java.util.concurrent.atomic.AtomicIntegerFieldUpdater Maven / Gradle / Ivy
Show all versions of qbicc-rt-java.base Show documentation
/*
* 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 java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.function.IntBinaryOperator;
import java.util.function.IntUnaryOperator;
import jdk.internal.misc.Unsafe;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;
import java.lang.invoke.VarHandle;
/**
* A reflection-based utility that enables atomic updates to
* designated {@code volatile int} fields of designated classes.
* This class is designed for use in atomic data structures in which
* several fields of the same node are independently subject to atomic
* updates.
*
* Note that the guarantees of the {@code compareAndSet}
* method in this class are weaker than in other atomic classes.
* Because this class cannot ensure that all uses of the field
* are appropriate for purposes of atomic access, it can
* guarantee atomicity only with respect to other invocations of
* {@code compareAndSet} and {@code set} on the same updater.
*
*
Object arguments for parameters of type {@code T} that are not
* instances of the class passed to {@link #newUpdater} will result in
* a {@link ClassCastException} being thrown.
*
* @since 1.5
* @author Doug Lea
* @param The type of the object holding the updatable field
*/
public abstract class AtomicIntegerFieldUpdater {
/**
* Creates and returns an updater for objects with the given field.
* The Class argument is needed to check that reflective types and
* generic types match.
*
* @param tclass the class of the objects holding the field
* @param fieldName the name of the field to be updated
* @param the type of instances of tclass
* @return the updater
* @throws IllegalArgumentException if the field is not a
* volatile integer type
* @throws RuntimeException with a nested reflection-based
* exception if the class does not hold field or is the wrong type,
* or the field is inaccessible to the caller according to Java language
* access control
*/
@CallerSensitive
public static AtomicIntegerFieldUpdater newUpdater(Class tclass,
String fieldName) {
return new AtomicIntegerFieldUpdaterImpl
(tclass, fieldName, Reflection.getCallerClass());
}
/**
* Protected do-nothing constructor for use by subclasses.
*/
protected AtomicIntegerFieldUpdater() {
}
/**
* Atomically sets the field of the given object managed by this updater
* to the given updated value if the current value {@code ==} the
* expected value. This method is guaranteed to be atomic with respect to
* other calls to {@code compareAndSet} and {@code set}, but not
* necessarily with respect to other changes in the field.
*
* @param obj An object whose field to conditionally set
* @param expect the expected value
* @param update the new value
* @return {@code true} if successful
*/
public abstract boolean compareAndSet(T obj, int expect, int update);
/**
* Atomically sets the field of the given object managed by this updater
* to the given updated value if the current value {@code ==} the
* expected value. This method is guaranteed to be atomic with respect to
* other calls to {@code compareAndSet} and {@code set}, but not
* necessarily with respect to other changes in the field.
*
* This operation may fail spuriously and does not provide
* ordering guarantees, so is only rarely an appropriate
* alternative to {@code compareAndSet}.
*
* @param obj An object whose field to conditionally set
* @param expect the expected value
* @param update the new value
* @return {@code true} if successful
*/
public abstract boolean weakCompareAndSet(T obj, int expect, int update);
/**
* Sets the field of the given object managed by this updater to the
* given updated value. This operation is guaranteed to act as a volatile
* store with respect to subsequent invocations of {@code compareAndSet}.
*
* @param obj An object whose field to set
* @param newValue the new value
*/
public abstract void set(T obj, int newValue);
/**
* Eventually sets the field of the given object managed by this
* updater to the given updated value.
*
* @param obj An object whose field to set
* @param newValue the new value
* @since 1.6
*/
public abstract void lazySet(T obj, int newValue);
/**
* Returns the current value held in the field of the given object
* managed by this updater.
*
* @param obj An object whose field to get
* @return the current value
*/
public abstract int get(T obj);
/**
* Atomically sets the field of the given object managed by this updater
* to the given value and returns the old value.
*
* @param obj An object whose field to get and set
* @param newValue the new value
* @return the previous value
*/
public int getAndSet(T obj, int newValue) {
int prev;
do {
prev = get(obj);
} while (!compareAndSet(obj, prev, newValue));
return prev;
}
/**
* Atomically increments by one the current value of the field of the
* given object managed by this updater.
*
* @param obj An object whose field to get and set
* @return the previous value
*/
public int getAndIncrement(T obj) {
int prev, next;
do {
prev = get(obj);
next = prev + 1;
} while (!compareAndSet(obj, prev, next));
return prev;
}
/**
* Atomically decrements by one the current value of the field of the
* given object managed by this updater.
*
* @param obj An object whose field to get and set
* @return the previous value
*/
public int getAndDecrement(T obj) {
int prev, next;
do {
prev = get(obj);
next = prev - 1;
} while (!compareAndSet(obj, prev, next));
return prev;
}
/**
* Atomically adds the given value to the current value of the field of
* the given object managed by this updater.
*
* @param obj An object whose field to get and set
* @param delta the value to add
* @return the previous value
*/
public int getAndAdd(T obj, int delta) {
int prev, next;
do {
prev = get(obj);
next = prev + delta;
} while (!compareAndSet(obj, prev, next));
return prev;
}
/**
* Atomically increments by one the current value of the field of the
* given object managed by this updater.
*
* @param obj An object whose field to get and set
* @return the updated value
*/
public int incrementAndGet(T obj) {
int prev, next;
do {
prev = get(obj);
next = prev + 1;
} while (!compareAndSet(obj, prev, next));
return next;
}
/**
* Atomically decrements by one the current value of the field of the
* given object managed by this updater.
*
* @param obj An object whose field to get and set
* @return the updated value
*/
public int decrementAndGet(T obj) {
int prev, next;
do {
prev = get(obj);
next = prev - 1;
} while (!compareAndSet(obj, prev, next));
return next;
}
/**
* Atomically adds the given value to the current value of the field of
* the given object managed by this updater.
*
* @param obj An object whose field to get and set
* @param delta the value to add
* @return the updated value
*/
public int addAndGet(T obj, int delta) {
int prev, next;
do {
prev = get(obj);
next = prev + delta;
} while (!compareAndSet(obj, prev, next));
return next;
}
/**
* Atomically updates (with memory effects as specified by {@link
* VarHandle#compareAndSet}) the field of the given object managed
* by this updater with the results of applying the given
* function, returning the previous value. The function should be
* side-effect-free, since it may be re-applied when attempted
* updates fail due to contention among threads.
*
* @param obj An object whose field to get and set
* @param updateFunction a side-effect-free function
* @return the previous value
* @since 1.8
*/
public final int getAndUpdate(T obj, IntUnaryOperator updateFunction) {
int prev, next;
do {
prev = get(obj);
next = updateFunction.applyAsInt(prev);
} while (!compareAndSet(obj, prev, next));
return prev;
}
/**
* Atomically updates (with memory effects as specified by {@link
* VarHandle#compareAndSet}) the field of the given object managed
* by this updater with the results of applying the given
* function, returning the updated value. The function should be
* side-effect-free, since it may be re-applied when attempted
* updates fail due to contention among threads.
*
* @param obj An object whose field to get and set
* @param updateFunction a side-effect-free function
* @return the updated value
* @since 1.8
*/
public final int updateAndGet(T obj, IntUnaryOperator updateFunction) {
int prev, next;
do {
prev = get(obj);
next = updateFunction.applyAsInt(prev);
} while (!compareAndSet(obj, prev, next));
return next;
}
/**
* Atomically updates (with memory effects as specified by {@link
* VarHandle#compareAndSet}) the field of the given object managed
* by this updater with the results of applying the given function
* to the current and given values, returning the previous value.
* The function should be side-effect-free, since it may be
* re-applied when attempted updates fail due to contention among
* threads. The function is applied with the current value as its
* first argument, and the given update as the second argument.
*
* @param obj An object whose field to get and set
* @param x the update value
* @param accumulatorFunction a side-effect-free function of two arguments
* @return the previous value
* @since 1.8
*/
public final int getAndAccumulate(T obj, int x,
IntBinaryOperator accumulatorFunction) {
int prev, next;
do {
prev = get(obj);
next = accumulatorFunction.applyAsInt(prev, x);
} while (!compareAndSet(obj, prev, next));
return prev;
}
/**
* Atomically updates (with memory effects as specified by {@link
* VarHandle#compareAndSet}) the field of the given object managed
* by this updater with the results of applying the given function
* to the current and given values, returning the updated value.
* The function should be side-effect-free, since it may be
* re-applied when attempted updates fail due to contention among
* threads. The function is applied with the current value as its
* first argument, and the given update as the second argument.
*
* @param obj An object whose field to get and set
* @param x the update value
* @param accumulatorFunction a side-effect-free function of two arguments
* @return the updated value
* @since 1.8
*/
public final int accumulateAndGet(T obj, int x,
IntBinaryOperator accumulatorFunction) {
int prev, next;
do {
prev = get(obj);
next = accumulatorFunction.applyAsInt(prev, x);
} while (!compareAndSet(obj, prev, next));
return next;
}
/**
* Standard hotspot implementation using intrinsics.
*/
private static final class AtomicIntegerFieldUpdaterImpl
extends AtomicIntegerFieldUpdater {
private static final Unsafe U = Unsafe.getUnsafe();
private final long offset;
/**
* if field is protected, the subclass constructing updater, else
* the same as tclass
*/
private final Class cclass;
/** class holding the field */
private final Class tclass;
@SuppressWarnings("removal")
AtomicIntegerFieldUpdaterImpl(final Class tclass,
final String fieldName,
final Class caller) {
final Field field;
final int modifiers;
try {
field = AccessController.doPrivileged(
new PrivilegedExceptionAction() {
public Field run() throws NoSuchFieldException {
return tclass.getDeclaredField(fieldName);
}
});
modifiers = field.getModifiers();
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);
}
} catch (PrivilegedActionException pae) {
throw new RuntimeException(pae.getException());
} catch (Exception ex) {
throw new RuntimeException(ex);
}
if (field.getType() != int.class)
throw new IllegalArgumentException("Must be integer type");
if (!Modifier.isVolatile(modifiers))
throw new IllegalArgumentException("Must be volatile type");
// 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);
}
/**
* 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;
}
/**
* 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()
&& class1.getPackageName() == class2.getPackageName();
}
/**
* Checks that target argument is instance of cclass. On
* failure, throws cause.
*/
private final void accessCheck(T obj) {
if (!cclass.isInstance(obj))
throwAccessCheckException(obj);
}
/**
* Throws access exception if accessCheck failed due to
* protected access, else ClassCastException.
*/
private final void throwAccessCheckException(T obj) {
if (cclass == tclass)
throw new ClassCastException();
else
throw new RuntimeException(
new IllegalAccessException(
"Class " +
cclass.getName() +
" can not access a protected member of class " +
tclass.getName() +
" using an instance of " +
obj.getClass().getName()));
}
public final boolean compareAndSet(T obj, int expect, int update) {
accessCheck(obj);
return U.compareAndSetInt(obj, offset, expect, update);
}
public final boolean weakCompareAndSet(T obj, int expect, int update) {
accessCheck(obj);
return U.compareAndSetInt(obj, offset, expect, update);
}
public final void set(T obj, int newValue) {
accessCheck(obj);
U.putIntVolatile(obj, offset, newValue);
}
public final void lazySet(T obj, int newValue) {
accessCheck(obj);
U.putIntRelease(obj, offset, newValue);
}
public final int get(T obj) {
accessCheck(obj);
return U.getIntVolatile(obj, offset);
}
public final int getAndSet(T obj, int newValue) {
accessCheck(obj);
return U.getAndSetInt(obj, offset, newValue);
}
public final int getAndAdd(T obj, int delta) {
accessCheck(obj);
return U.getAndAddInt(obj, offset, delta);
}
public final int getAndIncrement(T obj) {
return getAndAdd(obj, 1);
}
public final int getAndDecrement(T obj) {
return getAndAdd(obj, -1);
}
public final int incrementAndGet(T obj) {
return getAndAdd(obj, 1) + 1;
}
public final int decrementAndGet(T obj) {
return getAndAdd(obj, -1) - 1;
}
public final int addAndGet(T obj, int delta) {
return getAndAdd(obj, delta) + delta;
}
}
}