Codechange: Replace HasVehicleOnPos and callbacks with HasVehicleOnTile and lambda-predicates.

src/rail_cmd.cpp

@@ -3032,14 +3032,6 @@ static CommandCost TestAutoslopeOnRailTile(TileIndex tile, DoCommandFlags flags,
 	return  cost;
 }
 
-/**
- * Test-procedure for HasVehicleOnPos to check for a ship.
- */
-static Vehicle *EnsureNoShipProc(Vehicle *v, void *)
-{
-	return v->type == VEH_SHIP ? v : nullptr;
-}
-
 static CommandCost TerraformTile_Track(TileIndex tile, DoCommandFlags flags, int z_new, Slope tileh_new)
 {
 	auto [tileh_old, z_old] = GetTileSlopeZ(tile);
@@ -3049,7 +3041,9 @@ static CommandCost TerraformTile_Track(TileIndex tile, DoCommandFlags flags, int
 		bool was_water = (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh_old));
 
 		/* Allow clearing the water only if there is no ship */
-		if (was_water && HasVehicleOnPos(tile, nullptr, &EnsureNoShipProc)) return CommandCost(STR_ERROR_SHIP_IN_THE_WAY);
+		if (was_water && HasVehicleOnTile(tile, [](const Vehicle *v) {
+				return v->type == VEH_SHIP;
+			})) return CommandCost(STR_ERROR_SHIP_IN_THE_WAY);
 
 		/* First test autoslope. However if it succeeds we still have to test the rest, because non-autoslope terraforming is cheaper. */
 		CommandCost autoslope_result = TestAutoslopeOnRailTile(tile, flags, z_old, tileh_old, z_new, tileh_new, rail_bits);

src/roadveh_cmd.cpp

@@ -767,13 +767,6 @@ struct OvertakeData {
 	Trackdir trackdir;
 };
 
-static Vehicle *EnumFindVehBlockingOvertake(Vehicle *v, void *data)
-{
-	const OvertakeData *od = (OvertakeData*)data;
-
-	return (v->type == VEH_ROAD && v->First() == v && v != od->u && v != od->v) ? v : nullptr;
-}
-
 /**
  * Check if overtaking is possible on a piece of track
  *
@@ -792,7 +785,9 @@ static bool CheckRoadBlockedForOvertaking(OvertakeData *od)
 	if (!HasBit(trackdirbits, od->trackdir) || (trackbits & ~TRACK_BIT_CROSS) || (red_signals != TRACKDIR_BIT_NONE)) return true;
 
 	/* Are there more vehicles on the tile except the two vehicles involved in overtaking */
-	return HasVehicleOnPos(od->tile, od, EnumFindVehBlockingOvertake);
+	return HasVehicleOnTile(od->tile, [&](const Vehicle *v) {
+		return v->type == VEH_ROAD && v->First() == v && v != od->u && v != od->v;
+	});
 }
 
 static void RoadVehCheckOvertake(RoadVehicle *v, RoadVehicle *u)

src/ship_cmd.cpp

@@ -359,14 +359,6 @@ void Ship::UpdateDeltaXY()
 	}
 }
 
-/**
- * Test-procedure for HasVehicleOnPos to check for any ships which are moving.
- */
-static Vehicle *EnsureNoMovingShipProc(Vehicle *v, void *)
-{
-	return v->type == VEH_SHIP && v->cur_speed != 0 ? v : nullptr;
-}
-
 static bool CheckReverseShip(const Ship *v, Trackdir *trackdir = nullptr)
 {
 	/* Ask pathfinder for best direction */
@@ -392,7 +384,9 @@ static bool CheckShipLeaveDepot(Ship *v)
 
 	/* Don't leave depot if another vehicle is already entering/leaving */
 	/* This helps avoid CPU load if many ships are set to start at the same time */
-	if (HasVehicleOnPos(v->tile, nullptr, &EnsureNoMovingShipProc)) return true;
+	if (HasVehicleOnTile(v->tile, [](const Vehicle *u) {
+			return u->type == VEH_SHIP && u->cur_speed != 0;
+		})) return true;
 
 	TileIndex tile = v->tile;
 	Axis axis = GetShipDepotAxis(tile);

src/signal.cpp

@@ -189,11 +189,9 @@ static SmallSet<DiagDirection, SIG_GLOB_SIZE> _globset("_globset"); ///< set of
 
 
 /** Check whether there is a train on rail, not in a depot */
-static Vehicle *TrainOnTileEnum(Vehicle *v, void *)
+static bool IsTrainAndNotInDepot(const Vehicle *v)
 {
-	if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return nullptr;
+	return v->type == VEH_TRAIN && Train::From(v)->track != TRACK_BIT_DEPOT;
-
-	return v;
 }
 
 
@@ -280,13 +278,13 @@ static SigFlags ExploreSegment(Owner owner)
 
 				if (IsRailDepot(tile)) {
 					if (enterdir == INVALID_DIAGDIR) { // from 'inside' - train just entered or left the depot
-						if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+						if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 						exitdir = GetRailDepotDirection(tile);
 						tile += TileOffsByDiagDir(exitdir);
 						enterdir = ReverseDiagDir(exitdir);
 						break;
 					} else if (enterdir == GetRailDepotDirection(tile)) { // entered a depot
-						if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+						if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 						continue;
 					} else {
 						continue;
@@ -303,7 +301,7 @@ static SigFlags ExploreSegment(Owner owner)
 					if (!flags.Test(SigFlag::Train) && EnsureNoTrainOnTrackBits(tile, tracks).Failed()) flags. Set(SigFlag::Train);
 				} else {
 					if (tracks_masked == TRACK_BIT_NONE) continue; // no incidating track
-					if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+					if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 				}
 
 				/* Is this a track merge or split? */
@@ -358,7 +356,7 @@ static SigFlags ExploreSegment(Owner owner)
 				if (DiagDirToAxis(enterdir) != GetRailStationAxis(tile)) continue; // different axis
 				if (IsStationTileBlocked(tile)) continue; // 'eye-candy' station tile
 
-				if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+				if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 				tile += TileOffsByDiagDir(exitdir);
 				break;
 
@@ -367,7 +365,7 @@ static SigFlags ExploreSegment(Owner owner)
 				if (GetTileOwner(tile) != owner) continue;
 				if (DiagDirToAxis(enterdir) == GetCrossingRoadAxis(tile)) continue; // different axis
 
-				if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+				if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 				tile += TileOffsByDiagDir(exitdir);
 				break;
 
@@ -377,13 +375,13 @@ static SigFlags ExploreSegment(Owner owner)
 				DiagDirection dir = GetTunnelBridgeDirection(tile);
 
 				if (enterdir == INVALID_DIAGDIR) { // incoming from the wormhole
-					if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+					if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 					enterdir = dir;
 					exitdir = ReverseDiagDir(dir);
 					tile += TileOffsByDiagDir(exitdir); // just skip to next tile
 				} else { // NOT incoming from the wormhole!
 					if (ReverseDiagDir(enterdir) != dir) continue;
-					if (!flags.Test(SigFlag::Train) && HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum)) flags.Set(SigFlag::Train);
+					if (!flags.Test(SigFlag::Train) && HasVehicleOnTile(tile, IsTrainAndNotInDepot)) flags.Set(SigFlag::Train);
 					tile = GetOtherTunnelBridgeEnd(tile); // just skip to exit tile
 					enterdir = INVALID_DIAGDIR;
 					exitdir = INVALID_DIAGDIR;

src/train_cmd.cpp

@@ -1664,15 +1664,14 @@ void ReverseTrainSwapVeh(Train *v, int l, int r)
 	}
 }
 
-
 /**
  * Check if the vehicle is a train
  * @param v vehicle on tile
- * @return v if it is a train, nullptr otherwise
+ * @return true if v is a train
  */
-static Vehicle *TrainOnTileEnum(Vehicle *v, void *)
+static bool IsTrain(const Vehicle *v)
 {
-	return (v->type == VEH_TRAIN) ? v : nullptr;
+	return v->type == VEH_TRAIN;
 }
 
 /**
@@ -1685,28 +1684,23 @@ bool TrainOnCrossing(TileIndex tile)
 {
 	assert(IsLevelCrossingTile(tile));
 
-	return HasVehicleOnPos(tile, nullptr, &TrainOnTileEnum);
+	return HasVehicleOnTile(tile, IsTrain);
 }
 
-
 /**
  * Checks if a train is approaching a rail-road crossing
  * @param v vehicle on tile
- * @param data tile with crossing we are testing
+ * @param tile tile with crossing we are testing
- * @return v if it is approaching a crossing, nullptr otherwise
+ * @return true if v is approaching a crossing
  */
-static Vehicle *TrainApproachingCrossingEnum(Vehicle *v, void *data)
+static bool TrainApproachingCrossingEnum(const Vehicle *v, TileIndex tile)
 {
-	if (v->type != VEH_TRAIN || v->vehstatus.Test(VehState::Crashed)) return nullptr;
+	if (v->type != VEH_TRAIN || v->vehstatus.Test(VehState::Crashed)) return false;
 
-	Train *t = Train::From(v);
+	const Train *t = Train::From(v);
-	if (!t->IsFrontEngine()) return nullptr;
+	if (!t->IsFrontEngine()) return false;
 
-	TileIndex tile = *(TileIndex *)data;
+	return TrainApproachingCrossingTile(t) == tile;
-
-	if (TrainApproachingCrossingTile(t) != tile) return nullptr;
-
-	return t;
 }
 
 
@@ -1723,12 +1717,16 @@ static bool TrainApproachingCrossing(TileIndex tile)
 	DiagDirection dir = AxisToDiagDir(GetCrossingRailAxis(tile));
 	TileIndex tile_from = tile + TileOffsByDiagDir(dir);
 
-	if (HasVehicleOnPos(tile_from, &tile, &TrainApproachingCrossingEnum)) return true;
+	if (HasVehicleOnTile(tile_from, [&](const Vehicle *v) {
+			return TrainApproachingCrossingEnum(v, tile);
+		})) return true;
 
 	dir = ReverseDiagDir(dir);
 	tile_from = tile + TileOffsByDiagDir(dir);
 
-	return HasVehicleOnPos(tile_from, &tile, &TrainApproachingCrossingEnum);
+	return HasVehicleOnTile(tile_from, [&](const Vehicle *v) {
+		return TrainApproachingCrossingEnum(v, tile);
+	});
 }
 
 /**
@@ -3252,21 +3250,6 @@ static bool CheckTrainCollision(Train *v)
 	return true;
 }
 
-static Vehicle *CheckTrainAtSignal(Vehicle *v, void *data)
-{
-	if (v->type != VEH_TRAIN || v->vehstatus.Test(VehState::Crashed)) return nullptr;
-
-	Train *t = Train::From(v);
-	DiagDirection exitdir = *(DiagDirection *)data;
-
-	/* not front engine of a train, inside wormhole or depot, crashed */
-	if (!t->IsFrontEngine() || !(t->track & TRACK_BIT_MASK)) return nullptr;
-
-	if (t->cur_speed > 5 || VehicleExitDir(t->direction, t->track) != exitdir) return nullptr;
-
-	return t;
-}
-
 /**
  * Move a vehicle chain one movement stop forwards.
  * @param v First vehicle to move.
@@ -3384,7 +3367,17 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 								exitdir = ReverseDiagDir(exitdir);
 
 								/* check if a train is waiting on the other side */
-								if (!HasVehicleOnPos(o_tile, &exitdir, &CheckTrainAtSignal)) return false;
+								if (!HasVehicleOnTile(o_tile, [&exitdir](const Vehicle *u) {
+										if (u->type != VEH_TRAIN || u->vehstatus.Test(VehState::Crashed)) return false;
+										const Train *t = Train::From(u);
+
+										/* not front engine of a train, inside wormhole or depot, crashed */
+										if (!t->IsFrontEngine() || !(t->track & TRACK_BIT_MASK)) return false;
+
+										if (t->cur_speed > 5 || VehicleExitDir(t->direction, t->track) != exitdir) return false;
+
+										return true;
+									})) return false;
 							}
 						}
 
@@ -3617,10 +3610,10 @@ static bool IsRailStationPlatformOccupied(TileIndex tile)
 	TileIndexDiff delta = TileOffsByAxis(GetRailStationAxis(tile));
 
 	for (TileIndex t = tile; IsCompatibleTrainStationTile(t, tile); t -= delta) {
-		if (HasVehicleOnPos(t, nullptr, &TrainOnTileEnum)) return true;
+		if (HasVehicleOnTile(t, IsTrain)) return true;
 	}
 	for (TileIndex t = tile + delta; IsCompatibleTrainStationTile(t, tile); t += delta) {
-		if (HasVehicleOnPos(t, nullptr, &TrainOnTileEnum)) return true;
+		if (HasVehicleOnTile(t, IsTrain)) return true;
 	}
 
 	return false;

src/vehicle.cpp

@@ -544,21 +544,6 @@ void FindVehicleOnPos(TileIndex tile, void *data, VehicleFromPosProc *proc)
 	VehicleFromPos(tile, data, proc, false);
 }
 
-/**
- * Checks whether a vehicle is on a specific location. It will call \a proc for
- * vehicles until it returns non-nullptr.
- * @note Use #FindVehicleOnPos when you have the intention that all vehicles
- *       should be iterated over.
- * @param tile The location on the map
- * @param data Arbitrary data passed to \a proc.
- * @param proc The \a proc that determines whether a vehicle will be "found".
- * @return True if proc returned non-nullptr.
- */
-bool HasVehicleOnPos(TileIndex tile, void *data, VehicleFromPosProc *proc)
-{
-	return VehicleFromPos(tile, data, proc, true) != nullptr;
-}
-
 /**
  * Callback that returns 'real' vehicles lower or at height \c *(int*)data .
  * @param v Vehicle to examine.

src/vehicle_func.h

@@ -98,13 +98,25 @@ private:
 	Iterator start;
 };
 
+/**
+ * Loop over vehicles on a tile, and check whether a predicate is true for any of them.
+ * The predicate must have the signature: bool Predicate(const Vehicle *);
+ */
+template <class UnaryPred>
+bool HasVehicleOnTile(TileIndex tile, UnaryPred &&predicate)
+{
+	for (const auto *v : VehiclesOnTile(tile)) {
+		if (predicate(v)) return true;
+	}
+	return false;
+}
+
 typedef Vehicle *VehicleFromPosProc(Vehicle *v, void *data);
 
 void VehicleServiceInDepot(Vehicle *v);
 uint CountVehiclesInChain(const Vehicle *v);
 void FindVehicleOnPos(TileIndex tile, void *data, VehicleFromPosProc *proc);
 void FindVehicleOnPosXY(int x, int y, void *data, VehicleFromPosProc *proc);
-bool HasVehicleOnPos(TileIndex tile, void *data, VehicleFromPosProc *proc);
 bool HasVehicleOnPosXY(int x, int y, void *data, VehicleFromPosProc *proc);
 void CallVehicleTicks();
 uint8_t CalcPercentVehicleFilled(const Vehicle *v, StringID *colour);