1# Copyright (C) 2001-2007, 2009, 2010 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.iteritems()])
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
68class UnknownRdataclass(dns.exception.DNSException):
69    """Raised when a class is unknown."""
70    pass
71
72def from_text(text):
73    """Convert text into a DNS rdata class value.
74    @param text: the text
75    @type text: string
76    @rtype: int
77    @raises dns.rdataclass.UnknownRdataClass: the class is unknown
78    @raises ValueError: the rdata class value is not >= 0 and <= 65535
79    """
80
81    value = _by_text.get(text.upper())
82    if value is None:
83        match = _unknown_class_pattern.match(text)
84        if match == None:
85            raise UnknownRdataclass
86        value = int(match.group(1))
87        if value < 0 or value > 65535:
88            raise ValueError("class must be between >= 0 and <= 65535")
89    return value
90
91def to_text(value):
92    """Convert a DNS rdata class to text.
93    @param value: the rdata class value
94    @type value: int
95    @rtype: string
96    @raises ValueError: the rdata class value is not >= 0 and <= 65535
97    """
98
99    if value < 0 or value > 65535:
100        raise ValueError("class must be between >= 0 and <= 65535")
101    text = _by_value.get(value)
102    if text is None:
103        text = 'CLASS' + `value`
104    return text
105
106def is_metaclass(rdclass):
107    """True if the class is a metaclass.
108    @param rdclass: the rdata class
109    @type rdclass: int
110    @rtype: bool"""
111
112    if _metaclasses.has_key(rdclass):
113        return True
114    return False
115