# HG changeset patch # User Jaroslav Tulach # Date 1423510356 -3600 # Node ID f0c5b36d931159eb319003e11083d48f89b0bd83 # Parent f19e2fe0855a576755ac43bd1d330118eca2f8bb# Parent b208ff5b7dbcf7d2f40f9b435f34f45fa0a8a96b Merging in new JDK classes for emulation: Updaters diff -r f19e2fe0855a -r f0c5b36d9311 rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java Mon Feb 09 20:32:36 2015 +0100 @@ -0,0 +1,346 @@ +/* + * 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 sun.misc.Unsafe; +import java.lang.reflect.*; + +/** + * A reflection-based utility that enables atomic updates to + * designated {@code volatile int} fields of designated classes. + * This class is designed for use in atomic data structures in which + * several fields of the same node are independently subject to atomic + * updates. + * + *

Note that the guarantees of the {@code compareAndSet} + * method in this class are weaker than in other atomic classes. + * Because this class cannot ensure that all uses of the field + * are appropriate for purposes of atomic access, it can + * guarantee atomicity only with respect to other invocations of + * {@code compareAndSet} and {@code set} on the same updater. + * + * @since 1.5 + * @author Doug Lea + * @param The type of the object holding the updatable field + */ +public abstract class AtomicIntegerFieldUpdater { + /** + * Creates and returns an updater for objects with the given field. + * The Class argument is needed to check that reflective types and + * generic types match. + * + * @param tclass the class of the objects holding the field + * @param fieldName the name of the field to be updated + * @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 + */ + public static AtomicIntegerFieldUpdater newUpdater(Class tclass, String fieldName) { + return new AtomicIntegerFieldUpdaterImpl(tclass, fieldName); + } + + /** + * 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 true if successful + * @throws ClassCastException if {@code obj} is not an instance + * of the class possessing the field established in the constructor + */ + public abstract boolean compareAndSet(T obj, int expect, int update); + + /** + * Atomically sets the field of the given object managed by this updater + * to the given updated value if the current value {@code ==} the + * expected value. This method is guaranteed to be atomic with respect to + * other calls to {@code compareAndSet} and {@code set}, but not + * necessarily with respect to other changes in the field. + * + *

May fail spuriously + * and does not provide ordering guarantees, so is only rarely an + * appropriate alternative to {@code compareAndSet}. + * + * @param obj An object whose field to conditionally set + * @param expect the expected value + * @param update the new value + * @return true if successful + * @throws ClassCastException if {@code obj} is not an instance + * of the class possessing the field established in the constructor + */ + public abstract boolean weakCompareAndSet(T obj, int expect, int update); + + /** + * Sets the field of the given object managed by this updater to the + * given updated value. This operation is guaranteed to act as a volatile + * store with respect to subsequent invocations of {@code compareAndSet}. + * + * @param obj An object whose field to set + * @param newValue the new value + */ + public abstract void set(T obj, int newValue); + + /** + * Eventually sets the field of the given object managed by this + * updater to the given updated value. + * + * @param obj An object whose field to set + * @param newValue the new value + * @since 1.6 + */ + public abstract void lazySet(T obj, int newValue); + + + /** + * Gets the current value held in the field of the given object managed + * by this updater. + * + * @param obj An object whose field to get + * @return the current value + */ + public abstract int get(T obj); + + /** + * Atomically sets the field of the given object managed by this updater + * to the given value and returns the old value. + * + * @param obj An object whose field to get and set + * @param newValue the new value + * @return the previous value + */ + public int getAndSet(T obj, int newValue) { + for (;;) { + int current = get(obj); + if (compareAndSet(obj, current, newValue)) + return current; + } + } + + /** + * 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) { + for (;;) { + int current = get(obj); + int next = current + 1; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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) { + for (;;) { + int current = get(obj); + int next = current - 1; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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) { + for (;;) { + int current = get(obj); + int next = current + delta; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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) { + for (;;) { + int current = get(obj); + int next = current + 1; + if (compareAndSet(obj, current, 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) { + for (;;) { + int current = get(obj); + int next = current - 1; + if (compareAndSet(obj, current, 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) { + for (;;) { + int current = get(obj); + int next = current + delta; + if (compareAndSet(obj, current, next)) + return next; + } + } + + /** + * Standard hotspot implementation using intrinsics + */ + private static class AtomicIntegerFieldUpdaterImpl extends AtomicIntegerFieldUpdater { + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private final long offset; + private final Class tclass; + private final Class cclass; + + AtomicIntegerFieldUpdaterImpl(Class tclass, String fieldName) { + Field field = null; + Class caller = null; + int modifiers = 0; + try { + field = tclass.getDeclaredField(fieldName); + caller = sun.reflect.Reflection.getCallerClass(3); + modifiers = field.getModifiers(); + sun.reflect.misc.ReflectUtil.ensureMemberAccess( + caller, tclass, null, modifiers); + sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); + } catch (Exception ex) { + throw new RuntimeException(ex); + } + + Class fieldt = field.getType(); + if (fieldt != int.class) + throw new IllegalArgumentException("Must be integer type"); + + if (!Modifier.isVolatile(modifiers)) + throw new IllegalArgumentException("Must be volatile type"); + + this.cclass = (Modifier.isProtected(modifiers) && + caller != tclass) ? caller : null; + this.tclass = tclass; + offset = unsafe.objectFieldOffset(field); + } + + private void fullCheck(T obj) { + if (!tclass.isInstance(obj)) + throw new ClassCastException(); + if (cclass != null) + ensureProtectedAccess(obj); + } + + public boolean compareAndSet(T obj, int expect, int update) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.compareAndSwapInt(obj, offset, expect, update); + } + + public boolean weakCompareAndSet(T obj, int expect, int update) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.compareAndSwapInt(obj, offset, expect, update); + } + + public void set(T obj, int newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + unsafe.putIntVolatile(obj, offset, newValue); + } + + public void lazySet(T obj, int newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + unsafe.putOrderedInt(obj, offset, newValue); + } + + public final int get(T obj) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.getIntVolatile(obj, offset); + } + + private void ensureProtectedAccess(T obj) { + if (cclass.isInstance(obj)) { + return; + } + 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() + ) + ); + } + } +} diff -r f19e2fe0855a -r f0c5b36d9311 rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicLongFieldUpdater.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicLongFieldUpdater.java Mon Feb 09 20:32:36 2015 +0100 @@ -0,0 +1,436 @@ +/* + * 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 sun.misc.Unsafe; +import java.lang.reflect.*; + +/** + * A reflection-based utility that enables atomic updates to + * designated {@code volatile long} fields of designated classes. + * This class is designed for use in atomic data structures in which + * several fields of the same node are independently subject to atomic + * updates. + * + *

Note that the guarantees of the {@code compareAndSet} + * method in this class are weaker than in other atomic classes. + * Because this class cannot ensure that all uses of the field + * are appropriate for purposes of atomic access, it can + * guarantee atomicity only with respect to other invocations of + * {@code compareAndSet} and {@code set} on the same updater. + * + * @since 1.5 + * @author Doug Lea + * @param The type of the object holding the updatable field + */ +public abstract class AtomicLongFieldUpdater { + /** + * 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. + * @return the updater + * @throws IllegalArgumentException if the field is not a + * volatile long type. + * @throws RuntimeException with a nested reflection-based + * exception if the class does not hold field or is the wrong type. + */ + public static AtomicLongFieldUpdater newUpdater(Class tclass, String fieldName) { + if (AtomicLong.VM_SUPPORTS_LONG_CAS) + return new CASUpdater(tclass, fieldName); + else + return new LockedUpdater(tclass, fieldName); + } + + /** + * Protected do-nothing constructor for use by subclasses. + */ + protected AtomicLongFieldUpdater() { + } + + /** + * 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 true if successful. + * @throws ClassCastException if {@code obj} is not an instance + * of the class possessing the field established in the constructor. + */ + public abstract boolean compareAndSet(T obj, long expect, long update); + + /** + * Atomically sets the field of the given object managed by this updater + * to the given updated value if the current value {@code ==} the + * expected value. This method is guaranteed to be atomic with respect to + * other calls to {@code compareAndSet} and {@code set}, but not + * necessarily with respect to other changes in the field. + * + *

May fail spuriously + * and does not provide ordering guarantees, so is only rarely an + * appropriate alternative to {@code compareAndSet}. + * + * @param obj An object whose field to conditionally set + * @param expect the expected value + * @param update the new value + * @return true if successful. + * @throws ClassCastException if {@code obj} is not an instance + * of the class possessing the field established in the constructor. + */ + public abstract boolean weakCompareAndSet(T obj, long expect, long 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, long 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, long newValue); + + /** + * Gets the current value held in the field of the given object managed + * by this updater. + * + * @param obj An object whose field to get + * @return the current value + */ + public abstract long 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 long getAndSet(T obj, long newValue) { + for (;;) { + long current = get(obj); + if (compareAndSet(obj, current, newValue)) + return current; + } + } + + /** + * 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 long getAndIncrement(T obj) { + for (;;) { + long current = get(obj); + long next = current + 1; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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 long getAndDecrement(T obj) { + for (;;) { + long current = get(obj); + long next = current - 1; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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 long getAndAdd(T obj, long delta) { + for (;;) { + long current = get(obj); + long next = current + delta; + if (compareAndSet(obj, current, next)) + return current; + } + } + + /** + * 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 long incrementAndGet(T obj) { + for (;;) { + long current = get(obj); + long next = current + 1; + if (compareAndSet(obj, current, 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 long decrementAndGet(T obj) { + for (;;) { + long current = get(obj); + long next = current - 1; + if (compareAndSet(obj, current, 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 long addAndGet(T obj, long delta) { + for (;;) { + long current = get(obj); + long next = current + delta; + if (compareAndSet(obj, current, next)) + return next; + } + } + + private static class CASUpdater extends AtomicLongFieldUpdater { + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private final long offset; + private final Class tclass; + private final Class cclass; + + CASUpdater(Class tclass, String fieldName) { + Field field = null; + Class caller = null; + int modifiers = 0; + try { + field = tclass.getDeclaredField(fieldName); + caller = sun.reflect.Reflection.getCallerClass(3); + modifiers = field.getModifiers(); + sun.reflect.misc.ReflectUtil.ensureMemberAccess( + caller, tclass, null, modifiers); + sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); + } catch (Exception ex) { + throw new RuntimeException(ex); + } + + Class fieldt = field.getType(); + if (fieldt != long.class) + throw new IllegalArgumentException("Must be long type"); + + if (!Modifier.isVolatile(modifiers)) + throw new IllegalArgumentException("Must be volatile type"); + + this.cclass = (Modifier.isProtected(modifiers) && + caller != tclass) ? caller : null; + this.tclass = tclass; + offset = unsafe.objectFieldOffset(field); + } + + private void fullCheck(T obj) { + if (!tclass.isInstance(obj)) + throw new ClassCastException(); + if (cclass != null) + ensureProtectedAccess(obj); + } + + public boolean compareAndSet(T obj, long expect, long update) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.compareAndSwapLong(obj, offset, expect, update); + } + + public boolean weakCompareAndSet(T obj, long expect, long update) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.compareAndSwapLong(obj, offset, expect, update); + } + + public void set(T obj, long newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + unsafe.putLongVolatile(obj, offset, newValue); + } + + public void lazySet(T obj, long newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + unsafe.putOrderedLong(obj, offset, newValue); + } + + public long get(T obj) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + return unsafe.getLongVolatile(obj, offset); + } + + private void ensureProtectedAccess(T obj) { + if (cclass.isInstance(obj)) { + return; + } + throw new RuntimeException( + new IllegalAccessException("Class " + + cclass.getName() + + " can not access a protected member of class " + + tclass.getName() + + " using an instance of " + + obj.getClass().getName() + ) + ); + } + } + + + private static class LockedUpdater extends AtomicLongFieldUpdater { + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private final long offset; + private final Class tclass; + private final Class cclass; + + LockedUpdater(Class tclass, String fieldName) { + Field field = null; + Class caller = null; + int modifiers = 0; + try { + field = tclass.getDeclaredField(fieldName); + caller = sun.reflect.Reflection.getCallerClass(3); + modifiers = field.getModifiers(); + sun.reflect.misc.ReflectUtil.ensureMemberAccess( + caller, tclass, null, modifiers); + sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); + } catch (Exception ex) { + throw new RuntimeException(ex); + } + + Class fieldt = field.getType(); + if (fieldt != long.class) + throw new IllegalArgumentException("Must be long type"); + + if (!Modifier.isVolatile(modifiers)) + throw new IllegalArgumentException("Must be volatile type"); + + this.cclass = (Modifier.isProtected(modifiers) && + caller != tclass) ? caller : null; + this.tclass = tclass; + offset = unsafe.objectFieldOffset(field); + } + + private void fullCheck(T obj) { + if (!tclass.isInstance(obj)) + throw new ClassCastException(); + if (cclass != null) + ensureProtectedAccess(obj); + } + + public boolean compareAndSet(T obj, long expect, long update) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + synchronized (this) { + long v = unsafe.getLong(obj, offset); + if (v != expect) + return false; + unsafe.putLong(obj, offset, update); + return true; + } + } + + public boolean weakCompareAndSet(T obj, long expect, long update) { + return compareAndSet(obj, expect, update); + } + + public void set(T obj, long newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + synchronized (this) { + unsafe.putLong(obj, offset, newValue); + } + } + + public void lazySet(T obj, long newValue) { + set(obj, newValue); + } + + public long get(T obj) { + if (obj == null || obj.getClass() != tclass || cclass != null) fullCheck(obj); + synchronized (this) { + return unsafe.getLong(obj, offset); + } + } + + private void ensureProtectedAccess(T obj) { + if (cclass.isInstance(obj)) { + return; + } + 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() + ) + ); + } + } +} diff -r f19e2fe0855a -r f0c5b36d9311 rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java Mon Feb 09 20:32:36 2015 +0100 @@ -0,0 +1,304 @@ +/* + * 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 sun.misc.Unsafe; +import java.lang.reflect.*; + +/** + * A reflection-based utility that enables atomic updates to + * designated {@code volatile} reference fields of designated + * classes. This class is designed for use in atomic data structures + * in which several reference fields of the same node are + * independently subject to atomic updates. For example, a tree node + * might be declared as + * + * 

 {@code
+ * class Node {
+ *   private volatile Node left, right;
+ *
+ *   private static final AtomicReferenceFieldUpdater leftUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left");
+ *   private static AtomicReferenceFieldUpdater rightUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");
+ *
+ *   Node getLeft() { return left;  }
+ *   boolean compareAndSetLeft(Node expect, Node update) {
+ *     return leftUpdater.compareAndSet(this, expect, update);
+ *   }
+ *   // ... and so on
+ * }}
+ * + *

Note that the guarantees of the {@code compareAndSet} + * method in this class are weaker than in other atomic classes. + * Because this class cannot ensure that all uses of the field + * are appropriate for purposes of atomic access, it can + * guarantee atomicity only with respect to other invocations of + * {@code compareAndSet} and {@code set} on the same updater. + * + * @since 1.5 + * @author Doug Lea + * @param The type of the object holding the updatable field + * @param The type of the field + */ +public abstract class AtomicReferenceFieldUpdater { + + /** + * Creates and returns an updater for objects with the given field. + * The Class arguments are needed to check that reflective types and + * generic types match. + * + * @param tclass the class of the objects holding the field. + * @param vclass the class of the field + * @param fieldName the name of the field to be updated. + * @return the updater + * @throws IllegalArgumentException if the field is not a volatile reference type. + * @throws RuntimeException with a nested reflection-based + * exception if the class does not hold field or is the wrong type. + */ + public static AtomicReferenceFieldUpdater newUpdater(Class tclass, Class vclass, String fieldName) { + return new AtomicReferenceFieldUpdaterImpl(tclass, + vclass, + fieldName); + } + + /** + * Protected do-nothing constructor for use by subclasses. + */ + protected AtomicReferenceFieldUpdater() { + } + + /** + * Atomically sets the field of the given object managed by this updater + * to the given updated value if the current value {@code ==} the + * expected value. This method is guaranteed to be atomic with respect to + * other calls to {@code compareAndSet} and {@code set}, but not + * necessarily with respect to other changes in the field. + * + * @param obj An object whose field to conditionally set + * @param expect the expected value + * @param update the new value + * @return true if successful. + */ + public abstract boolean compareAndSet(T obj, V expect, V update); + + /** + * Atomically sets the field of the given object managed by this updater + * to the given updated value if the current value {@code ==} the + * expected value. This method is guaranteed to be atomic with respect to + * other calls to {@code compareAndSet} and {@code set}, but not + * necessarily with respect to other changes in the field. + * + *

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 true if successful. + */ + public abstract boolean weakCompareAndSet(T obj, V expect, V update); + + /** + * Sets the field of the given object managed by this updater to the + * given updated value. This operation is guaranteed to act as a volatile + * store with respect to subsequent invocations of {@code compareAndSet}. + * + * @param obj An object whose field to set + * @param newValue the new value + */ + public abstract void set(T obj, V newValue); + + /** + * Eventually sets the field of the given object managed by this + * updater to the given updated value. + * + * @param obj An object whose field to set + * @param newValue the new value + * @since 1.6 + */ + public abstract void lazySet(T obj, V newValue); + + /** + * Gets the current value held in the field of the given object managed + * by this updater. + * + * @param obj An object whose field to get + * @return the current value + */ + public abstract V get(T obj); + + /** + * Atomically sets the field of the given object managed by this updater + * to the given value and returns the old value. + * + * @param obj An object whose field to get and set + * @param newValue the new value + * @return the previous value + */ + public V getAndSet(T obj, V newValue) { + for (;;) { + V current = get(obj); + if (compareAndSet(obj, current, newValue)) + return current; + } + } + + private static final class AtomicReferenceFieldUpdaterImpl + extends AtomicReferenceFieldUpdater { + private static final Unsafe unsafe = Unsafe.getUnsafe(); + private final long offset; + private final Class tclass; + private final Class vclass; + private final Class cclass; + + /* + * Internal type checks within all update methods contain + * internal inlined optimizations checking for the common + * cases where the class is final (in which case a simple + * getClass comparison suffices) or is of type Object (in + * which case no check is needed because all objects are + * instances of Object). The Object case is handled simply by + * setting vclass to null in constructor. The targetCheck and + * updateCheck methods are invoked when these faster + * screenings fail. + */ + + AtomicReferenceFieldUpdaterImpl(Class tclass, + Class vclass, + String fieldName) { + Field field = null; + Class fieldClass = null; + Class caller = null; + int modifiers = 0; + try { + field = tclass.getDeclaredField(fieldName); + caller = sun.reflect.Reflection.getCallerClass(3); + modifiers = field.getModifiers(); + sun.reflect.misc.ReflectUtil.ensureMemberAccess( + caller, tclass, null, modifiers); + sun.reflect.misc.ReflectUtil.checkPackageAccess(tclass); + fieldClass = field.getType(); + } catch (Exception ex) { + throw new RuntimeException(ex); + } + + if (vclass != fieldClass) + throw new ClassCastException(); + + if (!Modifier.isVolatile(modifiers)) + throw new IllegalArgumentException("Must be volatile type"); + + this.cclass = (Modifier.isProtected(modifiers) && + caller != tclass) ? caller : null; + this.tclass = tclass; + if (vclass == Object.class) + this.vclass = null; + else + this.vclass = vclass; + offset = unsafe.objectFieldOffset(field); + } + + void targetCheck(T obj) { + if (!tclass.isInstance(obj)) + throw new ClassCastException(); + if (cclass != null) + ensureProtectedAccess(obj); + } + + void updateCheck(T obj, V update) { + if (!tclass.isInstance(obj) || + (update != null && vclass != null && !vclass.isInstance(update))) + throw new ClassCastException(); + if (cclass != null) + ensureProtectedAccess(obj); + } + + public boolean compareAndSet(T obj, V expect, V update) { + if (obj == null || obj.getClass() != tclass || cclass != null || + (update != null && vclass != null && + vclass != update.getClass())) + updateCheck(obj, update); + return unsafe.compareAndSwapObject(obj, offset, expect, update); + } + + public boolean weakCompareAndSet(T obj, V expect, V update) { + // same implementation as strong form for now + if (obj == null || obj.getClass() != tclass || cclass != null || + (update != null && vclass != null && + vclass != update.getClass())) + updateCheck(obj, update); + return unsafe.compareAndSwapObject(obj, offset, expect, update); + } + + public void set(T obj, V newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null || + (newValue != null && vclass != null && + vclass != newValue.getClass())) + updateCheck(obj, newValue); + unsafe.putObjectVolatile(obj, offset, newValue); + } + + public void lazySet(T obj, V newValue) { + if (obj == null || obj.getClass() != tclass || cclass != null || + (newValue != null && vclass != null && + vclass != newValue.getClass())) + updateCheck(obj, newValue); + unsafe.putOrderedObject(obj, offset, newValue); + } + + public V get(T obj) { + if (obj == null || obj.getClass() != tclass || cclass != null) + targetCheck(obj); + return (V)unsafe.getObjectVolatile(obj, offset); + } + + private void ensureProtectedAccess(T obj) { + if (cclass.isInstance(obj)) { + return; + } + 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() + ) + ); + } + } +}