Need example of modifying string parameter

[Garrett Goebel]

I'm trying to wrap the Win32 user32.dll function 

UINT RealGetWindowClassA(
  HWND  hwnd,      // handle to window
  LPTSTR pszType,  // window type buffer
  UINT  cchType    // size of window type buffer
);


Working with my extremely limited knowledge of C... and Perl internals... I
came up with this:

int Get_Window_Class(long hWnd, SV* class) {
  int size, rval;
  char myclass[] = SvPL(class, *size);
  rval = RealGetWindowClassA(hWnd, myclass, size);
  class = newSVpvf(sprintf("%s", myclass));
  return rval;
}

Which not surprisingly doesn't work. Not knowing my right hand from my left
with regards to C and the Perl API... can anyone suggest something that has
a higher chance of success?

Garrett