/**
* Copyright 2010 The Apache Software Foundation
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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.apache.hadoop.hbase.util;
import java.lang.ref.ReferenceQueue;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* A Map that uses Soft Reference values internally. Use as a simple cache.
*
* @param <K> key class
* @param <V> value class
*/
public class SoftValueMap<K,V> implements Map<K,V> {
private final Map<K, SoftValue<K,V>> internalMap =
new HashMap<K, SoftValue<K,V>>();
private final ReferenceQueue<?> rq;
public SoftValueMap() {
this(new ReferenceQueue());
}
public SoftValueMap(final ReferenceQueue<?> rq) {
this.rq = rq;
}
/**
* Checks soft references and cleans any that have been placed on
* ReferenceQueue.
* @return How many references cleared.
*/
@SuppressWarnings({"unchecked"})
public int checkReferences() {
int i = 0;
for (Object obj; (obj = this.rq.poll()) != null;) {
i++;
this.internalMap.remove(((SoftValue<K,V>)obj).getKey());
}
return i;
}
public V put(K key, V value) {
checkReferences();
SoftValue<K,V> oldValue = this.internalMap.put(key,
new SoftValue<K,V>(key, value, this.rq));
return oldValue == null ? null : oldValue.get();
}
@SuppressWarnings("unchecked")
public void putAll(Map map) {
throw new RuntimeException("Not implemented");
}
@SuppressWarnings({"SuspiciousMethodCalls"})
public V get(Object key) {
checkReferences();
SoftValue<K,V> value = this.internalMap.get(key);
if (value == null) {
return null;
}
if (value.get() == null) {
this.internalMap.remove(key);
return null;
}
return value.get();
}
public V remove(Object key) {
checkReferences();
SoftValue<K,V> value = this.internalMap.remove(key);
return value == null ? null : value.get();
}
public boolean containsKey(Object key) {
checkReferences();
return this.internalMap.containsKey(key);
}
public boolean containsValue(Object value) {
/* checkReferences();
return internalMap.containsValue(value);*/
throw new UnsupportedOperationException("Don't support containsValue!");
}
public boolean isEmpty() {
checkReferences();
return this.internalMap.isEmpty();
}
public int size() {
checkReferences();
return this.internalMap.size();
}
public void clear() {
checkReferences();
this.internalMap.clear();
}
public Set<K> keySet() {
checkReferences();
return this.internalMap.keySet();
}
public Set<Map.Entry<K,V>> entrySet() {
checkReferences();
Set<Map.Entry<K, SoftValue<K,V>>> entries = this.internalMap.entrySet();
Set<Map.Entry<K, V>> real_entries = new HashSet<Map.Entry<K,V>>();
for(Map.Entry<K, SoftValue<K,V>> entry : entries) {
real_entries.add(entry.getValue());
}
return real_entries;
}
public Collection<V> values() {
checkReferences();
Collection<SoftValue<K,V>> softValues = this.internalMap.values();
ArrayList<V> hardValues = new ArrayList<V>();
for(SoftValue<K,V> softValue : softValues) {
hardValues.add(softValue.get());
}
return hardValues;
}
}