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