blob: c6032427e95179855755c7cf616e30543fbf33fe [file] [log] [blame]
use crate::stream::{Fuse, FuturesUnordered, StreamExt};
use crate::try_future::{IntoFuture, TryFutureExt};
use crate::try_stream::IntoStream;
use futures_core::future::TryFuture;
use futures_core::stream::{Stream, TryStream};
use futures_core::task::{self, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
use std::marker::Unpin;
use std::mem::PinMut;
/// A stream returned by 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
{
stream: Fuse<IntoStream<St>>,
in_progress_queue: FuturesUnordered<IntoFuture<St::Ok>>,
max: usize,
}
impl<St> Unpin for TryBufferUnordered<St>
where St: TryStream + Unpin
{}
impl<St> TryBufferUnordered<St>
where St: TryStream,
St::Ok: TryFuture,
{
unsafe_pinned!(stream: Fuse<IntoStream<St>>);
unsafe_unpinned!(in_progress_queue: FuturesUnordered<IntoFuture<St::Ok>>);
pub(super) fn new(stream: St, n: usize) -> Self {
TryBufferUnordered {
stream: IntoStream::new(stream).fuse(),
in_progress_queue: FuturesUnordered::new(),
max: n,
}
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &St {
self.stream.get_ref().get_ref()
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut St {
self.stream.get_mut().get_mut()
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> St {
self.stream.into_inner().into_inner()
}
}
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(
mut self: PinMut<Self>,
cx: &mut task::Context,
) -> Poll<Option<Self::Item>> {
// First up, try to spawn off as many futures as possible by filling up
// our slab of futures. Propagate errors from the stream immediately.
while self.in_progress_queue.len() < self.max {
match self.stream().poll_next(cx) {
Poll::Ready(Some(Ok(fut))) => self.in_progress_queue().push(fut.into_future()),
Poll::Ready(Some(Err(e))) => return Poll::Ready(Some(Err(e))),
Poll::Ready(None) | Poll::Pending => break,
}
}
// Attempt to pull the next value from the in_progress_queue
match PinMut::new(self.in_progress_queue()).poll_next(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 self.stream.is_done() {
Poll::Ready(None)
} else {
Poll::Pending
}
}
}