std::codecvt_utf16 - cppreference.com (original) (raw)

std::codecvt_utf16 is a std::codecvt facet which encapsulates conversion between a UTF-16 encoded byte string and UCS-2 or UTF-32 character string (depending on the type of Elem). This std::codecvt facet can be used to read and write UTF-16 files in binary mode.

UCS-2 is an archaic encoding that is a subset of UTF-16, which encodes scalar values in the range U+0000-U+FFFF (Basic Multilingual Plane) only.

Contents

• 1 Template Parameters
• 2 Member functions
• 3 std::codecvt_utf16::codecvt_utf16
  • 3.1 Parameters
• 4 std::codecvt_utf16::~codecvt_utf16
• 5 Inherited from std::codecvt
  • 5.1 Nested types
  • 5.2 Data members
  • 5.3 Member functions
  • 5.4 Protected member functions
• 6 Inherited from std::codecvt_base
  • 6.1 Notes
  • 6.2 Example
  • 6.3 Defect reports
  • 6.4 See also

[edit] Template Parameters

[edit] Member functions

| | constructs a new codecvt_utf16 facet (public member function) | | ----------------------------------------------------------------- | | | destroys a codecvt_utf16 facet (public member function) |

std::codecvt_utf16::codecvt_utf16

Constructs a new std::codecvt_utf16 facet, passes the initial reference counter refs to the base class.

Parameters

std::codecvt_utf16::~codecvt_utf16

Destroys the facet. Unlike the locale-managed facets, this facet's destructor is public.

Inherited from std::codecvt

Nested types

[edit] Data members

Member functions

Protected member functions

Inherited from std::codecvt_base

[edit] Notes

Although the standard requires that this facet works with UCS-2 when the size of Elem is 16 bits, some implementations use UTF-16 instead, making this a non-converting locale. The term "UCS-2" was deprecated and removed from ISO 10646.

[edit] Example

The following example demonstrates decoding of UTF-16le file on a system with 32-bit wchar_t. On a system with 16-bit wchar_t, decoding of the third character will fail because std::codecvt_utf16<char16_t> produces UCS-2, not UTF-16.

#include #include #include #include #include #include   void prepare_file() { // UTF-16le data (if host system is little-endian) char16_t utf16le[4] = {0x007a, // latin small letter 'z' U+007a 0x6c34, // CJK ideograph "water" U+6c34 0xd834, 0xdd0b}; // musical sign segno U+1d10b
  // store in a file std::ofstream fout("text.txt"); fout.write(reinterpret_cast<char*>(utf16le), sizeof utf16le); }   int main() { prepare_file(); // open as a byte stream std::wifstream fin("text.txt", std::ios::binary); // apply facet fin.imbue(std::locale(fin.getloc(), new std::codecvt_utf16<wchar_t, 0x10ffff, std::little_endian>));   wchar_t c = 0; for (std::cout << std::showbase << std::hex; fin.get(c); std::cout << static_cast<std::wint_t>(c) << '\n'); }

Output:

[edit] Defect reports

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

[edit] See also

| | converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) [edit] | | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | (C++11)(deprecated in C++17)(removed in C++26) | tags to alter behavior of the standard codecvt facets (enum) [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-8 and UTF-16 (class template) [edit] |