--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,346 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+/*
+ * This file is available under and governed by the GNU General Public
+ * License version 2 only, as published by the Free Software Foundation.
+ * However, the following notice accompanied the original version of this
+ * file:
+ *
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/licenses/publicdomain
+ */
+
+package java.util.concurrent.atomic;
+import sun.misc.Unsafe;
+import java.lang.reflect.*;
+
+/**
+ * A reflection-based utility that enables atomic updates to
+ * designated {@code volatile int} fields of designated classes.
+ * This class is designed for use in atomic data structures in which
+ * several fields of the same node are independently subject to atomic
+ * updates.
+ *
+ * <p>Note that the guarantees of the {@code compareAndSet}
+ * method in this class are weaker than in other atomic classes.
+ * Because this class cannot ensure that all uses of the field
+ * are appropriate for purposes of atomic access, it can
+ * guarantee atomicity only with respect to other invocations of
+ * {@code compareAndSet} and {@code set} on the same updater.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <T> The type of the object holding the updatable field
+ */
+public abstract class AtomicIntegerFieldUpdater<T> {
+ /**
+ * Creates and returns an updater for objects with the given field.
+ * The Class argument is needed to check that reflective types and
+ * generic types match.
+ *
+ * @param tclass the class of the objects holding the field
+ * @param fieldName the name of the field to be updated
+ * @return the updater
+ * @throws IllegalArgumentException if the field is not a
+ * volatile integer type
+ * @throws RuntimeException with a nested reflection-based
+ * exception if the class does not hold field or is the wrong type
+ */
+ public static <U> AtomicIntegerFieldUpdater<U> newUpdater(Class<U> tclass, String fieldName) {
+ return new AtomicIntegerFieldUpdaterImpl<U>(tclass, fieldName);
+ }
+
+ /**
+ * Protected do-nothing constructor for use by subclasses.
+ */
+ protected AtomicIntegerFieldUpdater() {
+ }
+
+ /**
+ * Atomically sets the field of the given object managed by this updater
+ * to the given updated value if the current value {@code ==} the
+ * expected value. This method is guaranteed to be atomic with respect to
+ * other calls to {@code compareAndSet} and {@code set}, but not
+ * necessarily with respect to other changes in the field.
+ *
+ * @param obj An object whose field to conditionally set
+ * @param expect the expected value
+ * @param update the new value
+ * @return true if successful
+ * @throws ClassCastException if {@code obj} is not an instance
+ * of the class possessing the field established in the constructor
+ */
+ public abstract boolean compareAndSet(T obj, int expect, int update);
+
+ /**
+ * Atomically sets the field of the given object managed by this updater
+ * to the given updated value if the current value {@code ==} the
+ * expected value. This method is guaranteed to be atomic with respect to
+ * other calls to {@code compareAndSet} and {@code set}, but not
+ * necessarily with respect to other changes in the field.
+ *
+ * <p>May <a href="package-summary.html#Spurious">fail spuriously</a>
+ * and does not provide ordering guarantees, so is only rarely an
+ * appropriate alternative to {@code compareAndSet}.
+ *
+ * @param obj An object whose field to conditionally set
+ * @param expect the expected value
+ * @param update the new value
+ * @return true if successful
+ * @throws ClassCastException if {@code obj} is not an instance
+ * of the class possessing the field established in the constructor
+ */
+ public abstract boolean weakCompareAndSet(T obj, int expect, int update);
+
+ /**
+ * Sets the field of the given object managed by this updater to the
+ * given updated value. This operation is guaranteed to act as a volatile
+ * store with respect to subsequent invocations of {@code compareAndSet}.
+ *
+ * @param obj An object whose field to set
+ * @param newValue the new value
+ */
+ public abstract void set(T obj, int newValue);
+
+ /**
+ * Eventually sets the field of the given object managed by this
+ * updater to the given updated value.
+ *
+ * @param obj An object whose field to set
+ * @param newValue the new value
+ * @since 1.6
+ */
+ public abstract void lazySet(T obj, int newValue);
+
+
+ /**
+ * Gets the current value held in the field of the given object managed
+ * by this updater.
+ *
+ * @param obj An object whose field to get
+ * @return the current value
+ */
+ public abstract int get(T obj);
+
+ /**
+ * Atomically sets the field of the given object managed by this updater
+ * to the given value and returns the old value.
+ *
+ * @param obj An object whose field to get and set
+ * @param newValue the new value
+ * @return the previous value
+ */
+ public int getAndSet(T obj, int newValue) {
+ for (;;) {
+ int current = get(obj);
+ if (compareAndSet(obj, current, newValue))
+ return current;
+ }
+ }
+
+ /**
+ * Atomically increments by one the current value of the field of the
+ * given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @return the previous value
+ */
+ public int getAndIncrement(T obj) {
+ for (;;) {
+ int current = get(obj);
+ int next = current + 1;
+ if (compareAndSet(obj, current, next))
+ return current;
+ }
+ }
+
+ /**
+ * Atomically decrements by one the current value of the field of the
+ * given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @return the previous value
+ */
+ public int getAndDecrement(T obj) {
+ for (;;) {
+ int current = get(obj);
+ int next = current - 1;
+ if (compareAndSet(obj, current, next))
+ return current;
+ }
+ }
+
+ /**
+ * Atomically adds the given value to the current value of the field of
+ * the given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @param delta the value to add
+ * @return the previous value
+ */
+ public int getAndAdd(T obj, int delta) {
+ for (;;) {
+ int current = get(obj);
+ int next = current + delta;
+ if (compareAndSet(obj, current, next))
+ return current;
+ }
+ }
+
+ /**
+ * Atomically increments by one the current value of the field of the
+ * given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @return the updated value
+ */
+ public int incrementAndGet(T obj) {
+ for (;;) {
+ int current = get(obj);
+ int next = current + 1;
+ if (compareAndSet(obj, current, next))
+ return next;
+ }
+ }
+
+ /**
+ * Atomically decrements by one the current value of the field of the
+ * given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @return the updated value
+ */
+ public int decrementAndGet(T obj) {
+ for (;;) {
+ int current = get(obj);
+ int next = current - 1;
+ if (compareAndSet(obj, current, next))
+ return next;
+ }
+ }
+
+ /**
+ * Atomically adds the given value to the current value of the field of
+ * the given object managed by this updater.
+ *
+ * @param obj An object whose field to get and set
+ * @param delta the value to add
+ * @return the updated value
+ */
+ public int addAndGet(T obj, int delta) {
+ for (;;) {
+ int current = get(obj);
+ int next = current + delta;
+ if (compareAndSet(obj, current, next))
+ return next;
+ }
+ }
+
+ /**
+ * Standard hotspot implementation using intrinsics
+ */
+ private static class AtomicIntegerFieldUpdaterImpl<T> extends AtomicIntegerFieldUpdater<T> {
+ private static final Unsafe unsafe = Unsafe.getUnsafe();
+ private final long offset;
+ private final Class<T> tclass;
+ private final Class cclass;
+
+ AtomicIntegerFieldUpdaterImpl(Class<T> tclass, String fieldName) {
+ Field field = null;
+ Class caller = null;
+ int modifiers = 0;
+ try {
+ field = tclass.getDeclaredField(fieldName);
+ caller = sun.reflect.Reflection.getCallerClass(3);
+ modifiers = field.getModifiers();
+ sun.reflect.misc.ReflectUtil.ensureMemberAccess(
+ caller, tclass, null, modifiers);
+ sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
+ } catch(Exception ex) {
+ throw new RuntimeException(ex);
+ }
+
+ Class fieldt = field.getType();
+ if (fieldt != int.class)
+ throw new IllegalArgumentException("Must be integer type");
+
+ if (!Modifier.isVolatile(modifiers))
+ throw new IllegalArgumentException("Must be volatile type");
+
+ this.cclass = (Modifier.isProtected(modifiers) &&
+ caller != tclass) ? caller : null;
+ this.tclass = tclass;
+ offset = unsafe.objectFieldOffset(field);
+ }
+
+ private void fullCheck(T obj) {
+ if (!tclass.isInstance(obj))
+ throw new ClassCastException();
+ if (cclass != null)
+ ensureProtectedAccess(obj);
+ }
+
+ public boolean compareAndSet(T obj, int expect, int update) {
+ if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+ return unsafe.compareAndSwapInt(obj, offset, expect, update);
+ }
+
+ public boolean weakCompareAndSet(T obj, int expect, int update) {
+ if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+ return unsafe.compareAndSwapInt(obj, offset, expect, update);
+ }
+
+ public void set(T obj, int newValue) {
+ if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+ unsafe.putIntVolatile(obj, offset, newValue);
+ }
+
+ public void lazySet(T obj, int newValue) {
+ if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+ unsafe.putOrderedInt(obj, offset, newValue);
+ }
+
+ public final int get(T obj) {
+ if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj);
+ return unsafe.getIntVolatile(obj, offset);
+ }
+
+ private void ensureProtectedAccess(T obj) {
+ if (cclass.isInstance(obj)) {
+ return;
+ }
+ throw new RuntimeException(
+ new IllegalAccessException("Class " +
+ cclass.getName() +
+ " can not access a protected member of class " +
+ tclass.getName() +
+ " using an instance of " +
+ obj.getClass().getName()
+ )
+ );
+ }
+ }
+}