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`](super::StreamExt::skip) method. 10 #[must_use = "streams do nothing unless polled"] 11 pub struct Skip<St> { 12 #[pin] 13 stream: St, 14 remaining: usize, 15 } 16 } 17 18 impl<St> fmt::Debug for Skip<St> 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("Skip") 24 .field("stream", &self.stream) 25 .finish() 26 } 27 } 28 29 impl<St> Skip<St> { new(stream: St, remaining: usize) -> Self30 pub(super) fn new(stream: St, remaining: usize) -> Self { 31 Self { stream, remaining } 32 } 33 } 34 35 impl<St> Stream for Skip<St> 36 where 37 St: Stream, 38 { 39 type Item = St::Item; 40 poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>41 fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> { 42 loop { 43 match ready!(self.as_mut().project().stream.poll_next(cx)) { 44 Some(e) => { 45 if self.remaining == 0 { 46 return Poll::Ready(Some(e)); 47 } 48 *self.as_mut().project().remaining -= 1; 49 } 50 None => return Poll::Ready(None), 51 } 52 } 53 } 54 size_hint(&self) -> (usize, Option<usize>)55 fn size_hint(&self) -> (usize, Option<usize>) { 56 let (lower, upper) = self.stream.size_hint(); 57 58 let lower = lower.saturating_sub(self.remaining); 59 let upper = upper.map(|x| x.saturating_sub(self.remaining)); 60 61 (lower, upper) 62 } 63 } 64