ulonglong my_strntoull10rnd_8bit()

in mysql_strings/ctype-simple.cc [1228:1439]

• 176 lines of code
• 66 McCabe index (conditional complexity)

ulonglong my_strntoull10rnd_8bit(const CHARSET_INFO *cs [[maybe_unused]],
                                 const char *str, size_t length,
                                 int unsigned_flag, const char **endptr,
                                 int *error) {
  const char *dot, *end9, *beg, *end = str + length;
  ulonglong ull;
  ulong ul;
  uchar ch;
  int shift = 0, digits = 0, addon;
  bool negative;

  /* Skip leading spaces and tabs */
  for (; str < end && (*str == ' ' || *str == '\t'); str++)
    ;

  if (str >= end) goto ret_edom;

  if ((negative = (*str == '-')) || *str == '+') /* optional sign */
  {
    if (++str == end) goto ret_edom;
  }

  beg = str;
  end9 = (str + 9) > end ? end : (str + 9);
  /* Accumulate small number into ulong, for performance purposes */
  for (ul = 0; str < end9 && (ch = (uchar)(*str - '0')) < 10; str++) {
    ul = ul * 10 + ch;
  }

  if (str >= end) /* Small number without dots and expanents */
  {
    *endptr = str;
    if (negative) {
      if (unsigned_flag) {
        *error = ul ? MY_ERRNO_ERANGE : 0;
        return 0;
      } else {
        *error = 0;
        return (ulonglong)(longlong) - (long)ul;
      }
    } else {
      *error = 0;
      return (ulonglong)ul;
    }
  }

  digits = (int)(str - beg);

  /* Continue to accumulate into ulonglong */
  for (dot = nullptr, ull = ul; str < end; str++) {
    if ((ch = (uchar)(*str - '0')) < 10) {
      if (ull < CUTOFF || (ull == CUTOFF && ch <= CUTLIM)) {
        ull = ull * 10 + ch;
        digits++;
        continue;
      }
      /*
        Adding the next digit would overflow.
        Remember the next digit in "addon", for rounding.
        Scan all digits with an optional single dot.
      */
      if (ull == CUTOFF) {
        ull = ULLONG_MAX;
        addon = 1;
        str++;
      } else
        addon = (*str >= '5');
      if (!dot) {
        for (; str < end && (ch = (uchar)(*str - '0')) < 10; shift++, str++)
          ;
        if (str < end && *str == '.') {
          str++;
          for (; str < end && (ch = (uchar)(*str - '0')) < 10; str++)
            ;
        }
      } else {
        shift = (int)(dot - str);
        for (; str < end && (ch = (uchar)(*str - '0')) < 10; str++)
          ;
      }
      goto exp;
    }

    if (*str == '.') {
      if (dot) {
        /* The second dot character */
        goto dotshift;
      } else {
        dot = str + 1;
      }
      continue;
    }

    /* Unknown character, exit the loop */
    break;
  }

dotshift:
  shift = dot ? (int)(dot - str) : 0; /* Right shift */
  addon = 0;

exp: /* [ E [ <sign> ] <unsigned integer> ] */

  if (!digits) {
    str = beg;
    goto ret_edom;
  }

  if (str < end && (*str == 'e' || *str == 'E')) {
    str++;
    if (str < end) {
      longlong negative_exp, exponent;
      if ((negative_exp = (*str == '-')) || *str == '+') {
        if (++str == end) goto check_shift_overflow;
      }
      for (exponent = 0; str < end && (ch = (uchar)(*str - '0')) < 10; str++) {
        if (exponent <= (std::numeric_limits<longlong>::max() - ch) / 10)
          exponent = exponent * 10 + ch;
        else
          goto ret_too_big;
      }
      shift += negative_exp ? -exponent : exponent;
    }
  }

  if (shift == 0) /* No shift, check addon digit */
  {
    if (addon) {
      if (ull == ULLONG_MAX) goto ret_too_big;
      ull++;
    }
    goto ret_sign;
  }

  if (shift < 0) /* Right shift */
  {
    ulonglong d, r;

    if (shift == INT_MIN32 || -shift >= DIGITS_IN_ULONGLONG)
      goto ret_zero; /* Exponent is a big negative number, return 0 */

    d = d10[-shift];
    r = ull % d;
    ull /= d;
    if (r >= d / 2) ull++;
    goto ret_sign;
  }

check_shift_overflow:
  if (shift > DIGITS_IN_ULONGLONG) /* Huge left shift */
  {
    if (!ull) goto ret_sign;
    goto ret_too_big;
  }

  for (; shift > 0; shift--, ull *= 10) /* Left shift */
  {
    if (ull > CUTOFF) goto ret_too_big; /* Overflow, number too big */
  }

ret_sign:
  *endptr = str;

  if (!unsigned_flag) {
    if (negative) {
      if (ull > (ulonglong)LLONG_MIN) {
        *error = MY_ERRNO_ERANGE;
        return (ulonglong)LLONG_MIN;
      }
      *error = 0;
      if (ull == static_cast<ulonglong>(LLONG_MIN))
        return static_cast<ulonglong>(LLONG_MIN);
      return (ulonglong) - (longlong)ull;
    } else {
      if (ull > (ulonglong)LLONG_MAX) {
        *error = MY_ERRNO_ERANGE;
        return (ulonglong)LLONG_MAX;
      }
      *error = 0;
      return ull;
    }
  }

  /* Unsigned number */
  if (negative && ull) {
    *error = MY_ERRNO_ERANGE;
    return 0;
  }
  *error = 0;
  return ull;

ret_zero:
  *endptr = str;
  *error = 0;
  return 0;

ret_edom:
  *endptr = str;
  *error = MY_ERRNO_EDOM;
  return 0;

ret_too_big:
  *endptr = str;
  *error = MY_ERRNO_ERANGE;
  if (unsigned_flag) {
    if (negative) return 0;
    return ULLONG_MAX;
  } else {
    if (negative) return LLONG_MIN;
    return LLONG_MAX;
  }
}