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1 files changed, 275 insertions, 0 deletions

diff --git a/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java b/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java
new file mode 100644
index 000000000..24014a9df
--- /dev/null
+++ b/libjava/classpath/external/jsr166/java/util/concurrent/atomic/AtomicReferenceFieldUpdater.java
@@ -0,0 +1,275 @@
+/*
+ * 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/licenses/publicdomain
+ */
+
+package java.util.concurrent.atomic;
+import sun.misc.Unsafe;
+import java.lang.reflect.*;
+
+/**
+ * A reflection-based utility that enables atomic updates to
+ * designated <tt>volatile</tt> reference fields of designated
+ * classes.  This class is designed for use in atomic data structures
+ * in which several reference fields of the same node are
+ * independently subject to atomic updates. For example, a tree node
+ * might be declared as
+ *
+ * <pre>
+ * class Node {
+ *   private volatile Node left, right;
+ *
+ *   private static final AtomicReferenceFieldUpdater&lt;Node, Node&gt; leftUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "left");
+ *   private static AtomicReferenceFieldUpdater&lt;Node, Node&gt; rightUpdater =
+ *     AtomicReferenceFieldUpdater.newUpdater(Node.class, Node.class, "right");
+ *
+ *   Node getLeft() { return left;  }
+ *   boolean compareAndSetLeft(Node expect, Node update) {
+ *     return leftUpdater.compareAndSet(this, expect, update);
+ *   }
+ *   // ... and so on
+ * }
+ * </pre>
+ *
+ * <p>Note that the guarantees of the {@code compareAndSet}
+ * method in this class are weaker than in other atomic classes.
+ * Because this class cannot ensure that all uses of the field
+ * are appropriate for purposes of atomic access, it can
+ * guarantee atomicity only with respect to other invocations of
+ * {@code compareAndSet} and {@code set} on the same updater.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <T> The type of the object holding the updatable field
+ * @param <V> The type of the field
+ */
+public abstract class AtomicReferenceFieldUpdater<T, V>  {
+
+    /**
+     * Creates and returns an updater for objects with the given field.
+     * The Class arguments are needed to check that reflective types and
+     * generic types match.
+     *
+     * @param tclass the class of the objects holding the field.
+     * @param vclass the class of the field
+     * @param fieldName the name of the field to be updated.
+     * @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 <U, W> AtomicReferenceFieldUpdater<U,W> newUpdater(Class<U> tclass, Class<W> vclass, String fieldName) {
+        return new AtomicReferenceFieldUpdaterImpl<U,W>(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 <tt>==</tt> the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to <tt>compareAndSet</tt> and <tt>set</tt>, 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 <tt>==</tt> the
+     * expected value. This method is guaranteed to be atomic with respect to
+     * other calls to <tt>compareAndSet</tt> and <tt>set</tt>, 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 <tt>compareAndSet</tt>.
+     *
+     * @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
+     * <tt>compareAndSet</tt>.
+     *
+     * @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<T,V>
+        extends AtomicReferenceFieldUpdater<T,V> {
+        private static final Unsafe unsafe = Unsafe.getUnsafe();
+        private final long offset;
+        private final Class<T> tclass;
+        private final Class<V> 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<T> tclass,
+                                        Class<V> 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()
+                )
+            );
+        }
+    }
+}