forked from mirror/async-std
52 lines
1.2 KiB
Rust
52 lines
1.2 KiB
Rust
use std::marker::PhantomData;
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use std::pin::Pin;
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use pin_project_lite::pin_project;
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use crate::stream::Stream;
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use crate::task::{Context, Poll};
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pin_project! {
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/// A stream that does something with each element of another stream.
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///
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/// This `struct` is created by the [`inspect`] method on [`Stream`]. See its
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/// documentation for more.
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///
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/// [`inspect`]: trait.Stream.html#method.inspect
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/// [`Stream`]: trait.Stream.html
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#[derive(Debug)]
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pub struct Inspect<S, F, T> {
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#[pin]
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stream: S,
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f: F,
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__t: PhantomData<T>,
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}
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}
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impl<S, F, T> Inspect<S, F, T> {
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pub(super) fn new(stream: S, f: F) -> Self {
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Inspect {
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stream,
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f,
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__t: PhantomData,
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}
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}
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}
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impl<S, F> Stream for Inspect<S, F, S::Item>
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where
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S: Stream,
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F: FnMut(&S::Item),
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{
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type Item = S::Item;
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fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
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let mut this = self.project();
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let next = futures_core::ready!(this.stream.as_mut().poll_next(cx));
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Poll::Ready(next.and_then(|x| {
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(this.f)(&x);
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Some(x)
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}))
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}
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}
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