#!/usr/bin/env python3

class NotValidAddressException(Exception):
    pass

def ipaddr_aton(ipaddr):
    _tmp = ''
    lead_bit = True
    base = 10
    ipaddr_len = len(ipaddr)
    blk_count = 3
    bit_count = 0
    sum = 0
    for i, item in enumerate(ipaddr):
        if lead_bit:
            if item == '0':
                base = 8
            elif item == 'x' or item == 'X':
                base = 16
                lead_bit = False
                continue
            elif item == ' ':
                continue
            else:
                if bit_count == 0:
                    base = 10
                    lead_bit = False

        if item != '.':
            _tmp += item
            bit_count += 1

        if item == '.' or i+1 == ipaddr_len:
            if blk_count < 0:
                raise NotValidAddressException

            if i+1 == ipaddr_len and blk_count != 0:
                blk_count = 0
            try:
                blk_value = int(_tmp, base)
            except:
                raise NotValidAddressException

            if blk_value > 255:
                raise NotValidAddressException

            sum += blk_value << (8*blk_count)

            lead_bit = True
            _tmp = ''
            blk_count -= 1
            bit_count = 0
    return sum