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

      1  # Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
      2  #
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      4  # documentation for any purpose with or without fee is hereby granted,
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      8  # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
      9  # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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     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
    115