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 #ifndef CATACOMB_MP_H
  40 #  include "mp.h"
  41 #endif
  42
  43 /*----- Generic translation macros ----------------------------------------*/
  44
  45 /* --- Warning damage control --- *
  46  *
  47  * GCC (at least) isn't clever enough to work out that the division in
  48  * @MP_FROMINT@ is actually safe (since it will only be executed if @_i >
  49  * MPW_MAX@, which would prove that @(type)MPW_MAX + 1 != 0@).  So here's
  50  * some machinery to shut it up.
  51  */
  52
  53 #if __GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
  54 #  define MP_FROMINT_MUFFLE_WARNING(x) do {                             \
  55         _Pragma("GCC diagnostic push")                                  \
  56         _Pragma("GCC diagnostic ignored \"-Wdiv-by-zero\"")             \
  57         x                                                               \
  58         _Pragma("GCC diagnostic pop")                                   \
  59    } while (0)
  60 #else
  61 #  define MP_FROMINT_MUFFLE_WARNING(x) do { x } while (0)
  62 #endif
  63
  64 /* --- @MP_FROMINT@ --- *
  65  *
  66  * Arguments:   @d@ = destination multiprecision integer
  67  *              @type@ = type of integer which @i@ is
  68  *              @i@ = a standard C integer
  69  *
  70  * Use:         Stores the value of @i@ in @d@.  This macro is actually
  71  *              rather subtle in places.  Be careful what you change.
  72  */
  73
  74 #define MP_FROMINT(d, type, i) do {                                     \
  75   type _i = (i);                                                        \
  76   size_t _o = 0;                                                        \
  77   mp *_d = (d);                                                         \
  78   size_t _sz = 4;                                                       \
  79                                                                         \
  80   MP_DEST(_d, _sz, 0);                                                  \
  81   _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
  82                                                                         \
  83   if (_i >= 0) {                                                        \
  84     while (_i) {                                                        \
  85       if (_o == _sz) {                                                  \
  86         _sz <<= 1;                                                      \
  87         MP_ENSURE(_d, _sz);                                             \
  88       }                                                                 \
  89       _d->v[_o++] = MPW(_i);                                            \
  90       if (_i <= MPW_MAX)                                                \
  91         break;                                                          \
  92       else                                                              \
  93         MP_FROMINT_MUFFLE_WARNING({ _i /= (type)MPW_MAX + 1; });        \
  94     }                                                                   \
  95   } else {                                                              \
  96     _d->f |= MP_NEG;                                                    \
  97     while (_i) {                                                        \
  98       if (_o == _sz) {                                                  \
  99         _sz <<= 1;                                                      \
 100         MP_ENSURE(_d, _sz);                                             \
 101       }                                                                 \
 102       _d->v[_o++] = MPW(-_i);                                           \
 103       if (_i >= -MPW_MAX)                                               \
 104         break;                                                          \
 105       else                                                              \
 106         MP_FROMINT_MUFFLE_WARNING({ _i /= (type)MPW_MAX + 1; });        \
 107     }                                                                   \
 108   }                                                                     \
 109                                                                         \
 110   _d->vl = _d->v + _o;                                                  \
 111   (d) = _d;                                                             \
 112 } while (0)
 113
 114 /* --- @MP_TOINT@ --- *
 115  *
 116  * Arguments:   @m@ = a multiprecision integer
 117  *              @type@ = the type of @i@
 118  *              @max@ = the largest value @i@ can represent
 119  *              @i@ = an integer variable
 120  *
 121  * Use:         Stores the value of a multiprecision integer in a standard C
 122  *              integer.  If the value won't fit, the behaviour is determined
 123  *              by the type of @i@: if @i@ is unsigned, the value of the
 124  *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 125  *              signed, the behaviour is undefined.
 126  *
 127  *              If you don't want to be bitten by these sorts of things, keep
 128  *              copies of @INT_MAX@ or whatever is appropriate in
 129  *              multiprecision form and compare before conversion.
 130  */
 131
 132 #define MP_TOINT(m, type, max, i) do {                                  \
 133   type _i = 0;                                                          \
 134   type _max = (max);                                                    \
 135   unsigned _s = 0;                                                      \
 136   const mp *_m = (m);                                                   \
 137   const mpw *_v = _m->v, *_vl = _m->vl;                                 \
 138                                                                         \
 139   /* --- Do all the arithmetic in negative numbers --- */               \
 140                                                                         \
 141   while (_v < _vl && _max > 0) {                                        \
 142     _i -= *_v << _s;                                                    \
 143     _s += MPW_BITS;                                                     \
 144     _v++;                                                               \
 145     _max /= (mpd)MPW_MAX + 1;                                           \
 146   }                                                                     \
 147   if (!MP_NEGP(_m))                                                     \
 148     _i = -_i;                                                           \
 149   (i) = _i;                                                             \
 150 } while (0)
 151
 152 /*----- Functions provided ------------------------------------------------*/
 153
 154 /* --- @mp_fromINT@ --- *
 155  *
 156  * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 157  *              @INT i@ = standard C integer to convert
 158  *
 159  * Returns:     The resulting multiprecision integer.
 160  *
 161  * Use:         Converts a standard C integer to a multiprecision integer.
 162  */
 163
 164 #define mp_fromINT(name, type)                                          \
 165   extern mp *mp_from##name(mp */*d*/, type /*i*/)
 166
 167 mp_fromINT(short, short);
 168 mp_fromINT(ushort, unsigned short);
 169 mp_fromINT(int, int);
 170 mp_fromINT(uint, unsigned);
 171 mp_fromINT(uint32, uint32);
 172 mp_fromINT(long, long);
 173 mp_fromINT(ulong, unsigned long);
 174
 175 #undef mp_fromINT
 176
 177 /* --- @mp_toINT@ --- *
 178  *
 179  * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 180  *
 181  * Returns:     The value of the integer @m@ as a C integer.
 182  *
 183  * Use:         Converts a multiprecision integer to a standard C integer.
 184  *              If the value of the multiprecision integer cannot be
 185  *              represented in the return type, and the return type is
 186  *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 187  *              type is signed, the behaviour is undefined.
 188  */
 189
 190 #define mp_toINT(name, type)                                            \
 191   extern type mp_to##name(const mp */*m*/)
 192
 193 mp_toINT(short, short);
 194 mp_toINT(ushort, unsigned short);
 195 mp_toINT(int, int);
 196 mp_toINT(uint, unsigned);
 197 mp_toINT(uint32, uint32);
 198 mp_toINT(long, long);
 199 mp_toINT(ulong, unsigned long);
 200
 201 #undef mp_toINT
 202
 203 /*----- That's all, folks -------------------------------------------------*/
 204
 205 #ifdef __cplusplus
 206   }
 207 #endif
 208
 209 #endif