Add: Road vehicle path cache. (#7261)

1 files changed, 33 insertions, 1 deletions

diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
index 970477001..559b87547 100644
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -924,6 +924,8 @@ static Trackdir RoadFindPathToDest(RoadVehicle *v, TileIndex tile, DiagDirection
 	/* Remove tracks unreachable from the enter dir */
 	trackdirs &= DiagdirReachesTrackdirs(enterdir);
 	if (trackdirs == TRACKDIR_BIT_NONE) {
+		/* If vehicle expected a path, it no longer exists, so invalidate it. */
+		if (!v->path.empty()) v->path.clear();
 		/* No reachable tracks, so we'll reverse */
 		return_track(_road_reverse_table[enterdir]);
 	}
@@ -954,12 +956,35 @@ 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) {
+			/* Vehicle expected a choice here, invalidate its path. */
+			v->path.clear();
+		}
 		return_track(FindFirstBit2x64(trackdirs));
 	}
 
+	/* Attempt to follow cached path. */
+	if (!v->path.empty()) {
+		if (v->path.tile.front() != tile) {
+			/* Vehicle didn't expect a choice here, invalidate its path. */
+			v->path.clear();
+		} else {
+			Trackdir trackdir = v->path.td.front();
+
+			if (HasBit(trackdirs, trackdir)) {
+				v->path.td.pop_front();
+				v->path.tile.pop_front();
+				return_track(trackdir);
+			}
+
+			/* Vehicle expected a choice which is no longer available. */
+			v->path.clear();
+		}
+	}
+
 	switch (_settings_game.pf.pathfinder_for_roadvehs) {
 		case VPF_NPF:  best_track = NPFRoadVehicleChooseTrack(v, tile, enterdir, path_found); break;
-		case VPF_YAPF: best_track = YapfRoadVehicleChooseTrack(v, tile, enterdir, trackdirs, path_found); break;
+		case VPF_YAPF: best_track = YapfRoadVehicleChooseTrack(v, tile, enterdir, trackdirs, path_found, v->path); break;
 
 		default: NOT_REACHED();
 	}
@@ -1600,6 +1625,13 @@ bool RoadVehicle::Tick()
 	return true;
 }
 
+void RoadVehicle::SetDestTile(TileIndex tile)
+{
+	if (tile == this->dest_tile) return;
+	this->path.clear();
+	this->dest_tile = tile;
+}
+
 static void CheckIfRoadVehNeedsService(RoadVehicle *v)
 {
 	/* If we already got a slot at a stop, use that FIRST, and go to a depot later */