BaseX XML database in C++ encoding issue - c++

Question

I work with Base X and try to integrate a XML database with c++ on Windows 7. I use the BaseXclient API from https://github.com/JohnLeM/BasexCPPAPI/
it contains the pugixml parser and uses the boost lib. I got it to work but I have issues with the encoding. The xml dokuments in my database are utf-8 and contain some letters and symbols that are not displayed correctly on console output(like ä and °).
I set the console code page with chcp 65001.
I changed the locale with std::setlocale(LC_ALL, ""); in c++ and when I cout these letters and symbols directly in my Programm and not from the database they are displayed correctly. The database output also changed but is still wrong.
I also set the pugi parser with pugi::xml_encoding::encoding_utf8; but the database output is not affected. here is a code example from the string list interface:
virtual ~my_string_list_interface() {};
my_string_list_interface(const std::string& DBHOST, const std::string& DBPORT, const std::string& DBUSER,const std::string& DBPASSWD) : base_type(DBHOST,DBPORT,DBUSER,DBPASSWD) {};
virtual my_string_list get(string query,int stage){
my_string_list my_string_list_;
pugi::xml_encoding::encoding_auto;
pugi::xml_parse_result parse_;
pugi::xml_document doc;
string results = session().execute("XQUERY "+query);
parse_ = doc.load(results.c_str());
pugi::xpath_node_set is = doc.select_nodes("/record/mid");
The API uses boost streambuf to get the data. The code from boost streambuf looks like that:
std::string read_streambuffer(){return read_streambuffer(response_);};
std::string read_streambuffer(boost::asio::streambuf & response)
{
std::string results;
boost::system::error_code error;
boost::asio::streambuf::const_buffers_type bufs = response.data();
std::size_t size(0);
std::string line;
auto ptr_b = boost::asio::buffers_begin(bufs);
for(; ptr_b != boost::asio::buffers_end(bufs); ++ptr_b, ++ size)
{if (*ptr_b != 0) {line.push_back(*ptr_b);} else if (size > 1) break; };
response.consume(size);
return line;
};
Is there a way to specify the encoding for the buffer stream or string? I use a string list for the database output. should I use wstring or is there something i missed?
Thanks!