org.jctools.queues.SpscUnboundedArrayQueue Maven / Gradle / Ivy
/*
* 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;
import org.jctools.util.Pow2;
import static org.jctools.util.UnsafeRefArrayAccess.*;
/**
* An SPSC array queue which starts at initialCapacity and grows indefinitely in linked chunks of the initial size.
* The queue grows only when the current chunk is full and elements are not copied on
* resize, instead a link to the new chunk is stored in the old chunk for the consumer to follow.
*
* @param
*/
public class SpscUnboundedArrayQueue extends BaseSpscLinkedArrayQueue
{
public SpscUnboundedArrayQueue(int chunkSize)
{
int chunkCapacity = Math.max(Pow2.roundToPowerOfTwo(chunkSize), 16);
long mask = chunkCapacity - 1;
E[] buffer = allocateRefArray(chunkCapacity + 1);
producerBuffer = buffer;
producerMask = mask;
consumerBuffer = buffer;
consumerMask = mask;
producerBufferLimit = mask - 1; // we know it's all empty to start with
}
@Override
final boolean offerColdPath(E[] buffer, long mask, long pIndex, long offset, E v, Supplier s)
{
// 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 == lvRefElement(buffer, calcCircularRefElementOffset(pBufferLimit, mask)))
{
producerBufferLimit = pBufferLimit - 1; // joy, there's plenty of room
writeToQueue(buffer, v == null ? s.get() : v, pIndex, offset);
}
else if (null == lvRefElement(buffer, calcCircularRefElementOffset(pIndex + 1, mask)))
{ // buffer is not full
writeToQueue(buffer, v == null ? s.get() : v, 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 E[] newBuffer = allocateRefArray((int) (mask + 2));
producerBuffer = newBuffer;
producerBufferLimit = pIndex + mask - 1;
linkOldToNew(pIndex, buffer, offset, newBuffer, offset, v == null ? s.get() : v);
}
return true;
}
@Override
public int fill(Supplier s)
{
return fill(s, (int) this.producerMask);
}
@Override
public int capacity()
{
return UNBOUNDED_CAPACITY;
}
}