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