std::codecvt::unshift,do_unshift(3)

NAME
std::codecvt::unshift,do_unshift - std::codecvt::unshift,do_unshift

Synopsis
   Defined in header <locale>
   public:
   result unshift( StateT& state, ExternT* to, ExternT* to_end, (1)
                   ExternT*& to_next ) const;
   protected:
   virtual result do_unshift( StateT& state, ExternT* to, ExternT* to_end, (2)
                        ExternT*& to_next ) const;
   1) Public member function, calls the member function do_unshift of the most derived
   class.
   2) If the encoding represented by this codecvt facet is state-dependent, and state
   represents a conversion state that is not the initial shift state, writes the
   characters necessary to return to the initial shift state. The characters are
   written to a character array whose first element is pointed to by to. No more than
   to_end - to characters are written. The parameter to_next is updated to point one
   past the last character written.

Return value
   A value of type std::codecvt_base::result, indicating the success status as follows:
   ok all necessary characters were written. state now represents initial shift
           state
   partial not enough space in the output buffer. to_next == to_end
   error an unspecified error has occurred
   noconv the encoding is not state-dependent, no termination sequence necessary

Notes
   This function is called by std::basic_filebuf::close() and in other situations when
   finalizing a state-dependent multibyte character sequence.

Example
    This section is incomplete
    Reason: no example
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
     DR Applied to Behavior as published Correct behavior
                      std::codecvt<wchar_t, char,
   LWG 305 C++98 std::mbstate_t>::do_unshift not required
                      was required not to write any character
                      the meaning of returning partial was 'more corrected to
   LWG 380 C++98 characters need to indicating
                      be supplied to complete termination', but no insufficient buffer
                      character is supplied space
                        state is required to
   LWG 381 C++98 state was not required to be valid, and be valid, and
                      error is returned if state is invalid returning error
                        indicates an error
                      std::codecvt<char, char,
   LWG 664 C++98 std::mbstate_t>::do_unshift not required
                      was required not to write any character
                      std::codecvt<char, char,
   LWG 665 C++98 std::mbstate_t>::do_unshift not required
                      was required to return noconv

See also
   wcrtomb converts a wide character to its multibyte representation, given state
             (function)
   do_out converts a string from InternT to ExternT, such as when writing to file
   [virtual] (virtual protected member function)

Category:
     * Todo no example