kc3-lang/libtommath/mp_div_2.c

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• Hash : 7a68f128
  Author :
  Date : 2019-10-19T16:24:39
  

  Execute move.sh - Rename files from bn_* to match the function names. * git blame <renamed-file> is not affected * git log --follow <renamed-file> can be used to show log across renames

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• mp_div_2.c

• #include "tommath_private.h"
  #ifdef 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_digit r, rr, *tmpa, *tmpb;
     mp_err err;
  
     /* copy */
     if (b->alloc < a->used) {
        if ((err = mp_grow(b, a->used)) != MP_OKAY) {
           return err;
        }
     }
  
     oldused = b->used;
     b->used = a->used;
  
     /* 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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