docs: public void writeOverSet(int which, List<Point2D_I32> points) {
  		BlockIndexLength set = sets.get(which);
  		if( set.length != points.size() )
  			throw new IllegalArgumentException("points and set don't have the same length");
  
  		for (int i = 0; i < set.length; i++) {
  			int index = set.start + i*2;
  			int blockIndex = set.block + index/blockLength;
  			index %= blockLength;
  
  			Point2D_I32 p = points.get(i);
  			int block[] = blocks.get( blockIndex );
  			block[index] = p.x;
  			block[index+1] = p.y;
  		}
  	}