namespace std {
    enum codecvt_mode {
        consume_header = 4,
        generate_header = 2,
        little_endian = 1
    };
 
    template<class Elem,
             unsigned long Maxcode = 0x10ffff,
             codecvt_mode Mode = (codecvt_mode)0>
    class codecvt_utf8;
 
    template<class Elem,
             unsigned long Maxcode = 0x10ffff,
             codecvt_mode Mode = (codecvt_mode)0>
    class codecvt_utf16;
 
    template<class Elem,
             unsigned long Maxcode = 0x10ffff,
             codecvt_mode Mode = (codecvt_mode)0>
    class codecvt_utf8_utf16;
}

template< class Elem,
          unsigned long Maxcode = 0x10ffff,
          codecvt_mode Mode = (codecvt_mode)0 >
class codecvt_utf8 : public codecvt<Elem, char, mbstate_t> {
 public:
    explicit codecvt_utf8(size_t refs = 0);
    ~codecvt_utf8();
};

template< class Elem,
          unsigned long Maxcode = 0x10ffff,
          codecvt_mode Mode = (codecvt_mode)0 >
class codecvt_utf16 : public codecvt<Elem, char, mbstate_t> {
 public:
    explicit codecvt_utf16(size_t refs = 0);
    ~codecvt_utf16();
};

template< class Elem,
          unsigned long Maxcode = 0x10ffff,
          codecvt_mode Mode = (codecvt_mode)0 >
class codecvt_utf8_utf16 : public codecvt<Elem, char, mbstate_t> {
 public:
    explicit codecvt_utf8_utf16(size_t refs = 0);
    ~codecvt_utf8_utf16();
};