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   1 /* -*-c-*-
   2  *
   3  * $Id: mpint.h,v 1.5 2002/01/13 19:23:16 mdw Exp $
   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 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: mpint.h,v $
  33  * Revision 1.5  2002/01/13 19:23:16  mdw
  34  * Fix division-by-zero bug translating @MPW_MAX@ to an @mp@.
  35  *
  36  * Revision 1.4  2000/10/08 12:04:01  mdw
  37  * Remove spurious semicolon.
  38  *
  39  * Revision 1.3  2000/06/17 11:45:09  mdw
  40  * Major memory management overhaul.  Added arena support.  Use the secure
  41  * arena for secret integers.  Replace and improve the MP management macros
  42  * (e.g., replace MP_MODIFY by MP_DEST).
  43  *
  44  * Revision 1.2  1999/12/10 23:22:53  mdw
  45  * Support for uint32.
  46  *
  47  * Revision 1.1  1999/11/25 11:38:31  mdw
  48  * Support for conversions between MPs and C integers.
  49  *
  50  */
  51
  52 #ifndef CATACOMB_MPINT_H
  53 #define CATACOMB_MPINT_H
  54
  55 #ifdef __cplusplus
  56   extern "C" {
  57 #endif
  58
  59 /*----- Header files ------------------------------------------------------*/
  60
  61 #include <limits.h>
  62
  63 #ifndef CATACOMB_MP_H
  64 #  include "mp.h"
  65 #endif
  66
  67 /*----- Generic translation macros ----------------------------------------*/
  68
  69 /* --- @MP_FROMINT@ --- *
  70  *
  71  * Arguments:   @d@ = destination multiprecision integer
  72  *              @type@ = type of integer which @i@ is
  73  *              @i@ = a standard C integer
  74  *
  75  * Use:         Stores the value of @i@ in @d@.  This macro is actually
  76  *              rather subtle in places.  Be careful what you change.
  77  */
  78
  79 #define MP_FROMINT(d, type, i) do {                                     \
  80   type _i = (i);                                                        \
  81   size_t _o = 0;                                                        \
  82   mp *_d = (d);                                                         \
  83   size_t _sz = 4;                                                       \
  84                                                                         \
  85   MP_DEST(_d, _sz, 0);                                                  \
  86   _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
  87                                                                         \
  88   /* --- Set the sign on the MP --- *                                   \
  89    *                                                                    \
  90    * If the input integer is *not* negative, then negate it.  This      \
  91    * fixes a problem with two's complement machines where the most      \
  92    * negative value actually has larger magnitude than the most         \
  93    * positive, and hence -TYPE_MIN == TYPE_MIN but TYPE_MIN != 0.  If   \
  94    * all the work is carried out on negative numbers there isn't a      \
  95    * problem.                                                           \
  96    */                                                                   \
  97                                                                         \
  98   if (_i >= 0)                                                          \
  99     _i = -_i;                                                           \
 100   else                                                                  \
 101     _d->f |= MP_NEG;                                                    \
 102                                                                         \
 103   while (_i) {                                                          \
 104     if (_o == _sz) {                                                    \
 105       _sz <<= 1;                                                        \
 106       MP_ENSURE(_d, _sz);                                               \
 107     }                                                                   \
 108     _d->v[_o++] = MPW(-_i);                                             \
 109                                                                         \
 110     /* --- More subtlety --- *                                          \
 111      *                                                                  \
 112      * Ideally, I'd like to just shift @i@ right by @MPW_BITS@.  But I  \
 113      * can't, because that might be more than I'm allowed.  I can't     \
 114      * divide by @MPW_MAX + 1@ because that might turn out to be zero   \
 115      * in my current type, and besides which it's unsigned which messes \
 116      * up all of my negative arithmetic.  So do an explicit test here.  \
 117      */                                                                 \
 118                                                                         \
 119     if (_i >= -MPW_MAX)                                                 \
 120       break;                                                            \
 121     else                                                                \
 122       _i /= (type)MPW_MAX + 1;                                          \
 123   }                                                                     \
 124   _d->vl = _d->v + _o;                                                  \
 125   (d) = _d;                                                             \
 126 } while (0)
 127
 128 /* --- @MP_TOINT@ --- *
 129  *
 130  * Arguments:   @m@ = a multiprecision integer
 131  *              @type@ = the type of @i@
 132  *              @max@ = the largest value @i@ can represent
 133  *              @i@ = an integer variable
 134  *
 135  * Use:         Stores the value of a multiprecision integer in a standard C
 136  *              integer.  If the value won't fit, the behaviour is determined
 137  *              by the type of @i@: if @i@ is unsigned, the value of the
 138  *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 139  *              signed, the behaviour is undefined.
 140  *
 141  *              If you don't want to be bitten by these sorts of things, keep
 142  *              copies of @INT_MAX@ or whatever is appropriate in
 143  *              multiprecision form and compare before conversion.
 144  */
 145
 146 #define MP_TOINT(m, type, max, i) do {                                  \
 147   type _i = 0;                                                          \
 148   type _max = (max);                                                    \
 149   unsigned _s = 0;                                                      \
 150   const mp *_m = (m);                                                   \
 151   const mpw *_v = _m->v, *_vl = _m->vl;                                 \
 152                                                                         \
 153   /* --- Do all the arithmetic in negative numbers --- */               \
 154                                                                         \
 155   while (_v < _vl && _max > 0) {                                        \
 156     _i -= *_v << _s;                                                    \
 157     _s += MPW_BITS;                                                     \
 158     _v++;                                                               \
 159     _max /= (mpd)MPW_MAX + 1;                                           \
 160   }                                                                     \
 161   if (!(_m->f & MP_NEG))                                                \
 162     _i = -_i;                                                           \
 163   (i) = _i;                                                             \
 164 } while (0)
 165
 166 /*----- Functions provided ------------------------------------------------*/
 167
 168 /* --- @mp_fromINT@ --- *
 169  *
 170  * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 171  *              @INT i@ = standard C integer to convert
 172  *
 173  * Returns:     The resulting multiprecision integer.
 174  *
 175  * Use:         Converts a standard C integer to a multiprecision integer.
 176  */
 177
 178 #define mp_fromINT(name, type)                                          \
 179   extern mp *mp_from##name(mp */*d*/, type /*i*/)
 180
 181 mp_fromINT(short, short);
 182 mp_fromINT(ushort, unsigned short);
 183 mp_fromINT(int, int);
 184 mp_fromINT(uint, unsigned);
 185 mp_fromINT(uint32, uint32);
 186 mp_fromINT(long, long);
 187 mp_fromINT(ulong, unsigned long);
 188
 189 #undef mp_fromINT
 190
 191 /* --- @mp_toINT@ --- *
 192  *
 193  * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 194  *
 195  * Returns:     The value of the integer @m@ as a C integer.
 196  *
 197  * Use:         Converts a multiprecision integer to a standard C integer.
 198  *              If the value of the multiprecision integer cannot be
 199  *              represented in the return type, and the return type is
 200  *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 201  *              type is signed, the behaviour is undefined.
 202  */
 203
 204 #define mp_toINT(name, type)                                            \
 205   extern type mp_to##name(const mp */*m*/)
 206
 207 mp_toINT(short, short);
 208 mp_toINT(ushort, unsigned short);
 209 mp_toINT(int, int);
 210 mp_toINT(uint, unsigned);
 211 mp_toINT(uint32, uint32);
 212 mp_toINT(long, long);
 213 mp_toINT(ulong, unsigned long);
 214
 215 #undef mp_toINT
 216
 217 /*----- That's all, folks -------------------------------------------------*/
 218
 219 #ifdef __cplusplus
 220   }
 221 #endif
 222
 223 #endif