next.rs - Codebrowser

1	use futures_core::Stream;
2	use std::future::Future;
3	use std::pin::Pin;
4	use std::task::{Context, Poll};
5
6	// This is equivalent to the `futures::StreamExt::next` method.
7	// But we want to make this crate dependency as small as possible, so we define our `next` function.
8	#[doc(hidden)]
9	pub fn next<S>(stream: &mut S) -> impl Future<Output = Option<S::Item>> + '_
10	where
11	S: Stream + Unpin,
12	{
13	Next { stream }
14	}
15
16	#[derive(Debug)]
17	struct Next<'a, S> {
18	stream: &'a mut S,
19	}
20
21	impl<S> Unpin for Next<'_, S> where S: Unpin {}
22
23	impl<S> Future for Next<'_, S>
24	where
25	S: Stream + Unpin,
26	{
27	type Output = Option<S::Item>;
28
29	fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
30	Pin::new(&mut self.stream).poll_next(cx)
31	}
32	}
33