8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/util/concurrent/atomic/AtomicMarkableReference.java

@@ -0,0 +1,209 @@
+/*
+ * 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.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+/**
+ * An {@code AtomicMarkableReference} maintains an object reference
+ * along with a mark bit, that can be updated atomically.
+ *
+ * <p>Implementation note: This implementation maintains markable
+ * references by creating internal objects representing "boxed"
+ * [reference, boolean] pairs.
+ *
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicMarkableReference<V> {
+
+    private static class Pair<T> {
+        final T reference;
+        final boolean mark;
+        private Pair(T reference, boolean mark) {
+            this.reference = reference;
+            this.mark = mark;
+        }
+        static <T> Pair<T> of(T reference, boolean mark) {
+            return new Pair<T>(reference, mark);
+        }
+    }
+
+    private volatile Pair<V> pair;
+
+    /**
+     * Creates a new {@code AtomicMarkableReference} with the given
+     * initial values.
+     *
+     * @param initialRef the initial reference
+     * @param initialMark the initial mark
+     */
+    public AtomicMarkableReference(V initialRef, boolean initialMark) {
+        pair = Pair.of(initialRef, initialMark);
+    }
+
+    /**
+     * Returns the current value of the reference.
+     *
+     * @return the current value of the reference
+     */
+    public V getReference() {
+        return pair.reference;
+    }
+
+    /**
+     * Returns the current value of the mark.
+     *
+     * @return the current value of the mark
+     */
+    public boolean isMarked() {
+        return pair.mark;
+    }
+
+    /**
+     * Returns the current values of both the reference and the mark.
+     * Typical usage is {@code boolean[1] holder; ref = v.get(holder); }.
+     *
+     * @param markHolder an array of size of at least one. On return,
+     * {@code markHolder[0]} will hold the value of the mark.
+     * @return the current value of the reference
+     */
+    public V get(boolean[] markHolder) {
+        Pair<V> pair = this.pair;
+        markHolder[0] = pair.mark;
+        return pair.reference;
+    }
+
+    /**
+     * Atomically sets the value of both the reference and mark
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current mark is equal to the expected mark.
+     *
+     * <p><a href="package-summary.html#weakCompareAndSet">May fail
+     * spuriously and does not provide ordering guarantees</a>, so is
+     * only rarely an appropriate alternative to {@code compareAndSet}.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedMark the expected value of the mark
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean weakCompareAndSet(V       expectedReference,
+                                     V       newReference,
+                                     boolean expectedMark,
+                                     boolean newMark) {
+        return compareAndSet(expectedReference, newReference,
+                             expectedMark, newMark);
+    }
+
+    /**
+     * Atomically sets the value of both the reference and mark
+     * to the given update values if the
+     * current reference is {@code ==} to the expected reference
+     * and the current mark is equal to the expected mark.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newReference the new value for the reference
+     * @param expectedMark the expected value of the mark
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean compareAndSet(V       expectedReference,
+                                 V       newReference,
+                                 boolean expectedMark,
+                                 boolean newMark) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            expectedMark == current.mark &&
+            ((newReference == current.reference &&
+              newMark == current.mark) ||
+             casPair(current, Pair.of(newReference, newMark)));
+    }
+
+    /**
+     * Unconditionally sets the value of both the reference and mark.
+     *
+     * @param newReference the new value for the reference
+     * @param newMark the new value for the mark
+     */
+    public void set(V newReference, boolean newMark) {
+        Pair<V> current = pair;
+        if (newReference != current.reference || newMark != current.mark)
+            this.pair = Pair.of(newReference, newMark);
+    }
+
+    /**
+     * Atomically sets the value of the mark to the given update value
+     * if the current reference is {@code ==} to the expected
+     * reference.  Any given invocation of this operation may fail
+     * (return {@code false}) spuriously, but repeated invocation
+     * when the current value holds the expected value and no other
+     * thread is also attempting to set the value will eventually
+     * succeed.
+     *
+     * @param expectedReference the expected value of the reference
+     * @param newMark the new value for the mark
+     * @return {@code true} if successful
+     */
+    public boolean attemptMark(V expectedReference, boolean newMark) {
+        Pair<V> current = pair;
+        return
+            expectedReference == current.reference &&
+            (newMark == current.mark ||
+             casPair(current, Pair.of(expectedReference, newMark)));
+    }
+
+    // VarHandle mechanics
+    private static final VarHandle PAIR;
+    static {
+        try {
+            MethodHandles.Lookup l = MethodHandles.lookup();
+            PAIR = l.findVarHandle(AtomicMarkableReference.class, "pair",
+                                   Pair.class);
+        } catch (ReflectiveOperationException e) {
+            throw new Error(e);
+        }
+    }
+
+    private boolean casPair(Pair<V> cmp, Pair<V> val) {
+        return PAIR.compareAndSet(this, cmp, val);
+    }
+}