Source Code for Module dns.opcode

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