content: /**
   * 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.activemq.memory;
  
  import java.util.concurrent.atomic.AtomicLong;
  import org.apache.activemq.usage.MemoryUsage;
  
  /**
   * Simple CacheFilter that increases/decreases usage on a UsageManager as
   * objects are added/removed from the Cache.
   * 
   * 
   */
  public class UsageManagerCacheFilter extends CacheFilter {
  
      private final AtomicLong totalUsage = new AtomicLong(0);
      private final MemoryUsage usage;
  
      public UsageManagerCacheFilter(Cache next, MemoryUsage um) {
          super(next);
          this.usage = um;
      }
  
      public Object put(Object key, Object value) {
          long usageValue = getUsageOfAddedObject(value);
          Object rc = super.put(key, value);
          if (rc != null) {
              usageValue -= getUsageOfRemovedObject(rc);
          }
          totalUsage.addAndGet(usageValue);
          usage.increaseUsage(usageValue);
          return rc;
      }
  
      public Object remove(Object key) {
          Object rc = super.remove(key);
          if (rc != null) {
              long usageValue = getUsageOfRemovedObject(rc);
              totalUsage.addAndGet(-usageValue);
              usage.decreaseUsage(usageValue);
          }
          return rc;
      }
  
      protected long getUsageOfAddedObject(Object value) {
          return 1;
      }
  
      protected long getUsageOfRemovedObject(Object value) {
          return 1;
      }
  
      public void close() {
          usage.decreaseUsage(totalUsage.get());
      }
  }
  