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use crate::future::{IntoFuture, TryFutureExt};
use crate::stream::{Fuse, FuturesUnordered, 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_buffer_unordered`](super::TryStreamExt::try_buffer_unordered) method.
#[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 {
Self {
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>;
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 TryBufferUnordered<S>
where
S: TryStream + Sink<Item, Error = E>,
S::Ok: TryFuture<Error = E>,
{
type Error = E;
delegate_sink!(stream, Item);
}