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 #include <mLib/macros.h>
  40
  41 #ifndef CATACOMB_MP_H
  42 #  include "mp.h"
  43 #endif
  44
  45 /*----- Generic translation macros ----------------------------------------*/
  46
  47 /* --- Warning damage control --- *
  48  *
  49  * GCC (at least) isn't clever enough to work out that the division in
  50  * @MP_FROMINT@ is actually safe (since it will only be executed if @_i >
  51  * MPW_MAX@, which would prove that @(type)MPW_MAX + 1 != 0@).
  52  */
  53
  54 /* --- @MP_FROMINT@ --- *
  55  *
  56  * Arguments:   @d@ = destination multiprecision integer
  57  *              @type@ = type of integer which @i@ is
  58  *              @i@ = a standard C integer
  59  *
  60  * Use:         Stores the value of @i@ in @d@.  This macro is actually
  61  *              rather subtle in places.  Be careful what you change.
  62  */
  63
  64 #define MP_FROMINT(d, type, i) do {                                     \
  65   type _i = (i);                                                        \
  66   size_t _o = 0;                                                        \
  67   mp *_d = (d);                                                         \
  68   size_t _sz = 4;                                                       \
  69                                                                         \
  70   MP_DEST(_d, _sz, 0);                                                  \
  71   _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
  72                                                                         \
  73   if (_i >= 0) {                                                        \
  74     while (_i) {                                                        \
  75       if (_o == _sz) {                                                  \
  76         _sz <<= 1;                                                      \
  77         MP_ENSURE(_d, _sz);                                             \
  78       }                                                                 \
  79       _d->v[_o++] = MPW(_i);                                            \
  80       if (_i <= MPW_MAX)                                                \
  81         break;                                                          \
  82       else                                                              \
  83         MUFFLE_WARNINGS_STMT(GCC_WARNING("-Wdiv-by-zero"), {            \
  84           _i /= (type)MPW_MAX + 1;                                      \
  85         });                                                             \
  86     }                                                                   \
  87   } else {                                                              \
  88     _d->f |= MP_NEG;                                                    \
  89     while (_i) {                                                        \
  90       if (_o == _sz) {                                                  \
  91         _sz <<= 1;                                                      \
  92         MP_ENSURE(_d, _sz);                                             \
  93       }                                                                 \
  94       _d->v[_o++] = MPW(-_i);                                           \
  95       if (_i >= -MPW_MAX)                                               \
  96         break;                                                          \
  97       else                                                              \
  98         MUFFLE_WARNINGS_STMT(GCC_WARNING("-Wdiv-by-zero"), {            \
  99           _i /= (type)MPW_MAX + 1;                                      \
 100         });                                                             \
 101     }                                                                   \
 102   }                                                                     \
 103                                                                         \
 104   _d->vl = _d->v + _o;                                                  \
 105   (d) = _d;                                                             \
 106 } while (0)
 107
 108 /* --- @MP_TOINT@ --- *
 109  *
 110  * Arguments:   @m@ = a multiprecision integer
 111  *              @type@ = the type of @i@
 112  *              @max@ = the largest value @i@ can represent
 113  *              @i@ = an integer variable
 114  *
 115  * Use:         Stores the value of a multiprecision integer in a standard C
 116  *              integer.  If the value won't fit, the behaviour is determined
 117  *              by the type of @i@: if @i@ is unsigned, the value of the
 118  *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 119  *              signed, the behaviour is undefined.
 120  *
 121  *              If you don't want to be bitten by these sorts of things, keep
 122  *              copies of @INT_MAX@ or whatever is appropriate in
 123  *              multiprecision form and compare before conversion.
 124  */
 125
 126 #define MP_TOINT(m, type, max, i) do {                                  \
 127   type _i = 0;                                                          \
 128   type _max = (max);                                                    \
 129   unsigned _s = 0;                                                      \
 130   const mp *_m = (m);                                                   \
 131   const mpw *_v = _m->v, *_vl = _m->vl;                                 \
 132                                                                         \
 133   /* --- Do all the arithmetic in negative numbers --- */               \
 134                                                                         \
 135   while (_v < _vl && _max > 0) {                                        \
 136     _i -= *_v << _s;                                                    \
 137     _s += MPW_BITS;                                                     \
 138     _v++;                                                               \
 139     _max /= (mpd)MPW_MAX + 1;                                           \
 140   }                                                                     \
 141   if (!MP_NEGP(_m))                                                     \
 142     _i = -_i;                                                           \
 143   (i) = _i;                                                             \
 144 } while (0)
 145
 146 /*----- Functions provided ------------------------------------------------*/
 147
 148 /* --- @mp_fromINT@ --- *
 149  *
 150  * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 151  *              @INT i@ = standard C integer to convert
 152  *
 153  * Returns:     The resulting multiprecision integer.
 154  *
 155  * Use:         Converts a standard C integer to a multiprecision integer.
 156  */
 157
 158 #define mp_fromINT(name, type)                                          \
 159   extern mp *mp_from##name(mp */*d*/, type /*i*/)
 160
 161 mp_fromINT(short, short);
 162 mp_fromINT(ushort, unsigned short);
 163 mp_fromINT(int, int);
 164 mp_fromINT(uint, unsigned);
 165 mp_fromINT(uint32, uint32);
 166 mp_fromINT(long, long);
 167 mp_fromINT(ulong, unsigned long);
 168
 169 #undef mp_fromINT
 170
 171 /* --- @mp_toINT@ --- *
 172  *
 173  * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 174  *
 175  * Returns:     The value of the integer @m@ as a C integer.
 176  *
 177  * Use:         Converts a multiprecision integer to a standard C integer.
 178  *              If the value of the multiprecision integer cannot be
 179  *              represented in the return type, and the return type is
 180  *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 181  *              type is signed, the behaviour is undefined.
 182  */
 183
 184 #define mp_toINT(name, type)                                            \
 185   extern type mp_to##name(const mp */*m*/)
 186
 187 mp_toINT(short, short);
 188 mp_toINT(ushort, unsigned short);
 189 mp_toINT(int, int);
 190 mp_toINT(uint, unsigned);
 191 mp_toINT(uint32, uint32);
 192 mp_toINT(long, long);
 193 mp_toINT(ulong, unsigned long);
 194
 195 #undef mp_toINT
 196
 197 /*----- That's all, folks -------------------------------------------------*/
 198
 199 #ifdef __cplusplus
 200   }
 201 #endif
 202
 203 #endif