enum class  file_dtypes : std::size_t  {

    FLOAT = 0,            // float
    DOUBLE = 1,           // double
    LONG_DOUBLE = 2,      // long double
    SHORT = 3,            // short int
    USHORT = 4,           // unsigned short int
    INT = 5,              // int
    UINT = 6,             // unsigned int
    LONG = 7,             // long int
    ULONG = 8,            // unsigned long int
    LONG_LONG = 9,        // long long int
    ULONG_LONG = 10,      // unsigned long long int
    CHAR = 11,            // char
    UCHAR = 12,           // unsigned char
    BOOL = 13,            // bool

    STRING = 14,          // std::string
    VSTR32 = 15,          // FixedSizeString<31> == String32
    VSTR64 = 16,          // FixedSizeString<63> == String64
    VSTR128 = 17,         // FixedSizeString<127> == String128
    VSTR512 = 18,         // FixedSizeString<511> == String512
    VSTR1K = 19,          // FixedSizeString<1023> == String1K
    VSTR2K = 20,          // FixedSizeString<2047> == String2K

    DATETIME = 21,        // DateTime
    DATETIME_AME = 22,    // DateTime
    DATETIME_EUR = 23,    // DateTime
    DATETIME_ISO = 24,    // DateTime

    STR_DBL_PAIR = 25,    // std::pair<std::string, double>
    STR_STR_PAIR = 26,    // std::pair<std::string, std::string>
    DBL_DBL_PAIR = 27,    // std::pair<double, double>

    DBL_VEC = 28,         // std::vector<double>
    STR_VEC = 29,         // std::vector<std::string>
    DBL_SET = 30,         // std::set<double>
    STR_SET = 31,         // std::set<std::string>
    STR_DBL_MAP = 32,     // std::map<std::string, double>
    STR_DBL_UNOMAP = 33,  // std::unordered_map<std::string, double>
};