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/licenses/publicdomain 34 */ 35 36 package java.util.concurrent.atomic; 37 import sun.misc.Unsafe; 38 import java.util.*; 39 40 /** 41 * A {@code long} array in which elements may be updated atomically. 42 * See the {@link java.util.concurrent.atomic} package specification 43 * for description of the properties of atomic variables. 44 * @since 1.5 45 * @author Doug Lea 46 */ 47 public class AtomicLongArray implements java.io.Serializable { 48 private static final long serialVersionUID = -2308431214976778248L; 49 50 // setup to use Unsafe.compareAndSwapInt for updates 51 private static final Unsafe unsafe = Unsafe.getUnsafe(); 52 private static final int base = unsafe.arrayBaseOffset(long[].class); 53 private static final int scale = unsafe.arrayIndexScale(long[].class); 54 private final long[] array; 55 56 private long rawIndex(int i) { 57 if (i < 0 || i >= array.length) 58 throw new IndexOutOfBoundsException("index " + i); 59 return base + (long) i * scale; 60 } 61 62 /** 63 * Creates a new AtomicLongArray of given length. 64 * 65 * @param length the length of the array 66 */ 67 public AtomicLongArray(int length) { 68 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 } 73 74 /** 75 * Creates a new AtomicLongArray with the same length as, and 76 * all elements copied from, the given array. 77 * 78 * @param array the array to copy elements from 79 * @throws NullPointerException if array is null 80 */ 81 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 } 93 } 94 95 /** 96 * Returns the length of the array. 97 * 98 * @return the length of the array 99 */ 100 public final int length() { 101 return array.length; 102 } 103 104 /** 105 * Gets the current value at position {@code i}. 106 * 107 * @param i the index 108 * @return the current value 109 */ 110 public final long get(int i) { 111 return unsafe.getLongVolatile(array, rawIndex(i)); 112 } 113 114 /** 115 * Sets the element at position {@code i} to the given value. 116 * 117 * @param i the index 118 * @param newValue the new value 119 */ 120 public final void set(int i, long newValue) { 121 unsafe.putLongVolatile(array, rawIndex(i), newValue); 122 } 123 124 /** 125 * Eventually sets the element at position {@code i} to the given value. 126 * 127 * @param i the index 128 * @param newValue the new value 129 * @since 1.6 130 */ 131 public final void lazySet(int i, long newValue) { 132 unsafe.putOrderedLong(array, rawIndex(i), newValue); 133 } 134 135 136 /** 137 * Atomically sets the element at position {@code i} to the given value 138 * and returns the old value. 139 * 140 * @param i the index 141 * @param newValue the new value 142 * @return the previous value 143 */ 144 public final long getAndSet(int i, long newValue) { 145 while (true) { 146 long current = get(i); 147 if (compareAndSet(i, current, newValue)) 148 return current; 149 } 150 } 151 152 /** 153 * Atomically sets the value to the given updated value 154 * if the current value {@code ==} the expected value. 155 * 156 * @param i the index 157 * @param expect the expected value 158 * @param update the new value 159 * @return true if successful. False return indicates that 160 * the actual value was not equal to the expected value. 161 */ 162 public final boolean compareAndSet(int i, long expect, long update) { 163 return unsafe.compareAndSwapLong(array, rawIndex(i), 164 expect, update); 165 } 166 167 /** 168 * Atomically sets the value to the given updated value 169 * if the current value {@code ==} the expected value. 170 * 171 * <p>May <a href="package-summary.html#Spurious">fail spuriously</a> 172 * and does not provide ordering guarantees, so is only rarely an 173 * appropriate alternative to {@code compareAndSet}. 174 * 175 * @param i the index 176 * @param expect the expected value 177 * @param update the new value 178 * @return true if successful. 179 */ 180 public final boolean weakCompareAndSet(int i, long expect, long update) { 181 return compareAndSet(i, expect, update); 182 } 183 184 /** 185 * Atomically increments by one the element at index {@code i}. 186 * 187 * @param i the index 188 * @return the previous value 189 */ 190 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 } 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 */ 205 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 } 212 } 213 214 /** 215 * Atomically adds the given value to the element at index {@code i}. 216 * 217 * @param i the index 218 * @param delta the value to add 219 * @return the previous value 220 */ 221 public final long getAndAdd(int i, long delta) { 222 while (true) { 223 long current = get(i); 224 long next = current + delta; 225 if (compareAndSet(i, current, next)) 226 return current; 227 } 228 } 229 230 /** 231 * Atomically increments by one the element at index {@code i}. 232 * 233 * @param i the index 234 * @return the updated value 235 */ 236 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 } 243 } 244 245 /** 246 * Atomically decrements by one the element at index {@code i}. 247 * 248 * @param i the index 249 * @return the updated value 250 */ 251 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 } 258 } 259 260 /** 261 * Atomically adds the given value to the element at index {@code i}. 262 * 263 * @param i the index 264 * @param delta the value to add 265 * @return the updated value 266 */ 267 public long addAndGet(int i, long delta) { 268 while (true) { 269 long current = get(i); 270 long next = current + delta; 271 if (compareAndSet(i, current, next)) 272 return next; 273 } 274 } 275 276 /** 277 * Returns the String representation of the current values of array. 278 * @return the String representation of the current values of array. 279 */ 280 public String toString() { 281 if (array.length > 0) // force volatile read 282 get(0); 283 return Arrays.toString(array); 284 } 285 286 } | 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/licenses/publicdomain 34 */ 35 36 package java.util.concurrent.atomic; 37 import sun.misc.Unsafe; 38 import java.util.*; 39 40 /** 41 * A {@code long} array in which elements may be updated atomically. 42 * See the {@link java.util.concurrent.atomic} package specification 43 * for description of the properties of atomic variables. 44 * @since 1.5 45 * @author Doug Lea 46 */ 47 public class AtomicLongArray implements java.io.Serializable { 48 private static final long serialVersionUID = -2308431214976778248L; 49 50 private static final Unsafe unsafe = Unsafe.getUnsafe(); 51 private static final int base = unsafe.arrayBaseOffset(long[].class); 52 private static final int shift; 53 private final long[] array; 54 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) { 63 if (i < 0 || i >= array.length) 64 throw new IndexOutOfBoundsException("index " + i); 65 66 return byteOffset(i); 67 } 68 69 private static long byteOffset(int i) { 70 return ((long) i << shift) + base; 71 } 72 73 /** 74 * Creates a new AtomicLongArray of the given length, with all 75 * elements initially zero. 76 * 77 * @param length the length of the array 78 */ 79 public AtomicLongArray(int length) { 80 array = new long[length]; 81 } 82 83 /** 84 * Creates a new AtomicLongArray with the same length as, and 85 * all elements copied from, the given array. 86 * 87 * @param array the array to copy elements from 88 * @throws NullPointerException if array is null 89 */ 90 public AtomicLongArray(long[] array) { 91 // Visibility guaranteed by final field guarantees 92 this.array = array.clone(); 93 } 94 95 /** 96 * Returns the length of the array. 97 * 98 * @return the length of the array 99 */ 100 public final int length() { 101 return array.length; 102 } 103 104 /** 105 * Gets the current value at position {@code i}. 106 * 107 * @param i the index 108 * @return the current value 109 */ 110 public final long get(int i) { 111 return getRaw(checkedByteOffset(i)); 112 } 113 114 private long getRaw(long offset) { 115 return unsafe.getLongVolatile(array, offset); 116 } 117 118 /** 119 * Sets the element at position {@code i} to the given value. 120 * 121 * @param i the index 122 * @param newValue the new value 123 */ 124 public final void set(int i, long newValue) { 125 unsafe.putLongVolatile(array, checkedByteOffset(i), newValue); 126 } 127 128 /** 129 * Eventually sets the element at position {@code i} to the given value. 130 * 131 * @param i the index 132 * @param newValue the new value 133 * @since 1.6 134 */ 135 public final void lazySet(int i, long newValue) { 136 unsafe.putOrderedLong(array, checkedByteOffset(i), newValue); 137 } 138 139 140 /** 141 * Atomically sets the element at position {@code i} to the given value 142 * and returns the old value. 143 * 144 * @param i the index 145 * @param newValue the new value 146 * @return the previous value 147 */ 148 public final long getAndSet(int i, long newValue) { 149 long offset = checkedByteOffset(i); 150 while (true) { 151 long current = getRaw(offset); 152 if (compareAndSetRaw(offset, current, newValue)) 153 return current; 154 } 155 } 156 157 /** 158 * Atomically sets the element at position {@code i} to the given 159 * updated value if the current value {@code ==} the expected value. 160 * 161 * @param i the index 162 * @param expect the expected value 163 * @param update the new value 164 * @return true if successful. False return indicates that 165 * the actual value was not equal to the expected value. 166 */ 167 public final boolean compareAndSet(int i, long expect, long update) { 168 return compareAndSetRaw(checkedByteOffset(i), expect, update); 169 } 170 171 private boolean compareAndSetRaw(long offset, long expect, long update) { 172 return unsafe.compareAndSwapLong(array, offset, expect, update); 173 } 174 175 /** 176 * Atomically sets the element at position {@code i} to the given 177 * updated value if the current value {@code ==} the expected value. 178 * 179 * <p>May <a href="package-summary.html#Spurious">fail spuriously</a> 180 * and does not provide ordering guarantees, so is only rarely an 181 * appropriate alternative to {@code compareAndSet}. 182 * 183 * @param i the index 184 * @param expect the expected value 185 * @param update the new value 186 * @return true if successful. 187 */ 188 public final boolean weakCompareAndSet(int i, long expect, long update) { 189 return compareAndSet(i, expect, update); 190 } 191 192 /** 193 * Atomically increments by one the element at index {@code i}. 194 * 195 * @param i the index 196 * @return the previous value 197 */ 198 public final long getAndIncrement(int i) { 199 return getAndAdd(i, 1); 200 } 201 202 /** 203 * Atomically decrements by one the element at index {@code i}. 204 * 205 * @param i the index 206 * @return the previous value 207 */ 208 public final long getAndDecrement(int i) { 209 return getAndAdd(i, -1); 210 } 211 212 /** 213 * Atomically adds the given value to the element at index {@code i}. 214 * 215 * @param i the index 216 * @param delta the value to add 217 * @return the previous value 218 */ 219 public final long getAndAdd(int i, long delta) { 220 long offset = checkedByteOffset(i); 221 while (true) { 222 long current = getRaw(offset); 223 if (compareAndSetRaw(offset, current, current + delta)) 224 return current; 225 } 226 } 227 228 /** 229 * Atomically increments by one the element at index {@code i}. 230 * 231 * @param i the index 232 * @return the updated value 233 */ 234 public final long incrementAndGet(int i) { 235 return addAndGet(i, 1); 236 } 237 238 /** 239 * Atomically decrements by one the element at index {@code i}. 240 * 241 * @param i the index 242 * @return the updated value 243 */ 244 public final long decrementAndGet(int i) { 245 return addAndGet(i, -1); 246 } 247 248 /** 249 * Atomically adds the given value to the element at index {@code i}. 250 * 251 * @param i the index 252 * @param delta the value to add 253 * @return the updated value 254 */ 255 public long addAndGet(int i, long delta) { 256 long offset = checkedByteOffset(i); 257 while (true) { 258 long current = getRaw(offset); 259 long next = current + delta; 260 if (compareAndSetRaw(offset, current, next)) 261 return next; 262 } 263 } 264 265 /** 266 * Returns the String representation of the current values of array. 267 * @return the String representation of the current values of array 268 */ 269 public String toString() { 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 } 282 } 283 284 } |