| use crate::stream::{Fuse, FuturesUnordered, StreamExt, IntoStream}; |
| use crate::future::{IntoFuture, TryFutureExt}; |
| 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::{pin_project, project}; |
| use core::pin::Pin; |
| |
| /// Stream for the |
| /// [`try_buffer_unordered`](super::TryStreamExt::try_buffer_unordered) method. |
| #[pin_project] |
| #[derive(Debug)] |
| #[must_use = "streams do nothing unless polled"] |
| pub struct TryBufferUnordered<St> |
| where St: TryStream |
| { |
| #[pin] |
| stream: Fuse<IntoStream<St>>, |
| in_progress_queue: FuturesUnordered<IntoFuture<St::Ok>>, |
| max: usize, |
| } |
| |
| impl<St> TryBufferUnordered<St> |
| where St: TryStream, |
| St::Ok: TryFuture, |
| { |
| pub(super) fn new(stream: St, n: usize) -> Self { |
| TryBufferUnordered { |
| stream: IntoStream::new(stream).fuse(), |
| in_progress_queue: FuturesUnordered::new(), |
| max: n, |
| } |
| } |
| |
| delegate_access_inner!(stream, St, (. .)); |
| } |
| |
| impl<St> Stream for TryBufferUnordered<St> |
| where St: TryStream, |
| St::Ok: TryFuture<Error = St::Error>, |
| { |
| type Item = Result<<St::Ok as TryFuture>::Ok, St::Error>; |
| |
| #[project] |
| fn poll_next( |
| self: Pin<&mut Self>, |
| cx: &mut Context<'_>, |
| ) -> Poll<Option<Self::Item>> { |
| #[project] |
| let TryBufferUnordered { mut stream, in_progress_queue, max } = 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 in_progress_queue.len() < *max { |
| match stream.as_mut().poll_next(cx)? { |
| Poll::Ready(Some(fut)) => 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 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 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 TryBufferUnordered<S> |
| where S: TryStream + Sink<Item, Error = E>, |
| S::Ok: TryFuture<Error = E>, |
| { |
| type Error = E; |
| |
| delegate_sink!(stream, Item); |
| } |