| use crate::stream::{FuturesUnordered, StreamExt}; |
| use core::fmt; |
| use core::pin::Pin; |
| use core::num::NonZeroUsize; |
| use futures_core::future::{FusedFuture, Future}; |
| use futures_core::stream::Stream; |
| use futures_core::task::{Context, Poll}; |
| use pin_project::pin_project; |
| |
| /// Future for the [`for_each_concurrent`](super::StreamExt::for_each_concurrent) |
| /// method. |
| #[pin_project] |
| #[must_use = "futures do nothing unless you `.await` or poll them"] |
| pub struct ForEachConcurrent<St, Fut, F> { |
| #[pin] |
| stream: Option<St>, |
| f: F, |
| futures: FuturesUnordered<Fut>, |
| limit: Option<NonZeroUsize>, |
| } |
| |
| impl<St, Fut, F> fmt::Debug for ForEachConcurrent<St, Fut, F> |
| where |
| St: fmt::Debug, |
| Fut: fmt::Debug, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_struct("ForEachConcurrent") |
| .field("stream", &self.stream) |
| .field("futures", &self.futures) |
| .field("limit", &self.limit) |
| .finish() |
| } |
| } |
| |
| impl<St, Fut, F> ForEachConcurrent<St, Fut, F> |
| where St: Stream, |
| F: FnMut(St::Item) -> Fut, |
| Fut: Future<Output = ()>, |
| { |
| pub(super) fn new(stream: St, limit: Option<usize>, f: F) -> ForEachConcurrent<St, Fut, F> { |
| ForEachConcurrent { |
| stream: Some(stream), |
| // Note: `limit` = 0 gets ignored. |
| limit: limit.and_then(NonZeroUsize::new), |
| f, |
| futures: FuturesUnordered::new(), |
| } |
| } |
| } |
| |
| impl<St, Fut, F> FusedFuture for ForEachConcurrent<St, Fut, F> |
| where St: Stream, |
| F: FnMut(St::Item) -> Fut, |
| Fut: Future<Output = ()>, |
| { |
| fn is_terminated(&self) -> bool { |
| self.stream.is_none() && self.futures.is_empty() |
| } |
| } |
| |
| impl<St, Fut, F> Future for ForEachConcurrent<St, Fut, F> |
| where St: Stream, |
| F: FnMut(St::Item) -> Fut, |
| Fut: Future<Output = ()>, |
| { |
| type Output = (); |
| |
| fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> { |
| let mut this = self.project(); |
| loop { |
| let mut made_progress_this_iter = false; |
| |
| // Check if we've already created a number of futures greater than `limit` |
| if this.limit.map(|limit| limit.get() > this.futures.len()).unwrap_or(true) { |
| let mut stream_completed = false; |
| let elem = if let Some(stream) = this.stream.as_mut().as_pin_mut() { |
| match stream.poll_next(cx) { |
| Poll::Ready(Some(elem)) => { |
| made_progress_this_iter = true; |
| Some(elem) |
| }, |
| Poll::Ready(None) => { |
| stream_completed = true; |
| None |
| } |
| Poll::Pending => None, |
| } |
| } else { |
| None |
| }; |
| if stream_completed { |
| this.stream.set(None); |
| } |
| if let Some(elem) = elem { |
| this.futures.push((this.f)(elem)); |
| } |
| } |
| |
| match this.futures.poll_next_unpin(cx) { |
| Poll::Ready(Some(())) => made_progress_this_iter = true, |
| Poll::Ready(None) => { |
| if this.stream.is_none() { |
| return Poll::Ready(()) |
| } |
| }, |
| Poll::Pending => {} |
| } |
| |
| if !made_progress_this_iter { |
| return Poll::Pending; |
| } |
| } |
| } |
| } |