Removing some more allocations in signalling

Author: pzgulyas

Source/Orts.Simulation/Simulation/Signalling/SignalObject.cs

@@ -140,6 +140,7 @@ public enum Permission
 
         private readonly List<int> SectionsWithAlternativePath = new List<int>();
         private readonly List<int> SectionsWithAltPathSet = new List<int>();
+        private readonly static List<int> sectionsInRoute = new List<int>();
 
         public bool enabled
         {
@@ -2157,7 +2158,7 @@ public bool requestClearSignal(Train.TCSubpathRoute RoutePart, Train.TrainRouted
             // copy sections upto next normal signal
             // check for loop
 
-            List<int> sectionsInRoute = new List<int>();
+            sectionsInRoute.Clear();
 
             for (int iNode = foundFirstSection; iNode < RoutePart.Count && foundLastSection < 0; iNode++)
             {

Source/Orts.Simulation/Simulation/Signalling/TrackCircuitState.cs

@@ -36,6 +36,8 @@ public class TrackCircuitState
         public int RemoteReserved;                                 // remote reserved (number only) //
         public bool Forced;                                        // forced by human dispatcher    //
 
+        List<Train.TrainRouted> TrainOccupyList;                   // used for allocation-free returning of the TrainOccuping() result //
+
         public TrackCircuitState()
         {
             TrainOccupy = new TrainOccupyState();
@@ -253,12 +255,13 @@ public void Save(BinaryWriter outf)
         /// </summary>
         public List<Train.TrainRouted> TrainsOccupying()
         {
-            List<Train.TrainRouted> reqList = new List<Train.TrainRouted>();
+            TrainOccupyList = TrainOccupyList ?? new List<Train.TrainRouted>();
+            TrainOccupyList.Clear();
             foreach (KeyValuePair<Train.TrainRouted, int> thisTCT in TrainOccupy)
             {
-                reqList.Add(thisTCT.Key);
+                TrainOccupyList.Add(thisTCT.Key);
             }
-            return (reqList);
+            return (TrainOccupyList);
         }
 
         /// <summary>
@@ -267,15 +270,16 @@ public void Save(BinaryWriter outf)
         /// </summary>
         public List<Train.TrainRouted> TrainsOccupying(int reqDirection)
         {
-            List<Train.TrainRouted> reqList = new List<Train.TrainRouted>();
+            TrainOccupyList = TrainOccupyList ?? new List<Train.TrainRouted>();
+            TrainOccupyList.Clear();
             foreach (KeyValuePair<Train.TrainRouted, int> thisTCT in TrainOccupy)
             {
                 if (thisTCT.Value == reqDirection)
                 {
-                    reqList.Add(thisTCT.Key);
+                    TrainOccupyList.Add(thisTCT.Key);
                 }
             }
-            return (reqList);
+            return (TrainOccupyList);
         }
 
         /// <summary>