2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
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
8 package org.opendaylight.yangtools.util;
10 import com.google.common.base.Preconditions;
11 import com.google.common.collect.ForwardingMap;
12 import com.romix.scala.collection.concurrent.TrieMap;
14 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
15 import org.slf4j.Logger;
16 import org.slf4j.LoggerFactory;
19 * A read-only facade in front of a TrieMap. This is what we give out from
20 * MapAdaptor.optimize(). The idea is that we want our read-only users to
21 * share a single snapshot. That snapshot is instantiated lazily either on
22 * first access. Since we never leak the TrieMap and track its size as it
23 * changes, we can cache it for future reference.
25 final class ReadOnlyTrieMap<K, V> extends ForwardingMap<K, V> {
26 @SuppressWarnings("rawtypes")
27 private static final AtomicReferenceFieldUpdater<ReadOnlyTrieMap, TrieMap> UPDATER =
28 AtomicReferenceFieldUpdater.newUpdater(ReadOnlyTrieMap.class, TrieMap.class, "readOnly");
29 private static final Logger LOG = LoggerFactory.getLogger(ReadOnlyTrieMap.class);
30 private final TrieMap<K, V> readWrite;
31 private final int size;
32 private volatile TrieMap<K, V> readOnly;
34 ReadOnlyTrieMap(final TrieMap<K, V> map, final int size) {
36 this.readWrite = Preconditions.checkNotNull(map);
40 Map<K, V> toReadWrite() {
41 final Map<K, V> ret = new ReadWriteTrieMap<>(readWrite.snapshot(), size);
42 LOG.trace("Converted read-only TrieMap {} to read-write {}", this, ret);
47 protected Map<K, V> delegate() {
48 TrieMap<K, V> ret = readOnly;
50 ret = readWrite.readOnlySnapshot();
51 if (!UPDATER.compareAndSet(this, null, ret)) {