-

def ip_to_int(ip)
  ip.split(".").map(&:to_i).reverse.each_with_index.map {|n,i| n << (i*8) }.reduce(:+)
end

def range_to_ip_and_mask(range)
  ip, width = range.split("/")
  mask = 0xffffffff >> width.to_i
  [ip_to_int(ip), mask]
end

def int_to_ip(n)
  (0..3).map do |current_byte|
    (n >> (8 * current_byte)) & 0xFF
  end.reverse.join(".")
end

def in_range?(ip, range)
  ip = ip_to_int(ip)
  net, mask = range_to_ip_and_mask(range)
  ip & ~mask == net & ~mask
end

p in_range?("10.2.3.5", "10.2.3.4/5")
p in_range?("128.2.3.5", "10.2.3.4/5")