std::codecvt - cppreference.com (original) (raw)

| | | | | ---------------------------------------------------------------------- | | | | template< class InternT, class ExternT, class StateT > class codecvt; | | |

Class template std::codecvt encapsulates conversion of character strings, including wide and multibyte, from one encoding to another. All file I/O operations performed through std::basic_fstream<CharT> use the std::codecvt<CharT, char, std::mbstate_t> facet of the locale imbued in the stream.

Inheritance diagram

Contents

• 1 Specializations
• 2 Nested types
• 3 Data members
• 4 Member functions
• 5 Protected member functions
• 6 Inherited from std::codecvt_base
  • 6.1 Example
  • 6.2 Defect reports
  • 6.3 See also

[edit] Specializations

The standard library is guaranteed to provide the following specializations (they are required to be implemented by any locale object):

[edit] Nested types

[edit] Data members

[edit] Member functions

[edit] Protected member functions

Inherited from std::codecvt_base

[edit] Example

The following examples reads a UTF-8 file using a locale which implements UTF-8 conversion in codecvt<wchar_t, char, std::mbstate_t> and converts a UTF-8 string to UTF-16 using one of the standard specializations of std::codecvt.

#include #include #include #include #include #include #include   // utility wrapper to adapt locale-bound facets for wstring/wbuffer convert template struct deletable_facet : Facet { template<class... Args> deletable_facet(Args&&... args) : Facet(std::forward(args)...) {} ~deletable_facet() {} };   int main() { // UTF-8 narrow multibyte encoding std::string data = reinterpret_cast<const char*>(+u8"z\u00df\u6c34\U0001f34c"); // or reinterpret_cast<const char*>(+u8"zß水🍌") // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c"   std::ofstream("text.txt") << data;   // using system-supplied locale's codecvt facet std::wifstream fin("text.txt"); // reading from wifstream will use codecvt<wchar_t, char, std::mbstate_t> // this locale's codecvt converts UTF-8 to UCS4 (on systems such as Linux) fin.imbue(std::locale("en_US.UTF-8")); std::cout << "The UTF-8 file contains the following UCS4 code units:\n" << std::hex; for (wchar_t c; fin >> c;) std::cout << "U+" << std::setw(4) << std::setfill('0') << static_cast(c) << ' ';   // using standard (locale-independent) codecvt facet std::wstring_convert< deletable_facet<std::codecvt<char16_t, char, std::mbstate_t>>, char16_t> conv16; std::u16string str16 = conv16.from_bytes(data);   std::cout << "\n\nThe UTF-8 file contains the following UTF-16 code units:\n" << std::hex; for (char16_t c : str16) std::cout << "U+" << std::setw(4) << std::setfill('0') << static_cast(c) << ' '; std::cout << '\n'; }

Output:

The UTF-8 file contains the following UCS4 code units: U+007a U+00df U+6c34 U+1f34c   The UTF-8 file contains the following UTF-16 code units: U+007a U+00df U+6c34 U+d83c U+df4c

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also

| | defines character conversion errors (class) [edit] | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | represents the system-supplied std::codecvt for the named locale (class template) [edit] | | | (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-8 and UCS-2/UCS-4 (class template) [edit] | | (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-16 and UCS-2/UCS-4 (class template) [edit] | | (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-8 and UTF-16 (class template) [edit] |