lib/dnspython/dns/wiredata.py

   1 # Copyright (C) 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
   6 # appear in all copies.
   7 #
   8 # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
   9 # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  11 # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  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 Wire Data Helper"""
  17
  18 import sys
  19
  20 import dns.exception
  21
  22 class WireData(str):
  23     # WireData is a string with stricter slicing
  24     def __getitem__(self, key):
  25         try:
  26             return WireData(super(WireData, self).__getitem__(key))
  27         except IndexError:
  28             raise dns.exception.FormError
  29     def __getslice__(self, i, j):
  30         try:
  31             if j == sys.maxint:
  32                 # handle the case where the right bound is unspecified
  33                 j = len(self)
  34             if i < 0 or j < 0:
  35                 raise dns.exception.FormError
  36             # If it's not an empty slice, access left and right bounds
  37             # to make sure they're valid
  38             if i != j:
  39                 super(WireData, self).__getitem__(i)
  40                 super(WireData, self).__getitem__(j - 1)
  41             return WireData(super(WireData, self).__getslice__(i, j))
  42         except IndexError:
  43             raise dns.exception.FormError
  44     def __iter__(self):
  45         i = 0
  46         while 1:
  47             try:
  48                 yield self[i]
  49                 i += 1
  50             except dns.exception.FormError:
  51                 raise StopIteration
  52     def unwrap(self):
  53         return str(self)
  54
  55 def maybe_wrap(wire):
  56     if not isinstance(wire, WireData):
  57         return WireData(wire)
  58     else:
  59         return wire