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68 lines
1.7 KiB
Rust
68 lines
1.7 KiB
Rust
use std::future::Future;
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use std::pin::Pin;
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use std::time::Duration;
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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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use crate::utils::Timer;
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pin_project! {
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/// A stream that only yields one element once every `duration`.
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///
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/// This `struct` is created by the [`throttle`] method on [`Stream`]. See its
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/// documentation for more.
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///
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/// [`throttle`]: trait.Stream.html#method.throttle
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/// [`Stream`]: trait.Stream.html
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#[doc(hidden)]
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#[allow(missing_debug_implementations)]
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pub struct Throttle<S> {
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#[pin]
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stream: S,
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duration: Duration,
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#[pin]
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blocked: bool,
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#[pin]
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delay: Timer,
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}
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}
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impl<S: Stream> Throttle<S> {
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pub(super) fn new(stream: S, duration: Duration) -> Self {
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Self {
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stream,
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duration,
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blocked: false,
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delay: Timer::after(Duration::default()),
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}
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}
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}
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impl<S: Stream> Stream for Throttle<S> {
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type Item = S::Item;
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fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
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let mut this = self.project();
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if *this.blocked {
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let d = this.delay.as_mut();
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if d.poll(cx).is_ready() {
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*this.blocked = false;
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} else {
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return Poll::Pending;
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}
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}
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match this.stream.poll_next(cx) {
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Poll::Pending => Poll::Pending,
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Poll::Ready(None) => Poll::Ready(None),
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Poll::Ready(Some(v)) => {
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*this.blocked = true;
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let _ = std::mem::replace(&mut *this.delay, Timer::after(*this.duration));
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Poll::Ready(Some(v))
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}
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}
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}
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}
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