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Contents?: true
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Versions: 25
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Stored size: 1.94 KB
Contents
use core::cmp;
use core::pin::Pin;
use futures_core::ready;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_project_lite::pin_project;
pin_project! {
/// Stream for the [`take`](super::StreamExt::take) method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Take<St> {
#[pin]
stream: St,
remaining: usize,
}
}
impl<St: Stream> Take<St> {
pub(super) fn new(stream: St, n: usize) -> Self {
Self { stream, remaining: n }
}
delegate_access_inner!(stream, St, ());
}
impl<St> Stream for Take<St>
where
St: Stream,
{
type Item = St::Item;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<St::Item>> {
if self.remaining == 0 {
Poll::Ready(None)
} else {
let this = self.project();
let next = ready!(this.stream.poll_next(cx));
if next.is_some() {
*this.remaining -= 1;
} else {
*this.remaining = 0;
}
Poll::Ready(next)
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
if self.remaining == 0 {
return (0, Some(0));
}
let (lower, upper) = self.stream.size_hint();
let lower = cmp::min(lower, self.remaining);
let upper = match upper {
Some(x) if x < self.remaining => Some(x),
_ => Some(self.remaining),
};
(lower, upper)
}
}
impl<St> FusedStream for Take<St>
where
St: FusedStream,
{
fn is_terminated(&self) -> bool {
self.remaining == 0 || self.stream.is_terminated()
}
}
// Forwarding impl of Sink from the underlying stream
#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for Take<S>
where
S: Stream + Sink<Item>,
{
type Error = S::Error;
delegate_sink!(stream, Item);
}
Version data entries
25 entries across 25 versions & 1 rubygems