code: func roundUp(v uint64) uint64 {
  	v--
  	v |= v >> 1
  	v |= v >> 2
  	v |= v >> 4
  	v |= v >> 8
  	v |= v >> 16
  	v |= v >> 32
  	v++
  	return v
  }
docs: // roundUp takes a uint64 greater than 0 and rounds it up to the next
  // power of 2.