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
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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
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     11  # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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     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