Handling Multiple Win32 Operating Environments

Listing 2 Implementing SetCurrentDirectoryW() for SharedCU, Redefine and DLL models

#ifdef WDN_SHAREDCU

# define SetCurrentDirectoryW_impl  SetCurrentDirectoryW	

. . .

#endif /* WDN_SHAREDCU */

. . .

/* Loads KERNEL32.DLL and returns its instance handle. There's no
 * release, but that's ok with KERNEL32.DLL, since every process
 * must be statically linked to it in order to be able to call
 * LoadLibrary() in the first place! Hacky, but valid.
 */
static HINSTANCE GetInstance_Kernel32();


static BOOL WINAPI SetCurrentDirectoryW_impl_9x(LPCWSTR lpPathName)
{
  size_t  len       = lstrlenW(lpPathName);
  char    *pathName = (char*)_alloca(1 + len);

  WideCharToMultiByte(CP_ACP, 0, lpPathName, 1 + len, pathName, 1 + len, NULL, 		NULL);

  return SetCurrentDirectoryA(pathName);
}

static BOOL WINAPI SetCurrentDirectoryW_impl_NT(LPCWSTR lpPathName)
{
#ifdef WDN_SHAREDCU
  /* In this mode, SetCurrentDirectoryW_impl is #defined to be SetCurrentDirectoryW, 
   * so linking to SetCurrentDirectoryW would just result in infinite recursion 
   * and stack exhaustion. It's unlikely that that process would result in the 
   * desired directory change.
   *
   * Hence, we need to load SetCurrentDirectoryW from KERNEL32.DLL, and call it
   * in that way.
   */

  typedef BOOL (WINAPI *PFnSetCurrentDirectoryW)(LPCWSTR lpFileName);

  PFnSetCurrentDirectoryW pfn = 						(PFnSetCurrentDirectoryW)GetProcAddress(GetInstance_Kernel32(), 		"SetCurrentDirectoryW");

  return (NULL == pfn) ? FALSE : pfn(lpPathName);
#else
  /* Otherwise just link to the function directly. */
  return SetCurrentDirectoryW(lpPathName);
#endif /* WDN_SHAREDCU */
}

#ifdef WDN_SHAREDCU
# pragma warning(disable : 4273)
#endif /* WDN_SHAREDCU */

#ifdef WDN_DLL
extern __declspec(dllexport)
#endif /* WDN_DLL */
BOOL WINAPI SetCurrentDirectoryW_impl(LPCWSTR lpPathName)
{
  if(IsWinNT())
  {
    debug_printf("SetCurrentDirectoryW_impl(): calling NT's 			SetCurrentDirectoryW()\n");

    return SetCurrentDirectoryW_impl_NT(lpPathName);
  }
  else
  {
    debug_printf("SetCurrentDirectoryW_impl(): calling 				SetCurrentDirectoryW_impl_9x()\n");

    return SetCurrentDirectoryW_impl_9x(lpPathName);
  }
}

#ifdef WDN_SHAREDCU
# pragma warning(default : 4273)
#endif /* WDN_SHAREDCU */