Function increase_safely

include/utf8cpp/core.h:138–147

    /// Helper for get_sequence_x
    template <typename octet_iterator>
    utf_error increase_safely(octet_iterator& it, octet_iterator end)
    {
        if (++it == end)
            return NOT_ENOUGH_ROOM;

        if (!utf8::internal::is_trail(*it))
            return INCOMPLETE_SEQUENCE;
        
        return UTF8_OK;
    }

    #define UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(IT, END) {utf_error ret = increase_safely(IT, END); if (ret != UTF8_OK) return ret;}