Package dns :: Module opcode
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Source Code for Module dns.opcode

  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 Opcodes.""" 
 17   
 18  import dns.exception 
 19   
 20  QUERY = 0 
 21  IQUERY = 1 
 22  STATUS = 2 
 23  NOTIFY = 4 
 24  UPDATE = 5 
 25   
 26  _by_text = { 
 27      'QUERY' : QUERY, 
 28      'IQUERY' : IQUERY, 
 29      'STATUS' : STATUS, 
 30      'NOTIFY' : NOTIFY, 
 31      'UPDATE' : UPDATE 
 32  } 
 33   
 34  # We construct the inverse mapping programmatically to ensure that we 
 35  # cannot make any mistakes (e.g. omissions, cut-and-paste errors) that 
 36  # would cause the mapping not to be true inverse. 
 37   
 38  _by_value = dict([(y, x) for x, y in _by_text.iteritems()]) 
 39   
 40   
41 -class UnknownOpcode(dns.exception.DNSException):
42 """Raised if an opcode is unknown.""" 43 pass
44
45 -def from_text(text):
46 """Convert text into an opcode. 47 48 @param text: the textual opcode 49 @type text: string 50 @raises UnknownOpcode: the opcode is unknown 51 @rtype: int 52 """ 53 54 if text.isdigit(): 55 value = int(text) 56 if value >= 0 and value <= 15: 57 return value 58 value = _by_text.get(text.upper()) 59 if value is None: 60 raise UnknownOpcode 61 return value
62
63 -def from_flags(flags):
64 """Extract an opcode from DNS message flags. 65 66 @param flags: int 67 @rtype: int 68 """ 69 70 return (flags & 0x7800) >> 11
71
72 -def to_flags(value):
73 """Convert an opcode to a value suitable for ORing into DNS message 74 flags. 75 @rtype: int 76 """ 77 78 return (value << 11) & 0x7800
79
80 -def to_text(value):
81 """Convert an opcode to text. 82 83 @param value: the opcdoe 84 @type value: int 85 @raises UnknownOpcode: the opcode is unknown 86 @rtype: string 87 """ 88 89 text = _by_value.get(value) 90 if text is None: 91 text = str(value) 92 return text
93
94 -def is_update(flags):
95 """True if the opcode in flags is UPDATE. 96 97 @param flags: DNS flags 98 @type flags: int 99 @rtype: bool 100 """ 101 102 if (from_flags(flags) == UPDATE): 103 return True 104 return False
105