Question

I need to convert between wstring and string. I figured out, that using codecvt facet should do the trick, but it doesn’t seem to work for utf-8 locale.

My idea is, that when I read utf-8 encoded file to chars, one utf-8 character is read into two normal characters (which is how utf-8 works). I’d like to create this utf-8 string from wstring representation for library I use in my code.

Does anybody know how to do it?

I already tried this:

  locale mylocale("cs_CZ.utf-8");
  mbstate_t mystate;

  wstring mywstring = L"čřžýáí";

  const codecvt<wchar_t,char,mbstate_t>& myfacet =
    use_facet<codecvt<wchar_t,char,mbstate_t> >(mylocale);

  codecvt<wchar_t,char,mbstate_t>::result myresult;  

  size_t length = mywstring.length();
  char* pstr= new char [length+1];

  const wchar_t* pwc;
  char* pc;

  // translate characters:
  myresult = myfacet.out (mystate,
      mywstring.c_str(), mywstring.c_str()+length+1, pwc,
      pstr, pstr+length+1, pc);

  if ( myresult == codecvt<wchar_t,char,mbstate_t>::ok )
   cout << "Translation successful: " << pstr << endl;
  else cout << "failed" << endl;
  return 0;

which returns ‘failed’ for cs_CZ.utf-8 locale and works correctly for cs_CZ.iso8859-2 locale.

Answer 1

C++ has no idea of Unicode. Use an external library such as ICU (UnicodeString class) or Qt (QString class), both support Unicode, including UTF-8.