Codechange: Add RailStationTileLayout iterator. (#14510)

This allows iterating a predefined or calculated rail station layout without allocating extra memory and copying.

src/CMakeLists.txt

@@ -462,6 +462,7 @@ add_files(
     station_gui.cpp
     station_gui.h
     station_kdtree.h
+    station_layout_type.h
     station_map.h
     station_type.h
     statusbar_gui.cpp

src/station_cmd.cpp

@@ -68,6 +68,7 @@
 #include "timer/timer_game_tick.h"
 #include "cheat_type.h"
 #include "road_func.h"
+#include "station_layout_type.h"
 
 #include "widgets/station_widget.h"
 
@@ -1094,54 +1095,37 @@ CommandCost CanExpandRailStation(const BaseStation *st, TileArea &new_ta)
 	return CommandCost();
 }
 
-static inline uint8_t *CreateSingle(uint8_t *layout, int n)
+RailStationTileLayout::RailStationTileLayout(const StationSpec *spec, uint8_t platforms, uint8_t length) : platforms(platforms), length(length)
 {
-	int i = n;
-	do *layout++ = 0; while (--i);
-	layout[((n - 1) >> 1) - n] = 2;
-	return layout;
+	if (spec == nullptr) return;
+
+	/* Look for a predefined layout for the required size. */
+	auto found = spec->layouts.find(GetStationLayoutKey(platforms, length));
+	if (found != std::end(spec->layouts)) this->layout = found->second;
 }
 
-static inline uint8_t *CreateMulti(uint8_t *layout, int n, uint8_t b)
+StationGfx RailStationTileLayout::Iterator::operator*() const
 {
-	int i = n;
-	do *layout++ = b; while (--i);
-	if (n > 4) {
-		layout[0 - n] = 0;
-		layout[n - 1 - n] = 0;
-	}
-	return layout;
-}
+	/* Use predefined layout if it exists. Mask bit zero which will indicate axis. */
+	if (!stl.layout.empty()) return this->stl.layout[this->position] & ~1;
 
-/**
- * Create the station layout for the given number of tracks and platform length.
- * @param layout    The layout to write to.
- * @param numtracks The number of tracks to write.
- * @param plat_len  The length of the platforms.
- * @param statspec  The specification of the station to (possibly) get the layout from.
- */
-void GetStationLayout(uint8_t *layout, uint numtracks, uint plat_len, const StationSpec *statspec)
-{
-	if (statspec != nullptr) {
-		auto found = statspec->layouts.find(GetStationLayoutKey(numtracks, plat_len));
-		if (found != std::end(statspec->layouts)) {
-			/* Custom layout defined, copy to buffer. */
-			std::copy(std::begin(found->second), std::end(found->second), layout);
-			return;
-		}
+	if (this->stl.length == 1) {
+		/* Special case for 1-long platforms, all bare platforms except one small building. */
+		return this->position == ((this->stl.platforms - 1) / 2) ? 2 : 0;
 	}
 
-	if (plat_len == 1) {
-		CreateSingle(layout, numtracks);
-	} else {
-		if (numtracks & 1) layout = CreateSingle(layout, plat_len);
-		int n = numtracks >> 1;
-
-		while (--n >= 0) {
-			layout = CreateMulti(layout, plat_len, 4);
-			layout = CreateMulti(layout, plat_len, 6);
-		}
+	if ((this->position < this->stl.length && (this->stl.platforms % 2 == 1))) {
+		/* Number of tracks is odd, make the first platform bare with a small building. */
+		return this->position == ((this->stl.length - 1) / 2) ? 2 : 0;
 	}
+
+	if (this->stl.length > 4 && ((this->position % this->stl.length) == 0 || (this->position % this->stl.length) == this->stl.length - 1)) {
+		/* Station is longer than 4 tiles, place bare platforms at either end. */
+		return 0;
+	}
+
+	/* None of the above so must be north or south part of larger station. */
+	return ((this->position / this->stl.length) & (this->stl.platforms % 2)) ? 4 : 6;
 }
 
 /**
@@ -1427,19 +1411,17 @@ CommandCost CmdBuildRailStation(DoCommandFlags flags, TileIndex tile_org, RailTy
 		TileIndexDiff track_delta = TileOffsByAxis(OtherAxis(axis)); // offset to go to the next track
 		Track track = AxisToTrack(axis);
 
-		std::vector<uint8_t> layouts(numtracks * plat_len);
-		GetStationLayout(layouts.data(), numtracks, plat_len, statspec);
+		RailStationTileLayout stl{statspec, numtracks, plat_len};
+		auto it = stl.begin();
 
 		uint8_t numtracks_orig = numtracks;
 
 		Company *c = Company::Get(st->owner);
-		size_t layout_idx = 0;
 		TileIndex tile_track = tile_org;
 		do {
 			TileIndex tile = tile_track;
 			int w = plat_len;
 			do {
-				uint8_t layout = layouts[layout_idx++];
 				if (IsRailStationTile(tile) && HasStationReservation(tile)) {
 					/* Check for trains having a reservation for this tile. */
 					Train *v = GetTrainForReservation(tile, AxisToTrack(GetRailStationAxis(tile)));
@@ -1458,7 +1440,8 @@ CommandCost CmdBuildRailStation(DoCommandFlags flags, TileIndex tile_org, RailTy
 				/* Remove animation if overbuilding */
 				DeleteAnimatedTile(tile);
 				uint8_t old_specindex = HasStationTileRail(tile) ? GetCustomStationSpecIndex(tile) : 0;
-				MakeRailStation(tile, st->owner, st->index, axis, layout & ~1, rt);
+
+				MakeRailStation(tile, st->owner, st->index, axis, *it++, rt);
 				/* Free the spec if we overbuild something */
 				DeallocateSpecFromStation(st, old_specindex);
 

src/station_layout_type.h

@@ -0,0 +1,59 @@
+/*
+ * 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 station_layout_type.h Functions related to station layouts. */
+
+#ifndef STATION_LAYOUT_TYPE_H
+#define STATION_LAYOUT_TYPE_H
+
+#include "newgrf_station.h"
+#include "station_map.h"
+
+class RailStationTileLayout {
+private:
+	std::span<const StationGfx> layout{}; ///< Predefined tile layout.
+	uint platforms; ///< Number of platforms.
+	uint length; ///< Length of platforms.
+public:
+	RailStationTileLayout(const StationSpec *spec, uint8_t platforms, uint8_t length);
+
+	class Iterator {
+		const RailStationTileLayout &stl; ///< Station tile layout being iterated.
+		uint position = 0; ///< Position within iterator.
+	public:
+		using value_type = StationGfx;
+		using difference_type = std::ptrdiff_t;
+		using iterator_category = std::forward_iterator_tag;
+		using pointer = void;
+		using reference = void;
+
+		Iterator(const RailStationTileLayout &stl) : stl(stl) {}
+
+		bool operator==(const Iterator &rhs) const { return this->position == rhs.position; }
+		bool operator==(const std::default_sentinel_t &) const { return this->position == this->stl.platforms * this->stl.length; }
+
+		StationGfx operator*() const;
+
+		Iterator &operator++()
+		{
+			++this->position;
+			return *this;
+		}
+
+		Iterator operator++(int)
+		{
+			Iterator result = *this;
+			++*this;
+			return result;
+		}
+	};
+
+	Iterator begin() const { return Iterator(*this); }
+	std::default_sentinel_t end() const { return std::default_sentinel_t(); }
+};
+
+#endif /* STATION_LAYOUT_TYPE_H */

src/waypoint_cmd.cpp

@@ -31,6 +31,7 @@
 #include "company_gui.h"
 #include "waypoint_cmd.h"
 #include "landscape_cmd.h"
+#include "station_layout_type.h"
 
 #include "table/strings.h"
 
@@ -179,7 +180,6 @@ static CommandCost IsValidTileForWaypoint(TileIndex tile, Axis axis, StationID *
 	return CommandCost();
 }
 
-extern void GetStationLayout(uint8_t *layout, uint numtracks, uint plat_len, const StationSpec *statspec);
 extern CommandCost FindJoiningWaypoint(StationID existing_station, StationID station_to_join, bool adjacent, TileArea ta, Waypoint **wp, bool is_road);
 extern CommandCost CanExpandRailStation(const BaseStation *st, TileArea &new_ta);
 extern CommandCost CalculateRoadStopCost(TileArea tile_area, DoCommandFlags flags, bool is_drive_through, StationType station_type, Axis axis, DiagDirection ddir, StationID *est, RoadType rt, Money unit_cost);
@@ -286,13 +286,11 @@ CommandCost CmdBuildRailWaypoint(DoCommandFlags flags, TileIndex start_tile, Axi
 		wp->UpdateVirtCoord();
 
 		const StationSpec *spec = StationClass::Get(spec_class)->GetSpec(spec_index);
-		std::vector<uint8_t> layout(count);
-		if (spec != nullptr) {
-			/* For NewGRF waypoints we like to have their style. */
-			GetStationLayout(layout.data(), count, 1, spec);
-		}
 		uint8_t map_spec_index = AllocateSpecToStation(spec, wp, true);
 
+		RailStationTileLayout stl{spec, count, 1};
+		auto it = stl.begin();
+
 		Company *c = Company::Get(wp->owner);
 		for (int i = 0; i < count; i++) {
 			TileIndex tile = start_tile + i * offset;
@@ -301,7 +299,7 @@ CommandCost CmdBuildRailWaypoint(DoCommandFlags flags, TileIndex start_tile, Axi
 			bool reserved = IsTileType(tile, MP_RAILWAY) ?
 					HasBit(GetRailReservationTrackBits(tile), AxisToTrack(axis)) :
 					HasStationReservation(tile);
-			MakeRailWaypoint(tile, wp->owner, wp->index, axis, layout[i], GetRailType(tile));
+			MakeRailWaypoint(tile, wp->owner, wp->index, axis, *it++, GetRailType(tile));
 			SetCustomStationSpecIndex(tile, map_spec_index);
 
 			SetRailStationTileFlags(tile, spec);