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

| Defined in header | | | | -------------------------------------------------------------------------- | | ------------- | | (1) | | | | public: bool always_noconv() const throw(); | | (until C++11) | | public: bool always_noconv() const noexcept; | | (since C++11) | | (2) | | | | protected: virtual bool do_always_noconv() const throw(); | | (until C++11) | | protected: virtual bool do_always_noconv() const noexcept; | | (since C++11) |

1. Public member function, calls the member function do_always_noconv of the most derived class.

2. Returns true if both do_in() and do_out() return std::codecvt_base::noconv for all valid inputs.

[edit] Return value

true if this conversion facet performs no conversions, false otherwise.

The non-converting specialization std::codecvt<char, char, std::mbstate_t> returns true.

[edit] Notes

This function may be used e.g. in the implementation of std::basic_filebuf::underflow and std::basic_filebuf::overflow to use bulk character copy instead of calling std::codecvt::in or std::codecvt::out if it is known that the locale imbued in the std::basic_filebuf does not perform any conversions.

[edit] Example

Output:

The non-converting char<->char codecvt::always_noconv() returns true while wchar_t<->char codecvt::always_noconv() returns false