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143 lines
5.1 KiB
143 lines
5.1 KiB
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
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# Copyright (C) 2003-2017 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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"""Common DNS Exceptions.
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Dnspython modules may also define their own exceptions, which will
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always be subclasses of ``DNSException``.
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"""
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class DNSException(Exception):
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"""Abstract base class shared by all dnspython exceptions.
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It supports two basic modes of operation:
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a) Old/compatible mode is used if ``__init__`` was called with
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empty *kwargs*. In compatible mode all *args* are passed
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to the standard Python Exception class as before and all *args* are
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printed by the standard ``__str__`` implementation. Class variable
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``msg`` (or doc string if ``msg`` is ``None``) is returned from ``str()``
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if *args* is empty.
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b) New/parametrized mode is used if ``__init__`` was called with
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non-empty *kwargs*.
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In the new mode *args* must be empty and all kwargs must match
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those set in class variable ``supp_kwargs``. All kwargs are stored inside
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``self.kwargs`` and used in a new ``__str__`` implementation to construct
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a formatted message based on the ``fmt`` class variable, a ``string``.
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In the simplest case it is enough to override the ``supp_kwargs``
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and ``fmt`` class variables to get nice parametrized messages.
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"""
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msg = None # non-parametrized message
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supp_kwargs = set() # accepted parameters for _fmt_kwargs (sanity check)
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fmt = None # message parametrized with results from _fmt_kwargs
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def __init__(self, *args, **kwargs):
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self._check_params(*args, **kwargs)
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if kwargs:
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self.kwargs = self._check_kwargs(**kwargs)
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self.msg = str(self)
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else:
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self.kwargs = dict() # defined but empty for old mode exceptions
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if self.msg is None:
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# doc string is better implicit message than empty string
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self.msg = self.__doc__
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if args:
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super().__init__(*args)
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else:
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super().__init__(self.msg)
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def _check_params(self, *args, **kwargs):
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"""Old exceptions supported only args and not kwargs.
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For sanity we do not allow to mix old and new behavior."""
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if args or kwargs:
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assert bool(args) != bool(kwargs), \
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'keyword arguments are mutually exclusive with positional args'
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def _check_kwargs(self, **kwargs):
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if kwargs:
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assert set(kwargs.keys()) == self.supp_kwargs, \
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'following set of keyword args is required: %s' % (
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self.supp_kwargs)
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return kwargs
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def _fmt_kwargs(self, **kwargs):
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"""Format kwargs before printing them.
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Resulting dictionary has to have keys necessary for str.format call
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on fmt class variable.
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"""
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fmtargs = {}
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for kw, data in kwargs.items():
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if isinstance(data, (list, set)):
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# convert list of <someobj> to list of str(<someobj>)
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fmtargs[kw] = list(map(str, data))
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if len(fmtargs[kw]) == 1:
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# remove list brackets [] from single-item lists
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fmtargs[kw] = fmtargs[kw].pop()
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else:
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fmtargs[kw] = data
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return fmtargs
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def __str__(self):
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if self.kwargs and self.fmt:
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# provide custom message constructed from keyword arguments
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fmtargs = self._fmt_kwargs(**self.kwargs)
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return self.fmt.format(**fmtargs)
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else:
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# print *args directly in the same way as old DNSException
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return super().__str__()
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class FormError(DNSException):
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"""DNS message is malformed."""
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class SyntaxError(DNSException):
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"""Text input is malformed."""
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class UnexpectedEnd(SyntaxError):
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"""Text input ended unexpectedly."""
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class TooBig(DNSException):
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"""The DNS message is too big."""
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class Timeout(DNSException):
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"""The DNS operation timed out."""
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supp_kwargs = {'timeout'}
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fmt = "The DNS operation timed out after {timeout} seconds"
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class ExceptionWrapper:
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def __init__(self, exception_class):
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self.exception_class = exception_class
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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if exc_type is not None and not isinstance(exc_val,
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self.exception_class):
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raise self.exception_class(str(exc_val)) from exc_val
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return False
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