Source Code for Module dns.opcode

  1  # Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license 
  2   
  3  # Copyright (C) 2001-2017 Nominum, Inc. 
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 17   
 18  """DNS Opcodes.""" 
 19   
 20  import dns.exception 
 21   
 22  #: Query 
 23  QUERY = 0 
 24  #: Inverse Query (historical) 
 25  IQUERY = 1 
 26  #: Server Status (unspecified and unimplemented anywhere) 
 27  STATUS = 2 
 28  #: Notify 
 29  NOTIFY = 4 
 30  #: Dynamic Update 
 31  UPDATE = 5 
 32   
 33  _by_text = { 
 34      'QUERY': QUERY, 
 35      'IQUERY': IQUERY, 
 36      'STATUS': STATUS, 
 37      'NOTIFY': NOTIFY, 
 38      'UPDATE': UPDATE 
 39  } 
 40   
 41  # We construct the inverse mapping programmatically to ensure that we 
 42  # cannot make any mistakes (e.g. omissions, cut-and-paste errors) that 
 43  # would cause the mapping not to be true inverse. 
 44   
 45  _by_value = {y: x for x, y in _by_text.items()} 
 46   
 47   
 48 -class UnknownOpcode(dns.exception.DNSException): 
 49      """An DNS opcode is unknown.""" 
 50   
 51   
 52 -def from_text(text): 
 53      """Convert text into an opcode. 
 54   
 55      *text*, a ``text``, the textual opcode 
 56   
 57      Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown. 
 58   
 59      Returns an ``int``. 
 60      """ 
 61   
 62      if text.isdigit(): 
 63          value = int(text) 
 64          if value >= 0 and value <= 15: 
 65              return value 
 66      value = _by_text.get(text.upper()) 
 67      if value is None: 
 68          raise UnknownOpcode 
 69      return value 
 70   
 71   
 72 -def from_flags(flags): 
 73      """Extract an opcode from DNS message flags. 
 74   
 75      *flags*, an ``int``, the DNS flags. 
 76   
 77      Returns an ``int``. 
 78      """ 
 79   
 80      return (flags & 0x7800) >> 11 
 81   
 82   
 83 -def to_flags(value): 
 84      """Convert an opcode to a value suitable for ORing into DNS message 
 85      flags. 
 86   
 87      *value*, an ``int``, the DNS opcode value. 
 88   
 89      Returns an ``int``. 
 90      """ 
 91   
 92      return (value << 11) & 0x7800 
 93   
 94   
 95 -def to_text(value): 
 96      """Convert an opcode to text. 
 97   
 98      *value*, an ``int`` the opcode value, 
 99   
100      Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown. 
101   
102      Returns a ``text``. 
103      """ 
104   
105      text = _by_value.get(value) 
106      if text is None: 
107          text = str(value) 
108      return text 
109   
110   
111 -def is_update(flags): 
112      """Is the opcode in flags UPDATE? 
113   
114      *flags*, an ``int``, the DNS message flags. 
115   
116      Returns a ``bool``. 
117      """ 
118   
119      return from_flags(flags) == UPDATE 
120