/*
* Copyright 2010 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.gradle.messaging.dispatch;
import org.gradle.messaging.concurrent.AsyncStoppable;
import org.gradle.util.UncheckedException;
import java.util.concurrent.Executor;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* <p>Receives messages asynchronously. One or more {@link Receive} instances can use used as a source of messages.
* Messages are sent to a {@link Dispatch} </p>
*/
public class AsyncReceive<T> implements AsyncStoppable {
private enum State {
Init, Stopping, Stopped
}
private final Lock lock = new ReentrantLock();
private final Condition condition = lock.newCondition();
private final Executor executor;
private final Dispatch<? super T> dispatch;
private int receivers;
private State state = State.Init;
public AsyncReceive(Executor executor, final Dispatch<? super T> dispatch) {
this.executor = executor;
this.dispatch = dispatch;
}
public void receiveFrom(final Receive<? extends T> receive) {
onReceiveThreadStart();
executor.execute(new Runnable() {
public void run() {
try {
receiveMessages(receive);
} finally {
onReceiveThreadExit();
}
}
});
}
private void onReceiveThreadStart() {
lock.lock();
try {
if (state != State.Init) {
throw new IllegalStateException("This receiver has been stopped.");
}
receivers++;
} finally {
lock.unlock();
}
}
private void onReceiveThreadExit() {
lock.lock();
try {
receivers--;
condition.signalAll();
} finally {
lock.unlock();
}
}
private void receiveMessages(Receive<? extends T> receive) {
while (true) {
T message = receive.receive();
if (message == null) {
return;
}
dispatch.dispatch(message);
lock.lock();
try {
if (state != State.Init) {
return;
}
} finally {
lock.unlock();
}
}
}
private void setState(State state) {
this.state = state;
condition.signalAll();
}
public void requestStop() {
lock.lock();
try {
doRequestStop();
} finally {
lock.unlock();
}
}
private void doRequestStop() {
if (receivers > 0) {
setState(State.Stopping);
} else {
setState(State.Stopped);
}
}
public void stop() {
lock.lock();
try {
doRequestStop();
while (receivers > 0) {
condition.await();
}
setState(State.Stopped);
} catch (InterruptedException e) {
throw new UncheckedException(e);
} finally {
lock.unlock();
}
}
}