code: func (s *Subnet) Bits() (ones int, zeros int) {
  	for _, b := range []byte(s.mask) {
  		for i := uint(0); i < 8; i++ {
  			if b&(1<<i) == 0 {
  				zeros++
  			} else {
  				ones++
  			}
  		}
  	}
  	return
  }
docs: // Bits returns the number of ones (network bits) and zeros (host bits) in the
  // subnet mask.