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