com.hazelcast.internal.util.concurrent.ManyToOneConcurrentArrayQueue Maven / Gradle / Ivy
/*
* Original work Copyright 2015 Real Logic Ltd.
* Modified work Copyright (c) 2015-2021, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.internal.util.concurrent;
import java.util.Collection;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.function.Predicate;
/**
* Many producers to single consumer concurrent queue backed by an array.
* Adapted from the Agrona project.
*
* @param type of the elements stored in the queue.
*/
public class ManyToOneConcurrentArrayQueue extends AbstractConcurrentArrayQueue {
public ManyToOneConcurrentArrayQueue(int requestedCapacity) {
super(requestedCapacity);
}
@Override
public boolean offer(E e) {
assert e != null : "attempt to offer a null element";
final int capacity = this.capacity;
long acquiredHead = sharedHeadCache;
long bufferLimit = acquiredHead + capacity;
long acquiredTail;
do {
acquiredTail = tail;
if (acquiredTail >= bufferLimit) {
acquiredHead = head;
bufferLimit = acquiredHead + capacity;
if (acquiredTail >= bufferLimit) {
return false;
}
SHARED_HEAD_CACHE.lazySet(this, acquiredHead);
}
} while (!TAIL.compareAndSet(this, acquiredTail, acquiredTail + 1));
buffer.lazySet(seqToArrayIndex(acquiredTail, capacity - 1), e);
return true;
}
@Override
@SuppressWarnings("unchecked")
public E poll() {
final long head = this.head;
final AtomicReferenceArray buffer = this.buffer;
final int arrayIndex = seqToArrayIndex(head, capacity - 1);
final E item = buffer.get(arrayIndex);
if (item != null) {
buffer.lazySet(arrayIndex, null);
HEAD.lazySet(this, head + 1);
}
return item;
}
@Override
@SuppressWarnings("unchecked")
public int drain(Predicate itemHandler) {
final AtomicReferenceArray buffer = this.buffer;
final long mask = capacity - 1;
final long acquiredHead = head;
final long limit = acquiredHead + mask + 1;
long nextSequence = acquiredHead;
while (nextSequence < limit) {
final int arrayIndex = seqToArrayIndex(nextSequence, mask);
final E item = buffer.get(arrayIndex);
if (item == null) {
break;
}
buffer.lazySet(arrayIndex, null);
nextSequence++;
HEAD.lazySet(this, nextSequence);
if (!itemHandler.test(item)) {
break;
}
}
return (int) (nextSequence - acquiredHead);
}
@SuppressWarnings("unchecked")
@Override
public int drainTo(Collection target, int limit) {
final AtomicReferenceArray buffer = this.buffer;
final long mask = capacity - 1;
long nextSequence = head;
int count = 0;
while (count < limit) {
final int arrayIndex = seqToArrayIndex(nextSequence, mask);
final E item = buffer.get(arrayIndex);
if (item == null) {
break;
}
buffer.lazySet(arrayIndex, null);
nextSequence++;
HEAD.lazySet(this, nextSequence);
count++;
target.add(item);
}
return count;
}
}