| 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.
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.
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
See also
| converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) | |
| (C++11) | converts between UTF-8 and UCS2/UCS4 (class template) |
| (C++11) | converts between UTF-16 and UCS2/UCS4 (class template) |
| (C++11) | converts between UTF-8 and UTF-16 (class template) |
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