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54 lines
1.2 KiB
54 lines
1.2 KiB
use super::*;
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use pin_project::pin_project;
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use std::{
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pin::Pin,
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task::{Context, Poll},
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};
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#[pin_project]
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#[derive(Debug, Clone)]
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pub struct MaybeStream<I,T>(#[pin] Option<I>)
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where I: Stream<Item=T>;
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pub trait OptionStreamExt<I, T>: Sized
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where I: Stream<Item=T>
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{
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/// Map this `Option<Stream>` into a stream that will yield the items of the stream if it is present.
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fn map_into_stream(self) -> MaybeStream<I,T>;
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}
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impl<I: Stream<Item=T>, T> Stream for MaybeStream<I,T>
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{
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type Item = T;
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fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
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match self.project().0.as_pin_mut()
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{
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Some(i) => i.poll_next(cx),
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_ => Poll::Ready(None),
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}
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}
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fn size_hint(&self) -> (usize, Option<usize>) {
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match &self.0 {
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Some(i) => i.size_hint(),
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None => (0, Some(0)),
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}
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}
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}
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impl<E, T, I: Stream<Item=T>> OptionStreamExt<I, T> for Result<I, E>
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where I: Stream<Item = T>
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{
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#[inline] fn map_into_stream(self) -> MaybeStream<I, T> {
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MaybeStream(self.ok())
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}
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}
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impl<T, I: Stream<Item=T>> OptionStreamExt<I, T> for Option<I>
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where I: Stream<Item = T>
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{
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#[inline] fn map_into_stream(self) -> MaybeStream<I, T> {
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MaybeStream(self)
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}
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}
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