support for string_view about better-enums HOT 6 OPEN

BETTER_ENUMS_CONSTEXPR_ inline bool _names_match(const char *stringizedName,
                                                 std::experimental::string_view &referenceName,
                                                 std::size_t index = 0)
{
    return
        _ends_name(stringizedName[index]) ? index == referenceName.size() :
        index == referenceName.size() ? false :
        stringizedName[index] != referenceName[index] ? false :
        _names_match(stringizedName, referenceName, index + 1);
}

    BETTER_ENUMS_CONSTEXPR_ static _optional                                    \
    _from_string_nothrow(std::experimental::string_view s);                     \
\
    BETTER_ENUMS_CONSTEXPR_ static _optional_index                              \
    _from_string_loop(std::experimental::string_view &s, std::size_t index = 0);\

BETTER_ENUMS_CONSTEXPR_ inline Enum::_optional_index                            \
Enum::_from_string_loop(std::experimental::string_view &s, std::size_t index)   \
{                                                                               \
    return                                                                      \
        index == _size() ? _optional_index() :                                  \
        ::better_enums::_names_match(                                           \
            BETTER_ENUMS_NS(Enum)::_raw_names()[index], s) ?                    \
            _optional_index(index) :                                            \
            _from_string_loop(s, index + 1);                                    \
}                                                                               \
\
BETTER_ENUMS_CONSTEXPR_ inline Enum::_optional                                  \
Enum::_from_string_nothrow(std::experimental::string_view s)                    \
{                                                                               \
    return                                                                      \
        ::better_enums::_map_index<Enum>(                                       \
            BETTER_ENUMS_NS(Enum)::_value_array, _from_string_loop(s));         \
}