/*
* Copyright (c) 2008-2012, Hazel Bilisim Ltd. All Rights Reserved.
*
* 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 com.hazelcast.util;
import java.util.AbstractQueue;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class ResponseQueueFactory {
public static BlockingQueue newResponseQueue() {
return new LockBasedResponseQueue();
}
private final static class LockBasedResponseQueue extends AbstractQueue implements BlockingQueue {
private Object response = null;
private final Lock lock = new ReentrantLock();
private final Condition noValue = lock.newCondition();
private final static Object NULL = new Object();
public Object take() throws InterruptedException {
lock.lock();
try {
//noinspection WhileLoopSpinsOnField
while (response == null) {
noValue.await();
}
return getAndRemoveResponse();
} finally {
lock.unlock();
}
}
public boolean offer(Object o, long timeout, TimeUnit unit) throws InterruptedException {
return offer(o);
}
public Object poll(long timeout, TimeUnit unit) throws InterruptedException {
if (timeout < 0) throw new IllegalArgumentException();
long remaining = unit.toMillis(timeout);
lock.lock();
try {
while (response == null && remaining > 0) {
long start = System.currentTimeMillis();
noValue.await(remaining, TimeUnit.MILLISECONDS);
remaining -= (System.currentTimeMillis() - start);
}
return getAndRemoveResponse();
} finally {
lock.unlock();
}
}
public void put(Object o) throws InterruptedException {
offer(o);
}
public boolean offer(Object obj) {
if (obj == null) {
obj = NULL;
}
lock.lock();
try {
if (response != null) {
return false;
}
response = obj;
//noinspection CallToSignalInsteadOfSignalAll
noValue.signal();
return true;
} finally {
lock.unlock();
}
}
public Object poll() {
lock.lock();
try {
return getAndRemoveResponse();
} finally {
lock.unlock();
}
}
/**
* Internal method, should be called under lock.
*
* @return response
*/
private Object getAndRemoveResponse() {
final Object value = response;
response = null;
return (value == NULL) ? null : value;
}
public int remainingCapacity() {
throw new UnsupportedOperationException();
}
public int drainTo(Collection c) {
throw new UnsupportedOperationException();
}
public int drainTo(Collection c, int maxElements) {
throw new UnsupportedOperationException();
}
public void clear() {
lock.lock();
try {
response = null;
} finally {
lock.unlock();
}
}
@Override
public Iterator iterator() {
throw new UnsupportedOperationException();
}
@Override
public int size() {
lock.lock();
try {
return (response == null) ? 0 : 1;
} finally {
lock.unlock();
}
}
public Object peek() {
lock.lock();
try {
return response;
} finally {
lock.unlock();
}
}
}
}