rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicReferenceArray.java
1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicReferenceArray.java Thu Oct 03 15:40:35 2013 +0200
1.3 @@ -0,0 +1,213 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.6 + *
1.7 + * This code is free software; you can redistribute it and/or modify it
1.8 + * under the terms of the GNU General Public License version 2 only, as
1.9 + * published by the Free Software Foundation. Oracle designates this
1.10 + * particular file as subject to the "Classpath" exception as provided
1.11 + * by Oracle in the LICENSE file that accompanied this code.
1.12 + *
1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.15 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.16 + * version 2 for more details (a copy is included in the LICENSE file that
1.17 + * accompanied this code).
1.18 + *
1.19 + * You should have received a copy of the GNU General Public License version
1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.22 + *
1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.24 + * or visit www.oracle.com if you need additional information or have any
1.25 + * questions.
1.26 + */
1.27 +
1.28 +/*
1.29 + * This file is available under and governed by the GNU General Public
1.30 + * License version 2 only, as published by the Free Software Foundation.
1.31 + * However, the following notice accompanied the original version of this
1.32 + * file:
1.33 + *
1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
1.35 + * Expert Group and released to the public domain, as explained at
1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
1.37 + */
1.38 +
1.39 +package java.util.concurrent.atomic;
1.40 +import sun.misc.Unsafe;
1.41 +import java.util.*;
1.42 +
1.43 +/**
1.44 + * An array of object references in which elements may be updated
1.45 + * atomically. See the {@link java.util.concurrent.atomic} package
1.46 + * specification for description of the properties of atomic
1.47 + * variables.
1.48 + * @since 1.5
1.49 + * @author Doug Lea
1.50 + * @param <E> The base class of elements held in this array
1.51 + */
1.52 +public class AtomicReferenceArray<E> implements java.io.Serializable {
1.53 + private static final long serialVersionUID = -6209656149925076980L;
1.54 +
1.55 + private static final Unsafe unsafe = Unsafe.getUnsafe();
1.56 + private static final int base = unsafe.arrayBaseOffset(Object[].class);
1.57 + private static final int shift;
1.58 + private final Object[] array;
1.59 +
1.60 + static {
1.61 + int scale = unsafe.arrayIndexScale(Object[].class);
1.62 + if ((scale & (scale - 1)) != 0)
1.63 + throw new Error("data type scale not a power of two");
1.64 + shift = 31 - Integer.numberOfLeadingZeros(scale);
1.65 + }
1.66 +
1.67 + private long checkedByteOffset(int i) {
1.68 + if (i < 0 || i >= array.length)
1.69 + throw new IndexOutOfBoundsException("index " + i);
1.70 +
1.71 + return byteOffset(i);
1.72 + }
1.73 +
1.74 + private static long byteOffset(int i) {
1.75 + return ((long) i << shift) + base;
1.76 + }
1.77 +
1.78 + /**
1.79 + * Creates a new AtomicReferenceArray of the given length, with all
1.80 + * elements initially null.
1.81 + *
1.82 + * @param length the length of the array
1.83 + */
1.84 + public AtomicReferenceArray(int length) {
1.85 + array = new Object[length];
1.86 + }
1.87 +
1.88 + /**
1.89 + * Creates a new AtomicReferenceArray with the same length as, and
1.90 + * all elements copied from, the given array.
1.91 + *
1.92 + * @param array the array to copy elements from
1.93 + * @throws NullPointerException if array is null
1.94 + */
1.95 + public AtomicReferenceArray(E[] array) {
1.96 + // Visibility guaranteed by final field guarantees
1.97 + this.array = array.clone();
1.98 + }
1.99 +
1.100 + /**
1.101 + * Returns the length of the array.
1.102 + *
1.103 + * @return the length of the array
1.104 + */
1.105 + public final int length() {
1.106 + return array.length;
1.107 + }
1.108 +
1.109 + /**
1.110 + * Gets the current value at position {@code i}.
1.111 + *
1.112 + * @param i the index
1.113 + * @return the current value
1.114 + */
1.115 + public final E get(int i) {
1.116 + return getRaw(checkedByteOffset(i));
1.117 + }
1.118 +
1.119 + private E getRaw(long offset) {
1.120 + return (E) unsafe.getObjectVolatile(array, offset);
1.121 + }
1.122 +
1.123 + /**
1.124 + * Sets the element at position {@code i} to the given value.
1.125 + *
1.126 + * @param i the index
1.127 + * @param newValue the new value
1.128 + */
1.129 + public final void set(int i, E newValue) {
1.130 + unsafe.putObjectVolatile(array, checkedByteOffset(i), newValue);
1.131 + }
1.132 +
1.133 + /**
1.134 + * Eventually sets the element at position {@code i} to the given value.
1.135 + *
1.136 + * @param i the index
1.137 + * @param newValue the new value
1.138 + * @since 1.6
1.139 + */
1.140 + public final void lazySet(int i, E newValue) {
1.141 + unsafe.putOrderedObject(array, checkedByteOffset(i), newValue);
1.142 + }
1.143 +
1.144 +
1.145 + /**
1.146 + * Atomically sets the element at position {@code i} to the given
1.147 + * value and returns the old value.
1.148 + *
1.149 + * @param i the index
1.150 + * @param newValue the new value
1.151 + * @return the previous value
1.152 + */
1.153 + public final E getAndSet(int i, E newValue) {
1.154 + long offset = checkedByteOffset(i);
1.155 + while (true) {
1.156 + E current = (E) getRaw(offset);
1.157 + if (compareAndSetRaw(offset, current, newValue))
1.158 + return current;
1.159 + }
1.160 + }
1.161 +
1.162 + /**
1.163 + * Atomically sets the element at position {@code i} to the given
1.164 + * updated value if the current value {@code ==} the expected value.
1.165 + *
1.166 + * @param i the index
1.167 + * @param expect the expected value
1.168 + * @param update the new value
1.169 + * @return true if successful. False return indicates that
1.170 + * the actual value was not equal to the expected value.
1.171 + */
1.172 + public final boolean compareAndSet(int i, E expect, E update) {
1.173 + return compareAndSetRaw(checkedByteOffset(i), expect, update);
1.174 + }
1.175 +
1.176 + private boolean compareAndSetRaw(long offset, E expect, E update) {
1.177 + return unsafe.compareAndSwapObject(array, offset, expect, update);
1.178 + }
1.179 +
1.180 + /**
1.181 + * Atomically sets the element at position {@code i} to the given
1.182 + * updated value if the current value {@code ==} the expected value.
1.183 + *
1.184 + * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
1.185 + * and does not provide ordering guarantees, so is only rarely an
1.186 + * appropriate alternative to {@code compareAndSet}.
1.187 + *
1.188 + * @param i the index
1.189 + * @param expect the expected value
1.190 + * @param update the new value
1.191 + * @return true if successful.
1.192 + */
1.193 + public final boolean weakCompareAndSet(int i, E expect, E update) {
1.194 + return compareAndSet(i, expect, update);
1.195 + }
1.196 +
1.197 + /**
1.198 + * Returns the String representation of the current values of array.
1.199 + * @return the String representation of the current values of array
1.200 + */
1.201 + public String toString() {
1.202 + int iMax = array.length - 1;
1.203 + if (iMax == -1)
1.204 + return "[]";
1.205 +
1.206 + StringBuilder b = new StringBuilder();
1.207 + b.append('[');
1.208 + for (int i = 0; ; i++) {
1.209 + b.append(getRaw(byteOffset(i)));
1.210 + if (i == iMax)
1.211 + return b.append(']').toString();
1.212 + b.append(',').append(' ');
1.213 + }
1.214 + }
1.215 +
1.216 +}