Home	Trees	Indices	Help	pyscard

Source Code for Module smartcard.sw.ErrorCheckingChain

 1  """The error checking chain is a list of status word (sw1, sw2) error check strategies. 
 2   
 3  __author__ = "http://www.gemalto.com" 
 4   
 5  Copyright 2001-2011 gemalto 
 6  Author: Jean-Daniel Aussel, mailto:jean-daniel.aussel@gemalto.com 
 7   
 8  This file is part of pyscard. 
 9   
10  pyscard is free software; you can redistribute it and/or modify 
11  it under the terms of the GNU Lesser General Public License as published by 
12  the Free Software Foundation; either version 2.1 of the License, or 
13  (at your option) any later version. 
14   
15  pyscard is distributed in the hope that it will be useful, 
16  but WITHOUT ANY WARRANTY; without even the implied warranty of 
17  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
18  GNU Lesser General Public License for more details. 
19   
20  You should have received a copy of the GNU Lesser General Public License 
21  along with pyscard; if not, write to the Free Software 
22  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA 
23  """ 
24   
25  from sys import exc_info 
26   
27   
28 -class ErrorCheckingChain: 
29      """The error checking chain is a list of response apdu status word 
30      (sw1, sw2) error check strategies. Each strategy in the chain is 
31      called until an error is detected. A L{smartcard.sw.SWException} 
32      exception is raised when an error is detected. No exception is 
33      raised if no error is detected. 
34   
35      Implementation derived from Bruce Eckel, Thinking in Python. The 
36      L{ErrorCheckingChain} implements the Chain Of Responsibility design 
37      pattern. 
38      """ 
39   
40 -    def __init__(self, chain, strategy): 
41          """constructor. Appends a strategy to the L{ErrorCheckingChain} 
42          chain.""" 
43          self.strategy = strategy 
44          self.chain = chain 
45          self.chain.append(self) 
46          self.excludes = [] 
47   
48 -    def next(self): 
49          """Returns next error checking strategy.""" 
50          # Where this link is in the chain: 
51          location = self.chain.index(self) 
52          if not self.end(): 
53              return self.chain[location + 1] 
54   
55 -    def addFilterException(self, exClass): 
56          """Add an exception filter to the error checking chain. 
57   
58          @param exClass:    the exception to exclude, e.g. 
59          L{smartcard.sw.SWExceptions.WarningProcessingException} A filtered 
60          exception will not be raised when the sw1,sw2 conditions that 
61          would raise the excption are met. 
62          """ 
63   
64          self.excludes.append(exClass) 
65          if self.end(): 
66              return 
67          self.next().addFilterException(exClass) 
68   
69 -    def end(self): 
70          """Returns True if this is the end of the error checking 
71          strategy chain.""" 
72          return (self.chain.index(self) + 1 >= len(self.chain)) 
73   
74 -    def __call__(self, data, sw1, sw2): 
75          """Called to test data, sw1 and sw2 for error on the chain.""" 
76          try: 
77              self.strategy(data, sw1, sw2) 
78          except: 
79              # if exception is filtered, return 
80              for exception in self.excludes: 
81                  if exception == exc_info()[0]: 
82                      return 
83              # otherwise reraise exception 
84              raise 
85   
86          # if not done, call next strategy 
87          if self.end(): 
88              return 
89          return self.next()(data, sw1, sw2) 
90   

Home	Trees	Indices	Help	pyscard