From c6fcfefe4deedd0abae65c760003289e8560f2c0 Mon Sep 17 00:00:00 2001
From: Koen Bussemaker <koen_bussemaker@hotmail.com>
Date: Mon, 11 Mar 2024 20:29:23 +0100
Subject: [PATCH] Codechange: Make the road vehicle cache behave more like a
 std::deque

---
 src/pathfinder/yapf/yapf_road.cpp | 13 +++----------
 src/roadveh.h                     | 29 +++++++++++++++++++++++++++++
 src/roadveh_cmd.cpp               | 15 ++++++---------
 3 files changed, 38 insertions(+), 19 deletions(-)

diff --git a/src/pathfinder/yapf/yapf_road.cpp b/src/pathfinder/yapf/yapf_road.cpp
index 41102c2e15..7390404b42 100644
--- a/src/pathfinder/yapf/yapf_road.cpp
+++ b/src/pathfinder/yapf/yapf_road.cpp
@@ -393,8 +393,7 @@ public:
 			while (pNode->m_parent != nullptr) {
 				steps--;
 				if (pNode->GetIsChoice() && steps < YAPF_ROADVEH_PATH_CACHE_SEGMENTS) {
-					path_cache.td.push_front(pNode->GetTrackdir());
-					path_cache.tile.push_front(pNode->GetTile());
+					path_cache.push_front({ pNode->GetTile(), pNode->GetTrackdir() });
 				}
 				pNode = pNode->m_parent;
 			}
@@ -403,10 +402,7 @@ public:
 			assert(best_next_node.GetTile() == tile);
 			next_trackdir = best_next_node.GetTrackdir();
 			/* remove last element for the special case when tile == dest_tile */
-			if (path_found && !path_cache.empty() && tile == v->dest_tile) {
-				path_cache.td.pop_back();
-				path_cache.tile.pop_back();
-			}
+			if (path_found && !path_cache.empty() && tile == v->dest_tile) path_cache.pop_back();
 
 			/* Check if target is a station, and cached path ends within 8 tiles of the dest tile */
 			const Station *st = Yapf().GetDestinationStation();
@@ -417,10 +413,7 @@ public:
 					 * trim end of path cache within a number of tiles of road stop tile area */
 					TileArea non_cached_area = v->IsBus() ? st->bus_station : st->truck_station;
 					non_cached_area.Expand(YAPF_ROADVEH_PATH_CACHE_DESTINATION_LIMIT);
-					while (!path_cache.empty() && non_cached_area.Contains(path_cache.tile.back())) {
-						path_cache.td.pop_back();
-						path_cache.tile.pop_back();
-					}
+					while (!path_cache.empty() && non_cached_area.Contains(path_cache.back().tile)) path_cache.pop_back();
 				}
 			}
 		}
diff --git a/src/roadveh.h b/src/roadveh.h
index 19ba64d1d6..4c864b3329 100644
--- a/src/roadveh.h
+++ b/src/roadveh.h
@@ -82,9 +82,38 @@ void RoadVehUpdateCache(RoadVehicle *v, bool same_length = false);
 void GetRoadVehSpriteSize(EngineID engine, uint &width, uint &height, int &xoffs, int &yoffs, EngineImageType image_type);
 
 struct RoadVehPathCache {
+	friend class SlVehicleRoadVeh;
+private:
 	std::deque<Trackdir> td;
 	std::deque<TileIndex> tile;
 
+public:
+	struct Item {
+		TileIndex tile;
+		Trackdir trackdir;
+	};
+
+	Item front() { return {this->tile.front(), this->td.front()}; }
+	Item back() { return {this->tile.back(), this->td.back()}; }
+
+	inline void push_front(Item item)
+	{
+		this->tile.push_front(item.tile);
+		this->td.push_front(item.trackdir);
+	}
+
+	inline void pop_front()
+	{
+		this->td.pop_front();
+		this->tile.pop_front();
+	}
+
+	inline void pop_back()
+	{
+		this->td.pop_back();
+		this->tile.pop_back();
+	}
+
 	inline bool empty() const { return this->td.empty(); }
 
 	inline size_t size() const
diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
index 32150cc714..b775087caa 100644
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -963,7 +963,7 @@ static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection
 
 	/* Only one track to choose between? */
 	if (KillFirstBit(trackdirs) == TRACKDIR_BIT_NONE) {
-		if (!v->path.empty() && v->path.tile.front() == tile) {
+		if (!v->path.empty() && v->path.front().tile == tile) {
 			/* Vehicle expected a choice here, invalidate its path. */
 			v->path.clear();
 		}
@@ -972,15 +972,14 @@ static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection
 
 	/* Attempt to follow cached path. */
 	if (!v->path.empty()) {
-		if (v->path.tile.front() != tile) {
+		if (v->path.front().tile != tile) {
 			/* Vehicle didn't expect a choice here, invalidate its path. */
 			v->path.clear();
 		} else {
-			Trackdir trackdir = v->path.td.front();
+			Trackdir trackdir = v->path.front().trackdir;
 
 			if (HasBit(trackdirs, trackdir)) {
-				v->path.td.pop_front();
-				v->path.tile.pop_front();
+				v->path.pop_front();
 				return_track(trackdir);
 			}
 
@@ -1291,8 +1290,7 @@ again:
 			if (u != nullptr) {
 				v->cur_speed = u->First()->cur_speed;
 				/* We might be blocked, prevent pathfinding rerun as we already know where we are heading to. */
-				v->path.tile.push_front(tile);
-				v->path.td.push_front(dir);
+				v->path.push_front({ tile, dir });
 				return false;
 			}
 		}
@@ -1407,8 +1405,7 @@ again:
 			if (u != nullptr) {
 				v->cur_speed = u->First()->cur_speed;
 				/* We might be blocked, prevent pathfinding rerun as we already know where we are heading to. */
-				v->path.tile.push_front(v->tile);
-				v->path.td.push_front(dir);
+				v->path.push_front({ v->tile, dir });
 				return false;
 			}
 		}