gistfilecache.cpp

此文件包含了在linux下实现tpr-tree索引的源代码

//--------------------------------------------------------------------
//        GiSTfileCache.cpp
//        -----------------
//
//        GiST - Generalized Search Tree 
//        June 2001 release, Aalborg University
//        
//        This file is a revised version of a part of the original 
//        libGiST release (version  0.9beta1)     
//        Copyright (c) 1996, Regents of the University of California
//

#include "GiSTfileCache.h"
#include <string.h>

//--------------------------------------------------------------------
void GiSTfileCache::Reset()
{
   if (buffer) delete buffer;
   buffer = new char[DEF_FILECACHE_SIZE * PageSize()];
   assert (buffer);
   lenPageNums  = 0;
   for (int i = 0; i < DEF_FILECACHE_SIZE2; i++) lookUp[i] = -1;
   GiSTfile::Reset();
}

//--------------------------------------------------------------------
void GiSTfileCache::Create(const char *filename)
{
   Reset();
   GiSTfile::Create(filename);
}

//--------------------------------------------------------------------
void GiSTfileCache::Open  (const char *filename)
{
   Reset();
   GiSTfile::Open(filename);
}

//--------------------------------------------------------------------
void GiSTfileCache::Close ()
{
   for (int i = 0; i < lenPageNums; i++) 
      if (dirty[i]) GiSTfile::Write(pageNums[i], buffer + i * PageSize());
   GiSTfile::Close();      
}

//--------------------------------------------------------------------
void GiSTfileCache::Read    (GiSTpage page, char *buf)
{
   assert(page < DEF_FILECACHE_SIZE2);
   if (lookUp[page] != -1) 
   {
      memcpy(buf, buffer + lookUp[page] * PageSize(), PageSize());
      return;
   }
   GiSTfile::Read(page, buf);
   int ns = GetNewSlot();
   lookUp[page] = ns;
   pageNums[ns] = page;
   dirty[ns]    = 0;
   memcpy(buffer + ns * PageSize(), buf, PageSize());
}

//--------------------------------------------------------------------
void GiSTfileCache::Write   (GiSTpage page, const char *buf)
{
   assert(page < DEF_FILECACHE_SIZE2);
   if (lookUp[page] != -1) 
   {
      memcpy(buffer + lookUp[page] * PageSize(), buf, PageSize());
      dirty[lookUp[page]] = 1;
      return;
   }
   int ns = GetNewSlot();
   lookUp[page] = ns;
   pageNums[ns] = page;
   dirty[ns]    = 1;
   memcpy(buffer + ns * PageSize(), buf, PageSize());   
}

//--------------------------------------------------------------------
int GiSTfileCache::GetNewSlot()
{
   if (lenPageNums == DEF_FILECACHE_SIZE) 
   {
      if (dirty[lenPageNums - 1]) 
         GiSTfile::Write(pageNums[lenPageNums - 1], 
                         buffer + (lenPageNums - 1) * PageSize());
      lookUp[pageNums[lenPageNums - 1]] = -1;
      return lenPageNums - 1; 
   }
   return lenPageNums++;
}