CardMonitoring.py

"""Smart card insertion/removal monitoring classes.

CardObserver is a base class for objects that are to be notified
upon smart card insertion/removal.

CardMonitor is a singleton object notifying registered CardObservers
upon reader insertion/removal.

__author__ = "http:https://www.gemalto.com"

Copyright 2001-2012 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
from threading import Thread, Event
from time import sleep

from smartcard.System import readers
from smartcard.Exceptions import CardRequestTimeoutException
from smartcard.Observer import Observer
from smartcard.Observer import Observable

from smartcard.CardType import AnyCardType
from smartcard.CardRequest import CardRequest

_START_ON_DEMAND_ = False


# CardObserver interface
class CardObserver(Observer):
    """
    CardObserver is a base abstract class for objects that are to be notified
    upon smartcard reader insertion/removal.
    """

    def __init__(self):
        pass

    def update(self, observable, (addedcards, removedcards)):
        """Called upon reader insertion/removal.

        observable:
        addedcards: list of added readers causing notification
        removedcards: list of removed readers causing notification
        """
        pass


class CardMonitor(object):
    """Class that monitors smart card insertion/removal.
    and notify observers

    note: a card monitoring thread will be running
    as long as the card monitor has observers, or CardMonitor.stop()
    is called. Do not forget to delete all your observers by
    calling deleteObserver, or your program will run forever...

    Uses the singleton pattern from Thinking in Python
    Bruce Eckel, http:https://mindview.net/Books/TIPython to make sure
    there is only one CardMonitor.
    """

    class __CardMonitorSingleton(Observable):
        """The real smartcard monitor class.

        A single instance of this class is created
        by the public CardMonitor class.
        """

        def __init__(self):
            Observable.__init__(self)
            if _START_ON_DEMAND_:
                self.rmthread = None
            else:
                self.rmthread = CardMonitoringThread(self)

        def addObserver(self, observer):
            """Add an observer.

            We only start the card monitoring thread when
            there are observers.
            """
            Observable.addObserver(self, observer)
            if _START_ON_DEMAND_:
                if self.countObservers() > 0 and self.rmthread == None:
                    self.rmthread = CardMonitoringThread(self)
            else:
                observer.update(self, (self.rmthread.cards, []))

        def deleteObserver(self, observer):
            """Remove an observer.

            We delete the CardMonitoringThread reference when there
            are no more observers.
            """
            Observable.deleteObserver(self, observer)
            if _START_ON_DEMAND_:
                if self.countObservers() == 0:
                    if self.rmthread != None:
                        self.rmthread = None

        def __str__(self):
            return 'CardMonitor'

    # the singleton
    instance = None

    def __init__(self):
        if not CardMonitor.instance:
            CardMonitor.instance = CardMonitor.__CardMonitorSingleton()

    def __getattr__(self, name):
        return getattr(self.instance, name)


class CardMonitoringThread(object):
    """Card insertion thread.
    This thread waits for card insertion.
    """

    class __CardMonitoringThreadSingleton(Thread):
        """The real card monitoring thread class.

        A single instance of this class is created
        by the public CardMonitoringThread class.
        """

        def __init__(self, observable):
            Thread.__init__(self)
            self.observable = observable
            self.stopEvent = Event()
            self.stopEvent.clear()
            self.cards = []
            self.setDaemon(True)

        # the actual monitoring thread
        def run(self):
            """Runs until stopEvent is notified, and notify
            observers of all card insertion/removal.
            """
            self.cardrequest = CardRequest(timeout=0.1)
            while self.stopEvent.isSet() != 1:
                try:
                    currentcards = self.cardrequest.waitforcardevent()

                    addedcards = []
                    for card in currentcards:
                        if not self.cards.__contains__(card):
                            addedcards.append(card)

                    removedcards = []
                    for card in self.cards:
                        if not currentcards.__contains__(card):
                            removedcards.append(card)

                    if addedcards != [] or removedcards != []:
                        self.cards = currentcards
                        self.observable.setChanged()
                        self.observable.notifyObservers(
                            (addedcards, removedcards))

                # when CardMonitoringThread.__del__() is invoked in
                # response to shutdown, e.g., when execution of the
                # program is done, other globals referenced by the
                # __del__() method may already have been deleted.
                # this causes ReaderMonitoringThread.run() to except
                # with a TypeError or AttributeError
                except TypeError:
                    pass
                except AttributeError:
                    pass

                except:
                    try:
                        import sys
                        print sys.exc_info()[1]
                        print sys.exc_info()[2]
                        print sys.exc_info()[0]
                    except:
                        pass

        # stop the thread by signaling stopEvent
        def stop(self):
            self.stopEvent.set()

    # the singleton
    instance = None

    def __init__(self, observable):
        if not CardMonitoringThread.instance:
            CardMonitoringThread.instance = \
               CardMonitoringThread.__CardMonitoringThreadSingleton(observable)
            CardMonitoringThread.instance.start()

    def __getattr__(self, name):
        if self.instance:
            return getattr(self.instance, name)

    # commented to avoid bad clean-up sequence of python where __del__
    # is called when some objects it uses are already gargabe collected
    #def __del__(self):
    #    if CardMonitoringThread.instance!=None:
    #        CardMonitoringThread.instance.stop()
    #        CardMonitoringThread.instance = None


if __name__ == "__main__":
    from smartcard.CardMonitoring import CardMonitor
    print 'insert or remove cards in the next 10 seconds'

    # a simple card observer that prints added/removed cards
    class printobserver(CardObserver):

        def __init__(self, obsindex):
            self.obsindex = obsindex

        def update(self, observable, (addedcards, removedcards)):
            print "%d - added:   " % self.obsindex, addedcards
            print "%d - removed: " % self.obsindex, removedcards

    class testthread(Thread):

        def __init__(self, obsindex):
            Thread.__init__(self)
            self.readermonitor = CardMonitor()
            self.obsindex = obsindex
            self.observer = None

        def run(self):
            # create and register observer
            self.observer = printobserver(self.obsindex)
            self.readermonitor.addObserver(self.observer)
            sleep(10)
            self.readermonitor.deleteObserver(self.observer)

    t1 = testthread(1)
    t2 = testthread(2)
    t1.start()
    t2.start()