forked from mirror/async-std
45 lines
1 KiB
Rust
45 lines
1 KiB
Rust
use std::marker::PhantomData;
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use std::pin::Pin;
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use std::task::{Context, Poll};
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use crate::stream::{Stream, DoubleEndedStream, ExactSizeStream, FusedStream};
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/// A stream that never returns any items.
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///
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/// This stream is created by the [`pending`] function. See its
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/// documentation for more.
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///
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/// [`pending`]: fn.pending.html
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#[derive(Debug)]
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pub struct Pending<T> {
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_marker: PhantomData<T>
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}
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/// Creates a stream that never returns any items.
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///
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/// The returned stream will always return `Pending` when polled.
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pub fn pending<T>() -> Pending<T> {
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Pending { _marker: PhantomData }
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}
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impl<T> Stream for Pending<T> {
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type Item = T;
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fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<T>> {
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Poll::Pending
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}
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}
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impl<T> DoubleEndedStream for Pending<T> {
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fn poll_next_back(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<T>> {
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Poll::Pending
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}
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}
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impl<T> FusedStream for Pending<T> {}
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impl<T> ExactSizeStream for Pending<T> {
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fn len(&self) -> usize {
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0
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}
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}
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