From 17893388feed5f91ebd254ac7ad8e2801ca8a6d0 Mon Sep 17 00:00:00 2001
From: David Blajda <blajda@hotmail.com>
Date: Wed, 19 Dec 2018 16:14:14 +0000
Subject: Place barrier and waiters in their own modules

---
 src/sync/barrier.rs | 130 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 src/sync/barrier.rs

(limited to 'src/sync/barrier.rs')

diff --git a/src/sync/barrier.rs b/src/sync/barrier.rs
new file mode 100644
index 0000000..7e53b12
--- /dev/null
+++ b/src/sync/barrier.rs
@@ -0,0 +1,130 @@
+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);
+    }
+}
-- 
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