package org.apache.qpid.pool;
import java.util.AbstractQueue;
import java.util.Iterator;
import java.util.Collection;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.atomic.AtomicInteger;
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*
*/
public class ReadWriteJobQueue extends AbstractQueue<Runnable> implements BlockingQueue<Runnable>
{
private final AtomicInteger _count = new AtomicInteger(0);
private final ReentrantLock _takeLock = new ReentrantLock();
private final Condition _notEmpty = _takeLock.newCondition();
private final ReentrantLock _putLock = new ReentrantLock();
private final ConcurrentLinkedQueue<ReadWriteRunnable> _readJobQueue = new ConcurrentLinkedQueue<ReadWriteRunnable>();
private final ConcurrentLinkedQueue<ReadWriteRunnable> _writeJobQueue = new ConcurrentLinkedQueue<ReadWriteRunnable>();
private class ReadWriteJobIterator implements Iterator<Runnable>
{
private boolean _onReads;
private Iterator<ReadWriteRunnable> _iter = _writeJobQueue.iterator();
public boolean hasNext()
{
if(!_iter.hasNext())
{
if(_onReads)
{
_iter = _readJobQueue.iterator();
_onReads = true;
return _iter.hasNext();
}
else
{
return false;
}
}
else
{
return true;
}
}
public Runnable next()
{
if(_iter.hasNext())
{
return _iter.next();
}
else
{
return null;
}
}
public void remove()
{
_takeLock.lock();
try
{
_iter.remove();
_count.decrementAndGet();
}
finally
{
_takeLock.unlock();
}
}
}
public Iterator<Runnable> iterator()
{
return new ReadWriteJobIterator();
}
public int size()
{
return _count.get();
}
public boolean offer(final Runnable runnable)
{
final ReadWriteRunnable job = (ReadWriteRunnable) runnable;
final ReentrantLock putLock = _putLock;
putLock.lock();
try
{
if(job.isRead())
{
_readJobQueue.offer(job);
}
else
{
_writeJobQueue.offer(job);
}
if(_count.getAndIncrement() == 0)
{
_takeLock.lock();
try
{
_notEmpty.signal();
}
finally
{
_takeLock.unlock();
}
}
return true;
}
finally
{
putLock.unlock();
}
}
public void put(final Runnable runnable) throws InterruptedException
{
final ReadWriteRunnable job = (ReadWriteRunnable) runnable;
final ReentrantLock putLock = _putLock;
putLock.lock();
try
{
if(job.isRead())
{
_readJobQueue.offer(job);
}
else
{
_writeJobQueue.offer(job);
}
if(_count.getAndIncrement() == 0)
{
_takeLock.lock();
try
{
_notEmpty.signal();
}
finally
{
_takeLock.unlock();
}
}
}
finally
{
putLock.unlock();
}
}
public boolean offer(final Runnable runnable, final long timeout, final TimeUnit unit) throws InterruptedException
{
final ReadWriteRunnable job = (ReadWriteRunnable) runnable;
final ReentrantLock putLock = _putLock;
putLock.lock();
try
{
if(job.isRead())
{
_readJobQueue.offer(job);
}
else
{
_writeJobQueue.offer(job);
}
if(_count.getAndIncrement() == 0)
{
_takeLock.lock();
try
{
_notEmpty.signal();
}
finally
{
_takeLock.unlock();
}
}
return true;
}
finally
{
putLock.unlock();
}
}
public Runnable take() throws InterruptedException
{
final ReentrantLock takeLock = _takeLock;
takeLock.lockInterruptibly();
try
{
try
{
while (_count.get() == 0)
{
_notEmpty.await();
}
}
catch (InterruptedException ie)
{
_notEmpty.signal();
throw ie;
}
ReadWriteRunnable job = _writeJobQueue.poll();
if(job == null)
{
job = _readJobQueue.poll();
}
int c = _count.getAndDecrement();
if (c > 1)
{
_notEmpty.signal();
}
return job;
}
finally
{
takeLock.unlock();
}
}
public Runnable poll(final long timeout, final TimeUnit unit) throws InterruptedException
{
final ReentrantLock takeLock = _takeLock;
final AtomicInteger count = _count;
long nanos = unit.toNanos(timeout);
takeLock.lockInterruptibly();
ReadWriteRunnable job = null;
try
{
for (;;)
{
if (count.get() > 0)
{
job = _writeJobQueue.poll();
if(job == null)
{
job = _readJobQueue.poll();
}
int c = count.getAndDecrement();
if (c > 1)
{
_notEmpty.signal();
}
break;
}
if (nanos <= 0)
{
return null;
}
try
{
nanos = _notEmpty.awaitNanos(nanos);
}
catch (InterruptedException ie)
{
_notEmpty.signal();
throw ie;
}
}
}
finally
{
takeLock.unlock();
}
return job;
}
public int remainingCapacity()
{
return Integer.MAX_VALUE;
}
public int drainTo(final Collection<? super Runnable> c)
{
int total = 0;
_putLock.lock();
_takeLock.lock();
try
{
ReadWriteRunnable job;
while((job = _writeJobQueue.peek())!= null)
{
c.add(job);
_writeJobQueue.poll();
_count.decrementAndGet();
total++;
}
while((job = _readJobQueue.peek())!= null)
{
c.add(job);
_readJobQueue.poll();
_count.decrementAndGet();
total++;
}
}
finally
{
_takeLock.unlock();
_putLock.unlock();
}
return total;
}
public int drainTo(final Collection<? super Runnable> c, final int maxElements)
{
int total = 0;
_putLock.lock();
_takeLock.lock();
try
{
ReadWriteRunnable job;
while(total<=maxElements && (job = _writeJobQueue.peek())!= null)
{
c.add(job);
_writeJobQueue.poll();
_count.decrementAndGet();
total++;
}
while(total<=maxElements && (job = _readJobQueue.peek())!= null)
{
c.add(job);
_readJobQueue.poll();
_count.decrementAndGet();
total++;
}
}
finally
{
_takeLock.unlock();
_putLock.unlock();
}
return total;
}
public Runnable poll()
{
final ReentrantLock takeLock = _takeLock;
takeLock.lock();
try
{
if(_count.get() > 0)
{
ReadWriteRunnable job = _writeJobQueue.poll();
if(job == null)
{
job = _readJobQueue.poll();
}
_count.decrementAndGet();
return job;
}
else
{
return null;
}
}
finally
{
takeLock.unlock();
}
}
public Runnable peek()
{
final ReentrantLock takeLock = _takeLock;
takeLock.lock();
try
{
ReadWriteRunnable job = _writeJobQueue.peek();
if(job == null)
{
job = _readJobQueue.peek();
}
return job;
}
finally
{
takeLock.unlock();
}
}
}