code: private void setBitsImpl(int position, long value, int length) {
  		int i = position >> ADDRESS_BITS;
  		int s = position & ADDRESS_MASK;
  		long m = length == ADDRESS_SIZE ? -1L : (1L << length) - 1L;
  		long v = value & m;
  		performAdjSet(length, i, s, m, v);
  	}
docs: length guaranteed to be non-zero