NAME

std::codecvt::always_noconv,do_always_noconv - std::codecvt::always_noconv,do_always_noconv

Synopsis

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

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

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

// 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>>(
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";

}

Output:

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