# cache.hpp

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    00001 /*********************************************************************/
    00002 // dar - disk archive - a backup/restoration program
    00003 // Copyright (C) 2002-2052 Denis Corbin
    00004 //
    00005 // This program is free software; you can redistribute it and/or
    00006 // modify it under the terms of the GNU General Public License
    00007 // as published by the Free Software Foundation; either version 2
    00008 // of the License, or (at your option) any later version.
    00009 //
    00010 // This program is distributed in the hope that it will be useful,
    00011 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00012 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00013 // GNU General Public License for more details.
    00014 //
    00015 // You should have received a copy of the GNU General Public License
    00016 // along with this program; if not, write to the Free Software
    00017 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
    00018 //
    00019 // to contact the author : dar.linux@free.fr
    00020 /*********************************************************************/
    00021 // $Id: cache.hpp,v 1.10.2.2 2009/04/07 08:45:29 edrusb Rel $
    00022 //
    00023 /*********************************************************************/
    00024
    00028
    00029 #ifndef CACHE_HPP
    00030 #define CACHE_HPP
    00031
    00032 #include "../my_config.h"
    00033 #include "infinint.hpp"
    00034 #include "generic_file.hpp"
    00035
    00036 namespace libdar
    00037 {
    00039
    00050     class cache : public generic_file
    00051     {
    00052     public:
    00053         cache(user_interaction & dialog,
    00054               generic_file & hidden,
    00055               U_I initial_size = 10240,
    00056               U_I unused_read_ratio = 10, U_I observation_read_number = 100, U_I max_size_hit_read_ratio = 50,
    00057               U_I unused_write_ratio = 10, U_I observation_write_number = 100, U_I max_size_hit_write_ratio = 50);
    00058             // *** hidden: is the file to cache, it is never deleted by the cache object,
    00059             // *** intial_size: is the initial size of the cache for reading (read this amount of data at a time)
    00060             // unused_read_ratio: is the ratio of cached data effectively asked for reading below which the cache size is divided by two
    00061             //   in other words, if during observation_read_number fullfilment of the cache, less than unused_read_ratio percent of data has been
    00062             //   effectively asked for reading, then the cache size is divided by two
    00063             // *** max_size_hit_read_ratio: is the ratio above which the cache size is doubled. In other words, if during observation_read_number
    00064             //   times of cache fullfilment, more than max_size_hit_read_ratio percent time all the cached data has been asked for reading
    00065             //   the cache size is doubled.
    00066             // to have fixed size read caching, you can set unused_read_ratio to zero and max_size_hit_read_ratio to 101 or above.
    00067             // *** unused_write_ratio: cache is flushed before being fullfilled if a seek operation has been asked. If after observation_write_number
    00068             //   of cache flushing, less than unused_write_ratio percent of the time the cache was full, its size is divided by 2
    00069             // *** max_size_hit_write_ratio: if after observation_write_number of cache flushing, max_size_hit_write_ratio percent of the time
    00070             // the cache was fulled, its size get doubled.
    00071             // to have a fixed size write caching , you can set unused_write_ratio to zero and max_size_hit_write_ratio to 101 or above
    00072         ~cache() { flush_write(); };
    00073
    00074
    00075             // inherited from generic_file
    00076         bool skip(const infinint & pos) { flush_write(); clear_read(); return ref->skip(pos); };
    00077         bool skip_to_eof() { flush_write(); clear_read(); return ref->skip_to_eof(); };
    00078         bool skip_relative(S_I x) { flush_write(); clear_read(); return ref->skip_relative(x); };
    00079         infinint get_position() { return ref->get_position(); };
    00080
    00081     protected:
    00082             // inherited from generic_file
    00083         S_I inherited_read(char *a, size_t size);
    00084         S_I inherited_write(const char *a, size_t size);
    00085
    00086     private:
    00087         struct buf
    00088         {
    00089             char *buffer;
    00090             U_I size; // allocated size
    00091             U_I next; // next to read or next place to write to
    00092             U_I last; // first to not read in the cache
    00093
    00094             buf() { buffer = NULL; size = next = last = 0; };
    00095             ~buf() { if(buffer != NULL) delete [] buffer; };
    00096         };
    00097
    00098         generic_file *ref;
    00099
    00100         struct buf buffer_cache;
    00101         bool read_mode; // true if in read mode, false if in write mode
    00102
    00103         U_I read_obs;
    00104         U_I read_unused_rate;
    00105         U_I read_overused_rate;
    00106
    00107         U_I write_obs;
    00108         U_I write_unused_rate;
    00109         U_I write_overused_rate;
    00110
    00111         U_I stat_read_unused;
    00112         U_I stat_read_overused;
    00113         U_I stat_read_counter;
    00114
    00115         U_I stat_write_overused;
    00116         U_I stat_write_counter;
    00117
    00118         void flush_write();
    00119         void fulfill_read();
    00120         void clear_read() { if(read_mode) { buffer_cache.next = buffer_cache.last = 0; } };
    00121     };
    00122
    00123 } // end of namespace
    00124
    00125 #endif
    00126