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/AtomicReference.java Thu Oct 03 15:40:35 2013 +0200
1.3 @@ -0,0 +1,155 @@
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 +
1.42 +/**
1.43 + * An object reference that may be updated atomically. See the {@link
1.44 + * java.util.concurrent.atomic} package specification for description
1.45 + * of the properties of atomic variables.
1.46 + * @since 1.5
1.47 + * @author Doug Lea
1.48 + * @param <V> The type of object referred to by this reference
1.49 + */
1.50 +public class AtomicReference<V> implements java.io.Serializable {
1.51 + private static final long serialVersionUID = -1848883965231344442L;
1.52 +
1.53 + private static final Unsafe unsafe = Unsafe.getUnsafe();
1.54 + private static final long valueOffset;
1.55 +
1.56 + static {
1.57 + try {
1.58 + valueOffset = unsafe.objectFieldOffset
1.59 + (AtomicReference.class.getDeclaredField("value"));
1.60 + } catch (Exception ex) { throw new Error(ex); }
1.61 + }
1.62 +
1.63 + private volatile V value;
1.64 +
1.65 + /**
1.66 + * Creates a new AtomicReference with the given initial value.
1.67 + *
1.68 + * @param initialValue the initial value
1.69 + */
1.70 + public AtomicReference(V initialValue) {
1.71 + value = initialValue;
1.72 + }
1.73 +
1.74 + /**
1.75 + * Creates a new AtomicReference with null initial value.
1.76 + */
1.77 + public AtomicReference() {
1.78 + }
1.79 +
1.80 + /**
1.81 + * Gets the current value.
1.82 + *
1.83 + * @return the current value
1.84 + */
1.85 + public final V get() {
1.86 + return value;
1.87 + }
1.88 +
1.89 + /**
1.90 + * Sets to the given value.
1.91 + *
1.92 + * @param newValue the new value
1.93 + */
1.94 + public final void set(V newValue) {
1.95 + value = newValue;
1.96 + }
1.97 +
1.98 + /**
1.99 + * Eventually sets to the given value.
1.100 + *
1.101 + * @param newValue the new value
1.102 + * @since 1.6
1.103 + */
1.104 + public final void lazySet(V newValue) {
1.105 + unsafe.putOrderedObject(this, valueOffset, newValue);
1.106 + }
1.107 +
1.108 + /**
1.109 + * Atomically sets the value to the given updated value
1.110 + * if the current value {@code ==} the expected value.
1.111 + * @param expect the expected value
1.112 + * @param update the new value
1.113 + * @return true if successful. False return indicates that
1.114 + * the actual value was not equal to the expected value.
1.115 + */
1.116 + public final boolean compareAndSet(V expect, V update) {
1.117 + return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
1.118 + }
1.119 +
1.120 + /**
1.121 + * Atomically sets the value to the given updated value
1.122 + * if the current value {@code ==} the expected value.
1.123 + *
1.124 + * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
1.125 + * and does not provide ordering guarantees, so is only rarely an
1.126 + * appropriate alternative to {@code compareAndSet}.
1.127 + *
1.128 + * @param expect the expected value
1.129 + * @param update the new value
1.130 + * @return true if successful.
1.131 + */
1.132 + public final boolean weakCompareAndSet(V expect, V update) {
1.133 + return unsafe.compareAndSwapObject(this, valueOffset, expect, update);
1.134 + }
1.135 +
1.136 + /**
1.137 + * Atomically sets to the given value and returns the old value.
1.138 + *
1.139 + * @param newValue the new value
1.140 + * @return the previous value
1.141 + */
1.142 + public final V getAndSet(V newValue) {
1.143 + while (true) {
1.144 + V x = get();
1.145 + if (compareAndSet(x, newValue))
1.146 + return x;
1.147 + }
1.148 + }
1.149 +
1.150 + /**
1.151 + * Returns the String representation of the current value.
1.152 + * @return the String representation of the current value.
1.153 + */
1.154 + public String toString() {
1.155 + return String.valueOf(get());
1.156 + }
1.157 +
1.158 +}