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use core::pin::Pin;
use futures_core::stream::Stream;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_utils::{unsafe_pinned, unsafe_unpinned};
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Take<St> {
stream: St,
remaining: u64,
}
impl<St: Unpin> Unpin for Take<St> {}
impl<St: Stream> Take<St> {
unsafe_pinned!(stream: St);
unsafe_unpinned!(remaining: u64);
pub(super) fn new(stream: St, n: u64) -> Take<St> {
Take {
stream,
remaining: n,
}
}
pub fn get_ref(&self) -> &St {
&self.stream
}
pub fn get_mut(&mut self) -> &mut St {
&mut self.stream
}
pub fn into_inner(self) -> St {
self.stream
}
}
impl<St> Stream for Take<St>
where St: Stream,
{
type Item = St::Item;
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<St::Item>> {
if self.remaining == 0 {
Poll::Ready(None)
} else {
let next = ready!(self.as_mut().stream().poll_next(cx));
match next {
Some(_) => *self.as_mut().remaining() -= 1,
None => *self.as_mut().remaining() = 0,
}
Poll::Ready(next)
}
}
}
impl<S, Item> Sink<Item> for Take<S>
where S: Stream + Sink<Item>,
{
type SinkError = S::SinkError;
delegate_sink!(stream, Item);
}