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

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