| /* |
| * 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.BinaryOperator; |
| import java.util.function.UnaryOperator; |
| import sun.reflect.CallerSensitive; |
| import sun.reflect.Reflection; |
| |
| /** |
| * A reflection-based utility that enables atomic updates to |
| * designated {@code volatile} reference fields of designated |
| * classes. This class is designed for use in atomic data structures |
| * in which several reference fields of the same node are |
| * independently subject to atomic updates. For example, a tree node |
| * might be declared as |
| * |
| * <pre> {@code |
| * class Node { |
| * private volatile Node left, right; |
| * |
| * private static final AtomicReferenceFieldUpdater<Node, Node> leftUpdater = |
| * AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left"); |
| * private static AtomicReferenceFieldUpdater<Node, Node> rightUpdater = |
| * AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right"); |
| * |
| * Node getLeft() { return left; } |
| * boolean compareAndSetLeft(Node expect, Node update) { |
| * return leftUpdater.compareAndSet(this, expect, update); |
| * } |
| * // ... and so on |
| * }}</pre> |
| * |
| * <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 |
| * @param <V> The type of the field |
| */ |
| public abstract class AtomicReferenceFieldUpdater<T,V> { |
| |
| /** |
| * Creates and returns an updater for objects with the given field. |
| * The Class arguments are needed to check that reflective types and |
| * generic types match. |
| * |
| * @param tclass the class of the objects holding the field |
| * @param vclass the class of the field |
| * @param fieldName the name of the field to be updated |
| * @param <U> the type of instances of tclass |
| * @param <W> the type of instances of vclass |
| * @return the updater |
| * @throws ClassCastException if the field is of the wrong type |
| * @throws IllegalArgumentException if the field is not volatile |
| * @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 <U,W> AtomicReferenceFieldUpdater<U,W> newUpdater(Class<U> tclass, |
| Class<W> vclass, |
| String fieldName) { |
| return new AtomicReferenceFieldUpdaterImpl<U,W> |
| (tclass, vclass, fieldName, VMStack.getStackClass1()); // android-changed |
| } |
| |
| /** |
| * Protected do-nothing constructor for use by subclasses. |
| */ |
| protected AtomicReferenceFieldUpdater() { |
| } |
| |
| /** |
| * 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 |
| */ |
| public abstract boolean compareAndSet(T obj, V expect, V 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><a href="package-summary.html#weakCompareAndSet">May fail |
| * spuriously and does not provide ordering guarantees</a>, 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 |
| */ |
| public abstract boolean weakCompareAndSet(T obj, V expect, V 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, V 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, V 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 V 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 V getAndSet(T obj, V newValue) { |
| V prev; |
| do { |
| prev = get(obj); |
| } while (!compareAndSet(obj, prev, newValue)); |
| return prev; |
| } |
| |
| /** |
| * 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 V getAndUpdate(T obj, UnaryOperator<V> updateFunction) { |
| V prev, next; |
| do { |
| prev = get(obj); |
| next = updateFunction.apply(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 V updateAndGet(T obj, UnaryOperator<V> updateFunction) { |
| V prev, next; |
| do { |
| prev = get(obj); |
| next = updateFunction.apply(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 V getAndAccumulate(T obj, V x, |
| BinaryOperator<V> accumulatorFunction) { |
| V prev, next; |
| do { |
| prev = get(obj); |
| next = accumulatorFunction.apply(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 V accumulateAndGet(T obj, V x, |
| BinaryOperator<V> accumulatorFunction) { |
| V prev, next; |
| do { |
| prev = get(obj); |
| next = accumulatorFunction.apply(prev, x); |
| } while (!compareAndSet(obj, prev, next)); |
| return next; |
| } |
| |
| private static final class AtomicReferenceFieldUpdaterImpl<T,V> |
| extends AtomicReferenceFieldUpdater<T,V> { |
| 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<T> tclass; |
| /** field value type */ |
| private final Class<V> vclass; |
| |
| /* |
| * Internal type checks within all update methods contain |
| * internal inlined optimizations checking for the common |
| * cases where the class is final (in which case a simple |
| * getClass comparison suffices) or is of type Object (in |
| * which case no check is needed because all objects are |
| * instances of Object). The Object case is handled simply by |
| * setting vclass to null in constructor. The targetCheck and |
| * updateCheck methods are invoked when these faster |
| * screenings fail. |
| */ |
| |
| AtomicReferenceFieldUpdaterImpl(final Class<T> tclass, |
| final Class<V> vclass, |
| final String fieldName, |
| final Class<?> caller) { |
| final Field field; |
| final Class<?> fieldClass; |
| final int modifiers; |
| try { |
| field = tclass.getDeclaredField(fieldName); // android-changed |
| 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 |
| fieldClass = field.getType(); |
| // BEGIN android-removed |
| // } catch (PrivilegedActionException pae) { |
| // throw new RuntimeException(pae.getException()); |
| // END android-removed |
| } catch (Exception ex) { |
| throw new RuntimeException(ex); |
| } |
| |
| if (vclass != fieldClass) |
| throw new ClassCastException(); |
| if (vclass.isPrimitive()) |
| throw new IllegalArgumentException("Must be reference type"); |
| |
| if (!Modifier.isVolatile(modifiers)) |
| throw new IllegalArgumentException("Must be volatile type"); |
| |
| this.cclass = (Modifier.isProtected(modifiers)) ? caller : tclass; |
| this.tclass = tclass; |
| this.vclass = vclass; |
| 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())); |
| } |
| |
| private final void valueCheck(V v) { |
| if (v != null && !(vclass.isInstance(v))) |
| throwCCE(); |
| } |
| |
| static void throwCCE() { |
| throw new ClassCastException(); |
| } |
| |
| public final boolean compareAndSet(T obj, V expect, V update) { |
| accessCheck(obj); |
| valueCheck(update); |
| return U.compareAndSwapObject(obj, offset, expect, update); |
| } |
| |
| public final boolean weakCompareAndSet(T obj, V expect, V update) { |
| // same implementation as strong form for now |
| accessCheck(obj); |
| valueCheck(update); |
| return U.compareAndSwapObject(obj, offset, expect, update); |
| } |
| |
| public final void set(T obj, V newValue) { |
| accessCheck(obj); |
| valueCheck(newValue); |
| U.putObjectVolatile(obj, offset, newValue); |
| } |
| |
| public final void lazySet(T obj, V newValue) { |
| accessCheck(obj); |
| valueCheck(newValue); |
| U.putOrderedObject(obj, offset, newValue); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public final V get(T obj) { |
| accessCheck(obj); |
| return (V)U.getObjectVolatile(obj, offset); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public final V getAndSet(T obj, V newValue) { |
| accessCheck(obj); |
| valueCheck(newValue); |
| return (V)U.getAndSetObject(obj, offset, newValue); |
| } |
| } |
| } |