Move generic fs helpers to os/include/file_system

Fixes #1488

repos/os/include/file_system/node.h

@@ -0,0 +1,77 @@
+/*
+ * \brief  File-system node
+ * \author Norman Feske
+ * \date   2012-04-11
+ */
+
+#ifndef _FILE_SYSTEM__NODE_H_
+#define _FILE_SYSTEM__NODE_H_
+
+/* Genode includes */
+#include <file_system/listener.h>
+#include <util/list.h>
+#include <base/lock.h>
+
+
+namespace File_system {
+
+	class Node_base
+	{
+		private:
+
+			Lock           _lock;
+			List<Listener> _listeners;
+
+		public:
+
+			virtual ~Node_base()
+			{
+				/* propagate event to listeners */
+				mark_as_updated();
+				notify_listeners();
+
+				while (_listeners.first())
+					_listeners.remove(_listeners.first());
+			}
+
+			void lock()   { _lock.lock(); }
+			void unlock() { _lock.unlock(); }
+
+			void add_listener(Listener *listener)
+			{
+				_listeners.insert(listener);
+			}
+
+			void remove_listener(Listener *listener)
+			{
+				_listeners.remove(listener);
+			}
+
+			void notify_listeners()
+			{
+				for (Listener *curr = _listeners.first(); curr; curr = curr->next())
+					curr->notify();
+			}
+
+			void mark_as_updated()
+			{
+				for (Listener *curr = _listeners.first(); curr; curr = curr->next())
+					curr->mark_as_updated();
+			}
+	};
+
+
+	/**
+	 * Guard used for properly releasing node locks
+	 */
+	struct Node_lock_guard
+	{
+		Node_base *node;
+
+		Node_lock_guard(Node_base *node) : node(node) { node = node; }
+
+		~Node_lock_guard() { node->unlock(); }
+	};
+}
+
+#endif /* _FILE_SYSTEM__NODE_H_ */