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From co...@apache.org
Subject cvs commit: jakarta-avalon-excalibur/src/scratchpad/org/apache/avalon/excalibur/cache/policy TimeMapLRUPolicy.java
Date Mon, 28 Jan 2002 07:29:47 GMT
colus       02/01/27 23:29:47

  Added:       src/scratchpad/org/apache/avalon/excalibur/cache/policy
                        TimeMapLRUPolicy.java
  Log:
  TimeMapLRUCache replacement policy.
  On large cache this impl should be faster than current LRUPolicy.
  
  Submitted By: Alexis Agahi <alag@users.sourceforge.net>
  
  Revision  Changes    Path
  1.1                  jakarta-avalon-excalibur/src/scratchpad/org/apache/avalon/excalibur/cache/policy/TimeMapLRUPolicy.java
  
  Index: TimeMapLRUPolicy.java
  ===================================================================
  /*
   * Copyright (C) The Apache Software Foundation. All rights reserved.
   *
   * This software is published under the terms of the Apache Software License
   * version 1.1, a copy of which has been included  with this distribution in
   * the LICENSE.txt file.
   */
  package org.apache.avalon.excalibur.cache.policy;
  
  import java.util.HashMap;
  import java.util.TreeMap;
  import org.apache.avalon.excalibur.cache.ReplacementPolicy;
  
  /**
   * TimeMapLRU(Least Recently Used) replacement policy.
   * Use a TreeMap with logical time to perform LRU <code>selectVictim</code>
operations.
   * On large cache this implementation should be really faster (since it uses a
   * log(n) treemap plus an hashmap) than the current LRU implem that is working with a List.
   *
   * @author <a href="alag@users.sourceforge.net">Alexis Agahi</a>
   */
  public class TimeMapLRUPolicy
      implements ReplacementPolicy
  {
  
      protected TreeMap m_timeToKeyMap;
      protected HashMap m_keyToTimeMap;
  
      private long m_time;
      private Object m_lock;
  
      public TimeMapLRUPolicy()
      {
          m_timeToKeyMap = new TreeMap();
          m_keyToTimeMap = new HashMap();
          m_time = 0;
          m_lock = new Object();
      }
  
      public void hit( final Object key )
      {
          remove( key );
          add( key );
      }
  
      public void add( final Object key )
      {
          Long time = getTime();
          m_timeToKeyMap.put( time, key );
          m_keyToTimeMap.put( key, time );
      }
  
      public void remove( final Object key )
      {
          Long time = (Long)m_keyToTimeMap.remove( key );
          m_timeToKeyMap.remove( time );
      }
  
      public Object selectVictim()
      {
          Object time = m_timeToKeyMap.firstKey();
          Object key = m_timeToKeyMap.get( time );
          return key;
      }
  
      private Long getTime()
      {
          synchronized ( m_lock )
          {
              return new Long( m_time++ );
          }
      }
  }
  
  
  

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