source: gsdl/trunk/packages/isis-gdl/CacheMan.h@ 14171

/**********************************************************************
 *
 * CacheMan.h
 * Copyright (C) 2003  UNESCO
 *
 * A component of the Greenstone digital library software
 * from the New Zealand Digital Library Project at the
 * University of Waikato, New Zealand.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *********************************************************************/

#ifndef __CACHEMAN_H__
#define __CACHEMAN_H__


#include "File.h"

class CacheManager
{
private:
    
    CFileBase*         theFile_;
    unsigned           maxblocks_;  // Max # blocks in buff_er
    unsigned           nused_;      // Number being used.
    unsigned           blocksize_;  // Size of a block
    FileSystem::FAU_t* diskAddrs_;  // Its disk address
    unsigned*          useCounts_;  // Use count for the block
    char*              buff_;       // The set of blocks.
    
public:
    
    CacheManager();
    CacheManager(unsigned blocksz, unsigned mxblks);

    ~CacheManager();
    
    void        Create(unsigned blocksz, unsigned mxblks = 10);
    void        Erase();
    
    void        Connect(CFileBase* file);
    void        Disconnect();
    bool        Flush();            // Perform any pending writes.
    void        Invalidate();       // Invalidate the entire cache
    bool        Read (FileSystem::FAU_t locn, void* dat);
    bool        Write(FileSystem::FAU_t locn, void* dat);
    
private:
    
    CacheManager(const CacheManager&);          // Private to insure no copies
    void        operator=(const CacheManager&); // Ditto
    size_t      AgeAndFindSlot(FileSystem::FAU_t);
    bool        Flush(unsigned);
    size_t      GetFreeSlot();
    size_t      LRU() const; // Find least recently used block
};

#endif