std::codecvt<InternT,ExternT,StateT>::unshift, do_unshift
From cppreference.com
| Defined in header <locale>
|
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| public: result unshift( StateT& state, ExternT* to, ExternT* to_end, |
(1) | |
| protected: virtual result do_unshift( StateT& state, ExternT* to, ExternT* to_end, |
(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.Contents |
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 |
|---|---|---|---|
| LWG 305 | C++98 | std::codecvt<wchar_t, char, std::mbstate_t>::do_unshift was required not to write any character |
not required |
| LWG 380 | C++98 | the meaning of returning partial was 'more characters need to be supplied to complete termination', but no character is supplied |
corrected to indicating insufficient buffer space |
| LWG 381 | C++98 | state was not required to be valid, and error is returned if state is invalid |
state is required to be valid, and returning error indicates an error |
| LWG 664 | C++98 | std::codecvt<char, char, std::mbstate_t>::do_unshift was required not to write any character |
not required |
| LWG 665 | C++98 | std::codecvt<char, char, std::mbstate_t>::do_unshift was required to return noconv |
not required |
See also
| converts a wide character to its multibyte representation, given state (function) | |
| [virtual] |
converts a string from InternT to ExternT, such as when writing to file (virtual protected member function) |
