(svn r18364) -Codechange: move the pathfinders and their related files into a separate directory

1 files changed, 1120 insertions, 0 deletions

diff --git a/src/pathfinder/npf/npf.cpp b/src/pathfinder/npf/npf.cpp
new file mode 100644
index 000000000..f4211c298
--- /dev/null
+++ b/src/pathfinder/npf/npf.cpp
@@ -0,0 +1,1120 @@
+/* $Id$ */
+
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file npf.cpp Implementation of the NPF pathfinder. */
+
+#include "../../stdafx.h"
+#include "../../debug.h"
+#include "../../landscape.h"
+#include "../../depot_base.h"
+#include "../../network/network.h"
+#include "../../tunnelbridge_map.h"
+#include "../../functions.h"
+#include "../../tunnelbridge.h"
+#include "../../pbs.h"
+#include "../../train.h"
+#include "../pathfinder_func.h"
+#include "npf.h"
+
+static AyStar _npf_aystar;
+
+/* The cost of each trackdir. A diagonal piece is the full NPF_TILE_LENGTH,
+ * the shorter piece is sqrt(2)/2*NPF_TILE_LENGTH =~ 0.7071
+ */
+#define NPF_STRAIGHT_LENGTH (uint)(NPF_TILE_LENGTH * STRAIGHT_TRACK_LENGTH)
+static const uint _trackdir_length[TRACKDIR_END] = {
+	NPF_TILE_LENGTH, NPF_TILE_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH,
+	0, 0,
+	NPF_TILE_LENGTH, NPF_TILE_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH, NPF_STRAIGHT_LENGTH
+};
+
+/**
+ * Calculates the minimum distance traveled to get from t0 to t1 when only
+ * using tracks (ie, only making 45 degree turns). Returns the distance in the
+ * NPF scale, ie the number of full tiles multiplied by NPF_TILE_LENGTH to
+ * prevent rounding.
+ */
+static uint NPFDistanceTrack(TileIndex t0, TileIndex t1)
+{
+	const uint dx = Delta(TileX(t0), TileX(t1));
+	const uint dy = Delta(TileY(t0), TileY(t1));
+
+	const uint straightTracks = 2 * min(dx, dy); // The number of straight (not full length) tracks
+	/* OPTIMISATION:
+	 * Original: diagTracks = max(dx, dy) - min(dx,dy);
+	 * Proof:
+	 * (dx+dy) - straightTracks  == (min + max) - straightTracks = min + max - 2 * min = max - min */
+	const uint diagTracks = dx + dy - straightTracks; // The number of diagonal (full tile length) tracks.
+
+	/* Don't factor out NPF_TILE_LENGTH below, this will round values and lose
+	 * precision */
+	return diagTracks * NPF_TILE_LENGTH + straightTracks * NPF_TILE_LENGTH * STRAIGHT_TRACK_LENGTH;
+}
+
+
+#if 0
+static uint NTPHash(uint key1, uint key2)
+{
+	/* This function uses the old hash, which is fixed on 10 bits (1024 buckets) */
+	return PATHFIND_HASH_TILE(key1);
+}
+#endif
+
+/**
+ * Calculates a hash value for use in the NPF.
+ * @param key1 The TileIndex of the tile to hash
+ * @param key2 The Trackdir of the track on the tile.
+ *
+ * @todo Think of a better hash.
+ */
+static uint NPFHash(uint key1, uint key2)
+{
+	/* TODO: think of a better hash? */
+	uint part1 = TileX(key1) & NPF_HASH_HALFMASK;
+	uint part2 = TileY(key1) & NPF_HASH_HALFMASK;
+
+	assert(IsValidTrackdir((Trackdir)key2));
+	assert(IsValidTile(key1));
+	return ((part1 << NPF_HASH_HALFBITS | part2) + (NPF_HASH_SIZE * key2 / TRACKDIR_END)) % NPF_HASH_SIZE;
+}
+
+static int32 NPFCalcZero(AyStar *as, AyStarNode *current, OpenListNode *parent)
+{
+	return 0;
+}
+
+/* Calcs the heuristic to the target station or tile. For train stations, it
+ * takes into account the direction of approach.
+ */
+static int32 NPFCalcStationOrTileHeuristic(AyStar *as, AyStarNode *current, OpenListNode *parent)
+{
+	NPFFindStationOrTileData *fstd = (NPFFindStationOrTileData*)as->user_target;
+	NPFFoundTargetData *ftd = (NPFFoundTargetData*)as->user_path;
+	TileIndex from = current->tile;
+	TileIndex to = fstd->dest_coords;
+	uint dist;
+
+	/* for train-stations, we are going to aim for the closest station tile */
+	if (as->user_data[NPF_TYPE] == TRANSPORT_RAIL && fstd->station_index != INVALID_STATION)
+		to = CalcClosestStationTile(fstd->station_index, from);
+
+	if (as->user_data[NPF_TYPE] == TRANSPORT_ROAD) {
+		/* Since roads only have diagonal pieces, we use manhattan distance here */
+		dist = DistanceManhattan(from, to) * NPF_TILE_LENGTH;
+	} else {
+		/* Ships and trains can also go diagonal, so the minimum distance is shorter */
+		dist = NPFDistanceTrack(from, to);
+	}
+
+	DEBUG(npf, 4, "Calculating H for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), dist);
+
+	if (dist < ftd->best_bird_dist) {
+		ftd->best_bird_dist = dist;
+		ftd->best_trackdir = (Trackdir)current->user_data[NPF_TRACKDIR_CHOICE];
+	}
+	return dist;
+}
+
+
+/* Fills AyStarNode.user_data[NPF_TRACKDIRCHOICE] with the chosen direction to
+ * get here, either getting it from the current choice or from the parent's
+ * choice */
+static void NPFFillTrackdirChoice(AyStarNode *current, OpenListNode *parent)
+{
+	if (parent->path.parent == NULL) {
+		Trackdir trackdir = current->direction;
+		/* This is a first order decision, so we'd better save the
+		 * direction we chose */
+		current->user_data[NPF_TRACKDIR_CHOICE] = trackdir;
+		DEBUG(npf, 6, "Saving trackdir: 0x%X", trackdir);
+	} else {
+		/* We've already made the decision, so just save our parent's decision */
+		current->user_data[NPF_TRACKDIR_CHOICE] = parent->path.node.user_data[NPF_TRACKDIR_CHOICE];
+	}
+}
+
+/* Will return the cost of the tunnel. If it is an entry, it will return the
+ * cost of that tile. If the tile is an exit, it will return the tunnel length
+ * including the exit tile. Requires that this is a Tunnel tile */
+static uint NPFTunnelCost(AyStarNode *current)
+{
+	DiagDirection exitdir = TrackdirToExitdir(current->direction);
+	TileIndex tile = current->tile;
+	if (GetTunnelBridgeDirection(tile) == ReverseDiagDir(exitdir)) {
+		/* We just popped out if this tunnel, since were
+		 * facing the tunnel exit */
+		return NPF_TILE_LENGTH * (GetTunnelBridgeLength(current->tile, GetOtherTunnelEnd(current->tile)) + 1);
+		/* @todo: Penalty for tunnels? */
+	} else {
+		/* We are entering the tunnel, the enter tile is just a
+		 * straight track */
+		return NPF_TILE_LENGTH;
+	}
+}
+
+static inline uint NPFBridgeCost(AyStarNode *current)
+{
+	return NPF_TILE_LENGTH * GetTunnelBridgeLength(current->tile, GetOtherBridgeEnd(current->tile));
+}
+
+static uint NPFSlopeCost(AyStarNode *current)
+{
+	TileIndex next = current->tile + TileOffsByDiagDir(TrackdirToExitdir(current->direction));
+
+	/* Get center of tiles */
+	int x1 = TileX(current->tile) * TILE_SIZE + TILE_SIZE / 2;
+	int y1 = TileY(current->tile) * TILE_SIZE + TILE_SIZE / 2;
+	int x2 = TileX(next) * TILE_SIZE + TILE_SIZE / 2;
+	int y2 = TileY(next) * TILE_SIZE + TILE_SIZE / 2;
+
+	int dx4 = (x2 - x1) / 4;
+	int dy4 = (y2 - y1) / 4;
+
+	/* Get the height on both sides of the tile edge.
+	 * Avoid testing the height on the tile-center. This will fail for halftile-foundations.
+	 */
+	int z1 = GetSlopeZ(x1 + dx4, y1 + dy4);
+	int z2 = GetSlopeZ(x2 - dx4, y2 - dy4);
+
+	if (z2 - z1 > 1) {
+		/* Slope up */
+		return _settings_game.pf.npf.npf_rail_slope_penalty;
+	}
+	return 0;
+	/* Should we give a bonus for slope down? Probably not, we
+	 * could just substract that bonus from the penalty, because
+	 * there is only one level of steepness... */
+}
+
+static uint NPFReservedTrackCost(AyStarNode *current)
+{
+	TileIndex tile = current->tile;
+	TrackBits track = TrackToTrackBits(TrackdirToTrack(current->direction));
+	TrackBits res = GetReservedTrackbits(tile);
+
+	if (NPFGetFlag(current, NPF_FLAG_3RD_SIGNAL) || ((res & track) == TRACK_BIT_NONE && !TracksOverlap(res | track))) return 0;
+
+	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
+		DiagDirection exitdir = TrackdirToExitdir(current->direction);
+		if (GetTunnelBridgeDirection(tile) == ReverseDiagDir(exitdir)) {
+			return  _settings_game.pf.npf.npf_rail_pbs_cross_penalty * (GetTunnelBridgeLength(tile, GetOtherTunnelBridgeEnd(tile)) + 1);
+		}
+	}
+	return  _settings_game.pf.npf.npf_rail_pbs_cross_penalty;
+}
+
+/**
+ * Mark tiles by mowing the grass when npf debug level >= 1.
+ * Will not work for multiplayer games, since it can (will) cause desyncs.
+ */
+static void NPFMarkTile(TileIndex tile)
+{
+#ifndef NO_DEBUG_MESSAGES
+	if (_debug_npf_level < 1 || _networking) return;
+	switch (GetTileType(tile)) {
+		case MP_RAILWAY:
+			/* DEBUG: mark visited tiles by mowing the grass under them ;-) */
+			if (!IsRailDepot(tile)) {
+				SetRailGroundType(tile, RAIL_GROUND_BARREN);
+				MarkTileDirtyByTile(tile);
+			}
+			break;
+
+		case MP_ROAD:
+			if (!IsRoadDepot(tile)) {
+				SetRoadside(tile, ROADSIDE_BARREN);
+				MarkTileDirtyByTile(tile);
+			}
+			break;
+
+		default:
+			break;
+	}
+#endif
+}
+
+static int32 NPFWaterPathCost(AyStar *as, AyStarNode *current, OpenListNode *parent)
+{
+	/* TileIndex tile = current->tile; */
+	int32 cost = 0;
+	Trackdir trackdir = current->direction;
+
+	cost = _trackdir_length[trackdir]; // Should be different for diagonal tracks
+
+	if (IsBuoyTile(current->tile) && IsDiagonalTrackdir(trackdir))
+		cost += _settings_game.pf.npf.npf_buoy_penalty; // A small penalty for going over buoys
+
+	if (current->direction != NextTrackdir((Trackdir)parent->path.node.direction))
+		cost += _settings_game.pf.npf.npf_water_curve_penalty;
+
+	/* @todo More penalties? */
+
+	return cost;
+}
+
+/* Determine the cost of this node, for road tracks */
+static int32 NPFRoadPathCost(AyStar *as, AyStarNode *current, OpenListNode *parent)
+{
+	TileIndex tile = current->tile;
+	int32 cost = 0;
+
+	/* Determine base length */
+	switch (GetTileType(tile)) {
+		case MP_TUNNELBRIDGE:
+			cost = IsTunnel(tile) ? NPFTunnelCost(current) : NPFBridgeCost(current);
+			break;
+
+		case MP_ROAD:
+			cost = NPF_TILE_LENGTH;
+			/* Increase the cost for level crossings */
+			if (IsLevelCrossing(tile)) cost += _settings_game.pf.npf.npf_crossing_penalty;
+			break;
+
+		case MP_STATION:
+			cost = NPF_TILE_LENGTH;
+			/* Increase the cost for drive-through road stops */
+			if (IsDriveThroughStopTile(tile)) cost += _settings_game.pf.npf.npf_road_drive_through_penalty;
+			break;
+
+		default:
+			break;
+	}
+
+	/* Determine extra costs */
+
+	/* Check for slope */
+	cost += NPFSlopeCost(current);
+
+	/* Check for turns. Road vehicles only really drive diagonal, turns are
+	 * represented by non-diagonal tracks */
+	if (!IsDiagonalTrackdir(current->direction))
+		cost += _settings_game.pf.npf.npf_road_curve_penalty;
+
+	NPFMarkTile(tile);
+	DEBUG(npf, 4, "Calculating G for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), cost);
+	return cost;
+}
+
+
+/* Determine the cost of this node, for railway tracks */
+static int32 NPFRailPathCost(AyStar *as, AyStarNode *current, OpenListNode *parent)
+{
+	TileIndex tile = current->tile;
+	Trackdir trackdir = current->direction;
+	int32 cost = 0;
+	/* HACK: We create a OpenListNode manually, so we can call EndNodeCheck */
+	OpenListNode new_node;
+
+	/* Determine base length */
+	switch (GetTileType(tile)) {
+		case MP_TUNNELBRIDGE:
+			cost = IsTunnel(tile) ? NPFTunnelCost(current) : NPFBridgeCost(current);
+			break;
+
+		case MP_RAILWAY:
+			cost = _trackdir_length[trackdir]; // Should be different for diagonal tracks
+			break;
+
+		case MP_ROAD: // Railway crossing
+			cost = NPF_TILE_LENGTH;
+			break;
+
+		case MP_STATION:
+			/* We give a station tile a penalty. Logically we would only want to give
+			 * station tiles that are not our destination this penalty. This would
+			 * discourage trains to drive through busy stations. But, we can just
+			 * give any station tile a penalty, because every possible route will get
+			 * this penalty exactly once, on its end tile (if it's a station) and it
+			 * will therefore not make a difference. */
+			cost = NPF_TILE_LENGTH + _settings_game.pf.npf.npf_rail_station_penalty;
+			break;
+
+		default:
+			break;
+	}
+
+	/* Determine extra costs */
+
+	/* Check for signals */
+	if (IsTileType(tile, MP_RAILWAY)) {
+		if (HasSignalOnTrackdir(tile, trackdir)) {
+			/* Ordinary track with signals */
+			if (GetSignalStateByTrackdir(tile, trackdir) == SIGNAL_STATE_RED) {
+				/* Signal facing us is red */
+				if (!NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL)) {
+					/* Penalize the first signal we
+					 * encounter, if it is red */
+
+					/* Is this a presignal exit or combo? */
+					SignalType sigtype = GetSignalType(tile, TrackdirToTrack(trackdir));
+					if (!IsPbsSignal(sigtype)) {
+						if (sigtype == SIGTYPE_EXIT || sigtype == SIGTYPE_COMBO) {
+							/* Penalise exit and combo signals differently (heavier) */
+							cost += _settings_game.pf.npf.npf_rail_firstred_exit_penalty;
+						} else {
+							cost += _settings_game.pf.npf.npf_rail_firstred_penalty;
+						}
+					}
+				}
+				/* Record the state of this signal */
+				NPFSetFlag(current, NPF_FLAG_LAST_SIGNAL_RED, true);
+			} else {
+				/* Record the state of this signal */
+				NPFSetFlag(current, NPF_FLAG_LAST_SIGNAL_RED, false);
+			}
+			if (NPFGetFlag(current, NPF_FLAG_SEEN_SIGNAL)) {
+				if (NPFGetFlag(current, NPF_FLAG_2ND_SIGNAL)) {
+					NPFSetFlag(current, NPF_FLAG_3RD_SIGNAL, true);
+				} else {
+					NPFSetFlag(current, NPF_FLAG_2ND_SIGNAL, true);
+				}
+			} else {
+				NPFSetFlag(current, NPF_FLAG_SEEN_SIGNAL, true);
+			}
+		}
+
+		if (HasPbsSignalOnTrackdir(tile, ReverseTrackdir(trackdir)) && !NPFGetFlag(current, NPF_FLAG_3RD_SIGNAL)) {
+			cost += _settings_game.pf.npf.npf_rail_pbs_signal_back_penalty;
+		}
+	}
+
+	/* Penalise the tile if it is a target tile and the last signal was
+	 * red */
+	/* HACK: We create a new_node here so we can call EndNodeCheck. Ugly as hell
+	 * of course... */
+	new_node.path.node = *current;
+	if (as->EndNodeCheck(as, &new_node) == AYSTAR_FOUND_END_NODE && NPFGetFlag(current, NPF_FLAG_LAST_SIGNAL_RED))
+		cost += _settings_game.pf.npf.npf_rail_lastred_penalty;
+
+	/* Check for slope */
+	cost += NPFSlopeCost(current);
+
+	/* Check for turns */
+	if (current->direction != NextTrackdir((Trackdir)parent->path.node.direction))
+		cost += _settings_game.pf.npf.npf_rail_curve_penalty;
+	/* TODO, with realistic acceleration, also the amount of straight track between
+	 *      curves should be taken into account, as this affects the speed limit. */
+
+	/* Check for reverse in depot */
+	if (IsRailDepotTile(tile) && as->EndNodeCheck(as, &new_node) != AYSTAR_FOUND_END_NODE) {
+		/* Penalise any depot tile that is not the last tile in the path. This
+		 * _should_ penalise every occurence of reversing in a depot (and only
+		 * that) */
+		cost += _settings_game.pf.npf.npf_rail_depot_reverse_penalty;
+	}
+
+	/* Check for occupied track */
+	cost += NPFReservedTrackCost(current);
+
+	NPFMarkTile(tile);
+	DEBUG(npf, 4, "Calculating G for: (%d, %d). Result: %d", TileX(current->tile), TileY(current->tile), cost);
+	return cost;
+}
+
+/* Will find any depot */
+static int32 NPFFindDepot(AyStar *as, OpenListNode *current)
+{
+	/* It's not worth caching the result with NPF_FLAG_IS_TARGET here as below,
+	 * since checking the cache not that much faster than the actual check */
+	return IsDepotTypeTile(current->path.node.tile, (TransportType)as->user_data[NPF_TYPE]) ?
+		AYSTAR_FOUND_END_NODE : AYSTAR_DONE;
+}
+
+/** Find any safe and free tile. */
+static int32 NPFFindSafeTile(AyStar *as, OpenListNode *current)
+{
+	const Train *v = Train::From(((NPFFindStationOrTileData *)as->user_target)->v);
+
+	return
+		IsSafeWaitingPosition(v, current->path.node.tile, current->path.node.direction, true, _settings_game.pf.forbid_90_deg) &&
+		IsWaitingPositionFree(v, current->path.node.tile, current->path.node.direction, _settings_game.pf.forbid_90_deg) ?
+			AYSTAR_FOUND_END_NODE : AYSTAR_DONE;
+}
+
+/* Will find a station identified using the NPFFindStationOrTileData */
+static int32 NPFFindStationOrTile(AyStar *as, OpenListNode *current)
+{
+	NPFFindStationOrTileData *fstd = (NPFFindStationOrTileData*)as->user_target;
+	AyStarNode *node = &current->path.node;
+	TileIndex tile = node->tile;
+
+	/* If GetNeighbours said we could get here, we assume the station type
+	 * is correct */
+	if (
+		(fstd->station_index == INVALID_STATION && tile == fstd->dest_coords) || // We've found the tile, or
+		(IsTileType(tile, MP_STATION) && GetStationIndex(tile) == fstd->station_index) // the station
+	) {
+		return AYSTAR_FOUND_END_NODE;
+	} else {
+		return AYSTAR_DONE;
+	}
+}
+
+/**
+ * Find the node containing the first signal on the path.
+ *
+ * If the first signal is on the very first two tiles of the path,
+ * the second signal is returnd. If no suitable signal is present, the
+ * last node of the path is returned.
+ */
+static const PathNode *FindSafePosition(PathNode *path, const Train *v)
+{
+	/* If there is no signal, reserve the whole path. */
+	PathNode *sig = path;
+
+	for (; path->parent != NULL; path = path->parent) {
+		if (IsSafeWaitingPosition(v, path->node.tile, path->node.direction, true, _settings_game.pf.forbid_90_deg)) {
+			sig = path;
+		}
+	}
+
+	return sig;
+}
+
+/**
+ * Lift the reservation of the tiles from @p start till @p end, excluding @p end itself.
+ */
+static void ClearPathReservation(const PathNode *start, const PathNode *end)
+{
+	bool first_run = true;
+	for (; start != end; start = start->parent) {
+		if (IsRailStationTile(start->node.tile) && first_run) {
+			SetRailStationPlatformReservation(start->node.tile, TrackdirToExitdir(start->node.direction), false);
+		} else {
+			UnreserveRailTrack(start->node.tile, TrackdirToTrack(start->node.direction));
+		}
+		first_run = false;
+	}
+}
+
+/**
+ * To be called when @p current contains the (shortest route to) the target node.
+ * Will fill the contents of the NPFFoundTargetData using
+ * AyStarNode[NPF_TRACKDIR_CHOICE]. If requested, path reservation
+ * is done here.
+ */
+static void NPFSaveTargetData(AyStar *as, OpenListNode *current)
+{
+	NPFFoundTargetData *ftd = (NPFFoundTargetData*)as->user_path;
+	ftd->best_trackdir = (Trackdir)current->path.node.user_data[NPF_TRACKDIR_CHOICE];
+	ftd->best_path_dist = current->g;
+	ftd->best_bird_dist = 0;
+	ftd->node = current->path.node;
+	ftd->res_okay = false;
+
+	if (as->user_target != NULL && ((NPFFindStationOrTileData*)as->user_target)->reserve_path && as->user_data[NPF_TYPE] == TRANSPORT_RAIL) {
+		/* Path reservation is requested. */
+		const Train *v = Train::From(((NPFFindStationOrTileData *)as->user_target)->v);
+
+		const PathNode *target = FindSafePosition(&current->path, v);
+		ftd->node = target->node;
+
+		/* If the target is a station skip to platform end. */
+		if (IsRailStationTile(target->node.tile)) {
+			DiagDirection dir = TrackdirToExitdir(target->node.direction);
+			uint len = Station::GetByTile(target->node.tile)->GetPlatformLength(target->node.tile, dir);
+			TileIndex end_tile = TILE_ADD(target->node.tile, (len - 1) * TileOffsByDiagDir(dir));
+
+			/* Update only end tile, trackdir of a station stays the same. */
+			ftd->node.tile = end_tile;
+			if (!IsWaitingPositionFree(v, end_tile, target->node.direction, _settings_game.pf.forbid_90_deg)) return;
+			SetRailStationPlatformReservation(target->node.tile, dir, true);
+			SetRailStationReservation(target->node.tile, false);
+		} else {
+			if (!IsWaitingPositionFree(v, target->node.tile, target->node.direction, _settings_game.pf.forbid_90_deg)) return;
+		}
+
+		for (const PathNode *cur = target; cur->parent != NULL; cur = cur->parent) {
+			if (!TryReserveRailTrack(cur->node.tile, TrackdirToTrack(cur->node.direction))) {
+				/* Reservation failed, undo. */
+				ClearPathReservation(target, cur);
+				return;
+			}
+		}
+
+		ftd->res_okay = true;
+	}
+}
+
+/**
+ * Finds out if a given company's vehicles are allowed to enter a given tile.
+ * @param owner    The owner of the vehicle.
+ * @param tile     The tile that is about to be entered.
+ * @param enterdir The direction in which the vehicle wants to enter the tile.
+ * @return         true if the vehicle can enter the tile.
+ * @todo           This function should be used in other places than just NPF,
+ *                 maybe moved to another file too.
+ */
+static bool CanEnterTileOwnerCheck(Owner owner, TileIndex tile, DiagDirection enterdir)
+{
+	if (IsTileType(tile, MP_RAILWAY) || // Rail tile (also rail depot)
+			HasStationTileRail(tile) ||     // Rail station tile/waypoint
+			IsRoadDepotTile(tile) ||        // Road depot tile
+			IsStandardRoadStopTile(tile)) { // Road station tile (but not drive-through stops)
+		return IsTileOwner(tile, owner);  // You need to own these tiles entirely to use them
+	}
+
+	switch (GetTileType(tile)) {
+		case MP_ROAD:
+			/* rail-road crossing : are we looking at the railway part? */
+			if (IsLevelCrossing(tile) &&
+					DiagDirToAxis(enterdir) != GetCrossingRoadAxis(tile)) {
+				return IsTileOwner(tile, owner); // Railway needs owner check, while the street is public
+			}
+			break;
+
+		case MP_TUNNELBRIDGE:
+			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
+				return IsTileOwner(tile, owner);
+			}
+			break;
+
+		default:
+			break;
+	}
+
+	return true; // no need to check
+}
+
+
+/**
+ * Returns the direction the exit of the depot on the given tile is facing.
+ */
+static DiagDirection GetDepotDirection(TileIndex tile, TransportType type)
+{
+	assert(IsDepotTypeTile(tile, type));
+
+	switch (type) {
+		case TRANSPORT_RAIL:  return GetRailDepotDirection(tile);
+		case TRANSPORT_ROAD:  return GetRoadDepotDirection(tile);
+		case TRANSPORT_WATER: return GetShipDepotDirection(tile);
+		default: return INVALID_DIAGDIR; // Not reached
+	}
+}
+
+/** Tests if a tile is a road tile with a single tramtrack (tram can reverse) */
+static DiagDirection GetSingleTramBit(TileIndex tile)
+{
+	if (IsNormalRoadTile(tile)) {
+		RoadBits rb = GetRoadBits(tile, ROADTYPE_TRAM);
+		switch (rb) {
+			case ROAD_NW: return DIAGDIR_NW;
+			case ROAD_SW: return DIAGDIR_SW;
+			case ROAD_SE: return DIAGDIR_SE;
+			case ROAD_NE: return DIAGDIR_NE;
+			default: break;
+		}
+	}
+	return INVALID_DIAGDIR;
+}
+
+/**
+ * Tests if a tile can be entered or left only from one side.
+ *
+ * Depots, non-drive-through roadstops, and tiles with single trambits are tested.
+ *
+ * @param tile The tile of interest.
+ * @param type The transporttype of the vehicle.
+ * @param subtype For TRANSPORT_ROAD the compatible RoadTypes of the vehicle.
+ * @return The single entry/exit-direction of the tile, or INVALID_DIAGDIR if there are more or less directions
+ */
+static DiagDirection GetTileSingleEntry(TileIndex tile, TransportType type, uint subtype)
+{
+	if (type != TRANSPORT_WATER && IsDepotTypeTile(tile, type)) return GetDepotDirection(tile, type);
+
+	if (type == TRANSPORT_ROAD) {
+		if (IsStandardRoadStopTile(tile)) return GetRoadStopDir(tile);
+		if (HasBit(subtype, ROADTYPE_TRAM)) return GetSingleTramBit(tile);
+	}
+
+	return INVALID_DIAGDIR;
+}
+
+/**
+ * Tests if a vehicle must reverse on a tile.
+ *
+ * @param tile The tile of interest.
+ * @param dir The direction in which the vehicle drives on a tile.
+ * @param type The transporttype of the vehicle.
+ * @param subtype For TRANSPORT_ROAD the compatible RoadTypes of the vehicle.
+ * @return true iff the vehicle must reverse on the tile.
+ */
+static inline bool ForceReverse(TileIndex tile, DiagDirection dir, TransportType type, uint subtype)
+{
+	DiagDirection single_entry = GetTileSingleEntry(tile, type, subtype);
+	return single_entry != INVALID_DIAGDIR && single_entry != dir;
+}
+
+/**
+ * Tests if a vehicle can enter a tile.
+ *
+ * @param tile The tile of interest.
+ * @param dir The direction in which the vehicle drives onto a tile.
+ * @param type The transporttype of the vehicle.
+ * @param subtype For TRANSPORT_ROAD the compatible RoadTypes of the vehicle.
+ * @param railtypes For TRANSPORT_RAIL the compatible RailTypes of the vehicle.
+ * @param owner The owner of the vehicle.
+ * @return true iff the vehicle can enter the tile.
+ */
+static bool CanEnterTile(TileIndex tile, DiagDirection dir, TransportType type, uint subtype, RailTypes railtypes, Owner owner)
+{
+	/* Check tunnel entries and bridge ramps */
+	if (IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(tile) != dir) return false;
+
+	/* Test ownership */
+	if (!CanEnterTileOwnerCheck(owner, tile, dir)) return false;
+
+	/* check correct rail type (mono, maglev, etc) */
+	if (type == TRANSPORT_RAIL) {
+		RailType rail_type = GetTileRailType(tile);
+		if (!HasBit(railtypes, rail_type)) return false;
+	}
+
+	/* Depots, standard roadstops and single tram bits can only be entered from one direction */
+	DiagDirection single_entry = GetTileSingleEntry(tile, type, subtype);
+	if (single_entry != INVALID_DIAGDIR && single_entry != ReverseDiagDir(dir)) return false;
+
+	return true;
+}
+
+/**
+ * Returns the driveable Trackdirs on a tile.
+ *
+ * One-way-roads are taken into account. Signals are not tested.
+ *
+ * @param dst_tile The tile of interest.
+ * @param src_trackdir The direction the vehicle is currently moving.
+ * @param type The transporttype of the vehicle.
+ * @param subtype For TRANSPORT_ROAD the compatible RoadTypes of the vehicle.
+ * @return The Trackdirs the vehicle can continue moving on.
+ */
+static TrackdirBits GetDriveableTrackdirBits(TileIndex dst_tile, Trackdir src_trackdir, TransportType type, uint subtype)
+{
+	TrackdirBits trackdirbits = TrackStatusToTrackdirBits(GetTileTrackStatus(dst_tile, type, subtype));
+
+	if (trackdirbits == 0 && type == TRANSPORT_ROAD && HasBit(subtype, ROADTYPE_TRAM)) {
+		/* GetTileTrackStatus() returns 0 for single tram bits.
+		 * As we cannot change it there (easily) without breaking something, change it here */
+		switch (GetSingleTramBit(dst_tile)) {
+			case DIAGDIR_NE:
+			case DIAGDIR_SW:
+				trackdirbits = TRACKDIR_BIT_X_NE | TRACKDIR_BIT_X_SW;
+				break;
+
+			case DIAGDIR_NW:
+			case DIAGDIR_SE:
+				trackdirbits = TRACKDIR_BIT_Y_NW | TRACKDIR_BIT_Y_SE;
+				break;
+
+			default: break;
+		}
+	}
+
+	DEBUG(npf, 4, "Next node: (%d, %d) [%d], possible trackdirs: 0x%X", TileX(dst_tile), TileY(dst_tile), dst_tile, trackdirbits);
+
+	/* Select only trackdirs we can reach from our current trackdir */
+	trackdirbits &= TrackdirReachesTrackdirs(src_trackdir);
+
+	/* Filter out trackdirs that would make 90 deg turns for trains */
+	if (_settings_game.pf.forbid_90_deg && (type == TRANSPORT_RAIL || type == TRANSPORT_WATER)) trackdirbits &= ~TrackdirCrossesTrackdirs(src_trackdir);
+
+	DEBUG(npf, 6, "After filtering: (%d, %d), possible trackdirs: 0x%X", TileX(dst_tile), TileY(dst_tile), trackdirbits);
+
+	return trackdirbits;
+}
+
+
+/* Will just follow the results of GetTileTrackStatus concerning where we can
+ * go and where not. Uses AyStar.user_data[NPF_TYPE] as the transport type and
+ * an argument to GetTileTrackStatus. Will skip tunnels, meaning that the
+ * entry and exit are neighbours. Will fill
+ * AyStarNode.user_data[NPF_TRACKDIR_CHOICE] with an appropriate value, and
+ * copy AyStarNode.user_data[NPF_NODE_FLAGS] from the parent */
+static void NPFFollowTrack(AyStar *aystar, OpenListNode *current)
+{
+	/* We leave src_tile on track src_trackdir in direction src_exitdir */
+	Trackdir src_trackdir = current->path.node.direction;
+	TileIndex src_tile = current->path.node.tile;
+	DiagDirection src_exitdir = TrackdirToExitdir(src_trackdir);
+
+	/* Is src_tile valid, and can be used?
+	 * When choosing track on a junction src_tile is the tile neighboured to the junction wrt. exitdir.
+	 * But we must not check the validity of this move, as src_tile is totally unrelated to the move, if a roadvehicle reversed on a junction. */
+	bool ignore_src_tile = (current->path.parent == NULL && NPFGetFlag(&current->path.node, NPF_FLAG_IGNORE_START_TILE));
+
+	/* Information about the vehicle: TransportType (road/rail/water) and SubType (compatible rail/road types) */
+	TransportType type = (TransportType)aystar->user_data[NPF_TYPE];
+	uint subtype = aystar->user_data[NPF_SUB_TYPE];
+
+	/* Initialize to 0, so we can jump out (return) somewhere an have no neighbours */
+	aystar->num_neighbours = 0;
+	DEBUG(npf, 4, "Expanding: (%d, %d, %d) [%d]", TileX(src_tile), TileY(src_tile), src_trackdir, src_tile);
+
+	/* We want to determine the tile we arrive, and which choices we have there */
+	TileIndex dst_tile;
+	TrackdirBits trackdirbits;
+
+	/* Find dest tile */
+	if (ignore_src_tile) {
+		/* Do not perform any checks that involve src_tile */
+		dst_tile = src_tile + TileOffsByDiagDir(src_exitdir);
+		trackdirbits = GetDriveableTrackdirBits(dst_tile, src_trackdir, type, subtype);
+	} else if (IsTileType(src_tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(src_tile) == src_exitdir) {
+		/* We drive through the wormhole and arrive on the other side */
+		dst_tile = GetOtherTunnelBridgeEnd(src_tile);
+		trackdirbits = TrackdirToTrackdirBits(src_trackdir);
+	} else if (ForceReverse(src_tile, src_exitdir, type, subtype)) {
+		/* We can only reverse on this tile */
+		dst_tile = src_tile;
+		src_trackdir = ReverseTrackdir(src_trackdir);
+		trackdirbits = TrackdirToTrackdirBits(src_trackdir);
+	} else {
+		/* We leave src_tile in src_exitdir and reach dst_tile */
+		dst_tile = AddTileIndexDiffCWrap(src_tile, TileIndexDiffCByDiagDir(src_exitdir));
+
+		if (dst_tile != INVALID_TILE && !CanEnterTile(dst_tile, src_exitdir, type, subtype, (RailTypes)aystar->user_data[NPF_RAILTYPES], (Owner)aystar->user_data[NPF_OWNER])) dst_tile = INVALID_TILE;
+
+		if (dst_tile == INVALID_TILE) {
+			/* We cannot enter the next tile. Road vehicles can reverse, others reach dead end */
+			if (type != TRANSPORT_ROAD || HasBit(subtype, ROADTYPE_TRAM)) return;
+
+			dst_tile = src_tile;
+			src_trackdir = ReverseTrackdir(src_trackdir);
+		}
+
+		trackdirbits = GetDriveableTrackdirBits(dst_tile, src_trackdir, type, subtype);
+
+		if (trackdirbits == 0) {
+			/* We cannot enter the next tile. Road vehicles can reverse, others reach dead end */
+			if (type != TRANSPORT_ROAD || HasBit(subtype, ROADTYPE_TRAM)) return;
+
+			dst_tile = src_tile;
+			src_trackdir = ReverseTrackdir(src_trackdir);
+
+			trackdirbits = GetDriveableTrackdirBits(dst_tile, src_trackdir, type, subtype);
+		}
+	}
+
+	if (NPFGetFlag(&current->path.node, NPF_FLAG_IGNORE_RESERVED)) {
+		/* Mask out any reserved tracks. */
+		TrackBits reserved = GetReservedTrackbits(dst_tile);
+		trackdirbits &= ~TrackBitsToTrackdirBits(reserved);
+
+		uint bits = TrackdirBitsToTrackBits(trackdirbits);
+		int i;
+		FOR_EACH_SET_BIT(i, bits) {
+			if (TracksOverlap(reserved | TrackToTrackBits((Track)i))) trackdirbits &= ~TrackToTrackdirBits((Track)i);
+		}
+	}
+
+	/* Enumerate possible track */
+	uint i = 0;
+	while (trackdirbits != 0) {
+		Trackdir dst_trackdir = RemoveFirstTrackdir(&trackdirbits);
+		DEBUG(npf, 5, "Expanded into trackdir: %d, remaining trackdirs: 0x%X", dst_trackdir, trackdirbits);
+
+		/* Tile with signals? */
+		if (IsTileType(dst_tile, MP_RAILWAY) && GetRailTileType(dst_tile) == RAIL_TILE_SIGNALS) {
+			if (HasSignalOnTrackdir(dst_tile, ReverseTrackdir(dst_trackdir)) && !HasSignalOnTrackdir(dst_tile, dst_trackdir) && IsOnewaySignal(dst_tile, TrackdirToTrack(dst_trackdir)))
+				/* If there's a one-way signal not pointing towards us, stop going in this direction. */
+				break;
+		}
+		{
+			/* We've found ourselves a neighbour :-) */
+			AyStarNode *neighbour = &aystar->neighbours[i];
+			neighbour->tile = dst_tile;
+			neighbour->direction = dst_trackdir;
+			/* Save user data */
+			neighbour->user_data[NPF_NODE_FLAGS] = current->path.node.user_data[NPF_NODE_FLAGS];
+			NPFFillTrackdirChoice(neighbour, current);
+		}
+		i++;
+	}
+	aystar->num_neighbours = i;
+}
+
+/*
+ * Plan a route to the specified target (which is checked by target_proc),
+ * from start1 and if not NULL, from start2 as well. The type of transport we
+ * are checking is in type. reverse_penalty is applied to all routes that
+ * originate from the second start node.
+ * When we are looking for one specific target (optionally multiple tiles), we
+ * should use a good heuristic to perform aystar search. When we search for
+ * multiple targets that are spread around, we should perform a breadth first
+ * search by specifiying CalcZero as our heuristic.
+ */
+static NPFFoundTargetData NPFRouteInternal(AyStarNode *start1, bool ignore_start_tile1, AyStarNode *start2, bool ignore_start_tile2, NPFFindStationOrTileData *target, AyStar_EndNodeCheck target_proc, AyStar_CalculateH heuristic_proc, TransportType type, uint sub_type, Owner owner, RailTypes railtypes, uint reverse_penalty)
+{
+	int r;
+	NPFFoundTargetData result;
+
+	/* Initialize procs */
+	_npf_aystar.CalculateH = heuristic_proc;
+	_npf_aystar.EndNodeCheck = target_proc;
+	_npf_aystar.FoundEndNode = NPFSaveTargetData;
+	_npf_aystar.GetNeighbours = NPFFollowTrack;
+	switch (type) {
+		default: NOT_REACHED();
+		case TRANSPORT_RAIL:  _npf_aystar.CalculateG = NPFRailPathCost;  break;
+		case TRANSPORT_ROAD:  _npf_aystar.CalculateG = NPFRoadPathCost;  break;
+		case TRANSPORT_WATER: _npf_aystar.CalculateG = NPFWaterPathCost; break;
+	}
+
+	/* Initialize Start Node(s) */
+	start1->user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+	start1->user_data[NPF_NODE_FLAGS] = 0;
+	NPFSetFlag(start1, NPF_FLAG_IGNORE_START_TILE, ignore_start_tile1);
+	_npf_aystar.addstart(&_npf_aystar, start1, 0);
+	if (start2) {
+		start2->user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+		start2->user_data[NPF_NODE_FLAGS] = 0;
+		NPFSetFlag(start2, NPF_FLAG_IGNORE_START_TILE, ignore_start_tile2);
+		NPFSetFlag(start2, NPF_FLAG_REVERSE, true);
+		_npf_aystar.addstart(&_npf_aystar, start2, reverse_penalty);
+	}
+
+	/* Initialize result */
+	result.best_bird_dist = UINT_MAX;
+	result.best_path_dist = UINT_MAX;
+	result.best_trackdir  = INVALID_TRACKDIR;
+	result.node.tile      = INVALID_TILE;
+	result.res_okay       = false;
+	_npf_aystar.user_path = &result;
+
+	/* Initialize target */
+	_npf_aystar.user_target = target;
+
+	/* Initialize user_data */
+	_npf_aystar.user_data[NPF_TYPE] = type;
+	_npf_aystar.user_data[NPF_SUB_TYPE] = sub_type;
+	_npf_aystar.user_data[NPF_OWNER] = owner;
+	_npf_aystar.user_data[NPF_RAILTYPES] = railtypes;
+
+	/* GO! */
+	r = AyStarMain_Main(&_npf_aystar);
+	assert(r != AYSTAR_STILL_BUSY);
+
+	if (result.best_bird_dist != 0) {
+		if (target != NULL) {
+			DEBUG(npf, 1, "Could not find route to tile 0x%X from 0x%X.", target->dest_coords, start1->tile);
+		} else {
+			/* Assumption: target == NULL, so we are looking for a depot */
+			DEBUG(npf, 1, "Could not find route to a depot from tile 0x%X.", start1->tile);
+		}
+
+	}
+	return result;
+}
+
+NPFFoundTargetData NPFRouteToStationOrTileTwoWay(TileIndex tile1, Trackdir trackdir1, bool ignore_start_tile1, TileIndex tile2, Trackdir trackdir2, bool ignore_start_tile2, NPFFindStationOrTileData *target, TransportType type, uint sub_type, Owner owner, RailTypes railtypes)
+{
+	AyStarNode start1;
+	AyStarNode start2;
+
+	start1.tile = tile1;
+	start2.tile = tile2;
+	/* We set this in case the target is also the start tile, we will just
+	 * return a not found then */
+	start1.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+	start1.direction = trackdir1;
+	start2.direction = trackdir2;
+	start2.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+
+	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : NULL), ignore_start_tile2, target, NPFFindStationOrTile, NPFCalcStationOrTileHeuristic, type, sub_type, owner, railtypes, 0);
+}
+
+NPFFoundTargetData NPFRouteToStationOrTile(TileIndex tile, Trackdir trackdir, bool ignore_start_tile, NPFFindStationOrTileData *target, TransportType type, uint sub_type, Owner owner, RailTypes railtypes)
+{
+	return NPFRouteToStationOrTileTwoWay(tile, trackdir, ignore_start_tile, INVALID_TILE, INVALID_TRACKDIR, false, target, type, sub_type, owner, railtypes);
+}
+
+NPFFoundTargetData NPFRouteToDepotBreadthFirstTwoWay(TileIndex tile1, Trackdir trackdir1, bool ignore_start_tile1, TileIndex tile2, Trackdir trackdir2, bool ignore_start_tile2, TransportType type, uint sub_type, Owner owner, RailTypes railtypes, uint reverse_penalty)
+{
+	AyStarNode start1;
+	AyStarNode start2;
+
+	start1.tile = tile1;
+	start2.tile = tile2;
+	/* We set this in case the target is also the start tile, we will just
+	 * return a not found then */
+	start1.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+	start1.direction = trackdir1;
+	start2.direction = trackdir2;
+	start2.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+
+	/* perform a breadth first search. Target is NULL,
+	 * since we are just looking for any depot...*/
+	return NPFRouteInternal(&start1, ignore_start_tile1, (IsValidTile(tile2) ? &start2 : NULL), ignore_start_tile2, NULL, NPFFindDepot, NPFCalcZero, type, sub_type, owner, railtypes, reverse_penalty);
+}
+
+NPFFoundTargetData NPFRouteToDepotBreadthFirst(TileIndex tile, Trackdir trackdir, bool ignore_start_tile, TransportType type, uint sub_type, Owner owner, RailTypes railtypes)
+{
+	return NPFRouteToDepotBreadthFirstTwoWay(tile, trackdir, ignore_start_tile, INVALID_TILE, INVALID_TRACKDIR, false, type, sub_type, owner, railtypes, 0);
+}
+
+NPFFoundTargetData NPFRouteToDepotTrialError(TileIndex tile, Trackdir trackdir, bool ignore_start_tile, TransportType type, uint sub_type, Owner owner, RailTypes railtypes)
+{
+	/* Okay, what we're gonna do. First, we look at all depots, calculate
+	 * the manhatten distance to get to each depot. We then sort them by
+	 * distance. We start by trying to plan a route to the closest, then
+	 * the next closest, etc. We stop when the best route we have found so
+	 * far, is shorter than the manhattan distance. This will obviously
+	 * always find the closest depot. It will probably be most efficient
+	 * for ships, since the heuristic will not be to far off then. I hope.
+	 */
+	Queue depots;
+	int r;
+	NPFFoundTargetData best_result = {UINT_MAX, UINT_MAX, INVALID_TRACKDIR, {INVALID_TILE, INVALID_TRACKDIR, {0, 0}}, false};
+	NPFFoundTargetData result;
+	NPFFindStationOrTileData target;
+	AyStarNode start;
+	Depot *current;
+	Depot *depot;
+
+	init_InsSort(&depots);
+	/* Okay, let's find all depots that we can use first */
+	FOR_ALL_DEPOTS(depot) {
+		/* Check if this is really a valid depot, it is of the needed type and
+		 * owner */
+		if (IsDepotTypeTile(depot->xy, type) && IsTileOwner(depot->xy, owner))
+			/* If so, let's add it to the queue, sorted by distance */
+			depots.push(&depots, depot, DistanceManhattan(tile, depot->xy));
+	}
+
+	/* Now, let's initialise the aystar */
+
+	/* Initialize procs */
+	_npf_aystar.CalculateH = NPFCalcStationOrTileHeuristic;
+	_npf_aystar.EndNodeCheck = NPFFindStationOrTile;
+	_npf_aystar.FoundEndNode = NPFSaveTargetData;
+	_npf_aystar.GetNeighbours = NPFFollowTrack;
+	switch (type) {
+		default: NOT_REACHED();
+		case TRANSPORT_RAIL:  _npf_aystar.CalculateG = NPFRailPathCost;  break;
+		case TRANSPORT_ROAD:  _npf_aystar.CalculateG = NPFRoadPathCost;  break;
+		case TRANSPORT_WATER: _npf_aystar.CalculateG = NPFWaterPathCost; break;
+	}
+
+	/* Initialize target */
+	target.station_index = INVALID_STATION; // We will initialize dest_coords inside the loop below
+	_npf_aystar.user_target = &target;
+
+	/* Initialize user_data */
+	_npf_aystar.user_data[NPF_TYPE] = type;
+	_npf_aystar.user_data[NPF_SUB_TYPE] = sub_type;
+	_npf_aystar.user_data[NPF_OWNER] = owner;
+
+	/* Initialize Start Node */
+	start.tile = tile;
+	start.direction = trackdir; // We will initialize user_data inside the loop below
+
+	/* Initialize Result */
+	_npf_aystar.user_path = &result;
+	best_result.best_path_dist = UINT_MAX;
+	best_result.best_bird_dist = UINT_MAX;
+
+	/* Just iterate the depots in order of increasing distance */
+	while ((current = (Depot*)depots.pop(&depots))) {
+		/* Check to see if we already have a path shorter than this
+		 * depot's manhattan distance. HACK: We call DistanceManhattan
+		 * again, we should probably modify the queue to give us that
+		 * value... */
+		if ( DistanceManhattan(tile, current->xy * NPF_TILE_LENGTH) > best_result.best_path_dist)
+			break;
+
+		/* Initialize Start Node
+		 * We set this in case the target is also the start tile, we will just
+		 * return a not found then */
+		start.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+		start.user_data[NPF_NODE_FLAGS] = 0;
+		NPFSetFlag(&start, NPF_FLAG_IGNORE_START_TILE, ignore_start_tile);
+		_npf_aystar.addstart(&_npf_aystar, &start, 0);
+
+		/* Initialize result */
+		result.best_bird_dist = UINT_MAX;
+		result.best_path_dist = UINT_MAX;
+		result.best_trackdir = INVALID_TRACKDIR;
+
+		/* Initialize target */
+		target.dest_coords = current->xy;
+
+		/* GO! */
+		r = AyStarMain_Main(&_npf_aystar);
+		assert(r != AYSTAR_STILL_BUSY);
+
+		/* This depot is closer */
+		if (result.best_path_dist < best_result.best_path_dist)
+			best_result = result;
+	}
+	if (result.best_bird_dist != 0) {
+		DEBUG(npf, 1, "Could not find route to any depot from tile 0x%X.", tile);
+	}
+	return best_result;
+}
+
+NPFFoundTargetData NPFRouteToSafeTile(const Train *v, TileIndex tile, Trackdir trackdir, bool override_railtype)
+{
+	assert(v->type == VEH_TRAIN);
+
+	NPFFindStationOrTileData fstd;
+	fstd.v = v;
+	fstd.reserve_path = true;
+
+	AyStarNode start1;
+	start1.tile = tile;
+	/* We set this in case the target is also the start tile, we will just
+	 * return a not found then */
+	start1.user_data[NPF_TRACKDIR_CHOICE] = INVALID_TRACKDIR;
+	start1.direction = trackdir;
+	NPFSetFlag(&start1, NPF_FLAG_IGNORE_RESERVED, true);
+
+	RailTypes railtypes = v->compatible_railtypes;
+	if (override_railtype) railtypes |= GetRailTypeInfo(v->railtype)->compatible_railtypes;
+
+	/* perform a breadth first search. Target is NULL,
+	 * since we are just looking for any safe tile...*/
+	return NPFRouteInternal(&start1, true, NULL, false, &fstd, NPFFindSafeTile, NPFCalcZero, TRANSPORT_RAIL, 0, v->owner, railtypes, 0);
+}
+
+void InitializeNPF()
+{
+	static bool first_init = true;
+	if (first_init) {
+		first_init = false;
+		init_AyStar(&_npf_aystar, NPFHash, NPF_HASH_SIZE);
+	} else {
+		AyStarMain_Clear(&_npf_aystar);
+	}
+	_npf_aystar.loops_per_tick = 0;
+	_npf_aystar.max_path_cost = 0;
+	//_npf_aystar.max_search_nodes = 0;
+	/* We will limit the number of nodes for now, until we have a better
+	 * solution to really fix performance */
+	_npf_aystar.max_search_nodes = _settings_game.pf.npf.npf_max_search_nodes;
+}
+
+void NPFFillWithOrderData(NPFFindStationOrTileData *fstd, Vehicle *v, bool reserve_path)
+{
+	/* Ships don't really reach their stations, but the tile in front. So don't
+	 * save the station id for ships. For roadvehs we don't store it either,
+	 * because multistop depends on vehicles actually reaching the exact
+	 * dest_tile, not just any stop of that station.
+	 * So only for train orders to stations we fill fstd->station_index, for all
+	 * others only dest_coords */
+	if (v->type == VEH_TRAIN && (v->current_order.IsType(OT_GOTO_STATION) || v->current_order.IsType(OT_GOTO_WAYPOINT))) {
+		fstd->station_index = v->current_order.GetDestination();
+		/* Let's take the closest tile of the station as our target for trains */
+		fstd->dest_coords = CalcClosestStationTile(fstd->station_index, v->tile);
+	} else {
+		fstd->dest_coords = v->dest_tile;
+		fstd->station_index = INVALID_STATION;
+	}
+	fstd->reserve_path = reserve_path;
+	fstd->v = v;
+}