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use std::{
pin::Pin,
sync::Arc,
task::{Context, Poll},
};
use futures::{
channel::mpsc::{channel, Receiver, Sender, TrySendError},
Stream, StreamExt,
};
/// The `Notify` struct encapsulates asynchronous, multi-producer, single-consumer (MPSC) channel functionality.
/// It is used to send notifications of type `T` from multiple producers to a single consumer.
#[derive(Debug)]
pub struct Notify<T> {
sender: Sender<T>,
receiver: Arc<futures::lock::Mutex<Receiver<T>>>,
}
impl<T> Clone for Notify<T> {
fn clone(&self) -> Self {
Self {
sender: self.sender.clone(),
receiver: self.receiver.clone(),
}
}
}
impl<T> Notify<T> {
/// Creates a new instance of `Notify`.
/// It initializes a channel with a buffer size of 1 and wraps the receiver in an `Arc<Mutex>`.
pub fn new() -> Self {
let (sender, receiver) = channel(1);
Self {
sender,
receiver: Arc::new(futures::lock::Mutex::new(receiver)),
}
}
/// Sends a notification of type `T` to the receiver.
pub fn notify(&self, value: T) -> Result<(), TrySendError<T>> {
self.sender.clone().try_send(value)
}
/// Waits for and retrieves the next notification.
/// This is an asynchronous method that awaits until a notification is available.
/// Panics if the sender is dropped, ensuring that `notified` is always eventually fulfilled.
pub async fn notified(&self) {
self.receiver
.lock()
.await
.next()
.await
.expect("sender is dropped");
}
}
impl<T> Default for Notify<T> {
fn default() -> Self {
Self::new()
}
}
impl<T> Stream for Notify<T> {
type Item = T;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
if let Some(mut receiver) = self.receiver.try_lock() {
receiver.poll_next_unpin(cx)
} else {
Poll::Pending
}
}
}