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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Conversion between MPs and standard C integers
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 #ifndef CATACOMB_MPINT_H
  31 #define CATACOMB_MPINT_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #include <limits.h>
  40
  41 #ifndef CATACOMB_MP_H
  42 #  include "mp.h"
  43 #endif
  44
  45 /*----- Generic translation macros ----------------------------------------*/
  46
  47 /* --- @MP_FROMINT@ --- *
  48  *
  49  * Arguments:   @d@ = destination multiprecision integer
  50  *              @type@ = type of integer which @i@ is
  51  *              @i@ = a standard C integer
  52  *
  53  * Use:         Stores the value of @i@ in @d@.  This macro is actually
  54  *              rather subtle in places.  Be careful what you change.
  55  */
  56
  57 #define MP_FROMINT(d, type, i) do {                                     \
  58   type _i = (i);                                                        \
  59   size_t _o = 0;                                                        \
  60   mp *_d = (d);                                                         \
  61   size_t _sz = 4;                                                       \
  62                                                                         \
  63   MP_DEST(_d, _sz, 0);                                                  \
  64   _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
  65                                                                         \
  66   if (_i >= 0) {                                                        \
  67     while (_i) {                                                        \
  68       if (_o == _sz) {                                                  \
  69         _sz <<= 1;                                                      \
  70         MP_ENSURE(_d, _sz);                                             \
  71       }                                                                 \
  72       _d->v[_o++] = MPW(_i);                                            \
  73       if (_i < MPW_MAX)                                                 \
  74         break;                                                          \
  75       else                                                              \
  76         _i /= (type)MPW_MAX + 1;                                        \
  77     }                                                                   \
  78   } else {                                                              \
  79     _d->f |= MP_NEG;                                                    \
  80     while (_i) {                                                        \
  81       if (_o == _sz) {                                                  \
  82         _sz <<= 1;                                                      \
  83         MP_ENSURE(_d, _sz);                                             \
  84       }                                                                 \
  85       _d->v[_o++] = MPW(-_i);                                           \
  86       if (_i > -MPW_MAX)                                                \
  87         break;                                                          \
  88       else                                                              \
  89         _i /= (type)MPW_MAX + 1;                                        \
  90     }                                                                   \
  91   }                                                                     \
  92                                                                         \
  93   _d->vl = _d->v + _o;                                                  \
  94   (d) = _d;                                                             \
  95 } while (0)
  96
  97 /* --- @MP_TOINT@ --- *
  98  *
  99  * Arguments:   @m@ = a multiprecision integer
 100  *              @type@ = the type of @i@
 101  *              @max@ = the largest value @i@ can represent
 102  *              @i@ = an integer variable
 103  *
 104  * Use:         Stores the value of a multiprecision integer in a standard C
 105  *              integer.  If the value won't fit, the behaviour is determined
 106  *              by the type of @i@: if @i@ is unsigned, the value of the
 107  *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 108  *              signed, the behaviour is undefined.
 109  *
 110  *              If you don't want to be bitten by these sorts of things, keep
 111  *              copies of @INT_MAX@ or whatever is appropriate in
 112  *              multiprecision form and compare before conversion.
 113  */
 114
 115 #define MP_TOINT(m, type, max, i) do {                                  \
 116   type _i = 0;                                                          \
 117   type _max = (max);                                                    \
 118   unsigned _s = 0;                                                      \
 119   const mp *_m = (m);                                                   \
 120   const mpw *_v = _m->v, *_vl = _m->vl;                                 \
 121                                                                         \
 122   /* --- Do all the arithmetic in negative numbers --- */               \
 123                                                                         \
 124   while (_v < _vl && _max > 0) {                                        \
 125     _i -= *_v << _s;                                                    \
 126     _s += MPW_BITS;                                                     \
 127     _v++;                                                               \
 128     _max /= (mpd)MPW_MAX + 1;                                           \
 129   }                                                                     \
 130   if (!MP_NEGP(_m))                                                     \
 131     _i = -_i;                                                           \
 132   (i) = _i;                                                             \
 133 } while (0)
 134
 135 /*----- Functions provided ------------------------------------------------*/
 136
 137 /* --- @mp_fromINT@ --- *
 138  *
 139  * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 140  *              @INT i@ = standard C integer to convert
 141  *
 142  * Returns:     The resulting multiprecision integer.
 143  *
 144  * Use:         Converts a standard C integer to a multiprecision integer.
 145  */
 146
 147 #define mp_fromINT(name, type)                                          \
 148   extern mp *mp_from##name(mp */*d*/, type /*i*/)
 149
 150 mp_fromINT(short, short);
 151 mp_fromINT(ushort, unsigned short);
 152 mp_fromINT(int, int);
 153 mp_fromINT(uint, unsigned);
 154 mp_fromINT(uint32, uint32);
 155 mp_fromINT(long, long);
 156 mp_fromINT(ulong, unsigned long);
 157
 158 #undef mp_fromINT
 159
 160 /* --- @mp_toINT@ --- *
 161  *
 162  * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 163  *
 164  * Returns:     The value of the integer @m@ as a C integer.
 165  *
 166  * Use:         Converts a multiprecision integer to a standard C integer.
 167  *              If the value of the multiprecision integer cannot be
 168  *              represented in the return type, and the return type is
 169  *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 170  *              type is signed, the behaviour is undefined.
 171  */
 172
 173 #define mp_toINT(name, type)                                            \
 174   extern type mp_to##name(const mp */*m*/)
 175
 176 mp_toINT(short, short);
 177 mp_toINT(ushort, unsigned short);
 178 mp_toINT(int, int);
 179 mp_toINT(uint, unsigned);
 180 mp_toINT(uint32, uint32);
 181 mp_toINT(long, long);
 182 mp_toINT(ulong, unsigned long);
 183
 184 #undef mp_toINT
 185
 186 /*----- That's all, folks -------------------------------------------------*/
 187
 188 #ifdef __cplusplus
 189   }
 190 #endif
 191
 192 #endif