std::codecvt_mode

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Defined in header `<locale>`

enum codecvt_mode { consume_header = 4, generate_header = 2, little_endian = 1 };

The facets std::codecvt_utf8, std::codecvt_utf16, and std::codecvt_utf8_utf16 accept an optional value of type std::codecvt_mode as a template argument, which specifies optional features of the unicode string conversion.

[edit] Constants

Defined in header `<locale>`

Value	Meaning

`little_endian`	assume the input is in little-endian byte order (applies to UTF-16 input only, the default is big-endian)

`consume_header`	consume the byte order mark, if present at the start of input sequence, and (in case of UTF-16), rely on the byte order it specifies for decoding the rest of the input

`generate_header`	output the byte order mark at the start of the output sequence

The recognized byte order marks are:


`0xfe 0xff`	UTF-16 big-endian

`0xff 0xfe`	UTF-16 little-endian

`0xef 0xbb 0xbf`	UTF-8 (no effect on endianness) )

If std::consume_header is not selected when reading a file beginning with byte order mark, the Unicode character U+FEFF (Zero width non-breaking space) will be read as the first character of the string content.

[edit] Example

The following example demonstrates consuming the UTF-8 BOM

#include <fstream>
#include <iostream>
#include <string>
#include <locale>
#include <codecvt>
int main()
{
    // UTF-8 data with BOM
    std::ofstream("text.txt") << u8"\ufeffz\u6c34\U0001d10b";
    // read the UTF8 file, skipping the BOM
    std::wifstream fin("text.txt");
    fin.imbue(std::locale(fin.getloc(),
                          new std::codecvt_utf8<wchar_t, 0x10ffff, std::consume_header>));
    for(wchar_t c; fin.get(c); )
        std::cout << std::hex << std::showbase << c << '\n';
}

Output:

0x7a
0x6c34
0x1d10b

[edit] See also

codecvt

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

codecvt_utf8 (C++11)

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

codecvt_utf16 (C++11)

converts between UTF-16 and UCS2/UCS4
(class template)

codecvt_utf8_utf16 (C++11)

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