lib/dnspython/dns/rdataclass.py

   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
  23 whose key is the rdatatype value and whose value is True in this dictionary.
  24 @type _metaclasses: dict"""
  25
  26 import re
  27
  28 import dns.exception
  29
  30 RESERVED0 = 0
  31 IN = 1
  32 CH = 3
  33 HS = 4
  34 NONE = 254
  35 ANY = 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
  68 class UnknownRdataclass(dns.exception.DNSException):
  69     """Raised when a class is unknown."""
  70     pass
  71
  72 def 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
  91 def 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
 106 def 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