futures_util/stream/stream/
collect.rs

1use core::mem;
2use core::pin::Pin;
3use futures_core::future::{FusedFuture, Future};
4use futures_core::ready;
5use futures_core::stream::{FusedStream, Stream};
6use futures_core::task::{Context, Poll};
7use pin_project_lite::pin_project;
8
9pin_project! {
10    /// Future for the [`collect`](super::StreamExt::collect) method.
11    #[derive(Debug)]
12    #[must_use = "futures do nothing unless you `.await` or poll them"]
13    pub struct Collect<St, C> {
14        #[pin]
15        stream: St,
16        collection: C,
17    }
18}
19
20impl<St: Stream, C: Default> Collect<St, C> {
21    fn finish(self: Pin<&mut Self>) -> C {
22        mem::take(self.project().collection)
23    }
24
25    pub(super) fn new(stream: St) -> Self {
26        Self { stream, collection: Default::default() }
27    }
28}
29
30impl<St, C> FusedFuture for Collect<St, C>
31where
32    St: FusedStream,
33    C: Default + Extend<St::Item>,
34{
35    fn is_terminated(&self) -> bool {
36        self.stream.is_terminated()
37    }
38}
39
40impl<St, C> Future for Collect<St, C>
41where
42    St: Stream,
43    C: Default + Extend<St::Item>,
44{
45    type Output = C;
46
47    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<C> {
48        let mut this = self.as_mut().project();
49        loop {
50            match ready!(this.stream.as_mut().poll_next(cx)) {
51                Some(e) => this.collection.extend(Some(e)),
52                None => return Poll::Ready(self.finish()),
53            }
54        }
55    }
56}