diff options
Diffstat (limited to 'src/stream_ext/chain.rs')
-rw-r--r-- | src/stream_ext/chain.rs | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/src/stream_ext/chain.rs b/src/stream_ext/chain.rs new file mode 100644 index 0000000..bd64f33 --- /dev/null +++ b/src/stream_ext/chain.rs @@ -0,0 +1,50 @@ +use crate::stream_ext::Fuse; +use crate::Stream; + +use core::pin::Pin; +use core::task::{Context, Poll}; +use pin_project_lite::pin_project; + +pin_project! { + /// Stream returned by the [`chain`](super::StreamExt::chain) method. + pub struct Chain<T, U> { + #[pin] + a: Fuse<T>, + #[pin] + b: U, + } +} + +impl<T, U> Chain<T, U> { + pub(super) fn new(a: T, b: U) -> Chain<T, U> + where + T: Stream, + U: Stream, + { + Chain { a: Fuse::new(a), b } + } +} + +impl<T, U> Stream for Chain<T, U> +where + T: Stream, + U: Stream<Item = T::Item>, +{ + type Item = T::Item; + + fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> { + use Poll::Ready; + + let me = self.project(); + + if let Some(v) = ready!(me.a.poll_next(cx)) { + return Ready(Some(v)); + } + + me.b.poll_next(cx) + } + + fn size_hint(&self) -> (usize, Option<usize>) { + super::merge_size_hints(self.a.size_hint(), self.b.size_hint()) + } +} |