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dl |
1.2 |
/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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dl |
1.38 |
* Expert Group and released to the public domain, as explained at |
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jsr166 |
1.78 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
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dl |
1.2 |
*/ |
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tim |
1.1 |
package java.util.concurrent; |
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jsr166 |
1.110 |
|
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import java.lang.ref.WeakReference; |
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jsr166 |
1.125 |
import java.util.AbstractQueue; |
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jsr166 |
1.120 |
import java.util.Arrays; |
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jsr166 |
1.85 |
import java.util.Collection; |
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import java.util.Iterator; |
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import java.util.NoSuchElementException; |
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jsr166 |
1.119 |
import java.util.Objects; |
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jsr166 |
1.110 |
import java.util.Spliterator; |
17 |
dl |
1.102 |
import java.util.Spliterators; |
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jsr166 |
1.110 |
import java.util.concurrent.locks.Condition; |
19 |
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import java.util.concurrent.locks.ReentrantLock; |
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jsr166 |
1.127 |
import java.util.function.Consumer; |
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jsr166 |
1.135 |
import java.util.function.Predicate; |
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tim |
1.1 |
|
23 |
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/** |
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dl |
1.25 |
* A bounded {@linkplain BlockingQueue blocking queue} backed by an |
25 |
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* array. This queue orders elements FIFO (first-in-first-out). The |
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* <em>head</em> of the queue is that element that has been on the |
27 |
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* queue the longest time. The <em>tail</em> of the queue is that |
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* element that has been on the queue the shortest time. New elements |
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* are inserted at the tail of the queue, and the queue retrieval |
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* operations obtain elements at the head of the queue. |
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dholmes |
1.13 |
* |
32 |
dl |
1.40 |
* <p>This is a classic "bounded buffer", in which a |
33 |
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* fixed-sized array holds elements inserted by producers and |
34 |
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* extracted by consumers. Once created, the capacity cannot be |
35 |
jsr166 |
1.69 |
* changed. Attempts to {@code put} an element into a full queue |
36 |
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* will result in the operation blocking; attempts to {@code take} an |
37 |
dl |
1.40 |
* element from an empty queue will similarly block. |
38 |
dl |
1.11 |
* |
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jsr166 |
1.72 |
* <p>This class supports an optional fairness policy for ordering |
40 |
dl |
1.42 |
* waiting producer and consumer threads. By default, this ordering |
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* is not guaranteed. However, a queue constructed with fairness set |
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jsr166 |
1.69 |
* to {@code true} grants threads access in FIFO order. Fairness |
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dl |
1.42 |
* generally decreases throughput but reduces variability and avoids |
44 |
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* starvation. |
45 |
brian |
1.7 |
* |
46 |
dl |
1.43 |
* <p>This class and its iterator implement all of the |
47 |
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* <em>optional</em> methods of the {@link Collection} and {@link |
48 |
jsr166 |
1.47 |
* Iterator} interfaces. |
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dl |
1.26 |
* |
50 |
dl |
1.41 |
* <p>This class is a member of the |
51 |
jsr166 |
1.54 |
* <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
52 |
dl |
1.41 |
* Java Collections Framework</a>. |
53 |
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* |
54 |
dl |
1.8 |
* @since 1.5 |
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* @author Doug Lea |
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jsr166 |
1.109 |
* @param <E> the type of elements held in this queue |
57 |
dl |
1.8 |
*/ |
58 |
dl |
1.5 |
public class ArrayBlockingQueue<E> extends AbstractQueue<E> |
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tim |
1.1 |
implements BlockingQueue<E>, java.io.Serializable { |
60 |
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jsr166 |
1.138 |
/* |
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* Much of the implementation mechanics, especially the unusual |
63 |
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* nested loops, are shared and co-maintained with ArrayDeque. |
64 |
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*/ |
65 |
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|
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dl |
1.36 |
/** |
67 |
dl |
1.42 |
* Serialization ID. This class relies on default serialization |
68 |
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* even for the items array, which is default-serialized, even if |
69 |
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* it is empty. Otherwise it could not be declared final, which is |
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dl |
1.36 |
* necessary here. |
71 |
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*/ |
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private static final long serialVersionUID = -817911632652898426L; |
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|
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jsr166 |
1.73 |
/** The queued items */ |
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jsr166 |
1.68 |
final Object[] items; |
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jsr166 |
1.73 |
|
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/** items index for next take, poll, peek or remove */ |
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jsr166 |
1.58 |
int takeIndex; |
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jsr166 |
1.73 |
|
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/** items index for next put, offer, or add */ |
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jsr166 |
1.58 |
int putIndex; |
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jsr166 |
1.73 |
|
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/** Number of elements in the queue */ |
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jsr166 |
1.59 |
int count; |
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tim |
1.12 |
|
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dl |
1.5 |
/* |
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dl |
1.36 |
* Concurrency control uses the classic two-condition algorithm |
88 |
dl |
1.5 |
* found in any textbook. |
89 |
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*/ |
90 |
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|
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dl |
1.11 |
/** Main lock guarding all access */ |
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jsr166 |
1.58 |
final ReentrantLock lock; |
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jsr166 |
1.85 |
|
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dholmes |
1.13 |
/** Condition for waiting takes */ |
95 |
dl |
1.37 |
private final Condition notEmpty; |
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jsr166 |
1.85 |
|
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dl |
1.35 |
/** Condition for waiting puts */ |
98 |
dl |
1.37 |
private final Condition notFull; |
99 |
dl |
1.5 |
|
100 |
jsr166 |
1.89 |
/** |
101 |
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* Shared state for currently active iterators, or null if there |
102 |
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* are known not to be any. Allows queue operations to update |
103 |
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* iterator state. |
104 |
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*/ |
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jsr166 |
1.121 |
transient Itrs itrs; |
106 |
jsr166 |
1.89 |
|
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dl |
1.5 |
// Internal helper methods |
108 |
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109 |
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/** |
110 |
jsr166 |
1.135 |
* Increments i, mod modulus. |
111 |
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* Precondition and postcondition: 0 <= i < modulus. |
112 |
jsr166 |
1.71 |
*/ |
113 |
jsr166 |
1.135 |
static final int inc(int i, int modulus) { |
114 |
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if (++i >= modulus) i = 0; |
115 |
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return i; |
116 |
jsr166 |
1.71 |
} |
117 |
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|
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jsr166 |
1.68 |
/** |
119 |
jsr166 |
1.128 |
* Decrements i, mod modulus. |
120 |
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* Precondition and postcondition: 0 <= i < modulus. |
121 |
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*/ |
122 |
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static final int dec(int i, int modulus) { |
123 |
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if (--i < 0) i = modulus - 1; |
124 |
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return i; |
125 |
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} |
126 |
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127 |
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/** |
128 |
jsr166 |
1.68 |
* Returns item at index i. |
129 |
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*/ |
130 |
jsr166 |
1.96 |
@SuppressWarnings("unchecked") |
131 |
jsr166 |
1.68 |
final E itemAt(int i) { |
132 |
jsr166 |
1.96 |
return (E) items[i]; |
133 |
jsr166 |
1.68 |
} |
134 |
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|
135 |
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/** |
136 |
jsr166 |
1.128 |
* Returns element at array index i. |
137 |
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* This is a slight abuse of generics, accepted by javac. |
138 |
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*/ |
139 |
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@SuppressWarnings("unchecked") |
140 |
jsr166 |
1.132 |
static <E> E itemAt(Object[] items, int i) { |
141 |
jsr166 |
1.131 |
return (E) items[i]; |
142 |
jsr166 |
1.128 |
} |
143 |
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144 |
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/** |
145 |
jsr166 |
1.47 |
* Inserts element at current put position, advances, and signals. |
146 |
dl |
1.9 |
* Call only when holding lock. |
147 |
dl |
1.5 |
*/ |
148 |
jsr166 |
1.141 |
private void enqueue(E e) { |
149 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
150 |
jsr166 |
1.95 |
// assert lock.getHoldCount() == 1; |
151 |
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// assert items[putIndex] == null; |
152 |
dl |
1.100 |
final Object[] items = this.items; |
153 |
jsr166 |
1.141 |
items[putIndex] = e; |
154 |
jsr166 |
1.116 |
if (++putIndex == items.length) putIndex = 0; |
155 |
jsr166 |
1.89 |
count++; |
156 |
dl |
1.9 |
notEmpty.signal(); |
157 |
jsr166 |
1.128 |
// checkInvariants(); |
158 |
tim |
1.1 |
} |
159 |
tim |
1.12 |
|
160 |
dl |
1.5 |
/** |
161 |
jsr166 |
1.47 |
* Extracts element at current take position, advances, and signals. |
162 |
dl |
1.9 |
* Call only when holding lock. |
163 |
dl |
1.5 |
*/ |
164 |
jsr166 |
1.88 |
private E dequeue() { |
165 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
166 |
jsr166 |
1.95 |
// assert lock.getHoldCount() == 1; |
167 |
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// assert items[takeIndex] != null; |
168 |
jsr166 |
1.68 |
final Object[] items = this.items; |
169 |
jsr166 |
1.97 |
@SuppressWarnings("unchecked") |
170 |
jsr166 |
1.141 |
E e = (E) items[takeIndex]; |
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dl |
1.5 |
items[takeIndex] = null; |
172 |
jsr166 |
1.116 |
if (++takeIndex == items.length) takeIndex = 0; |
173 |
jsr166 |
1.89 |
count--; |
174 |
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if (itrs != null) |
175 |
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itrs.elementDequeued(); |
176 |
dl |
1.9 |
notFull.signal(); |
177 |
jsr166 |
1.128 |
// checkInvariants(); |
178 |
jsr166 |
1.141 |
return e; |
179 |
dl |
1.5 |
} |
180 |
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181 |
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/** |
182 |
jsr166 |
1.90 |
* Deletes item at array index removeIndex. |
183 |
jsr166 |
1.89 |
* Utility for remove(Object) and iterator.remove. |
184 |
dl |
1.9 |
* Call only when holding lock. |
185 |
dl |
1.5 |
*/ |
186 |
jsr166 |
1.90 |
void removeAt(final int removeIndex) { |
187 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
188 |
jsr166 |
1.95 |
// assert lock.getHoldCount() == 1; |
189 |
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// assert items[removeIndex] != null; |
190 |
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// assert removeIndex >= 0 && removeIndex < items.length; |
191 |
jsr166 |
1.68 |
final Object[] items = this.items; |
192 |
jsr166 |
1.90 |
if (removeIndex == takeIndex) { |
193 |
jsr166 |
1.89 |
// removing front item; just advance |
194 |
dl |
1.9 |
items[takeIndex] = null; |
195 |
jsr166 |
1.116 |
if (++takeIndex == items.length) takeIndex = 0; |
196 |
jsr166 |
1.90 |
count--; |
197 |
jsr166 |
1.89 |
if (itrs != null) |
198 |
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itrs.elementDequeued(); |
199 |
tim |
1.23 |
} else { |
200 |
jsr166 |
1.89 |
// an "interior" remove |
201 |
jsr166 |
1.90 |
|
202 |
dl |
1.9 |
// slide over all others up through putIndex. |
203 |
jsr166 |
1.115 |
for (int i = removeIndex, putIndex = this.putIndex;;) { |
204 |
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int pred = i; |
205 |
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if (++i == items.length) i = 0; |
206 |
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if (i == putIndex) { |
207 |
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items[pred] = null; |
208 |
|
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this.putIndex = pred; |
209 |
dl |
1.9 |
break; |
210 |
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} |
211 |
jsr166 |
1.115 |
items[pred] = items[i]; |
212 |
dl |
1.5 |
} |
213 |
jsr166 |
1.90 |
count--; |
214 |
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if (itrs != null) |
215 |
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itrs.removedAt(removeIndex); |
216 |
dl |
1.5 |
} |
217 |
dl |
1.9 |
notFull.signal(); |
218 |
jsr166 |
1.134 |
// checkInvariants(); |
219 |
tim |
1.1 |
} |
220 |
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|
221 |
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/** |
222 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
223 |
dholmes |
1.13 |
* capacity and default access policy. |
224 |
jsr166 |
1.50 |
* |
225 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
226 |
jsr166 |
1.69 |
* @throws IllegalArgumentException if {@code capacity < 1} |
227 |
dl |
1.5 |
*/ |
228 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity) { |
229 |
dl |
1.36 |
this(capacity, false); |
230 |
dl |
1.5 |
} |
231 |
dl |
1.2 |
|
232 |
dl |
1.5 |
/** |
233 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
234 |
dholmes |
1.13 |
* capacity and the specified access policy. |
235 |
jsr166 |
1.50 |
* |
236 |
dholmes |
1.13 |
* @param capacity the capacity of this queue |
237 |
jsr166 |
1.69 |
* @param fair if {@code true} then queue accesses for threads blocked |
238 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
239 |
jsr166 |
1.69 |
* if {@code false} the access order is unspecified. |
240 |
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* @throws IllegalArgumentException if {@code capacity < 1} |
241 |
dl |
1.11 |
*/ |
242 |
dholmes |
1.13 |
public ArrayBlockingQueue(int capacity, boolean fair) { |
243 |
dl |
1.36 |
if (capacity <= 0) |
244 |
|
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throw new IllegalArgumentException(); |
245 |
jsr166 |
1.68 |
this.items = new Object[capacity]; |
246 |
dl |
1.36 |
lock = new ReentrantLock(fair); |
247 |
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notEmpty = lock.newCondition(); |
248 |
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notFull = lock.newCondition(); |
249 |
dl |
1.5 |
} |
250 |
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|
251 |
dholmes |
1.16 |
/** |
252 |
jsr166 |
1.69 |
* Creates an {@code ArrayBlockingQueue} with the given (fixed) |
253 |
dholmes |
1.21 |
* capacity, the specified access policy and initially containing the |
254 |
tim |
1.17 |
* elements of the given collection, |
255 |
dholmes |
1.16 |
* added in traversal order of the collection's iterator. |
256 |
jsr166 |
1.50 |
* |
257 |
dholmes |
1.16 |
* @param capacity the capacity of this queue |
258 |
jsr166 |
1.69 |
* @param fair if {@code true} then queue accesses for threads blocked |
259 |
jsr166 |
1.50 |
* on insertion or removal, are processed in FIFO order; |
260 |
jsr166 |
1.69 |
* if {@code false} the access order is unspecified. |
261 |
dholmes |
1.16 |
* @param c the collection of elements to initially contain |
262 |
jsr166 |
1.69 |
* @throws IllegalArgumentException if {@code capacity} is less than |
263 |
|
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* {@code c.size()}, or less than 1. |
264 |
jsr166 |
1.50 |
* @throws NullPointerException if the specified collection or any |
265 |
|
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* of its elements are null |
266 |
dholmes |
1.16 |
*/ |
267 |
tim |
1.20 |
public ArrayBlockingQueue(int capacity, boolean fair, |
268 |
dholmes |
1.18 |
Collection<? extends E> c) { |
269 |
dl |
1.36 |
this(capacity, fair); |
270 |
dholmes |
1.16 |
|
271 |
jsr166 |
1.68 |
final ReentrantLock lock = this.lock; |
272 |
|
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lock.lock(); // Lock only for visibility, not mutual exclusion |
273 |
|
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try { |
274 |
jsr166 |
1.133 |
final Object[] items = this.items; |
275 |
jsr166 |
1.68 |
int i = 0; |
276 |
|
|
try { |
277 |
jsr166 |
1.119 |
for (E e : c) |
278 |
|
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items[i++] = Objects.requireNonNull(e); |
279 |
jsr166 |
1.68 |
} catch (ArrayIndexOutOfBoundsException ex) { |
280 |
|
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throw new IllegalArgumentException(); |
281 |
|
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} |
282 |
|
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count = i; |
283 |
|
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putIndex = (i == capacity) ? 0 : i; |
284 |
jsr166 |
1.134 |
// checkInvariants(); |
285 |
jsr166 |
1.68 |
} finally { |
286 |
|
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lock.unlock(); |
287 |
|
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} |
288 |
dholmes |
1.16 |
} |
289 |
dl |
1.2 |
|
290 |
dholmes |
1.13 |
/** |
291 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue if it is |
292 |
|
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* possible to do so immediately without exceeding the queue's capacity, |
293 |
jsr166 |
1.69 |
* returning {@code true} upon success and throwing an |
294 |
|
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* {@code IllegalStateException} if this queue is full. |
295 |
dl |
1.25 |
* |
296 |
jsr166 |
1.50 |
* @param e the element to add |
297 |
jsr166 |
1.69 |
* @return {@code true} (as specified by {@link Collection#add}) |
298 |
jsr166 |
1.50 |
* @throws IllegalStateException if this queue is full |
299 |
|
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* @throws NullPointerException if the specified element is null |
300 |
|
|
*/ |
301 |
|
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public boolean add(E e) { |
302 |
jsr166 |
1.56 |
return super.add(e); |
303 |
jsr166 |
1.50 |
} |
304 |
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|
305 |
|
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/** |
306 |
|
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* Inserts the specified element at the tail of this queue if it is |
307 |
|
|
* possible to do so immediately without exceeding the queue's capacity, |
308 |
jsr166 |
1.69 |
* returning {@code true} upon success and {@code false} if this queue |
309 |
jsr166 |
1.50 |
* is full. This method is generally preferable to method {@link #add}, |
310 |
|
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* which can fail to insert an element only by throwing an exception. |
311 |
|
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* |
312 |
|
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* @throws NullPointerException if the specified element is null |
313 |
dholmes |
1.13 |
*/ |
314 |
jsr166 |
1.49 |
public boolean offer(E e) { |
315 |
jsr166 |
1.119 |
Objects.requireNonNull(e); |
316 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
317 |
dl |
1.5 |
lock.lock(); |
318 |
|
|
try { |
319 |
jsr166 |
1.59 |
if (count == items.length) |
320 |
dl |
1.2 |
return false; |
321 |
dl |
1.5 |
else { |
322 |
jsr166 |
1.88 |
enqueue(e); |
323 |
dl |
1.5 |
return true; |
324 |
|
|
} |
325 |
tim |
1.23 |
} finally { |
326 |
tim |
1.12 |
lock.unlock(); |
327 |
dl |
1.2 |
} |
328 |
dl |
1.5 |
} |
329 |
dl |
1.2 |
|
330 |
dholmes |
1.13 |
/** |
331 |
jsr166 |
1.50 |
* Inserts the specified element at the tail of this queue, waiting |
332 |
|
|
* for space to become available if the queue is full. |
333 |
|
|
* |
334 |
|
|
* @throws InterruptedException {@inheritDoc} |
335 |
|
|
* @throws NullPointerException {@inheritDoc} |
336 |
|
|
*/ |
337 |
|
|
public void put(E e) throws InterruptedException { |
338 |
jsr166 |
1.119 |
Objects.requireNonNull(e); |
339 |
jsr166 |
1.50 |
final ReentrantLock lock = this.lock; |
340 |
|
|
lock.lockInterruptibly(); |
341 |
|
|
try { |
342 |
jsr166 |
1.59 |
while (count == items.length) |
343 |
jsr166 |
1.58 |
notFull.await(); |
344 |
jsr166 |
1.88 |
enqueue(e); |
345 |
jsr166 |
1.50 |
} finally { |
346 |
|
|
lock.unlock(); |
347 |
|
|
} |
348 |
|
|
} |
349 |
|
|
|
350 |
|
|
/** |
351 |
|
|
* Inserts the specified element at the tail of this queue, waiting |
352 |
|
|
* up to the specified wait time for space to become available if |
353 |
|
|
* the queue is full. |
354 |
|
|
* |
355 |
|
|
* @throws InterruptedException {@inheritDoc} |
356 |
|
|
* @throws NullPointerException {@inheritDoc} |
357 |
brian |
1.7 |
*/ |
358 |
jsr166 |
1.49 |
public boolean offer(E e, long timeout, TimeUnit unit) |
359 |
dholmes |
1.13 |
throws InterruptedException { |
360 |
dl |
1.2 |
|
361 |
jsr166 |
1.119 |
Objects.requireNonNull(e); |
362 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
363 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
364 |
dl |
1.5 |
lock.lockInterruptibly(); |
365 |
|
|
try { |
366 |
jsr166 |
1.59 |
while (count == items.length) { |
367 |
jsr166 |
1.126 |
if (nanos <= 0L) |
368 |
dl |
1.5 |
return false; |
369 |
jsr166 |
1.58 |
nanos = notFull.awaitNanos(nanos); |
370 |
dl |
1.5 |
} |
371 |
jsr166 |
1.88 |
enqueue(e); |
372 |
jsr166 |
1.58 |
return true; |
373 |
tim |
1.23 |
} finally { |
374 |
jsr166 |
1.134 |
// checkInvariants(); |
375 |
dl |
1.5 |
lock.unlock(); |
376 |
dl |
1.2 |
} |
377 |
dl |
1.5 |
} |
378 |
dl |
1.2 |
|
379 |
dholmes |
1.13 |
public E poll() { |
380 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
381 |
dholmes |
1.13 |
lock.lock(); |
382 |
|
|
try { |
383 |
jsr166 |
1.88 |
return (count == 0) ? null : dequeue(); |
384 |
tim |
1.23 |
} finally { |
385 |
tim |
1.15 |
lock.unlock(); |
386 |
dholmes |
1.13 |
} |
387 |
|
|
} |
388 |
|
|
|
389 |
jsr166 |
1.50 |
public E take() throws InterruptedException { |
390 |
|
|
final ReentrantLock lock = this.lock; |
391 |
|
|
lock.lockInterruptibly(); |
392 |
|
|
try { |
393 |
jsr166 |
1.59 |
while (count == 0) |
394 |
jsr166 |
1.58 |
notEmpty.await(); |
395 |
jsr166 |
1.88 |
return dequeue(); |
396 |
jsr166 |
1.50 |
} finally { |
397 |
|
|
lock.unlock(); |
398 |
|
|
} |
399 |
|
|
} |
400 |
|
|
|
401 |
dl |
1.5 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException { |
402 |
jsr166 |
1.56 |
long nanos = unit.toNanos(timeout); |
403 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
404 |
dl |
1.5 |
lock.lockInterruptibly(); |
405 |
|
|
try { |
406 |
jsr166 |
1.59 |
while (count == 0) { |
407 |
jsr166 |
1.126 |
if (nanos <= 0L) |
408 |
dl |
1.5 |
return null; |
409 |
jsr166 |
1.58 |
nanos = notEmpty.awaitNanos(nanos); |
410 |
dl |
1.2 |
} |
411 |
jsr166 |
1.88 |
return dequeue(); |
412 |
tim |
1.23 |
} finally { |
413 |
jsr166 |
1.131 |
// checkInvariants(); |
414 |
dl |
1.5 |
lock.unlock(); |
415 |
|
|
} |
416 |
|
|
} |
417 |
dl |
1.2 |
|
418 |
dholmes |
1.13 |
public E peek() { |
419 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
420 |
dholmes |
1.13 |
lock.lock(); |
421 |
|
|
try { |
422 |
jsr166 |
1.99 |
return itemAt(takeIndex); // null when queue is empty |
423 |
tim |
1.23 |
} finally { |
424 |
dholmes |
1.13 |
lock.unlock(); |
425 |
|
|
} |
426 |
|
|
} |
427 |
|
|
|
428 |
|
|
// this doc comment is overridden to remove the reference to collections |
429 |
|
|
// greater in size than Integer.MAX_VALUE |
430 |
tim |
1.15 |
/** |
431 |
dl |
1.25 |
* Returns the number of elements in this queue. |
432 |
|
|
* |
433 |
jsr166 |
1.50 |
* @return the number of elements in this queue |
434 |
dholmes |
1.13 |
*/ |
435 |
|
|
public int size() { |
436 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
437 |
dholmes |
1.13 |
lock.lock(); |
438 |
|
|
try { |
439 |
|
|
return count; |
440 |
tim |
1.23 |
} finally { |
441 |
dholmes |
1.13 |
lock.unlock(); |
442 |
|
|
} |
443 |
|
|
} |
444 |
|
|
|
445 |
|
|
// this doc comment is a modified copy of the inherited doc comment, |
446 |
|
|
// without the reference to unlimited queues. |
447 |
tim |
1.15 |
/** |
448 |
jsr166 |
1.48 |
* Returns the number of additional elements that this queue can ideally |
449 |
|
|
* (in the absence of memory or resource constraints) accept without |
450 |
dholmes |
1.13 |
* blocking. This is always equal to the initial capacity of this queue |
451 |
jsr166 |
1.69 |
* less the current {@code size} of this queue. |
452 |
jsr166 |
1.48 |
* |
453 |
|
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
454 |
jsr166 |
1.69 |
* an element will succeed by inspecting {@code remainingCapacity} |
455 |
jsr166 |
1.48 |
* because it may be the case that another thread is about to |
456 |
jsr166 |
1.50 |
* insert or remove an element. |
457 |
dholmes |
1.13 |
*/ |
458 |
|
|
public int remainingCapacity() { |
459 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
460 |
dholmes |
1.13 |
lock.lock(); |
461 |
|
|
try { |
462 |
|
|
return items.length - count; |
463 |
tim |
1.23 |
} finally { |
464 |
dholmes |
1.13 |
lock.unlock(); |
465 |
|
|
} |
466 |
|
|
} |
467 |
|
|
|
468 |
jsr166 |
1.50 |
/** |
469 |
|
|
* Removes a single instance of the specified element from this queue, |
470 |
jsr166 |
1.69 |
* if it is present. More formally, removes an element {@code e} such |
471 |
|
|
* that {@code o.equals(e)}, if this queue contains one or more such |
472 |
jsr166 |
1.50 |
* elements. |
473 |
jsr166 |
1.69 |
* Returns {@code true} if this queue contained the specified element |
474 |
jsr166 |
1.50 |
* (or equivalently, if this queue changed as a result of the call). |
475 |
|
|
* |
476 |
jsr166 |
1.64 |
* <p>Removal of interior elements in circular array based queues |
477 |
dl |
1.60 |
* is an intrinsically slow and disruptive operation, so should |
478 |
|
|
* be undertaken only in exceptional circumstances, ideally |
479 |
|
|
* only when the queue is known not to be accessible by other |
480 |
|
|
* threads. |
481 |
|
|
* |
482 |
jsr166 |
1.50 |
* @param o element to be removed from this queue, if present |
483 |
jsr166 |
1.69 |
* @return {@code true} if this queue changed as a result of the call |
484 |
jsr166 |
1.50 |
*/ |
485 |
|
|
public boolean remove(Object o) { |
486 |
|
|
if (o == null) return false; |
487 |
|
|
final ReentrantLock lock = this.lock; |
488 |
|
|
lock.lock(); |
489 |
|
|
try { |
490 |
jsr166 |
1.86 |
if (count > 0) { |
491 |
jsr166 |
1.114 |
final Object[] items = this.items; |
492 |
jsr166 |
1.130 |
for (int i = takeIndex, end = putIndex, |
493 |
|
|
to = (i < end) ? end : items.length; |
494 |
|
|
; i = 0, to = end) { |
495 |
|
|
for (; i < to; i++) |
496 |
|
|
if (o.equals(items[i])) { |
497 |
|
|
removeAt(i); |
498 |
|
|
return true; |
499 |
|
|
} |
500 |
|
|
if (to == end) break; |
501 |
|
|
} |
502 |
jsr166 |
1.50 |
} |
503 |
jsr166 |
1.68 |
return false; |
504 |
jsr166 |
1.50 |
} finally { |
505 |
jsr166 |
1.131 |
// checkInvariants(); |
506 |
jsr166 |
1.50 |
lock.unlock(); |
507 |
|
|
} |
508 |
|
|
} |
509 |
dholmes |
1.13 |
|
510 |
jsr166 |
1.50 |
/** |
511 |
jsr166 |
1.69 |
* Returns {@code true} if this queue contains the specified element. |
512 |
|
|
* More formally, returns {@code true} if and only if this queue contains |
513 |
|
|
* at least one element {@code e} such that {@code o.equals(e)}. |
514 |
jsr166 |
1.50 |
* |
515 |
|
|
* @param o object to be checked for containment in this queue |
516 |
jsr166 |
1.69 |
* @return {@code true} if this queue contains the specified element |
517 |
jsr166 |
1.50 |
*/ |
518 |
dholmes |
1.21 |
public boolean contains(Object o) { |
519 |
|
|
if (o == null) return false; |
520 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
521 |
dl |
1.5 |
lock.lock(); |
522 |
|
|
try { |
523 |
jsr166 |
1.86 |
if (count > 0) { |
524 |
jsr166 |
1.114 |
final Object[] items = this.items; |
525 |
jsr166 |
1.129 |
for (int i = takeIndex, end = putIndex, |
526 |
|
|
to = (i < end) ? end : items.length; |
527 |
|
|
; i = 0, to = end) { |
528 |
|
|
for (; i < to; i++) |
529 |
|
|
if (o.equals(items[i])) |
530 |
|
|
return true; |
531 |
|
|
if (to == end) break; |
532 |
|
|
} |
533 |
jsr166 |
1.86 |
} |
534 |
dl |
1.2 |
return false; |
535 |
tim |
1.23 |
} finally { |
536 |
jsr166 |
1.131 |
// checkInvariants(); |
537 |
dl |
1.5 |
lock.unlock(); |
538 |
|
|
} |
539 |
|
|
} |
540 |
brian |
1.7 |
|
541 |
jsr166 |
1.50 |
/** |
542 |
|
|
* Returns an array containing all of the elements in this queue, in |
543 |
|
|
* proper sequence. |
544 |
|
|
* |
545 |
|
|
* <p>The returned array will be "safe" in that no references to it are |
546 |
|
|
* maintained by this queue. (In other words, this method must allocate |
547 |
|
|
* a new array). The caller is thus free to modify the returned array. |
548 |
jsr166 |
1.51 |
* |
549 |
jsr166 |
1.50 |
* <p>This method acts as bridge between array-based and collection-based |
550 |
|
|
* APIs. |
551 |
|
|
* |
552 |
|
|
* @return an array containing all of the elements in this queue |
553 |
|
|
*/ |
554 |
dl |
1.5 |
public Object[] toArray() { |
555 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
556 |
dl |
1.5 |
lock.lock(); |
557 |
|
|
try { |
558 |
jsr166 |
1.120 |
final Object[] items = this.items; |
559 |
|
|
final int end = takeIndex + count; |
560 |
|
|
final Object[] a = Arrays.copyOfRange(items, takeIndex, end); |
561 |
|
|
if (end != putIndex) |
562 |
|
|
System.arraycopy(items, 0, a, items.length - takeIndex, putIndex); |
563 |
|
|
return a; |
564 |
tim |
1.23 |
} finally { |
565 |
dl |
1.5 |
lock.unlock(); |
566 |
|
|
} |
567 |
|
|
} |
568 |
brian |
1.7 |
|
569 |
jsr166 |
1.50 |
/** |
570 |
|
|
* Returns an array containing all of the elements in this queue, in |
571 |
|
|
* proper sequence; the runtime type of the returned array is that of |
572 |
|
|
* the specified array. If the queue fits in the specified array, it |
573 |
|
|
* is returned therein. Otherwise, a new array is allocated with the |
574 |
|
|
* runtime type of the specified array and the size of this queue. |
575 |
|
|
* |
576 |
|
|
* <p>If this queue fits in the specified array with room to spare |
577 |
|
|
* (i.e., the array has more elements than this queue), the element in |
578 |
|
|
* the array immediately following the end of the queue is set to |
579 |
jsr166 |
1.69 |
* {@code null}. |
580 |
jsr166 |
1.50 |
* |
581 |
|
|
* <p>Like the {@link #toArray()} method, this method acts as bridge between |
582 |
|
|
* array-based and collection-based APIs. Further, this method allows |
583 |
|
|
* precise control over the runtime type of the output array, and may, |
584 |
|
|
* under certain circumstances, be used to save allocation costs. |
585 |
|
|
* |
586 |
jsr166 |
1.69 |
* <p>Suppose {@code x} is a queue known to contain only strings. |
587 |
jsr166 |
1.50 |
* The following code can be used to dump the queue into a newly |
588 |
jsr166 |
1.69 |
* allocated array of {@code String}: |
589 |
jsr166 |
1.50 |
* |
590 |
jsr166 |
1.117 |
* <pre> {@code String[] y = x.toArray(new String[0]);}</pre> |
591 |
jsr166 |
1.50 |
* |
592 |
jsr166 |
1.69 |
* Note that {@code toArray(new Object[0])} is identical in function to |
593 |
|
|
* {@code toArray()}. |
594 |
jsr166 |
1.50 |
* |
595 |
|
|
* @param a the array into which the elements of the queue are to |
596 |
|
|
* be stored, if it is big enough; otherwise, a new array of the |
597 |
|
|
* same runtime type is allocated for this purpose |
598 |
|
|
* @return an array containing all of the elements in this queue |
599 |
|
|
* @throws ArrayStoreException if the runtime type of the specified array |
600 |
|
|
* is not a supertype of the runtime type of every element in |
601 |
|
|
* this queue |
602 |
|
|
* @throws NullPointerException if the specified array is null |
603 |
|
|
*/ |
604 |
jsr166 |
1.68 |
@SuppressWarnings("unchecked") |
605 |
dl |
1.5 |
public <T> T[] toArray(T[] a) { |
606 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
607 |
dl |
1.5 |
lock.lock(); |
608 |
|
|
try { |
609 |
jsr166 |
1.120 |
final Object[] items = this.items; |
610 |
jsr166 |
1.68 |
final int count = this.count; |
611 |
jsr166 |
1.120 |
final int firstLeg = Math.min(items.length - takeIndex, count); |
612 |
|
|
if (a.length < count) { |
613 |
|
|
a = (T[]) Arrays.copyOfRange(items, takeIndex, takeIndex + count, |
614 |
|
|
a.getClass()); |
615 |
|
|
} else { |
616 |
|
|
System.arraycopy(items, takeIndex, a, 0, firstLeg); |
617 |
|
|
if (a.length > count) |
618 |
|
|
a[count] = null; |
619 |
|
|
} |
620 |
|
|
if (firstLeg < count) |
621 |
|
|
System.arraycopy(items, 0, a, firstLeg, putIndex); |
622 |
|
|
return a; |
623 |
tim |
1.23 |
} finally { |
624 |
dl |
1.5 |
lock.unlock(); |
625 |
|
|
} |
626 |
|
|
} |
627 |
dl |
1.6 |
|
628 |
|
|
public String toString() { |
629 |
jsr166 |
1.122 |
return Helpers.collectionToString(this); |
630 |
dl |
1.6 |
} |
631 |
tim |
1.12 |
|
632 |
dl |
1.44 |
/** |
633 |
|
|
* Atomically removes all of the elements from this queue. |
634 |
|
|
* The queue will be empty after this call returns. |
635 |
|
|
*/ |
636 |
dl |
1.30 |
public void clear() { |
637 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
638 |
dl |
1.30 |
lock.lock(); |
639 |
|
|
try { |
640 |
jsr166 |
1.131 |
int k; |
641 |
|
|
if ((k = count) > 0) { |
642 |
|
|
circularClear(items, takeIndex, putIndex); |
643 |
jsr166 |
1.86 |
takeIndex = putIndex; |
644 |
|
|
count = 0; |
645 |
jsr166 |
1.89 |
if (itrs != null) |
646 |
|
|
itrs.queueIsEmpty(); |
647 |
jsr166 |
1.86 |
for (; k > 0 && lock.hasWaiters(notFull); k--) |
648 |
|
|
notFull.signal(); |
649 |
|
|
} |
650 |
dl |
1.30 |
} finally { |
651 |
jsr166 |
1.131 |
// checkInvariants(); |
652 |
dl |
1.30 |
lock.unlock(); |
653 |
|
|
} |
654 |
|
|
} |
655 |
|
|
|
656 |
jsr166 |
1.50 |
/** |
657 |
jsr166 |
1.131 |
* Nulls out slots starting at array index i, upto index end. |
658 |
jsr166 |
1.142 |
* Condition i == end means "full" - the entire array is cleared. |
659 |
jsr166 |
1.131 |
*/ |
660 |
|
|
private static void circularClear(Object[] items, int i, int end) { |
661 |
jsr166 |
1.142 |
// assert 0 <= i && i < items.length; |
662 |
|
|
// assert 0 <= end && end < items.length; |
663 |
jsr166 |
1.131 |
for (int to = (i < end) ? end : items.length; |
664 |
|
|
; i = 0, to = end) { |
665 |
jsr166 |
1.142 |
for (; i < to; i++) items[i] = null; |
666 |
jsr166 |
1.131 |
if (to == end) break; |
667 |
|
|
} |
668 |
|
|
} |
669 |
|
|
|
670 |
|
|
/** |
671 |
jsr166 |
1.50 |
* @throws UnsupportedOperationException {@inheritDoc} |
672 |
|
|
* @throws ClassCastException {@inheritDoc} |
673 |
|
|
* @throws NullPointerException {@inheritDoc} |
674 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
675 |
|
|
*/ |
676 |
dl |
1.30 |
public int drainTo(Collection<? super E> c) { |
677 |
jsr166 |
1.81 |
return drainTo(c, Integer.MAX_VALUE); |
678 |
dl |
1.30 |
} |
679 |
|
|
|
680 |
jsr166 |
1.50 |
/** |
681 |
|
|
* @throws UnsupportedOperationException {@inheritDoc} |
682 |
|
|
* @throws ClassCastException {@inheritDoc} |
683 |
|
|
* @throws NullPointerException {@inheritDoc} |
684 |
|
|
* @throws IllegalArgumentException {@inheritDoc} |
685 |
|
|
*/ |
686 |
dl |
1.30 |
public int drainTo(Collection<? super E> c, int maxElements) { |
687 |
jsr166 |
1.119 |
Objects.requireNonNull(c); |
688 |
dl |
1.30 |
if (c == this) |
689 |
|
|
throw new IllegalArgumentException(); |
690 |
|
|
if (maxElements <= 0) |
691 |
|
|
return 0; |
692 |
jsr166 |
1.68 |
final Object[] items = this.items; |
693 |
dl |
1.36 |
final ReentrantLock lock = this.lock; |
694 |
dl |
1.30 |
lock.lock(); |
695 |
|
|
try { |
696 |
jsr166 |
1.82 |
int n = Math.min(maxElements, count); |
697 |
|
|
int take = takeIndex; |
698 |
|
|
int i = 0; |
699 |
|
|
try { |
700 |
|
|
while (i < n) { |
701 |
jsr166 |
1.97 |
@SuppressWarnings("unchecked") |
702 |
jsr166 |
1.141 |
E e = (E) items[take]; |
703 |
|
|
c.add(e); |
704 |
jsr166 |
1.82 |
items[take] = null; |
705 |
jsr166 |
1.116 |
if (++take == items.length) take = 0; |
706 |
jsr166 |
1.86 |
i++; |
707 |
jsr166 |
1.82 |
} |
708 |
|
|
return n; |
709 |
|
|
} finally { |
710 |
|
|
// Restore invariants even if c.add() threw |
711 |
jsr166 |
1.89 |
if (i > 0) { |
712 |
|
|
count -= i; |
713 |
|
|
takeIndex = take; |
714 |
|
|
if (itrs != null) { |
715 |
|
|
if (count == 0) |
716 |
|
|
itrs.queueIsEmpty(); |
717 |
|
|
else if (i > take) |
718 |
|
|
itrs.takeIndexWrapped(); |
719 |
|
|
} |
720 |
|
|
for (; i > 0 && lock.hasWaiters(notFull); i--) |
721 |
|
|
notFull.signal(); |
722 |
|
|
} |
723 |
dl |
1.30 |
} |
724 |
|
|
} finally { |
725 |
jsr166 |
1.134 |
// checkInvariants(); |
726 |
dl |
1.30 |
lock.unlock(); |
727 |
|
|
} |
728 |
|
|
} |
729 |
|
|
|
730 |
brian |
1.7 |
/** |
731 |
dl |
1.75 |
* Returns an iterator over the elements in this queue in proper sequence. |
732 |
jsr166 |
1.77 |
* The elements will be returned in order from first (head) to last (tail). |
733 |
|
|
* |
734 |
jsr166 |
1.106 |
* <p>The returned iterator is |
735 |
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
736 |
brian |
1.7 |
* |
737 |
jsr166 |
1.50 |
* @return an iterator over the elements in this queue in proper sequence |
738 |
brian |
1.7 |
*/ |
739 |
dl |
1.5 |
public Iterator<E> iterator() { |
740 |
jsr166 |
1.68 |
return new Itr(); |
741 |
dl |
1.5 |
} |
742 |
dl |
1.8 |
|
743 |
|
|
/** |
744 |
jsr166 |
1.94 |
* Shared data between iterators and their queue, allowing queue |
745 |
jsr166 |
1.89 |
* modifications to update iterators when elements are removed. |
746 |
|
|
* |
747 |
jsr166 |
1.94 |
* This adds a lot of complexity for the sake of correctly |
748 |
|
|
* handling some uncommon operations, but the combination of |
749 |
|
|
* circular-arrays and supporting interior removes (i.e., those |
750 |
|
|
* not at head) would cause iterators to sometimes lose their |
751 |
|
|
* places and/or (re)report elements they shouldn't. To avoid |
752 |
|
|
* this, when a queue has one or more iterators, it keeps iterator |
753 |
|
|
* state consistent by: |
754 |
|
|
* |
755 |
|
|
* (1) keeping track of the number of "cycles", that is, the |
756 |
|
|
* number of times takeIndex has wrapped around to 0. |
757 |
|
|
* (2) notifying all iterators via the callback removedAt whenever |
758 |
|
|
* an interior element is removed (and thus other elements may |
759 |
|
|
* be shifted). |
760 |
|
|
* |
761 |
|
|
* These suffice to eliminate iterator inconsistencies, but |
762 |
|
|
* unfortunately add the secondary responsibility of maintaining |
763 |
|
|
* the list of iterators. We track all active iterators in a |
764 |
|
|
* simple linked list (accessed only when the queue's lock is |
765 |
|
|
* held) of weak references to Itr. The list is cleaned up using |
766 |
|
|
* 3 different mechanisms: |
767 |
jsr166 |
1.89 |
* |
768 |
|
|
* (1) Whenever a new iterator is created, do some O(1) checking for |
769 |
|
|
* stale list elements. |
770 |
|
|
* |
771 |
|
|
* (2) Whenever takeIndex wraps around to 0, check for iterators |
772 |
|
|
* that have been unused for more than one wrap-around cycle. |
773 |
|
|
* |
774 |
|
|
* (3) Whenever the queue becomes empty, all iterators are notified |
775 |
|
|
* and this entire data structure is discarded. |
776 |
|
|
* |
777 |
jsr166 |
1.94 |
* So in addition to the removedAt callback that is necessary for |
778 |
|
|
* correctness, iterators have the shutdown and takeIndexWrapped |
779 |
|
|
* callbacks that help remove stale iterators from the list. |
780 |
|
|
* |
781 |
|
|
* Whenever a list element is examined, it is expunged if either |
782 |
|
|
* the GC has determined that the iterator is discarded, or if the |
783 |
|
|
* iterator reports that it is "detached" (does not need any |
784 |
|
|
* further state updates). Overhead is maximal when takeIndex |
785 |
|
|
* never advances, iterators are discarded before they are |
786 |
|
|
* exhausted, and all removals are interior removes, in which case |
787 |
|
|
* all stale iterators are discovered by the GC. But even in this |
788 |
|
|
* case we don't increase the amortized complexity. |
789 |
|
|
* |
790 |
|
|
* Care must be taken to keep list sweeping methods from |
791 |
|
|
* reentrantly invoking another such method, causing subtle |
792 |
|
|
* corruption bugs. |
793 |
jsr166 |
1.89 |
*/ |
794 |
|
|
class Itrs { |
795 |
|
|
|
796 |
|
|
/** |
797 |
|
|
* Node in a linked list of weak iterator references. |
798 |
|
|
*/ |
799 |
|
|
private class Node extends WeakReference<Itr> { |
800 |
|
|
Node next; |
801 |
|
|
|
802 |
|
|
Node(Itr iterator, Node next) { |
803 |
|
|
super(iterator); |
804 |
|
|
this.next = next; |
805 |
|
|
} |
806 |
|
|
} |
807 |
|
|
|
808 |
|
|
/** Incremented whenever takeIndex wraps around to 0 */ |
809 |
jsr166 |
1.108 |
int cycles; |
810 |
jsr166 |
1.89 |
|
811 |
|
|
/** Linked list of weak iterator references */ |
812 |
jsr166 |
1.93 |
private Node head; |
813 |
jsr166 |
1.89 |
|
814 |
|
|
/** Used to expunge stale iterators */ |
815 |
jsr166 |
1.108 |
private Node sweeper; |
816 |
jsr166 |
1.89 |
|
817 |
|
|
private static final int SHORT_SWEEP_PROBES = 4; |
818 |
|
|
private static final int LONG_SWEEP_PROBES = 16; |
819 |
|
|
|
820 |
jsr166 |
1.93 |
Itrs(Itr initial) { |
821 |
|
|
register(initial); |
822 |
|
|
} |
823 |
|
|
|
824 |
jsr166 |
1.89 |
/** |
825 |
|
|
* Sweeps itrs, looking for and expunging stale iterators. |
826 |
|
|
* If at least one was found, tries harder to find more. |
827 |
jsr166 |
1.94 |
* Called only from iterating thread. |
828 |
jsr166 |
1.89 |
* |
829 |
|
|
* @param tryHarder whether to start in try-harder mode, because |
830 |
|
|
* there is known to be at least one iterator to collect |
831 |
|
|
*/ |
832 |
|
|
void doSomeSweeping(boolean tryHarder) { |
833 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
834 |
jsr166 |
1.95 |
// assert head != null; |
835 |
jsr166 |
1.89 |
int probes = tryHarder ? LONG_SWEEP_PROBES : SHORT_SWEEP_PROBES; |
836 |
|
|
Node o, p; |
837 |
|
|
final Node sweeper = this.sweeper; |
838 |
jsr166 |
1.93 |
boolean passedGo; // to limit search to one full sweep |
839 |
jsr166 |
1.89 |
|
840 |
jsr166 |
1.93 |
if (sweeper == null) { |
841 |
|
|
o = null; |
842 |
|
|
p = head; |
843 |
|
|
passedGo = true; |
844 |
|
|
} else { |
845 |
jsr166 |
1.89 |
o = sweeper; |
846 |
|
|
p = o.next; |
847 |
jsr166 |
1.93 |
passedGo = false; |
848 |
jsr166 |
1.89 |
} |
849 |
|
|
|
850 |
jsr166 |
1.93 |
for (; probes > 0; probes--) { |
851 |
|
|
if (p == null) { |
852 |
|
|
if (passedGo) |
853 |
|
|
break; |
854 |
|
|
o = null; |
855 |
|
|
p = head; |
856 |
|
|
passedGo = true; |
857 |
|
|
} |
858 |
jsr166 |
1.89 |
final Itr it = p.get(); |
859 |
|
|
final Node next = p.next; |
860 |
|
|
if (it == null || it.isDetached()) { |
861 |
|
|
// found a discarded/exhausted iterator |
862 |
|
|
probes = LONG_SWEEP_PROBES; // "try harder" |
863 |
|
|
// unlink p |
864 |
|
|
p.clear(); |
865 |
|
|
p.next = null; |
866 |
jsr166 |
1.93 |
if (o == null) { |
867 |
jsr166 |
1.89 |
head = next; |
868 |
jsr166 |
1.93 |
if (next == null) { |
869 |
|
|
// We've run out of iterators to track; retire |
870 |
|
|
itrs = null; |
871 |
|
|
return; |
872 |
|
|
} |
873 |
|
|
} |
874 |
jsr166 |
1.89 |
else |
875 |
|
|
o.next = next; |
876 |
|
|
} else { |
877 |
|
|
o = p; |
878 |
|
|
} |
879 |
|
|
p = next; |
880 |
|
|
} |
881 |
|
|
|
882 |
|
|
this.sweeper = (p == null) ? null : o; |
883 |
|
|
} |
884 |
|
|
|
885 |
|
|
/** |
886 |
|
|
* Adds a new iterator to the linked list of tracked iterators. |
887 |
|
|
*/ |
888 |
|
|
void register(Itr itr) { |
889 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
890 |
jsr166 |
1.89 |
head = new Node(itr, head); |
891 |
|
|
} |
892 |
|
|
|
893 |
|
|
/** |
894 |
|
|
* Called whenever takeIndex wraps around to 0. |
895 |
|
|
* |
896 |
|
|
* Notifies all iterators, and expunges any that are now stale. |
897 |
|
|
*/ |
898 |
|
|
void takeIndexWrapped() { |
899 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
900 |
jsr166 |
1.89 |
cycles++; |
901 |
|
|
for (Node o = null, p = head; p != null;) { |
902 |
|
|
final Itr it = p.get(); |
903 |
|
|
final Node next = p.next; |
904 |
|
|
if (it == null || it.takeIndexWrapped()) { |
905 |
|
|
// unlink p |
906 |
jsr166 |
1.95 |
// assert it == null || it.isDetached(); |
907 |
jsr166 |
1.89 |
p.clear(); |
908 |
|
|
p.next = null; |
909 |
|
|
if (o == null) |
910 |
|
|
head = next; |
911 |
|
|
else |
912 |
|
|
o.next = next; |
913 |
|
|
} else { |
914 |
|
|
o = p; |
915 |
|
|
} |
916 |
|
|
p = next; |
917 |
|
|
} |
918 |
|
|
if (head == null) // no more iterators to track |
919 |
|
|
itrs = null; |
920 |
|
|
} |
921 |
|
|
|
922 |
|
|
/** |
923 |
jsr166 |
1.107 |
* Called whenever an interior remove (not at takeIndex) occurred. |
924 |
jsr166 |
1.93 |
* |
925 |
|
|
* Notifies all iterators, and expunges any that are now stale. |
926 |
jsr166 |
1.89 |
*/ |
927 |
jsr166 |
1.90 |
void removedAt(int removedIndex) { |
928 |
jsr166 |
1.89 |
for (Node o = null, p = head; p != null;) { |
929 |
|
|
final Itr it = p.get(); |
930 |
|
|
final Node next = p.next; |
931 |
jsr166 |
1.90 |
if (it == null || it.removedAt(removedIndex)) { |
932 |
jsr166 |
1.89 |
// unlink p |
933 |
jsr166 |
1.95 |
// assert it == null || it.isDetached(); |
934 |
jsr166 |
1.89 |
p.clear(); |
935 |
|
|
p.next = null; |
936 |
|
|
if (o == null) |
937 |
|
|
head = next; |
938 |
|
|
else |
939 |
|
|
o.next = next; |
940 |
|
|
} else { |
941 |
|
|
o = p; |
942 |
|
|
} |
943 |
|
|
p = next; |
944 |
|
|
} |
945 |
|
|
if (head == null) // no more iterators to track |
946 |
|
|
itrs = null; |
947 |
|
|
} |
948 |
|
|
|
949 |
|
|
/** |
950 |
|
|
* Called whenever the queue becomes empty. |
951 |
|
|
* |
952 |
|
|
* Notifies all active iterators that the queue is empty, |
953 |
|
|
* clears all weak refs, and unlinks the itrs datastructure. |
954 |
|
|
*/ |
955 |
|
|
void queueIsEmpty() { |
956 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
957 |
jsr166 |
1.89 |
for (Node p = head; p != null; p = p.next) { |
958 |
|
|
Itr it = p.get(); |
959 |
|
|
if (it != null) { |
960 |
|
|
p.clear(); |
961 |
|
|
it.shutdown(); |
962 |
|
|
} |
963 |
|
|
} |
964 |
|
|
head = null; |
965 |
|
|
itrs = null; |
966 |
|
|
} |
967 |
|
|
|
968 |
|
|
/** |
969 |
jsr166 |
1.90 |
* Called whenever an element has been dequeued (at takeIndex). |
970 |
jsr166 |
1.89 |
*/ |
971 |
|
|
void elementDequeued() { |
972 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
973 |
jsr166 |
1.89 |
if (count == 0) |
974 |
|
|
queueIsEmpty(); |
975 |
|
|
else if (takeIndex == 0) |
976 |
|
|
takeIndexWrapped(); |
977 |
|
|
} |
978 |
|
|
} |
979 |
|
|
|
980 |
|
|
/** |
981 |
|
|
* Iterator for ArrayBlockingQueue. |
982 |
|
|
* |
983 |
|
|
* To maintain weak consistency with respect to puts and takes, we |
984 |
|
|
* read ahead one slot, so as to not report hasNext true but then |
985 |
|
|
* not have an element to return. |
986 |
|
|
* |
987 |
|
|
* We switch into "detached" mode (allowing prompt unlinking from |
988 |
|
|
* itrs without help from the GC) when all indices are negative, or |
989 |
|
|
* when hasNext returns false for the first time. This allows the |
990 |
|
|
* iterator to track concurrent updates completely accurately, |
991 |
|
|
* except for the corner case of the user calling Iterator.remove() |
992 |
|
|
* after hasNext() returned false. Even in this case, we ensure |
993 |
|
|
* that we don't remove the wrong element by keeping track of the |
994 |
|
|
* expected element to remove, in lastItem. Yes, we may fail to |
995 |
|
|
* remove lastItem from the queue if it moved due to an interleaved |
996 |
|
|
* interior remove while in detached mode. |
997 |
dl |
1.8 |
*/ |
998 |
dl |
1.5 |
private class Itr implements Iterator<E> { |
999 |
jsr166 |
1.91 |
/** Index to look for new nextItem; NONE at end */ |
1000 |
jsr166 |
1.89 |
private int cursor; |
1001 |
|
|
|
1002 |
|
|
/** Element to be returned by next call to next(); null if none */ |
1003 |
|
|
private E nextItem; |
1004 |
|
|
|
1005 |
jsr166 |
1.91 |
/** Index of nextItem; NONE if none, REMOVED if removed elsewhere */ |
1006 |
jsr166 |
1.89 |
private int nextIndex; |
1007 |
|
|
|
1008 |
|
|
/** Last element returned; null if none or not detached. */ |
1009 |
|
|
private E lastItem; |
1010 |
|
|
|
1011 |
jsr166 |
1.91 |
/** Index of lastItem, NONE if none, REMOVED if removed elsewhere */ |
1012 |
jsr166 |
1.89 |
private int lastRet; |
1013 |
|
|
|
1014 |
jsr166 |
1.91 |
/** Previous value of takeIndex, or DETACHED when detached */ |
1015 |
jsr166 |
1.89 |
private int prevTakeIndex; |
1016 |
|
|
|
1017 |
|
|
/** Previous value of iters.cycles */ |
1018 |
|
|
private int prevCycles; |
1019 |
tim |
1.12 |
|
1020 |
jsr166 |
1.91 |
/** Special index value indicating "not available" or "undefined" */ |
1021 |
|
|
private static final int NONE = -1; |
1022 |
|
|
|
1023 |
|
|
/** |
1024 |
|
|
* Special index value indicating "removed elsewhere", that is, |
1025 |
|
|
* removed by some operation other than a call to this.remove(). |
1026 |
|
|
*/ |
1027 |
|
|
private static final int REMOVED = -2; |
1028 |
|
|
|
1029 |
|
|
/** Special value for prevTakeIndex indicating "detached mode" */ |
1030 |
|
|
private static final int DETACHED = -3; |
1031 |
|
|
|
1032 |
dl |
1.66 |
Itr() { |
1033 |
jsr166 |
1.91 |
lastRet = NONE; |
1034 |
jsr166 |
1.68 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
1035 |
|
|
lock.lock(); |
1036 |
|
|
try { |
1037 |
jsr166 |
1.89 |
if (count == 0) { |
1038 |
jsr166 |
1.95 |
// assert itrs == null; |
1039 |
jsr166 |
1.91 |
cursor = NONE; |
1040 |
|
|
nextIndex = NONE; |
1041 |
|
|
prevTakeIndex = DETACHED; |
1042 |
jsr166 |
1.89 |
} else { |
1043 |
|
|
final int takeIndex = ArrayBlockingQueue.this.takeIndex; |
1044 |
|
|
prevTakeIndex = takeIndex; |
1045 |
jsr166 |
1.68 |
nextItem = itemAt(nextIndex = takeIndex); |
1046 |
jsr166 |
1.89 |
cursor = incCursor(takeIndex); |
1047 |
|
|
if (itrs == null) { |
1048 |
jsr166 |
1.93 |
itrs = new Itrs(this); |
1049 |
jsr166 |
1.89 |
} else { |
1050 |
|
|
itrs.register(this); // in this order |
1051 |
|
|
itrs.doSomeSweeping(false); |
1052 |
|
|
} |
1053 |
|
|
prevCycles = itrs.cycles; |
1054 |
jsr166 |
1.95 |
// assert takeIndex >= 0; |
1055 |
|
|
// assert prevTakeIndex == takeIndex; |
1056 |
|
|
// assert nextIndex >= 0; |
1057 |
|
|
// assert nextItem != null; |
1058 |
jsr166 |
1.89 |
} |
1059 |
jsr166 |
1.68 |
} finally { |
1060 |
|
|
lock.unlock(); |
1061 |
|
|
} |
1062 |
dl |
1.5 |
} |
1063 |
tim |
1.12 |
|
1064 |
jsr166 |
1.89 |
boolean isDetached() { |
1065 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1066 |
jsr166 |
1.89 |
return prevTakeIndex < 0; |
1067 |
|
|
} |
1068 |
|
|
|
1069 |
|
|
private int incCursor(int index) { |
1070 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1071 |
jsr166 |
1.116 |
if (++index == items.length) index = 0; |
1072 |
|
|
if (index == putIndex) index = NONE; |
1073 |
jsr166 |
1.89 |
return index; |
1074 |
|
|
} |
1075 |
|
|
|
1076 |
|
|
/** |
1077 |
|
|
* Returns true if index is invalidated by the given number of |
1078 |
|
|
* dequeues, starting from prevTakeIndex. |
1079 |
|
|
*/ |
1080 |
|
|
private boolean invalidated(int index, int prevTakeIndex, |
1081 |
|
|
long dequeues, int length) { |
1082 |
|
|
if (index < 0) |
1083 |
|
|
return false; |
1084 |
|
|
int distance = index - prevTakeIndex; |
1085 |
|
|
if (distance < 0) |
1086 |
|
|
distance += length; |
1087 |
|
|
return dequeues > distance; |
1088 |
|
|
} |
1089 |
|
|
|
1090 |
|
|
/** |
1091 |
|
|
* Adjusts indices to incorporate all dequeues since the last |
1092 |
|
|
* operation on this iterator. Call only from iterating thread. |
1093 |
|
|
*/ |
1094 |
|
|
private void incorporateDequeues() { |
1095 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1096 |
jsr166 |
1.95 |
// assert itrs != null; |
1097 |
|
|
// assert !isDetached(); |
1098 |
|
|
// assert count > 0; |
1099 |
jsr166 |
1.89 |
|
1100 |
|
|
final int cycles = itrs.cycles; |
1101 |
|
|
final int takeIndex = ArrayBlockingQueue.this.takeIndex; |
1102 |
|
|
final int prevCycles = this.prevCycles; |
1103 |
|
|
final int prevTakeIndex = this.prevTakeIndex; |
1104 |
|
|
|
1105 |
|
|
if (cycles != prevCycles || takeIndex != prevTakeIndex) { |
1106 |
|
|
final int len = items.length; |
1107 |
|
|
// how far takeIndex has advanced since the previous |
1108 |
|
|
// operation of this iterator |
1109 |
|
|
long dequeues = (cycles - prevCycles) * len |
1110 |
|
|
+ (takeIndex - prevTakeIndex); |
1111 |
|
|
|
1112 |
|
|
// Check indices for invalidation |
1113 |
|
|
if (invalidated(lastRet, prevTakeIndex, dequeues, len)) |
1114 |
jsr166 |
1.91 |
lastRet = REMOVED; |
1115 |
jsr166 |
1.89 |
if (invalidated(nextIndex, prevTakeIndex, dequeues, len)) |
1116 |
jsr166 |
1.91 |
nextIndex = REMOVED; |
1117 |
jsr166 |
1.89 |
if (invalidated(cursor, prevTakeIndex, dequeues, len)) |
1118 |
|
|
cursor = takeIndex; |
1119 |
|
|
|
1120 |
|
|
if (cursor < 0 && nextIndex < 0 && lastRet < 0) |
1121 |
|
|
detach(); |
1122 |
|
|
else { |
1123 |
|
|
this.prevCycles = cycles; |
1124 |
|
|
this.prevTakeIndex = takeIndex; |
1125 |
|
|
} |
1126 |
|
|
} |
1127 |
|
|
} |
1128 |
|
|
|
1129 |
|
|
/** |
1130 |
|
|
* Called when itrs should stop tracking this iterator, either |
1131 |
|
|
* because there are no more indices to update (cursor < 0 && |
1132 |
|
|
* nextIndex < 0 && lastRet < 0) or as a special exception, when |
1133 |
|
|
* lastRet >= 0, because hasNext() is about to return false for the |
1134 |
|
|
* first time. Call only from iterating thread. |
1135 |
|
|
*/ |
1136 |
|
|
private void detach() { |
1137 |
|
|
// Switch to detached mode |
1138 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1139 |
jsr166 |
1.95 |
// assert cursor == NONE; |
1140 |
|
|
// assert nextIndex < 0; |
1141 |
|
|
// assert lastRet < 0 || nextItem == null; |
1142 |
|
|
// assert lastRet < 0 ^ lastItem != null; |
1143 |
jsr166 |
1.89 |
if (prevTakeIndex >= 0) { |
1144 |
jsr166 |
1.95 |
// assert itrs != null; |
1145 |
jsr166 |
1.91 |
prevTakeIndex = DETACHED; |
1146 |
jsr166 |
1.89 |
// try to unlink from itrs (but not too hard) |
1147 |
|
|
itrs.doSomeSweeping(true); |
1148 |
|
|
} |
1149 |
|
|
} |
1150 |
|
|
|
1151 |
|
|
/** |
1152 |
|
|
* For performance reasons, we would like not to acquire a lock in |
1153 |
|
|
* hasNext in the common case. To allow for this, we only access |
1154 |
|
|
* fields (i.e. nextItem) that are not modified by update operations |
1155 |
|
|
* triggered by queue modifications. |
1156 |
|
|
*/ |
1157 |
dl |
1.5 |
public boolean hasNext() { |
1158 |
jsr166 |
1.89 |
if (nextItem != null) |
1159 |
|
|
return true; |
1160 |
|
|
noNext(); |
1161 |
|
|
return false; |
1162 |
|
|
} |
1163 |
|
|
|
1164 |
|
|
private void noNext() { |
1165 |
|
|
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
1166 |
|
|
lock.lock(); |
1167 |
|
|
try { |
1168 |
jsr166 |
1.95 |
// assert cursor == NONE; |
1169 |
|
|
// assert nextIndex == NONE; |
1170 |
jsr166 |
1.89 |
if (!isDetached()) { |
1171 |
jsr166 |
1.95 |
// assert lastRet >= 0; |
1172 |
jsr166 |
1.89 |
incorporateDequeues(); // might update lastRet |
1173 |
|
|
if (lastRet >= 0) { |
1174 |
|
|
lastItem = itemAt(lastRet); |
1175 |
jsr166 |
1.95 |
// assert lastItem != null; |
1176 |
jsr166 |
1.89 |
detach(); |
1177 |
|
|
} |
1178 |
|
|
} |
1179 |
jsr166 |
1.95 |
// assert isDetached(); |
1180 |
|
|
// assert lastRet < 0 ^ lastItem != null; |
1181 |
jsr166 |
1.89 |
} finally { |
1182 |
|
|
lock.unlock(); |
1183 |
|
|
} |
1184 |
dl |
1.5 |
} |
1185 |
tim |
1.12 |
|
1186 |
dl |
1.5 |
public E next() { |
1187 |
jsr166 |
1.141 |
final E e = nextItem; |
1188 |
|
|
if (e == null) |
1189 |
jsr166 |
1.89 |
throw new NoSuchElementException(); |
1190 |
dl |
1.66 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
1191 |
|
|
lock.lock(); |
1192 |
|
|
try { |
1193 |
jsr166 |
1.92 |
if (!isDetached()) |
1194 |
jsr166 |
1.89 |
incorporateDequeues(); |
1195 |
jsr166 |
1.95 |
// assert nextIndex != NONE; |
1196 |
|
|
// assert lastItem == null; |
1197 |
dl |
1.66 |
lastRet = nextIndex; |
1198 |
jsr166 |
1.89 |
final int cursor = this.cursor; |
1199 |
|
|
if (cursor >= 0) { |
1200 |
|
|
nextItem = itemAt(nextIndex = cursor); |
1201 |
jsr166 |
1.95 |
// assert nextItem != null; |
1202 |
jsr166 |
1.89 |
this.cursor = incCursor(cursor); |
1203 |
|
|
} else { |
1204 |
jsr166 |
1.91 |
nextIndex = NONE; |
1205 |
jsr166 |
1.89 |
nextItem = null; |
1206 |
|
|
} |
1207 |
dl |
1.66 |
} finally { |
1208 |
|
|
lock.unlock(); |
1209 |
dl |
1.2 |
} |
1210 |
jsr166 |
1.141 |
return e; |
1211 |
dl |
1.5 |
} |
1212 |
tim |
1.12 |
|
1213 |
jsr166 |
1.136 |
public void forEachRemaining(Consumer<? super E> action) { |
1214 |
|
|
Objects.requireNonNull(action); |
1215 |
|
|
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
1216 |
|
|
lock.lock(); |
1217 |
|
|
try { |
1218 |
jsr166 |
1.141 |
final E e = nextItem; |
1219 |
|
|
if (e == null) return; |
1220 |
jsr166 |
1.136 |
if (!isDetached()) |
1221 |
|
|
incorporateDequeues(); |
1222 |
jsr166 |
1.141 |
action.accept(e); |
1223 |
jsr166 |
1.136 |
if (isDetached() || cursor < 0) return; |
1224 |
|
|
final Object[] items = ArrayBlockingQueue.this.items; |
1225 |
|
|
for (int i = cursor, end = putIndex, |
1226 |
|
|
to = (i < end) ? end : items.length; |
1227 |
|
|
; i = 0, to = end) { |
1228 |
|
|
for (; i < to; i++) |
1229 |
|
|
action.accept(itemAt(items, i)); |
1230 |
|
|
if (to == end) break; |
1231 |
|
|
} |
1232 |
|
|
} finally { |
1233 |
|
|
// Calling forEachRemaining is a strong hint that this |
1234 |
|
|
// iteration is surely over; supporting remove() after |
1235 |
|
|
// forEachRemaining() is more trouble than it's worth |
1236 |
jsr166 |
1.140 |
cursor = nextIndex = lastRet = NONE; |
1237 |
jsr166 |
1.136 |
nextItem = lastItem = null; |
1238 |
|
|
detach(); |
1239 |
|
|
lock.unlock(); |
1240 |
|
|
} |
1241 |
|
|
} |
1242 |
|
|
|
1243 |
dl |
1.5 |
public void remove() { |
1244 |
dl |
1.36 |
final ReentrantLock lock = ArrayBlockingQueue.this.lock; |
1245 |
dl |
1.5 |
lock.lock(); |
1246 |
jsr166 |
1.137 |
// assert lock.getHoldCount() == 1; |
1247 |
dl |
1.5 |
try { |
1248 |
jsr166 |
1.92 |
if (!isDetached()) |
1249 |
|
|
incorporateDequeues(); // might update lastRet or detach |
1250 |
|
|
final int lastRet = this.lastRet; |
1251 |
|
|
this.lastRet = NONE; |
1252 |
jsr166 |
1.89 |
if (lastRet >= 0) { |
1253 |
jsr166 |
1.92 |
if (!isDetached()) |
1254 |
|
|
removeAt(lastRet); |
1255 |
|
|
else { |
1256 |
|
|
final E lastItem = this.lastItem; |
1257 |
jsr166 |
1.95 |
// assert lastItem != null; |
1258 |
jsr166 |
1.92 |
this.lastItem = null; |
1259 |
jsr166 |
1.89 |
if (itemAt(lastRet) == lastItem) |
1260 |
|
|
removeAt(lastRet); |
1261 |
|
|
} |
1262 |
jsr166 |
1.91 |
} else if (lastRet == NONE) |
1263 |
dl |
1.66 |
throw new IllegalStateException(); |
1264 |
jsr166 |
1.91 |
// else lastRet == REMOVED and the last returned element was |
1265 |
jsr166 |
1.89 |
// previously asynchronously removed via an operation other |
1266 |
|
|
// than this.remove(), so nothing to do. |
1267 |
|
|
|
1268 |
|
|
if (cursor < 0 && nextIndex < 0) |
1269 |
|
|
detach(); |
1270 |
|
|
} finally { |
1271 |
|
|
lock.unlock(); |
1272 |
jsr166 |
1.95 |
// assert lastRet == NONE; |
1273 |
|
|
// assert lastItem == null; |
1274 |
jsr166 |
1.89 |
} |
1275 |
|
|
} |
1276 |
|
|
|
1277 |
|
|
/** |
1278 |
|
|
* Called to notify the iterator that the queue is empty, or that it |
1279 |
|
|
* has fallen hopelessly behind, so that it should abandon any |
1280 |
|
|
* further iteration, except possibly to return one more element |
1281 |
|
|
* from next(), as promised by returning true from hasNext(). |
1282 |
|
|
*/ |
1283 |
|
|
void shutdown() { |
1284 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1285 |
jsr166 |
1.91 |
cursor = NONE; |
1286 |
jsr166 |
1.89 |
if (nextIndex >= 0) |
1287 |
jsr166 |
1.91 |
nextIndex = REMOVED; |
1288 |
jsr166 |
1.89 |
if (lastRet >= 0) { |
1289 |
jsr166 |
1.91 |
lastRet = REMOVED; |
1290 |
jsr166 |
1.61 |
lastItem = null; |
1291 |
jsr166 |
1.89 |
} |
1292 |
jsr166 |
1.91 |
prevTakeIndex = DETACHED; |
1293 |
jsr166 |
1.89 |
// Don't set nextItem to null because we must continue to be |
1294 |
|
|
// able to return it on next(). |
1295 |
|
|
// |
1296 |
|
|
// Caller will unlink from itrs when convenient. |
1297 |
|
|
} |
1298 |
|
|
|
1299 |
|
|
private int distance(int index, int prevTakeIndex, int length) { |
1300 |
|
|
int distance = index - prevTakeIndex; |
1301 |
|
|
if (distance < 0) |
1302 |
|
|
distance += length; |
1303 |
|
|
return distance; |
1304 |
|
|
} |
1305 |
|
|
|
1306 |
|
|
/** |
1307 |
jsr166 |
1.107 |
* Called whenever an interior remove (not at takeIndex) occurred. |
1308 |
jsr166 |
1.89 |
* |
1309 |
jsr166 |
1.90 |
* @return true if this iterator should be unlinked from itrs |
1310 |
jsr166 |
1.89 |
*/ |
1311 |
jsr166 |
1.90 |
boolean removedAt(int removedIndex) { |
1312 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1313 |
jsr166 |
1.89 |
if (isDetached()) |
1314 |
|
|
return true; |
1315 |
|
|
|
1316 |
|
|
final int takeIndex = ArrayBlockingQueue.this.takeIndex; |
1317 |
|
|
final int prevTakeIndex = this.prevTakeIndex; |
1318 |
|
|
final int len = items.length; |
1319 |
jsr166 |
1.112 |
// distance from prevTakeIndex to removedIndex |
1320 |
jsr166 |
1.89 |
final int removedDistance = |
1321 |
jsr166 |
1.112 |
len * (itrs.cycles - this.prevCycles |
1322 |
|
|
+ ((removedIndex < takeIndex) ? 1 : 0)) |
1323 |
|
|
+ (removedIndex - prevTakeIndex); |
1324 |
|
|
// assert itrs.cycles - this.prevCycles >= 0; |
1325 |
|
|
// assert itrs.cycles - this.prevCycles <= 1; |
1326 |
|
|
// assert removedDistance > 0; |
1327 |
|
|
// assert removedIndex != takeIndex; |
1328 |
jsr166 |
1.89 |
int cursor = this.cursor; |
1329 |
|
|
if (cursor >= 0) { |
1330 |
|
|
int x = distance(cursor, prevTakeIndex, len); |
1331 |
|
|
if (x == removedDistance) { |
1332 |
jsr166 |
1.90 |
if (cursor == putIndex) |
1333 |
jsr166 |
1.91 |
this.cursor = cursor = NONE; |
1334 |
jsr166 |
1.89 |
} |
1335 |
|
|
else if (x > removedDistance) { |
1336 |
jsr166 |
1.95 |
// assert cursor != prevTakeIndex; |
1337 |
jsr166 |
1.135 |
this.cursor = cursor = dec(cursor, len); |
1338 |
jsr166 |
1.71 |
} |
1339 |
dl |
1.5 |
} |
1340 |
jsr166 |
1.89 |
int lastRet = this.lastRet; |
1341 |
|
|
if (lastRet >= 0) { |
1342 |
|
|
int x = distance(lastRet, prevTakeIndex, len); |
1343 |
|
|
if (x == removedDistance) |
1344 |
jsr166 |
1.91 |
this.lastRet = lastRet = REMOVED; |
1345 |
jsr166 |
1.89 |
else if (x > removedDistance) |
1346 |
jsr166 |
1.135 |
this.lastRet = lastRet = dec(lastRet, len); |
1347 |
jsr166 |
1.89 |
} |
1348 |
|
|
int nextIndex = this.nextIndex; |
1349 |
|
|
if (nextIndex >= 0) { |
1350 |
|
|
int x = distance(nextIndex, prevTakeIndex, len); |
1351 |
|
|
if (x == removedDistance) |
1352 |
jsr166 |
1.91 |
this.nextIndex = nextIndex = REMOVED; |
1353 |
jsr166 |
1.89 |
else if (x > removedDistance) |
1354 |
jsr166 |
1.135 |
this.nextIndex = nextIndex = dec(nextIndex, len); |
1355 |
jsr166 |
1.89 |
} |
1356 |
jsr166 |
1.112 |
if (cursor < 0 && nextIndex < 0 && lastRet < 0) { |
1357 |
jsr166 |
1.91 |
this.prevTakeIndex = DETACHED; |
1358 |
jsr166 |
1.89 |
return true; |
1359 |
|
|
} |
1360 |
|
|
return false; |
1361 |
|
|
} |
1362 |
|
|
|
1363 |
|
|
/** |
1364 |
|
|
* Called whenever takeIndex wraps around to zero. |
1365 |
|
|
* |
1366 |
jsr166 |
1.90 |
* @return true if this iterator should be unlinked from itrs |
1367 |
jsr166 |
1.89 |
*/ |
1368 |
|
|
boolean takeIndexWrapped() { |
1369 |
jsr166 |
1.137 |
// assert lock.isHeldByCurrentThread(); |
1370 |
jsr166 |
1.89 |
if (isDetached()) |
1371 |
|
|
return true; |
1372 |
|
|
if (itrs.cycles - prevCycles > 1) { |
1373 |
|
|
// All the elements that existed at the time of the last |
1374 |
|
|
// operation are gone, so abandon further iteration. |
1375 |
|
|
shutdown(); |
1376 |
|
|
return true; |
1377 |
|
|
} |
1378 |
|
|
return false; |
1379 |
dl |
1.5 |
} |
1380 |
jsr166 |
1.89 |
|
1381 |
|
|
// /** Uncomment for debugging. */ |
1382 |
|
|
// public String toString() { |
1383 |
|
|
// return ("cursor=" + cursor + " " + |
1384 |
|
|
// "nextIndex=" + nextIndex + " " + |
1385 |
|
|
// "lastRet=" + lastRet + " " + |
1386 |
|
|
// "nextItem=" + nextItem + " " + |
1387 |
|
|
// "lastItem=" + lastItem + " " + |
1388 |
|
|
// "prevCycles=" + prevCycles + " " + |
1389 |
|
|
// "prevTakeIndex=" + prevTakeIndex + " " + |
1390 |
|
|
// "size()=" + size() + " " + |
1391 |
|
|
// "remainingCapacity()=" + remainingCapacity()); |
1392 |
|
|
// } |
1393 |
tim |
1.1 |
} |
1394 |
dl |
1.100 |
|
1395 |
jsr166 |
1.105 |
/** |
1396 |
|
|
* Returns a {@link Spliterator} over the elements in this queue. |
1397 |
|
|
* |
1398 |
jsr166 |
1.106 |
* <p>The returned spliterator is |
1399 |
|
|
* <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>. |
1400 |
|
|
* |
1401 |
jsr166 |
1.105 |
* <p>The {@code Spliterator} reports {@link Spliterator#CONCURRENT}, |
1402 |
|
|
* {@link Spliterator#ORDERED}, and {@link Spliterator#NONNULL}. |
1403 |
|
|
* |
1404 |
|
|
* @implNote |
1405 |
|
|
* The {@code Spliterator} implements {@code trySplit} to permit limited |
1406 |
|
|
* parallelism. |
1407 |
|
|
* |
1408 |
|
|
* @return a {@code Spliterator} over the elements in this queue |
1409 |
|
|
* @since 1.8 |
1410 |
|
|
*/ |
1411 |
dl |
1.103 |
public Spliterator<E> spliterator() { |
1412 |
dl |
1.102 |
return Spliterators.spliterator |
1413 |
jsr166 |
1.124 |
(this, (Spliterator.ORDERED | |
1414 |
|
|
Spliterator.NONNULL | |
1415 |
|
|
Spliterator.CONCURRENT)); |
1416 |
dl |
1.100 |
} |
1417 |
|
|
|
1418 |
jsr166 |
1.143 |
/** |
1419 |
|
|
* @throws NullPointerException {@inheritDoc} |
1420 |
|
|
*/ |
1421 |
jsr166 |
1.127 |
public void forEach(Consumer<? super E> action) { |
1422 |
|
|
Objects.requireNonNull(action); |
1423 |
|
|
final ReentrantLock lock = this.lock; |
1424 |
|
|
lock.lock(); |
1425 |
|
|
try { |
1426 |
|
|
if (count > 0) { |
1427 |
|
|
final Object[] items = this.items; |
1428 |
jsr166 |
1.128 |
for (int i = takeIndex, end = putIndex, |
1429 |
|
|
to = (i < end) ? end : items.length; |
1430 |
|
|
; i = 0, to = end) { |
1431 |
|
|
for (; i < to; i++) |
1432 |
|
|
action.accept(itemAt(items, i)); |
1433 |
|
|
if (to == end) break; |
1434 |
|
|
} |
1435 |
jsr166 |
1.127 |
} |
1436 |
|
|
} finally { |
1437 |
jsr166 |
1.131 |
// checkInvariants(); |
1438 |
jsr166 |
1.127 |
lock.unlock(); |
1439 |
|
|
} |
1440 |
|
|
} |
1441 |
|
|
|
1442 |
jsr166 |
1.135 |
/** |
1443 |
|
|
* @throws NullPointerException {@inheritDoc} |
1444 |
|
|
*/ |
1445 |
|
|
public boolean removeIf(Predicate<? super E> filter) { |
1446 |
|
|
Objects.requireNonNull(filter); |
1447 |
|
|
return bulkRemove(filter); |
1448 |
|
|
} |
1449 |
|
|
|
1450 |
|
|
/** |
1451 |
|
|
* @throws NullPointerException {@inheritDoc} |
1452 |
|
|
*/ |
1453 |
|
|
public boolean removeAll(Collection<?> c) { |
1454 |
|
|
Objects.requireNonNull(c); |
1455 |
|
|
return bulkRemove(e -> c.contains(e)); |
1456 |
|
|
} |
1457 |
|
|
|
1458 |
|
|
/** |
1459 |
|
|
* @throws NullPointerException {@inheritDoc} |
1460 |
|
|
*/ |
1461 |
|
|
public boolean retainAll(Collection<?> c) { |
1462 |
|
|
Objects.requireNonNull(c); |
1463 |
|
|
return bulkRemove(e -> !c.contains(e)); |
1464 |
|
|
} |
1465 |
|
|
|
1466 |
|
|
/** Implementation of bulk remove methods. */ |
1467 |
|
|
private boolean bulkRemove(Predicate<? super E> filter) { |
1468 |
|
|
final ReentrantLock lock = this.lock; |
1469 |
|
|
lock.lock(); |
1470 |
|
|
try { |
1471 |
|
|
if (itrs == null) { // check for active iterators |
1472 |
|
|
if (count > 0) { |
1473 |
|
|
final Object[] items = this.items; |
1474 |
|
|
// Optimize for initial run of survivors |
1475 |
|
|
for (int i = takeIndex, end = putIndex, |
1476 |
|
|
to = (i < end) ? end : items.length; |
1477 |
|
|
; i = 0, to = end) { |
1478 |
|
|
for (; i < to; i++) |
1479 |
|
|
if (filter.test(itemAt(items, i))) |
1480 |
jsr166 |
1.137 |
return bulkRemoveModified(filter, i); |
1481 |
jsr166 |
1.135 |
if (to == end) break; |
1482 |
|
|
} |
1483 |
|
|
} |
1484 |
|
|
return false; |
1485 |
|
|
} |
1486 |
|
|
} finally { |
1487 |
|
|
// checkInvariants(); |
1488 |
|
|
lock.unlock(); |
1489 |
|
|
} |
1490 |
|
|
// Active iterators are too hairy! |
1491 |
|
|
// Punting (for now) to the slow n^2 algorithm ... |
1492 |
|
|
return super.removeIf(filter); |
1493 |
|
|
} |
1494 |
|
|
|
1495 |
jsr166 |
1.137 |
// A tiny bit set implementation |
1496 |
|
|
|
1497 |
|
|
private static long[] nBits(int n) { |
1498 |
|
|
return new long[((n - 1) >> 6) + 1]; |
1499 |
|
|
} |
1500 |
|
|
private static void setBit(long[] bits, int i) { |
1501 |
|
|
bits[i >> 6] |= 1L << i; |
1502 |
|
|
} |
1503 |
|
|
private static boolean isClear(long[] bits, int i) { |
1504 |
|
|
return (bits[i >> 6] & (1L << i)) == 0; |
1505 |
|
|
} |
1506 |
|
|
|
1507 |
|
|
/** |
1508 |
|
|
* Returns circular distance from i to j, disambiguating i == j to |
1509 |
|
|
* items.length; never returns 0. |
1510 |
|
|
*/ |
1511 |
|
|
private int distanceNonEmpty(int i, int j) { |
1512 |
|
|
if ((j -= i) <= 0) j += items.length; |
1513 |
|
|
return j; |
1514 |
|
|
} |
1515 |
|
|
|
1516 |
jsr166 |
1.135 |
/** |
1517 |
|
|
* Helper for bulkRemove, in case of at least one deletion. |
1518 |
jsr166 |
1.137 |
* Tolerate predicates that reentrantly access the collection for |
1519 |
|
|
* read (but not write), so traverse once to find elements to |
1520 |
|
|
* delete, a second pass to physically expunge. |
1521 |
|
|
* |
1522 |
|
|
* @param beg valid index of first element to be deleted |
1523 |
jsr166 |
1.135 |
*/ |
1524 |
|
|
private boolean bulkRemoveModified( |
1525 |
jsr166 |
1.137 |
Predicate<? super E> filter, final int beg) { |
1526 |
|
|
final Object[] es = items; |
1527 |
jsr166 |
1.135 |
final int capacity = items.length; |
1528 |
|
|
final int end = putIndex; |
1529 |
jsr166 |
1.137 |
final long[] deathRow = nBits(distanceNonEmpty(beg, putIndex)); |
1530 |
|
|
deathRow[0] = 1L; // set bit 0 |
1531 |
|
|
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1532 |
|
|
; i = 0, to = end, k -= capacity) { |
1533 |
|
|
for (; i < to; i++) |
1534 |
|
|
if (filter.test(itemAt(es, i))) |
1535 |
|
|
setBit(deathRow, i - k); |
1536 |
|
|
if (to == end) break; |
1537 |
|
|
} |
1538 |
|
|
// a two-finger traversal, with hare i reading, tortoise w writing |
1539 |
|
|
int w = beg; |
1540 |
|
|
for (int i = beg + 1, to = (i <= end) ? end : es.length, k = beg; |
1541 |
|
|
; w = 0) { // w rejoins i on second leg |
1542 |
|
|
// In this loop, i and w are on the same leg, with i > w |
1543 |
|
|
for (; i < to; i++) |
1544 |
|
|
if (isClear(deathRow, i - k)) |
1545 |
|
|
es[w++] = es[i]; |
1546 |
|
|
if (to == end) break; |
1547 |
|
|
// In this loop, w is on the first leg, i on the second |
1548 |
|
|
for (i = 0, to = end, k -= capacity; i < to && w < capacity; i++) |
1549 |
|
|
if (isClear(deathRow, i - k)) |
1550 |
|
|
es[w++] = es[i]; |
1551 |
|
|
if (i >= to) { |
1552 |
|
|
if (w == capacity) w = 0; // "corner" case |
1553 |
|
|
break; |
1554 |
jsr166 |
1.135 |
} |
1555 |
|
|
} |
1556 |
jsr166 |
1.137 |
count -= distanceNonEmpty(w, end); |
1557 |
|
|
circularClear(es, putIndex = w, end); |
1558 |
|
|
// checkInvariants(); |
1559 |
|
|
return true; |
1560 |
jsr166 |
1.135 |
} |
1561 |
|
|
|
1562 |
jsr166 |
1.128 |
/** debugging */ |
1563 |
|
|
void checkInvariants() { |
1564 |
jsr166 |
1.134 |
// meta-assertions |
1565 |
jsr166 |
1.128 |
// assert lock.isHeldByCurrentThread(); |
1566 |
|
|
try { |
1567 |
jsr166 |
1.138 |
// Unlike ArrayDeque, we have a count field but no spare slot. |
1568 |
jsr166 |
1.139 |
// We prefer ArrayDeque's strategy (and the names of its fields!), |
1569 |
|
|
// but our field layout is baked into the serial form, and so is |
1570 |
|
|
// too annoying to change. |
1571 |
|
|
// |
1572 |
jsr166 |
1.138 |
// putIndex == takeIndex must be disambiguated by checking count. |
1573 |
jsr166 |
1.128 |
int capacity = items.length; |
1574 |
|
|
// assert capacity > 0; |
1575 |
|
|
// assert takeIndex >= 0 && takeIndex < capacity; |
1576 |
|
|
// assert putIndex >= 0 && putIndex < capacity; |
1577 |
|
|
// assert count <= capacity; |
1578 |
|
|
// assert takeIndex == putIndex || items[takeIndex] != null; |
1579 |
|
|
// assert count == capacity || items[putIndex] == null; |
1580 |
|
|
// assert takeIndex == putIndex || items[dec(putIndex, capacity)] != null; |
1581 |
|
|
} catch (Throwable t) { |
1582 |
jsr166 |
1.134 |
System.err.printf("takeIndex=%d putIndex=%d count=%d capacity=%d%n", |
1583 |
|
|
takeIndex, putIndex, count, items.length); |
1584 |
jsr166 |
1.128 |
System.err.printf("items=%s%n", |
1585 |
|
|
Arrays.toString(items)); |
1586 |
|
|
throw t; |
1587 |
|
|
} |
1588 |
|
|
} |
1589 |
|
|
|
1590 |
tim |
1.1 |
} |