package org.apache.commons.ognl.internal;

 /*

  * 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.

  */

 /*

  * $Id: ReentrantReadWriteLockCache.java 1194954 2011-10-29 18:00:27Z mcucchiara $

  */

 import org.apache.commons.ognl.internal.entry.CacheEntryFactory;

 import java.util.HashMap;

 import java.util.Map;

 import java.util.concurrent.locks.Lock;

 import java.util.concurrent.locks.ReadWriteLock;

 import java.util.concurrent.locks.ReentrantReadWriteLock;

 public class ReentrantReadWriteLockCache<K, V>

     implements Cache<K, V>

 {

     private final ReadWriteLock lock = new ReentrantReadWriteLock();

     private final Lock readLock = lock.readLock();

     private final Lock writeLock = lock.writeLock();

     final Map<K, V> cache = new HashMap<K, V>();

     private CacheEntryFactory<K, V> cacheEntryFactory;

     public ReentrantReadWriteLockCache()

     {

     }

     public ReentrantReadWriteLockCache( CacheEntryFactory<K, V> cacheEntryFactory )

     {

         this.cacheEntryFactory = cacheEntryFactory;

     }

     public void clear()

     {

         synchronized ( cache )

         {

             cache.clear();

         }

     }

     public int getSize()

     {

         synchronized ( cache )

         {

             return cache.size();

         }

     }

     public V get( K key )

         throws CacheException

     {

         V v;

         boolean shouldCreate;

         readLock.lock();

         try

         {

             v = cache.get( key );

             shouldCreate = shouldCreate( cacheEntryFactory, v );

         }

         finally

         {

             readLock.unlock();

         }

         if ( shouldCreate )

         {

             try

             {

                 writeLock.lock();

                 v = cache.get( key );

                 if ( !shouldCreate( cacheEntryFactory, v ) )

                 {

                     return v;

                 }

                 v = cacheEntryFactory.create( key );

                 cache.put( key, v );

                 return v;

             }

             finally

             {

                 writeLock.unlock();

             }

         }

         return v;

     }

     protected boolean shouldCreate( CacheEntryFactory<K, V> cacheEntryFactory, V v )

         throws CacheException

     {

         if ( cacheEntryFactory != null )

         {

             if ( v == null )

             {

                 return true;

             }

         }

         return false;

     }

     public V put( K key, V value )

     {

         writeLock.lock();

         try

         {

             cache.put( key, value );

             return value;

         }

         finally

         {

             writeLock.unlock();

         }

     }

 }