kc3-lang/libtommath/s_mp_div_small.c

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• Hash : 1cc289d2
  Author :
  Date : 2019-11-09T20:23:03
  

  better use of mp_isneg() and mp_iszero()

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• s_mp_div_small.c

• #include "tommath_private.h"
  #ifdef S_MP_DIV_SMALL_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* slower bit-bang division... also smaller */
  mp_err s_mp_div_small(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
  {
     mp_int ta, tb, tq, q;
     int n;
     bool neg;
     mp_err err;
  
     /* init our temps */
     if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
        return err;
     }
  
     mp_set(&tq, 1uL);
     n = mp_count_bits(a) - mp_count_bits(b);
     if ((err = mp_abs(a, &ta)) != MP_OKAY)                         goto LBL_ERR;
     if ((err = mp_abs(b, &tb)) != MP_OKAY)                         goto LBL_ERR;
     if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY)                 goto LBL_ERR;
     if ((err = mp_mul_2d(&tq, n, &tq)) != MP_OKAY)                 goto LBL_ERR;
  
     while (n-- >= 0) {
        if (mp_cmp(&tb, &ta) != MP_GT) {
           if ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY)            goto LBL_ERR;
           if ((err = mp_add(&q, &tq, &q)) != MP_OKAY)              goto LBL_ERR;
        }
        if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY)        goto LBL_ERR;
        if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY)        goto LBL_ERR;
     }
  
     /* now q == quotient and ta == remainder */
  
     neg = (a->sign != b->sign);
     if (c != NULL) {
        mp_exch(c, &q);
        c->sign = ((neg && !mp_iszero(c)) ? MP_NEG : MP_ZPOS);
     }
     if (d != NULL) {
        mp_exch(d, &ta);
        d->sign = (mp_iszero(d) ? MP_ZPOS : a->sign);
     }
  LBL_ERR:
     mp_clear_multi(&ta, &tb, &tq, &q, NULL);
     return err;
  }
  
  #endif
  

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