std::codecvt<InternT,ExternT,StateT>::always_noconv, do_always_noconv
From cppreference.com
| Defined in header <locale>
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||
public:
bool always_noconv() const throw();
|
(1) | (until C++11) |
public:
bool always_noconv() const noexcept;
|
(since C++11) | |
protected:
virtual bool do_always_noconv() const throw();
|
(2) | (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.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 <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';
}
Output:
The non-converting char<->char codecvt::always_noconv() returns true
while wchar_t<->char codecvt::always_noconv() returns false