std::codecvt_utf16

From Cppreference

Defined in header `<codecvt>`

template< class Elem, unsigned long Maxcode = 0x10ffff, std::codecvt_mode Mode = (std::codecvt_mode)0 > class codecvt_utf16;

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.

[edit] Template Parameters

`Elem`	-	either char16_t, char32_t, or wchar_t
`Maxcode`	-	the largest value of `Elem` that this facet will read or write without error
`Mode`	-	a constant of type std::codecvt_mode

[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` / `c16rtombr`	`codecvt`<char16_t, char, mbstate_t> `codecvt_utf8_utf16`<char16_t> `codecvt_utf8_utf16`<char32_t> `codecvt_utf8_utf16`<wchar_t>	N/A
UCS2	No	`codecvt_utf8`<char16_t>	`codecvt_utf16`<char16_t>
UTF-32/UCS4 (char32_t)	`mbrtoc32` / `c32rtombr`	`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> `mbstowcs` / `wcstombs`	No	No

codecvt

converts between character encodings, including UTF-8, UTF-16, UTF-32
(class template)

codecvt_mode (C++11)

tags to alter behavior of the standard codecvt facets
(class)

codecvt_utf8 (C++11)

converts between UTF-8 and UCS2/UCS4
(class template)

codecvt_utf8_utf16 (C++11)

converts between UTF-8 and UTF-16
(class template)