use core::mem;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future};
use futures_core::ready;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Collect<St, C> {
#[pin]
stream: St,
collection: C,
}
}
impl<St: Stream, C: Default> Collect<St, C> {
fn finish(self: Pin<&mut Self>) -> C {
mem::take(self.project().collection)
}
pub(super) fn new(stream: St) -> Self {
Self { stream, collection: Default::default() }
}
}
impl<St, C> FusedFuture for Collect<St, C>
where
St: FusedStream,
C: Default + Extend<St::Item>,
{
fn is_terminated(&self) -> bool {
self.stream.is_terminated()
}
}
impl<St, C> Future for Collect<St, C>
where
St: Stream,
C: Default + Extend<St::Item>,
{
type Output = C;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<C> {
let mut this = self.as_mut().project();
loop {
match ready!(this.stream.as_mut().poll_next(cx)) {
Some(e) => this.collection.extend(Some(e)),
None => return Poll::Ready(self.finish()),
}
}
}
}