async_std/stream/stream/
filter.rs

1use core::pin::Pin;
2
3use pin_project_lite::pin_project;
4
5use crate::stream::Stream;
6use crate::task::{Context, Poll};
7
8pin_project! {
9    /// A stream to filter elements of another stream with a predicate.
10    ///
11    /// This `struct` is created by the [`filter`] method on [`Stream`]. See its
12    /// documentation for more.
13    ///
14    /// [`filter`]: trait.Stream.html#method.filter
15    /// [`Stream`]: trait.Stream.html
16    #[derive(Debug)]
17    pub struct Filter<S, P> {
18        #[pin]
19        stream: S,
20        predicate: P,
21    }
22}
23
24impl<S, P> Filter<S, P> {
25    pub(super) fn new(stream: S, predicate: P) -> Self {
26        Self {
27            stream,
28            predicate,
29        }
30    }
31}
32
33impl<S, P> Stream for Filter<S, P>
34where
35    S: Stream,
36    P: FnMut(&S::Item) -> bool,
37{
38    type Item = S::Item;
39
40    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
41        let this = self.project();
42        let next = futures_core::ready!(this.stream.poll_next(cx));
43
44        match next {
45            Some(v) if (this.predicate)(&v) => Poll::Ready(Some(v)),
46            Some(_) => {
47                cx.waker().wake_by_ref();
48                Poll::Pending
49            }
50            None => Poll::Ready(None),
51        }
52    }
53}
async_std/stream/stream/filter.rs

async_std/stream/stream/
filter.rs
