io.netty.util.internal.shaded.org.jctools.queues.BaseLinkedQueue Maven / Gradle / Ivy
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/*
* 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 io.netty.util.internal.shaded.org.jctools.queues;
import java.util.AbstractQueue;
import java.util.Iterator;
import static io.netty.util.internal.shaded.org.jctools.util.UnsafeAccess.UNSAFE;
import static io.netty.util.internal.shaded.org.jctools.util.UnsafeAccess.fieldOffset;
abstract class BaseLinkedQueuePad0 extends AbstractQueue implements MessagePassingQueue
{
long p00, p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16;
}
// $gen:ordered-fields
abstract class BaseLinkedQueueProducerNodeRef extends BaseLinkedQueuePad0
{
final static long P_NODE_OFFSET = fieldOffset(BaseLinkedQueueProducerNodeRef.class, "producerNode");
private LinkedQueueNode producerNode;
final void spProducerNode(LinkedQueueNode newValue)
{
producerNode = newValue;
}
@SuppressWarnings("unchecked")
final LinkedQueueNode lvProducerNode()
{
return (LinkedQueueNode) UNSAFE.getObjectVolatile(this, P_NODE_OFFSET);
}
@SuppressWarnings("unchecked")
final boolean casProducerNode(LinkedQueueNode expect, LinkedQueueNode newValue)
{
return UNSAFE.compareAndSwapObject(this, P_NODE_OFFSET, expect, newValue);
}
final LinkedQueueNode lpProducerNode()
{
return producerNode;
}
}
abstract class BaseLinkedQueuePad1 extends BaseLinkedQueueProducerNodeRef
{
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
//$gen:ordered-fields
abstract class BaseLinkedQueueConsumerNodeRef extends BaseLinkedQueuePad1
{
private final static long C_NODE_OFFSET = fieldOffset(BaseLinkedQueueConsumerNodeRef.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;
}
}
abstract class BaseLinkedQueuePad2 extends BaseLinkedQueueConsumerNodeRef
{
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
}
/**
* 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 BaseLinkedQueue extends BaseLinkedQueuePad2
{
@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 (chaserNode != producerNode && // don't go passed producer node
chaserNode != null && // stop at last node
size < Integer.MAX_VALUE) // stop at max int
{
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()
{
return lvConsumerNode() == lvProducerNode();
}
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;
}
@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;
}
}