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real_infinint.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 : http://dar.linux.free.fr/email.html
00020 /*********************************************************************/
00021 // $Id$
00022 //
00023 /*********************************************************************/
00024 
00031 
00032 #ifndef REAL_INFININT_HPP
00033 #define REAL_INFININT_HPP
00034 
00035 #include "../my_config.h"
00036 
00037 extern "C"
00038 {
00039 #if HAVE_SYS_TYPES_H
00040 #include <sys/types.h>
00041 #endif
00042 } // end extern "C"
00043 
00044 #include <typeinfo>
00045 #include "storage.hpp"
00046 #include "integers.hpp"
00047 #include "int_tools.hpp"
00048 
00049 #define ZEROED_SIZE 50
00050 
00051 namespace libdar
00052 {
00053     class generic_file;
00054     class user_interaction;
00055 
00057 
00060     class infinint
00061     {
00062     public :
00063 
00064 #if SIZEOF_OFF_T > SIZEOF_TIME_T
00065 #if SIZEOF_OFF_T > SIZEOF_SIZE_T
00066         infinint(off_t a = 0)
00067         { infinint_from(a); };
00068 #else
00069         infinint(size_t a = 0)
00070         { infinint_from(a); };
00071 #endif
00072 #else
00073 #if SIZEOF_TIME_T > SIZEOF_SIZE_T
00074         infinint(time_t a = 0)
00075         { infinint_from(a); };
00076 #else
00077         infinint(size_t a = 0)
00078         { infinint_from(a); };
00079 #endif
00080 #endif
00081 
00082         infinint(const infinint & ref)
00083         { copy_from(ref); }
00084 
00085             // read an infinint from a file
00086         infinint(user_interaction & dialog, S_I fd);
00087         infinint(generic_file & x);
00088 
00089         ~infinint()
00090         { detruit(); };
00091 
00092         const infinint & operator = (const infinint & ref)
00093         { detruit(); copy_from(ref); return *this; };
00094 
00095         void dump(user_interaction & dialog, int fd) const; // write byte sequence to file
00096         void dump(generic_file &x) const; // write byte sequence to file
00097         void read(generic_file &f) { detruit(); build_from_file(f); };
00098 
00099         infinint & operator += (const infinint & ref);
00100         infinint & operator -= (const infinint & ref);
00101         infinint & operator *= (unsigned char arg);
00102         infinint & operator *= (const infinint & ref);
00103         template <class T> infinint power(const T & exponent) const;
00104         inline infinint & operator /= (const infinint & ref);
00105         inline infinint & operator %= (const infinint & ref);
00106         infinint & operator &= (const infinint & ref);
00107         infinint & operator |= (const infinint & ref);
00108         infinint & operator ^= (const infinint & ref);
00109         infinint & operator >>= (U_32 bit);
00110         infinint & operator >>= (infinint bit);
00111         infinint & operator <<= (U_32 bit);
00112         infinint & operator <<= (infinint bit);
00113         infinint operator ++(int a)
00114         { infinint ret = *this; ++(*this); return ret; };
00115         infinint operator --(int a)
00116         { infinint ret = *this; --(*this); return ret; };
00117         infinint & operator ++()
00118         { return *this += 1; };
00119         infinint & operator --()
00120         { return *this -= 1; };
00121 
00122         U_32 operator % (U_32 arg) const
00123         { return modulo(arg); };
00124 
00125             // increment the argument up to a legal value for its storage type and decrement the object in consequence
00126             // note that the initial value of the argument is not ignored !
00127             // when the object is null the value of the argument is unchanged
00128         template <class T>void unstack(T &v)
00129         { infinint_unstack_to(v); }
00130 
00131         infinint get_storage_size() const { return field->size(); };
00132             // it returns number of byte of information necessary to store the integer
00133 
00134         unsigned char operator [] (const infinint & position) const;
00135             // return in big endian order the information byte storing the integer
00136 
00137         friend bool operator < (const infinint &, const infinint &);
00138         friend bool operator == (const infinint &, const infinint &);
00139         friend bool operator > (const infinint &, const infinint &);
00140         friend bool operator <= (const infinint &, const infinint &);
00141         friend bool operator != (const infinint &, const infinint &);
00142         friend bool operator >= (const infinint &, const infinint &);
00143         friend void euclide(infinint a, const infinint &b, infinint &q, infinint &r);
00144 
00145         static bool is_system_big_endian();
00146 
00147 #ifdef LIBDAR_SPECIAL_ALLOC
00148         USE_SPECIAL_ALLOC(infinint);
00149 #endif
00150     private :
00151         static const int TG = 4;
00152 
00153         enum endian { big_endian, little_endian, not_initialized };
00154         typedef unsigned char group[TG];
00155 
00156         storage *field;
00157 
00158         bool is_valid() const;
00159         void build_from_file(generic_file & x);
00160         void reduce(); // put the object in canonical form : no leading byte equal to zero
00161         void copy_from(const infinint & ref);
00162         void detruit();
00163         void make_at_least_as_wider_as(const infinint & ref);
00164         template <class T> void infinint_from(T a);
00165         template <class T> T max_val_of(T x);
00166         template <class T> void infinint_unstack_to(T &a);
00167         template <class T> T modulo(T arg) const;
00168         signed int difference(const infinint & b) const; // gives the sign of (*this - arg) but only the sign !
00169 
00171             // static statments
00172             //
00173         static endian used_endian;
00174         static U_8 zeroed_field[ZEROED_SIZE];
00175         static void setup_endian();
00176     };
00177 
00178 
00179 #define OPERATOR(OP) inline bool operator OP (const infinint &a, const infinint &b) \
00180     {                                                                   \
00181             return a.difference(b) OP 0;                                \
00182     }
00183 
00184     OPERATOR(<)
00185     OPERATOR(>)
00186     OPERATOR(<=)
00187     OPERATOR(>=)
00188     OPERATOR(==)
00189     OPERATOR(!=)
00190 
00191     infinint operator + (const infinint &, const infinint &);
00192     infinint operator - (const infinint &, const infinint &);
00193     infinint operator * (const infinint &, const infinint &);
00194     infinint operator * (const infinint &, const unsigned char);
00195     infinint operator * (const unsigned char, const infinint &);
00196     infinint operator / (const infinint &, const infinint &);
00197     infinint operator % (const infinint &, const infinint &);
00198     infinint operator & (const infinint & a, const infinint & bit);
00199     infinint operator | (const infinint & a, const infinint & bit);
00200     infinint operator ^ (const infinint & a, const infinint & bit);
00201     infinint operator >> (const infinint & a, U_32 bit);
00202     infinint operator >> (const infinint & a, const infinint & bit);
00203     infinint operator << (const infinint & a, U_32 bit);
00204     infinint operator << (const infinint & a, const infinint & bit);
00205     void euclide(infinint a, const infinint &b, infinint &q, infinint &r);
00206     template <class T> inline void euclide(T a, T b, T & q, T &r)
00207     {
00208         q = a/b; r = a%b;
00209     }
00210 
00211     inline infinint & infinint::operator /= (const infinint & ref)
00212     {
00213         *this = *this / ref;
00214         return *this;
00215     }
00216 
00217     inline infinint & infinint::operator %= (const infinint & ref)
00218     {
00219         *this = *this % ref;
00220         return *this;
00221     }
00222 
00223 
00227 
00228     template <class T> infinint infinint::power(const T & exponent) const
00229     {
00230         infinint ret = 1;
00231         for(T count = 0; count < exponent; ++count)
00232             ret *= *this;
00233 
00234         return ret;
00235     }
00236 
00237     template <class T> T infinint::modulo(T arg) const
00238     {
00239         infinint tmp = *this % infinint(arg);
00240         T ret = 0;
00241         unsigned char *debut = (unsigned char *)(&ret);
00242         unsigned char *ptr = debut + sizeof(T) - 1;
00243         storage::iterator it = tmp.field->rbegin();
00244 
00245         while(it != tmp.field->rend() && ptr >= debut)
00246         {
00247             *ptr = *it;
00248             --ptr;
00249             --it;
00250         }
00251 
00252             // checking for overflow (should never occur, but for sanity, we check it anyway)
00253 
00254         while(it != tmp.field->rend()) // field may not be reduced (some zeros are leading)
00255         {
00256             if(*it != 0)
00257                 throw SRC_BUG; // could not put all the data in the returned value !
00258             --it;
00259         }
00260 
00261         if(used_endian == little_endian)
00262             int_tools_swap_bytes(debut, sizeof(T));
00263 
00264         return ret;
00265     }
00266 
00267 
00268     template <class T> void infinint::infinint_from(T a)
00269     {
00270         U_I size = sizeof(a);
00271         S_I direction = +1;
00272         unsigned char *ptr, *fin;
00273 
00274         if(used_endian == not_initialized)
00275             setup_endian();
00276 
00277         if(used_endian == little_endian)
00278         {
00279             direction = -1;
00280             ptr = (unsigned char *)(&a) + (size - 1);
00281             fin = (unsigned char *)(&a) - 1;
00282         }
00283         else
00284         {
00285             direction = +1;
00286             ptr = (unsigned char *)(&a);
00287             fin = (unsigned char *)(&a) + size;
00288         }
00289 
00290         while(ptr != fin && *ptr == 0)
00291         {
00292             ptr += direction;
00293             --size;
00294         }
00295 
00296         if(size == 0)
00297         {
00298             size = 1;
00299             ptr -= direction;
00300         }
00301 
00302         field = new storage(size);
00303         if(field != NULL)
00304         {
00305             storage::iterator it = field->begin();
00306 
00307             while(ptr != fin)
00308             {
00309                 *it = *ptr;
00310                 ++it;
00311                 ptr += direction;
00312             }
00313             if(it != field->end())
00314                 throw SRC_BUG; // size mismatch in this algorithm
00315         }
00316         else
00317             throw Ememory("template infinint::infinint_from");
00318     }
00319 
00320     template <class T> T infinint::max_val_of(T x)
00321     {
00322         x = 0;
00323         x = ~x;
00324 
00325         if(x <= 0) // T is a signed integer type. Note that it should be "x < 0" but to avoid compiler warning when T is unsigned it does not hurt having "x <= 0" here
00326         {
00327             x = 1;
00328             x = int_tools_rotate_right_one_bit(x);
00329             x = ~x;
00330         }
00331 
00332         return x;
00333     }
00334 
00335     template <class T> void infinint::infinint_unstack_to(T &a)
00336     {
00337             // T is supposed to be an unsigned "integer"
00338             // (ie.: sizeof() returns the width of the storage bit field  and no sign bit is present)
00339             // Note : static here avoids the recalculation of max_T at each call
00340         static const T max_T = max_val_of(a);
00341         infinint step = max_T - a;
00342 
00343         if(*this < step)
00344         {
00345             T transfert = 0;
00346             unsigned char *debut = (unsigned char *)&transfert;
00347             unsigned char *ptr = debut + sizeof(transfert) - 1;
00348             storage::iterator it = field->rbegin();
00349 
00350             while(ptr >= debut && it != field->rend())
00351             {
00352                 *ptr = *it;
00353                 --ptr;
00354                 --it;
00355             }
00356 
00357             if(used_endian == little_endian)
00358                 int_tools_swap_bytes(debut, sizeof(transfert));
00359             a += transfert;
00360             *this -= *this;
00361         }
00362         else
00363         {
00364             *this -= step;
00365             a = max_T;
00366         }
00367     }
00368 
00369 } // end of namespace
00370 
00371 #endif
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