diff options
Diffstat (limited to 'third_party/rust/tokio-stream/src/stream_ext/skip_while.rs')
-rw-r--r-- | third_party/rust/tokio-stream/src/stream_ext/skip_while.rs | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/third_party/rust/tokio-stream/src/stream_ext/skip_while.rs b/third_party/rust/tokio-stream/src/stream_ext/skip_while.rs new file mode 100644 index 0000000000..985a92666e --- /dev/null +++ b/third_party/rust/tokio-stream/src/stream_ext/skip_while.rs @@ -0,0 +1,73 @@ +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) + } +} |