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--- old/src/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java
+++ new/src/share/classes/java/util/concurrent/atomic/AtomicIntegerArray.java
1 1 /*
2 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 3 *
4 4 * This code is free software; you can redistribute it and/or modify it
5 5 * under the terms of the GNU General Public License version 2 only, as
6 6 * published by the Free Software Foundation. Oracle designates this
7 7 * particular file as subject to the "Classpath" exception as provided
8 8 * by Oracle in the LICENSE file that accompanied this code.
9 9 *
10 10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 13 * version 2 for more details (a copy is included in the LICENSE file that
14 14 * accompanied this code).
15 15 *
16 16 * You should have received a copy of the GNU General Public License version
17 17 * 2 along with this work; if not, write to the Free Software Foundation,
18 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 19 *
20 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 21 * or visit www.oracle.com if you need additional information or have any
22 22 * questions.
23 23 */
24 24
25 25 /*
26 26 * This file is available under and governed by the GNU General Public
27 27 * License version 2 only, as published by the Free Software Foundation.
28 28 * However, the following notice accompanied the original version of this
29 29 * file:
30 30 *
31 31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 32 * Expert Group and released to the public domain, as explained at
33 33 * http://creativecommons.org/licenses/publicdomain
34 34 */
35 35
36 36 package java.util.concurrent.atomic;
37 37 import sun.misc.Unsafe;
38 38 import java.util.*;
39 39
40 40 /**
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40 lines elided |
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41 41 * An {@code int} array in which elements may be updated atomically.
42 42 * See the {@link java.util.concurrent.atomic} package
43 43 * specification for description of the properties of atomic
44 44 * variables.
45 45 * @since 1.5
46 46 * @author Doug Lea
47 47 */
48 48 public class AtomicIntegerArray implements java.io.Serializable {
49 49 private static final long serialVersionUID = 2862133569453604235L;
50 50
51 - // setup to use Unsafe.compareAndSwapInt for updates
52 51 private static final Unsafe unsafe = Unsafe.getUnsafe();
53 52 private static final int base = unsafe.arrayBaseOffset(int[].class);
54 - private static final int scale = unsafe.arrayIndexScale(int[].class);
53 + private static final int shift;
55 54 private final int[] array;
56 55
57 - private long rawIndex(int i) {
56 + static {
57 + int scale = unsafe.arrayIndexScale(int[].class);
58 + if ((scale & (scale - 1)) != 0)
59 + throw new Error("data type scale not a power of two");
60 + shift = 31 - Integer.numberOfLeadingZeros(scale);
61 + }
62 +
63 + private long checkedByteOffset(int i) {
58 64 if (i < 0 || i >= array.length)
59 65 throw new IndexOutOfBoundsException("index " + i);
60 - return base + (long) i * scale;
66 +
67 + return byteOffset(i);
61 68 }
62 69
70 + private static long byteOffset(int i) {
71 + return ((long) i << shift) + base;
72 + }
73 +
63 74 /**
64 - * Creates a new AtomicIntegerArray of given length.
75 + * Creates a new AtomicIntegerArray of the given length, with all
76 + * elements initially zero.
65 77 *
66 78 * @param length the length of the array
67 79 */
68 80 public AtomicIntegerArray(int length) {
69 81 array = new int[length];
70 - // must perform at least one volatile write to conform to JMM
71 - if (length > 0)
72 - unsafe.putIntVolatile(array, rawIndex(0), 0);
73 82 }
74 83
75 84 /**
76 85 * Creates a new AtomicIntegerArray with the same length as, and
77 86 * all elements copied from, the given array.
78 87 *
79 88 * @param array the array to copy elements from
80 89 * @throws NullPointerException if array is null
81 90 */
82 91 public AtomicIntegerArray(int[] array) {
83 - if (array == null)
84 - throw new NullPointerException();
85 - int length = array.length;
86 - this.array = new int[length];
87 - if (length > 0) {
88 - int last = length-1;
89 - for (int i = 0; i < last; ++i)
90 - this.array[i] = array[i];
91 - // Do the last write as volatile
92 - unsafe.putIntVolatile(this.array, rawIndex(last), array[last]);
93 - }
92 + // Visibility guaranteed by final field guarantees
93 + this.array = array.clone();
94 94 }
95 95
96 96 /**
97 97 * Returns the length of the array.
98 98 *
99 99 * @return the length of the array
100 100 */
101 101 public final int length() {
102 102 return array.length;
103 103 }
104 104
105 105 /**
106 106 * Gets the current value at position {@code i}.
107 107 *
108 108 * @param i the index
109 109 * @return the current value
110 110 */
111 111 public final int get(int i) {
112 - return unsafe.getIntVolatile(array, rawIndex(i));
112 + return getRaw(checkedByteOffset(i));
113 113 }
114 114
115 + private int getRaw(long offset) {
116 + return unsafe.getIntVolatile(array, offset);
117 + }
118 +
115 119 /**
116 120 * Sets the element at position {@code i} to the given value.
117 121 *
118 122 * @param i the index
119 123 * @param newValue the new value
120 124 */
121 125 public final void set(int i, int newValue) {
122 - unsafe.putIntVolatile(array, rawIndex(i), newValue);
126 + unsafe.putIntVolatile(array, checkedByteOffset(i), newValue);
123 127 }
124 128
125 129 /**
126 130 * Eventually sets the element at position {@code i} to the given value.
127 131 *
128 132 * @param i the index
129 133 * @param newValue the new value
130 134 * @since 1.6
131 135 */
132 136 public final void lazySet(int i, int newValue) {
133 - unsafe.putOrderedInt(array, rawIndex(i), newValue);
137 + unsafe.putOrderedInt(array, checkedByteOffset(i), newValue);
134 138 }
135 139
136 140 /**
137 141 * Atomically sets the element at position {@code i} to the given
138 142 * value and returns the old value.
139 143 *
140 144 * @param i the index
141 145 * @param newValue the new value
142 146 * @return the previous value
143 147 */
144 148 public final int getAndSet(int i, int newValue) {
149 + long offset = checkedByteOffset(i);
145 150 while (true) {
146 - int current = get(i);
147 - if (compareAndSet(i, current, newValue))
151 + int current = getRaw(offset);
152 + if (compareAndSetRaw(offset, current, newValue))
148 153 return current;
149 154 }
150 155 }
151 156
152 157 /**
153 158 * Atomically sets the element at position {@code i} to the given
154 159 * updated value if the current value {@code ==} the expected value.
155 160 *
156 161 * @param i the index
157 162 * @param expect the expected value
158 163 * @param update the new value
159 164 * @return true if successful. False return indicates that
160 165 * the actual value was not equal to the expected value.
161 166 */
162 167 public final boolean compareAndSet(int i, int expect, int update) {
163 - return unsafe.compareAndSwapInt(array, rawIndex(i),
164 - expect, update);
168 + return compareAndSetRaw(checkedByteOffset(i), expect, update);
165 169 }
166 170
171 + private boolean compareAndSetRaw(long offset, int expect, int update) {
172 + return unsafe.compareAndSwapInt(array, offset, expect, update);
173 + }
174 +
167 175 /**
168 176 * Atomically sets the element at position {@code i} to the given
169 177 * updated value if the current value {@code ==} the expected value.
170 178 *
171 179 * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
172 180 * and does not provide ordering guarantees, so is only rarely an
173 181 * appropriate alternative to {@code compareAndSet}.
174 182 *
175 183 * @param i the index
176 184 * @param expect the expected value
177 185 * @param update the new value
178 186 * @return true if successful.
179 187 */
180 188 public final boolean weakCompareAndSet(int i, int expect, int update) {
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181 189 return compareAndSet(i, expect, update);
182 190 }
183 191
184 192 /**
185 193 * Atomically increments by one the element at index {@code i}.
186 194 *
187 195 * @param i the index
188 196 * @return the previous value
189 197 */
190 198 public final int getAndIncrement(int i) {
191 - while (true) {
192 - int current = get(i);
193 - int next = current + 1;
194 - if (compareAndSet(i, current, next))
195 - return current;
196 - }
199 + return getAndAdd(i, 1);
197 200 }
198 201
199 202 /**
200 203 * Atomically decrements by one the element at index {@code i}.
201 204 *
202 205 * @param i the index
203 206 * @return the previous value
204 207 */
205 208 public final int getAndDecrement(int i) {
206 - while (true) {
207 - int current = get(i);
208 - int next = current - 1;
209 - if (compareAndSet(i, current, next))
210 - return current;
211 - }
209 + return getAndAdd(i, -1);
212 210 }
213 211
214 212 /**
215 213 * Atomically adds the given value to the element at index {@code i}.
216 214 *
217 215 * @param i the index
218 216 * @param delta the value to add
219 217 * @return the previous value
220 218 */
221 219 public final int getAndAdd(int i, int delta) {
220 + long offset = checkedByteOffset(i);
222 221 while (true) {
223 - int current = get(i);
224 - int next = current + delta;
225 - if (compareAndSet(i, current, next))
222 + int current = getRaw(offset);
223 + if (compareAndSetRaw(offset, current, current + delta))
226 224 return current;
227 225 }
228 226 }
229 227
230 228 /**
231 229 * Atomically increments by one the element at index {@code i}.
232 230 *
233 231 * @param i the index
234 232 * @return the updated value
235 233 */
236 234 public final int incrementAndGet(int i) {
237 - while (true) {
238 - int current = get(i);
239 - int next = current + 1;
240 - if (compareAndSet(i, current, next))
241 - return next;
242 - }
235 + return addAndGet(i, 1);
243 236 }
244 237
245 238 /**
246 239 * Atomically decrements by one the element at index {@code i}.
247 240 *
248 241 * @param i the index
249 242 * @return the updated value
250 243 */
251 244 public final int decrementAndGet(int i) {
252 - while (true) {
253 - int current = get(i);
254 - int next = current - 1;
255 - if (compareAndSet(i, current, next))
256 - return next;
257 - }
245 + return addAndGet(i, -1);
258 246 }
259 247
260 248 /**
261 249 * Atomically adds the given value to the element at index {@code i}.
262 250 *
263 251 * @param i the index
264 252 * @param delta the value to add
265 253 * @return the updated value
266 254 */
267 255 public final int addAndGet(int i, int delta) {
256 + long offset = checkedByteOffset(i);
268 257 while (true) {
269 - int current = get(i);
258 + int current = getRaw(offset);
270 259 int next = current + delta;
271 - if (compareAndSet(i, current, next))
260 + if (compareAndSetRaw(offset, current, next))
272 261 return next;
273 262 }
274 263 }
275 264
276 265 /**
277 266 * Returns the String representation of the current values of array.
278 - * @return the String representation of the current values of array.
267 + * @return the String representation of the current values of array
279 268 */
280 269 public String toString() {
281 - if (array.length > 0) // force volatile read
282 - get(0);
283 - return Arrays.toString(array);
270 + int iMax = array.length - 1;
271 + if (iMax == -1)
272 + return "[]";
273 +
274 + StringBuilder b = new StringBuilder();
275 + b.append('[');
276 + for (int i = 0; ; i++) {
277 + b.append(getRaw(byteOffset(i)));
278 + if (i == iMax)
279 + return b.append(']').toString();
280 + b.append(',').append(' ');
281 + }
284 282 }
285 283
286 284 }
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