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)]
next<S>(stream: &mut S) -> impl Future<Output = Option<S::Item>> + '_ where S: Stream + Unpin,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
poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>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