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use super::waiter::Waiter;
use futures::sync::mpsc;
use futures::sync::oneshot;
use futures::prelude::*;
pub trait BarrierSync<W: Waiter> {
fn wait_for(&mut self, waiter: W) -> Box<Future<Item=W::Item, Error=W::Error> + Send>;
}
pub struct Barrier<W: Waiter> {
sink: Option<mpsc::Sender<(W, oneshot::Sender<Result<W::Item, W::Error>>)>>,
}
impl<W: Waiter + 'static + Send> BarrierSync<W> for Barrier<W> {
fn wait_for(&mut self, waiter: W) -> Box<Future<Item=W::Item, Error=W::Error> + Send> {
let (resp_tx, resp_rx) = oneshot::channel();
if self.sink.is_none() {
let (barrier_tx, barrier_rx) = mpsc::channel(40);
self.barrier_task(barrier_rx);
self.sink.replace(barrier_tx);
}
let chan = self.sink.as_mut().unwrap().clone();
/*TODO: I want meaningful error types... */
let f1 = chan
.send((waiter, resp_tx))
.map_err(|err| W::Error::from(()))
.and_then(|_| {
resp_rx.then(|result| {
match result {
Ok(Ok(result)) => Ok(result),
Ok(Err(err)) => Err(err),
Err(err) => Err(W::Error::from(())),
}
})
});
Box::new(f1)
}
}
impl<W: Waiter + 'static + Send> Barrier<W> {
pub fn new() -> Barrier<W> {
Barrier {
sink: None,
}
}
fn barrier_task(&self, receiver: mpsc::Receiver<(W, oneshot::Sender<Result<W::Item, W::Error>>)>) {
enum Message<W: Waiter> {
Request((W, oneshot::Sender<Result<<W as Waiter>::Item, <W as Waiter>::Error>>)),
OnCondition(Result<(), <W as Waiter>::ConditionError>),
}
let mut polling = false;
let (on_condition_tx, on_condition_rx) = mpsc::unbounded();
let mut waiters = Vec::new();
let f1 = receiver.map(|request| Message::Request(request));
let f2 = on_condition_rx.map(|result| Message::OnCondition(result));
let inner_condition = on_condition_tx.clone();
let f =
f1.select(f2).for_each(move |message| {
match message {
Message::Request((waiter, backchan)) => {
if waiter.blocked() && !polling {
println!("locked");
let c1 = inner_condition.clone();
let f = waiter
.condition_poller()
.map(|_| ())
.then(|result| {
c1.send(result).wait();
Ok(())
});
tokio::spawn(f);
polling = true;
waiters.push((waiter, backchan));
} else if waiter.blocked() || polling {
println!("polling");
waiters.push((waiter, backchan));
} else {
println!("Pass along waiter!");
let f = waiter.into_future()
.then(|res| {
backchan.send(res);
Ok(())
});
tokio::spawn(f);
}
},
Message::OnCondition(result) => {
polling = false;
/*Resubmit all waiters back to the request channel
* At least one waiter will pass the barrier
*/
match result {
Ok(_) => {
while waiters.len() > 0 {
let (waiter, backchan) = waiters.pop().unwrap();
let f = waiter.into_future()
.then(|res| {
backchan.send(res);
Ok(())
});
tokio::spawn(f);
}
},
_ => { panic!("condition channel closed") }
}
}
}
Ok(())
})
.map(|_| ())
.map_err(|_| ());
tokio::spawn(f);
}
}
|
