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.items()) 
 39   
 40   
 41 -class UnknownOpcode(dns.exception.DNSException): 
 42   
 43      """An DNS opcode is unknown.""" 
 44   
 45   
 46 -def from_text(text): 
 47      """Convert text into an opcode. 
 48   
 49      @param text: the textual opcode 
 50      @type text: string 
 51      @raises UnknownOpcode: the opcode is unknown 
 52      @rtype: int 
 53      """ 
 54   
 55      if text.isdigit(): 
 56          value = int(text) 
 57          if value >= 0 and value <= 15: 
 58              return value 
 59      value = _by_text.get(text.upper()) 
 60      if value is None: 
 61          raise UnknownOpcode 
 62      return value 
 63   
 64   
 65 -def from_flags(flags): 
 66      """Extract an opcode from DNS message flags. 
 67   
 68      @param flags: int 
 69      @rtype: int 
 70      """ 
 71   
 72      return (flags & 0x7800) >> 11 
 73   
 74   
 75 -def to_flags(value): 
 76      """Convert an opcode to a value suitable for ORing into DNS message 
 77      flags. 
 78      @rtype: int 
 79      """ 
 80   
 81      return (value << 11) & 0x7800 
 82   
 83   
 84 -def to_text(value): 
 85      """Convert an opcode to text. 
 86   
 87      @param value: the opcdoe 
 88      @type value: int 
 89      @raises UnknownOpcode: the opcode is unknown 
 90      @rtype: string 
 91      """ 
 92   
 93      text = _by_value.get(value) 
 94      if text is None: 
 95          text = str(value) 
 96      return text 
 97   
 98   
 99 -def is_update(flags): 
100      """True if the opcode in flags is UPDATE. 
101   
102      @param flags: DNS flags 
103      @type flags: int 
104      @rtype: bool 
105      """ 
106   
107      return from_flags(flags) == UPDATE 
108