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A super fast inter-thread transfer queue.
The newest version!
/*
* MentaQueue => http://mentaqueue.soliveirajr.com
* Copyright (C) 2012 Sergio Oliveira Jr. ([email protected])
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.mentaqueue;
import static org.mentaqueue.util.BuilderUtils.createBuilder;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.mentaqueue.util.Builder;
import org.mentaqueue.util.NumberUtils;
public class LockedQueue implements BatchingQueue {
private final static int DEFAULT_CAPACITY = 1024 * 16;
private final int capacity;
private final E[] data;
private long nextOfferValue = -1;
private long nextPollValue = -1;
private long pollCount = 0;
private long offeringSequence = -1;
private long pollingSequence = -1;
private final Lock offeringLock = new ReentrantLock();
private final Lock pollingLock = new ReentrantLock();
private long maxSeq;
@SuppressWarnings("unchecked")
public LockedQueue(int capacity, Builder builder) {
NumberUtils.ensurePowerOfTwo(capacity);
this.capacity = capacity;
this.data = (E[]) new Object[capacity];
for (int i = 0; i < capacity; i++) {
this.data[i] = builder.newInstance();
}
this.maxSeq = findMaxSeqBeforeWrapping();
}
public LockedQueue(Builder builder) {
this(DEFAULT_CAPACITY, builder);
}
public LockedQueue(Class klass) {
this(createBuilder(klass));
}
public LockedQueue(int capacity, Class klass) {
this(capacity, createBuilder(klass));
}
private final long findMaxSeqBeforeWrapping() {
pollingLock.lock();
try {
return capacity + pollingSequence;
} finally {
pollingLock.unlock();
}
}
@Override
public E nextToDispatch() {
long index = ++nextOfferValue;
if (index <= maxSeq) {
// we are safe
} else {
// recalculate max sequence...
this.maxSeq = findMaxSeqBeforeWrapping();
if (index > maxSeq) {
// we are still ahead... nothing to do for now...
nextOfferValue--;
return null;
}
}
return data[(int) (index & capacity - 1)];
}
@Override
public void flush(boolean lazySet) {
offeringLock.lock();
offeringSequence = nextOfferValue;
offeringLock.unlock();
}
@Override
public long availableToPoll() {
offeringLock.lock();
try {
return offeringSequence - nextPollValue;
} finally {
offeringLock.unlock();
}
}
@Override
public final void flush() {
flush(false);
}
@Override
public E poll() {
pollCount++;
return data[(int) (++nextPollValue & capacity - 1)];
}
@Override
public E peek() {
return data[(int) (nextPollValue & capacity - 1)];
}
@Override
public void donePolling(boolean lazySet) {
pollingLock.lock();
pollingSequence = nextPollValue;
pollingLock.unlock();
pollCount = 0;
}
@Override
public final void donePolling() {
donePolling(false);
}
@Override
public final void rollback() {
rollback(pollCount);
}
@Override
public final void rollback(long count) {
if (count < 0 || count > pollCount) {
throw new RuntimeException("Invalid rollback request! polled=" + pollCount + " requested=" + count);
}
nextPollValue -= count;
pollCount -= count;
}
}
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