src/share/classes/java/util/concurrent/atomic/AtomicLongArray.java

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  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 }