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://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 threading import Thread, Event, Lock
from time import sleep
import traceback

from smartcard.Observer import Observer
from smartcard.Observer import Observable

from smartcard.CardRequest import CardRequest
from smartcard.Exceptions import SmartcardException
from smartcard.scard import SCARD_E_NO_SERVICE

_START_ON_DEMAND_ = False


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

    def __init__(self):
        pass

    def update(self, observable, handlers):
        """Called upon smart card insertion / removal.

        @param observable:
        @param handlers:
          - addedcards: list of inserted smart cards causing notification
          - removedcards: list of removed smart cards causing notification
        """
        pass


class CardMonitor(object):
    """Class that monitors smart card insertion / removals.
    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 L{deleteObserver}, or your program will run forever...

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

    class __CardMonitorSingleton(Observable):
        """The real smart card 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 is None:
                    self.rmthread = CardMonitoringThread(self)
            else:
                observer.update(self, (self.rmthread.cards, []))

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

            We delete the L{CardMonitoringThread} reference when there
            are no more observers.
            """
            Observable.deleteObserver(self, observer)
            if _START_ON_DEMAND_:
                if self.countObservers() == 0:
                    if self.rmthread is not None:
                        self.rmthread.stop()
                        self.rmthread.join()
                        self.rmthread = None

        def __str__(self):
            return 'CardMonitor'

    # the singleton
    instance = None
    lock = Lock()

    def __init__(self):
        with CardMonitor.lock:
            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 L{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 SmartcardException as exc:
                    # FIXME Tighten the exceptions caught by this block
                    traceback.print_exc()
                    # Most likely raised during interpreter shutdown due
                    # to unclean exit which failed to remove all observers.
                    # To solve this, we set the stop event and pass the
                    # exception to let the thread finish gracefully.
                    if exc.hresult == SCARD_E_NO_SERVICE:
                        self.stopEvent.set()

        # 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 join(self, *args, **kwargs):
        if self.instance:
            self.instance.join(*args, **kwargs)
            CardMonitoringThread.instance = None

    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__":
    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, handlers):
            addedcards, removedcards = handlers
            print("%d - added:   %s" % (self.obsindex, str(addedcards)))
            print("%d - removed: %s" % (self.obsindex, str(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()