Pathfinding.ThreadControlQueue.Pop C# (CSharp) Method

		public Path Pop () {
			
			Monitor.Enter(lockObj);
			try {
				if (terminate) {
					blockedReceivers++;
					throw new QueueTerminationException();
				}
				
				if (head == null) {
					Starving ();
				}
				
				while (blocked || starving) {
					blockedReceivers++;
					
					if (terminate) throw new QueueTerminationException();
					
					if (blockedReceivers == numReceivers) {
						//Last alive
						
					} else if (blockedReceivers > numReceivers) {
						throw new System.InvalidOperationException ("More receivers are blocked than specified in constructor ("+blockedReceivers + " > " + numReceivers+")");
					}
					
					Monitor.Exit (lockObj);
					block.WaitOne();
					Monitor.Enter (lockObj);
					blockedReceivers--;
					
					if (head == null) {
						Starving ();
					}
				}
				Path p = head;
				
				if (head.next == null) {
					tail = null;
				}
				head = head.next;
				return p;
			} finally {
				Monitor.Exit(lockObj);
			}
		}
		

        /// <summary>
        /// Main pathfinding method (multithreaded).
        /// This method will calculate the paths in the pathfinding queue when multithreading is enabled.
        ///
        /// See: CalculatePaths
        /// See: StartPath
        /// </summary>
        void CalculatePathsThreaded(PathHandler pathHandler)
        {
#if UNITY_2017_3_OR_NEWER
            UnityEngine.Profiling.Profiler.BeginThreadProfiling("Pathfinding", "Pathfinding thread #" + (pathHandler.threadID + 1));
#endif

#if !ASTAR_FAST_BUT_NO_EXCEPTIONS
            try {
#endif

            // Max number of ticks we are allowed to continue working in one run.
            // One tick is 1/10000 of a millisecond.
            // We need to check once in a while if the thread should be stopped.
            long maxTicks   = (long)(10 * 10000);
            long targetTick = System.DateTime.UtcNow.Ticks + maxTicks;
            while (true)
            {
                // The path we are currently calculating
                Path path = queue.Pop();
#if UNITY_2017_3_OR_NEWER
                profilingSampler.Begin();
#endif
                // Access the internal implementation methods
                IPathInternals ipath = (IPathInternals)path;


                AstarProfiler.StartFastProfile(0);
                ipath.PrepareBase(pathHandler);

                // Now processing the path
                // Will advance to Processing
                ipath.AdvanceState(PathState.Processing);

                // Call some callbacks
                if (OnPathPreSearch != null)
                {
                    OnPathPreSearch(path);
                }

                // Tick for when the path started, used for calculating how long time the calculation took
                long startTicks = System.DateTime.UtcNow.Ticks;

                // Prepare the path
                ipath.Prepare();

                AstarProfiler.EndFastProfile(0);

                if (path.CompleteState == PathCompleteState.NotCalculated)
                {
                    // For visualization purposes, we set the last computed path to p, so we can view debug info on it in the editor (scene view).
                    astar.debugPathData = ipath.PathHandler;
                    astar.debugPathID   = path.pathID;

                    AstarProfiler.StartFastProfile(1);

                    // Initialize the path, now ready to begin search
                    ipath.Initialize();

                    AstarProfiler.EndFastProfile(1);

                    // Loop while the path has not been fully calculated
                    while (path.CompleteState == PathCompleteState.NotCalculated)
                    {
                        // Do some work on the path calculation.
                        // The function will return when it has taken too much time
                        // or when it has finished calculation
                        AstarProfiler.StartFastProfile(2);
                        ipath.CalculateStep(targetTick);
                        AstarProfiler.EndFastProfile(2);

                        targetTick = System.DateTime.UtcNow.Ticks + maxTicks;

                        // Cancel function (and thus the thread) if no more paths should be accepted.
                        // This is done when the A* object is about to be destroyed
                        // The path is returned and then this function will be terminated
                        if (queue.IsTerminating)
                        {
                            path.FailWithError("AstarPath object destroyed");
                        }
                    }

                    path.duration = (System.DateTime.UtcNow.Ticks - startTicks) * 0.0001F;

#if ProfileAstar
                    System.Threading.Interlocked.Increment(ref AstarPath.PathsCompleted);
                    System.Threading.Interlocked.Add(ref AstarPath.TotalSearchTime, System.DateTime.UtcNow.Ticks - startTicks);
#endif
                }

                // Cleans up node tagging and other things
                ipath.Cleanup();

                AstarProfiler.StartFastProfile(9);

                if (path.immediateCallback != null)
                {
                    path.immediateCallback(path);
                }

                if (OnPathPostSearch != null)
                {
                    OnPathPostSearch(path);
                }

                // Push the path onto the return stack
                // It will be detected by the main Unity thread and returned as fast as possible (the next late update hopefully)
                returnQueue.Enqueue(path);

                // Will advance to ReturnQueue
                ipath.AdvanceState(PathState.ReturnQueue);

                AstarProfiler.EndFastProfile(9);
#if UNITY_2017_3_OR_NEWER
                profilingSampler.End();
#endif
            }
#if !ASTAR_FAST_BUT_NO_EXCEPTIONS
        }

        catch (System.Exception e) {
#if !NETFX_CORE
            if (e is ThreadAbortException || e is ThreadControlQueue.QueueTerminationException)
#else
            if (e is ThreadControlQueue.QueueTerminationException)
#endif
            {
                if (astar.logPathResults == PathLog.Heavy)
                {
                    Debug.LogWarning("Shutting down pathfinding thread #" + pathHandler.threadID);
                }
                return;
            }
            Debug.LogException(e);
            Debug.LogError("Unhandled exception during pathfinding. Terminating.");
            // Unhandled exception, kill pathfinding
            queue.TerminateReceivers();
        } finally {
#if UNITY_2017_3_OR_NEWER
            UnityEngine.Profiling.Profiler.EndThreadProfiling();
#endif
        }
#endif

            Debug.LogError("Error : This part should never be reached.");
            queue.ReceiverTerminated();
        }