code: private void fastadd(int wo, int off) {
  		this.buffer.add(off - this.sizeinwords);
  		this.buffer.add(wo);
  		this.sizeinwords = off + 1;
  	}
docs: same as add but without updating the cardinality counter, strictly for
  internal use.
  
  @param wo
  the wo
  @param off
  the off