chiark - git - mdw - catacomb/blob - math/mpint.h

   1 /* -*-c-*-
   2  *
   3  * Conversion between MPs and standard C integers
   4  *
   5  * (c) 1999 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef CATACOMB_MPINT_H
  29 #define CATACOMB_MPINT_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <limits.h>
  38
  39 #ifndef CATACOMB_MP_H
  40 #  include "mp.h"
  41 #endif
  42
  43 /*----- Generic translation macros ----------------------------------------*/
  44
  45 /* --- @MP_FROMINT@ --- *
  46  *
  47  * Arguments:   @d@ = destination multiprecision integer
  48  *              @type@ = type of integer which @i@ is
  49  *              @i@ = a standard C integer
  50  *
  51  * Use:         Stores the value of @i@ in @d@.  This macro is actually
  52  *              rather subtle in places.  Be careful what you change.
  53  */
  54
  55 #define MP_FROMINT(d, type, i) do {                                     \
  56   type _i = (i);                                                        \
  57   size_t _o = 0;                                                        \
  58   mp *_d = (d);                                                         \
  59   size_t _sz = 4;                                                       \
  60                                                                         \
  61   MP_DEST(_d, _sz, 0);                                                  \
  62   _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
  63                                                                         \
  64   if (_i >= 0) {                                                        \
  65     while (_i) {                                                        \
  66       if (_o == _sz) {                                                  \
  67         _sz <<= 1;                                                      \
  68         MP_ENSURE(_d, _sz);                                             \
  69       }                                                                 \
  70       _d->v[_o++] = MPW(_i);                                            \
  71       if (_i <= MPW_MAX)                                                \
  72         break;                                                          \
  73       else                                                              \
  74         _i /= (type)MPW_MAX + 1;                                        \
  75     }                                                                   \
  76   } else {                                                              \
  77     _d->f |= MP_NEG;                                                    \
  78     while (_i) {                                                        \
  79       if (_o == _sz) {                                                  \
  80         _sz <<= 1;                                                      \
  81         MP_ENSURE(_d, _sz);                                             \
  82       }                                                                 \
  83       _d->v[_o++] = MPW(-_i);                                           \
  84       if (_i >= -MPW_MAX)                                               \
  85         break;                                                          \
  86       else                                                              \
  87         _i /= (type)MPW_MAX + 1;                                        \
  88     }                                                                   \
  89   }                                                                     \
  90                                                                         \
  91   _d->vl = _d->v + _o;                                                  \
  92   (d) = _d;                                                             \
  93 } while (0)
  94
  95 /* --- @MP_TOINT@ --- *
  96  *
  97  * Arguments:   @m@ = a multiprecision integer
  98  *              @type@ = the type of @i@
  99  *              @max@ = the largest value @i@ can represent
 100  *              @i@ = an integer variable
 101  *
 102  * Use:         Stores the value of a multiprecision integer in a standard C
 103  *              integer.  If the value won't fit, the behaviour is determined
 104  *              by the type of @i@: if @i@ is unsigned, the value of the
 105  *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 106  *              signed, the behaviour is undefined.
 107  *
 108  *              If you don't want to be bitten by these sorts of things, keep
 109  *              copies of @INT_MAX@ or whatever is appropriate in
 110  *              multiprecision form and compare before conversion.
 111  */
 112
 113 #define MP_TOINT(m, type, max, i) do {                                  \
 114   type _i = 0;                                                          \
 115   type _max = (max);                                                    \
 116   unsigned _s = 0;                                                      \
 117   const mp *_m = (m);                                                   \
 118   const mpw *_v = _m->v, *_vl = _m->vl;                                 \
 119                                                                         \
 120   /* --- Do all the arithmetic in negative numbers --- */               \
 121                                                                         \
 122   while (_v < _vl && _max > 0) {                                        \
 123     _i -= *_v << _s;                                                    \
 124     _s += MPW_BITS;                                                     \
 125     _v++;                                                               \
 126     _max /= (mpd)MPW_MAX + 1;                                           \
 127   }                                                                     \
 128   if (!MP_NEGP(_m))                                                     \
 129     _i = -_i;                                                           \
 130   (i) = _i;                                                             \
 131 } while (0)
 132
 133 /*----- Functions provided ------------------------------------------------*/
 134
 135 /* --- @mp_fromINT@ --- *
 136  *
 137  * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 138  *              @INT i@ = standard C integer to convert
 139  *
 140  * Returns:     The resulting multiprecision integer.
 141  *
 142  * Use:         Converts a standard C integer to a multiprecision integer.
 143  */
 144
 145 #define mp_fromINT(name, type)                                          \
 146   extern mp *mp_from##name(mp */*d*/, type /*i*/)
 147
 148 mp_fromINT(short, short);
 149 mp_fromINT(ushort, unsigned short);
 150 mp_fromINT(int, int);
 151 mp_fromINT(uint, unsigned);
 152 mp_fromINT(uint32, uint32);
 153 mp_fromINT(long, long);
 154 mp_fromINT(ulong, unsigned long);
 155
 156 #undef mp_fromINT
 157
 158 /* --- @mp_toINT@ --- *
 159  *
 160  * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 161  *
 162  * Returns:     The value of the integer @m@ as a C integer.
 163  *
 164  * Use:         Converts a multiprecision integer to a standard C integer.
 165  *              If the value of the multiprecision integer cannot be
 166  *              represented in the return type, and the return type is
 167  *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 168  *              type is signed, the behaviour is undefined.
 169  */
 170
 171 #define mp_toINT(name, type)                                            \
 172   extern type mp_to##name(const mp */*m*/)
 173
 174 mp_toINT(short, short);
 175 mp_toINT(ushort, unsigned short);
 176 mp_toINT(int, int);
 177 mp_toINT(uint, unsigned);
 178 mp_toINT(uint32, uint32);
 179 mp_toINT(long, long);
 180 mp_toINT(ulong, unsigned long);
 181
 182 #undef mp_toINT
 183
 184 /*----- That's all, folks -------------------------------------------------*/
 185
 186 #ifdef __cplusplus
 187   }
 188 #endif
 189
 190 #endif