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# Copyright (C) 2003-2007, 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.
"""Common DNS Exceptions."""
class DNSException(Exception):
"""Abstract base class shared by all dnspython exceptions.
It supports two basic modes of operation:
a) Old/compatible mode is used if __init__ was called with
empty **kwargs.
In compatible mode all *args are passed to standard Python Exception class
as before and all *args are printed by standard __str__ implementation.
Class variable msg (or doc string if msg is None) is returned from str()
if *args is empty.
b) New/parametrized mode is used if __init__ was called with
non-empty **kwargs.
In the new mode *args has to be empty and all kwargs has to exactly match
set in class variable self.supp_kwargs. All kwargs are stored inside
self.kwargs and used in new __str__ implementation to construct
formatted message based on self.fmt string.
In the simplest case it is enough to override supp_kwargs and fmt
class variables to get nice parametrized messages.
"""
msg = None # non-parametrized message
supp_kwargs = set() # accepted parameters for _fmt_kwargs (sanity check)
fmt = None # message parametrized with results from _fmt_kwargs
def __init__(self, *args, **kwargs):
self._check_params(*args, **kwargs)
if kwargs:
self.kwargs = self._check_kwargs(**kwargs)
self.msg = str(self)
else:
self.kwargs = dict() # defined but empty for old mode exceptions
if self.msg is None:
# doc string is better implicit message than empty string
self.msg = self.__doc__
if args:
super(DNSException, self).__init__(*args)
else:
super(DNSException, self).__init__(self.msg)
def _check_params(self, *args, **kwargs):
"""Old exceptions supported only args and not kwargs.
For sanity we do not allow to mix old and new behavior."""
if args or kwargs:
assert bool(args) != bool(kwargs), \
'keyword arguments are mutually exclusive with positional args'
def _check_kwargs(self, **kwargs):
if kwargs:
assert set(kwargs.keys()) == self.supp_kwargs, \
'following set of keyword args is required: %s' % (
self.supp_kwargs)
return kwargs
def _fmt_kwargs(self, **kwargs):
"""Format kwargs before printing them.
Resulting dictionary has to have keys necessary for str.format call
on fmt class variable.
"""
fmtargs = {}
for kw, data in kwargs.items():
if isinstance(data, (list, set)):
# convert list of <someobj> to list of str(<someobj>)
fmtargs[kw] = list(map(str, data))
if len(fmtargs[kw]) == 1:
# remove list brackets [] from single-item lists
fmtargs[kw] = fmtargs[kw].pop()
else:
fmtargs[kw] = data
return fmtargs
def __str__(self):
if self.kwargs and self.fmt:
# provide custom message constructed from keyword arguments
fmtargs = self._fmt_kwargs(**self.kwargs)
return self.fmt.format(**fmtargs)
else:
# print *args directly in the same way as old DNSException
return super(DNSException, self).__str__()
class FormError(DNSException):
"""DNS message is malformed."""
class SyntaxError(DNSException):
"""Text input is malformed."""
class UnexpectedEnd(SyntaxError):
"""Text input ended unexpectedly."""
class TooBig(DNSException):
"""The DNS message is too big."""
class Timeout(DNSException):
"""The DNS operation timed out."""
supp_kwargs = set(['timeout'])
fmt = "The DNS operation timed out after {timeout} seconds"
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