"""The error checking chain is a list of status word (sw1, sw2) error check strategies.
__author__ = "http://www.gemalto.com"
Copyright 2001-2010 gemalto
Author: Jean-Daniel Aussel, mailto:jean-daniel.aussel@gemalto.com
This file is part of pyscard.
pyscard is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
pyscard is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with pyscard; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
"""
from sys import exc_info
class ErrorCheckingChain:
"""The error checking chain is a list of response apdu status word (sw1, sw2)
error check strategies. Each strategy in the chain is called until an error is
detected. A smartcard.sw.SWException exception is raised when an error is
detected. No exception is raised if no error is detected.
Implementation derived from Bruce Eckel, Thinking in Python. The ErrorCheckingChain
implements the Chain Of Responsibility design pattern.
"""
def __init__( self, chain, strategy ):
"""constructor. Appends a strategy to the ErrorCheckingChain chain."""
self.strategy = strategy
self.chain = chain
self.chain.append(self)
self.excludes=[]
def next( self ):
"""Returns next error checking strategy."""
# Where this link is in the chain:
location = self.chain.index(self)
if not self.end():
return self.chain[location + 1]
def addFilterException( self, exClass ):
"""Add an exception filter to the error checking chain.
exClass: the exception to exclude, e.g. smartcard.sw.SWExceptions.WarningProcessingException
A filtered exception will not be raised when the sw1,sw2 conditions that would raise
the excption are met.
"""
self.excludes.append( exClass )
if self.end():
return
self.next().addFilterException( exClass )
def end( self ):
"""Returns True if this is the end of the error checking strategy chain."""
return (self.chain.index(self) + 1 >= len(self.chain))
def __call__( self, data, sw1, sw2 ):
"""Called to test data, sw1 and sw2 for error on the chain."""
try:
self.strategy( data, sw1, sw2 )
except:
# if exception is filtered, return
for exception in self.excludes:
if exception==exc_info()[0]:
return
# otherwise reraise exception
raise
# if not done, call next strategy
if self.end():
return
return self.next()( data, sw1, sw2 )
|