563 lines
21 KiB
Java
563 lines
21 KiB
Java
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/publicdomain/zero/1.0/
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*/
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package java.util.concurrent.atomic;
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import java.lang.reflect.Field;
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import java.lang.reflect.Modifier;
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import java.security.AccessController;
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import java.security.PrivilegedActionException;
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import java.security.PrivilegedExceptionAction;
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import java.util.function.IntBinaryOperator;
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import java.util.function.IntUnaryOperator;
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import jdk.internal.misc.Unsafe;
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import jdk.internal.reflect.CallerSensitive;
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import jdk.internal.reflect.Reflection;
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import java.lang.invoke.VarHandle;
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/**
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* A reflection-based utility that enables atomic updates to
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* designated {@code volatile int} fields of designated classes.
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* This class is designed for use in atomic data structures in which
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* several fields of the same node are independently subject to atomic
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* updates.
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*
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* <p>Note that the guarantees of the {@code compareAndSet}
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* method in this class are weaker than in other atomic classes.
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* Because this class cannot ensure that all uses of the field
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* are appropriate for purposes of atomic access, it can
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* guarantee atomicity only with respect to other invocations of
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* {@code compareAndSet} and {@code set} on the same updater.
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*
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* <p>Object arguments for parameters of type {@code T} that are not
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* instances of the class passed to {@link #newUpdater} will result in
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* a {@link ClassCastException} being thrown.
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*
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* @since 1.5
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* @author Doug Lea
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* @param <T> The type of the object holding the updatable field
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*/
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public abstract class AtomicIntegerFieldUpdater<T> {
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/**
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* Creates and returns an updater for objects with the given field.
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* The Class argument is needed to check that reflective types and
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* generic types match.
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*
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* @param tclass the class of the objects holding the field
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* @param fieldName the name of the field to be updated
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* @param <U> the type of instances of tclass
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* @return the updater
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* @throws IllegalArgumentException if the field is not a
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* volatile integer type
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* @throws RuntimeException with a nested reflection-based
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* exception if the class does not hold field or is the wrong type,
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* or the field is inaccessible to the caller according to Java language
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* access control
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*/
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@CallerSensitive
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public static <U> AtomicIntegerFieldUpdater<U> newUpdater(Class<U> tclass,
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String fieldName) {
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return new AtomicIntegerFieldUpdaterImpl<U>
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(tclass, fieldName, Reflection.getCallerClass());
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}
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/**
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* Protected do-nothing constructor for use by subclasses.
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*/
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protected AtomicIntegerFieldUpdater() {
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}
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/**
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* Atomically sets the field of the given object managed by this updater
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* to the given updated value if the current value {@code ==} the
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* expected value. This method is guaranteed to be atomic with respect to
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* other calls to {@code compareAndSet} and {@code set}, but not
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* necessarily with respect to other changes in the field.
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*
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* @param obj An object whose field to conditionally set
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* @param expect the expected value
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* @param update the new value
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* @return {@code true} if successful
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*/
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public abstract boolean compareAndSet(T obj, int expect, int update);
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/**
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* Atomically sets the field of the given object managed by this updater
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* to the given updated value if the current value {@code ==} the
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* expected value. This method is guaranteed to be atomic with respect to
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* other calls to {@code compareAndSet} and {@code set}, but not
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* necessarily with respect to other changes in the field.
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*
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* <p>This operation may fail spuriously and does not provide
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* ordering guarantees, so is only rarely an appropriate
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* alternative to {@code compareAndSet}.
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*
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* @param obj An object whose field to conditionally set
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* @param expect the expected value
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* @param update the new value
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* @return {@code true} if successful
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*/
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public abstract boolean weakCompareAndSet(T obj, int expect, int update);
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/**
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* Sets the field of the given object managed by this updater to the
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* given updated value. This operation is guaranteed to act as a volatile
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* store with respect to subsequent invocations of {@code compareAndSet}.
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*
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* @param obj An object whose field to set
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* @param newValue the new value
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*/
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public abstract void set(T obj, int newValue);
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/**
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* Eventually sets the field of the given object managed by this
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* updater to the given updated value.
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*
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* @param obj An object whose field to set
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* @param newValue the new value
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* @since 1.6
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*/
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public abstract void lazySet(T obj, int newValue);
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/**
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* Returns the current value held in the field of the given object
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* managed by this updater.
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*
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* @param obj An object whose field to get
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* @return the current value
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*/
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public abstract int get(T obj);
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/**
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* Atomically sets the field of the given object managed by this updater
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* to the given value and returns the old value.
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*
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* @param obj An object whose field to get and set
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* @param newValue the new value
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* @return the previous value
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*/
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public int getAndSet(T obj, int newValue) {
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int prev;
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do {
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prev = get(obj);
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} while (!compareAndSet(obj, prev, newValue));
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return prev;
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}
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/**
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* Atomically increments by one the current value of the field of the
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* given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @return the previous value
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*/
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public int getAndIncrement(T obj) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev + 1;
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} while (!compareAndSet(obj, prev, next));
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return prev;
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}
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/**
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* Atomically decrements by one the current value of the field of the
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* given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @return the previous value
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*/
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public int getAndDecrement(T obj) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev - 1;
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} while (!compareAndSet(obj, prev, next));
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return prev;
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}
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/**
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* Atomically adds the given value to the current value of the field of
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* the given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @param delta the value to add
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* @return the previous value
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*/
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public int getAndAdd(T obj, int delta) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev + delta;
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} while (!compareAndSet(obj, prev, next));
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return prev;
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}
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/**
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* Atomically increments by one the current value of the field of the
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* given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @return the updated value
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*/
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public int incrementAndGet(T obj) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev + 1;
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} while (!compareAndSet(obj, prev, next));
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return next;
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}
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/**
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* Atomically decrements by one the current value of the field of the
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* given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @return the updated value
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*/
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public int decrementAndGet(T obj) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev - 1;
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} while (!compareAndSet(obj, prev, next));
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return next;
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}
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/**
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* Atomically adds the given value to the current value of the field of
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* the given object managed by this updater.
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*
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* @param obj An object whose field to get and set
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* @param delta the value to add
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* @return the updated value
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*/
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public int addAndGet(T obj, int delta) {
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int prev, next;
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do {
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prev = get(obj);
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next = prev + delta;
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} while (!compareAndSet(obj, prev, next));
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return next;
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}
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/**
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* Atomically updates (with memory effects as specified by {@link
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* VarHandle#compareAndSet}) the field of the given object managed
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* by this updater with the results of applying the given
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* function, returning the previous value. The function should be
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* side-effect-free, since it may be re-applied when attempted
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* updates fail due to contention among threads.
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*
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* @param obj An object whose field to get and set
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* @param updateFunction a side-effect-free function
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* @return the previous value
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* @since 1.8
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*/
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public final int getAndUpdate(T obj, IntUnaryOperator updateFunction) {
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int prev, next;
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do {
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prev = get(obj);
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next = updateFunction.applyAsInt(prev);
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} while (!compareAndSet(obj, prev, next));
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return prev;
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}
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/**
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* Atomically updates (with memory effects as specified by {@link
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* VarHandle#compareAndSet}) the field of the given object managed
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* by this updater with the results of applying the given
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* function, returning the updated value. The function should be
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* side-effect-free, since it may be re-applied when attempted
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* updates fail due to contention among threads.
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*
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* @param obj An object whose field to get and set
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* @param updateFunction a side-effect-free function
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* @return the updated value
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* @since 1.8
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*/
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public final int updateAndGet(T obj, IntUnaryOperator updateFunction) {
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int prev, next;
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do {
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prev = get(obj);
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next = updateFunction.applyAsInt(prev);
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} while (!compareAndSet(obj, prev, next));
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return next;
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}
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/**
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* Atomically updates (with memory effects as specified by {@link
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* VarHandle#compareAndSet}) the field of the given object managed
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* by this updater with the results of applying the given function
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* to the current and given values, returning the previous value.
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* The function should be side-effect-free, since it may be
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* re-applied when attempted updates fail due to contention among
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* threads. The function is applied with the current value as its
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* first argument, and the given update as the second argument.
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*
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* @param obj An object whose field to get and set
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* @param x the update value
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* @param accumulatorFunction a side-effect-free function of two arguments
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* @return the previous value
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* @since 1.8
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*/
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public final int getAndAccumulate(T obj, int x,
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IntBinaryOperator accumulatorFunction) {
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int prev, next;
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do {
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prev = get(obj);
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next = accumulatorFunction.applyAsInt(prev, x);
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} while (!compareAndSet(obj, prev, next));
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return prev;
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}
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/**
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* Atomically updates (with memory effects as specified by {@link
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* VarHandle#compareAndSet}) the field of the given object managed
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* by this updater with the results of applying the given function
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* to the current and given values, returning the updated value.
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* The function should be side-effect-free, since it may be
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* re-applied when attempted updates fail due to contention among
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* threads. The function is applied with the current value as its
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* first argument, and the given update as the second argument.
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*
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* @param obj An object whose field to get and set
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* @param x the update value
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* @param accumulatorFunction a side-effect-free function of two arguments
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* @return the updated value
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* @since 1.8
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*/
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public final int accumulateAndGet(T obj, int x,
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IntBinaryOperator accumulatorFunction) {
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int prev, next;
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do {
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prev = get(obj);
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next = accumulatorFunction.applyAsInt(prev, x);
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} while (!compareAndSet(obj, prev, next));
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return next;
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}
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/**
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* Standard hotspot implementation using intrinsics.
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*/
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private static final class AtomicIntegerFieldUpdaterImpl<T>
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extends AtomicIntegerFieldUpdater<T> {
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private static final Unsafe U = Unsafe.getUnsafe();
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private final long offset;
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/**
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* if field is protected, the subclass constructing updater, else
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* the same as tclass
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*/
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private final Class<?> cclass;
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/** class holding the field */
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private final Class<T> tclass;
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@SuppressWarnings("removal")
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AtomicIntegerFieldUpdaterImpl(final Class<T> tclass,
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final String fieldName,
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final Class<?> caller) {
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final Field field;
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final int modifiers;
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try {
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// BEGIN Android-changed: Skip privilege escalation which is a noop on Android.
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/*
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field = AccessController.doPrivileged(
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new PrivilegedExceptionAction<Field>() {
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public Field run() throws NoSuchFieldException {
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return tclass.getDeclaredField(fieldName);
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}
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});
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*/
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field = tclass.getDeclaredField(fieldName);
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// END Android-changed: Skip privilege escalation which is a noop on Android.
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modifiers = field.getModifiers();
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sun.reflect.misc.ReflectUtil.ensureMemberAccess(
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caller, tclass, null, modifiers);
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// BEGIN Android-removed: Skip checkPackageAccess which is a noop on Android.
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/*
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ClassLoader cl = tclass.getClassLoader();
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ClassLoader ccl = caller.getClassLoader();
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if ((ccl != null) && (ccl != cl) &&
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((cl == null) || !isAncestor(cl, ccl))) {
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sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass);
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}
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*/
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// END Android-removed: Skip checkPackageAccess which is a noop on Android.
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// BEGIN Android-removed: Skip privilege escalation which is a noop on Android.
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/*
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} catch (PrivilegedActionException pae) {
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throw new RuntimeException(pae.getException());
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*/
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// END Android-removed: Skip privilege escalation which is a noop on Android.
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} catch (Exception ex) {
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throw new RuntimeException(ex);
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}
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if (field.getType() != int.class)
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throw new IllegalArgumentException("Must be integer type");
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if (!Modifier.isVolatile(modifiers))
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throw new IllegalArgumentException("Must be volatile type");
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// Access to protected field members is restricted to receivers only
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// of the accessing class, or one of its subclasses, and the
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// accessing class must in turn be a subclass (or package sibling)
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// of the protected member's defining class.
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// If the updater refers to a protected field of a declaring class
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// outside the current package, the receiver argument will be
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// narrowed to the type of the accessing class.
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this.cclass = (Modifier.isProtected(modifiers) &&
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tclass.isAssignableFrom(caller) &&
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!isSamePackage(tclass, caller))
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? caller : tclass;
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this.tclass = tclass;
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this.offset = U.objectFieldOffset(field);
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}
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// BEGIN Android-removed: isAncestor()'s only usage was removed above.
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/*
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/**
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* Returns true if the second classloader can be found in the first
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* classloader's delegation chain.
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* Equivalent to the inaccessible: first.isAncestor(second).
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*
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private static boolean isAncestor(ClassLoader first, ClassLoader second) {
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ClassLoader acl = first;
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do {
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acl = acl.getParent();
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if (second == acl) {
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return true;
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}
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} while (acl != null);
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return false;
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}
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*/
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// END Android-removed: isAncestor()'s only usage was removed above.
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/**
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* Returns true if the two classes have the same class loader and
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* package qualifier
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*/
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private static boolean isSamePackage(Class<?> class1, Class<?> class2) {
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return class1.getClassLoader() == class2.getClassLoader()
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&& class1.getPackageName() == class2.getPackageName();
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}
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/**
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* Checks that target argument is instance of cclass. On
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* failure, throws cause.
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*/
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private final void accessCheck(T obj) {
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if (!cclass.isInstance(obj))
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throwAccessCheckException(obj);
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}
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/**
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* Throws access exception if accessCheck failed due to
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* protected access, else ClassCastException.
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*/
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private final void throwAccessCheckException(T obj) {
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if (cclass == tclass)
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throw new ClassCastException();
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else
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throw new RuntimeException(
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new IllegalAccessException(
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"Class " +
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cclass.getName() +
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" can not access a protected member of class " +
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tclass.getName() +
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" using an instance of " +
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obj.getClass().getName()));
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}
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public final boolean compareAndSet(T obj, int expect, int update) {
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accessCheck(obj);
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return U.compareAndSetInt(obj, offset, expect, update);
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}
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public final boolean weakCompareAndSet(T obj, int expect, int update) {
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accessCheck(obj);
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return U.compareAndSetInt(obj, offset, expect, update);
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}
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public final void set(T obj, int newValue) {
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accessCheck(obj);
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U.putIntVolatile(obj, offset, newValue);
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}
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public final void lazySet(T obj, int newValue) {
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accessCheck(obj);
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U.putIntRelease(obj, offset, newValue);
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}
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|
|
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;
|
|
}
|
|
|
|
}
|
|
}
|