wcsrtombs_s question

OK I'm using VC++ and I've read the MSDN description at
wcsrtombs_s
but I've obviously misunderstood something.

The following function is supposed to produce a popup window with the message given in 'str'. When compiled as a Unicode program the wide string str needs to be converted into a UTF-8 string for fl_message. What I actually get is a null string for 'copiedstring'.

Possibly this has something to do with the setlocale function?

Any hints gratefully received.

Code:

void pbox(const _TCHAR *str)
{ 
	char copiedstring[250];
	mbstate_t mbstate;
	size_t retval;
#ifdef _UNICODE
//	setlocale(LC_CTYPE, "en_US.UTF-8"); 
	// Convert to UTF-8 from wchar_t
    // Reset to initial conversion state
	const wchar_t *wcsIndirectString = str;
    memset(&mbstate, 0, sizeof(mbstate));
	wcsrtombs_s(&retval, copiedstring, sizeof(copiedstring), &str, 249, &mbstate);
	fl_message(copiedstring);
#else
	fl_message(str);
#endif
}

Originally Posted by PaulBlay

Possibly this has something to do with the setlocale function?

Well on further checking I noticed this ...

The set of available languages, country/region codes, and code pages includes all those supported by the Win32 NLS API except code pages that require more than two bytes per character, such as UTF-7 and UTF-8. If you provide a code page like UTF-7 or UTF-8, setlocale will fail, returning NULL. The set of language and country/region codes supported by setlocale is listed in Language and Country/Region Strings.

So how am I supposed to convert a wchar_t string to a UTF-8 string?

Some code I have laying around...

Code:

std::wstring utf8_to_wstr(const std::string &utf8)
{
    // NOTE: we are assuming that the number of bytes in a UTF8 string is 
    //       always >= to the number of wchar_t's required to represent that 
    //       string in UTF16LE - which should hold true
    std::vector<wchar_t> wbuff(utf8.length() + 1);

    // NOTE: this does not NULL terminate the string in wbuff, but this is ok
    //       since it was zero-initialized in the vector constructor
    if (!MultiByteToWideChar(CP_UTF8, 0, utf8.c_str(), utf8.length(),
                             &wbuff[0], utf8.length()))
    {
        return L"ErrorW";
    }//if

    return &wbuff[0];
}//utf8_to_wstr

std::string wstr_to_str(const std::wstring &wstr, UINT cp = CP_ACP)
{
    int len = WideCharToMultiByte(cp, 0, wstr.c_str(), wstr.length(), 
                                  0, 0, 0, 0);
    if (!len)
        return "ErrorA";

    std::vector<char> abuff(len + 1);

    // NOTE: this does not NULL terminate the string in abuff, but this is ok
    //       since it was zero-initialized in the vector constructor
    if (!WideCharToMultiByte(cp, 0, wstr.c_str(), wstr.length(), 
                             &abuff[0], len, 0, 0))
    {
        return "ErrorA";
    }//if

    return &abuff[0];
}//wstr_to_str

gg

Originally Posted by Codeplug

Some code I have laying around...

Great. Would you mind me using that, with attribution, in a GPL licensed project?

>> Would you mind me using that
Not at all.

gg