#include <locale>
#include <codecvt>
#include <fstream>
#include <cassert>

#include <iostream>
#include <sstream>


struct test_buf
    : public std::wbuffer_convert<std::codecvt_utf8<wchar_t> >
{
    typedef std::wbuffer_convert<std::codecvt_utf8<wchar_t> > base;
    typedef base::char_type   char_type;
    typedef base::int_type    int_type;
    typedef base::traits_type traits_type;

    explicit test_buf(std::streambuf* sb) : base(sb) {}

    char_type* pbase() const {return base::pbase();}
    char_type* pptr()  const {return base::pptr();}
    char_type* epptr() const {return base::epptr();}
    void gbump(int n) {base::gbump(n);}

    virtual int_type overflow(int_type c = traits_type::eof()) {return base::overflow(c);}
};

int main() {
    std::ostringstream out;
    test_buf f(out.rdbuf());
    assert(f.sputc(0x4E51) == 0x4E51);
    assert(f.sputc(0x4E52) == 0x4E52);
    assert(f.sputc(0x4E53) == 0x4E53);

    std::string s = out.str();
    std::cout << "s = '" << s << "', s.size() = " << s.size() << std::endl;
}