std::codecvt<InternT,ExternT,StateT>::unshift, do_unshift - cppreference.com (original) (raw)

| Defined in header | | | | -------------------------------------------------------------------------------------------------------------------- | --- | | | public: result unshift( StateT& state, ExternT* to, ExternT* to_end, ExternT*& to_next ) const; | (1) | | | protected: virtual result do_unshift( StateT& state, ExternT* to, ExternT* to_end, ExternT*& to_next ) const; | (2) | |

  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.

[edit] 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

[edit] Notes

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

[edit] Example

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 305 C++98 std::codecvt<wchar_t, char, std::mbstate_t>::do_unshiftwas required not to write any character not required
LWG 380 C++98 the meaning of returning partial was 'more characters need tobe supplied to complete termination', but no character is supplied corrected to indicatinginsufficient buffer space
LWG 381 C++98 state was not required to be valid, anderror is returned if state is invalid state is required to be valid, andreturning error indicates an error
LWG 664 C++98 std::codecvt<char, char, std::mbstate_t>::do_unshiftwas required not to write any character not required
LWG 665 C++98 std::codecvt<char, char, std::mbstate_t>::do_unshiftwas required to return noconv not required

[edit] See also

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