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use crate::stream::{Fuse, FuturesOrdered};
use futures_core::future::Future;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
use core::fmt;
use core::pin::Pin;
#[must_use = "streams do nothing unless polled"]
pub struct Buffered<St: Stream>
where
St: Stream,
St::Item: Future,
{
stream: Fuse<St>,
in_progress_queue: FuturesOrdered<St::Item>,
max: usize,
}
impl<St> Unpin for Buffered<St>
where
St: Stream + Unpin,
St::Item: Future,
{}
impl<St> fmt::Debug for Buffered<St>
where
St: Stream + fmt::Debug,
St::Item: Future,
{
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("Buffered")
.field("stream", &self.stream)
.field("in_progress_queue", &self.in_progress_queue)
.field("max", &self.max)
.finish()
}
}
impl<St> Buffered<St>
where
St: Stream,
St::Item: Future,
{
unsafe_pinned!(stream: Fuse<St>);
unsafe_unpinned!(in_progress_queue: FuturesOrdered<St::Item>);
pub(super) fn new(stream: St, n: usize) -> Buffered<St> {
Buffered {
stream: super::Fuse::new(stream),
in_progress_queue: FuturesOrdered::new(),
max: n,
}
}
pub fn get_ref(&self) -> &St {
self.stream.get_ref()
}
pub fn get_mut(&mut self) -> &mut St {
self.stream.get_mut()
}
#[allow(clippy::needless_lifetimes)]
pub fn get_pin_mut<'a>(self: Pin<&'a mut Self>) -> Pin<&'a mut St> {
unsafe { Pin::map_unchecked_mut(self, |x| x.get_mut()) }
}
pub fn into_inner(self) -> St {
self.stream.into_inner()
}
}
impl<St> Stream for Buffered<St>
where
St: Stream,
St::Item: Future,
{
type Item = <St::Item as Future>::Output;
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
while self.in_progress_queue.len() < self.max {
match self.as_mut().stream().poll_next(cx) {
Poll::Ready(Some(fut)) => self.as_mut().in_progress_queue().push(fut),
Poll::Ready(None) | Poll::Pending => break,
}
}
let res = Pin::new(self.as_mut().in_progress_queue()).poll_next(cx);
if let Some(val) = ready!(res) {
return Poll::Ready(Some(val))
}
if self.stream.is_done() {
Poll::Ready(None)
} else {
Poll::Pending
}
}
}
impl<S, Item> Sink<Item> for Buffered<S>
where
S: Stream + Sink<Item>,
S::Item: Future,
{
type SinkError = S::SinkError;
delegate_sink!(stream, Item);
}