kc3-lang/libtommath/bn_mp_div_2.c

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• Hash : 4534056c
  Author :
  Date : 2019-05-13T00:22:18
  

  use enums mp_err, mp_ord, mp_bool, mp_sign * MP_USE_ENUMS enables enums * Wc++-compat catches some implicit conversions if MP_USE_ENUMS is defined * 100% backwards compatible API/ABI if MP_USE_ENUMS is not defined

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• bn_mp_div_2.c

• #include "tommath_private.h"
  #ifdef BN_MP_DIV_2_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* b = a/2 */
  mp_err mp_div_2(const mp_int *a, mp_int *b)
  {
     int     x, oldused;
     mp_err res;
  
     /* copy */
     if (b->alloc < a->used) {
        if ((res = mp_grow(b, a->used)) != MP_OKAY) {
           return res;
        }
     }
  
     oldused = b->used;
     b->used = a->used;
     {
        mp_digit r, rr, *tmpa, *tmpb;
  
        /* source alias */
        tmpa = a->dp + b->used - 1;
  
        /* dest alias */
        tmpb = b->dp + b->used - 1;
  
        /* carry */
        r = 0;
        for (x = b->used - 1; x >= 0; x--) {
           /* get the carry for the next iteration */
           rr = *tmpa & 1u;
  
           /* shift the current digit, add in carry and store */
           *tmpb-- = (*tmpa-- >> 1) | (r << (MP_DIGIT_BIT - 1));
  
           /* forward carry to next iteration */
           r = rr;
        }
  
        /* zero excess digits */
        MP_ZERO_DIGITS(b->dp + b->used, oldused - b->used);
     }
     b->sign = a->sign;
     mp_clamp(b);
     return MP_OKAY;
  }
  #endif
  

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