| 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()) |
| } |
| } |