NAME

std::wstring_convert::to_bytes - std::wstring_convert::to_bytes

Synopsis

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

// Run this code

#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

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