cam: Add event loop

Add a simple event loop to the cam application and use it in the main()
function, with an example of how to handle SIGINT to gracefully stop the
loop.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/cam/event_loop.h

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * event_loop.h - cam - Event loop
+ */
+#ifndef __CAM_EVENT_LOOP_H__
+#define __CAM_EVENT_LOOP_H__
+
+#include <atomic>
+
+#include <libcamera/event_notifier.h>
+
+namespace libcamera {
+class EventDispatcher;
+};
+
+class EventLoop
+{
+public:
+	EventLoop(libcamera::EventDispatcher *dispatcher);
+	~EventLoop();
+
+	int exec();
+	void exit(int code = 0);
+
+private:
+	libcamera::EventDispatcher *dispatcher_;
+
+	std::atomic<bool> exit_;
+	int exitCode_;
+};
+
+#endif /* __CAM_EVENT_LOOP_H__ */