| use crate::stream::{Fuse, FuturesUnordered}; |
| use futures_core::future::Future; |
| use futures_core::stream::{Stream, FusedStream}; |
| use futures_core::task::{LocalWaker, Poll}; |
| use futures_sink::Sink; |
| use pin_utils::{unsafe_pinned, unsafe_unpinned}; |
| use std::fmt; |
| use std::marker::Unpin; |
| use std::pin::Pin; |
| |
| /// An adaptor for a stream of futures to execute the futures concurrently, if |
| /// possible, delivering results as they become available. |
| /// |
| /// This adaptor will buffer up a list of pending futures, and then return their |
| /// results in the order that they complete. This is created by the |
| /// `Stream::buffer_unordered` method. |
| #[must_use = "streams do nothing unless polled"] |
| pub struct BufferUnordered<St> |
| where |
| St: Stream, |
| St::Item: Future, |
| { |
| stream: Fuse<St>, |
| in_progress_queue: FuturesUnordered<St::Item>, |
| max: usize, |
| } |
| |
| impl<St> Unpin for BufferUnordered<St> |
| where |
| St: Stream + Unpin, |
| St::Item: Future, |
| {} |
| |
| impl<St> fmt::Debug for BufferUnordered<St> |
| where |
| St: Stream + fmt::Debug, |
| St::Item: Future, |
| { |
| fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { |
| fmt.debug_struct("BufferUnordered") |
| .field("stream", &self.stream) |
| .field("in_progress_queue", &self.in_progress_queue) |
| .field("max", &self.max) |
| .finish() |
| } |
| } |
| |
| impl<St> BufferUnordered<St> |
| where |
| St: Stream, |
| St::Item: Future, |
| { |
| unsafe_pinned!(stream: Fuse<St>); |
| unsafe_unpinned!(in_progress_queue: FuturesUnordered<St::Item>); |
| |
| pub(super) fn new(stream: St, n: usize) -> BufferUnordered<St> |
| where |
| St: Stream, |
| St::Item: Future, |
| { |
| BufferUnordered { |
| stream: super::Fuse::new(stream), |
| 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() |
| } |
| |
| /// 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() |
| } |
| |
| /// Acquires a pinned 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. |
| #[allow(clippy::needless_lifetimes)] // https://github.com/rust-lang/rust/issues/52675 |
| 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()) } |
| } |
| |
| /// 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() |
| } |
| } |
| |
| impl<St> Stream for BufferUnordered<St> |
| where |
| St: Stream, |
| St::Item: Future, |
| { |
| type Item = <St::Item as Future>::Output; |
| |
| fn poll_next( |
| mut self: Pin<&mut Self>, |
| lw: &LocalWaker, |
| ) -> Poll<Option<Self::Item>> { |
| // First up, try to spawn off as many futures as possible by filling up |
| // our slab of futures. |
| while self.in_progress_queue.len() < self.max { |
| match self.as_mut().stream().poll_next(lw) { |
| Poll::Ready(Some(fut)) => self.as_mut().in_progress_queue().push(fut), |
| Poll::Ready(None) | Poll::Pending => break, |
| } |
| } |
| |
| // Attempt to pull the next value from the in_progress_queue |
| match Pin::new(self.as_mut().in_progress_queue()).poll_next(lw) { |
| 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 |
| } |
| } |
| } |
| |
| impl<St> FusedStream for BufferUnordered<St> |
| where |
| St: Stream, |
| St::Item: Future, |
| { |
| fn is_terminated(&self) -> bool { |
| self.in_progress_queue.is_terminated() && self.stream.is_terminated() |
| } |
| } |
| |
| // Forwarding impl of Sink from the underlying stream |
| impl<S> Sink for BufferUnordered<S> |
| where |
| S: Stream + Sink, |
| S::Item: Future, |
| { |
| type SinkItem = S::SinkItem; |
| type SinkError = S::SinkError; |
| |
| delegate_sink!(stream); |
| } |