bool checkAndGetDateData()

in cpp-ch/local-engine/Functions/FunctionGetDateData.h [103:165]
63 lines of code
28 McCabe index (conditional complexity)

    bool checkAndGetDateData(DB::ReadBuffer & buf, size_t buf_size, T &x, const DateLUTImpl & date_lut, bool & can_be_parsed) const
    {
        auto checkNumbericASCII = [&](DB::ReadBuffer & rb, size_t start, size_t length) -> bool
        {
            for (size_t i = start; i < start + length; ++i)
            {
                if (i >= buf_size || !isNumericASCII(*(rb.position() + i)))
                {
                    return false;
                }
            }
            return true;
        };
        auto checkDelimiter = [&](DB::ReadBuffer & rb, size_t pos) -> bool
        {
            if (pos >= buf_size || *(rb.position() + pos) != '-')
                return false;
            else
                return true;
        };
        bool yearNumberCanbeParsed = checkNumbericASCII(buf, 0, 4) && (buf_size == 4 || checkDelimiter(buf, 4));
        Int16 year = 0;
        if (yearNumberCanbeParsed)
        {
            year = (*(buf.position() + 0) - '0') * 1000 +
                    (*(buf.position() + 1) - '0') * 100 +
                    (*(buf.position() + 2) - '0') * 10 +
                    (*(buf.position() + 3) - '0');
            x = get_year ? year : 0;
        }
        if (!yearNumberCanbeParsed
            || !checkNumbericASCII(buf, 5, 2)
            || !checkDelimiter(buf, 7)
            || !checkNumbericASCII(buf, 8, 2))
        {
            can_be_parsed = yearNumberCanbeParsed;
            return false;
        }
        else
        {
            UInt8 month = (*(buf.position() + 5) - '0') * 10 + (*(buf.position() + 6) - '0');
            if (month <= 0 || month > 12)
                return false;
            UInt8 day = (*(buf.position() + 8) - '0') * 10 + (*(buf.position() + 9) - '0');
            if (day <= 0 || day > 31)
                return false;
            else if (day == 31 && (month == 2 || month == 4 || month == 6 || month == 9 || month == 11))
                return false;
            else if (day == 30 && month == 2)
                return false;
            else
            {
                if (day == 29 && month == 2 && year % 4 != 0)
                    return false;
                else
                {
                    if (get_date)
                        x = date_lut.makeDayNum(year, month, day, -static_cast<Int32>(date_lut.getDayNumOffsetEpoch()));
                    return true;
                }
            }
        }
    }