replacecomputinglru.java

一宗队列算法

//Source file: E:/工作和学习/工作/硕士论文工作/程序/数据库缓存管理/20040304/src/MemCachePak/ReplaceComputingLRU.java

package MemCachePak;


public class ReplaceComputingLRU implements ReplaceComInterface
{
   public MemCacheInterface theCache;

   public ReplaceComputingLRU()
   {
   }

   /**
   @roseuid 41C63B8A02CE
   */
   public boolean InsertNewObj(String[] RefArray, int ObjSize, int TimeCost)
   {
      WebObj obj = new WebObj();
      obj.SetSourceFileName(RefArray[0]);
      obj.SetCachedFileName(RefArray[1]);
      obj.SetObjRef(RefArray);
      obj.SetCost(TimeCost);
      obj.SetFileSize(ObjSize);
      obj.SetEnterTime();
      theCache.InsertNewObj(obj);
      theCache.InsertNewVector(TimeCost,RefArray[0],RefArray[1],RefArray[0]);
     return true;
   }

   /**
   @roseuid 41C63CBA0128
   */
   public boolean InsertNewObj(String[] RefArray, int ObjSize, int TimeCost, String BeginPoint, boolean SourceOrMedia)
   {
     WebObj obj = new WebObj();
     obj.SetSourceFileName(RefArray[0]);
     obj.SetCachedFileName(RefArray[1]);
     obj.SetObjRef(RefArray);
     obj.SetCost(TimeCost);
     obj.SetFileSize(ObjSize);
     obj.SetEnterTime();
     theCache.InsertNewObj(obj);
     if(SourceOrMedia)
     {
       theCache.InsertNewVector(TimeCost,RefArray[0],RefArray[1],RefArray[0]);
     }
     else
     {
       WebObj MediaObj = theCache.GetCachedObj(RefArray[0],BeginPoint);
       if(MediaObj!=null)
       {
         MediaObj.AddMediaUsedCount();
         MediaObj.SetLastMediaUsedTime();
       }
       theCache.InsertNewVector(TimeCost,BeginPoint,RefArray[1],RefArray[0]);
     }
     return true;
   }

   /**
   @roseuid 41C63D2900CB
   */
   public boolean ReplaceCache()
   {
     //LRU算法的具体策略在这里实现
     //首先判断缓存大小是否超过了门限
     //如果超过了门限，则执行替换算法，返回true
     if(theCache.GetCacheSize()>=Configuration.MAX_SIZE)
     {
       System.out.println("缓存进行了一次替换LRU");
       //theCache.Print();
       WebObj headObj,NowObj,LRUObj;
       LRUObj = null;
       headObj = theCache.GetTheFirstObj();
       long TimeNow=System.currentTimeMillis();
       long LRU = TimeNow;
       while(headObj!=null)
       {
         NowObj = headObj;

         while(NowObj!=null)
         {
           long lastusedtime = 0;
           lastusedtime=NowObj.GetLastUsedTime(1);
           //判断
           if(lastusedtime<LRU)
           {
             LRU = lastusedtime;
             LRUObj = NowObj;
           }
           //转到下一个版本对象
           NowObj = NowObj.NextObjEdition;
         }
         //转到下一个版本对象群
         headObj = headObj.NextObj;
       }
       if(LRUObj!=null)
       {
         //theCache.Print();
         theCache.DeleteObj(LRUObj);

         //同步删除文件

       }
       //theCache.Print();
       return true;
     }
     else
     {
       //如果没有超过门限，则不执行替换算法，返回false
       return false;
     }
   }

   /**
   @roseuid 41C63EA501E4
   */
   protected ReplaceComputingLRU(MemCacheInterface Cache)
   {
     theCache = Cache;
   }
}