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use crate::ring_buffer::RingBuffer;
use async_channel::RecvError;
use futures::task::{Context, Poll};
use futures::Sink;
use std::pin::Pin;
use std::sync::Arc;
#[derive(Debug, Clone)]
pub struct AsyncPublishError;
impl std::fmt::Display for AsyncPublishError {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(f, "publisher encountered error it could not recover from")
}
}
pub struct AsyncPublisher<T> {
ring: Arc<RingBuffer>,
sequence: Option<u64>,
event: Option<T>,
}
impl<T: 'static + Unpin> AsyncPublisher<T> {
pub(crate) fn new(ring: Arc<RingBuffer>) -> Self {
Self {
ring,
sequence: None,
event: None,
}
}
pub(crate) fn write_to_ring(&mut self) {
if let Some(sequence) = self.sequence.take() {
if let Some(envelope) = self.ring.get_envelope(sequence) {
if let Some(event) = self.event.take() {
envelope.overwrite(sequence, event);
}
}
}
}
}
impl<T: 'static + Unpin> Sink<T> for AsyncPublisher<T> {
type Error = RecvError;
fn poll_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
if self.event.is_some() {
Poll::Pending
} else {
Poll::Ready(Ok(()))
}
}
fn start_send(mut self: Pin<&mut Self>, item: T) -> Result<(), Self::Error> {
let sequence = self.ring.next();
self.sequence.replace(sequence);
self.event.replace(item);
Ok(())
}
fn poll_flush(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
) -> Poll<Result<(), Self::Error>> {
self.write_to_ring();
Poll::Ready(Ok(()))
}
fn poll_close(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
drop(self);
Poll::Ready(Ok(()))
}
}
#[cfg(test)]
mod tests {
}