(svn r19616) -Codechange: Increase transparency of 'Extract' by passing also the number of used bits.

src/cmd_helper.h

@@ -14,12 +14,13 @@
 
 #include "core/enum_type.hpp"
 
-template<typename T, uint N, typename U> static inline T Extract(U v)
+template<typename T, uint S, uint N, typename U> static inline T Extract(U v)
 {
 	/* Check if there are enough bits in v */
-	assert_tcompile(N + EnumPropsT<T>::num_bits <= sizeof(U) * 8);
-	assert_tcompile(EnumPropsT<T>::end <= (1 << EnumPropsT<T>::num_bits));
-	return (T)GB(v, N, EnumPropsT<T>::num_bits);
+	assert_tcompile(N == EnumPropsT<T>::num_bits);
+	assert_tcompile(S + N <= sizeof(U) * 8);
+	assert_tcompile(EnumPropsT<T>::end <= (1 << N));
+	return (T)GB(v, S, N);
 }
 
 #endif

src/rail_cmd.cpp

@@ -837,7 +837,7 @@ CommandCost CmdBuildTrainDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 
 	Slope tileh = GetTileSlope(tile, NULL);
 
-	DiagDirection dir = Extract<DiagDirection, 0>(p2);
+	DiagDirection dir = Extract<DiagDirection, 0, 2>(p2);
 
 	/* Prohibit construction if
 	 * The tile is non-flat AND

src/road_cmd.cpp

@@ -464,7 +464,7 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		p2 = (town != NULL) ? town->index : (TownID)INVALID_TOWN;
 	}
 
-	RoadBits pieces = Extract<RoadBits, 0>(p1);
+	RoadBits pieces = Extract<RoadBits, 0, 4>(p1);
 
 	/* do not allow building 'zero' road bits, code wouldn't handle it */
 	if (pieces == ROAD_NONE) return CMD_ERROR;
@@ -729,7 +729,7 @@ CommandCost CmdBuildLongRoad(TileIndex start_tile, DoCommandFlag flags, uint32 p
 	RoadType rt = (RoadType)GB(p2, 3, 2);
 	if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;
 
-	Axis axis = Extract<Axis, 2>(p2);
+	Axis axis = Extract<Axis, 2, 1>(p2);
 	/* Only drag in X or Y direction dictated by the direction variable */
 	if (axis == AXIS_X && TileY(start_tile) != TileY(end_tile)) return CMD_ERROR; // x-axis
 	if (axis == AXIS_Y && TileX(start_tile) != TileX(end_tile)) return CMD_ERROR; // y-axis
@@ -821,7 +821,7 @@ CommandCost CmdRemoveLongRoad(TileIndex start_tile, DoCommandFlag flags, uint32
 	RoadType rt = (RoadType)GB(p2, 3, 2);
 	if (!IsValidRoadType(rt)) return CMD_ERROR;
 
-	Axis axis = Extract<Axis, 2>(p2);
+	Axis axis = Extract<Axis, 2, 1>(p2);
 	/* Only drag in X or Y direction dictated by the direction variable */
 	if (axis == AXIS_X && TileY(start_tile) != TileY(end_tile)) return CMD_ERROR; // x-axis
 	if (axis == AXIS_Y && TileX(start_tile) != TileX(end_tile)) return CMD_ERROR; // y-axis
@@ -886,7 +886,7 @@ CommandCost CmdRemoveLongRoad(TileIndex start_tile, DoCommandFlag flags, uint32
  */
 CommandCost CmdBuildRoadDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
-	DiagDirection dir = Extract<DiagDirection, 0>(p1);
+	DiagDirection dir = Extract<DiagDirection, 0, 2>(p1);
 	RoadType rt = (RoadType)GB(p1, 2, 2);
 
 	if (!IsValidRoadType(rt) || !ValParamRoadType(rt)) return CMD_ERROR;

src/station_cmd.cpp

@@ -1096,7 +1096,7 @@ CommandCost CmdBuildRailStation(TileIndex tile_org, DoCommandFlag flags, uint32
 {
 	/* Unpack parameters */
 	RailType rt    = (RailType)GB(p1, 0, 4);
-	Axis axis      = Extract<Axis, 4>(p1);
+	Axis axis      = Extract<Axis, 4, 1>(p1);
 	byte numtracks = GB(p1,  8, 8);
 	byte plat_len  = GB(p1, 16, 8);
 	bool adjacent  = HasBit(p1, 24);

src/water_cmd.cpp

@@ -104,7 +104,7 @@ static void MarkCanalsAndRiversAroundDirty(TileIndex tile)
  */
 CommandCost CmdBuildShipDepot(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
-	Axis axis = Extract<Axis, 0>(p1);
+	Axis axis = Extract<Axis, 0, 1>(p1);
 
 	TileIndex tile2 = tile + (axis == AXIS_X ? TileDiffXY(1, 0) : TileDiffXY(0, 1));