63 lines
1.5 KiB
Rust
63 lines
1.5 KiB
Rust
use crate::Stream;
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use core::fmt;
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use core::pin::Pin;
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use core::task::{Context, Poll};
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use pin_project_lite::pin_project;
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pin_project! {
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/// Stream for the [`skip`](super::StreamExt::skip) method.
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#[must_use = "streams do nothing unless polled"]
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pub struct Skip<St> {
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#[pin]
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stream: St,
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remaining: usize,
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}
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}
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impl<St> fmt::Debug for Skip<St>
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where
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St: fmt::Debug,
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{
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("Skip")
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.field("stream", &self.stream)
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.finish()
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}
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}
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impl<St> Skip<St> {
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pub(super) fn new(stream: St, remaining: usize) -> Self {
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Self { stream, remaining }
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}
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}
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impl<St> Stream for Skip<St>
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where
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St: Stream,
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{
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type Item = St::Item;
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fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
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loop {
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match ready!(self.as_mut().project().stream.poll_next(cx)) {
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Some(e) => {
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if self.remaining == 0 {
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return Poll::Ready(Some(e));
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}
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*self.as_mut().project().remaining -= 1;
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}
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None => return Poll::Ready(None),
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}
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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let (lower, upper) = self.stream.size_hint();
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let lower = lower.saturating_sub(self.remaining);
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let upper = upper.map(|x| x.saturating_sub(self.remaining));
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(lower, upper)
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}
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}
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