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use super::subscriber::*;
use futures::future::{BoxFuture};
///
/// A message sender represents a reserved space for sending a message. Because the
/// space is reserved, the message can be sent immediately
///
pub struct MessageSender<Message> {
/// Callback that sends the message
send_message: Option<Box<dyn FnOnce(Message) -> ()+Send>>,
/// Callback that abandons sending the message
cancel_send: Option<Box<dyn FnOnce() -> ()+Send>>,
/// Set to true once the message has been sent
sent: bool
}
///
/// Trait that provides functions for publishing messages to subscribers
///
pub trait MessagePublisher
where Self: Send {
type Message: 'static+Send;
///
/// Creates a subscription to this publisher
///
/// Any future messages sent here will also be sent to this subscriber.
///
fn subscribe(&mut self) -> Subscriber<Self::Message>;
///
/// Reserves a space for a message with the subscribers, returning when it's ready
///
fn when_ready(&mut self) -> BoxFuture<'static, MessageSender<Self::Message>>;
///
/// Waits until all subscribers have consumed all pending messages
///
fn when_empty(&mut self) -> BoxFuture<'static, ()>;
///
/// Returns true if this publisher is closed (will not publish any further messages to its subscribers)
///
fn is_closed(&self) -> bool;
///
/// Future that returns when this publisher is closed
///
fn when_closed(&self) -> BoxFuture<'static, ()>;
///
/// Publishes a message to the subscribers of this object
///
fn publish(&mut self, message: Self::Message) -> BoxFuture<'static, ()> {
let when_ready = self.when_ready();
Box::pin(async move {
let sender = when_ready.await;
sender.send(message);
})
}
}
impl<Message> MessageSender<Message> {
///
/// Creates a new message sender that will perform the supplied actions when the message is sent
///
pub fn new<TSendMsg, TCancelSend>(send_msg: TSendMsg, cancel_send: TCancelSend) -> MessageSender<Message>
where TSendMsg: 'static+Send+FnOnce(Message) -> (),
TCancelSend: 'static+Send+FnOnce() -> () {
MessageSender {
send_message: Some(Box::new(send_msg)),
cancel_send: Some(Box::new(cancel_send)),
sent: false
}
}
///
/// Sends a message, consuming this object
///
#[inline]
pub fn send(mut self, message: Message) {
self.sent = true;
self.send_message.take().map(move |send_message| send_message(message));
}
}
impl<Message> Drop for MessageSender<Message> {
fn drop(&mut self) {
if !self.sent {
self.cancel_send.take().map(move |cancel_send| cancel_send());
}
}
}