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/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 }
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