std::codecvt<InternT,ExternT,State>::always_noconv, do_always_noconv
Defined in header <locale> |
||
|---|---|---|
| (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.
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
#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
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https://en.cppreference.com/w/cpp/locale/codecvt/always_noconv
