Double null-terminated string

问题:

I need to format a string to be double null-terminated string in order to use SHFileOperation.

Interesting part is i found one of the following working, but not both:

  // Example 1
  CString szDir(_T("D:\\Test"));
  szDir = szDir + _T('\0') + _T('\0');

  // Example 2  
  CString szDir(_T("D:\\Test"));
  szDir = szDir + _T("\0\0");

  //Delete folder
  SHFILEOPSTRUCT fileop;
  fileop.hwnd   = NULL;    // no status display
  fileop.wFunc  = FO_DELETE;  // delete operation
  fileop.pFrom  = szDir;  // source file name as double null terminated string
  fileop.pTo    = NULL;    // no destination needed
  fileop.fFlags = FOF_NOCONFIRMATION|FOF_SILENT;  // do not prompt the user
  fileop.fAnyOperationsAborted = FALSE;
  fileop.lpszProgressTitle     = NULL;
  fileop.hNameMappings         = NULL;
  int ret = SHFileOperation(&fileop);

Does anyone has idea on this?

Is there other way to append double-terminated string?

回答1:

The CString class itself has no problem with a string containing a null character. The problem comes with putting null characters into the string in the first place. The first example works because it is appending a single character, not a string - it accepts the character as is without checking to see if it's null. The second example tries appending a typical C string, which by definition ends at the first null character - you're effectively appending an empty string.

回答2:

You cannot use CString for this purpose. You will need to use your own char[] buffer:

char buf[100]; // or large enough
strcpy(buf, "string to use");
memcpy(buf + strlen(buf), "\0\0", 2);

Although you could do this by only copying one more NUL byte after the existing NUL terminator, I would prefer to copy two so that the source code more accurately reflects the intent of the programmer.