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use core::fmt::{Debug, Formatter, Result as FmtResult};
use core::pin::Pin;
use futures_core::task::{Context, Poll};
use futures_sink::Sink;
use pin_project_lite::pin_project;
pin_project! {
/// Sink that clones incoming items and forwards them to two sinks at the same time.
///
/// Backpressure from any downstream sink propagates up, which means that this sink
/// can only process items as fast as its _slowest_ downstream sink.
#[must_use = "sinks do nothing unless polled"]
pub struct Fanout<Si1, Si2> {
#[pin]
sink1: Si1,
#[pin]
sink2: Si2
}
}
impl<Si1, Si2> Fanout<Si1, Si2> {
pub(super) fn new(sink1: Si1, sink2: Si2) -> Self {
Self { sink1, sink2 }
}
/// Get a shared reference to the inner sinks.
pub fn get_ref(&self) -> (&Si1, &Si2) {
(&self.sink1, &self.sink2)
}
/// Get a mutable reference to the inner sinks.
pub fn get_mut(&mut self) -> (&mut Si1, &mut Si2) {
(&mut self.sink1, &mut self.sink2)
}
/// Get a pinned mutable reference to the inner sinks.
pub fn get_pin_mut(self: Pin<&mut Self>) -> (Pin<&mut Si1>, Pin<&mut Si2>) {
let this = self.project();
(this.sink1, this.sink2)
}
/// Consumes this combinator, returning the underlying sinks.
///
/// Note that this may discard intermediate state of this combinator,
/// so care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> (Si1, Si2) {
(self.sink1, self.sink2)
}
}
impl<Si1: Debug, Si2: Debug> Debug for Fanout<Si1, Si2> {
fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
f.debug_struct("Fanout").field("sink1", &self.sink1).field("sink2", &self.sink2).finish()
}
}
impl<Si1, Si2, Item> Sink<Item> for Fanout<Si1, Si2>
where
Si1: Sink<Item>,
Item: Clone,
Si2: Sink<Item, Error = Si1::Error>,
{
type Error = Si1::Error;
fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let sink1_ready = this.sink1.poll_ready(cx)?.is_ready();
let sink2_ready = this.sink2.poll_ready(cx)?.is_ready();
let ready = sink1_ready && sink2_ready;
if ready {
Poll::Ready(Ok(()))
} else {
Poll::Pending
}
}
fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error> {
let this = self.project();
this.sink1.start_send(item.clone())?;
this.sink2.start_send(item)?;
Ok(())
}
fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let sink1_ready = this.sink1.poll_flush(cx)?.is_ready();
let sink2_ready = this.sink2.poll_flush(cx)?.is_ready();
let ready = sink1_ready && sink2_ready;
if ready {
Poll::Ready(Ok(()))
} else {
Poll::Pending
}
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
let this = self.project();
let sink1_ready = this.sink1.poll_close(cx)?.is_ready();
let sink2_ready = this.sink2.poll_close(cx)?.is_ready();
let ready = sink1_ready && sink2_ready;
if ready {
Poll::Ready(Ok(()))
} else {
Poll::Pending
}
}
}