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src/pypdevs/realtime/threadingBackend.py

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+# Copyright 2014 Modelling, Simulation and Design Lab (MSDL) at 
+# McGill University and the University of Antwerp (http://msdl.cs.mcgill.ca/)
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import threading
+
+class ThreadingBackend(object):
+    """
+    Wrapper around the actual threading backend. It will also handle interrupts and the passing of them to the calling thread.
+    """
+    def __init__(self, subsystem, args):
+        """
+        Constructor
+
+        :param subsystem: string specifying the subsystem to use: python, tkinter or loop
+        :param args: all additional arguments that should be passed to the subsystem's constructor (must be a list)
+        """
+        self.interrupted_value = None
+        self.value_lock = threading.Lock()
+        if subsystem == "python":
+            from pypdevs.realtime.threadingPython import ThreadingPython
+            self.subsystem = ThreadingPython(*args)
+        elif subsystem == "tkinter":
+            from pypdevs.realtime.threadingTkInter import ThreadingTkInter
+            self.subsystem = ThreadingTkInter(*args)
+        elif subsystem == "loop":
+            from pypdevs.realtime.threadingGameLoop import ThreadingGameLoop
+            self.subsystem = ThreadingGameLoop(*args)
+        else:
+            raise Exception("Realtime subsystem not found: " + str(subsystem))
+
+    def wait(self, time, func):
+        """
+        A non-blocking call, which will call the *func* parameter after *time* seconds. It will use the provided backend to do this.
+
+        :param time: time to wait in seconds, a float is possible
+        :param func: the function to call after the time has passed
+        """
+        self.subsystem.wait(time, func)
+
+    def interrupt(self, value):
+        """
+        Interrupt a running wait call.
+
+        :param value: the value that interrupts
+        """
+        self.interrupted_value = value
+        self.subsystem.interrupt()
+
+    def setInterrupt(self, value):
+        """
+        Sets the value of the interrupt. This should not be used manually and is only required to prevent the asynchronous combo generator from making *interrrupt()* calls.
+        
+        :param value: value with which the interrupt variable should be set
+        """
+        with self.value_lock:
+            if self.interrupted_value is None:
+                self.interrupted_value = value
+                return True
+            else:
+                # The interrupt was already set, indicating a collision!
+                return False
+
+    def getInterrupt(self):
+        """
+        Return the value of the interrupt and clear it internally.
+
+        :returns: the interrupt
+        """
+        with self.value_lock:
+            val = self.interrupted_value
+            self.interrupted_value = None
+        return val
+
+    def step(self):
+        """
+        Perform a step in the backend; only supported for the game loop backend.
+        """
+        self.subsystem.step()