/*
* 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.jctools.queues.atomic;
import org.jctools.util.Pow2;
import java.util.concurrent.atomic.AtomicReferenceArray;
public class SpscUnboundedAtomicArrayQueue<E> extends BaseSpscLinkedAtomicArrayQueue<E> {
public SpscUnboundedAtomicArrayQueue(final int chunkSize) {
int chunkCapacity = Math.max(Pow2.roundToPowerOfTwo(chunkSize), 16);
long mask = chunkCapacity - 1;
AtomicReferenceArray<E> buffer = allocate(chunkCapacity + 1);
producerBuffer = buffer;
producerMask = mask;
consumerBuffer = buffer;
consumerMask = mask;
producerBufferLimit = mask - 1; // we know it's all empty to start with
soProducerIndex(0L);
}
@Override
protected boolean offerColdPath(AtomicReferenceArray<E> buffer, long mask, E e, long pIndex, int offset) {
// use a fixed lookahead step based on buffer capacity
final long lookAheadStep = (mask + 1) / 4;
long pBufferLimit = pIndex + lookAheadStep;
// go around the buffer or add a new buffer
if (null == lvElement(buffer, calcElementOffset(pBufferLimit, mask))) {
producerBufferLimit = pBufferLimit - 1; // joy, there's plenty of room
writeToQueue(buffer, e, pIndex, offset);
}
else if (null == lvElement(buffer, calcElementOffset(pIndex + 1, mask))) { // buffer is not full
writeToQueue(buffer, e, pIndex, offset);
}
else {
// we got one slot left to write into, and we are not full. Need to link new buffer.
// allocate new buffer of same length
final AtomicReferenceArray<E> newBuffer = allocate((int)(mask + 2));
producerBuffer = newBuffer;
producerBufferLimit = pIndex + mask - 1;
linkOldToNew(pIndex, buffer, offset, newBuffer, offset, e);
}
return true;
}
}