source: vendor/3.6.0/lib/dnspython/dns/inet.py

# Copyright (C) 2003-2007, 2009, 2010 Nominum, Inc.
#
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# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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"""Generic Internet address helper functions."""

import socket

import dns.ipv4
import dns.ipv6


# We assume that AF_INET is always defined.

AF_INET = socket.AF_INET

# AF_INET6 might not be defined in the socket module, but we need it.
# We'll try to use the socket module's value, and if it doesn't work,
# we'll use our own value.

try:
    AF_INET6 = socket.AF_INET6
except AttributeError:
    AF_INET6 = 9999

def inet_pton(family, text):
    """Convert the textual form of a network address into its binary form.

    @param family: the address family
    @type family: int
    @param text: the textual address
    @type text: string
    @raises NotImplementedError: the address family specified is not
    implemented.
    @rtype: string
    """
    
    if family == AF_INET:
        return dns.ipv4.inet_aton(text)
    elif family == AF_INET6:
        return dns.ipv6.inet_aton(text)
    else:
        raise NotImplementedError

def inet_ntop(family, address):
    """Convert the binary form of a network address into its textual form.

    @param family: the address family
    @type family: int
    @param address: the binary address
    @type address: string
    @raises NotImplementedError: the address family specified is not
    implemented.
    @rtype: string
    """
    if family == AF_INET:
        return dns.ipv4.inet_ntoa(address)
    elif family == AF_INET6:
        return dns.ipv6.inet_ntoa(address)
    else:
        raise NotImplementedError

def af_for_address(text):
    """Determine the address family of a textual-form network address.

    @param text: the textual address
    @type text: string
    @raises ValueError: the address family cannot be determined from the input.
    @rtype: int
    """
    try:
        junk = dns.ipv4.inet_aton(text)
        return AF_INET
    except:
        try:
            junk = dns.ipv6.inet_aton(text)
            return AF_INET6
        except:
            raise ValueError

def is_multicast(text):
    """Is the textual-form network address a multicast address?

    @param text: the textual address
    @raises ValueError: the address family cannot be determined from the input.
    @rtype: bool
    """
    try:
        first = ord(dns.ipv4.inet_aton(text)[0])
        return (first >= 224 and first <= 239)
    except:
        try:
            first = ord(dns.ipv6.inet_aton(text)[0])
            return (first == 255)
        except:
            raise ValueError