vendor/futures-util/src/stream/stream/collect.rs

   1 use core::mem;
   2 use core::pin::Pin;
   3 use futures_core::future::{FusedFuture, Future};
   4 use futures_core::ready;
   5 use futures_core::stream::{FusedStream, Stream};
   6 use futures_core::task::{Context, Poll};
   7 use pin_project_lite::pin_project;
   8
   9 pin_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
  20 impl<St: Stream, C: Default> Collect<St, C> {
  21     fn finish(self: Pin<&mut Self>) -> C {
  22         mem::replace(self.project().collection, Default::default())
  23     }
  24
  25     pub(super) fn new(stream: St) -> Self {
  26         Self { stream, collection: Default::default() }
  27     }
  28 }
  29
  30 impl<St, C> FusedFuture for Collect<St, C>
  31 where
  32     St: FusedStream,
  33     C: Default + Extend<St::Item>,
  34 {
  35     fn is_terminated(&self) -> bool {
  36         self.stream.is_terminated()
  37     }
  38 }
  39
  40 impl<St, C> Future for Collect<St, C>
  41 where
  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 }