1 use crate::stream::Stream; 2 3 use core::fmt; 4 use core::pin::Pin; 5 use core::task::{Context, Poll}; 6 use pin_project_lite::pin_project; 7 8 pin_project! { 9 /// Stream for the [`skip_while`](super::StreamExt::skip_while) method. 10 #[must_use = "streams do nothing unless polled"] 11 pub struct SkipWhile<St, F> { 12 #[pin] 13 stream: St, 14 predicate: Option<F>, 15 } 16 } 17 18 impl<St, F> fmt::Debug for SkipWhile<St, F> 19 where 20 St: fmt::Debug, 21 { fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result22 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 23 f.debug_struct("SkipWhile") 24 .field("stream", &self.stream) 25 .finish() 26 } 27 } 28 29 impl<St, F> SkipWhile<St, F> { new(stream: St, predicate: F) -> Self30 pub(super) fn new(stream: St, predicate: F) -> Self { 31 Self { 32 stream, 33 predicate: Some(predicate), 34 } 35 } 36 } 37 38 impl<St, F> Stream for SkipWhile<St, F> 39 where 40 St: Stream, 41 F: FnMut(&St::Item) -> bool, 42 { 43 type Item = St::Item; 44 poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>45 fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { 46 let mut this = self.project(); 47 if let Some(predicate) = this.predicate { 48 loop { 49 match ready!(this.stream.as_mut().poll_next(cx)) { 50 Some(item) => { 51 if !(predicate)(&item) { 52 *this.predicate = None; 53 return Poll::Ready(Some(item)); 54 } 55 } 56 None => return Poll::Ready(None), 57 } 58 } 59 } else { 60 this.stream.poll_next(cx) 61 } 62 } 63 size_hint(&self) -> (usize, Option<usize>)64 fn size_hint(&self) -> (usize, Option<usize>) { 65 let (lower, upper) = self.stream.size_hint(); 66 67 if self.predicate.is_some() { 68 return (0, upper); 69 } 70 71 (lower, upper) 72 } 73 } 74