Initial import of svn+ssh:://svn.icir.org/bro/trunk/bro as of r7088

src/Continuation.h

@@ -0,0 +1,61 @@
+// $Id: Continuation.h 2698 2006-04-03 05:50:52Z vern $
+//
+// Helper class to implement continuation-like mechanisms for
+// suspending/resuming tasks for incremental operation.
+//
+// TODO: - Document how to use this.
+//       - Find some nice macro-based interface?
+
+#ifndef continuation_h
+#define continuation_h
+
+#include "List.h"
+
+class Continuation {
+public:
+	Continuation()	{ current_level = 0; suspend_level = -1; }
+
+	// Returns true if we're called for the first time.
+	bool NewInstance() const
+		{ return suspend_level < current_level; }
+
+	// Returns true if a function called by us has suspended itself.
+	bool ChildSuspended() const
+		{ return suspend_level > current_level;  }
+
+	// Returns true if we have suspended before and are now called again to
+	// resume our operation.
+	bool Resuming() const
+		{ return suspend_level == current_level; }
+
+	// To be called just before we suspend operation for the time being.
+	void Suspend()
+		{ suspend_level = current_level; }
+
+	// To be called right after we resumed operation.
+	void Resume()
+		{ suspend_level = -1; }
+
+	// If we call a function which may suspend itself, we need to
+	// enclose the call with calls to SaveContext() and RestoreContext().
+	void SaveContext()		{ ++current_level; }
+	void RestoreContext()		{ --current_level; }
+
+	// We can store some user state which can be retrieved later.
+	void SaveState(void* user_ptr)
+		{ states.replace(current_level, user_ptr); }
+
+	void* RestoreState() const
+		{ return states[current_level]; }
+
+private:
+	int current_level;
+	int suspend_level;
+
+	declare(PList, void);
+	typedef PList(void) voidp_list;
+
+	voidp_list states;
+};
+
+#endif