Generic interface.

[u/mdw/catacomb] / mpint.h

/* -*-c-*-
 *
 * $Id: mpint.h,v 1.1 1999/11/25 11:38:31 mdw Exp $
 *
 * Conversion between MPs and standard C integers
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * Catacomb is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: mpint.h,v $
 * Revision 1.1  1999/11/25 11:38:31  mdw
 * Support for conversions between MPs and C integers.
 *
 */

#ifndef MPINT_H
#define MPINT_H

#ifdef __cplusplus
  extern "C" {
#endif

/*----- Header files ------------------------------------------------------*/

#include <limits.h>

#ifndef MP_H
#  include "mp.h"
#endif

/*----- Generic translation macros ----------------------------------------*/

/* --- @MP_FROMINT@ --- *
 *
 * Arguments:   @d@ = destination multiprecision integer
 *              @type@ = type of integer which @i@ is
 *              @i@ = a standard C integer
 *
 * Use:         Stores the value of @i@ in @d@.  This macro is actually
 *              rather subtle in places.  Be careful what you change.
 */

#define MP_FROMINT(d, type, i) do {                                     \
  type _i = (i);                                                        \
  size_t _o = 0;                                                        \
  mp *_d = (d);                                                         \
  size_t _sz = 4;                                                       \
                                                                        \
  MP_MODIFY(_d, _sz);                                                   \
  _d->f &= ~(MP_NEG | MP_UNDEF);                                        \
                                                                        \
  /* --- Set the sign on the MP --- *                                   \
   *                                                                    \
   * If the input integer is *not* negative, then negate it.  This      \
   * fixes a problem with two's complement machines where the most      \
   * negative value actually has larger magnitude than the most         \
   * positive, and hence -TYPE_MIN == TYPE_MIN but TYPE_MIN != 0.  If   \
   * all the work is carried out on negative numbers there isn't a      \
   * problem.                                                           \
   */                                                                   \
                                                                        \
  if (_i >= 0)                                                          \
    _i = -_i;                                                           \
  else                                                                  \
    _d->f |= MP_NEG;                                                    \
                                                                        \
  while (_i) {                                                          \
    if (_o == _sz) {                                                    \
      _sz <<= 1;                                                        \
      MP_ENSURE(_d, _sz);                                               \
    }                                                                   \
    _d->v[_o++] = MPW(-_i);                                             \
                                                                        \
    /* --- More subtlety --- *                                          \
     *                                                                  \
     * Ideally, I'd like to just shift @i@ right by @MPW_BITS@.  But I  \
     * can't, because that might be more than I'm allowed.  I can't     \
     * divide by @MPW_MAX + 1@ because that might turn out to be zero   \
     * in my current type, and besides which it's unsigned which messes \
     * up all of my negative arithmetic.  So do an explicit test here.  \
     */                                                                 \
                                                                        \
    if (_i > -MPW_MAX)                                                  \
      break;                                                            \
    else                                                                \
      _i /= (type)MPW_MAX + 1;                                          \
  }                                                                     \
  _d->vl = _d->v + _o;                                                  \
  (d) = _d;                                                             \
} while (0)

/* --- @MP_TOINT@ --- *
 *
 * Arguments:   @m@ = a multiprecision integer
 *              @type@ = the type of @i@
 *              @max@ = the largest value @i@ can represent
 *              @i@ = an integer variable
 *
 * Use:         Stores the value of a multiprecision integer in a standard C
 *              integer.  If the value won't fit, the behaviour is determined
 *              by the type of @i@: if @i@ is unsigned, the value of the
 *              multiprecision integer modulo @max + 1@ is stored; if @i@ is
 *              signed, the behaviour is undefined.
 *
 *              If you don't want to be bitten by these sorts of things, keep
 *              copies of @INT_MAX@ or whatever is appropriate in
 *              multiprecision form and compare before conversion.
 */

#define MP_TOINT(m, type, max, i) do {                                  \
  type _i = 0;                                                          \
  type _max = (max);                                                    \
  unsigned _s = 0;                                                      \
  const mp *_m = (m);                                                   \
  const mpw *_v = _m->v, *_vl = _m->vl;                                 \
                                                                        \
  /* --- Do all the arithmetic in negative numbers --- */               \
                                                                        \
  while (_v < _vl && _max > 0) {                                        \
    _i -= *_v << _s;                                                    \
    _s += MPW_BITS;                                                     \
    _v++;                                                               \
    _max /= (mpd)MPW_MAX + 1;                                           \
  }                                                                     \
  if (!(_m->f & MP_NEG))                                                \
    _i = -_i;                                                           \
  (i) = _i;                                                             \
} while (0)

/*----- Functions provided ------------------------------------------------*/

/* --- @mp_fromINT@ --- *
 *
 * Arguments:   @mp *d@ = pointer to destination multiprecision integer
 *              @INT i@ = standard C integer to convert
 *
 * Returns:     The resulting multiprecision integer.
 *
 * Use:         Converts a standard C integer to a multiprecision integer.
 */

#define mp_fromINT(name, type)                                          \
  extern mp *mp_from##name(mp */*d*/, type /*i*/)

mp_fromINT(short, short);
mp_fromINT(ushort, unsigned short);
mp_fromINT(int, int);
mp_fromINT(uint, unsigned);
mp_fromINT(long, long);
mp_fromINT(ulong, unsigned long);

#undef mp_fromINT

/* --- @mp_toINT@ --- *
 *
 * Arguments:   @const mp *m@ = pointer to a multiprecision integer
 *
 * Returns:     The value of the integer @m@ as a C integer.
 *
 * Use:         Converts a multiprecision integer to a standard C integer.
 *              If the value of the multiprecision integer cannot be
 *              represented in the return type, and the return type is
 *              unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
 *              type is signed, the behaviour is undefined.
 */

#define mp_toINT(name, type)                                            \
  extern type mp_to##name(const mp */*m*/);

mp_toINT(short, short);
mp_toINT(ushort, unsigned short);
mp_toINT(int, int);
mp_toINT(uint, unsigned);
mp_toINT(long, long);
mp_toINT(ulong, unsigned long);

#undef mp_toINT

/*----- That's all, folks -------------------------------------------------*/

#ifdef __cplusplus
  }
#endif

#endif