Function do_sub

strings/decimal.c:1892–2025

to=from1-from2. if to==0, return -1/0/+1 - the result of the comparison */

/* to=from1-from2.
   if to==0, return -1/0/+1 - the result of the comparison */
static int do_sub(const decimal_t *from1, const decimal_t *from2, decimal_t *to)
{
  int intg1=ROUND_UP(from1->intg), intg2=ROUND_UP(from2->intg),
      frac1=ROUND_UP(from1->frac), frac2=ROUND_UP(from2->frac);
  int frac0= MY_MAX(frac1, frac2), error;
  dec1 *buf1, *buf2, *buf0, *stop1, *stop2, *start1, *start2, carry=0;

  /* let carry:=1 if from2 > from1 */
  start1=buf1=from1->buf; stop1=buf1+intg1;
  start2=buf2=from2->buf; stop2=buf2+intg2;
  if (unlikely(*buf1 == 0))
  {
    while (buf1 < stop1 && *buf1 == 0)
      buf1++;
    start1=buf1;
    intg1= (int) (stop1-buf1);
  }
  if (unlikely(*buf2 == 0))
  {
    while (buf2 < stop2 && *buf2 == 0)
      buf2++;
    start2=buf2;
    intg2= (int) (stop2-buf2);
  }
  if (intg2 > intg1)
    carry=1;
  else if (intg2 == intg1)
  {
    dec1 *end1= stop1 + (frac1 - 1);
    dec1 *end2= stop2 + (frac2 - 1);
    while (unlikely((buf1 <= end1) && (*end1 == 0)))
      end1--;
    while (unlikely((buf2 <= end2) && (*end2 == 0)))
      end2--;
    frac1= (int) (end1 - stop1) + 1;
    frac2= (int) (end2 - stop2) + 1;
    while (buf1 <=end1 && buf2 <= end2 && *buf1 == *buf2)
      buf1++, buf2++;
    if (buf1 <= end1)
    {
      if (buf2 <= end2)
        carry= *buf2 > *buf1;
      else
        carry= 0;
    }
    else
    {
      if (buf2 <= end2)
        carry=1;
      else /* short-circuit everything: from1 == from2 */
      {
        if (to == 0) /* decimal_cmp() */
          return 0;
        decimal_make_zero(to);
        return E_DEC_OK;
      }
    }
  }