code: public void grow() {
  		if( tailBlockSize >= blockLength ) {
  			tailBlockSize = 0;
  			blocks.grow();
  		}
  
  		BlockIndexLength s = sets.grow();
  		s.block = blocks.size-1;
  		s.start = tailBlockSize;
  		s.length = 0;
  
  		tail = s;
  	}
docs: Adds a new point set to the end.