Re: App Unicode call MBCS dll

On Mon, 25 Jun 2007 03:17:00 -0700, Josemi <josemiantelo@gmail.com>
wrote:


What do you mean here in P.D.?

(BTW: I don't like very much DLL exposing C++ interfaces; IMHO if one
wants to expose an object interface in a DLL, better using
object-orientation in pure C (like using handles, etc.) or use COM.)

Back to your problem.

My understand of your problem is:

 1. you have the DLL built using VC++6 in MBCS mode
 2. you cannot modify/rebuild your DLL
 3. you have the app built using VC++6 in Unicode mode
 4. you cannot build your app in MBCS mode

So, I think that you may need an "interface" wrapper DLL to solve your
problem, because if you are in VC++6 and are in Unicode mode, CString
will be considered Unicode strings, and so there is a strong impedence
with the DLL expecting a CString in MBCS...

So you may need an "interface" DLL, to be built with VC++6.

 +--------------------+
 | Your app (Unicode) |
 +--------------------+
           |
 +--------------------+
 | Wrapper DLL | <-- converts Unicode -> MBCS
 +--------------------+
           |
 +--------------------+
 | MBCS original DLL |
 +--------------------+

Assume that the function in your MBCS DLL is:

  bool FunctionMBCS( const CString & stringMBCS );

Then the wrapper DLL should define a function like so:

  // This must be called by the client app
  bool WrapperFunction( const WCHAR * stringUnicode );

Your app must call the WrapperFunction:

  // In your app:
  CString s; // Unicode, in your app

  // Call the wrapper function in wrapper DLL
  // (not the original MBCS DLL)
  boob ret = WrapperFunction( static_cast<const WCHAR *>(s) );

The wrapper function converts from Unicode to MBCS:
The wrapper DLL must be compiled in *MBCS* mode (so CString is MBCS):

  bool WrapperFunction( const WCHAR * stringUnicode )
  {
      //
      // Convert from Unicode to MBCS, and call the
      // original MBCS DLL function
      //

      ... Use ::WideCharToMultiByte to convert from
      ... stringUnicode to MBCS.

      ... Store the MBCS string in 'mbcs':
      CString mbcs;
      mbcs = ...

      // Pass the MBCS converted string to MBCS DLL
      return FunctionMBCS( mbcs );
  }

MrAsm