# HG changeset patch
# User celestar <celestar@openttd.org>
# Date 2007-03-24 09:12:03
# Node ID b0a38d4167ad5d53fe1197aa30ea88b979e11155
# Parent  1e9e4464ad4cdc08612c4e3bc011be05e912f353

(svn r9425) -Codechange/Fix (FS#689): Housekeeping in the convert rail functions: Changed the order of error checks to generate more meaningful error messages, added some doxygen comments and replaced bitshifting by proper mathematical operations

diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -849,14 +849,23 @@ int32 CmdRemoveSignalTrack(TileIndex til
 
 typedef int32 DoConvertRailProc(TileIndex tile, RailType totype, bool exec);
 
+/**
+ * Switches the rail type.
+ * Railtypes are stored on a per-tile basis, not on a per-track basis, so
+ * all the tracks in the given tile will be converted.
+ * @param tile        The tile on which the railtype is to be convert.
+ * @param totype      The railtype we want to convert to
+ * @param exec        Switches between test and execute mode
+ * @return            The cost and state of the operation
+ * @retval CMD_ERROR  An error occured during the operation.
+ */
 static int32 DoConvertRail(TileIndex tile, RailType totype, bool exec)
 {
 	if (!CheckTileOwnership(tile)) return CMD_ERROR;
 
-	if (!EnsureNoVehicle(tile) && (!IsCompatibleRail(GetRailType(tile), totype) || IsPlainRailTile(tile))) return CMD_ERROR;
+	if (GetRailType(tile) == totype) return CMD_ERROR;
 
-	// tile is already of requested type?
-	if (GetRailType(tile) == totype) return CMD_ERROR;
+	if (!EnsureNoVehicle(tile) && (!IsCompatibleRail(GetRailType(tile), totype) || IsPlainRailTile(tile))) return CMD_ERROR;
 
 	// 'hidden' elrails can't be downgraded to normal rail when elrails are disabled
 	if (_patches.disable_elrails && totype == RAILTYPE_RAIL && GetRailType(tile) == RAILTYPE_ELECTRIC) return CMD_ERROR;
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -367,6 +367,14 @@ do_clear:;
 	return cost;
 }
 
+/**
+ * Switches the rail type on a level crossing.
+ * @param tile        The tile on which the railtype is to be convert.
+ * @param totype      The railtype we want to convert to
+ * @param exec        Switches between test and execute mode
+ * @return            The cost and state of the operation
+ * @retval CMD_ERROR  An error occured during the operation.
+ */
 int32 DoConvertStreetRail(TileIndex tile, RailType totype, bool exec)
 {
 	// not a railroad crossing?
@@ -386,7 +394,7 @@ int32 DoConvertStreetRail(TileIndex tile
 		YapfNotifyTrackLayoutChange(tile, FindFirstTrack(GetCrossingRailBits(tile)));
 	}
 
-	return _price.build_rail >> 1;
+	return _price.build_rail / 2;
 }
 
 
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -1120,6 +1120,14 @@ static int32 RemoveRailroadStation(Stati
 	return cost;
 }
 
+/**
+ * Switches the rail type at a railway station tile.
+ * @param tile        The tile on which the railtype is to be convert.
+ * @param totype      The railtype we want to convert to
+ * @param exec        Switches between test and execute mode
+ * @return            The cost and state of the operation
+ * @retval CMD_ERROR  An error occured during the operation.
+ */
 int32 DoConvertStationRail(TileIndex tile, RailType totype, bool exec)
 {
 	const Station* st = GetStationByTile(tile);
@@ -1140,7 +1148,7 @@ int32 DoConvertStationRail(TileIndex til
 		YapfNotifyTrackLayoutChange(tile, GetRailStationTrack(tile));
 	}
 
-	return _price.build_rail >> 1;
+	return _price.build_rail / 2;
 }
 
 /**
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -696,6 +696,16 @@ static int32 ClearTile_TunnelBridge(Tile
 	return CMD_ERROR;
 }
 
+/**
+ * Switches the rail type for a tunnel or a bridgehead. As the railtype
+ * on the bridge are determined by the one of the bridgehead, this
+ * functions converts the railtype on the entire bridge.
+ * @param tile        The tile on which the railtype is to be convert.
+ * @param totype      The railtype we want to convert to
+ * @param exec        Switches between test and execute mode
+ * @return            The cost and state of the operation
+ * @retval CMD_ERROR  An error occured during the operation.
+ */
 int32 DoConvertTunnelBridgeRail(TileIndex tile, RailType totype, bool exec)
 {
 	TileIndex endtile;
@@ -724,7 +734,7 @@ int32 DoConvertTunnelBridgeRail(TileInde
 			YapfNotifyTrackLayoutChange(tile, track);
 			YapfNotifyTrackLayoutChange(endtile, track);
 		}
-		return (length + 1) * (_price.build_rail >> 1);
+		return (length + 1) * (_price.build_rail / 2);
 	} else if (IsBridge(tile) && GetBridgeTransportType(tile) == TRANSPORT_RAIL) {
 
 		if (!CheckTileOwnership(tile)) return CMD_ERROR;
@@ -758,7 +768,7 @@ int32 DoConvertTunnelBridgeRail(TileInde
 			}
 		}
 
-		return (DistanceManhattan(tile, endtile) + 1) * (_price.build_rail >> 1);
+		return (DistanceManhattan(tile, endtile) + 1) * (_price.build_rail / 2);
 	} else {
 		return CMD_ERROR;
 	}