std::codecvt_byname (3) - Linux Manuals

std::codecvt_byname: std::codecvt_byname

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 multibyte/wide character conversion rules of a locale specified at its construction.
Four specializations are provided by the standard library

Defined in header <locale>
std::codecvt_byname<char, char, std::mbstate_t> identity conversion
std::codecvt_byname<char16_t, char, std::mbstate_t> conversion between UTF-16 and UTF-8 (since C++11)(deprecated in C++20)
std::codecvt_byname<char16_t, char8_t, std::mbstate_t> conversion between UTF-16 and UTF-8 (since C++20)
std::codecvt_byname<char32_t, char, std::mbstate_t> conversion between UTF-32 and UTF-8 (since C++11)(deprecated in C++20)
std::codecvt_byname<char32_t, char8_t, std::mbstate_t> conversion between UTF-32 and UTF-8 (since C++20)
std::codecvt_byname<wchar_t, char, std::mbstate_t> locale-specific conversion between wide string and narrow character sets

Member functions

              constructs a new codecvt_byname facet
constructor (public member function)
              destroys a codecvt_byname facet
destructor (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 = 0 ); (since C++11)

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. Otherwise, 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 type 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,ExternT,State>)
              invokes do_in
in (public member function of std::codecvt<InternT,ExternT,State>)
              invokes do_unshift
unshift (public member function of std::codecvt<InternT,ExternT,State>)
              invokes do_encoding
encoding (public member function of std::codecvt<InternT,ExternT,State>)
              invokes do_always_noconv
always_noconv (public member function of std::codecvt<InternT,ExternT,State>)
              invokes do_length
length (public member function of std::codecvt<InternT,ExternT,State>)
              invokes do_max_length
max_length (public member function of std::codecvt<InternT,ExternT,State>)

Protected member functions

do_out converts a string from internT to externT, such as when writing to file
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_in converts a string from externT to internT, such as when reading from file
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_unshift generates the termination character sequence of externT characters for incomplete conversion
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_encoding returns the number of externT characters necessary to produce one internT character, if constant
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_always_noconv tests if the facet encodes an identity conversion for all valid argument values
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_length calculates the length of the externT string that would be consumed by conversion into given internT buffer
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

do_max_length returns the maximum number of externT characters that could be converted into a single internT character
                 (virtual protected member function of std::codecvt<InternT,ExternT,State>)
[virtual]

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 <iostream>
  #include <fstream>
  #include <string>
  #include <locale>

  int main()
  {
      // GB18030 narrow multibyte encoding
      std::ofstream("text.txt") << "\x7a" // letter 'z', U+007a
                                   "\x81\x30\x89\x38" // letter 'ß', U+00df
                                   "\xcb\xae" // CJK ideogram '水' (water), U+6c34
                                   "\x94\x32\xbc\x35"; // musical sign '𝄋' (segno), U+1d10b
      std::wifstream fin("text.txt");
      fin.imbue(std::locale(fin.getloc(),
                new std::codecvt_byname<wchar_t, char, std::mbstate_t>("zh_CN.gb18030")));
      for (wchar_t c; fin.get(c); )
          std::cout << std::hex << std::showbase << c << '\n';
  }

Output:

  0x7a
  0xdf
  0x6c34
  0x1d10b