std::codecvt_byname is a std::codecvt facet which encapsulates multibyte/wide character conversion rules of a locale specified at its construction.
The standard library is guaranteed to provide the following specializations:
std::codecvt_byname<char, char, std::mbstate_t> identity conversion std::codecvt_byname<char16_t, char, std::mbstate_t>codecvt_byname facet
codecvt_byname facet
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_bynameprotected:
~codecvt_byname();
Destroys the facet.
Inherited from std::codecvt Nested types Type Definitionintern_type internT extern_type externT state_type stateT [edit] Data members Member functions invokes do_out
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_in
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_unshift
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_encoding
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_always_noconv
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_length
std::codecvt<InternT,ExternT,StateT>) [edit] invokes do_max_length
std::codecvt<InternT,ExternT,StateT>) [edit] Protected member functions converts a string from InternT to ExternT, such as when writing to file
std::codecvt<InternT,ExternT,StateT>) [edit] converts a string from ExternT to InternT, such as when reading from file
std::codecvt<InternT,ExternT,StateT>) [edit] generates the termination character sequence of ExternT characters for incomplete conversion
std::codecvt<InternT,ExternT,StateT>) [edit] returns the number of ExternT characters necessary to produce one InternT character, if constant
std::codecvt<InternT,ExternT,StateT>) [edit] tests if the facet encodes an identity conversion for all valid argument values
std::codecvt<InternT,ExternT,StateT>) [edit] calculates the length of the ExternT string that would be consumed by conversion into given InternT buffer
std::codecvt<InternT,ExternT,StateT>) [edit] returns the maximum number of ExternT characters that could be converted into a single InternT character
std::codecvt<InternT,ExternT,StateT>) [edit] Inherited from std::codecvt_base Nested 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 [edit] Example
This example demonstrates reading a GB18030-encoded file using the codecvt facet from a GB18030-aware locale.
#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 'Ã', U+00df
"\xcb\xae" // CJK ideogram 'æ°´' (water), U+6c34
"\x94\x32\xbc\x35"; // musical sign 'ð' (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 << static_cast<unsigned>(c) << '\n';
}
Possible output:
[edit] Defect reportsThe following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 21 C++98 the standard library did not need to providestd::codecvt_byname specializations two specializations are required [edit] See also converts between character encodings, including UTF-8, UTF-16, UTF-32
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