python-ipy 1:0.75-1 / usr / share / pyshared / IPy.py

"""
IPy - class and tools for handling of IPv4 and IPv6 addresses and networks.
See README file for learn how to use IPy.

Further Information might be available at:
https://github.com/haypo/python-ipy
"""

__version__ = '0.75'

import sys
import types

# Definition of the Ranges for IPv4 IPs
# this should include www.iana.org/assignments/ipv4-address-space
# and www.iana.org/assignments/multicast-addresses
IPv4ranges = {
    '0':                'PUBLIC',   # fall back
    '00000000':         'PRIVATE',  # 0/8
    '00001010':         'PRIVATE',  # 10/8
    '01111111':         'PRIVATE',  # 127.0/8
    '1':                'PUBLIC',   # fall back
    '1010100111111110': 'PRIVATE',  # 169.254/16
    '101011000001':     'PRIVATE',  # 172.16/12
    '1100000010101000': 'PRIVATE',  # 192.168/16
    '111':              'RESERVED'  # 224/3
    }

# Definition of the Ranges for IPv6 IPs
# http://www.iana.org/assignments/ipv6-address-space/
# http://www.iana.org/assignments/ipv6-unicast-address-assignments/
# http://www.iana.org/assignments/ipv6-multicast-addresses/
IPv6ranges = {
    '00000000'                                      : 'RESERVED',               # ::/8
    '0' * 96                                        : 'RESERVED',               # ::/96 Formerly IPV4COMP [RFC4291]
    '0' * 128                                       : 'UNSPECIFIED',            # ::/128
    '0' * 127 + '1'                                 : 'LOOPBACK',               # ::1/128
    '0' * 80 + '1' * 16                             : 'IPV4MAP',                # ::ffff:0:0/96
    '00000000011001001111111110011011' + '0' * 64   : 'WKP46TRANS',             # 0064:ff9b::/96 Well-Known-Prefix [RFC6052]
    '00000001'                                      : 'UNASSIGNED',             # 0100::/8
    '0000001'                                       : 'RESERVED',               # 0200::/7 Formerly NSAP [RFC4048]
    '0000010'                                       : 'RESERVED',               # 0400::/7 Formerly IPX [RFC3513]
    '0000011'                                       : 'RESERVED',               # 0600::/7
    '00001'                                         : 'RESERVED',               # 0800::/5
    '0001'                                          : 'RESERVED',               # 1000::/4
    '001'                                           : 'GLOBAL-UNICAST',         # 2000::/3 [RFC4291]
    '00100000000000010000000'                       : 'SPECIALPURPOSE',         # 2001::/23 [RFC4773]
    '00100000000000010000000000000000'              : 'TEREDO',                 # 2001::/32 [RFC4380]
    '00100000000000010000000000000010' + '0' * 16   : 'BMWG',                   # 2001:0002::/48 Benchmarking [RFC5180]
    '0010000000000001000000000001'                  : 'ORCHID',                 # 2001:0010::/28 (Temp until 2014-03-21) [RFC4843]
    '00100000000000010000001'                       : 'ALLOCATED APNIC',        # 2001:0200::/23
    '00100000000000010000010'                       : 'ALLOCATED ARIN',         # 2001:0400::/23
    '00100000000000010000011'                       : 'ALLOCATED RIPE NCC',     # 2001:0600::/23
    '00100000000000010000100'                       : 'ALLOCATED RIPE NCC',     # 2001:0800::/23
    '00100000000000010000101'                       : 'ALLOCATED RIPE NCC',     # 2001:0a00::/23
    '00100000000000010000110'                       : 'ALLOCATED APNIC',        # 2001:0c00::/23
    '00100000000000010000110110111000'              : 'DOCUMENTATION',          # 2001:0db8::/32 [RFC3849]
    '00100000000000010000111'                       : 'ALLOCATED APNIC',        # 2001:0e00::/23
    '00100000000000010001001'                       : 'ALLOCATED LACNIC',       # 2001:1200::/23
    '00100000000000010001010'                       : 'ALLOCATED RIPE NCC',     # 2001:1400::/23
    '00100000000000010001011'                       : 'ALLOCATED RIPE NCC',     # 2001:1600::/23
    '00100000000000010001100'                       : 'ALLOCATED ARIN',         # 2001:1800::/23
    '00100000000000010001101'                       : 'ALLOCATED RIPE NCC',     # 2001:1a00::/23
    '0010000000000001000111'                        : 'ALLOCATED RIPE NCC',     # 2001:1c00::/22
    '00100000000000010010'                          : 'ALLOCATED RIPE NCC',     # 2001:2000::/20
    '001000000000000100110'                         : 'ALLOCATED RIPE NCC',     # 2001:3000::/21
    '0010000000000001001110'                        : 'ALLOCATED RIPE NCC',     # 2001:3800::/22
    '0010000000000001001111'                        : 'RESERVED',               # 2001:3c00::/22 Possible future allocation to RIPE NCC
    '00100000000000010100000'                       : 'ALLOCATED RIPE NCC',     # 2001:4000::/23
    '00100000000000010100001'                       : 'ALLOCATED AFRINIC',      # 2001:4200::/23
    '00100000000000010100010'                       : 'ALLOCATED APNIC',        # 2001:4400::/23
    '00100000000000010100011'                       : 'ALLOCATED RIPE NCC',     # 2001:4600::/23
    '00100000000000010100100'                       : 'ALLOCATED ARIN',         # 2001:4800::/23
    '00100000000000010100101'                       : 'ALLOCATED RIPE NCC',     # 2001:4a00::/23
    '00100000000000010100110'                       : 'ALLOCATED RIPE NCC',     # 2001:4c00::/23
    '00100000000000010101'                          : 'ALLOCATED RIPE NCC',     # 2001:5000::/20
    '0010000000000001100'                           : 'ALLOCATED APNIC',        # 2001:8000::/19
    '00100000000000011010'                          : 'ALLOCATED APNIC',        # 2001:a000::/20
    '00100000000000011011'                          : 'ALLOCATED APNIC',        # 2001:b000::/20
    '0010000000000010'                              : '6TO4',                   # 2002::/16 "6to4" [RFC3056]
    '001000000000001100'                            : 'ALLOCATED RIPE NCC',     # 2003::/18
    '001001000000'                                  : 'ALLOCATED APNIC',        # 2400::/12
    '001001100000'                                  : 'ALLOCATED ARIN',         # 2600::/12
    '00100110000100000000000'                       : 'ALLOCATED ARIN',         # 2610::/23
    '00100110001000000000000'                       : 'ALLOCATED ARIN',         # 2620::/23
    '001010000000'                                  : 'ALLOCATED LACNIC',       # 2800::/12
    '001010100000'                                  : 'ALLOCATED RIPE NCC',     # 2a00::/12
    '001011000000'                                  : 'ALLOCATED AFRINIC',      # 2c00::/12
    '00101101'                                      : 'RESERVED',               # 2d00::/8
    '0010111'                                       : 'RESERVED',               # 2e00::/7
    '0011'                                          : 'RESERVED',               # 3000::/4
    '010'                                           : 'RESERVED',               # 4000::/3
    '011'                                           : 'RESERVED',               # 6000::/3
    '100'                                           : 'RESERVED',               # 8000::/3
    '101'                                           : 'RESERVED',               # a000::/3
    '110'                                           : 'RESERVED',               # c000::/3
    '1110'                                          : 'RESERVED',               # e000::/4
    '11110'                                         : 'RESERVED',               # f000::/5
    '111110'                                        : 'RESERVED',               # f800::/6
    '1111110'                                       : 'ULA',                    # fc00::/7 [RFC4193]
    '111111100'                                     : 'RESERVED',               # fe00::/9
    '1111111010'                                    : 'LINKLOCAL',              # fe80::/10
    '1111111011'                                    : 'RESERVED',               # fec0::/10 Formerly SITELOCAL [RFC4291]
    '11111111'                                      : 'MULTICAST',              # ff00::/8
    '1111111100000001'                              : 'NODE-LOCAL MULTICAST',   # ff01::/16
    '1111111100000010'                              : 'LINK-LOCAL MULTICAST',   # ff02::/16
    '1111111100000100'                              : 'ADMIN-LOCAL MULTICAST',  # ff04::/16
    '1111111100000101'                              : 'SITE-LOCAL MULTICAST',   # ff05::/16
    '1111111100001000'                              : 'ORG-LOCAL MULTICAST',    # ff08::/16
    '1111111100001110'                              : 'GLOBAL MULTICAST',       # ff0e::/16
    '1111111100001111'                              : 'RESERVED MULTICAST',     # ff0f::/16
    '111111110011'                                  : 'PREFIX-BASED MULTICAST', # ff30::/12 [RFC3306]
    '111111110111'                                  : 'RP-EMBEDDED MULTICAST',  # ff70::/12 [RFC3956]
    }


class IPint:
    """Handling of IP addresses returning integers.

    Use class IP instead because some features are not implemented for
    IPint."""

    def __init__(self, data, ipversion=0, make_net=0):
        """Create an instance of an IP object.

        Data can be a network specification or a single IP. IP
        addresses can be specified in all forms understood by
        parseAddress(). The size of a network can be specified as

        /prefixlen        a.b.c.0/24               2001:658:22a:cafe::/64
        -lastIP           a.b.c.0-a.b.c.255        2001:658:22a:cafe::-2001:658:22a:cafe:ffff:ffff:ffff:ffff
        /decimal netmask  a.b.c.d/255.255.255.0    not supported for IPv6

        If no size specification is given a size of 1 address (/32 for
        IPv4 and /128 for IPv6) is assumed.

        If make_net is True, an IP address will be transformed into the network
        address by applying the specified netmask.

        >>> print(IP('127.0.0.0/8'))
        127.0.0.0/8
        >>> print(IP('127.0.0.0/255.0.0.0'))
        127.0.0.0/8
        >>> print(IP('127.0.0.0-127.255.255.255'))
        127.0.0.0/8
        >>> print(IP('127.0.0.1/255.0.0.0', make_net=True))
        127.0.0.0/8

        See module documentation for more examples.
        """

        # Print no Prefixlen for /32 and /128
        self.NoPrefixForSingleIp = 1

        # Do we want prefix printed by default? see _printPrefix()
        self.WantPrefixLen = None

        netbits = 0
        prefixlen = -1

        # handling of non string values in constructor
        if isinstance(data, (int, long)):
            self.ip = long(data)
            if ipversion == 0:
                if self.ip < 0x100000000:
                    ipversion = 4
                else:
                    ipversion = 6
            if ipversion == 4:
                if self.ip > 0xffffffff:
                    raise ValueError("IPv4 Addresses can't be larger than 0xffffffffffffffffffffffffffffffff: %x" % self.ip)
                prefixlen = 32
            elif ipversion == 6:
                if self.ip > 0xffffffffffffffffffffffffffffffff:
                    raise ValueError("IPv6 Addresses can't be larger than 0xffffffffffffffffffffffffffffffff: %x" % self.ip)
                prefixlen = 128
            else:
                raise ValueError("only IPv4 and IPv6 supported")
            self._ipversion = ipversion
            self._prefixlen = prefixlen
        # handle IP instance as an parameter
        elif isinstance(data, IPint):
            self._ipversion = data._ipversion
            self._prefixlen = data._prefixlen
            self.ip = data.ip
        elif isinstance(data, (str, unicode)):
            # TODO: refactor me!
            # splitting of a string into IP and prefixlen et. al.
            x = data.split('-')
            if len(x) == 2:
                # a.b.c.0-a.b.c.255 specification ?
                (ip, last) = x
                (self.ip, parsedVersion) = parseAddress(ip)
                if parsedVersion != 4:
                    raise ValueError("first-last notation only allowed for IPv4")
                (last, lastversion) = parseAddress(last)
                if lastversion != 4:
                    raise ValueError("last address should be IPv4, too")
                if last < self.ip:
                    raise ValueError("last address should be larger than first")
                size = last - self.ip
                netbits = _count1Bits(size)
                # make sure the broadcast is the same as the last ip
                # otherwise it will return /16 for something like:
                # 192.168.0.0-192.168.191.255
                if IP('%s/%s' % (ip, 32-netbits)).broadcast().int() != last:
                    raise ValueError("the range %s is not on a network boundary." % data)
            elif len(x) == 1:
                x = data.split('/')
                # if no prefix is given use defaults
                if len(x) == 1:
                    ip = x[0]
                    prefixlen = -1
                elif len(x) > 2:
                    raise ValueError("only one '/' allowed in IP Address")
                else:
                    (ip, prefixlen) = x
                    if prefixlen.find('.') != -1:
                        # check if the user might have used a netmask like
                        # a.b.c.d/255.255.255.0
                        (netmask, vers) = parseAddress(prefixlen)
                        if vers != 4:
                            raise ValueError("netmask must be IPv4")
                        prefixlen = _netmaskToPrefixlen(netmask)
            elif len(x) > 2:
                raise ValueError("only one '-' allowed in IP Address")
            else:
                raise ValueError("can't parse")

            (self.ip, parsedVersion) = parseAddress(ip)
            if ipversion == 0:
                ipversion = parsedVersion
            if prefixlen == -1:
                if ipversion == 4:
                    prefixlen = 32 - netbits
                elif ipversion == 6:
                    prefixlen = 128 - netbits
                else:
                    raise ValueError("only IPv4 and IPv6 supported")
            self._ipversion = ipversion
            self._prefixlen = int(prefixlen)

            if make_net:
                self.ip = self.ip & _prefixlenToNetmask(self._prefixlen, self._ipversion)

            if not _checkNetaddrWorksWithPrefixlen(self.ip,
            self._prefixlen, self._ipversion):
                raise ValueError("%s has invalid prefix length (%s)" % (repr(self), self._prefixlen))
        else:
            raise TypeError("Unsupported data type: %s" % type(data))

    def int(self):
        """Return the first / base / network addess as an (long) integer.

        The same as IP[0].

        >>> "%X" % IP('10.0.0.0/8').int()
        'A000000'
        """
        return self.ip

    def version(self):
        """Return the IP version of this Object.

        >>> IP('10.0.0.0/8').version()
        4
        >>> IP('::1').version()
        6
        """
        return self._ipversion

    def prefixlen(self):
        """Returns Network Prefixlen.

        >>> IP('10.0.0.0/8').prefixlen()
        8
        """
        return self._prefixlen

    def net(self):
        """
        Return the base (first) address of a network as an (long) integer.
        """
        return self.int()

    def broadcast(self):
        """
        Return the broadcast (last) address of a network as an (long) integer.

        The same as IP[-1]."""
        return self.int() + self.len() - 1

    def _printPrefix(self, want):
        """Prints Prefixlen/Netmask.

        Not really. In fact it is our universal Netmask/Prefixlen printer.
        This is considered an internal function.

        want == 0 / None        don't return anything    1.2.3.0
        want == 1               /prefix                  1.2.3.0/24
        want == 2               /netmask                 1.2.3.0/255.255.255.0
        want == 3               -lastip                  1.2.3.0-1.2.3.255
        """

        if (self._ipversion == 4 and self._prefixlen == 32) or \
           (self._ipversion == 6 and self._prefixlen == 128):
            if self.NoPrefixForSingleIp:
                want = 0
        if want == None:
            want = self.WantPrefixLen
            if want == None:
                want = 1
        if want:
            if want == 2:
                # this should work with IP and IPint
                netmask = self.netmask()
                if not isinstance(netmask, (int, long)):
                    netmask = netmask.int()
                return "/%s" % (intToIp(netmask, self._ipversion))
            elif want == 3:
                return "-%s" % (intToIp(self.ip + self.len() - 1, self._ipversion))
            else:
                # default
                return "/%d" % (self._prefixlen)
        else:
            return ''

        # We have different flavours to convert to:
        # strFullsize   127.0.0.1    2001:0658:022a:cafe:0200:c0ff:fe8d:08fa
        # strNormal     127.0.0.1    2001:658:22a:cafe:200:c0ff:fe8d:08fa
        # strCompressed 127.0.0.1    2001:658:22a:cafe::1
        # strHex        0x7F000001   0x20010658022ACAFE0200C0FFFE8D08FA
        # strDec        2130706433   42540616829182469433547974687817795834

    def strBin(self, wantprefixlen = None):
        """Return a string representation as a binary value.

        >>> print(IP('127.0.0.1').strBin())
        01111111000000000000000000000001
        """


        if self._ipversion == 4:
            bits = 32
        elif self._ipversion == 6:
            bits = 128
        else:
            raise ValueError("only IPv4 and IPv6 supported")

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 0
        ret = _intToBin(self.ip)
        return  '0' * (bits - len(ret)) + ret + self._printPrefix(wantprefixlen)

    def strCompressed(self, wantprefixlen = None):
        """Return a string representation in compressed format using '::' Notation.

        >>> IP('127.0.0.1').strCompressed()
        '127.0.0.1'
        >>> IP('2001:0658:022a:cafe:0200::1').strCompressed()
        '2001:658:22a:cafe:200::1'
        >>> IP('ffff:ffff:ffff:ffff:ffff:f:f:fffc/127').strCompressed()
        'ffff:ffff:ffff:ffff:ffff:f:f:fffc/127'
        """

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 1

        if self._ipversion == 4:
            return self.strFullsize(wantprefixlen)
        else:
            if self.ip >> 32 == 0xffff:
                ipv4 = intToIp(self.ip & 0xffffffff, 4)
                text = "::ffff:" + ipv4 + self._printPrefix(wantprefixlen)
                return text
            # find the longest sequence of '0'
            hextets = [int(x, 16) for x in self.strFullsize(0).split(':')]
            # every element of followingzeros will contain the number of zeros
            # following the corresponding element of hextets
            followingzeros = [0] * 8
            for i in xrange(len(hextets)):
                followingzeros[i] = _countFollowingZeros(hextets[i:])
            # compressionpos is the position where we can start removing zeros
            compressionpos = followingzeros.index(max(followingzeros))
            if max(followingzeros) > 1:
                # genererate string with the longest number of zeros cut out
                # now we need hextets as strings
                hextets = [x for x in self.strNormal(0).split(':')]
                while compressionpos < len(hextets) and hextets[compressionpos] == '0':
                    del(hextets[compressionpos])
                hextets.insert(compressionpos, '')
                if compressionpos + 1 >= len(hextets):
                    hextets.append('')
                if compressionpos == 0:
                    hextets = [''] + hextets
                return ':'.join(hextets) + self._printPrefix(wantprefixlen)
            else:
                return self.strNormal(0) + self._printPrefix(wantprefixlen)

    def strNormal(self, wantprefixlen = None):
        """Return a string representation in the usual format.

        >>> print(IP('127.0.0.1').strNormal())
        127.0.0.1
        >>> print(IP('2001:0658:022a:cafe:0200::1').strNormal())
        2001:658:22a:cafe:200:0:0:1
        """

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 1

        if self._ipversion == 4:
            ret = self.strFullsize(0)
        elif self._ipversion == 6:
            ret = ':'.join([hex(x)[2:] for x in [int(x, 16) for x in self.strFullsize(0).split(':')]])
        else:
            raise ValueError("only IPv4 and IPv6 supported")



        return ret + self._printPrefix(wantprefixlen)

    def strFullsize(self, wantprefixlen = None):
        """Return a string representation in the non-mangled format.

        >>> print(IP('127.0.0.1').strFullsize())
        127.0.0.1
        >>> print(IP('2001:0658:022a:cafe:0200::1').strFullsize())
        2001:0658:022a:cafe:0200:0000:0000:0001
        """

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 1

        return intToIp(self.ip, self._ipversion).lower() + self._printPrefix(wantprefixlen)

    def strHex(self, wantprefixlen = None):
        """Return a string representation in hex format in lower case.

        >>> IP('127.0.0.1').strHex()
        '0x7f000001'
        >>> IP('2001:0658:022a:cafe:0200::1').strHex()
        '0x20010658022acafe0200000000000001'
        """

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 0

        x = hex(self.ip)
        if x[-1] == 'L':
            x = x[:-1]
        return x.lower() + self._printPrefix(wantprefixlen)

    def strDec(self, wantprefixlen = None):
        """Return a string representation in decimal format.

        >>> print(IP('127.0.0.1').strDec())
        2130706433
        >>> print(IP('2001:0658:022a:cafe:0200::1').strDec())
        42540616829182469433547762482097946625
        """

        if self.WantPrefixLen == None and wantprefixlen == None:
            wantprefixlen = 0

        x =  str(self.ip)
        if x[-1] == 'L':
            x = x[:-1]
        return x + self._printPrefix(wantprefixlen)

    def iptype(self):
        """Return a description of the IP type ('PRIVATE', 'RESERVERD', etc).

        >>> print(IP('127.0.0.1').iptype())
        PRIVATE
        >>> print(IP('192.168.1.1').iptype())
        PRIVATE
        >>> print(IP('195.185.1.2').iptype())
        PUBLIC
        >>> print(IP('::1').iptype())
        LOOPBACK
        >>> print(IP('2001:0658:022a:cafe:0200::1').iptype())
        ALLOCATED RIPE NCC

        The type information for IPv6 is out of sync with reality.
        """

        # this could be greatly improved

        if self._ipversion == 4:
            iprange = IPv4ranges
        elif self._ipversion == 6:
            iprange = IPv6ranges
        else:
            raise ValueError("only IPv4 and IPv6 supported")

        bits = self.strBin()
        for i in xrange(len(bits), 0, -1):
            if bits[:i] in iprange:
                return iprange[bits[:i]]
        return "unknown"


    def netmask(self):
        """Return netmask as an integer.

        >>> "%X" % IP('195.185.0.0/16').netmask().int()
        'FFFF0000'
        """

        # TODO: unify with prefixlenToNetmask?
        if self._ipversion == 4:
            locallen = 32 - self._prefixlen
        elif self._ipversion == 6:
            locallen = 128 - self._prefixlen
        else:
            raise ValueError("only IPv4 and IPv6 supported")

        return ((2 ** self._prefixlen) - 1) << locallen


    def strNetmask(self):
        """Return netmask as an string. Mostly useful for IPv6.

        >>> print(IP('195.185.0.0/16').strNetmask())
        255.255.0.0
        >>> print(IP('2001:0658:022a:cafe::0/64').strNetmask())
        /64
        """

        # TODO: unify with prefixlenToNetmask?
        if self._ipversion == 4:
            locallen = 32 - self._prefixlen
            return intToIp(((2 ** self._prefixlen) - 1) << locallen, 4)
        elif self._ipversion == 6:
            locallen = 128 - self._prefixlen
            return "/%d" % self._prefixlen
        else:
            raise ValueError("only IPv4 and IPv6 supported")

    def len(self):
        """Return the length of a subnet.

        >>> print(IP('195.185.1.0/28').len())
        16
        >>> print(IP('195.185.1.0/24').len())
        256
        """

        if self._ipversion == 4:
            locallen = 32 - self._prefixlen
        elif self._ipversion == 6:
            locallen = 128 - self._prefixlen
        else:
            raise ValueError("only IPv4 and IPv6 supported")

        return 2 ** locallen


    def __nonzero__(self):
        """All IPy objects should evaluate to true in boolean context.
        Ordinarily they do, but if handling a default route expressed as
        0.0.0.0/0, the __len__() of the object becomes 0, which is used
        as the boolean value of the object.
        """
        return True


    def __len__(self):
        """Return the length of a subnet.

        Called to implement the built-in function len().
        It breaks with IPv6 Networks. Anybody knows how to fix this."""

        # Python < 2.2 has this silly restriction which breaks IPv6
        # how about Python >= 2.2 ... ouch - it persists!

        return int(self.len())


    def __getitem__(self, key):
        """Called to implement evaluation of self[key].

        >>> ip=IP('127.0.0.0/30')
        >>> for x in ip:
        ...  print(repr(x))
        ...
        IP('127.0.0.0')
        IP('127.0.0.1')
        IP('127.0.0.2')
        IP('127.0.0.3')
        >>> ip[2]
        IP('127.0.0.2')
        >>> ip[-1]
        IP('127.0.0.3')
        """

        if not isinstance(key, (int, long)):
            raise TypeError
        if key < 0:
            if abs(key) <= self.len():
                key = self.len() - abs(key)
            else:
                raise IndexError
        else:
            if key >= self.len():
                raise IndexError

        return self.ip + long(key)



    def __contains__(self, item):
        """Called to implement membership test operators.

        Should return true if item is in self, false otherwise. Item
        can be other IP-objects, strings or ints.

        >>> IP('195.185.1.1').strHex()
        '0xc3b90101'
        >>> 0xC3B90101 in IP('195.185.1.0/24')
        True
        >>> '127.0.0.1' in IP('127.0.0.0/24')
        True
        >>> IP('127.0.0.0/24') in IP('127.0.0.0/25')
        False
        """

        item = IP(item)
        if item.ip >= self.ip and item.ip < self.ip + self.len() - item.len() + 1:
            return True
        else:
            return False


    def overlaps(self, item):
        """Check if two IP address ranges overlap.

        Returns 0 if the two ranges don't overlap, 1 if the given
        range overlaps at the end and -1 if it does at the beginning.

        >>> IP('192.168.0.0/23').overlaps('192.168.1.0/24')
        1
        >>> IP('192.168.0.0/23').overlaps('192.168.1.255')
        1
        >>> IP('192.168.0.0/23').overlaps('192.168.2.0')
        0
        >>> IP('192.168.1.0/24').overlaps('192.168.0.0/23')
        -1
        """

        item = IP(item)
        if item.ip >= self.ip and item.ip < self.ip + self.len():
            return 1
        elif self.ip >= item.ip and self.ip < item.ip + item.len():
            return -1
        else:
            return 0


    def __str__(self):
        """Dispatch to the prefered String Representation.

        Used to implement str(IP)."""

        return self.strCompressed()


    def __repr__(self):
        """Print a representation of the Object.

        Used to implement repr(IP). Returns a string which evaluates
        to an identical Object (without the wantprefixlen stuff - see
        module docstring.

        >>> print(repr(IP('10.0.0.0/24')))
        IP('10.0.0.0/24')
        """

        return("IPint('%s')" % (self.strCompressed(1)))


    def __cmp__(self, other):
        """Called by comparison operations.

        Should return a negative integer if self < other, zero if self
        == other, a positive integer if self > other.

        Networks with different prefixlen are considered non-equal.
        Networks with the same prefixlen and differing addresses are
        considered non equal but are compared by their base address
        integer value to aid sorting of IP objects.

        The version of Objects is not put into consideration.

        >>> IP('10.0.0.0/24') > IP('10.0.0.0')
        1
        >>> IP('10.0.0.0/24') < IP('10.0.0.0')
        0
        >>> IP('10.0.0.0/24') < IP('12.0.0.0/24')
        1
        >>> IP('10.0.0.0/24') > IP('12.0.0.0/24')
        0

        """

        # Im not really sure if this is "the right thing to do"
        if self._prefixlen < other.prefixlen():
            return (other.prefixlen() - self._prefixlen)
        elif self._prefixlen > other.prefixlen():

            # Fixed bySamuel Krempp <krempp@crans.ens-cachan.fr>:

            # The bug is quite obvious really (as 99% bugs are once
            # spotted, isn't it ? ;-) Because of precedence of
            # multiplication by -1 over the substraction, prefixlen
            # differences were causing the __cmp__ function to always
            # return positive numbers, thus the function was failing
            # the basic assumptions for a __cmp__ function.

            # Namely we could have (a > b AND b > a), when the
            # prefixlen of a and b are different.  (eg let
            # a=IP("1.0.0.0/24"); b=IP("2.0.0.0/16");) thus, anything
            # could happen when launching a sort algorithm..
            # everything's in order with the trivial, attached patch.

            return other.prefixlen() - self._prefixlen
        else:
            if self.ip < other.ip:
                return -1
            elif self.ip > other.ip:
                return 1
            elif self._ipversion != other._ipversion:
                # IP('0.0.0.0'), IP('::/0')
                if self._ipversion < other._ipversion:
                    return -1
                elif self._ipversion > other._ipversion:
                    return 1
                else:
                    return 0
            else:
                return 0

    def __eq__(self, other):
        return self.__cmp__(other) == 0

    def __lt__(self, other):
        return self.__cmp__(other) < 0

    def __hash__(self):
        """Called for the key object for dictionary operations, and by
        the built-in function hash(). Should return a 32-bit integer
        usable as a hash value for dictionary operations. The only
        required property is that objects which compare equal have the
        same hash value

        >>> IP('10.0.0.0/24').__hash__()
        -167772185
        """

        thehash = int(-1)
        ip = self.ip
        while ip > 0:
            thehash = thehash ^ (ip & 0x7fffffff)
            ip = ip >> 32
        thehash = thehash ^ self._prefixlen
        return int(thehash)


class IP(IPint):
    """Class for handling IP addresses and networks."""

    def net(self):
        """Return the base (first) address of a network as an IP object.

        The same as IP[0].

        >>> IP('10.0.0.0/8').net()
        IP('10.0.0.0')
        """
        return IP(IPint.net(self), ipversion=self._ipversion)

    def broadcast(self):
        """Return the broadcast (last) address of a network as an IP object.

        The same as IP[-1].

        >>> IP('10.0.0.0/8').broadcast()
        IP('10.255.255.255')
        """
        return IP(IPint.broadcast(self))

    def netmask(self):
        """Return netmask as an IP object.

        >>> IP('10.0.0.0/8').netmask()
        IP('255.0.0.0')
         """
        return IP(IPint.netmask(self), ipversion=self._ipversion)

    def _getIPv4Map(self):
        if self._ipversion != 6:
            return None
        if (self.ip >> 32) != 0xffff:
            return None
        ipv4 = self.ip & 0xffffffff
        if self._prefixlen != 128:
            ipv4 = '%s/%s' % (ipv4, 32-(128-self._prefixlen))
        return IP(ipv4, ipversion=4)

    def reverseNames(self):
        """Return a list with values forming the reverse lookup.

        >>> IP('213.221.113.87/32').reverseNames()
        ['87.113.221.213.in-addr.arpa.']
        >>> IP('213.221.112.224/30').reverseNames()
        ['224.112.221.213.in-addr.arpa.', '225.112.221.213.in-addr.arpa.', '226.112.221.213.in-addr.arpa.', '227.112.221.213.in-addr.arpa.']
        >>> IP('127.0.0.0/24').reverseNames()
        ['0.0.127.in-addr.arpa.']
        >>> IP('127.0.0.0/23').reverseNames()
        ['0.0.127.in-addr.arpa.', '1.0.127.in-addr.arpa.']
        >>> IP('127.0.0.0/16').reverseNames()
        ['0.127.in-addr.arpa.']
        >>> IP('127.0.0.0/15').reverseNames()
        ['0.127.in-addr.arpa.', '1.127.in-addr.arpa.']
        >>> IP('128.0.0.0/8').reverseNames()
        ['128.in-addr.arpa.']
        >>> IP('128.0.0.0/7').reverseNames()
        ['128.in-addr.arpa.', '129.in-addr.arpa.']
        >>> IP('::1:2').reverseNames()
        ['2.0.0.0.1.ip6.arpa.']
        """

        if self._ipversion == 4:
            ret = []
            # TODO: Refactor. Add support for IPint objects
            if self.len() < 2**8:
                for x in self:
                    ret.append(x.reverseName())
            elif self.len() < 2**16:
                for i in xrange(0, self.len(), 2**8):
                    ret.append(self[i].reverseName()[2:])
            elif self.len() < 2**24:
                for i in xrange(0, self.len(), 2**16):
                    ret.append(self[i].reverseName()[4:])
            else:
                for i in xrange(0, self.len(), 2**24):
                    ret.append(self[i].reverseName()[6:])
            return ret
        elif self._ipversion == 6:
            ipv4 = self._getIPv4Map()
            if ipv4 is not None:
                return ipv4.reverseNames()
            s = hex(self.ip)[2:].lower()
            if s[-1] == 'l':
                s = s[:-1]
            if self._prefixlen % 4 != 0:
                raise NotImplementedError("can't create IPv6 reverse names at sub nibble level")
            s = list(s)
            s.reverse()
            s = '.'.join(s)
            first_nibble_index = int(32 - (self._prefixlen // 4)) * 2
            return ["%s.ip6.arpa." % s[first_nibble_index:]]
        else:
            raise ValueError("only IPv4 and IPv6 supported")

    def reverseName(self):
        """Return the value for reverse lookup/PTR records as RFC 2317 look alike.

        RFC 2317 is an ugly hack which only works for sub-/24 e.g. not
        for /23. Do not use it. Better set up a zone for every
        address. See reverseName for a way to achieve that.

        >>> print(IP('195.185.1.1').reverseName())
        1.1.185.195.in-addr.arpa.
        >>> print(IP('195.185.1.0/28').reverseName())
        0-15.1.185.195.in-addr.arpa.
        >>> IP('::1:2').reverseName()
        '2.0.0.0.1.ip6.arpa.'
        """

        if self._ipversion == 4:
            s = self.strFullsize(0)
            s = s.split('.')
            s.reverse()
            first_byte_index = int(4 - (self._prefixlen // 8))
            if self._prefixlen % 8 != 0:
                nibblepart = "%s-%s" % (s[3-(self._prefixlen // 8)], intToIp(self.ip + self.len() - 1, 4).split('.')[-1])
                if nibblepart[-1] == 'l':
                    nibblepart = nibblepart[:-1]
                nibblepart += '.'
            else:
                nibblepart = ""

            s = '.'.join(s[first_byte_index:])
            return "%s%s.in-addr.arpa." % (nibblepart, s)

        elif self._ipversion == 6:
            ipv4 = self._getIPv4Map()
            if ipv4 is not None:
                return ipv4.reverseName()
            s = hex(self.ip)[2:].lower()
            if s[-1] == 'l':
                s = s[:-1]
            if self._prefixlen % 4 != 0:
                nibblepart = "%s-%s" % (s[self._prefixlen:], hex(self.ip + self.len() - 1)[2:].lower())
                if nibblepart[-1] == 'l':
                    nibblepart = nibblepart[:-1]
                nibblepart += '.'
            else:
                nibblepart = ""
            s = list(s)
            s.reverse()
            s = '.'.join(s)
            first_nibble_index = int(32 - (self._prefixlen // 4)) * 2
            return "%s%s.ip6.arpa." % (nibblepart, s[first_nibble_index:])
        else:
            raise ValueError("only IPv4 and IPv6 supported")

    def make_net(self, netmask):
        """Transform a single IP address into a network specification by
        applying the given netmask.

        Returns a new IP instance.

        >>> print(IP('127.0.0.1').make_net('255.0.0.0'))
        127.0.0.0/8
        """
        if '/' in str(netmask):
            raise ValueError("invalid netmask (%s)" % netmask)
        return IP('%s/%s' % (self, netmask), make_net=True)

    def __getitem__(self, key):
        """Called to implement evaluation of self[key].

        >>> ip=IP('127.0.0.0/30')
        >>> for x in ip:
        ...  print(str(x))
        ...
        127.0.0.0
        127.0.0.1
        127.0.0.2
        127.0.0.3
        >>> print(str(ip[2]))
        127.0.0.2
        >>> print(str(ip[-1]))
        127.0.0.3
        """
        return IP(IPint.__getitem__(self, key))

    def __repr__(self):
        """Print a representation of the Object.

        >>> IP('10.0.0.0/8')
        IP('10.0.0.0/8')
        """

        return("IP('%s')" % (self.strCompressed(1)))

    def __add__(self, other):
        """Emulate numeric objects through network aggregation"""
        if self.prefixlen() != other.prefixlen():
            raise ValueError("Only networks with the same prefixlen can be added.")
        if self.prefixlen() < 1:
            raise ValueError("Networks with a prefixlen longer than /1 can't be added.")
        if self.version() != other.version():
            raise ValueError("Only networks with the same IP version can be added.")
        if self > other:
            # fixed by Skinny Puppy <skin_pup-IPy@happypoo.com>
            return other.__add__(self)
        else:
            ret = IP(self.int())
            ret._prefixlen = self.prefixlen() - 1
            return ret


def _parseAddressIPv6(ipstr):
    """
    Internal function used by parseAddress() to parse IPv6 address with ':'.

    >>> print(_parseAddressIPv6('::'))
    0
    >>> print(_parseAddressIPv6('::1'))
    1
    >>> print(_parseAddressIPv6('0:0:0:0:0:0:0:1'))
    1
    >>> print(_parseAddressIPv6('0:0:0::0:0:1'))
    1
    >>> print(_parseAddressIPv6('0:0:0:0:0:0:0:0'))
    0
    >>> print(_parseAddressIPv6('0:0:0::0:0:0'))
    0

    >>> print(_parseAddressIPv6('FEDC:BA98:7654:3210:FEDC:BA98:7654:3210'))
    338770000845734292534325025077361652240
    >>> print(_parseAddressIPv6('1080:0000:0000:0000:0008:0800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('1080:0:0:0:8:800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('1080:0::8:800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('1080::8:800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('FF01:0:0:0:0:0:0:43'))
    338958331222012082418099330867817087043
    >>> print(_parseAddressIPv6('FF01:0:0::0:0:43'))
    338958331222012082418099330867817087043
    >>> print(_parseAddressIPv6('FF01::43'))
    338958331222012082418099330867817087043
    >>> print(_parseAddressIPv6('0:0:0:0:0:0:13.1.68.3'))
    218186755
    >>> print(_parseAddressIPv6('::13.1.68.3'))
    218186755
    >>> print(_parseAddressIPv6('0:0:0:0:0:FFFF:129.144.52.38'))
    281472855454758
    >>> print(_parseAddressIPv6('::FFFF:129.144.52.38'))
    281472855454758
    >>> print(_parseAddressIPv6('1080:0:0:0:8:800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('1080::8:800:200C:417A'))
    21932261930451111902915077091070067066
    >>> print(_parseAddressIPv6('::1:2:3:4:5:6'))
    1208962713947218704138246
    >>> print(_parseAddressIPv6('1:2:3:4:5:6::'))
    5192455318486707404433266432802816
    """

    # Split string into a list, example:
    #   '1080:200C::417A' => ['1080', '200C', '417A'] and fill_pos=2
    # and fill_pos is the position of '::' in the list
    items = []
    index = 0
    fill_pos = None
    while index < len(ipstr):
        text = ipstr[index:]
        if text.startswith("::"):
            if fill_pos is not None:
                # Invalid IPv6, eg. '1::2::'
                raise ValueError("%r: Invalid IPv6 address: more than one '::'" % ipstr)
            fill_pos = len(items)
            index += 2
            continue
        pos = text.find(':')
        if pos == 0:
            # Invalid IPv6, eg. '1::2:'
            raise ValueError("%r: Invalid IPv6 address" % ipstr)
        if pos != -1:
            items.append(text[:pos])
            if text[pos:pos+2] == "::":
                index += pos
            else:
                index += pos+1

            if index == len(ipstr):
                # Invalid IPv6, eg. '1::2:'
                raise ValueError("%r: Invalid IPv6 address" % ipstr)
        else:
            items.append(text)
            break

    if items and '.' in items[-1]:
        # IPv6 ending with IPv4 like '::ffff:192.168.0.1'
        if (fill_pos is not None) and not (fill_pos <= len(items)-1):
            # Invalid IPv6: 'ffff:192.168.0.1::'
            raise ValueError("%r: Invalid IPv6 address: '::' after IPv4" % ipstr)
        value = parseAddress(items[-1])[0]
        items = items[:-1] + ["%04x" % (value >> 16), "%04x" % (value & 0xffff)]

    # Expand fill_pos to fill with '0'
    # ['1','2'] with fill_pos=1 => ['1', '0', '0', '0', '0', '0', '0', '2']
    if fill_pos is not None:
        diff = 8 - len(items)
        if diff <= 0:
            raise ValueError("%r: Invalid IPv6 address: '::' is not needed" % ipstr)
        items = items[:fill_pos] + ['0']*diff + items[fill_pos:]

    # Here we have a list of 8 strings
    if len(items) != 8:
        # Invalid IPv6, eg. '1:2:3'
        raise ValueError("%r: Invalid IPv6 address: should have 8 hextets" % ipstr)

    # Convert strings to long integer
    value = 0
    index = 0
    for item in items:
        try:
            item = int(item, 16)
            error = not(0 <= item <= 0xFFFF)
        except ValueError:
            error = True
        if error:
            raise ValueError("%r: Invalid IPv6 address: invalid hexlet %r" % (ipstr, item))
        value = (value << 16) + item
        index += 1
    return value

def parseAddress(ipstr):
    """
    Parse a string and return the corresponding IP address (as integer)
    and a guess of the IP version.

    Following address formats are recognized:

    >>> def testParseAddress(address):
    ...     ip, version = parseAddress(address)
    ...     print(("%s (IPv%s)" % (ip, version)))
    ...
    >>> testParseAddress('0x0123456789abcdef')           # IPv4 if <= 0xffffffff else IPv6
    81985529216486895 (IPv6)
    >>> testParseAddress('123.123.123.123')              # IPv4
    2071690107 (IPv4)
    >>> testParseAddress('123.123')                      # 0-padded IPv4
    2071658496 (IPv4)
    >>> testParseAddress('1080:0000:0000:0000:0008:0800:200C:417A')
    21932261930451111902915077091070067066 (IPv6)
    >>> testParseAddress('1080:0:0:0:8:800:200C:417A')
    21932261930451111902915077091070067066 (IPv6)
    >>> testParseAddress('1080:0::8:800:200C:417A')
    21932261930451111902915077091070067066 (IPv6)
    >>> testParseAddress('::1')
    1 (IPv6)
    >>> testParseAddress('::')
    0 (IPv6)
    >>> testParseAddress('0:0:0:0:0:FFFF:129.144.52.38')
    281472855454758 (IPv6)
    >>> testParseAddress('::13.1.68.3')
    218186755 (IPv6)
    >>> testParseAddress('::FFFF:129.144.52.38')
    281472855454758 (IPv6)
    """

    if ipstr.startswith('0x'):
        ret = long(ipstr[2:], 16)
        if ret > 0xffffffffffffffffffffffffffffffff:
            raise ValueError("%r: IP Address can't be bigger than 2^128" % (ipstr))
        if ret < 0x100000000:
            return (ret, 4)
        else:
            return (ret, 6)

    if ipstr.find(':') != -1:
        return (_parseAddressIPv6(ipstr), 6)

    elif len(ipstr) == 32:
        # assume IPv6 in pure hexadecimal notation
        return (long(ipstr, 16), 6)

    elif  ipstr.find('.') != -1 or (len(ipstr) < 4 and int(ipstr) < 256):
        # assume IPv4  ('127' gets interpreted as '127.0.0.0')
        bytes = ipstr.split('.')
        if len(bytes) > 4:
            raise ValueError("IPv4 Address with more than 4 bytes")
        bytes += ['0'] * (4 - len(bytes))
        bytes = [long(x) for x in bytes]
        for x in bytes:
            if x > 255 or x < 0:
                raise ValueError("%r: single byte must be 0 <= byte < 256" % (ipstr))
        return ((bytes[0] << 24) + (bytes[1] << 16) + (bytes[2] << 8) + bytes[3], 4)

    else:
        # we try to interprete it as a decimal digit -
        # this ony works for numbers > 255 ... others
        # will be interpreted as IPv4 first byte
        ret = long(ipstr, 10)
        if ret > 0xffffffffffffffffffffffffffffffff:
            raise ValueError("IP Address can't be bigger than 2^128")
        if ret <= 0xffffffff:
            return (ret, 4)
        else:
            return (ret, 6)


def intToIp(ip, version):
    """Transform an integer string into an IP address."""

    # just to be sure and hoping for Python 2.22
    ip = long(ip)

    if ip < 0:
        raise ValueError("IPs can't be negative: %d" % (ip))

    ret = ''
    if version == 4:
        if ip > 0xffffffff:
            raise ValueError("IPv4 Addresses can't be larger than 0xffffffff: %s" % (hex(ip)))
        for l in xrange(4):
            ret = str(ip & 0xff) + '.' + ret
            ip = ip >> 8
        ret = ret[:-1]
    elif version == 6:
        if ip > 0xffffffffffffffffffffffffffffffff:
            raise ValueError("IPv6 Addresses can't be larger than 0xffffffffffffffffffffffffffffffff: %s" % (hex(ip)))
        if sys.hexversion >= 0x03000000:
            # Remove "0x" prefix
            l = hex(ip)[2:]
        else:
            # Remove "0x" prefix and "L" suffix
            l = hex(ip)[2:-1]
        l = l.zfill(32)
        for x in xrange(1, 33):
            ret = l[-x] + ret
            if x % 4 == 0:
                ret = ':' + ret
        ret = ret[1:]
    else:
        raise ValueError("only IPv4 and IPv6 supported")

    return ret

def _ipVersionToLen(version):
    """Return number of bits in address for a certain IP version.

    >>> _ipVersionToLen(4)
    32
    >>> _ipVersionToLen(6)
    128
    >>> _ipVersionToLen(5)
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
      File "IPy.py", line 1076, in _ipVersionToLen
        raise ValueError("only IPv4 and IPv6 supported")
    ValueError: only IPv4 and IPv6 supported
    """

    if version == 4:
        return 32
    elif version == 6:
        return 128
    else:
        raise ValueError("only IPv4 and IPv6 supported")


def _countFollowingZeros(l):
    """Return number of elements containing 0 at the beginning of the list."""
    if len(l) == 0:
        return 0
    elif l[0] != 0:
        return 0
    else:
        return 1 + _countFollowingZeros(l[1:])


_BitTable = {'0': '0000', '1': '0001', '2': '0010', '3': '0011',
            '4': '0100', '5': '0101', '6': '0110', '7': '0111',
            '8': '1000', '9': '1001', 'a': '1010', 'b': '1011',
            'c': '1100', 'd': '1101', 'e': '1110', 'f': '1111'}

def _intToBin(val):
    """Return the binary representation of an integer as string."""

    if val < 0:
        raise ValueError("Only positive values allowed")
    s = hex(val).lower()
    ret = ''
    if s[-1] == 'l':
        s = s[:-1]
    for x in s[2:]:
        ret += _BitTable[x]
    # remove leading zeros
    while ret[0] == '0' and len(ret) > 1:
        ret = ret[1:]
    return ret

def _count1Bits(num):
    """Find the highest bit set to 1 in an integer."""
    ret = 0
    while num > 0:
        num = num >> 1
        ret += 1
    return ret

def _count0Bits(num):
    """Find the highest bit set to 0 in an integer."""

    # this could be so easy if _count1Bits(~long(num)) would work as excepted
    num = long(num)
    if num < 0:
        raise ValueError("Only positive Numbers please: %s" % (num))
    ret = 0
    while num > 0:
        if num & 1 == 1:
            break
        num = num >> 1
        ret += 1
    return ret


def _checkPrefix(ip, prefixlen, version):
    """Check the validity of a prefix

    Checks if the variant part of a prefix only has 0s, and the length is
    correct.

    >>> _checkPrefix(0x7f000000, 24, 4)
    1
    >>> _checkPrefix(0x7f000001, 24, 4)
    0
    >>> repr(_checkPrefix(0x7f000001, -1, 4))
    'None'
    >>> repr(_checkPrefix(0x7f000001, 33, 4))
    'None'
    """

    # TODO: unify this v4/v6/invalid code in a function
    bits = _ipVersionToLen(version)

    if prefixlen < 0 or prefixlen > bits:
        return None

    if ip == 0:
        zbits = bits + 1
    else:
        zbits = _count0Bits(ip)
    if zbits <  bits - prefixlen:
        return 0
    else:
        return 1


def _checkNetmask(netmask, masklen):
    """Checks if a netmask is expressable as a prefixlen."""

    num = long(netmask)
    bits = masklen

    # remove zero bits at the end
    while (num & 1) == 0 and bits != 0:
        num = num >> 1
        bits -= 1
        if bits == 0:
            break
    # now check if the rest consists only of ones
    while bits > 0:
        if (num & 1) == 0:
            raise ValueError("Netmask %s can't be expressed as an prefix." % (hex(netmask)))
        num = num >> 1
        bits -= 1


def _checkNetaddrWorksWithPrefixlen(net, prefixlen, version):
    """Check if a base addess of a network is compatible with a prefixlen"""
    return (net & _prefixlenToNetmask(prefixlen, version) == net)


def _netmaskToPrefixlen(netmask):
    """Convert an Integer representing a netmask to a prefixlen.

    E.g. 0xffffff00 (255.255.255.0) returns 24
    """

    netlen = _count0Bits(netmask)
    masklen = _count1Bits(netmask)
    _checkNetmask(netmask, masklen)
    return masklen - netlen


def _prefixlenToNetmask(prefixlen, version):
    """Return a mask of n bits as a long integer.

    From 'IP address conversion functions with the builtin socket module'
    by Alex Martelli
    http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66517
    """
    if prefixlen == 0:
        return 0
    elif prefixlen < 0:
        raise ValueError("Prefixlen must be > 0")
    return ((2<<prefixlen-1)-1) << (_ipVersionToLen(version) - prefixlen)


if __name__ == "__main__":
    import doctest
    failure, nbtest = doctest.testmod()
    if failure:
        import sys
        sys.exit(1)