Fix Windows 10 SCARD_E_SERVICE_STOPPED from SCardListReaders()

On Windows 10 the PC/SC manager is stopped when
the latest reader is unplugged.

#75
#27
#74

smartcard/Exceptions.py

@@ -70,6 +70,11 @@ class CardServiceException(SmartcardException):
     pass
 
 
+class CardServiceStoppedException(SmartcardException):
+    """Raised when the CardService was stopped"""
+    pass
+
+
 class InvalidATRMaskLengthException(SmartcardException):
     """Raised when an ATR mask does not match an ATR length."""
 

smartcard/pcsc/PCSCContext.py

@@ -42,6 +42,9 @@ def __init__(self):
         def getContext(self):
             return self.hcontext
 
+        def releaseContext(self):
+            return SCardReleaseContext(self.hcontext)
+
     # the singleton
     mutex = RLock()
     instance = None
@@ -50,10 +53,23 @@ def __init__(self):
         PCSCContext.mutex.acquire()
         try:
             if not PCSCContext.instance:
-                PCSCContext.instance = PCSCContext.__PCSCContextSingleton()
+                self.renewContext()
         finally:
             PCSCContext.mutex.release()
 
     def __getattr__(self, name):
         if self.instance:
             return getattr(self.instance, name)
+
+    def renewContext():
+        PCSCContext.mutex.acquire()
+        try:
+            if PCSCContext.instance is not None:
+                PCSCContext.instance.releaseContext()
+
+            PCSCContext.instance = PCSCContext.__PCSCContextSingleton()
+        finally:
+            PCSCContext.mutex.release()
+
+        return PCSCContext.instance.getContext()
+    renewContext = staticmethod(renewContext)

smartcard/pcsc/PCSCReader.py

@@ -45,6 +45,8 @@ def __PCSCreaders__(hcontext, groups=[]):
     if hresult != 0:
         if hresult == SCARD_E_NO_READERS_AVAILABLE:
             readers = []
+        elif hresult == SCARD_E_SERVICE_STOPPED:
+            raise CardServiceStoppedException()
         else:
             raise ListReadersException(hresult)
 
@@ -107,7 +109,13 @@ def readers(groups=[]):
         creaders = []
         hcontext = PCSCContext().getContext()
 
-        for reader in __PCSCreaders__(hcontext, groups):
+        try:
+            pcsc_readers = __PCSCreaders__(hcontext, groups)
+        except CardServiceStoppedException:
+            hcontext = PCSCContext.renewContext()
+            pcsc_readers = __PCSCreaders__(hcontext, groups)
+
+        for reader in pcsc_readers:
             creaders.append(PCSCReader.Factory.create(reader))
         return creaders
     readers = staticmethod(readers)