/*
* 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.
*
* Original License: https://github.com/JCTools/JCTools/blob/master/LICENSE
* Original location: https://github.com/JCTools/JCTools/blob/master/jctools-core/src/main/java/org/jctools/queues/atomic/BaseLinkedQueue.java
*/
package rx.internal.util.unsafe;
import static rx.internal.util.unsafe.
UnsafeAccess.
UNSAFE;
import java.util.*;
import rx.internal.util.
SuppressAnimalSniffer;
import rx.internal.util.atomic.
LinkedQueueNode;
abstract class
BaseLinkedQueuePad0<E> extends
AbstractQueue<E> {
long
p00,
p01,
p02,
p03,
p04,
p05,
p06,
p07;
long
p30,
p31,
p32,
p33,
p34,
p35,
p36,
p37;
}
@
SuppressAnimalSniffer
abstract class
BaseLinkedQueueProducerNodeRef<E> extends
BaseLinkedQueuePad0<E> {
protected final static long
P_NODE_OFFSET =
UnsafeAccess.
addressOf(
BaseLinkedQueueProducerNodeRef.class, "producerNode");
protected
LinkedQueueNode<E>
producerNode;
protected final void
spProducerNode(
LinkedQueueNode<E>
node) {
producerNode =
node;
}
@
SuppressWarnings("unchecked")
protected final
LinkedQueueNode<E>
lvProducerNode() {
return (
LinkedQueueNode<E>)
UNSAFE.
getObjectVolatile(this,
P_NODE_OFFSET);
}
protected final
LinkedQueueNode<E>
lpProducerNode() {
return
producerNode;
}
}
abstract class
BaseLinkedQueuePad1<E> extends
BaseLinkedQueueProducerNodeRef<E> {
long
p00,
p01,
p02,
p03,
p04,
p05,
p06,
p07;
long
p30,
p31,
p32,
p33,
p34,
p35,
p36,
p37;
}
@
SuppressAnimalSniffer
abstract class
BaseLinkedQueueConsumerNodeRef<E> extends
BaseLinkedQueuePad1<E> {
protected final static long
C_NODE_OFFSET =
UnsafeAccess.
addressOf(
BaseLinkedQueueConsumerNodeRef.class, "consumerNode");
protected
LinkedQueueNode<E>
consumerNode;
protected final void
spConsumerNode(
LinkedQueueNode<E>
node) {
consumerNode =
node;
}
@
SuppressWarnings("unchecked")
protected final
LinkedQueueNode<E>
lvConsumerNode() {
return (
LinkedQueueNode<E>)
UNSAFE.
getObjectVolatile(this,
C_NODE_OFFSET);
}
protected final
LinkedQueueNode<E>
lpConsumerNode() {
return
consumerNode;
}
}
/**
* A base data structure for concurrent linked queues.
*
* @author nitsanw
*
* @param <E> the element type
*/
@
SuppressAnimalSniffer
abstract class
BaseLinkedQueue<E> extends
BaseLinkedQueueConsumerNodeRef<E> {
long
p00,
p01,
p02,
p03,
p04,
p05,
p06,
p07;
long
p30,
p31,
p32,
p33,
p34,
p35,
p36,
p37;
@
Override
public final
Iterator<E>
iterator() {
throw new
UnsupportedOperationException();
}
/**
* {@inheritDoc} <br>
* <p>
* IMPLEMENTATION NOTES:<br>
* This is an O(n) operation as we run through all the nodes and count them.<br>
*
* @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). This will lead to an infinite loop below.
LinkedQueueNode<E>
chaserNode =
lvConsumerNode();
final
LinkedQueueNode<E>
producerNode =
lvProducerNode();
int
size = 0;
// must chase the nodes all the way to the producer node, but there's no need to chase a moving target.
while (
chaserNode !=
producerNode &&
size <
Integer.
MAX_VALUE) {
LinkedQueueNode<E>
next;
while ((
next =
chaserNode.
lvNext()) == null) { } // NOPMD
chaserNode =
next;
size++;
}
return
size;
}
/**
* {@inheritDoc} <br>
* <p>
* IMPLEMENTATION NOTES:<br>
* 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 final boolean
isEmpty() {
return
lvConsumerNode() ==
lvProducerNode();
}
}