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# std::codecvt::unshift, do_unshift

From cppreference.com
< cpp‎ | locale‎ | codecvt

Defined in header `<locale>` |  |
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` | unspecified error occurred
`noconv` | the encoding is not state-dependent, no termination sequence necessary

The non-converting specialization std::codecvt<char, char, std::mbstate_t> always returns std::codecvt_base::noconv

### [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

| This section is incomplete Reason: no example

### [edit] See also

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

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- Todo no example