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std::wstring_convert::to_bytes

Defined in header <locale> 
byte_string to_bytes( Elem wchar );
 (1) 
byte_string to_bytes( const Elem* wptr );
 (2) 
byte_string to_bytes( const wide_string& wstr );
 (3) 
byte_string to_bytes( const Elem* first, const Elem* last);
 (4)

Performs wide to multibyte conversion, using the codecvt facet supplied at construction.

1) Converts wchar as if it was a string of length 1, to byte_string.
2) Converts the null-terminated wide character sequence beginning at the wide character pointed to by wptr, to byte_string.
3) Converts the wide string str to byte_string.
4) Converts the wide character sequence [first, last) to byte_string.

In all cases, the conversion begins in initial shift state, unless non-initial starting state was provided to this wstring_convert constructor. The number of characters converted and the final value of the conversion state are remembered and can be accessed with state() and converted().

Return value

A byte_string object containing the results of the wide to multibyte conversion. If the conversion failed and there was a user-supplied byte-error string provided to the constructor of this wstring_convert, returns that byte-error string.

Exceptions

If this wstring_convert object was constructed without a user-supplied byte-error string, throws std::range_error on conversion failure.

Example

#include <iostream>
#include <string>
#include <locale>
#include <codecvt>
#include <iomanip>
 
// utility function for output
void hex_print(const std::string& s)
{
    std::cout << std::hex << std::setfill('0');
    for(unsigned char c : s)
        std::cout << std::setw(2) << static_cast<int>(c) << ' ';
    std::cout << std::dec << '\n';
}
 
int main()
{
    // wide character data
    std::wstring wstr =  L"z\u00df\u6c34\U0001f34c"; // or L"zß水🍌"
 
    // wide to UTF-8
    std::wstring_convert<std::codecvt_utf8<wchar_t>> conv1;
    std::string u8str = conv1.to_bytes(wstr);
    std::cout << "UTF-8 conversion produced " << u8str.size() << " bytes:\n";
    hex_print(u8str);
 
    // wide to UTF-16le
    std::wstring_convert<std::codecvt_utf16<wchar_t, 0x10ffff, std::little_endian>> conv2;
    std::string u16str = conv2.to_bytes(wstr);
    std::cout << "UTF-16le conversion produced " << u16str.size() << " bytes:\n";
    hex_print(u16str);
}

Output:

UTF-8 conversion produced 10 bytes:
7a c3 9f e6 b0 b4 f0 9f 8d 8c 
UTF-16le conversion produced 10 bytes:
7a 00 df 00 34 6c 3c d8 4c df

See also

converts a byte string into a wide string
(public member function)
converts a wide string to narrow multibyte character string, given state
(function)
[virtual]
 converts a string from internT to externT, such as when writing to file
(virtual protected member function of std::codecvt)

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