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send_all.rs
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send_all.rs
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use crate::stream::{Fuse, StreamExt};
use core::fmt;
use core::pin::Pin;
use futures_core::future::Future;
use futures_core::ready;
use futures_core::stream::{Stream, TryStream};
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_project_lite::pin_project;
pin_project! {
/// Future for the [`send_all`](super::SinkExt::send_all) method.
#[allow(explicit_outlives_requirements)] // https://github.com/rust-lang/rust/issues/60993
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct SendAll<'a, Si, St>
where
Si: ?Sized,
St: TryStream,
{
sink: &'a mut Si,
#[pin]
stream: Fuse<St>,
buffered: Option<St::Ok>,
}
}
impl<Si, St> fmt::Debug for SendAll<'_, Si, St>
where
Si: fmt::Debug + ?Sized,
St: fmt::Debug + TryStream,
St::Ok: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SendAll")
.field("sink", &self.sink)
.field("stream", &self.stream)
.field("buffered", &self.buffered)
.finish()
}
}
impl<'a, Si, St, Ok, Error> SendAll<'a, Si, St>
where
Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
St: TryStream<Ok = Ok, Error = Error> + Stream,
{
pub(super) fn new(sink: &'a mut Si, stream: St) -> Self {
Self { sink, stream: stream.fuse(), buffered: None }
}
fn try_start_send(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
item: St::Ok,
) -> Poll<Result<(), Si::Error>> {
let this = self.project();
debug_assert!(this.buffered.is_none());
match Pin::new(&mut *this.sink).poll_ready(cx)? {
Poll::Ready(()) => Poll::Ready(Pin::new(&mut *this.sink).start_send(item)),
Poll::Pending => {
*this.buffered = Some(item);
Poll::Pending
}
}
}
}
impl<Si, St, Ok, Error> Future for SendAll<'_, Si, St>
where
Si: Sink<Ok, Error = Error> + Unpin + ?Sized,
St: Stream<Item = Result<Ok, Error>>,
{
type Output = Result<(), Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// If we've got an item buffered already, we need to write it to the
// sink before we can do anything else
if let Some(item) = self.as_mut().project().buffered.take() {
ready!(self.as_mut().try_start_send(cx, item))?
}
loop {
let this = self.as_mut().project();
match this.stream.poll_next(cx)? {
Poll::Ready(Some(item)) => ready!(self.as_mut().try_start_send(cx, item))?,
Poll::Ready(None) => {
ready!(Pin::new(this.sink).poll_flush(cx))?;
return Poll::Ready(Ok(()));
}
Poll::Pending => {
ready!(Pin::new(this.sink).poll_flush(cx))?;
return Poll::Pending;
}
}
}
}
}