text: # Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
  #
  # Permission to use, copy, modify, and distribute this software and its
  # documentation for any purpose with or without fee is hereby granted,
  # provided that the above copyright notice and this permission notice
  # appear in all copies.
  #
  # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
  # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  
  """DNS Rdata Classes.
  
  @var _by_text: The rdata class textual name to value mapping
  @type _by_text: dict
  @var _by_value: The rdata class value to textual name mapping
  @type _by_value: dict
  @var _metaclasses: If an rdataclass is a metaclass, there will be a mapping
  whose key is the rdatatype value and whose value is True in this dictionary.
  @type _metaclasses: dict"""
  
  import re
  
  import rmrb_play_ctrl.core.dns.exception
  
  RESERVED0 = 0
  IN = 1
  CH = 3
  HS = 4
  NONE = 254
  ANY = 255
  
  _by_text = {
      'RESERVED0': RESERVED0,
      'IN': IN,
      'CH': CH,
      'HS': HS,
      'NONE': NONE,
      'ANY': ANY
  }
  
  # We construct the inverse mapping programmatically to ensure that we
  # cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
  # would cause the mapping not to be true inverse.
  
  _by_value = dict((y, x) for x, y in _by_text.items())
  
  # Now that we've built the inverse map, we can add class aliases to
  # the _by_text mapping.
  
  _by_text.update({
      'INTERNET': IN,
      'CHAOS': CH,
      'HESIOD': HS
  })
  
  _metaclasses = {
      NONE: True,
      ANY: True
  }
  
  _unknown_class_pattern = re.compile('CLASS([0-9]+)$', re.I)
  
  
  class UnknownRdataclass(rmrb_play_ctrl.core.dns.exception.DNSException):
  
      """A DNS class is unknown."""
  
  
  def from_text(text):
      """Convert text into a DNS rdata class value.
      @param text: the text
      @type text: string
      @rtype: int
      @raises rmrb_play_ctrl.core.dns.rdataclass.UnknownRdataclass: the class is unknown
      @raises ValueError: the rdata class value is not >= 0 and <= 65535
      """
  
      value = _by_text.get(text.upper())
      if value is None:
          match = _unknown_class_pattern.match(text)
          if match is None:
              raise UnknownRdataclass
          value = int(match.group(1))
          if value < 0 or value > 65535:
              raise ValueError("class must be between >= 0 and <= 65535")
      return value
  
  
  def to_text(value):
      """Convert a DNS rdata class to text.
      @param value: the rdata class value
      @type value: int
      @rtype: string
      @raises ValueError: the rdata class value is not >= 0 and <= 65535
      """
  
      if value < 0 or value > 65535:
          raise ValueError("class must be between >= 0 and <= 65535")
      text = _by_value.get(value)
      if text is None:
          text = 'CLASS' + repr(value)
      return text
  
  
  def is_metaclass(rdclass):
      """True if the class is a metaclass.
      @param rdclass: the rdata class
      @type rdclass: int
      @rtype: bool"""
  
      if rdclass in _metaclasses:
          return True
      return False
  