new file mode 100644
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+++ b/src/map_func.h
@@ -0,0 +1,389 @@
+/* $Id$ */
+
+/** @file map.h */
+
+#ifndef MAP_FUNC_H
+#define MAP_FUNC_H
+
+#include "tile_type.h"
+#include "map_type.h"
+#include "direction_func.h"
+
+extern uint _map_tile_mask;
+
+/**
+ * 'Wraps' the given tile to it is within the map. It does
+ * this by masking the 'high' bits of.
+ * @param x the tile to 'wrap'
+ */
+
+#define TILE_MASK(x) ((x) & _map_tile_mask)
+/**
+ * Asserts when the tile is outside of the map.
+ * @param x the tile to check
+ */
+#define TILE_ASSERT(x) assert(TILE_MASK(x) == (x));
+
+/**
+ * Pointer to the tile-array.
+ *
+ * This variable points to the tile-array which contains the tiles of
+ * the map.
+ */
+extern Tile *_m;
+
+/**
+ * Pointer to the extended tile-array.
+ *
+ * This variable points to the extended tile-array which contains the tiles
+ * of the map.
+ */
+extern TileExtended *_me;
+
+/**
+ * Allocate a new map with the given size.
+ */
+void AllocateMap(uint size_x, uint size_y);
+
+/**
+ * Logarithm of the map size along the X side.
+ * @note try to avoid using this one
+ * @return 2^"return value" == MapSizeX()
+ */
+static inline uint MapLogX()
+{
+	extern uint _map_log_x;
+	return _map_log_x;
+}
+
+/**
+ * Get the size of the map along the X
+ * @return the number of tiles along the X of the map
+ */
+static inline uint MapSizeX()
+{
+	extern uint _map_size_x;
+	return _map_size_x;
+}
+
+/**
+ * Get the size of the map along the Y
+ * @return the number of tiles along the Y of the map
+ */
+static inline uint MapSizeY()
+{
+	extern uint _map_size_y;
+	return _map_size_y;
+}
+
+/**
+ * Get the size of the map
+ * @return the number of tiles of the map
+ */
+static inline uint MapSize()
+{
+	extern uint _map_size;
+	return _map_size;
+}
+
+/**
+ * Gets the maximum X coordinate within the map, including MP_VOID
+ * @return the maximum X coordinate
+ */
+static inline uint MapMaxX()
+{
+	return MapSizeX() - 1;
+}
+
+/**
+ * Gets the maximum X coordinate within the map, including MP_VOID
+ * @return the maximum X coordinate
+ */
+static inline uint MapMaxY()
+{
+	return MapSizeY() - 1;
+}
+
+/**
+ * Scales relative to the number of tiles.
+ */
+uint ScaleByMapSize(uint);
+
+/**
+ * Scale relative to the circumference of the map.
+ */
+uint ScaleByMapSize1D(uint);
+
+/**
+ * An offset value between to tiles.
+ *
+ * This value is used fro the difference between
+ * to tiles. It can be added to a tileindex to get
+ * the resulting tileindex of the start tile applied
+ * with this saved difference.
+ *
+ * @see TileDiffXY(int, int)
+ */
+typedef int32 TileIndexDiff;
+
+/**
+ * Returns the TileIndex of a coordinate.
+ *
+ * @param x The x coordinate of the tile
+ * @param y The y coordinate of the tile
+ * @return The TileIndex calculated by the coordinate
+ */
+static inline TileIndex TileXY(uint x, uint y)
+{
+	return (y * MapSizeX()) + x;
+}
+
+/**
+ * Calculates an offset for the given coordinate(-offset).
+ *
+ * This function calculate an offset value which can be added to an
+ * #TileIndex. The coordinates can be negative.
+ *
+ * @param x The offset in x direction
+ * @param y The offset in y direction
+ * @return The resulting offset value of the given coordinate
+ * @see ToTileIndexDiff(TileIndexDiffC)
+ */
+static inline TileIndexDiff TileDiffXY(int x, int y)
+{
+	/* Multiplication gives much better optimization on MSVC than shifting.
+	 * 0 << shift isn't optimized to 0 properly.
+	 * Typically x and y are constants, and then this doesn't result
+	 * in any actual multiplication in the assembly code.. */
+	return (y * MapSizeX()) + x;
+}
+
+static inline TileIndex TileVirtXY(uint x, uint y)
+{
+	return (y >> 4 << MapLogX()) + (x >> 4);
+}
+
+
+/**
+ * Get the X component of a tile
+ * @param tile the tile to get the X component of
+ * @return the X component
+ */
+static inline uint TileX(TileIndex tile)
+{
+	return tile & MapMaxX();
+}
+
+/**
+ * Get the Y component of a tile
+ * @param tile the tile to get the Y component of
+ * @return the Y component
+ */
+static inline uint TileY(TileIndex tile)
+{
+	return tile >> MapLogX();
+}
+
+/**
+ * Return the offset between to tiles from a TileIndexDiffC struct.
+ *
+ * This function works like #TileDiffXY(int, int) and returns the
+ * difference between two tiles.
+ *
+ * @param tidc The coordinate of the offset as TileIndexDiffC
+ * @return The difference between two tiles.
+ * @see TileDiffXY(int, int)
+ */
+static inline TileIndexDiff ToTileIndexDiff(TileIndexDiffC tidc)
+{
+	return (tidc.y << MapLogX()) + tidc.x;
+}
+
+
+#ifndef _DEBUG
+	/**
+	 * Adds to tiles together.
+	 *
+	 * @param x One tile
+	 * @param y An other tile to add
+	 * @return The resulting tile(index)
+	 */
+	#define TILE_ADD(x,y) ((x) + (y))
+#else
+	extern TileIndex TileAdd(TileIndex tile, TileIndexDiff add,
+		const char *exp, const char *file, int line);
+	#define TILE_ADD(x, y) (TileAdd((x), (y), #x " + " #y, __FILE__, __LINE__))
+#endif
+
+/**
+ * Adds a given offset to a tile.
+ *
+ * @param tile The tile to add an offset on it
+ * @param x The x offset to add to the tile
+ * @param y The y offset to add to the tile
+ */
+#define TILE_ADDXY(tile, x, y) TILE_ADD(tile, TileDiffXY(x, y))
+
+/**
+ * Adds an offset to a tile and check if we are still on the map.
+ */
+uint TileAddWrap(TileIndex tile, int addx, int addy);
+
+/**
+ * Returns the TileIndexDiffC offset from a DiagDirection.
+ *
+ * @param dir The given direction
+ * @return The offset as TileIndexDiffC value
+ */
+static inline TileIndexDiffC TileIndexDiffCByDiagDir(DiagDirection dir)
+{
+	extern const TileIndexDiffC _tileoffs_by_diagdir[DIAGDIR_END];
+
+	assert(IsValidDiagDirection(dir));
+	return _tileoffs_by_diagdir[dir];
+}
+
+/**
+ * Add a TileIndexDiffC to a TileIndex and returns the new one.
+ *
+ * Returns tile + the diff given in diff. If the result tile would end up
+ * outside of the map, INVALID_TILE is returned instead.
+ *
+ * @param tile The base tile to add the offset on
+ * @param diff The offset to add on the tile
+ * @return The resulting TileIndex
+ */
+static inline TileIndex AddTileIndexDiffCWrap(TileIndex tile, TileIndexDiffC diff)
+{
+	int x = TileX(tile) + diff.x;
+	int y = TileY(tile) + diff.y;
+	if (x < 0 || y < 0 || x > (int)MapMaxX() || y > (int)MapMaxY())
+		return INVALID_TILE;
+	else
+		return TileXY(x, y);
+}
+
+/**
+ * Returns the diff between two tiles
+ *
+ * @param tile_a from tile
+ * @param tile_b to tile
+ * @return the difference between tila_a and tile_b
+ */
+static inline TileIndexDiffC TileIndexToTileIndexDiffC(TileIndex tile_a, TileIndex tile_b)
+{
+	TileIndexDiffC difference;
+
+	difference.x = TileX(tile_a) - TileX(tile_b);
+	difference.y = TileY(tile_a) - TileY(tile_b);
+
+	return difference;
+}
+
+/* Functions to calculate distances */
+uint DistanceManhattan(TileIndex, TileIndex); ///< also known as L1-Norm. Is the shortest distance one could go over diagonal tracks (or roads)
+uint DistanceSquare(TileIndex, TileIndex); ///< euclidian- or L2-Norm squared
+uint DistanceMax(TileIndex, TileIndex); ///< also known as L-Infinity-Norm
+uint DistanceMaxPlusManhattan(TileIndex, TileIndex); ///< Max + Manhattan
+uint DistanceFromEdge(TileIndex); ///< shortest distance from any edge of the map
+
+/**
+ * Starts a loop which iterates to a square of tiles
+ *
+ * This macro starts 2 nested loops which iterates over a square of tiles.
+ *
+ * @param var The name of the variable which contains the current tile
+ * @param w The width (x-width) of the square
+ * @param h The heigth (y-width) of the square
+ * @param tile The start tile of the square
+ */
+#define BEGIN_TILE_LOOP(var, w, h, tile)                      \
+	{                                                        \
+		int h_cur = h;                                         \
+		uint var = tile;                                       \
+		do {                                                   \
+			int w_cur = w;                                       \
+			do {
+/**
+ * Ends the square-loop used before
+ *
+ * @see BEGIN_TILE_LOOP
+ */
+#define END_TILE_LOOP(var, w, h, tile)                        \
+			} while (++var, --w_cur != 0);                       \
+		} while (var += TileDiffXY(0, 1) - (w), --h_cur != 0); \
+	}
+/**
+ * Convert a DiagDirection to a TileIndexDiff
+ *
+ * @param dir The DiagDirection
+ * @return The resulting TileIndexDiff
+ * @see TileIndexDiffCByDiagDir
+ */
+static inline TileIndexDiff TileOffsByDiagDir(DiagDirection dir)
+{
+	extern const TileIndexDiffC _tileoffs_by_diagdir[DIAGDIR_END];
+
+	assert(IsValidDiagDirection(dir));
+	return ToTileIndexDiff(_tileoffs_by_diagdir[dir]);
+}
+
+/**
+ * Convert a Direction to a TileIndexDiff.
+ *
+ * @param dir The direction to convert from
+ * @return The resulting TileIndexDiff
+ */
+static inline TileIndexDiff TileOffsByDir(Direction dir)
+{
+	extern const TileIndexDiffC _tileoffs_by_dir[DIR_END];
+
+	assert(IsValidDirection(dir));
+	return ToTileIndexDiff(_tileoffs_by_dir[dir]);
+}
+
+/**
+ * Adds a DiagDir to a tile.
+ *
+ * @param tile The current tile
+ * @param dir The direction in which we want to step
+ * @return the moved tile
+ */
+static inline TileIndex TileAddByDiagDir(TileIndex tile, DiagDirection dir)
+{
+	return TILE_ADD(tile, TileOffsByDiagDir(dir));
+}
+
+/**
+ * A callback function type for searching tiles.
+ *
+ * @param tile The tile to test
+ * @param data additional data for the callback function to use
+ * @return A boolean value, depend on the definition of the function.
+ */
+typedef bool TestTileOnSearchProc(TileIndex tile, uint32 data);
+
+/**
+ * Searches for some cirumstances of a tile around a given tile with a helper function.
+ */
+bool CircularTileSearch(TileIndex tile, uint size, TestTileOnSearchProc proc, uint32 data);
+
+/**
+ * Get a random tile out of a given seed.
+ * @param r the random 'seed'
+ * @return a valid tile
+ */
+static inline TileIndex RandomTileSeed(uint32 r)
+{
+	return TILE_MASK(r);
+}
+
+/**
+ * Get a valid random tile.
+ * @note a define so 'random' gets inserted in the place where it is actually
+ *       called, thus making the random traces more explicit.
+ * @return a valid tile
+ */
+#define RandomTile() RandomTileSeed(Random())
+
+#endif /* MAP_FUNC_H */