int decimal2bin()

in mysql_strings/decimal.cc [1344:1456]
100 lines of code
27 McCabe index (conditional complexity)

int decimal2bin(const decimal_t *from, uchar *to, int precision, int frac) {
  dec1 mask = from->sign ? -1 : 0, *buf1 = from->buf, *stop1;
  int error = E_DEC_OK, intg = precision - frac, isize1, intg1, intg1x,
      from_intg, intg0 = intg / DIG_PER_DEC1, frac0 = frac / DIG_PER_DEC1,
      intg0x = intg - intg0 * DIG_PER_DEC1,
      frac0x = frac - frac0 * DIG_PER_DEC1, frac1 = from->frac / DIG_PER_DEC1,
      frac1x = from->frac - frac1 * DIG_PER_DEC1,
      isize0 = intg0 * sizeof(dec1) + dig2bytes[intg0x],
      fsize0 = frac0 * sizeof(dec1) + dig2bytes[frac0x],
      fsize1 = frac1 * sizeof(dec1) + dig2bytes[frac1x];
  const int orig_isize0 = isize0;
  const int orig_fsize0 = fsize0;
  uchar *orig_to = to;

  buf1 = remove_leading_zeroes(from, &from_intg);

  if (unlikely(from_intg + fsize1 == 0)) {
    mask = 0; /* just in case */
    intg = 1;
    buf1 = &mask;
  }

  intg1 = from_intg / DIG_PER_DEC1;
  intg1x = from_intg - intg1 * DIG_PER_DEC1;
  isize1 = intg1 * sizeof(dec1) + dig2bytes[intg1x];

  if (intg < from_intg) {
    buf1 += intg1 - intg0 + (intg1x > 0) - (intg0x > 0);
    intg1 = intg0;
    intg1x = intg0x;
    error = E_DEC_OVERFLOW;
  } else if (isize0 > isize1) {
    while (isize0-- > isize1) *to++ = (char)mask;
  }
  if (fsize0 < fsize1) {
    frac1 = frac0;
    frac1x = frac0x;
    error = E_DEC_TRUNCATED;
  } else if (fsize0 > fsize1 && frac1x) {
    if (frac0 == frac1) {
      frac1x = frac0x;
      fsize0 = fsize1;
    } else {
      frac1++;
      frac1x = 0;
    }
  }

  /* intg1x part */
  if (intg1x) {
    int i = dig2bytes[intg1x];
    dec1 x = mod_by_pow10(*buf1++, intg1x) ^ mask;
    switch (i) {
      case 1:
        mi_int1store(to, x);
        break;
      case 2:
        mi_int2store(to, x);
        break;
      case 3:
        mi_int3store(to, x);
        break;
      case 4:
        mi_int4store(to, x);
        break;
      default:
        assert(0);
    }
    to += i;
  }

  /* intg1+frac1 part */
  for (stop1 = buf1 + intg1 + frac1; buf1 < stop1; to += sizeof(dec1)) {
    dec1 x = *buf1++ ^ mask;
    assert(sizeof(dec1) == 4);
    mi_int4store(to, x);
  }

  /* frac1x part */
  if (frac1x) {
    dec1 x;
    int i = dig2bytes[frac1x], lim = (frac1 < frac0 ? DIG_PER_DEC1 : frac0x);
    while (frac1x < lim && dig2bytes[frac1x] == i) frac1x++;
    x = div_by_pow10(*buf1, DIG_PER_DEC1 - frac1x) ^ mask;
    switch (i) {
      case 1:
        mi_int1store(to, x);
        break;
      case 2:
        mi_int2store(to, x);
        break;
      case 3:
        mi_int3store(to, x);
        break;
      case 4:
        mi_int4store(to, x);
        break;
      default:
        assert(0);
    }
    to += i;
  }
  if (fsize0 > fsize1) {
    uchar *to_end = orig_to + orig_fsize0 + orig_isize0;

    while (fsize0-- > fsize1 && to < to_end) *to++ = (uchar)mask;
  }
  orig_to[0] ^= 0x80;

  /* Check that we have written the whole decimal and nothing more */
  assert(to == orig_to + orig_fsize0 + orig_isize0);
  return error;
}