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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_lite::pin_project;
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) -> Self {
Self {
stream: Some(stream),
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>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
let mut made_progress_this_iter = false;
if this.limit.map(|limit| limit.get() > this.futures.len()).unwrap_or(true) {
let poll_res = match this.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) => {
this.stream.set(None);
None
}
Poll::Pending => None,
Poll::Ready(Some(Err(e))) => {
this.stream.set(None);
drop(mem::replace(this.futures, FuturesUnordered::new()));
return Poll::Ready(Err(e));
}
};
if let Some(elem) = elem {
this.futures.push((this.f)(elem));
}
}
match this.futures.poll_next_unpin(cx) {
Poll::Ready(Some(Ok(()))) => made_progress_this_iter = true,
Poll::Ready(None) => {
if this.stream.is_none() {
return Poll::Ready(Ok(()))
}
},
Poll::Pending => {}
Poll::Ready(Some(Err(e))) => {
this.stream.set(None);
drop(mem::replace(this.futures, FuturesUnordered::new()));
return Poll::Ready(Err(e));
}
}
if !made_progress_this_iter {
return Poll::Pending;
}
}
}
}