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std::wstrin...t::to_bytes(3)  C++ Standard Libary std::wstrin...t::to_bytes(3)

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 sup-
       plied 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-sup-
       plied 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"z"

	    // 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>)

http://cppreference.com		  2022.07.31	  std::wstrin...t::to_bytes(3)

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