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.items())
     52
     53  _edns_by_value = dict((y, x) for x, y in _edns_by_text.items())
     54
     55
     56 -def _order_flags(table):
     57      order = list(table.items())
     58      order.sort()
     59      order.reverse()
     60      return order
     61
     62  _flags_order = _order_flags(_by_value)
     63
     64  _edns_flags_order = _order_flags(_edns_by_value)
     65
     66
     67 -def _from_text(text, table):
     68      flags = 0
     69      tokens = text.split()
     70      for t in tokens:
     71          flags = flags | table[t.upper()]
     72      return flags
     73
     74
     75 -def _to_text(flags, table, order):
     76      text_flags = []
     77      for k, v in order:
     78          if flags & k != 0:
     79              text_flags.append(v)
     80      return ' '.join(text_flags)
     81
     82
     83 -def from_text(text):
     84      """Convert a space-separated list of flag text values into a flags
     85      value.
     86      @rtype: int"""
     87
     88      return _from_text(text, _by_text)
     89
     90
     91 -def to_text(flags):
     92      """Convert a flags value into a space-separated list of flag text
     93      values.
     94      @rtype: string"""
     95
     96      return _to_text(flags, _by_value, _flags_order)
     97
     98
     99 -def edns_from_text(text):
    100      """Convert a space-separated list of EDNS flag text values into a EDNS
    101      flags value.
    102      @rtype: int"""
    103
    104      return _from_text(text, _edns_by_text)
    105
    106
    107 -def edns_to_text(flags):
    108      """Convert an EDNS flags value into a space-separated list of EDNS flag
    109      text values.
    110      @rtype: string"""
    111
    112      return _to_text(flags, _edns_by_value, _edns_flags_order)
    113