tokio_stream/stream_ext/
map.rs

1use crate::Stream;
2
3use core::fmt;
4use core::pin::Pin;
5use core::task::{Context, Poll};
6use futures_core::FusedStream;
7use pin_project_lite::pin_project;
8
9pin_project! {
10    /// Stream for the [`map`](super::StreamExt::map) method.
11    #[must_use = "streams do nothing unless polled"]
12    pub struct Map<St, F> {
13        #[pin]
14        stream: St,
15        f: F,
16    }
17}
18
19impl<St, F> fmt::Debug for Map<St, F>
20where
21    St: fmt::Debug,
22{
23    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
24        f.debug_struct("Map").field("stream", &self.stream).finish()
25    }
26}
27
28impl<St, F> Map<St, F> {
29    pub(super) fn new(stream: St, f: F) -> Self {
30        Map { stream, f }
31    }
32}
33
34impl<St, F, T> Stream for Map<St, F>
35where
36    St: Stream,
37    F: FnMut(St::Item) -> T,
38{
39    type Item = T;
40
41    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
42        self.as_mut()
43            .project()
44            .stream
45            .poll_next(cx)
46            .map(|opt| opt.map(|x| (self.as_mut().project().f)(x)))
47    }
48
49    fn size_hint(&self) -> (usize, Option<usize>) {
50        self.stream.size_hint()
51    }
52}
53
54impl<St, F, T> FusedStream for Map<St, F>
55where
56    St: FusedStream,
57    F: FnMut(St::Item) -> T,
58{
59    fn is_terminated(&self) -> bool {
60        self.stream.is_terminated()
61    }
62}
tokio_stream/stream_ext/map.rs

tokio_stream/stream_ext/
map.rs
