std::codecvt_byname(3) C++ Standard Libary std::codecvt_byname(3) NAME std::codecvt_byname - std::codecvt_byname Synopsis Defined in header <locale> template< class InternT, class ExternT, class State > class codecvt_byname : public std::codecvt<InternT, ExternT, State>; std::codecvt_byname is a std::codecvt facet which encapsulates multi- byte/wide character conversion rules of a locale specified at its construction. Specializations The standard library is guaranteed to provide the following specializa- tions: Defined in header <locale> std::codecvt_byname<char, char, identity conversion std::mbstate_t> std::codecvt_byname<char16_t, char, conversion between UTF-16 and UTF-8 (since std::mbstate_t> C++11)(deprecated in C++20) std::codecvt_byname<char16_t, char8_t, conversion between UTF-16 and UTF-8 (since std::mbstate_t> C++20) std::codecvt_byname<char32_t, char, conversion between UTF-32 and UTF-8 (since std::mbstate_t> C++11)(deprecated in C++20) std::codecvt_byname<char32_t, char8_t, conversion between UTF-32 and UTF-8 (since std::mbstate_t> C++20) std::codecvt_byname<wchar_t, char, locale-specific conversion be- tween wide std::mbstate_t> string and narrow character sets Member functions constructor constructs a new codecvt_byname facet (public member function) destructor destroys a codecvt_byname facet (protected member function) std::codecvt_byname::codecvt_byname explicit codecvt_byname( const char* name, std::size_t refs = 0 ); explicit codecvt_byname( const std::string& name, std::size_t refs = (since C++11) 0 ); Constructs a new std::codecvt_byname facet for a locale with name. refs is used for resource management: if refs == 0, the implementation destroys the facet, when the last std::locale object holding it is destroyed. Other- wise, the object is not destroyed. Parameters name - the name of the locale refs - the number of references that link to the facet std::codecvt_byname::~codecvt_byname protected: ~codecvt_byname(); Destroys the facet. Inherited from std::codecvt Member types Member name Definition intern_type internT extern_type externT state_type stateT Member objects Member name Type id (static) std::locale::id Member functions invokes do_out out (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_in in (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_unshift unshift (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_encoding encoding (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_always_noconv always_noconv (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_length length (public member function of std::codecvt<InternT,Ex- ternT,StateT>) invokes do_max_length max_length (public member function of std::codecvt<InternT,Ex- ternT,StateT>) Protected member functions converts a string from InternT to ExternT, such as when writing to do_out file [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) converts a string from ExternT to InternT, such as when reading do_in from file [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) generates the termination character sequence of ExternT characters do_unshift for incomplete conversion [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) returns the number of ExternT characters necessary to produce one do_encoding InternT character, if constant [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) tests if the facet encodes an identity conversion for all valid do_always_noconv argument values [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) calculates the length of the ExternT string that would be consumed do_length by conversion into given InternT buffer [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) returns the maximum number of ExternT characters that could be do_max_length converted into a single InternT character [virtual] (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) Inherited from std::codecvt_base Member type Definition enum result { ok, partial, error, noconv }; Unscoped enumeration type Enumeration constant Definition ok conversion was completed with no error partial not all source characters were converted error encountered an invalid character noconv no conversion required, input and output types are the same Example This example demonstrates reading a GB18030-encoded file using the codecvt facet from a GB18030-aware locale. // Run this code #include <fstream> #include <iostream> #include <locale> #include <string> int main() { // GB18030 narrow multibyte encoding std::ofstream("text.txt") << "\x7a" // letter 'z', U+007a "\x81\x30\x89\x38" // letter 'A', U+00df "\xcb\xae" // CJK ideogram 'ae<degree>'' (water), U+6c34 "\x94\x32\xbc\x35"; // musical sign 'dh' (segno), U+1d10b std::wifstream fin("text.txt"); fin.imbue(std::locale(fin.getloc(), new std::codecvt_byname<wchar_t, char, std::mb- state_t>("zh_CN.gb18030"))); for (wchar_t c; fin.get(c);) std::cout << std::hex << std::showbase << static_cast<unsigned>(c) << '\n'; } Possible output: 0x7a 0xdf 0x6c34 0x1d10b Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior the standard library did not need to two spe- cializations are LWG 21 C++98 provide required any std::codecvt_byname specializations See also codecvt converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) http://cppreference.com 2024.06.10 std::codecvt_byname(3)
NAME | Synopsis | Specializations | Member functions | Parameters | Member types | Member objects | Member functions | Protected member functions | Example | Possible output: | See also
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