- added ev3

git-svn-id: http://moon:8086/svn/software/trunk/projects/opencv@329 b431acfa-c32f-4a4a-93f1-934dc6c82436

ev3/async.py

@@ -0,0 +1,91 @@
+"""A simple thread subclass for making ev3 function calls asynchronous.
+
+EXAMPLE USAGE:
+    import time
+
+    from ev3 import *
+
+
+    finished = False
+
+
+    def keep_alive_finished(result):
+        global finished
+        print 'The keep_alive() function returned: ', result
+        finished = True
+
+
+    if ("__main__" == __name__):
+        try:
+            async_thread = async.AsyncThread()
+
+            with ev3.EV3() as brick:
+                async_thread.put(brick.keep_alive, keep_alive_finished)
+
+                while (not finished):
+                    print 'Waiting...'
+                    time.sleep(0.1)
+
+        except ev3.EV3Error as ex:
+            print 'An error occurred: ', ex
+
+        async_thread.stop()
+
+"""
+
+
+import threading
+import queue
+
+
+class AsyncThread(threading.Thread):
+    """A simple thread subclass maintains a queue of functions to call."""
+
+
+    _STOP_QUEUE_ITEM = 'STOP'
+
+
+    def __init__(self):
+        """Creates and starts a new thread."""
+        super(AsyncThread, self).__init__()
+
+        self._daemon = True
+        self._queue = Queue.Queue()
+
+        self.start()
+
+
+    def run(self):
+        """This function is called automatically by the Thread class."""
+        try:
+            while(True):
+                item = self._queue.get(block=True)
+
+                if (self._STOP_QUEUE_ITEM == item):
+                    break
+
+                ev3_func, cb, args, kwargs = item
+
+                cb(ev3_func(*args, **kwargs))
+
+        except KeyboardInterrupt:
+            pass
+
+
+    def stop(self):
+        """Instructs the thread to exit after the current function is
+        finished.
+
+        """
+        with self._queue.mutex:
+            self._queue.queue.clear()
+
+        self._queue.put(self._STOP_QUEUE_ITEM)
+
+
+    def put(self, ev3_func, cb, *args, **kwargs):
+        """Adds a new function to the queue. The cb (callback) parameter should
+        be a function that accepts the result as its only parameter.
+
+        """
+        self._queue.put((ev3_func, cb, args, kwargs))