1# Copyright (C) 2001-2007, 2009-2011 Nominum, Inc. 2# 3# Permission to use, copy, modify, and distribute this software and its 4# documentation for any purpose with or without fee is hereby granted, 5# provided that the above copyright notice and this permission notice 6# appear in all copies. 7# 8# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES 9# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR 11# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 14# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 16"""DNS Rdata Classes. 17 18@var _by_text: The rdata class textual name to value mapping 19@type _by_text: dict 20@var _by_value: The rdata class value to textual name mapping 21@type _by_value: dict 22@var _metaclasses: If an rdataclass is a metaclass, there will be a mapping 23whose key is the rdatatype value and whose value is True in this dictionary. 24@type _metaclasses: dict""" 25 26import re 27 28import dns.exception 29 30RESERVED0 = 0 31IN = 1 32CH = 3 33HS = 4 34NONE = 254 35ANY = 255 36 37_by_text = { 38 'RESERVED0': RESERVED0, 39 'IN': IN, 40 'CH': CH, 41 'HS': HS, 42 'NONE': NONE, 43 'ANY': ANY 44} 45 46# We construct the inverse mapping programmatically to ensure that we 47# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that 48# would cause the mapping not to be true inverse. 49 50_by_value = dict((y, x) for x, y in _by_text.items()) 51 52# Now that we've built the inverse map, we can add class aliases to 53# the _by_text mapping. 54 55_by_text.update({ 56 'INTERNET': IN, 57 'CHAOS': CH, 58 'HESIOD': HS 59}) 60 61_metaclasses = { 62 NONE: True, 63 ANY: True 64} 65 66_unknown_class_pattern = re.compile('CLASS([0-9]+)$', re.I) 67 68 69class UnknownRdataclass(dns.exception.DNSException): 70 71 """A DNS class is unknown.""" 72 73 74def from_text(text): 75 """Convert text into a DNS rdata class value. 76 @param text: the text 77 @type text: string 78 @rtype: int 79 @raises dns.rdataclass.UnknownRdataclass: the class is unknown 80 @raises ValueError: the rdata class value is not >= 0 and <= 65535 81 """ 82 83 value = _by_text.get(text.upper()) 84 if value is None: 85 match = _unknown_class_pattern.match(text) 86 if match is None: 87 raise UnknownRdataclass 88 value = int(match.group(1)) 89 if value < 0 or value > 65535: 90 raise ValueError("class must be between >= 0 and <= 65535") 91 return value 92 93 94def to_text(value): 95 """Convert a DNS rdata class to text. 96 @param value: the rdata class value 97 @type value: int 98 @rtype: string 99 @raises ValueError: the rdata class value is not >= 0 and <= 65535 100 """ 101 102 if value < 0 or value > 65535: 103 raise ValueError("class must be between >= 0 and <= 65535") 104 text = _by_value.get(value) 105 if text is None: 106 text = 'CLASS' + repr(value) 107 return text 108 109 110def is_metaclass(rdclass): 111 """True if the class is a metaclass. 112 @param rdclass: the rdata class 113 @type rdclass: int 114 @rtype: bool""" 115 116 if rdclass in _metaclasses: 117 return True 118 return False 119