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ec23632f3e
* Cleanup: replace cfg-if with our macros * Prefix macros with cfg_ * Remove #[macro_export] from internal macros
24 lines
836 B
Rust
24 lines
836 B
Rust
use crate::stream::Stream;
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use std::pin::Pin;
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use std::task::{Context, Poll};
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/// A stream able to yield elements from both ends.
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///
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/// Something that implements `DoubleEndedStream` has one extra capability
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/// over something that implements [`Stream`]: the ability to also take
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/// `Item`s from the back, as well as the front.
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///
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/// [`Stream`]: trait.Stream.html
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#[cfg(feature = "unstable")]
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#[cfg_attr(feature = "docs", doc(cfg(unstable)))]
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pub trait DoubleEndedStream: Stream {
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/// Removes and returns an element from the end of the stream.
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///
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/// Returns `None` when there are no more elements.
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///
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/// The [trait-level] docs contain more details.
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///
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/// [trait-level]: trait.DoubleEndedStream.html
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fn poll_next_back(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>;
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}
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