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/*
* Licensed to Elastic Search and Shay Banon under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Elastic Search licenses this
* file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.common.util.concurrent;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
/**
* Provides the semantics of a thread safe copy on write map.
*
* @author kimchy (Shay Banon)
*/
@ThreadSafe
public class CopyOnWriteMap implements ConcurrentMap {
private volatile Map map = new HashMap();
public void clear() {
map = new HashMap();
}
public boolean containsKey(Object key) {
return map.containsKey(key);
}
public boolean containsValue(Object value) {
return map.containsValue(value);
}
public Set> entrySet() {
return map.entrySet();
}
public V get(Object key) {
return map.get(key);
}
public boolean isEmpty() {
return map.isEmpty();
}
public Set keySet() {
return map.keySet();
}
public V put(K key, V value) {
synchronized (this) {
Map copyMap = copyMap();
V put = copyMap.put(key, value);
map = copyMap;
return put;
}
}
public synchronized void putAll(Map t) {
Map copyMap = copyMap();
copyMap.putAll(t);
map = copyMap;
}
public synchronized V remove(Object key) {
Map copyMap = copyMap();
V remove = copyMap.remove(key);
map = copyMap;
return remove;
}
public int size() {
return map.size();
}
public Collection values() {
return map.values();
}
private Map copyMap() {
return new HashMap(map);
}
public synchronized V putIfAbsent(K key, V value) {
V v = map.get(key);
if (v == null) {
Map copyMap = copyMap();
copyMap.put(key, value);
map = copyMap;
}
return v;
}
public synchronized boolean remove(Object key, Object value) {
V v = map.get(key);
if (v != null && v.equals(value)) {
Map copyMap = copyMap();
copyMap.remove(key);
map = copyMap;
return true;
}
return false;
}
public synchronized V replace(K key, V value) {
V v = map.get(key);
if (v != null) {
Map copyMap = copyMap();
copyMap.put(key, value);
map = copyMap;
}
return v;
}
public synchronized boolean replace(K key, V oldValue, V newValue) {
V v = map.get(key);
if (v != null && v.equals(oldValue)) {
Map copyMap = copyMap();
copyMap.put(key, newValue);
map = copyMap;
return true;
}
return false;
}
}