diff options
Diffstat (limited to 'vendor/futures-util/src/stream/try_stream/try_filter.rs')
-rw-r--r-- | vendor/futures-util/src/stream/try_stream/try_filter.rs | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/vendor/futures-util/src/stream/try_stream/try_filter.rs b/vendor/futures-util/src/stream/try_stream/try_filter.rs new file mode 100644 index 000000000..61e6105c3 --- /dev/null +++ b/vendor/futures-util/src/stream/try_stream/try_filter.rs @@ -0,0 +1,112 @@ +use core::fmt; +use core::pin::Pin; +use futures_core::future::Future; +use futures_core::ready; +use futures_core::stream::{FusedStream, Stream, TryStream}; +use futures_core::task::{Context, Poll}; +#[cfg(feature = "sink")] +use futures_sink::Sink; +use pin_project_lite::pin_project; + +pin_project! { + /// Stream for the [`try_filter`](super::TryStreamExt::try_filter) + /// method. + #[must_use = "streams do nothing unless polled"] + pub struct TryFilter<St, Fut, F> + where St: TryStream + { + #[pin] + stream: St, + f: F, + #[pin] + pending_fut: Option<Fut>, + pending_item: Option<St::Ok>, + } +} + +impl<St, Fut, F> fmt::Debug for TryFilter<St, Fut, F> +where + St: TryStream + fmt::Debug, + St::Ok: fmt::Debug, + Fut: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("TryFilter") + .field("stream", &self.stream) + .field("pending_fut", &self.pending_fut) + .field("pending_item", &self.pending_item) + .finish() + } +} + +impl<St, Fut, F> TryFilter<St, Fut, F> +where + St: TryStream, +{ + pub(super) fn new(stream: St, f: F) -> Self { + Self { stream, f, pending_fut: None, pending_item: None } + } + + delegate_access_inner!(stream, St, ()); +} + +impl<St, Fut, F> FusedStream for TryFilter<St, Fut, F> +where + St: TryStream + FusedStream, + F: FnMut(&St::Ok) -> Fut, + Fut: Future<Output = bool>, +{ + fn is_terminated(&self) -> bool { + self.pending_fut.is_none() && self.stream.is_terminated() + } +} + +impl<St, Fut, F> Stream for TryFilter<St, Fut, F> +where + St: TryStream, + Fut: Future<Output = bool>, + F: FnMut(&St::Ok) -> Fut, +{ + type Item = Result<St::Ok, St::Error>; + + fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { + let mut this = self.project(); + + Poll::Ready(loop { + if let Some(fut) = this.pending_fut.as_mut().as_pin_mut() { + let res = ready!(fut.poll(cx)); + this.pending_fut.set(None); + if res { + break this.pending_item.take().map(Ok); + } + *this.pending_item = None; + } else if let Some(item) = ready!(this.stream.as_mut().try_poll_next(cx)?) { + this.pending_fut.set(Some((this.f)(&item))); + *this.pending_item = Some(item); + } else { + break None; + } + }) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + let pending_len = if self.pending_fut.is_some() { 1 } else { 0 }; + let (_, upper) = self.stream.size_hint(); + let upper = match upper { + Some(x) => x.checked_add(pending_len), + None => None, + }; + (0, upper) // can't know a lower bound, due to the predicate + } +} + +// Forwarding impl of Sink from the underlying stream +#[cfg(feature = "sink")] +impl<S, Fut, F, Item, E> Sink<Item> for TryFilter<S, Fut, F> +where + S: TryStream + Sink<Item, Error = E>, +{ + type Error = E; + + delegate_sink!(stream, Item); +} |