std::codecvt<InternT,ExternT,State>::always_noconv,do_always_noconv (3) - Linux Manuals

std::codecvt<InternT,ExternT,State>::always_noconv,do_always_noconv: std::codecvt<InternT,ExternT,State>::always_noconv,do_always_noconv


std::codecvt<InternT,ExternT,State>::always_noconv,do_always_noconv - std::codecvt<InternT,ExternT,State>::always_noconv,do_always_noconv


Defined in header <locale>
public: (1)
bool always_noconv() const;
protected: (2)
virtual bool do_always_noconv() const;

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.

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


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.


(none) (until C++11)
noexcept specification: (since C++11)


// Run this code

  #include <locale>
  #include <iostream>

  int main()
      std::cout << "The non-converting char<->char codecvt::always_noconv() returns "
                << std::boolalpha
                << std::use_facet<std::codecvt<char, char, std::mbstate_t>>(
                   ).always_noconv() << "\n"
                << "while wchar_t<->char codecvt::always_noconv() returns "
                << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                   ).always_noconv() << "\n";



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