/
AtomicReferenceArrayQueue.java
159 lines (138 loc) · 4.49 KB
/
AtomicReferenceArrayQueue.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
/*
* 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.atomic;
import org.jctools.queues.IndexedQueueSizeUtil;
import org.jctools.queues.IndexedQueueSizeUtil.IndexedQueue;
import org.jctools.queues.MessagePassingQueue;
import org.jctools.queues.QueueProgressIndicators;
import org.jctools.queues.SupportsIterator;
import org.jctools.util.InternalAPI;
import org.jctools.util.Pow2;
import java.util.AbstractQueue;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.atomic.AtomicReferenceArray;
import static org.jctools.queues.atomic.AtomicQueueUtil.*;
@InternalAPI
public abstract class AtomicReferenceArrayQueue<E> extends AbstractQueue<E> implements IndexedQueue, QueueProgressIndicators, MessagePassingQueue<E>, SupportsIterator
{
protected final AtomicReferenceArray<E> buffer;
protected final int mask;
public AtomicReferenceArrayQueue(int capacity)
{
int actualCapacity = Pow2.roundToPowerOfTwo(capacity);
this.mask = actualCapacity - 1;
this.buffer = new AtomicReferenceArray<E>(actualCapacity);
}
@Override
public String toString()
{
return this.getClass().getName();
}
@Override
public void clear()
{
while (poll() != null)
{
// toss it away
}
}
@Override
public final int capacity()
{
return (int) (mask + 1);
}
/**
* {@inheritDoc}
* <p>
*/
@Override
public final int size()
{
return IndexedQueueSizeUtil.size(this, IndexedQueueSizeUtil.PLAIN_DIVISOR);
}
@Override
public final boolean isEmpty()
{
return IndexedQueueSizeUtil.isEmpty(this);
}
@Override
public final long currentProducerIndex()
{
return lvProducerIndex();
}
@Override
public final long currentConsumerIndex()
{
return lvConsumerIndex();
}
/**
* Get an iterator for this queue. This method is thread safe.
* <p>
* The iterator provides a best-effort snapshot of the elements in the queue.
* The returned iterator is not guaranteed to return elements in queue order,
* and races with the consumer thread may cause gaps in the sequence of returned elements.
* Like {link #relaxedPoll}, the iterator may not immediately return newly inserted elements.
*
* @return The iterator.
*/
@Override
public final Iterator<E> iterator() {
final long cIndex = lvConsumerIndex();
final long pIndex = lvProducerIndex();
return new WeakIterator(cIndex, pIndex, mask, buffer);
}
private static class WeakIterator<E> implements Iterator<E> {
private final long pIndex;
private final int mask;
private final AtomicReferenceArray<E> buffer;
private long nextIndex;
private E nextElement;
WeakIterator(long cIndex, long pIndex, int mask, AtomicReferenceArray<E> buffer) {
this.nextIndex = cIndex;
this.pIndex = pIndex;
this.mask = mask;
this.buffer = buffer;
nextElement = getNext();
}
@Override
public void remove() {
throw new UnsupportedOperationException("remove");
}
@Override
public boolean hasNext() {
return nextElement != null;
}
@Override
public E next() {
final E e = nextElement;
if (e == null)
throw new NoSuchElementException();
nextElement = getNext();
return e;
}
private E getNext() {
final int mask = this.mask;
final AtomicReferenceArray<E> buffer = this.buffer;
while (nextIndex < pIndex) {
int offset = calcCircularRefElementOffset(nextIndex++, mask);
E e = lvRefElement(buffer, offset);
if (e != null) {
return e;
}
}
return null;
}
}
}