src/Cache.h

   1 //vim: expandtab:shiftwidth=4:fileencoding=utf-8 :
   2
   3 /* Copyright ® 2008-2009 Fulvio Satta
   4
   5    If you want contact me, send an email to Yota_VGA@users.sf.net
   6
   7    This file is part of Biscotto
   8
   9    Biscotto is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    Biscotto is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  22 */
  23
  24 #ifndef CACHE_H
  25 #define CACHE_H
  26
  27 #include <set>
  28 #include <map>
  29 #include <boost/pool/pool_alloc.hpp>
  30 #include <boost/thread.hpp>
  31
  32 class CacheObject;
  33
  34 /* Cache system
  35  *
  36  * The cache system work correctly only if the ids of the protected objects
  37  * are all in the unsigned long int intervall size and if the ++ overflow of
  38  * the unsigned long int give 0.
  39  * This is sure in all the pratical cases.
  40  */
  41 class Cache
  42 {
  43     friend class CacheObject;
  44
  45     protected:
  46         /* Functor for the monitor of the cache */
  47         class Monitor
  48         {
  49             public:
  50                 Monitor() {}
  51
  52             void operator()();
  53         };
  54
  55         /* Internal rappresentation of the cache */
  56         static Cache m_cache;
  57
  58         /* Syncronization variables */
  59         mutable boost::mutex mutex;
  60         boost::condition_variable command;
  61         boost::condition_variable_any waitdelfirst;
  62
  63         /* State of the cache */
  64         unsigned long int position;
  65         unsigned long int size;
  66         unsigned long int first;
  67         bool delfirst;
  68
  69         /* Maximum size of the cache, not strictly followed */
  70         unsigned long int max;
  71
  72         /* Functor for the map order */
  73         struct circular_order
  74         {
  75             inline bool operator()(unsigned long int a, unsigned long int b)
  76             {
  77                 if (a < cache().position and b >= cache().position)
  78                     return true;
  79
  80                 return a < b;
  81             }
  82         };
  83
  84         /* Order of the objects */
  85         std::map<unsigned long int, CacheObject *,
  86                  circular_order,
  87                  boost::pool_allocator<
  88                      std::pair<unsigned long int, CacheObject *> > >
  89             order;
  90
  91         /* Object collection */
  92         std::set<CacheObject *, std::less<CacheObject *>,
  93                  boost::pool_allocator<CacheObject *> >
  94             objects;
  95
  96         /* Internal costructor, is a singleton */
  97         Cache();
  98
  99         /* Add an object in the cache */
 100         void add(CacheObject &object);
 101
 102         /* Delete an object in the cache */
 103         void del(CacheObject &object);
 104
 105         /* Resize an object */
 106         void resize(long int delta);
 107
 108         /* Call this if an object is used */
 109         void use(CacheObject &object);
 110
 111     public:
 112         /* Return the cache (singleton) */
 113         static inline Cache &cache()
 114         {
 115             return m_cache;
 116         }
 117
 118         /* Set the cache limit (not strictly) */
 119         void setLimit(unsigned long int imit);
 120
 121         /* Get the cache limit (not strictly) */
 122         unsigned long int limit() const;
 123
 124         CacheObject *readPointer(CacheObject **ptr) const;
 125 };
 126
 127 #include "CacheObject.h"
 128
 129 #endif