std::codecvt_utf16
| Defined in header  <codecvt> | ||
| template< class Elem,           unsigned long Maxcode = 0x10ffff, | ||
std::codecvt_utf16 is a std::codecvt facet which encapsulates conversion between a UTF-16 encoded byte string and UCS2 or UCS4 character string (depending on the type of Elem). This codecvt facet can be used to read and write UTF-16 files in binary mode. 
| Contents | 
[edit] Template Parameters
| Elem | - | either char16_t, char32_t, or wchar_t | 
| Maxcode | - | the largest value of Elemthat this facet will read or write without error | 
| Mode | - | a constant of type std::codecvt_mode | 
[edit] Member functions
|  (constructor) | constructs a new codecvt_utf16facet(public member function) | 
|  (destructor) | destroys a codecvt_utf16facet(public member function) | 
std::codecvt_utf16::codecvt_utf16
| explicit codecvt_utf16( std::size_t refs = 0 ); | ||
Constructs a new std::codecvt_utf16 facet, passes the initial reference counter refs to the base class.
Parameters
| refs | - | the number of references that link to the facet | 
std::codecvt_utf16::~codecvt_utf16
| ~codecvt_utf16(); | ||
Destroys the facet. Unlike the locale-managed facets, this facet's destructor is public.
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(public member function of std::codecvt) | |
| invokes do_in(public member function of std::codecvt) | |
| invokes do_unshift(public member function of std::codecvt) | |
| invokes do_encoding(public member function of std::codecvt) | |
| invokes do_always_noconv(public member function of std::codecvt) | |
| invokes do_length(public member function of std::codecvt) | |
| invokes do_max_length(public member function of std::codecvt) | 
Protected member functions
| [virtual] | converts a string from internT to externT, such as when writing to file (virtual protected member function of std::codecvt) | 
| [virtual] | converts a string from externT to internT, such as when reading from file (virtual protected member function of std::codecvt) | 
| [virtual] | generates the termination character sequence of externT characters for incomplete conversion (virtual protected member function of std::codecvt) | 
| [virtual] | returns the number of externT characters necessary to produce one internT character, if constant (virtual protected member function of std::codecvt) | 
| [virtual] | tests if the facet encodes an identity conversion for all valid argument values (virtual protected member function of std::codecvt) | 
| [virtual] | calculates the length of the externT string that would be consumed by conversion into given internT buffer (virtual protected member function of std::codecvt) | 
| [virtual] | returns the maximum number of externT characters that could be converted into a single internT character (virtual protected member function of std::codecvt) | 
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 | 
[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 UCS2, not UTF-16.
#include <fstream> #include <iostream> #include <string> #include <locale> #include <codecvt> 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>)); for (wchar_t c; fin.get(c); ) std::cout << std::showbase << std::hex << c << '\n'; }
Output:
0x7a 0x6c34 0x1d10b
[edit] See also
| Character conversions | narrow multibyte (char) | UTF-8 (char) | UTF-16 (char16_t) | 
|---|---|---|---|
| UTF-16 | mbrtoc16(one way) | codecvt<char16_t, char, mbstate_t> codecvt_utf8_utf16<char16_t> codecvt_utf8_utf16<char32_t> codecvt_utf8_utf16<wchar_t> | N/A | 
| UCS2 | c16rtomb(one way) | codecvt_utf8<char16_t> | codecvt_utf16<char16_t> | 
| UTF-32/UCS4 (char32_t) | mbrtoc32 / c32rtomb | codecvt<char32_t, char, mbstate_t> codecvt_utf8<char32_t> | codecvt_utf16<char32_t> | 
| UCS2/UCS4 (wchar_t) | No | codecvt_utf8<wchar_t> | codecvt_utf16<wchar_t> | 
| wide (wchar_t) | codecvt<wchar_t, char, mbstate_t> mbsrtowcs / wcsrtombs | No | No | 
| converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) | |
| (C++11) | tags to alter behavior of the standard codecvt facets (enum) | 
| (C++11) | converts between UTF-8 and UCS2/UCS4 (class template) | 
| (C++11) | converts between UTF-8 and UTF-16 (class template) | 


