opendaylight/md-sal/sal-dom-spi/src/main/java/org/opendaylight/controller/md/sal/dom/spi/RegistrationTreeSnapshot.java

   1 /**
   2  * Copyright (c) 2015 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.md.sal.dom.spi;
   9
  10 import com.google.common.base.Preconditions;
  11 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
  12 import java.util.concurrent.locks.Lock;
  13
  14 /**
  15  * A stable read-only snapshot of a {@link AbstractRegistrationTree}.
  16  *
  17  * @author Robert Varga
  18  */
  19 public final class RegistrationTreeSnapshot<T> implements AutoCloseable {
  20     @SuppressWarnings("rawtypes")
  21     private static final AtomicIntegerFieldUpdater<RegistrationTreeSnapshot> CLOSED_UPDATER = AtomicIntegerFieldUpdater.newUpdater(RegistrationTreeSnapshot.class, "closed");
  22     private final RegistrationTreeNode<T> node;
  23     private final Lock lock;
  24
  25     // Used via CLOSED_UPDATER
  26     @SuppressWarnings("unused")
  27     private volatile int closed = 0;
  28
  29     RegistrationTreeSnapshot(final Lock lock, final RegistrationTreeNode<T> node) {
  30         this.lock = Preconditions.checkNotNull(lock);
  31         this.node = Preconditions.checkNotNull(node);
  32     }
  33
  34     public RegistrationTreeNode<T> getRootNode() {
  35         return node;
  36     }
  37
  38     @Override
  39     public void close() {
  40         if (CLOSED_UPDATER.compareAndSet(this, 0, 1)) {
  41             lock.unlock();
  42         }
  43     }
  44 }