def _appendstore(self, store):
        """Join another store on to the end of this one."""
        if not store.bitlength:
            return
        # Set new array offset to the number of bits in the final byte of current array.
        store = offsetcopy(store, (self.offset + self.bitlength) % 8)
        if store.offset:
            # first do the byte with the join.
            joinval = (self._rawarray.pop() & (255 ^ (255 >> store.offset)) |
                       (store.getbyte(0) & (255 >> store.offset)))
            self._rawarray.append(joinval)
            self._rawarray.extend(store._rawarray[1:])
        else:
            self._rawarray.extend(store._rawarray)
        self.bitlength += store.bitlength
Join another store on to the end of this one.