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use crate::Stream;
use core::fmt;
use core::pin::Pin;
use core::task::{Context, Poll};
use pin_project_lite::pin_project;
pin_project! {
/// Stream for the [`skip_while`](super::StreamExt::skip_while) method.
#[must_use = "streams do nothing unless polled"]
pub struct SkipWhile<St, F> {
#[pin]
stream: St,
predicate: Option<F>,
}
}
impl<St, F> fmt::Debug for SkipWhile<St, F>
where
St: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SkipWhile")
.field("stream", &self.stream)
.finish()
}
}
impl<St, F> SkipWhile<St, F> {
pub(super) fn new(stream: St, predicate: F) -> Self {
Self {
stream,
predicate: Some(predicate),
}
}
}
impl<St, F> Stream for SkipWhile<St, F>
where
St: Stream,
F: FnMut(&St::Item) -> bool,
{
type Item = St::Item;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
let mut this = self.project();
if let Some(predicate) = this.predicate {
loop {
match ready!(this.stream.as_mut().poll_next(cx)) {
Some(item) => {
if !(predicate)(&item) {
*this.predicate = None;
return Poll::Ready(Some(item));
}
}
None => return Poll::Ready(None),
}
}
} else {
this.stream.poll_next(cx)
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (lower, upper) = self.stream.size_hint();
if self.predicate.is_some() {
return (0, upper);
}
(lower, upper)
}
}