Source Code for Module dns.rdataclass

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