code: func hashLen17to32(s []byte, length uint32) uint64 {
  	var a = fetch64(s) * k1
  	var b = fetch64(s[8:])
  	var c = fetch64(s[length-8:]) * k2
  	var d = fetch64(s[length-16:]) * k0
  
  	return hashLen16(rotate64(a-b, 43)+rotate64(c, 30)+d,
  		a+rotate64(b^k3, 20)-c+uint64(length))
  }
docs: // This probably works well for 16-byte strings as well, but it may be overkill