1 /* 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. Oracle designates this 7 * particular file as subject to the "Classpath" exception as provided 8 * by Oracle in the LICENSE file that accompanied this code. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 */ 24 25 /* 26 * This file is available under and governed by the GNU General Public 27 * License version 2 only, as published by the Free Software Foundation. 28 * However, the following notice accompanied the original version of this 29 * file: 30 * 31 * Written by Doug Lea with assistance from members of JCP JSR-166 32 * Expert Group and released to the public domain, as explained at 33 * http://creativecommons.org/publicdomain/zero/1.0/ 34 */ 35 36 package java.util.concurrent.atomic; 37 38 import java.util.function.IntBinaryOperator; 39 import java.util.function.IntUnaryOperator; 40 41 /** 42 * An {@code int} array in which elements may be updated atomically. 43 * See the {@link java.util.concurrent.atomic} package 44 * specification for description of the properties of atomic 45 * variables. 46 * @since 1.5 47 * @author Doug Lea 48 */ 49 public class AtomicIntegerArray implements java.io.Serializable { 50 private static final long serialVersionUID = 2862133569453604235L; 51 52 private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe(); 53 private static final int ABASE; 54 private static final int ASHIFT; 55 private final int[] array; 56 57 static { 58 ABASE = U.arrayBaseOffset(int[].class); 59 int scale = U.arrayIndexScale(int[].class); 60 if ((scale & (scale - 1)) != 0) 61 throw new Error("array index scale not a power of two"); 62 ASHIFT = 31 - Integer.numberOfLeadingZeros(scale); 63 } 64 checkedByteOffset(int i)65 private long checkedByteOffset(int i) { 66 if (i < 0 || i >= array.length) 67 throw new IndexOutOfBoundsException("index " + i); 68 69 return byteOffset(i); 70 } 71 byteOffset(int i)72 private static long byteOffset(int i) { 73 return ((long) i << ASHIFT) + ABASE; 74 } 75 76 /** 77 * Creates a new AtomicIntegerArray of the given length, with all 78 * elements initially zero. 79 * 80 * @param length the length of the array 81 */ AtomicIntegerArray(int length)82 public AtomicIntegerArray(int length) { 83 array = new int[length]; 84 } 85 86 /** 87 * Creates a new AtomicIntegerArray with the same length as, and 88 * all elements copied from, the given array. 89 * 90 * @param array the array to copy elements from 91 * @throws NullPointerException if array is null 92 */ AtomicIntegerArray(int[] array)93 public AtomicIntegerArray(int[] array) { 94 // Visibility guaranteed by final field guarantees 95 this.array = array.clone(); 96 } 97 98 /** 99 * Returns the length of the array. 100 * 101 * @return the length of the array 102 */ length()103 public final int length() { 104 return array.length; 105 } 106 107 /** 108 * Gets the current value at position {@code i}. 109 * 110 * @param i the index 111 * @return the current value 112 */ get(int i)113 public final int get(int i) { 114 return getRaw(checkedByteOffset(i)); 115 } 116 getRaw(long offset)117 private int getRaw(long offset) { 118 return U.getIntVolatile(array, offset); 119 } 120 121 /** 122 * Sets the element at position {@code i} to the given value. 123 * 124 * @param i the index 125 * @param newValue the new value 126 */ set(int i, int newValue)127 public final void set(int i, int newValue) { 128 U.putIntVolatile(array, checkedByteOffset(i), newValue); 129 } 130 131 /** 132 * Eventually sets the element at position {@code i} to the given value. 133 * 134 * @param i the index 135 * @param newValue the new value 136 * @since 1.6 137 */ lazySet(int i, int newValue)138 public final void lazySet(int i, int newValue) { 139 U.putOrderedInt(array, checkedByteOffset(i), newValue); 140 } 141 142 /** 143 * Atomically sets the element at position {@code i} to the given 144 * value and returns the old value. 145 * 146 * @param i the index 147 * @param newValue the new value 148 * @return the previous value 149 */ getAndSet(int i, int newValue)150 public final int getAndSet(int i, int newValue) { 151 return U.getAndSetInt(array, checkedByteOffset(i), newValue); 152 } 153 154 /** 155 * Atomically sets the element at position {@code i} to the given 156 * updated value if the current value {@code ==} the expected value. 157 * 158 * @param i the index 159 * @param expect the expected value 160 * @param update the new value 161 * @return {@code true} if successful. False return indicates that 162 * the actual value was not equal to the expected value. 163 */ compareAndSet(int i, int expect, int update)164 public final boolean compareAndSet(int i, int expect, int update) { 165 return compareAndSetRaw(checkedByteOffset(i), expect, update); 166 } 167 compareAndSetRaw(long offset, int expect, int update)168 private boolean compareAndSetRaw(long offset, int expect, int update) { 169 return U.compareAndSwapInt(array, offset, expect, update); 170 } 171 172 /** 173 * Atomically sets the element at position {@code i} to the given 174 * updated value if the current value {@code ==} the expected value. 175 * 176 * <p><a href="package-summary.html#weakCompareAndSet">May fail 177 * spuriously and does not provide ordering guarantees</a>, so is 178 * only rarely an appropriate alternative to {@code compareAndSet}. 179 * 180 * @param i the index 181 * @param expect the expected value 182 * @param update the new value 183 * @return {@code true} if successful 184 */ weakCompareAndSet(int i, int expect, int update)185 public final boolean weakCompareAndSet(int i, int expect, int update) { 186 return compareAndSet(i, expect, update); 187 } 188 189 /** 190 * Atomically increments by one the element at index {@code i}. 191 * 192 * @param i the index 193 * @return the previous value 194 */ getAndIncrement(int i)195 public final int getAndIncrement(int i) { 196 return getAndAdd(i, 1); 197 } 198 199 /** 200 * Atomically decrements by one the element at index {@code i}. 201 * 202 * @param i the index 203 * @return the previous value 204 */ getAndDecrement(int i)205 public final int getAndDecrement(int i) { 206 return getAndAdd(i, -1); 207 } 208 209 /** 210 * Atomically adds the given value to the element at index {@code i}. 211 * 212 * @param i the index 213 * @param delta the value to add 214 * @return the previous value 215 */ getAndAdd(int i, int delta)216 public final int getAndAdd(int i, int delta) { 217 return U.getAndAddInt(array, checkedByteOffset(i), delta); 218 } 219 220 /** 221 * Atomically increments by one the element at index {@code i}. 222 * 223 * @param i the index 224 * @return the updated value 225 */ incrementAndGet(int i)226 public final int incrementAndGet(int i) { 227 return getAndAdd(i, 1) + 1; 228 } 229 230 /** 231 * Atomically decrements by one the element at index {@code i}. 232 * 233 * @param i the index 234 * @return the updated value 235 */ decrementAndGet(int i)236 public final int decrementAndGet(int i) { 237 return getAndAdd(i, -1) - 1; 238 } 239 240 /** 241 * Atomically adds the given value to the element at index {@code i}. 242 * 243 * @param i the index 244 * @param delta the value to add 245 * @return the updated value 246 */ addAndGet(int i, int delta)247 public final int addAndGet(int i, int delta) { 248 return getAndAdd(i, delta) + delta; 249 } 250 251 /** 252 * Atomically updates the element at index {@code i} with the results 253 * of applying the given function, returning the previous value. The 254 * function should be side-effect-free, since it may be re-applied 255 * when attempted updates fail due to contention among threads. 256 * 257 * @param i the index 258 * @param updateFunction a side-effect-free function 259 * @return the previous value 260 * @since 1.8 261 */ getAndUpdate(int i, IntUnaryOperator updateFunction)262 public final int getAndUpdate(int i, IntUnaryOperator updateFunction) { 263 long offset = checkedByteOffset(i); 264 int prev, next; 265 do { 266 prev = getRaw(offset); 267 next = updateFunction.applyAsInt(prev); 268 } while (!compareAndSetRaw(offset, prev, next)); 269 return prev; 270 } 271 272 /** 273 * Atomically updates the element at index {@code i} with the results 274 * of applying the given function, returning the updated value. The 275 * function should be side-effect-free, since it may be re-applied 276 * when attempted updates fail due to contention among threads. 277 * 278 * @param i the index 279 * @param updateFunction a side-effect-free function 280 * @return the updated value 281 * @since 1.8 282 */ updateAndGet(int i, IntUnaryOperator updateFunction)283 public final int updateAndGet(int i, IntUnaryOperator updateFunction) { 284 long offset = checkedByteOffset(i); 285 int prev, next; 286 do { 287 prev = getRaw(offset); 288 next = updateFunction.applyAsInt(prev); 289 } while (!compareAndSetRaw(offset, prev, next)); 290 return next; 291 } 292 293 /** 294 * Atomically updates the element at index {@code i} with the 295 * results of applying the given function to the current and 296 * given values, returning the previous value. The function should 297 * be side-effect-free, since it may be re-applied when attempted 298 * updates fail due to contention among threads. The function is 299 * applied with the current value at index {@code i} as its first 300 * argument, and the given update as the second argument. 301 * 302 * @param i the index 303 * @param x the update value 304 * @param accumulatorFunction a side-effect-free function of two arguments 305 * @return the previous value 306 * @since 1.8 307 */ getAndAccumulate(int i, int x, IntBinaryOperator accumulatorFunction)308 public final int getAndAccumulate(int i, int x, 309 IntBinaryOperator accumulatorFunction) { 310 long offset = checkedByteOffset(i); 311 int prev, next; 312 do { 313 prev = getRaw(offset); 314 next = accumulatorFunction.applyAsInt(prev, x); 315 } while (!compareAndSetRaw(offset, prev, next)); 316 return prev; 317 } 318 319 /** 320 * Atomically updates the element at index {@code i} with the 321 * results of applying the given function to the current and 322 * given values, returning the updated value. The function should 323 * be side-effect-free, since it may be re-applied when attempted 324 * updates fail due to contention among threads. The function is 325 * applied with the current value at index {@code i} as its first 326 * argument, and the given update as the second argument. 327 * 328 * @param i the index 329 * @param x the update value 330 * @param accumulatorFunction a side-effect-free function of two arguments 331 * @return the updated value 332 * @since 1.8 333 */ accumulateAndGet(int i, int x, IntBinaryOperator accumulatorFunction)334 public final int accumulateAndGet(int i, int x, 335 IntBinaryOperator accumulatorFunction) { 336 long offset = checkedByteOffset(i); 337 int prev, next; 338 do { 339 prev = getRaw(offset); 340 next = accumulatorFunction.applyAsInt(prev, x); 341 } while (!compareAndSetRaw(offset, prev, next)); 342 return next; 343 } 344 345 /** 346 * Returns the String representation of the current values of array. 347 * @return the String representation of the current values of array 348 */ toString()349 public String toString() { 350 int iMax = array.length - 1; 351 if (iMax == -1) 352 return "[]"; 353 354 StringBuilder b = new StringBuilder(); 355 b.append('['); 356 for (int i = 0; ; i++) { 357 b.append(getRaw(byteOffset(i))); 358 if (i == iMax) 359 return b.append(']').toString(); 360 b.append(',').append(' '); 361 } 362 } 363 364 } 365