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

      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 Message Flags."""
     17
     18  # Standard DNS flags
     19
     20  QR = 0x8000
     21  AA = 0x0400
     22  TC = 0x0200
     23  RD = 0x0100
     24  RA = 0x0080
     25  AD = 0x0020
     26  CD = 0x0010
     27
     28  # EDNS flags
     29
     30  DO = 0x8000
     31
     32  _by_text = {
     33      'QR' : QR,
     34      'AA' : AA,
     35      'TC' : TC,
     36      'RD' : RD,
     37      'RA' : RA,
     38      'AD' : AD,
     39      'CD' : CD
     40  }
     41
     42  _edns_by_text = {
     43      'DO' : DO
     44  }
     45
     46
     47  # We construct the inverse mappings programmatically to ensure that we
     48  # cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
     49  # would cause the mappings not to be true inverses.
     50
     51  _by_value = dict([(y, x) for x, y in _by_text.iteritems()])
     52
     53  _edns_by_value = dict([(y, x) for x, y in _edns_by_text.iteritems()])
     54
     55 -def _order_flags(table):
     56      order = list(table.iteritems())
     57      order.sort()
     58      order.reverse()
     59      return order
     60
     61  _flags_order = _order_flags(_by_value)
     62
     63  _edns_flags_order = _order_flags(_edns_by_value)
     64
     65 -def _from_text(text, table):
     66      flags = 0
     67      tokens = text.split()
     68      for t in tokens:
     69          flags = flags | table[t.upper()]
     70      return flags
     71
     72 -def _to_text(flags, table, order):
     73      text_flags = []
     74      for k, v in order:
     75          if flags & k != 0:
     76              text_flags.append(v)
     77      return ' '.join(text_flags)
     78
     79 -def from_text(text):
     80      """Convert a space-separated list of flag text values into a flags
     81      value.
     82      @rtype: int"""
     83
     84      return _from_text(text, _by_text)
     85
     86 -def to_text(flags):
     87      """Convert a flags value into a space-separated list of flag text
     88      values.
     89      @rtype: string"""
     90
     91      return _to_text(flags, _by_value, _flags_order)
     92
     93
     94 -def edns_from_text(text):
     95      """Convert a space-separated list of EDNS flag text values into a EDNS
     96      flags value.
     97      @rtype: int"""
     98
     99      return _from_text(text, _edns_by_text)
    100
    101 -def edns_to_text(flags):
    102      """Convert an EDNS flags value into a space-separated list of EDNS flag
    103      text values.
    104      @rtype: string"""
    105
    106      return _to_text(flags, _edns_by_value, _edns_flags_order)
    107