Remove up to the specified maxNumItems from the front of this container. Optionally specify a buffer into which the items removed from the container are appended. If buffer is non-null, the removed items are appended to it as if by repeated application of buffer->push_back(popFront()) while the const is not empty and maxNumItems have not yet been removed. Note that *buffer is not cleared -- the popped items are appended after any pre-existing contents.
Also note that to transfer the entire contents of a Deque d to a vector v, use d.removeAll(&v);.