, StreamExt}; +use core::pin::Pin; +use futures_core::future::TryFuture; +use futures_core::stream::{Stream, TryStream}; +use futures_core::task::{Context, Poll}; +#[cfg(feature = "sink")] +use futures_sink::Sink; +use pin_project_lite::pin_project; + +pin_project! { + /// Stream for the [`try_buffered`](super::TryStreamExt::try_buffered) method. + #[derive(Debug)] + #[must_use = "streams do nothing unless polled"] + pub struct TryBuffered<St> + where + St: TryStream, + St::Ok: TryFuture, + { + #[pin] + stream: Fuse<IntoStream<St>>, + in_progress_queue: FuturesOrdered<IntoFuture<St::Ok>>, + max: usize, + } +} + +impl<St> TryBuffered<St> +where + St: TryStream, + St::Ok: TryFuture, +{ + pub(super) fn new(stream: St, n: usize) -> Self { + Self { + stream: IntoStream::new(stream).fuse(), + in_progress_queue: FuturesOrdered::new(), + max: n, + } + } + + delegate_access_inner!(stream, St, (. .)); +} + +impl<St> Stream for TryBuffered<St> +where + St: TryStream, + St::Ok: TryFuture<Error = St::Error>, +{ + type Item = Result<<St::Ok as TryFuture>::Ok, St::Error>; + + fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { + let mut this = self.project(); + + // First up, try to spawn off as many futures as possible by filling up + // our queue of futures. Propagate errors from the stream immediately. + while this.in_progress_queue.len() < *this.max { + match this.stream.as_mut().poll_next(cx)? { + Poll::Ready(Some(fut)) => this.in_progress_queue.push(fut.into_future()), + Poll::Ready(None) | Poll::Pending => break, + } + } + + // Attempt to pull the next value from the in_progress_queue + match this.in_progress_queue.poll_next_unpin(cx) { + x @ Poll::Pending | x @ Poll::Ready(Some(_)) => return x, + Poll::Ready(None) => {} + } + + // If more values are still coming from the stream, we're not done yet + if this.stream.is_done() { + Poll::Ready(None) + } else { + Poll::Pending + } + } +} + +// Forwarding impl of Sink from the underlying stream +#[cfg(feature = "sink")] +impl<S, Item, E> Sink<Item> for TryBuffered<S> +where + S: TryStream + Sink<Item, Error = E>, + S::Ok: TryFuture<Error = E>, +{ + type Error = E; + + delegate_sink!(stream, Item); +} |