| use core::pin::Pin; |
| use futures_core::future::{Future, FusedFuture}; |
| use futures_core::stream::{Stream, FusedStream}; |
| use futures_core::task::{Context, Poll}; |
| use pin_project::pin_project; |
| |
| /// Future for the [`concat`](super::StreamExt::concat) method. |
| #[pin_project] |
| #[derive(Debug)] |
| #[must_use = "futures do nothing unless you `.await` or poll them"] |
| pub struct Concat<St: Stream> { |
| #[pin] |
| stream: St, |
| accum: Option<St::Item>, |
| } |
| |
| impl<St> Concat<St> |
| where St: Stream, |
| St::Item: Extend<<St::Item as IntoIterator>::Item> + |
| IntoIterator + Default, |
| { |
| pub(super) fn new(stream: St) -> Concat<St> { |
| Concat { |
| stream, |
| accum: None, |
| } |
| } |
| } |
| |
| impl<St> Future for Concat<St> |
| where St: Stream, |
| St::Item: Extend<<St::Item as IntoIterator>::Item> + |
| IntoIterator + Default, |
| { |
| type Output = St::Item; |
| |
| fn poll( |
| self: Pin<&mut Self>, cx: &mut Context<'_> |
| ) -> Poll<Self::Output> { |
| let mut this = self.project(); |
| |
| loop { |
| match ready!(this.stream.as_mut().poll_next(cx)) { |
| None => { |
| return Poll::Ready(this.accum.take().unwrap_or_default()) |
| } |
| Some(e) => { |
| if let Some(a) = this.accum { |
| a.extend(e) |
| } else { |
| *this.accum = Some(e) |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| impl<St> FusedFuture for Concat<St> |
| where St: FusedStream, |
| St::Item: Extend<<St::Item as IntoIterator>::Item> + |
| IntoIterator + Default, |
| { |
| fn is_terminated(&self) -> bool { |
| self.accum.is_none() && self.stream.is_terminated() |
| } |
| } |