135 lines
3.5 KiB
Rust
135 lines
3.5 KiB
Rust
use core::fmt;
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use core::marker::PhantomData;
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use core::pin::Pin;
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use futures_core::future::Future;
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use futures_core::ready;
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use futures_core::stream::Stream;
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use futures_core::task::{Context, Poll};
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use futures_sink::Sink;
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use pin_project_lite::pin_project;
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pin_project! {
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/// Sink for the [`with`](super::SinkExt::with) method.
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#[must_use = "sinks do nothing unless polled"]
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pub struct With<Si, Item, U, Fut, F> {
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#[pin]
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sink: Si,
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f: F,
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#[pin]
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state: Option<Fut>,
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_phantom: PhantomData<fn(U) -> Item>,
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}
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}
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impl<Si, Item, U, Fut, F> fmt::Debug for With<Si, Item, U, Fut, F>
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where
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Si: fmt::Debug,
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Fut: fmt::Debug,
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{
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("With").field("sink", &self.sink).field("state", &self.state).finish()
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}
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}
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impl<Si, Item, U, Fut, F> With<Si, Item, U, Fut, F>
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where
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Si: Sink<Item>,
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F: FnMut(U) -> Fut,
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Fut: Future,
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{
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pub(super) fn new<E>(sink: Si, f: F) -> Self
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where
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Fut: Future<Output = Result<Item, E>>,
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E: From<Si::Error>,
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{
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Self { state: None, sink, f, _phantom: PhantomData }
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}
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}
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impl<Si, Item, U, Fut, F> Clone for With<Si, Item, U, Fut, F>
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where
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Si: Clone,
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F: Clone,
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Fut: Clone,
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{
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fn clone(&self) -> Self {
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Self {
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state: self.state.clone(),
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sink: self.sink.clone(),
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f: self.f.clone(),
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_phantom: PhantomData,
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}
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}
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}
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// Forwarding impl of Stream from the underlying sink
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impl<S, Item, U, Fut, F> Stream for With<S, Item, U, Fut, F>
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where
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S: Stream + Sink<Item>,
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F: FnMut(U) -> Fut,
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Fut: Future,
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{
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type Item = S::Item;
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delegate_stream!(sink);
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}
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impl<Si, Item, U, Fut, F, E> With<Si, Item, U, Fut, F>
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where
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Si: Sink<Item>,
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F: FnMut(U) -> Fut,
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Fut: Future<Output = Result<Item, E>>,
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E: From<Si::Error>,
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{
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delegate_access_inner!(sink, Si, ());
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/// Completes the processing of previous item if any.
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), E>> {
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let mut this = self.project();
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let item = match this.state.as_mut().as_pin_mut() {
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None => return Poll::Ready(Ok(())),
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Some(fut) => ready!(fut.poll(cx))?,
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};
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this.state.set(None);
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this.sink.start_send(item)?;
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Poll::Ready(Ok(()))
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}
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}
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impl<Si, Item, U, Fut, F, E> Sink<U> for With<Si, Item, U, Fut, F>
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where
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Si: Sink<Item>,
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F: FnMut(U) -> Fut,
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Fut: Future<Output = Result<Item, E>>,
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E: From<Si::Error>,
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{
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type Error = E;
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fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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ready!(self.as_mut().poll(cx))?;
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ready!(self.project().sink.poll_ready(cx)?);
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Poll::Ready(Ok(()))
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}
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fn start_send(self: Pin<&mut Self>, item: U) -> Result<(), Self::Error> {
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let mut this = self.project();
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assert!(this.state.is_none());
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this.state.set(Some((this.f)(item)));
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Ok(())
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}
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fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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ready!(self.as_mut().poll(cx))?;
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ready!(self.project().sink.poll_flush(cx)?);
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Poll::Ready(Ok(()))
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}
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fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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ready!(self.as_mut().poll(cx))?;
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ready!(self.project().sink.poll_close(cx)?);
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Poll::Ready(Ok(()))
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}
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}
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