require 'rex/socket'

module Rex
module Socket

###
#
# This class provides an interface to enumerating a subnet with a supplied
# netmask.
#
###
class SubnetWalker

	#
	# Initializes a subnet walker instance using the supplied subnet
	# information.
	#
	def initialize(subnet, netmask)
		self.subnet  = Socket.resolv_to_dotted(subnet)
		self.netmask = Socket.resolv_to_dotted(netmask)

		reset
	end

	#
	# Resets the subnet walker back to its original state.
	#
	def reset
		self.curr_ip     = self.subnet.split('.')
		self.num_ips     = (1 << (32 - Socket.net2bitmask(self.netmask).to_i))
		self.curr_ip_idx = 0
	end

	#
	# Returns the next IP address.
	#
	def next_ip
		if (curr_ip_idx >= num_ips)
			return nil
		end

		if (curr_ip_idx > 0)
			self.curr_ip[3] = (curr_ip[3].to_i + 1) % 256
			self.curr_ip[2] = (curr_ip[2].to_i + 1) % 256 if (curr_ip[3] == 0)
			self.curr_ip[1] = (curr_ip[1].to_i + 1) % 256 if (curr_ip[2] == 0)
			self.curr_ip[0] = (curr_ip[0].to_i + 1) % 256 if (curr_ip[1] == 0)
		end

		self.curr_ip_idx += 1
	
		self.curr_ip.join('.')
	end

	#
	# The subnet that is being enumerated.
	#
	attr_reader :subnet
	#
	# The netmask of the subnet.
	#
	attr_reader :netmask
	#
	# The total number of IPs within the subnet.
	#
	attr_reader :num_ips

protected

	attr_writer   :subnet, :netmask, :num_ips # :nodoc:
	attr_accessor :curr_ip, :curr_ip_idx # :nodoc:

end

end
end
