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- # Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
- #
- # Permission to use, copy, modify, and distribute this software and its
- # documentation for any purpose with or without fee is hereby granted,
- # provided that the above copyright notice and this permission notice
- # appear in all copies.
- #
- # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
- # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
- # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
- # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
- # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
- """DNS Opcodes."""
- import dns.exception
- QUERY = 0
- IQUERY = 1
- STATUS = 2
- NOTIFY = 4
- UPDATE = 5
- _by_text = {
- 'QUERY': QUERY,
- 'IQUERY': IQUERY,
- 'STATUS': STATUS,
- 'NOTIFY': NOTIFY,
- 'UPDATE': UPDATE
- }
- # We construct the inverse mapping programmatically to ensure that we
- # cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
- # would cause the mapping not to be true inverse.
- _by_value = dict((y, x) for x, y in _by_text.items())
- class UnknownOpcode(dns.exception.DNSException):
- """An DNS opcode is unknown."""
- def from_text(text):
- """Convert text into an opcode.
- @param text: the textual opcode
- @type text: string
- @raises UnknownOpcode: the opcode is unknown
- @rtype: int
- """
- if text.isdigit():
- value = int(text)
- if value >= 0 and value <= 15:
- return value
- value = _by_text.get(text.upper())
- if value is None:
- raise UnknownOpcode
- return value
- def from_flags(flags):
- """Extract an opcode from DNS message flags.
- @param flags: int
- @rtype: int
- """
- return (flags & 0x7800) >> 11
- def to_flags(value):
- """Convert an opcode to a value suitable for ORing into DNS message
- flags.
- @rtype: int
- """
- return (value << 11) & 0x7800
- def to_text(value):
- """Convert an opcode to text.
- @param value: the opcdoe
- @type value: int
- @raises UnknownOpcode: the opcode is unknown
- @rtype: string
- """
- text = _by_value.get(value)
- if text is None:
- text = str(value)
- return text
- def is_update(flags):
- """True if the opcode in flags is UPDATE.
- @param flags: DNS flags
- @type flags: int
- @rtype: bool
- """
- return from_flags(flags) == UPDATE
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