#!/usr/bin/python
"""
INET module. Defines an IPaddr class (Internet Protocol address). 

Exports helper functions:
itodq(int) - return dotted quad string given an integer.
dqtoi(string) - return and integer given a string in IP dotted-quad notation.

The IPaddr class stores the IP address and mask. It also precomputes the
network, host, and broadcast addresses.

"""

from types import *
import string, socket

class IPaddr:
	"""
	Store an IP addresss. Pre-compute the network, host, and broadcast and
	store that as well.

	ipaddress = IPaddr(address, [mask])
	supply an address as either integer or string. A netmask may
	optionally be supplied. It defaults to a classful mask appropriate for its
	class. the netmask may be supplied as integer, dotted quad, or slash (e.g.
	/24) notation.

	Exports 'string' method that returns IP addresses as dotted quad string.

	Raises ValueError if the string representation is malformed, or is not an
	integer.
	"""
	def __init__(self, address, mask=None):
		# determine input type and convert if necessary
		if type(address) == StringType:
			self.address = dqtoi(socket.gethostbyname(address))
		elif type(address) == IntType:
			self.address = address
		else:
			raise ValueError
		# handle the optional mask parameter. Default to classful mask.
		if mask == None:
			if self.address & 0x80000000 == 0:
				self.mask = 0xff000000
			elif self.address & 0x40000000 == 0:
				self.mask = 0xffff0000
			else: 
				self.mask = 0xffffff00
		elif type(mask) == StringType:
			if mask[0] == '/':
				bits = int(mask[1:])
				if bits <= 32 and bits > 0:
					self.mask = 0xffffffff << (32 - bits)
				else:
					raise ValueError
			else:
				self.mask = dqtoi(mask)
		elif type(mask) == IntType:
			self.mask = mask
		else:
			raise ValueError
		# compute and store network, host, and broadcast address
		self.network = self.address & self.mask
		# check for host specific address
		if self.mask == 0xffffffff:
			self.host = self.address
			self.broadcast = 0xffffffff
		else:
			self.host = self.address & (~self.mask)
			self.broadcast = self.address | (~self.mask)

	def __repr__(self):
		return itodq(self.address)

def dqtoi(dq):
	"Return an integer value given an IP address as dotted-quad string."
	octets = string.split(dq, ".")
	if len(octets) != 4:
		raise ValueError
	for octet in octets:
		if int(octet) > 255:
			raise ValueError
	return (int(octets[0]) << 24) + \
			(int(octets[1]) << 16) + \
			(int(octets[2]) << 8) + \
			(int(octets[3]))
	
def itodq(intval):
	"Return a dotted-quad string given an integer. "
	return "%u.%u.%u.%u" % ((intval >> 24) & 0x000000ff, 
							((intval & 0x00ff0000) >> 16), 
							((intval & 0x0000ff00) >> 8), 
							(intval & 0x000000ff))
	

# vim:ts=4:sw=4