Method do_unshift

test/test_codecvt.hpp:67–67

    }

    virtual std::codecvt_base::result do_unshift(std::mbstate_t&, char* /*from*/, char* /*to*/, char*& /*next*/) const { return ok; }
    virtual int do_length(std::mbstate_t&, const char* /*from*/, const char* /*from_end*/, std::size_t /*max*/) const { return 0; }
    virtual int do_max_length() const throw() { return 0; }
};