#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_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