Package dns :: Module rdataclass
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Source Code for Module dns.rdataclass

  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 
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 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.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 = frozenset([NONE, ANY]) 
 62   
 63  _unknown_class_pattern = re.compile('CLASS([0-9]+)$', re.I); 
 64   
65 -class UnknownRdataclass(dns.exception.DNSException):
66 """Raised when a class is unknown.""" 67 pass
68
69 -def from_text(text):
70 """Convert text into a DNS rdata class value. 71 @param text: the text 72 @type text: string 73 @rtype: int 74 @raises dns.rdataclass.UnknownRdataclass: the class is unknown 75 @raises ValueError: the rdata class value is not >= 0 and <= 65535 76 """ 77 78 value = _by_text.get(text.upper()) 79 if value is None: 80 match = _unknown_class_pattern.match(text) 81 if match == None: 82 raise UnknownRdataclass 83 value = int(match.group(1)) 84 if value < 0 or value > 65535: 85 raise ValueError("class must be between >= 0 and <= 65535") 86 return value
87
88 -def to_text(value):
89 """Convert a DNS rdata class to text. 90 @param value: the rdata class value 91 @type value: int 92 @rtype: string 93 @raises ValueError: the rdata class value is not >= 0 and <= 65535 94 """ 95 96 if value < 0 or value > 65535: 97 raise ValueError("class must be between >= 0 and <= 65535") 98 text = _by_value.get(value) 99 if text is None: 100 text = 'CLASS' + str(value) 101 return text
102
103 -def is_metaclass(rdclass):
104 """True if the class is a metaclass. 105 @param rdclass: the rdata class 106 @type rdclass: int 107 @rtype: bool""" 108 109 if rdclass in _metaclasses: 110 return True 111 return False
112