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;
13 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
14 import org.opendaylight.yangtools.triemap.ImmutableTrieMap;
15 import org.opendaylight.yangtools.triemap.MutableTrieMap;
16 import org.slf4j.Logger;
17 import org.slf4j.LoggerFactory;
20 * A read-only facade in front of a TrieMap. This is what we give out from
21 * MapAdaptor.optimize(). The idea is that we want our read-only users to
22 * share a single snapshot. That snapshot is instantiated lazily either on
23 * first access. Since we never leak the TrieMap and track its size as it
24 * changes, we can cache it for future reference.
26 final class ReadOnlyTrieMap<K, V> extends ForwardingMap<K, V> {
27 @SuppressWarnings("rawtypes")
28 private static final AtomicReferenceFieldUpdater<ReadOnlyTrieMap, ImmutableTrieMap> UPDATER =
29 AtomicReferenceFieldUpdater.newUpdater(ReadOnlyTrieMap.class, ImmutableTrieMap.class, "readOnly");
30 private static final Logger LOG = LoggerFactory.getLogger(ReadOnlyTrieMap.class);
31 private final MutableTrieMap<K, V> readWrite;
32 private final int size;
33 private volatile ImmutableTrieMap<K, V> readOnly;
35 ReadOnlyTrieMap(final MutableTrieMap<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.mutableSnapshot(), size);
42 LOG.trace("Converted read-only TrieMap {} to read-write {}", this, ret);
47 protected Map<K, V> delegate() {
48 ImmutableTrieMap<K, V> ret = readOnly;
50 ret = readWrite.immutableSnapshot();
51 if (!UPDATER.compareAndSet(this, null, ret)) {