def _invert_all(self):
        """Invert every bit."""
        set = self._datastore.setbyte
        get = self._datastore.getbyte
        for p in xrange(self._datastore.byteoffset, self._datastore.byteoffset + self._datastore.bytelength):
            set(p, 256 + ~get(p))
Invert every bit.