/* * 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. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.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/publicdomain/zero/1.0/ */ package java.util.concurrent.atomic; import dalvik.system.VMStack; // Android-added import java.lang.reflect.Field; import java.lang.reflect.Modifier; import java.security.AccessController; import java.security.PrivilegedActionException; import java.security.PrivilegedExceptionAction; import java.util.function.IntBinaryOperator; import java.util.function.IntUnaryOperator; import sun.reflect.CallerSensitive; import sun.reflect.Reflection; /** * 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. * *

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 The type of the object holding the updatable field */ public abstract class AtomicIntegerFieldUpdater { /** * 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 * @param the type of instances of tclass * @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, * or the field is inaccessible to the caller according to Java language * access control */ @CallerSensitive public static AtomicIntegerFieldUpdater newUpdater(Class tclass, String fieldName) { return new AtomicIntegerFieldUpdaterImpl (tclass, fieldName, VMStack.getStackClass1()); // Android-changed } /** * 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 {@code 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. * *

May fail * spuriously 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 {@code 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) { int prev; do { prev = get(obj); } while (!compareAndSet(obj, prev, newValue)); return prev; } /** * 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) { int prev, next; do { prev = get(obj); next = prev + 1; } while (!compareAndSet(obj, prev, next)); return prev; } /** * 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) { int prev, next; do { prev = get(obj); next = prev - 1; } while (!compareAndSet(obj, prev, next)); return prev; } /** * 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) { int prev, next; do { prev = get(obj); next = prev + delta; } while (!compareAndSet(obj, prev, next)); return prev; } /** * 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) { int prev, next; do { prev = get(obj); next = prev + 1; } while (!compareAndSet(obj, prev, 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) { int prev, next; do { prev = get(obj); next = prev - 1; } while (!compareAndSet(obj, prev, 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) { int prev, next; do { prev = get(obj); next = prev + delta; } while (!compareAndSet(obj, prev, next)); return next; } /** * Atomically updates the field of the given object managed by this updater * with the results of applying the given function, returning the previous * value. The function should be side-effect-free, since it may be * re-applied when attempted updates fail due to contention among threads. * * @param obj An object whose field to get and set * @param updateFunction a side-effect-free function * @return the previous value * @since 1.8 */ public final int getAndUpdate(T obj, IntUnaryOperator updateFunction) { int prev, next; do { prev = get(obj); next = updateFunction.applyAsInt(prev); } while (!compareAndSet(obj, prev, next)); return prev; } /** * Atomically updates the field of the given object managed by this updater * with the results of applying the given function, returning the updated * value. The function should be side-effect-free, since it may be * re-applied when attempted updates fail due to contention among threads. * * @param obj An object whose field to get and set * @param updateFunction a side-effect-free function * @return the updated value * @since 1.8 */ public final int updateAndGet(T obj, IntUnaryOperator updateFunction) { int prev, next; do { prev = get(obj); next = updateFunction.applyAsInt(prev); } while (!compareAndSet(obj, prev, next)); return next; } /** * Atomically updates the field of the given object managed by this * updater with the results of applying the given function to the * current and given values, returning the previous value. The * function should be side-effect-free, since it may be re-applied * when attempted updates fail due to contention among threads. The * function is applied with the current value as its first argument, * and the given update as the second argument. * * @param obj An object whose field to get and set * @param x the update value * @param accumulatorFunction a side-effect-free function of two arguments * @return the previous value * @since 1.8 */ public final int getAndAccumulate(T obj, int x, IntBinaryOperator accumulatorFunction) { int prev, next; do { prev = get(obj); next = accumulatorFunction.applyAsInt(prev, x); } while (!compareAndSet(obj, prev, next)); return prev; } /** * Atomically updates the field of the given object managed by this * updater with the results of applying the given function to the * current and given values, returning the updated value. The * function should be side-effect-free, since it may be re-applied * when attempted updates fail due to contention among threads. The * function is applied with the current value as its first argument, * and the given update as the second argument. * * @param obj An object whose field to get and set * @param x the update value * @param accumulatorFunction a side-effect-free function of two arguments * @return the updated value * @since 1.8 */ public final int accumulateAndGet(T obj, int x, IntBinaryOperator accumulatorFunction) { int prev, next; do { prev = get(obj); next = accumulatorFunction.applyAsInt(prev, x); } while (!compareAndSet(obj, prev, next)); return next; } /** * Standard hotspot implementation using intrinsics. */ private static final class AtomicIntegerFieldUpdaterImpl extends AtomicIntegerFieldUpdater { private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe(); private final long offset; /** * if field is protected, the subclass constructing updater, else * the same as tclass */ private final Class cclass; /** class holding the field */ private final Class tclass; AtomicIntegerFieldUpdaterImpl(final Class tclass, final String fieldName, final Class caller) { final Field field; final int modifiers; try { field = AccessController.doPrivileged( new PrivilegedExceptionAction() { public Field run() throws NoSuchFieldException { return tclass.getDeclaredField(fieldName); } }); modifiers = field.getModifiers(); // BEGIN Android-removed // sun.reflect.misc.ReflectUtil.ensureMemberAccess( // caller, tclass, null, modifiers); // ClassLoader cl = tclass.getClassLoader(); // ClassLoader ccl = caller.getClassLoader(); // if ((ccl != null) && (ccl != cl) && // ((cl == null) || !isAncestor(cl, ccl))) { // sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); // } // END Android-removed // BEGIN Android-removed // } catch (PrivilegedActionException pae) { // throw new RuntimeException(pae.getException()); // END Android-removed } catch (Exception ex) { throw new RuntimeException(ex); } if (field.getType() != 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; this.tclass = tclass; this.offset = U.objectFieldOffset(field); } // BEGIN Android-removed // /** // * Returns true if the second classloader can be found in the first // * classloader's delegation chain. // * Equivalent to the inaccessible: first.isAncestor(second). // */ // private static boolean isAncestor(ClassLoader first, ClassLoader second) { // ClassLoader acl = first; // do { // acl = acl.getParent(); // if (second == acl) { // return true; // } // } while (acl != null); // return false; // } // END Android-removed /** * Checks that target argument is instance of cclass. On * failure, throws cause. */ private final void accessCheck(T obj) { if (!cclass.isInstance(obj)) throwAccessCheckException(obj); } /** * Throws access exception if accessCheck failed due to * protected access, else ClassCastException. */ private final void throwAccessCheckException(T obj) { if (cclass == tclass) throw new ClassCastException(); else 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())); } public final boolean compareAndSet(T obj, int expect, int update) { accessCheck(obj); return U.compareAndSwapInt(obj, offset, expect, update); } public final boolean weakCompareAndSet(T obj, int expect, int update) { accessCheck(obj); return U.compareAndSwapInt(obj, offset, expect, update); } public final void set(T obj, int newValue) { accessCheck(obj); U.putIntVolatile(obj, offset, newValue); } public final void lazySet(T obj, int newValue) { accessCheck(obj); U.putOrderedInt(obj, offset, newValue); } public final int get(T obj) { accessCheck(obj); return U.getIntVolatile(obj, offset); } public final int getAndSet(T obj, int newValue) { accessCheck(obj); return U.getAndSetInt(obj, offset, newValue); } public final int getAndAdd(T obj, int delta) { accessCheck(obj); return U.getAndAddInt(obj, offset, delta); } public final int getAndIncrement(T obj) { return getAndAdd(obj, 1); } public final int getAndDecrement(T obj) { return getAndAdd(obj, -1); } public final int incrementAndGet(T obj) { return getAndAdd(obj, 1) + 1; } public final int decrementAndGet(T obj) { return getAndAdd(obj, -1) - 1; } public final int addAndGet(T obj, int delta) { return getAndAdd(obj, delta) + delta; } } }