Refactor all thread stuff into its own file

Source/Integration/TriggeredTask.h

@@ -0,0 +1,104 @@
+
+#include "CoreMinimal.h"
+
+///////////////////////////////////////////////
+//
+// TRIGGERED TASKS
+//
+// This is the situation where this class is
+// useful:
+// 
+// * You have a function to run in the background.
+// * It should start the instant a foreground thread says "NOW".
+// * It should be run exactly once for each "NOW".
+//
+// To use this class, construct an FTriggeredTask,
+// and provide a runnable object.  The runnable
+// object's "Run" method will get executed in
+// each time you call 'Trigger' on the FTriggeredTask.
+//
+// The run method will never get called reentrantly,
+// even if you call 'Trigger' rapidly in succession.
+//
+///////////////////////////////////////////////
+
+class FTriggeredTask : public FRunnable
+{
+private:
+	// Mutex used by control routines.
+	//
+	FCriticalSection Mutex;
+
+	// The worker thread.
+	//
+	FRunnableThread* Thread;
+
+	// Used to tell the worker thread to stop.
+	//
+	bool ThreadStopRequested;
+
+	// This event is used to wake up the thread.
+	//
+	// Normally, this means we want the worker to run the task
+	// once. But if ThreadStopRequested is true, it means we
+	// want the thread to exit.
+	//
+	FEvent* ThreadEvent;
+
+	// The client whose task we're triggering.
+	//
+	FRunnable* Client;
+
+private:
+	/////////////////////////////////////////////
+	// 
+	// This section contains routines that are
+	// executed by the thread itself.
+	//
+	/////////////////////////////////////////////
+
+	// Method of FRunnable, called by the Luprex thread.
+	//
+	virtual uint32 Run() override;
+
+public:
+	/////////////////////////////////////////////
+	//
+	// This section contains thread control routines.
+	// These are not invoked by the thread, but by the
+	// outside entity that started the thread.
+	//
+	/////////////////////////////////////////////
+
+	// Constructor.
+	//
+	// The client must outlive the FTriggeredTask.
+	//
+	FTriggeredTask();
+	
+	// Startup.
+	//
+	// Bring the system online, put it in ready mode.
+	//
+	void Startup(FRunnable* client);
+
+	// Shutdown.
+	//
+	// Bring the system down, deallocate all threads.
+	//
+	void Shutdown();
+
+	// Trigger
+	//
+	// Run the client's 'RUN' method once, in the
+	// background.  Trigger is a no-op if the system
+	// is shut down.  If you trigger when the task
+	// is already running, a trigger may get dropped.
+	//
+	void Trigger();
+
+	// IsRunning
+	//
+	bool IsRunning();
+};
+