C++ (Cpp) s_is_power_of_two Examples

Example #1

File: bn_mp_div_d.c Project: AIdrifter/samba

/* single digit division (based on routine from MPI) */
int mp_div_d (mp_int * a, mp_digit b, mp_int * c, mp_digit * d)
{
  mp_int  q;
  mp_word w;
  mp_digit t;
  int     res, ix;

  /* cannot divide by zero */
  if (b == 0) {
     return MP_VAL;
  }

  /* quick outs */
  if (b == 1 || mp_iszero(a) == 1) {
     if (d != NULL) {
        *d = 0;
     }
     if (c != NULL) {
        return mp_copy(a, c);
     }
     return MP_OKAY;
  }

  /* power of two ? */
  if (s_is_power_of_two(b, &ix) == 1) {
     if (d != NULL) {
        *d = a->dp[0] & ((((mp_digit)1)<<ix) - 1);
     }
     if (c != NULL) {
        return mp_div_2d(a, ix, c, NULL);
     }
     return MP_OKAY;
  }

#ifdef BN_MP_DIV_3_C
  /* three? */
  if (b == 3) {
     return mp_div_3(a, c, d);
  }
#endif

  /* no easy answer [c'est la vie].  Just division */
  if ((res = mp_init_size(&q, a->used)) != MP_OKAY) {
     return res;
  }

  q.used = a->used;
  q.sign = a->sign;
  w = 0;
  for (ix = a->used - 1; ix >= 0; ix--) {
     w = (w << ((mp_word)DIGIT_BIT)) | ((mp_word)a->dp[ix]);

     if (w >= b) {
        t = (mp_digit)(w / b);
        w -= ((mp_word)t) * ((mp_word)b);
      } else {
        t = 0;
      }
      q.dp[ix] = (mp_digit)t;
  }

  if (d != NULL) {
     *d = (mp_digit)w;
  }

  if (c != NULL) {
     mp_clamp(&q);
     mp_exch(&q, c);
  }
  mp_clear(&q);

  return res;
}

Example #2

File: fp_div_d.c Project: 30rasheed/x-VTOLdrone

/* a/b => cb + d == a */
int fp_div_d(fp_int *a, fp_digit b, fp_int *c, fp_digit *d)
{
  fp_int   q;
  fp_word  w;
  fp_digit t;
  int      ix;

  /* cannot divide by zero */
  if (b == 0) {
     return FP_VAL;
  }

  /* quick outs */
  if (b == 1 || fp_iszero(a) == 1) {
     if (d != NULL) {
        *d = 0;
     }
     if (c != NULL) {
        fp_copy(a, c);
     }
     return FP_OKAY;
  }

  /* power of two ? */
  if (s_is_power_of_two(b, &ix) == 1) {
     if (d != NULL) {
        *d = a->dp[0] & ((((fp_digit)1)<<ix) - 1);
     }
     if (c != NULL) {
        fp_div_2d(a, ix, c, NULL);
     }
     return FP_OKAY;
  }

  /* no easy answer [c'est la vie].  Just division */
  fp_init(&q);
  
  q.used = a->used;
  q.sign = a->sign;
  w = 0;
  for (ix = a->used - 1; ix >= 0; ix--) {
     w = (w << ((fp_word)DIGIT_BIT)) | ((fp_word)a->dp[ix]);
     
     if (w >= b) {
        t = (fp_digit)(w / b);
        w -= ((fp_word)t) * ((fp_word)b);
      } else {
        t = 0;
      }
      q.dp[ix] = (fp_digit)t;
  }
  
  if (d != NULL) {
     *d = (fp_digit)w;
  }
  
  if (c != NULL) {
     fp_clamp(&q);
     fp_copy(&q, c);
  }
 
  return FP_OKAY;
}