async_std/stream/stream/
inspect.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 that does something with each element of another stream.
10    ///
11    /// This `struct` is created by the [`inspect`] method on [`Stream`]. See its
12    /// documentation for more.
13    ///
14    /// [`inspect`]: trait.Stream.html#method.inspect
15    /// [`Stream`]: trait.Stream.html
16    #[derive(Debug)]
17    pub struct Inspect<S, F> {
18        #[pin]
19        stream: S,
20        f: F,
21    }
22}
23
24impl<S, F> Inspect<S, F> {
25    pub(super) fn new(stream: S, f: F) -> Self {
26        Self {
27            stream,
28            f,
29        }
30    }
31}
32
33impl<S, F> Stream for Inspect<S, F>
34where
35    S: Stream,
36    F: FnMut(&S::Item),
37{
38    type Item = S::Item;
39
40    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
41        let mut this = self.project();
42        let next = futures_core::ready!(this.stream.as_mut().poll_next(cx));
43
44        Poll::Ready(next.map(|x| {
45            (this.f)(&x);
46            x
47        }))
48    }
49}
async_std/stream/stream/inspect.rs

async_std/stream/stream/
inspect.rs
