ISMAIL MASSERAN
97 lines
3.5 KiB
Python
97 lines
3.5 KiB
Python
"""The error checking chain is a list of status word
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(sw1, sw2) error check strategies.
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__author__ = "https://www.gemalto.com/"
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Copyright 2001-2012 gemalto
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Author: Jean-Daniel Aussel, mailto:jean-daniel.aussel@gemalto.com
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This file is part of pyscard.
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pyscard is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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pyscard is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with pyscard; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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"""
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from sys import exc_info
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class ErrorCheckingChain:
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"""The error checking chain is a list of response apdu status word
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(sw1, sw2) error check strategies. Each strategy in the chain is
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called until an error is detected. A L{smartcard.sw.SWExceptions}
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exception is raised when an error is detected. No exception is
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raised if no error is detected.
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Implementation derived from Bruce Eckel, Thinking in Python. The
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L{ErrorCheckingChain} implements the Chain Of Responsibility design
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pattern.
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"""
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def __init__(self, chain, strategy):
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"""constructor. Appends a strategy to the L{ErrorCheckingChain}
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chain."""
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self.strategy = strategy
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self.chain = chain
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self.chain.append(self)
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self.excludes = []
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def next(self):
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"""Returns next error checking strategy."""
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# Where this link is in the chain:
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location = self.chain.index(self)
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if not self.end():
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return self.chain[location + 1]
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return None
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def addFilterException(self, exClass):
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"""Add an exception filter to the error checking chain.
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@param exClass: the exception to exclude, e.g.
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L{smartcard.sw.SWExceptions.WarningProcessingException} A filtered
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exception will not be raised when the sw1,sw2 conditions that
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would raise the exception are met.
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"""
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self.excludes.append(exClass)
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if self.end():
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return
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self.next().addFilterException(exClass)
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def end(self):
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"""Returns True if this is the end of the error checking
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strategy chain."""
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return self.chain.index(self) + 1 >= len(self.chain)
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def __call__(self, data, sw1, sw2):
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"""Called to test data, sw1 and sw2 for error on the chain."""
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try:
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self.strategy(data, sw1, sw2)
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except tuple(self.excludes):
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# The following additional filter may look redundant, it isn't.
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# It checks that type(exc) is *equal* to any of self.excludes,
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# rather than equal-or-subclass to any of self.excludes.
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# This maintains backward compatibility with the behaviour of
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# pyscard <= 1.6.16.
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# if exception is filtered, return
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for exception in self.excludes:
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if exception == exc_info()[0]:
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return None
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# otherwise reraise exception
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raise
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# if not done, call next strategy
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if self.end():
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return None
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return self.next()(data, sw1, sw2)
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