Convert char * to LPWSTR

Question

I am trying to convert a program for multibyte character to Unicode.

I have gone through the program and preceded the string literals with L so they look like L"string".

This has worked but I am now left with a C style string that won't conform. I have tried the L and putting it in TEXT() but the L gets added to the variable name -- not the string -- if I use TEXT().

I have tried making it a TCHAR but then it complains that it cannot convert a TCHAR to a char *.

What options am I left with?

I know C and C++ are different. It is an old in-house C library that has been used in C++ projects for several years now.

Answer 1

The std::mbstowcs function is what you are looking for:

 char text[] = "something";  wchar_t wtext[20];  mbstowcs(wtext, text, strlen(text)+1);//Plus null  LPWSTR ptr = wtext; 

for strings,

 string text = "something";  wchar_t wtext[20];  mbstowcs(wtext, text.c_str(), text.length());//includes null  LPWSTR ptr = wtext; 

--> ED: The "L" prefix only works on string literals, not variables. <--

Answer 2

The clean way to use mbstowcs is to call it twice to find the length of the result:

  const char * cs = <your input char*>   size_t wn = mbsrtowcs(NULL, &cs, 0, NULL);    // error if wn == size_t(-1)    wchar_t * buf = new wchar_t[wn + 1]();  // value-initialize to 0 (see below)    wn = mbsrtowcs(buf, &cs, wn + 1, NULL);    // error if wn == size_t(-1)    assert(cs == NULL); // successful conversion    // result now in buf, return e.g. as std::wstring    delete[] buf; 

Don't forget to call setlocale(LC_CTYPE, ""); at the beginning of your program!

The advantage over the Windows MultiByteToWideChar is that this is entirely standard C, although on Windows you might prefer the Windows API function anyway.

I usually wrap this method, along with the opposite one, in two conversion functions string->wstring and wstring->string. If you also add trivial overloads string->string and wstring->wstring, you can easily write code that compiles with the Winapi TCHAR typedef in any setting.

[Edit:] I added zero-initialization to buf, in case you plan to use the C array directly. I would usually return the result as std::wstring(buf, wn), though, but do beware if you plan on using C-style null-terminated arrays.[/]

In a multithreaded environment you should pass a thread-local conversion state to the function as its final (currently invisible) parameter.

Here is a small rant of mine on this topic.