/*
* 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.tomcat.util.collections;
import java.io.Serial;
import java.util.LinkedHashMap;
import java.util.Map;
public class ConcurrentLruCache<T> {
private volatile LimitedLinkedHashMap<T,T> map;
private final Object lock = new Object();
public ConcurrentLruCache(int limit) {
setLimit(limit);
}
public void add(T entry) {
if (map == null) {
return;
}
synchronized (lock) {
if (map == null) {
return;
}
map.put(entry, entry);
}
}
public boolean contains(T entry) {
if (map == null) {
return false;
}
synchronized (lock) {
if (map == null) {
return false;
}
return map.get(entry) != null;
}
}
public void clear() {
if (map == null) {
return;
}
synchronized (lock) {
if (map == null) {
return;
}
map.clear();
}
}
public void setLimit(int limit) {
synchronized (lock) {
if (limit > 0) {
Map<T,T> oldMap = map;
map = new LimitedLinkedHashMap<>(limit);
if (oldMap != null) {
map.putAll(oldMap);
}
} else {
map = null;
}
}
}
public int getLimit() {
synchronized (lock) {
if (map == null) {
return -1;
} else {
return map.getLimit();
}
}
}
private static class LimitedLinkedHashMap<K, V> extends LinkedHashMap<K,V> {
@Serial
private static final long serialVersionUID = 1L;
private final int limit;
LimitedLinkedHashMap(int limit) {
super(16, 0.75F, true);
this.limit = limit;
}
@Override
protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
return size() > limit;
}
private int getLimit() {
return limit;
}
}
}