new .dispose() method to release resources in the backend classes

brother_ql/backends/generic.py

@@ -39,3 +39,15 @@ class BrotherQLBackendGeneric(object):
         except Exception as e:
             logger.debug('Error reading... %s', e)
             raise
+
+    def dispose(self):
+        try:
+            self._dispose()
+        except:
+            pass
+
+    def _dispose(self):
+        raise NotImplementedError()
+
+    def __del__(self):
+        self.dispose()

brother_ql/backends/linux_kernel.py

@@ -75,3 +75,6 @@ class BrotherQLBackendLinuxKernel(BrotherQLBackendGeneric):
                 return data
         else:
             raise NotImplementedError('Unknown strategy')
+
+    def _dispose(self):
+        os.close(self.dev)

brother_ql/backends/network.py

@@ -90,3 +90,7 @@ class BrotherQLBackendNetwork(BrotherQLBackendGeneric):
             return data
         else:
             raise NotImplementedError('Unknown strategy')
+
+    def _dispose(self):
+        self.s.shutdown(socket.SHUT_RDWR)
+        self.s.close()

brother_ql/backends/pyusb.py

@@ -88,6 +88,9 @@ class BrotherQLBackendPyUSB(BrotherQLBackendGeneric):
 
         if self.dev.is_kernel_driver_active(0):
             self.dev.detach_kernel_driver(0)
+            self.was_kernel_driver_active = True
+        else:
+            self.was_kernel_driver_active = False
 
         # set the active configuration. With no arguments, the first configuration will be the active one
         self.dev.set_configuration()
@@ -135,3 +138,10 @@ class BrotherQLBackendPyUSB(BrotherQLBackendGeneric):
                 return data
         else:
             raise NotImplementedError('Unknown strategy')
+
+    def _dispose(self):
+        usb.util.dispose_resources(self.dev)
+        del self.write_dev, self.read_dev
+        if self.was_kernel_driver_active:
+            self.dev.attach_kernel_driver(0)
+        del self.dev

brother_ql/web/__init__.py

@@ -149,6 +149,7 @@ def print_text(content=None):
         try:
             be = BACKEND_CLASS(BACKEND_STRING_DESCR)
             be.write(qlr.data)
+            be.dispose()
             del be
         except Exception as e:
             return_dict['message'] = str(e)