/*
* Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.yangtools.util;
import com.google.common.base.Preconditions;
import com.google.common.collect.ForwardingMap;
import com.romix.scala.collection.concurrent.TrieMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A read-only facade in front of a TrieMap. This is what we give out from
* MapAdaptor.optimize(). The idea is that we want our read-only users to
* share a single snapshot. That snapshot is instantiated lazily either on
* first access. Since we never leak the TrieMap and track its size as it
* changes, we can cache it for future reference.
*/
final class ReadOnlyTrieMap<K, V> extends ForwardingMap<K, V> {
@SuppressWarnings("rawtypes")
private static final AtomicReferenceFieldUpdater<ReadOnlyTrieMap, TrieMap> UPDATER =
AtomicReferenceFieldUpdater.newUpdater(ReadOnlyTrieMap.class, TrieMap.class, "readOnly");
private static final Logger LOG = LoggerFactory.getLogger(ReadOnlyTrieMap.class);
private final TrieMap<K, V> readWrite;
private final int size;
private volatile TrieMap<K, V> readOnly;
ReadOnlyTrieMap(final TrieMap<K, V> map, final int size) {
super();
this.readWrite = Preconditions.checkNotNull(map);
this.size = size;
}
Map<K, V> toReadWrite() {
final Map<K, V> ret = new ReadWriteTrieMap<>(readWrite.snapshot(), size);
LOG.trace("Converted read-only TrieMap {} to read-write {}", this, ret);
return ret;
}
@Override
protected Map<K, V> delegate() {
TrieMap<K, V> ret = readOnly;
if (ret == null) {
ret = readWrite.readOnlySnapshot();
if (!UPDATER.compareAndSet(this, null, ret)) {
ret = readOnly;
}
}
return ret;
}
@Override
public int size() {
return size;
}
}