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--- old/src/share/classes/java/util/concurrent/atomic/AtomicLongArray.java
+++ new/src/share/classes/java/util/concurrent/atomic/AtomicLongArray.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
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39 lines elided |
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40 40 /**
41 41 * A {@code long} array in which elements may be updated atomically.
42 42 * See the {@link java.util.concurrent.atomic} package specification
43 43 * for description of the properties of atomic variables.
44 44 * @since 1.5
45 45 * @author Doug Lea
46 46 */
47 47 public class AtomicLongArray implements java.io.Serializable {
48 48 private static final long serialVersionUID = -2308431214976778248L;
49 49
50 - // setup to use Unsafe.compareAndSwapInt for updates
51 50 private static final Unsafe unsafe = Unsafe.getUnsafe();
52 51 private static final int base = unsafe.arrayBaseOffset(long[].class);
53 - private static final int scale = unsafe.arrayIndexScale(long[].class);
52 + private static final int shift;
54 53 private final long[] array;
55 54
56 - private long rawIndex(int i) {
55 + static {
56 + int scale = unsafe.arrayIndexScale(long[].class);
57 + if ((scale & (scale - 1)) != 0)
58 + throw new Error("data type scale not a power of two");
59 + shift = 31 - Integer.numberOfLeadingZeros(scale);
60 + }
61 +
62 + private long checkedByteOffset(int i) {
57 63 if (i < 0 || i >= array.length)
58 64 throw new IndexOutOfBoundsException("index " + i);
59 - return base + (long) i * scale;
65 +
66 + return byteOffset(i);
60 67 }
61 68
69 + private static long byteOffset(int i) {
70 + return ((long) i << shift) + base;
71 + }
72 +
62 73 /**
63 - * Creates a new AtomicLongArray of given length.
74 + * Creates a new AtomicLongArray of the given length, with all
75 + * elements initially zero.
64 76 *
65 77 * @param length the length of the array
66 78 */
67 79 public AtomicLongArray(int length) {
68 80 array = new long[length];
69 - // must perform at least one volatile write to conform to JMM
70 - if (length > 0)
71 - unsafe.putLongVolatile(array, rawIndex(0), 0);
72 81 }
73 82
74 83 /**
75 84 * Creates a new AtomicLongArray with the same length as, and
76 85 * all elements copied from, the given array.
77 86 *
78 87 * @param array the array to copy elements from
79 88 * @throws NullPointerException if array is null
80 89 */
81 90 public AtomicLongArray(long[] array) {
82 - if (array == null)
83 - throw new NullPointerException();
84 - int length = array.length;
85 - this.array = new long[length];
86 - if (length > 0) {
87 - int last = length-1;
88 - for (int i = 0; i < last; ++i)
89 - this.array[i] = array[i];
90 - // Do the last write as volatile
91 - unsafe.putLongVolatile(this.array, rawIndex(last), array[last]);
92 - }
91 + // Visibility guaranteed by final field guarantees
92 + this.array = array.clone();
93 93 }
94 94
95 95 /**
96 96 * Returns the length of the array.
97 97 *
98 98 * @return the length of the array
99 99 */
100 100 public final int length() {
101 101 return array.length;
102 102 }
103 103
104 104 /**
105 105 * Gets the current value at position {@code i}.
106 106 *
107 107 * @param i the index
108 108 * @return the current value
109 109 */
110 110 public final long get(int i) {
111 - return unsafe.getLongVolatile(array, rawIndex(i));
111 + return getRaw(checkedByteOffset(i));
112 112 }
113 113
114 + private long getRaw(long offset) {
115 + return unsafe.getLongVolatile(array, offset);
116 + }
117 +
114 118 /**
115 119 * Sets the element at position {@code i} to the given value.
116 120 *
117 121 * @param i the index
118 122 * @param newValue the new value
119 123 */
120 124 public final void set(int i, long newValue) {
121 - unsafe.putLongVolatile(array, rawIndex(i), newValue);
125 + unsafe.putLongVolatile(array, checkedByteOffset(i), newValue);
122 126 }
123 127
124 128 /**
125 129 * Eventually sets the element at position {@code i} to the given value.
126 130 *
127 131 * @param i the index
128 132 * @param newValue the new value
129 133 * @since 1.6
130 134 */
131 135 public final void lazySet(int i, long newValue) {
132 - unsafe.putOrderedLong(array, rawIndex(i), newValue);
136 + unsafe.putOrderedLong(array, checkedByteOffset(i), newValue);
133 137 }
134 138
135 139
136 140 /**
137 141 * Atomically sets the element at position {@code i} to the given value
138 142 * 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 long getAndSet(int i, long newValue) {
149 + long offset = checkedByteOffset(i);
145 150 while (true) {
146 - long current = get(i);
147 - if (compareAndSet(i, current, newValue))
151 + long current = getRaw(offset);
152 + if (compareAndSetRaw(offset, current, newValue))
148 153 return current;
149 154 }
150 155 }
151 156
152 157 /**
153 - * Atomically sets the value to the given updated value
154 - * if the current value {@code ==} the expected value.
158 + * Atomically sets the element at position {@code i} to the given
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, long expect, long update) {
163 - return unsafe.compareAndSwapLong(array, rawIndex(i),
164 - expect, update);
168 + return compareAndSetRaw(checkedByteOffset(i), expect, update);
165 169 }
166 170
171 + private boolean compareAndSetRaw(long offset, long expect, long update) {
172 + return unsafe.compareAndSwapLong(array, offset, expect, update);
173 + }
174 +
167 175 /**
168 - * Atomically sets the value to the given updated value
169 - * if the current value {@code ==} the expected value.
176 + * Atomically sets the element at position {@code i} to the given
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, long expect, long 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 long getAndIncrement(int i) {
191 - while (true) {
192 - long current = get(i);
193 - long 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 long getAndDecrement(int i) {
206 - while (true) {
207 - long current = get(i);
208 - long 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 long getAndAdd(int i, long delta) {
220 + long offset = checkedByteOffset(i);
222 221 while (true) {
223 - long current = get(i);
224 - long next = current + delta;
225 - if (compareAndSet(i, current, next))
222 + long 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 long incrementAndGet(int i) {
237 - while (true) {
238 - long current = get(i);
239 - long 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 long decrementAndGet(int i) {
252 - while (true) {
253 - long current = get(i);
254 - long 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 long addAndGet(int i, long delta) {
256 + long offset = checkedByteOffset(i);
268 257 while (true) {
269 - long current = get(i);
258 + long current = getRaw(offset);
270 259 long 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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