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104 lines
3.6 KiB
104 lines
3.6 KiB
6 years ago
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# Copyright (C) 2011 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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"""DNS Wire Data Helper"""
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import sys
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import dns.exception
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from ._compat import binary_type, string_types
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# Figure out what constant python passes for an unspecified slice bound.
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# It's supposed to be sys.maxint, yet on 64-bit windows sys.maxint is 2^31 - 1
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# but Python uses 2^63 - 1 as the constant. Rather than making pointless
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# extra comparisons, duplicating code, or weakening WireData, we just figure
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# out what constant Python will use.
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class _SliceUnspecifiedBound(binary_type):
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def __getitem__(self, key):
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return key.stop
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if sys.version_info < (3,):
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def __getslice__(self, i, j): # pylint: disable=getslice-method
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return self.__getitem__(slice(i, j))
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_unspecified_bound = _SliceUnspecifiedBound()[1:]
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class WireData(binary_type):
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# WireData is a string with stricter slicing
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def __getitem__(self, key):
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try:
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if isinstance(key, slice):
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# make sure we are not going outside of valid ranges,
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# do stricter control of boundaries than python does
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# by default
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start = key.start
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stop = key.stop
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if sys.version_info < (3,):
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if stop == _unspecified_bound:
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# handle the case where the right bound is unspecified
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stop = len(self)
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if start < 0 or stop < 0:
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raise dns.exception.FormError
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# If it's not an empty slice, access left and right bounds
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# to make sure they're valid
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if start != stop:
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super(WireData, self).__getitem__(start)
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super(WireData, self).__getitem__(stop - 1)
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else:
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for index in (start, stop):
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if index is None:
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continue
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elif abs(index) > len(self):
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raise dns.exception.FormError
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return WireData(super(WireData, self).__getitem__(
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slice(start, stop)))
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return bytearray(self.unwrap())[key]
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except IndexError:
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raise dns.exception.FormError
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if sys.version_info < (3,):
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def __getslice__(self, i, j): # pylint: disable=getslice-method
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return self.__getitem__(slice(i, j))
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def __iter__(self):
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i = 0
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while 1:
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try:
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yield self[i]
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i += 1
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except dns.exception.FormError:
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raise StopIteration
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def unwrap(self):
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return binary_type(self)
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def maybe_wrap(wire):
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if isinstance(wire, WireData):
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return wire
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elif isinstance(wire, binary_type):
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return WireData(wire)
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elif isinstance(wire, string_types):
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return WireData(wire.encode())
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raise ValueError("unhandled type %s" % type(wire))
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