Codechange: Increase readability of track functions and pathfinders.

src/pathfinder/follow_track.hpp

@@ -239,7 +239,7 @@ protected:
 		} else {
 			m_new_td_bits = TrackStatusToTrackdirBits(GetTileTrackStatus(m_new_tile, TT(), IsRoadTT() ? RoadVehicle::From(m_veh)->compatible_roadtypes : 0));
 
-			if (IsTram() && m_new_td_bits == 0) {
+			if (IsTram() && m_new_td_bits == TRACKDIR_BIT_NONE) {
 				/* GetTileTrackStatus() returns 0 for single tram bits.
 				 * As we cannot change it there (easily) without breaking something, change it here */
 				switch (GetSingleTramBit(m_new_tile)) {

src/pathfinder/npf/npf.cpp

@@ -807,7 +807,7 @@ static TrackdirBits GetDriveableTrackdirBits(TileIndex dst_tile, Trackdir src_tr
 {
 	TrackdirBits trackdirbits = TrackStatusToTrackdirBits(GetTileTrackStatus(dst_tile, type, subtype));
 
-	if (trackdirbits == 0 && type == TRANSPORT_ROAD && HasBit(subtype, ROADTYPE_TRAM)) {
+	if (trackdirbits == TRACKDIR_BIT_NONE && 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)) {
@@ -900,7 +900,7 @@ static void NPFFollowTrack(AyStar *aystar, OpenListNode *current)
 
 		trackdirbits = GetDriveableTrackdirBits(dst_tile, src_trackdir, type, subtype);
 
-		if (trackdirbits == 0) {
+		if (trackdirbits == TRACKDIR_BIT_NONE) {
 			/* We cannot enter the next tile. Road vehicles can reverse, others reach dead end */
 			if (type != TRANSPORT_ROAD || HasBit(subtype, ROADTYPE_TRAM)) return;
 
@@ -924,7 +924,7 @@ static void NPFFollowTrack(AyStar *aystar, OpenListNode *current)
 
 	/* Enumerate possible track */
 	uint i = 0;
-	while (trackdirbits != 0) {
+	while (trackdirbits != TRACKDIR_BIT_NONE) {
 		Trackdir dst_trackdir = RemoveFirstTrackdir(&trackdirbits);
 		DEBUG(npf, 5, "Expanded into trackdir: %d, remaining trackdirs: 0x%X", dst_trackdir, trackdirbits);
 

src/pathfinder/opf/opf_ship.cpp

@@ -183,9 +183,14 @@ bad:;
 }
 
 /**
- * returns the track to choose on the next tile, or -1 when it's better to
- * reverse. The tile given is the tile we are about to enter, enterdir is the
- * direction in which we are entering the tile
+ * Finds the best track to choose on the next tile and
+ * returns INVALID_TRACK when it is better to reverse.
+ * @param v The ship.
+ * @param tile The tile we are about to enter.
+ * @param enterdir The direction entering the tile.
+ * @param tracks The tracks available on new tile.
+ * @param[out] path_found Whether a path has been found.
+ * @return Best track on next tile or INVALID_TRACK when better to reverse.
  */
 Track OPFShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks, bool &path_found)
 {
@@ -195,13 +200,15 @@ Track OPFShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir,
 	Track track;
 
 	/* Let's find out how far it would be if we would reverse first */
-	Trackdir trackdir = v->GetVehicleTrackdir();
-	TrackBits b = TrackStatusToTrackBits(GetTileTrackStatus(tile2, TRANSPORT_WATER, 0)) & DiagdirReachesTracks(ReverseDiagDir(enterdir)) & TrackdirBitsToTrackBits(TrackdirToTrackdirBits(trackdir));
-
-	uint distr = UINT_MAX; // distance if we reversed
-	if (b != 0) {
-		distr = FindShipTrack(v, tile2, ReverseDiagDir(enterdir), b, tile, &track);
-		if (distr != UINT_MAX) distr++; // penalty for reversing
+	uint rev_dist = UINT_MAX; // distance if we reverse
+	Track cur_track = TrackdirToTrack(v->GetVehicleTrackdir()); // track on the current tile
+	DiagDirection rev_enterdir = ReverseDiagDir(enterdir);
+	TrackBits rev_tracks = TrackStatusToTrackBits(GetTileTrackStatus(tile2, TRANSPORT_WATER, 0)) &
+			DiagdirReachesTracks(rev_enterdir);
+
+	if ((rev_tracks & TrackToTrackBits(cur_track) != TRACK_BIT_NONE) {
+		rev_dist = FindShipTrack(v, tile2, rev_enterdir, TrackToTrackBits(cur_track), tile, &track);
+		if (rev_dist != UINT_MAX) rev_dist++; // penalty for reversing
 	}
 
 	/* And if we would not reverse? */
@@ -209,6 +216,6 @@ Track OPFShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir,
 
 	/* Due to the way this pathfinder works we cannot determine whether we're lost or not. */
 	path_found = true;
-	if (dist <= distr) return track;
+	if (dist <= rev_dist) return track;
 	return INVALID_TRACK; // We could better reverse
 }

src/pathfinder/yapf/yapf_common.hpp

@@ -142,8 +142,7 @@ public:
 	/** Called by YAPF to detect if node ends in the desired destination */
 	inline bool PfDetectDestination(Node &n)
 	{
-		bool bDest = (n.m_key.m_tile == m_destTile) && ((m_destTrackdirs & TrackdirToTrackdirBits(n.GetTrackdir())) != TRACKDIR_BIT_NONE);
-		return bDest;
+		return (n.m_key.m_tile == m_destTile) && ((m_destTrackdirs & TrackdirToTrackdirBits(n.GetTrackdir())) != TRACKDIR_BIT_NONE);
 	}
 
 	/**

src/pathfinder/yapf/yapf_costrail.hpp

@@ -104,7 +104,7 @@ public:
 		assert(IsValidTrackdir(td2));
 		int cost = 0;
 		if (TrackFollower::Allow90degTurns()
-				&& ((TrackdirToTrackdirBits(td2) & (TrackdirBits)TrackdirCrossesTrackdirs(td1)) != 0)) {
+				&& ((TrackdirToTrackdirBits(td2) & TrackdirCrossesTrackdirs(td1)) != TRACKDIR_BIT_NONE)) {
 			/* 90-deg curve penalty */
 			cost += Yapf().PfGetSettings().rail_curve90_penalty;
 		} else if (td2 != NextTrackdir(td1)) {

src/pathfinder/yapf/yapf_destrail.hpp

@@ -166,16 +166,13 @@ public:
 	/** Called by YAPF to detect if node ends in the desired destination */
 	inline bool PfDetectDestination(TileIndex tile, Trackdir td)
 	{
-		bool bDest;
 		if (m_dest_station_id != INVALID_STATION) {
-			bDest = HasStationTileRail(tile)
+			return HasStationTileRail(tile)
 				&& (GetStationIndex(tile) == m_dest_station_id)
 				&& (GetRailStationTrack(tile) == TrackdirToTrack(td));
-		} else {
-			bDest = (tile == m_destTile)
-				&& ((m_destTrackdirs & TrackdirToTrackdirBits(td)) != TRACKDIR_BIT_NONE);
 		}
-		return bDest;
+
+		return (tile == m_destTile) && ((m_destTrackdirs & TrackdirToTrackdirBits(td)) != TRACKDIR_BIT_NONE);
 	}
 
 	/**

src/pathfinder/yapf/yapf_road.cpp

@@ -185,8 +185,7 @@ public:
 	/** Called by YAPF to detect if node ends in the desired destination */
 	inline bool PfDetectDestination(Node &n)
 	{
-		bool bDest = IsRoadDepotTile(n.m_segment_last_tile);
-		return bDest;
+		return IsRoadDepotTile(n.m_segment_last_tile);
 	}
 
 	inline bool PfDetectDestinationTile(TileIndex tile, Trackdir trackdir)

src/track_func.h

@@ -61,7 +61,7 @@ static inline bool IsValidTrackdirForRoadVehicle(Trackdir trackdir)
  */
 static inline bool IsValidTrackdir(Trackdir trackdir)
 {
-	return (1 << trackdir & TRACKDIR_BIT_MASK) != 0;
+	return (1 << trackdir & TRACKDIR_BIT_MASK) != TRACKDIR_BIT_NONE;
 }
 
 /**