std::codecvt_mode
From cppreference.com
Defined in header <codecvt>
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enum codecvt_mode { consume_header = 4, |
(since C++11) (deprecated in C++17) (removed in C++26) |
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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
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assume the input is in little-endian byte order (applies to UTF-16 input only, the default is big-endian) |
consume_header
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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
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output the byte order mark at the start of the output sequence |
The recognized byte order marks are:
0xfe 0xff
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UTF-16 big-endian |
0xff 0xfe
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UTF-16 little-endian |
0xef 0xbb 0xbf
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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:
Run this code
#include <codecvt> #include <cwchar> #include <fstream> #include <iostream> #include <locale> #include <string> int main() { // UTF-8 data with BOM std::ofstream{"text.txt"} << "\ufeffz\u6c34\U0001d10b"; // read the UTF-8 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 << (std::wint_t)c << '\n'; }
Output:
0x7a 0x6c34 0x1d10b
See also
converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) | |
(C++11)(deprecated in C++17)(removed in C++26) |
converts between UTF-8 and UCS-2/UCS-4 (class template) |
(C++11)(deprecated in C++17)(removed in C++26) |
converts between UTF-16 and UCS-2/UCS-4 (class template) |
(C++11)(deprecated in C++17)(removed in C++26) |
converts between UTF-8 and UTF-16 (class template) |