code: func numBlocks(size int64, blockSize int) int {
  	numBlocks := int(size / int64(blockSize))
  	if size%int64(blockSize) != 0 {
  		numBlocks++
  	}
  	assert2(int64(numBlocks)*int64(blockSize) >= size, "size is too large for this block size")
  	return numBlocks
  }
docs: /* Return the number of blocks required to store size values on blockSize. */