lib/dnspython/dns/flags.py

   1 # Copyright (C) 2001-2007, 2009, 2010 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.
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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
  10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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  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)