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660 lines
23 KiB
660 lines
23 KiB
/*
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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/*
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*
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*
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*
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*
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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.Objects;
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import java.util.function.LongBinaryOperator;
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import java.util.function.LongUnaryOperator;
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import sun.reflect.CallerSensitive;
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import sun.reflect.Reflection;
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/**
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* A reflection-based utility that enables atomic updates to
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* designated {@code volatile long} 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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* @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 AtomicLongFieldUpdater<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 long 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> AtomicLongFieldUpdater<U> newUpdater(Class<U> tclass,
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String fieldName) {
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Class<?> caller = Reflection.getCallerClass();
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if (AtomicLong.VM_SUPPORTS_LONG_CAS)
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return new CASUpdater<U>(tclass, fieldName, caller);
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else
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return new LockedUpdater<U>(tclass, fieldName, caller);
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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 AtomicLongFieldUpdater() {
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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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* @throws ClassCastException if {@code obj} is not an instance
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* of the class possessing the field established in the constructor
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*/
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public abstract boolean compareAndSet(T obj, long expect, long 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><a href="package-summary.html#weakCompareAndSet">May fail
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* spuriously and does not provide ordering guarantees</a>, so is
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* only rarely an appropriate 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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* @throws ClassCastException if {@code obj} is not an instance
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* of the class possessing the field established in the constructor
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*/
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public abstract boolean weakCompareAndSet(T obj, long expect, long 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, long 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, long newValue);
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/**
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* Gets the current value held in the field of the given object managed
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* 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 long 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 long getAndSet(T obj, long newValue) {
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long 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 long getAndIncrement(T obj) {
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long 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 long getAndDecrement(T obj) {
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long 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 long getAndAdd(T obj, long delta) {
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long 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 long incrementAndGet(T obj) {
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long 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 long decrementAndGet(T obj) {
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long 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 long addAndGet(T obj, long delta) {
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long 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 the field of the given object managed by this updater
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* with the results of applying the given function, returning the previous
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* value. 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 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 long getAndUpdate(T obj, LongUnaryOperator updateFunction) {
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long prev, next;
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do {
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prev = get(obj);
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next = updateFunction.applyAsLong(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 the field of the given object managed by this updater
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* with the results of applying the given function, returning the updated
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* value. 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 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 long updateAndGet(T obj, LongUnaryOperator updateFunction) {
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long prev, next;
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do {
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prev = get(obj);
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next = updateFunction.applyAsLong(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 the field of the given object managed by this
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* updater with the results of applying the given function to the
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* current and given values, returning the previous value. The
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* function should be side-effect-free, since it may be re-applied
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* when attempted updates fail due to contention among threads. The
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* function is applied with the current value as its first argument,
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* 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 long getAndAccumulate(T obj, long x,
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LongBinaryOperator accumulatorFunction) {
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long prev, next;
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do {
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prev = get(obj);
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next = accumulatorFunction.applyAsLong(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 the field of the given object managed by this
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* updater with the results of applying the given function to the
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* current and given values, returning the updated value. The
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* function should be side-effect-free, since it may be re-applied
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* when attempted updates fail due to contention among threads. The
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* function is applied with the current value as its first argument,
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* 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 long accumulateAndGet(T obj, long x,
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LongBinaryOperator accumulatorFunction) {
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long prev, next;
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do {
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prev = get(obj);
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next = accumulatorFunction.applyAsLong(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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private static final class CASUpdater<T> extends AtomicLongFieldUpdater<T> {
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private static final sun.misc.Unsafe U = sun.misc.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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CASUpdater(final Class<T> tclass, 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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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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modifiers = field.getModifiers();
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sun.reflect.misc.ReflectUtil.ensureMemberAccess(
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caller, tclass, null, modifiers);
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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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} catch (PrivilegedActionException pae) {
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throw new RuntimeException(pae.getException());
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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() != long.class)
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throw new IllegalArgumentException("Must be long 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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/**
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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, long expect, long update) {
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accessCheck(obj);
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return U.compareAndSwapLong(obj, offset, expect, update);
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}
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public final boolean weakCompareAndSet(T obj, long expect, long update) {
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accessCheck(obj);
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return U.compareAndSwapLong(obj, offset, expect, update);
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}
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public final void set(T obj, long newValue) {
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accessCheck(obj);
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U.putLongVolatile(obj, offset, newValue);
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}
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public final void lazySet(T obj, long newValue) {
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accessCheck(obj);
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U.putOrderedLong(obj, offset, newValue);
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}
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public final long get(T obj) {
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accessCheck(obj);
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return U.getLongVolatile(obj, offset);
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}
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public final long getAndSet(T obj, long newValue) {
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accessCheck(obj);
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return U.getAndSetLong(obj, offset, newValue);
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}
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public final long getAndAdd(T obj, long delta) {
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accessCheck(obj);
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return U.getAndAddLong(obj, offset, delta);
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}
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public final long getAndIncrement(T obj) {
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return getAndAdd(obj, 1);
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}
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public final long getAndDecrement(T obj) {
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return getAndAdd(obj, -1);
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}
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public final long incrementAndGet(T obj) {
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return getAndAdd(obj, 1) + 1;
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}
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public final long decrementAndGet(T obj) {
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return getAndAdd(obj, -1) - 1;
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}
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public final long addAndGet(T obj, long delta) {
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return getAndAdd(obj, delta) + delta;
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}
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}
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private static final class LockedUpdater<T> extends AtomicLongFieldUpdater<T> {
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private static final sun.misc.Unsafe U = sun.misc.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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LockedUpdater(final Class<T> tclass, final String fieldName,
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final Class<?> caller) {
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Field field = null;
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int modifiers = 0;
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try {
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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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modifiers = field.getModifiers();
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sun.reflect.misc.ReflectUtil.ensureMemberAccess(
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caller, tclass, null, modifiers);
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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);
|
|
}
|
|
} catch (PrivilegedActionException pae) {
|
|
throw new RuntimeException(pae.getException());
|
|
} catch (Exception ex) {
|
|
throw new RuntimeException(ex);
|
|
}
|
|
|
|
if (field.getType() != long.class)
|
|
throw new IllegalArgumentException("Must be long type");
|
|
|
|
if (!Modifier.isVolatile(modifiers))
|
|
throw new IllegalArgumentException("Must be volatile type");
|
|
|
|
// Access to protected field members is restricted to receivers only
|
|
// of the accessing class, or one of its subclasses, and the
|
|
// accessing class must in turn be a subclass (or package sibling)
|
|
// of the protected member's defining class.
|
|
// If the updater refers to a protected field of a declaring class
|
|
// outside the current package, the receiver argument will be
|
|
// narrowed to the type of the accessing class.
|
|
this.cclass = (Modifier.isProtected(modifiers) &&
|
|
tclass.isAssignableFrom(caller) &&
|
|
!isSamePackage(tclass, caller))
|
|
? caller : tclass;
|
|
this.tclass = tclass;
|
|
this.offset = U.objectFieldOffset(field);
|
|
}
|
|
|
|
/**
|
|
* Checks that target argument is instance of cclass. On
|
|
* failure, throws cause.
|
|
*/
|
|
private final void accessCheck(T obj) {
|
|
if (!cclass.isInstance(obj))
|
|
throw accessCheckException(obj);
|
|
}
|
|
|
|
/**
|
|
* Returns access exception if accessCheck failed due to
|
|
* protected access, else ClassCastException.
|
|
*/
|
|
private final RuntimeException accessCheckException(T obj) {
|
|
if (cclass == tclass)
|
|
return new ClassCastException();
|
|
else
|
|
return 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, long expect, long update) {
|
|
accessCheck(obj);
|
|
synchronized (this) {
|
|
long v = U.getLong(obj, offset);
|
|
if (v != expect)
|
|
return false;
|
|
U.putLong(obj, offset, update);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
public final boolean weakCompareAndSet(T obj, long expect, long update) {
|
|
return compareAndSet(obj, expect, update);
|
|
}
|
|
|
|
public final void set(T obj, long newValue) {
|
|
accessCheck(obj);
|
|
synchronized (this) {
|
|
U.putLong(obj, offset, newValue);
|
|
}
|
|
}
|
|
|
|
public final void lazySet(T obj, long newValue) {
|
|
set(obj, newValue);
|
|
}
|
|
|
|
public final long get(T obj) {
|
|
accessCheck(obj);
|
|
synchronized (this) {
|
|
return U.getLong(obj, offset);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Returns true if the second classloader can be found in the first
|
|
* classloader's delegation chain.
|
|
* Equivalent to the inaccessible: first.isAncestor(second).
|
|
*/
|
|
static boolean isAncestor(ClassLoader first, ClassLoader second) {
|
|
ClassLoader acl = first;
|
|
do {
|
|
acl = acl.getParent();
|
|
if (second == acl) {
|
|
return true;
|
|
}
|
|
} while (acl != null);
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* Returns true if the two classes have the same class loader and
|
|
* package qualifier
|
|
*/
|
|
private static boolean isSamePackage(Class<?> class1, Class<?> class2) {
|
|
return class1.getClassLoader() == class2.getClassLoader()
|
|
&& Objects.equals(getPackageName(class1), getPackageName(class2));
|
|
}
|
|
|
|
private static String getPackageName(Class<?> cls) {
|
|
String cn = cls.getName();
|
|
int dot = cn.lastIndexOf('.');
|
|
return (dot != -1) ? cn.substring(0, dot) : "";
|
|
}
|
|
}
|