co.paralleluniverse.strands.channels.ReducingReceivePort Maven / Gradle / Ivy
/*
* Quasar: lightweight threads and actors for the JVM.
* Copyright (c) 2013-2015, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.strands.channels;
import co.paralleluniverse.common.util.Function2;
import co.paralleluniverse.fibers.SuspendExecution;
import co.paralleluniverse.strands.Timeout;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* A transforming {@link ReceivePort} that will apply a reduction function to values.
*
* @author circlespainter
*/
class ReducingReceivePort extends ReceivePortTransformer implements ReceivePort {
private final Function2 f;
private final AtomicBoolean receivedAtLeastOnce = new AtomicBoolean(false);
private T prev;
public ReducingReceivePort(final ReceivePort target, final Function2 f, T init) {
super(target);
this.f = f;
this.prev = init;
}
@Override
public T receive(final Timeout timeout) throws SuspendExecution, InterruptedException {
return checkReceivedAtLeastOnce(super.receive(timeout));
}
@Override
public T tryReceive() {
return checkReceivedAtLeastOnce(super.tryReceive());
}
@Override
public T receive() throws SuspendExecution, InterruptedException {
return checkReceivedAtLeastOnce(super.receive());
}
@Override
public boolean isClosed() {
return super.isClosed() && receivedAtLeastOnce.get();
}
@Override
public T receive(final long timeout, final TimeUnit unit) throws SuspendExecution, InterruptedException {
return checkReceivedAtLeastOnce(super.receive(timeout, unit));
}
@Override
protected T transform(final S m) {
return (this.prev = reduce(prev, m));
}
private T reduce(final T prev, final S m) {
if (f != null && prev != null)
return f.apply(prev, m);
throw new UnsupportedOperationException();
}
private T checkReceivedAtLeastOnce(final T r) {
T ret = r;
if (target.isClosed() && !receivedAtLeastOnce.get())
ret = prev;
receivedAtLeastOnce.set(true);
return ret;
}
}