org.jctools.queues.unpadded.BaseLinkedUnpaddedQueue 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.unpadded;
import java.util.AbstractQueue;
import java.util.Iterator;
import java.util.Queue;
import static org.jctools.util.UnsafeAccess.UNSAFE;
import static org.jctools.util.UnsafeAccess.fieldOffset;
import org.jctools.queues.*;
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*/
abstract class BaseLinkedUnpaddedQueuePad0 extends AbstractQueue implements MessagePassingQueue {
}
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*/
abstract class BaseLinkedUnpaddedQueueProducerNodeRef extends BaseLinkedUnpaddedQueuePad0 {
final static long P_NODE_OFFSET = fieldOffset(BaseLinkedUnpaddedQueueProducerNodeRef.class, "producerNode");
private volatile LinkedQueueNode producerNode;
final void spProducerNode(LinkedQueueNode newValue) {
UNSAFE.putObject(this, P_NODE_OFFSET, newValue);
}
final void soProducerNode(LinkedQueueNode newValue) {
UNSAFE.putOrderedObject(this, P_NODE_OFFSET, newValue);
}
final LinkedQueueNode lvProducerNode() {
return producerNode;
}
final boolean casProducerNode(LinkedQueueNode expect, LinkedQueueNode newValue) {
return UNSAFE.compareAndSwapObject(this, P_NODE_OFFSET, expect, newValue);
}
final LinkedQueueNode lpProducerNode() {
return producerNode;
}
}
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*/
abstract class BaseLinkedUnpaddedQueuePad1 extends BaseLinkedUnpaddedQueueProducerNodeRef {
}
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*/
abstract class BaseLinkedUnpaddedQueueConsumerNodeRef extends BaseLinkedUnpaddedQueuePad1 {
private final static long C_NODE_OFFSET = fieldOffset(BaseLinkedUnpaddedQueueConsumerNodeRef.class, "consumerNode");
private LinkedQueueNode consumerNode;
final void spConsumerNode(LinkedQueueNode newValue) {
consumerNode = newValue;
}
@SuppressWarnings("unchecked")
final LinkedQueueNode lvConsumerNode() {
return (LinkedQueueNode) UNSAFE.getObjectVolatile(this, C_NODE_OFFSET);
}
final LinkedQueueNode lpConsumerNode() {
return consumerNode;
}
}
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*/
abstract class BaseLinkedUnpaddedQueuePad2 extends BaseLinkedUnpaddedQueueConsumerNodeRef {
}
/**
* NOTE: This class was automatically generated by org.jctools.queues.unpadded.JavaParsingUnpaddedQueueGenerator
* which can found in the jctools-build module. The original source file is BaseLinkedQueue.java.
*
* A base data structure for concurrent linked queues. For convenience also pulled in common single consumer
* methods since at this time there's no plan to implement MC.
*/
abstract class BaseLinkedUnpaddedQueue extends BaseLinkedUnpaddedQueuePad2 {
@Override
public final Iterator iterator() {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return this.getClass().getName();
}
protected final LinkedQueueNode newNode() {
return new LinkedQueueNode();
}
protected final LinkedQueueNode newNode(E e) {
return new LinkedQueueNode(e);
}
/**
* {@inheritDoc}
*
* IMPLEMENTATION NOTES:
* This is an O(n) operation as we run through all the nodes and count them.
* The accuracy of the value returned by this method is subject to races with producer/consumer threads. In
* particular when racing with the consumer thread this method may under estimate the size.
*
* @see java.util.Queue#size()
*/
@Override
public final int size() {
// Read consumer first, this is important because if the producer is node is 'older' than the consumer
// the consumer may overtake it (consume past it) invalidating the 'snapshot' notion of size.
LinkedQueueNode chaserNode = lvConsumerNode();
LinkedQueueNode producerNode = lvProducerNode();
int size = 0;
// must chase the nodes all the way to the producer node, but there's no need to count beyond expected head.
while (// don't go passed producer node
chaserNode != producerNode && // stop at last node
chaserNode != null && // stop at max int
size < Integer.MAX_VALUE) {
LinkedQueueNode next;
next = chaserNode.lvNext();
// check if this node has been consumed, if so return what we have
if (next == chaserNode) {
return size;
}
chaserNode = next;
size++;
}
return size;
}
/**
* {@inheritDoc}
*
* IMPLEMENTATION NOTES:
* Queue is empty when producerNode is the same as consumerNode. An alternative implementation would be to
* observe the producerNode.value is null, which also means an empty queue because only the
* consumerNode.value is allowed to be null.
*
* @see MessagePassingQueue#isEmpty()
*/
@Override
public boolean isEmpty() {
LinkedQueueNode consumerNode = lvConsumerNode();
LinkedQueueNode producerNode = lvProducerNode();
return consumerNode == producerNode;
}
protected E getSingleConsumerNodeValue(LinkedQueueNode currConsumerNode, LinkedQueueNode nextNode) {
// we have to null out the value because we are going to hang on to the node
final E nextValue = nextNode.getAndNullValue();
// Fix up the next ref of currConsumerNode to prevent promoted nodes from keeping new ones alive.
// We use a reference to self instead of null because null is already a meaningful value (the next of
// producer node is null).
currConsumerNode.soNext(currConsumerNode);
spConsumerNode(nextNode);
// currConsumerNode is now no longer referenced and can be collected
return nextValue;
}
/**
* {@inheritDoc}
*
* IMPLEMENTATION NOTES:
* Poll is allowed from a SINGLE thread.
* Poll is potentially blocking here as the {@link Queue#poll()} does not allow returning {@code null} if the queue is not
* empty. This is very different from the original Vyukov guarantees. See {@link #relaxedPoll()} for the original
* semantics.
* Poll reads {@code consumerNode.next} and:
*
* - If it is {@code null} AND the queue is empty return {@code null}, if queue is not empty spin wait for
* value to become visible.
*
- If it is not {@code null} set it as the consumer node and return it's now evacuated value.
*
* This means the consumerNode.value is always {@code null}, which is also the starting point for the queue.
* Because {@code null} values are not allowed to be offered this is the only node with it's value set to
* {@code null} at any one time.
*
* @see MessagePassingQueue#poll()
* @see java.util.Queue#poll()
*/
@Override
public E poll() {
final LinkedQueueNode currConsumerNode = lpConsumerNode();
LinkedQueueNode nextNode = currConsumerNode.lvNext();
if (nextNode != null) {
return getSingleConsumerNodeValue(currConsumerNode, nextNode);
} else if (currConsumerNode != lvProducerNode()) {
nextNode = spinWaitForNextNode(currConsumerNode);
// got the next node...
return getSingleConsumerNodeValue(currConsumerNode, nextNode);
}
return null;
}
/**
* {@inheritDoc}
*
* IMPLEMENTATION NOTES:
* Peek is allowed from a SINGLE thread.
* Peek is potentially blocking here as the {@link Queue#peek()} does not allow returning {@code null} if the queue is not
* empty. This is very different from the original Vyukov guarantees. See {@link #relaxedPeek()} for the original
* semantics.
* Poll reads the next node from the consumerNode and:
*
* - If it is {@code null} AND the queue is empty return {@code null}, if queue is not empty spin wait for
* value to become visible.
*
- If it is not {@code null} return it's value.
*
*
* @see MessagePassingQueue#peek()
* @see java.util.Queue#peek()
*/
@Override
public E peek() {
final LinkedQueueNode currConsumerNode = lpConsumerNode();
LinkedQueueNode nextNode = currConsumerNode.lvNext();
if (nextNode != null) {
return nextNode.lpValue();
} else if (currConsumerNode != lvProducerNode()) {
nextNode = spinWaitForNextNode(currConsumerNode);
// got the next node...
return nextNode.lpValue();
}
return null;
}
LinkedQueueNode spinWaitForNextNode(LinkedQueueNode currNode) {
LinkedQueueNode nextNode;
while ((nextNode = currNode.lvNext()) == null) {
// spin, we are no longer wait free
}
return nextNode;
}
@Override
public E relaxedPoll() {
final LinkedQueueNode currConsumerNode = lpConsumerNode();
final LinkedQueueNode nextNode = currConsumerNode.lvNext();
if (nextNode != null) {
return getSingleConsumerNodeValue(currConsumerNode, nextNode);
}
return null;
}
@Override
public E relaxedPeek() {
final LinkedQueueNode nextNode = lpConsumerNode().lvNext();
if (nextNode != null) {
return nextNode.lpValue();
}
return null;
}
@Override
public boolean relaxedOffer(E e) {
return offer(e);
}
@Override
public int drain(Consumer c, int limit) {
if (null == c)
throw new IllegalArgumentException("c is null");
if (limit < 0)
throw new IllegalArgumentException("limit is negative: " + limit);
if (limit == 0)
return 0;
LinkedQueueNode chaserNode = this.lpConsumerNode();
for (int i = 0; i < limit; i++) {
final LinkedQueueNode nextNode = chaserNode.lvNext();
if (nextNode == null) {
return i;
}
// we have to null out the value because we are going to hang on to the node
final E nextValue = getSingleConsumerNodeValue(chaserNode, nextNode);
chaserNode = nextNode;
c.accept(nextValue);
}
return limit;
}
@Override
public int drain(Consumer c) {
return MessagePassingQueueUtil.drain(this, c);
}
@Override
public void drain(Consumer c, WaitStrategy wait, ExitCondition exit) {
MessagePassingQueueUtil.drain(this, c, wait, exit);
}
@Override
public int capacity() {
return UNBOUNDED_CAPACITY;
}
}