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  * An {@code int} array in which elements may be updated atomically.
  42  * See the {@link java.util.concurrent.atomic} package
  43  * specification for description of the properties of atomic
  44  * variables.
  45  * @since 1.5
  46  * @author Doug Lea
  47  */
  48 public class AtomicIntegerArray implements java.io.Serializable {
  49     private static final long serialVersionUID = 2862133569453604235L;
  50 
  51    // setup to use Unsafe.compareAndSwapInt for updates
  52     private static final Unsafe unsafe = Unsafe.getUnsafe();
  53     private static final int base = unsafe.arrayBaseOffset(int[].class);
  54     private static final int scale = unsafe.arrayIndexScale(int[].class);
  55     private final int[] array;
  56 
  57     private long rawIndex(int i) {







  58         if (i < 0 || i >= array.length)
  59             throw new IndexOutOfBoundsException("index " + i);
  60         return base + (long) i * scale;

  61     }
  62 




  63     /**
  64      * Creates a new AtomicIntegerArray of given length.

  65      *
  66      * @param length the length of the array
  67      */
  68     public AtomicIntegerArray(int length) {
  69         array = new int[length];
  70         // must perform at least one volatile write to conform to JMM
  71         if (length > 0)
  72             unsafe.putIntVolatile(array, rawIndex(0), 0);
  73     }
  74 
  75     /**
  76      * Creates a new AtomicIntegerArray with the same length as, and
  77      * all elements copied from, the given array.
  78      *
  79      * @param array the array to copy elements from
  80      * @throws NullPointerException if array is null
  81      */
  82     public AtomicIntegerArray(int[] array) {
  83         if (array == null)
  84             throw new NullPointerException();
  85         int length = array.length;
  86         this.array = new int[length];
  87         if (length > 0) {
  88             int last = length-1;
  89             for (int i = 0; i < last; ++i)
  90                 this.array[i] = array[i];
  91             // Do the last write as volatile
  92             unsafe.putIntVolatile(this.array, rawIndex(last), array[last]);
  93         }
  94     }
  95 
  96     /**
  97      * Returns the length of the array.
  98      *
  99      * @return the length of the array
 100      */
 101     public final int length() {
 102         return array.length;
 103     }
 104 
 105     /**
 106      * Gets the current value at position {@code i}.
 107      *
 108      * @param i the index
 109      * @return the current value
 110      */
 111     public final int get(int i) {
 112         return unsafe.getIntVolatile(array, rawIndex(i));
 113     }
 114 




 115     /**
 116      * Sets the element at position {@code i} to the given value.
 117      *
 118      * @param i the index
 119      * @param newValue the new value
 120      */
 121     public final void set(int i, int newValue) {
 122         unsafe.putIntVolatile(array, rawIndex(i), newValue);
 123     }
 124 
 125     /**
 126      * Eventually sets the element at position {@code i} to the given value.
 127      *
 128      * @param i the index
 129      * @param newValue the new value
 130      * @since 1.6
 131      */
 132     public final void lazySet(int i, int newValue) {
 133         unsafe.putOrderedInt(array, rawIndex(i), newValue);
 134     }
 135 
 136     /**
 137      * Atomically sets the element at position {@code i} to the given
 138      * value 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 int getAndSet(int i, int newValue) {

 145         while (true) {
 146             int current = get(i);
 147             if (compareAndSet(i, current, newValue))
 148                 return current;
 149         }
 150     }
 151 
 152     /**
 153      * Atomically sets the element at position {@code i} to the given
 154      * updated value 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, int expect, int update) {
 163         return unsafe.compareAndSwapInt(array, rawIndex(i),
 164                                         expect, update);
 165     }
 166 




 167     /**
 168      * Atomically sets the element at position {@code i} to the given
 169      * updated value 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, int expect, int 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 int getAndIncrement(int i) {
 191         while (true) {
 192             int current = get(i);
 193             int 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 int getAndDecrement(int i) {
 206         while (true) {
 207             int current = get(i);
 208             int 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 int getAndAdd(int i, int delta) {

 222         while (true) {
 223             int current = get(i);
 224             int 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 int incrementAndGet(int i) {
 237         while (true) {
 238             int current = get(i);
 239             int 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 int decrementAndGet(int i) {
 252         while (true) {
 253             int current = get(i);
 254             int 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 final int addAndGet(int i, int delta) {

 268         while (true) {
 269             int current = get(i);
 270             int 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 }
--- EOF ---