/*
* 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_voltpatches.queues;
import java.util.AbstractQueue;
import java.util.Iterator;
import org.jctools_voltpatches.util.Pow2;
abstract class ConcurrentCircularArrayQueueL0Pad<E> extends AbstractQueue<E> implements MessagePassingQueue<E> {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
/**
* A concurrent access enabling class used by circular array based queues this class exposes an offset computation
* method along with differently memory fenced load/store methods into the underlying array. The class is pre-padded and
* the array is padded on either side to help with False sharing prvention. It is expected theat subclasses handle post
* padding.
* <p>
* Offset calculation is separate from access to enable the reuse of a give compute offset.
* <p>
* Load/Store methods using a <i>buffer</i> parameter are provided to allow the prevention of final field reload after a
* LoadLoad barrier.
* <p>
*
* @author nitsanw
*
* @param <E>
*/
public abstract class ConcurrentCircularArrayQueue<E> extends ConcurrentCircularArrayQueueL0Pad<E> {
protected final long mask;
// @Stable :(
protected final E[] buffer;
public ConcurrentCircularArrayQueue(int capacity) {
int actualCapacity = Pow2.roundToPowerOfTwo(capacity);
mask = actualCapacity - 1;
buffer = SparsePaddedCircularArrayOffsetCalculator.allocate(actualCapacity);
}
/**
* @param index desirable element index
* @return the offset in bytes within the array for a given index.
*/
protected final long calcElementOffset(long index) {
return calcElementOffset(index, mask);
}
/**
* @param index desirable element index
* @param mask
* @return the offset in bytes within the array for a given index.
*/
protected static long calcElementOffset(long index, long mask) {
return SparsePaddedCircularArrayOffsetCalculator.calcElementOffset(index, mask);
}
@Override
public Iterator<E> iterator() {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
while (poll() != null || !isEmpty())
;
}
@Override
public int capacity() {
return (int) (mask + 1);
}
}