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DjVuFileCache.h

//C-  -*- C++ -*-
//C- -------------------------------------------------------------------
//C- DjVuLibre-3.5
//C- Copyright (c) 2002  Leon Bottou and Yann Le Cun.
//C- Copyright (c) 2001  AT&T
//C-
//C- This software is subject to, and may be distributed under, the
//C- GNU General Public License, either Version 2 of the license,
//C- or (at your option) any later version. The license should have
//C- accompanied the software or you may obtain a copy of the license
//C- from the Free Software Foundation at http://www.fsf.org .
//C-
//C- This program is distributed in the hope that it will be useful,
//C- but WITHOUT ANY WARRANTY; without even the implied warranty of
//C- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//C- GNU General Public License for more details.
//C- 
//C- DjVuLibre-3.5 is derived from the DjVu(r) Reference Library from
//C- Lizardtech Software.  Lizardtech Software has authorized us to
//C- replace the original DjVu(r) Reference Library notice by the following
//C- text (see doc/lizard2002.djvu and doc/lizardtech2007.djvu):
//C-
//C-  ------------------------------------------------------------------
//C- | DjVu (r) Reference Library (v. 3.5)
//C- | Copyright (c) 1999-2001 LizardTech, Inc. All Rights Reserved.
//C- | The DjVu Reference Library is protected by U.S. Pat. No.
//C- | 6,058,214 and patents pending.
//C- |
//C- | This software is subject to, and may be distributed under, the
//C- | GNU General Public License, either Version 2 of the license,
//C- | or (at your option) any later version. The license should have
//C- | accompanied the software or you may obtain a copy of the license
//C- | from the Free Software Foundation at http://www.fsf.org .
//C- |
//C- | The computer code originally released by LizardTech under this
//C- | license and unmodified by other parties is deemed "the LIZARDTECH
//C- | ORIGINAL CODE."  Subject to any third party intellectual property
//C- | claims, LizardTech grants recipient a worldwide, royalty-free, 
//C- | non-exclusive license to make, use, sell, or otherwise dispose of 
//C- | the LIZARDTECH ORIGINAL CODE or of programs derived from the 
//C- | LIZARDTECH ORIGINAL CODE in compliance with the terms of the GNU 
//C- | General Public License.   This grant only confers the right to 
//C- | infringe patent claims underlying the LIZARDTECH ORIGINAL CODE to 
//C- | the extent such infringement is reasonably necessary to enable 
//C- | recipient to make, have made, practice, sell, or otherwise dispose 
//C- | of the LIZARDTECH ORIGINAL CODE (or portions thereof) and not to 
//C- | any greater extent that may be necessary to utilize further 
//C- | modifications or combinations.
//C- |
//C- | The LIZARDTECH ORIGINAL CODE is provided "AS IS" WITHOUT WARRANTY
//C- | OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
//C- | TO ANY WARRANTY OF NON-INFRINGEMENT, OR ANY IMPLIED WARRANTY OF
//C- | MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
//C- +------------------------------------------------------------------
// 
// $Id: DjVuFileCache.h,v 1.9 2007/03/25 20:48:30 leonb Exp $
// $Name: debian_version_3_5_22-6 $

#ifndef _DJVUFILECACHE_H
#define _DJVUFILECACHE_H
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#if NEED_GNUG_PRAGMAS
# pragma interface
#endif


#include "DjVuFile.h"

#ifndef macintosh //MCW can't compile
# ifndef UNDER_CE
#  include <sys/types.h>
#  include <time.h>
# endif 
#else
# include <time.h>
#endif


#ifdef HAVE_NAMESPACES
namespace DJVU {
# ifdef NOT_DEFINED // Just to fool emacs c++ mode
}
#endif
#endif

/** @name DjVuFileCache.h
    Files #"DjVuFileCache.h"# and #"DjVuFileCache.cpp"# implement a simple
    caching mechanism for keeping a given number of \Ref{DjVuFile} instances
    alive. The cache estimates the size of its elements and gets rid of
    the oldest ones when necessary.

    See \Ref{DjVuFileCache} for details.
    
    @memo Simple DjVuFile caching class.
    @author Andrei Erofeev <eaf@geocities.com>
    @version #$Id: DjVuFileCache.h,v 1.9 2007/03/25 20:48:30 leonb Exp $#
*/

//@{

/** #DjVuFileCache# is a simple list of \Ref{DjVuFile} instances. It keeps
    track of the total size of all elements and can get rid of the oldest
    one once the total size becomes over some threshold. Its main purpose
    is to keep the added \Ref{DjVuFile} instances alive until their size
    exceeds some given threshold (set by \Ref{set_maximum_size}() function).
    The user is supposed to use \Ref{DjVuPortcaster::name_to_port}() to
    find a file corresponding to a given name. The cache provides no
    naming services */
#ifdef UNDER_CE
class DjVuFileCache : public GPEnabled
{
protected:
   DjVuFileCache(const int) {}
public:
   static GP<DjVuFileCache> create(const int);
   virtual ~DjVuFileCache(void);
   void del_file(const DjVuFile *) {}
   void add_file(const GP<DjVuFile> &) {}
   void clear(void) {}
   void set_max_size(int) {}
   int get_max_size(void) const {return 0;}
   void enable(bool en) {}
   bool is_enabled(void) const {return false;}
} ;
#else
00128 class DjVuFileCache : public GPEnabled
{
protected:
   DjVuFileCache(const int max_size=5*2*1024*1024);
public:
      /** Constructs the #DjVuFileCache#
        @param max_size Maximum allowed size of the cache in bytes. */
   static GP<DjVuFileCache> create(const int max_size=5*2*1024*1024);

   virtual ~DjVuFileCache(void);

      /** Removes file #file# from the cache */
   void           del_file(const DjVuFile * file);

      /** Adds the given file to the cache. It it's already there, its
        timestamp will be refreshed. */
   void           add_file(const GP<DjVuFile> & file);

      /** Clears the cache. All items will be deleted. */
   void           clear(void);
      /** Sets new maximum size. If the total size of all items in the cache
        is greater than #max_size#, the cache will be deleting the oldest
        items until the size is OK. */
   void           set_max_size(int max_size);

      /** Returns the maximum allowed size of the cache. */
   int            get_max_size(void) const;

      /** Enables or disables the cache. See \Ref{is_enabled}() for details
        @param en - If {\em en} is TRUE, the cache will be enabled.
               Otherwise it will be disabled.
      */
   void           enable(bool en);

      /** Returns #TRUE# if the cache is enabled, #FALSE# otherwise.
        When a cache is disabled, \Ref{add_file}(), and
        \Ref{del_file}() do nothing. But the {\em maximum size} is preserved
        inside the class so that next time the cache is enabled, it will
        be configured the same way. Clearly this "enable/disable" thing is
        for convenience only. One could easily simulate this behavior by
        setting the {\em maximum size} of the cache to #ZERO#. */
   bool           is_enabled(void) const;

public:
   class Item;
   
   class Item : public GPEnabled
      {
      public:
         virtual ~Item(void);
         time_t         get_time(void) const;

         GP<DjVuFile>   get_file(void) const;
         unsigned int   get_size(void) const;
         
         void           refresh(void);

      public:
         GP<DjVuFile>   file;
         time_t         time;
         GPosition            list_pos;
         static int     qsort_func(const void * el1, const void * el2);

         Item(void);
         Item(const GP<DjVuFile> & xfile);
      };

protected:
   GCriticalSection     class_lock;
   
      /** This function is called right after the given file has been added
        to the cache for management. */
   virtual void   file_added(const GP<DjVuFile> & file);
      /** This function is called when the given file is no longer
        managed by the cache. */
   virtual void   file_deleted(const GP<DjVuFile> & file);
      /** This function is called when after the cache decides to get rid
        of the file. */
   virtual void   file_cleared(const GP<DjVuFile> & file);

   GPList<Item>   get_items(void);
private:
   GPList<Item>   list;
   bool           enabled;
   int            max_size;
   int            cur_size;

   int            calculate_size(void);
   void           clear_to_size(int size);
};



//@}
   
inline
DjVuFileCache::Item::Item(void) : time(::time(0)) {};

inline
DjVuFileCache::Item::Item(const GP<DjVuFile> & xfile) :
      file(xfile), time(::time(0)) {}

inline
DjVuFileCache::Item::~Item(void) {}

inline GP<DjVuFile>
DjVuFileCache::Item::get_file(void) const
{
   return file;
}

inline unsigned int
DjVuFileCache::Item::get_size(void) const
{
   return file->get_memory_usage();
}

inline time_t
DjVuFileCache::Item::get_time(void) const
{
   return time;
}

inline void
DjVuFileCache::Item::refresh(void)
{
   time=::time(0);
}

inline
DjVuFileCache::DjVuFileCache(const int xmax_size) :
      enabled(true), max_size(xmax_size), cur_size(0) {}

inline void
00262 DjVuFileCache::clear(void)
{
   clear_to_size(0);
}

inline bool
00268 DjVuFileCache::is_enabled(void) const
{
   return enabled;
}

inline int
00274 DjVuFileCache::get_max_size(void) const
{
   return max_size;
}

#endif

inline GP<DjVuFileCache>
00282 DjVuFileCache::create(const int max_size)
{
  return new DjVuFileCache(max_size);
}


#ifdef HAVE_NAMESPACES
}
# ifndef NOT_USING_DJVU_NAMESPACE
using namespace DJVU;
# endif
#endif
#endif

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