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std::mbrtoc16(3)	       C++ Standard Libary		std::mbrtoc16(3)

NAME
     std::mbrtoc16 - std::mbrtoc16

Synopsis
	Defined in header <cuchar>
	std::size_t mbrtoc16( char16_t* pc16,

			      const char* s,	     (since C++11)
			      std::size_t n,

			      std::mbstate_t* ps );

	Converts  a  narrow  multibyte character to UTF-16 character representa-
     tion.

	If s is not a null pointer, inspects at most n bytes  of  the  multibyte
     character
	string,  beginning with the byte pointed to by s to determine the number
     of bytes
	necessary to complete the next multibyte character (including any  shift
     sequences).
	If  the  function  determines  that the next multibyte character in s is
     complete and
	valid, converts it to the corresponding 16-bit character and  stores  it
     in *pc16 (if
	pc16 is not null).

	If  the  multibyte  character  in *s corresponds to a multi-char16_t se-
     quence (e.g. a
	surrogate pair in UTF-16), then after the first call to  this  function,
     *ps is
	updated  in such a way that the next call to mbrtoc16 will write out the
     additional
	char16_t, without considering *s.

	If s is a null pointer, the values of n and pc16  are  ignored	and  the
     call is
	equivalent to std::mbrtoc16(nullptr, "", 1, ps).

	If  the  wide  character  produced is the null character, the conversion
     state *ps
	represents the initial shift state.

	The multibyte encoding used by this function is specified  by  the  cur-
     rently active C
	locale.

Parameters
	pc16 - pointer to the location where the resulting 16-bit character will
     be written
	s    - pointer to the multibyte character string used as input
	n    - limit on the number of bytes in s that can be examined
	ps   - pointer to the conversion state object used when interpreting the
     multibyte
	       string

Return value
	The first of the following that applies:

	  *  0	if  the  character converted from s (and stored in *pc16 if non-
     null) was the
	    null character.
	  * the number of bytes [1...n] of the multibyte character  successfully
     converted
	    from s.
	  * -3 if the next char16_t from a multi-char16_t character (e.g. a sur-
     rogate pair)
	    has now been written to *pc16. No bytes are processed from the input
     in this
	    case.
	  *  -2  if the next n bytes constitute an incomplete, but so far valid,
     multibyte
	    character. Nothing is written to *pc16.
	  * -1 if encoding error occurs. Nothing is written to *pc16, the  value
     EILSEQ is
	    stored in errno and the value of *ps is unspecified.

Example
     // Run this code

      #include <clocale>
      #include <cstring>
      #include <cuchar>
      #include <cwchar>
      #include <iomanip>
      #include <iostream>

      int main()
      {
	  std::setlocale(LC_ALL, "en_US.utf8");

	  std::string str = "z\u00df\u6c34\U0001F34C"; // or u8"zAae<degree>'dh"

	  std::cout << "Processing " << str.size() << " bytes: [ " << std::show-
     base;
	  for (unsigned char c: str)
	      std::cout << std::hex << +c << ' ';
	  std::cout << "]\n";

	  std::mbstate_t state{}; // zero-initialized to initial state
	  char16_t c16;
	  const char *ptr = &str[0], *end = &str[0] + str.size();

	  while  (std::size_t  rc  =  std::mbrtoc16(&c16,  ptr,  end  - ptr + 1,
     &state))
	  {
	      std::cout << "Next UTF-16 char: " << std::hex
			<< static_cast<int>(c16) << " obtained from ";
	      if (rc == (std::size_t)-3)
		  std::cout << "earlier surrogate pair\n";
	      else if (rc == (std::size_t) - 2)
		  break;
	      else if (rc == (std::size_t) - 1)
		  break;
	      else
	      {
		  std::cout << std::dec << rc << " bytes [ ";
		  for (std::size_t n = 0; n < rc; ++n)
		      std::cout    <<	 std::hex    <<    +static_cast<unsigned
     char>(ptr[n]) << ' ';
		  std::cout << "]\n";
		  ptr += rc;
	      }
	  }
      }

Output:
      Processing 10 bytes: [ 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c ]
      Next UTF-16 char: 0x7a obtained from 1 bytes [ 0x7a ]
      Next UTF-16 char: 0xdf obtained from 2 bytes [ 0xc3 0x9f ]
      Next UTF-16 char: 0x6c34 obtained from 3 bytes [ 0xe6 0xb0 0xb4 ]
      Next UTF-16 char: 0xd83c obtained from 4 bytes [ 0xf0 0x9f 0x8d 0x8c ]
      Next UTF-16 char: 0xdf4c obtained from earlier surrogate pair

See also
	c16rtomb  convert a 16-bit wide character to narrow multibyte string
	(C++11)   (function)
	do_in	   converts a string from ExternT to InternT, such as when read-
     ing from file
	[virtual] (virtual protected member function of
		  std::codecvt<InternT,ExternT,StateT>)
	C documentation for
	mbrtoc16

http://cppreference.com 	   2024.06.10			std::mbrtoc16(3)
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