+    wxASSERT_MSG( mode.find_first_of('+') != wxString::npos,
+                  "must be opened in read-write mode for this class to work" );
+
+    wxFFileOutputStream::m_file =
+    wxFFileInputStream::m_file = new wxFFile(fileName, mode);
+
+    // see comment in wxFileStream ctor
+    wxFFileInputStream::m_file_destroy = true;