# 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
# 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(str):
def __getslice__(self, i, j):
return j
_unspecified_bound = _SliceUnspecifiedBound('')[1:]
class WireData(str):
# WireData is a string with stricter slicing
def __getitem__(self, key):
try:
return WireData(super(WireData, self).__getitem__(key))
except IndexError:
raise dns.exception.FormError
def __getslice__(self, i, j):
try:
if j == _unspecified_bound:
# handle the case where the right bound is unspecified
j = len(self)
if i < 0 or j < 0:
raise dns.exception.FormError
# If it's not an empty slice, access left and right bounds
# to make sure they're valid
if i != j:
super(WireData, self).__getitem__(i)
super(WireData, self).__getitem__(j - 1)
return WireData(super(WireData, self).__getslice__(i, j))
except IndexError:
raise dns.exception.FormError
def __iter__(self):
i = 0
while 1:
try:
yield self[i]
i += 1
except dns.exception.FormError:
raise StopIteration
def unwrap(self):
return str(self)
def maybe_wrap(wire):
if not isinstance(wire, WireData):
return WireData(wire)
else:
return wire