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

Since C++11

Header: <locale>

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

# Declarations

public:
bool always_noconv() const throw();

(until C++11)

public:
bool always_noconv() const noexcept;

(since C++11)

protected:
virtual bool do_always_noconv() const throw();

(until C++11)

protected:
virtual bool do_always_noconv() const noexcept;

(since C++11)

# Return value

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

# 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.

# Example

#include <iostream>
#include <locale>
 
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>>(
                    std::locale()
                 ).always_noconv() << '\n'
              << "while wchar_t<->char codecvt::always_noconv() returns "
              << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                    std::locale()
                 ).always_noconv() << '\n';
}