bool checkDateTimeFormat()

in cpp-ch/local-engine/Functions/SparkFunctionToDateTime.h [57:115]
59 lines of code
33 McCabe index (conditional complexity)

    bool checkDateTimeFormat(DB::ReadBuffer & buf, size_t buf_size, UInt8 & 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 (!isNumericASCII(*(rb.position() + i)))
                    return false;
            }
            return true;
        };
        auto checkDelimiter = [&](DB::ReadBuffer & rb, size_t pos, char delim) -> bool
        {
            if (*(rb.position() + pos) != delim)
                return false;
            else
                return true;
        };
        if ((buf_size == 10 || buf_size == 11)
            && checkNumbericASCII(buf, 0, 4) && checkDelimiter(buf, 4, '-')
            && checkNumbericASCII(buf, 5, 2) && checkDelimiter(buf, 7, '-')
            && checkNumbericASCII(buf, 8, 2))
        {
            if (buf_size == 10)
                return true;
            else if (*(buf.position() + 10) != ' ')
                can_be_parsed = 0;
            return false;
        }
        else if ((buf_size == 19 || buf_size == 20) 
            && (checkNumbericASCII(buf, 0, 4) && checkDelimiter(buf, 4, '-')
            && checkNumbericASCII(buf, 5, 2) && checkDelimiter(buf, 7, '-')
            && checkNumbericASCII(buf, 8, 2) && checkDelimiter(buf, 10, ' ')
            && checkNumbericASCII(buf, 11, 2) && checkDelimiter(buf, 13, ':')
            && checkNumbericASCII(buf, 14, 2) && checkDelimiter(buf, 16, ':')
            && checkNumbericASCII(buf, 17, 2)))
        {
            if (buf_size == 19)
                return true;
            else
                return *(buf.position() + 19) == '.';
        }
        else if (buf_size < 4 || !isNumericASCII(*(buf.position() + buf_size - 1)))
        {
            can_be_parsed = 0;
            return false;
        }
        else if (buf_size < 19)
            return false;
        else if (buf_size > 20)
        {
            for (size_t i = 20; i < buf_size; ++i)
            {
                if (!isNumericASCII(*(buf.position() + i)))
                    return false;
            }
        }
        return true;
    }