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# Copyright (C) 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 Wire Data Helper"""
import sys
import dns.exception
from ._compat import binary_type, string_types
# Figure out what constant python passes for an unspecified slice bound.
# It's supposed to be sys.maxint, yet on 64-bit windows sys.maxint is 2^31 - 1
# but Python uses 2^63 - 1 as the constant. Rather than making pointless
# extra comparisons, duplicating code, or weakening WireData, we just figure
# out what constant Python will use.
class _SliceUnspecifiedBound(binary_type):
def __getitem__(self, key):
return key.stop
if sys.version_info < (3,):
def __getslice__(self, i, j): # pylint: disable=getslice-method
return self.__getitem__(slice(i, j))
_unspecified_bound = _SliceUnspecifiedBound()[1:]
class WireData(binary_type):
# WireData is a string with stricter slicing
def __getitem__(self, key):
try:
if isinstance(key, slice):
# make sure we are not going outside of valid ranges,
# do stricter control of boundaries than python does
# by default
start = key.start
stop = key.stop
if sys.version_info < (3,):
if stop == _unspecified_bound:
# handle the case where the right bound is unspecified
stop = len(self)
if start < 0 or stop < 0:
raise dns.exception.FormError
# If it's not an empty slice, access left and right bounds
# to make sure they're valid
if start != stop:
super(WireData, self).__getitem__(start)
super(WireData, self).__getitem__(stop - 1)
else:
for index in (start, stop):
if index is None:
continue
elif abs(index) > len(self):
raise dns.exception.FormError
return WireData(super(WireData, self).__getitem__(
slice(start, stop)))
return bytearray(self.unwrap())[key]
except IndexError:
raise dns.exception.FormError
if sys.version_info < (3,):
def __getslice__(self, i, j): # pylint: disable=getslice-method
return self.__getitem__(slice(i, j))
def __iter__(self):
i = 0
while 1:
try:
yield self[i]
i += 1
except dns.exception.FormError:
raise StopIteration
def unwrap(self):
return binary_type(self)
def maybe_wrap(wire):
if isinstance(wire, WireData):
return wire
elif isinstance(wire, binary_type):
return WireData(wire)
elif isinstance(wire, string_types):
return WireData(wire.encode())
raise ValueError("unhandled type %s" % type(wire))
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