diff --git a/aystar.h b/aystar.h
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+/*
+ * This file has the header for AyStar
+ *  AyStar is a fast pathfinding routine and is used for things like
+ *  AI_pathfinding and Train_pathfinding.
+ *  For more information about AyStar (A* Algorithm), you can look at
+ *	  http://en.wikipedia.org/wiki/A-star_search_algorithm
+ */
+
+#ifndef AYSTAR_H
+#define AYSTAR_H
+
+#include "queue.h"
+
+//#define AYSTAR_DEBUG
+enum {
+	AYSTAR_FOUND_END_NODE,
+	AYSTAR_EMPTY_OPENLIST,
+	AYSTAR_STILL_BUSY,
+	AYSTAR_NO_PATH,
+	AYSTAR_LIMIT_REACHED,
+	AYSTAR_DONE
+};
+
+enum{
+	AYSTAR_INVALID_NODE = -1,
+};
+
+typedef struct AyStarNode AyStarNode;
+struct AyStarNode {
+	uint tile;
+	uint direction;
+	uint user_data[2];
+};
+
+// The resulting path has nodes looking like this.
+typedef struct PathNode PathNode;
+struct PathNode {
+	AyStarNode node;
+	// The parent of this item
+	PathNode *parent;
+};
+
+// For internal use only
+// We do not save the h-value, because it is only needed to calculate the f-value.
+//  h-value should _always_ be the distance left to the end-tile.
+typedef struct OpenListNode OpenListNode;
+struct OpenListNode {
+	int g;
+	PathNode path;
+};
+
+typedef struct AyStar AyStar;
+/*
+ * This function is called to check if the end-tile is found
+ *  return values can be:
+ *	AYSTAR_FOUND_END_NODE : indicates this is the end tile
+ *	AYSTAR_DONE : indicates this is not the end tile (or direction was wrong)
+ */
+typedef int32 AyStar_EndNodeCheck(AyStar *aystar, OpenListNode *current);
+
+/*
+ * This function is called to calculate the G-value for AyStar Algorithm.
+ *  return values can be:
+ *	AYSTAR_INVALID_NODE : indicates an item is not valid (e.g.: unwalkable)
+ *	Any value >= 0 : the g-value for this tile
+ */
+typedef int32 AyStar_CalculateG(AyStar *aystar, AyStarNode *current, OpenListNode *parent);
+
+/*
+ * This function is called to calculate the H-value for AyStar Algorithm.
+ *  Mostly, this must result the distance (Manhattan way) between the
+ *   current point and the end point
+ *  return values can be:
+ *	Any value >= 0 : the h-value for this tile
+ */
+typedef int32 AyStar_CalculateH(AyStar *aystar, AyStarNode *current, OpenListNode *parent);
+
+/*
+ * This function request the tiles around the current tile and put them in tiles_around
+ *  tiles_around is never resetted, so if you are not using directions, just leave it alone.
+ * Warning: never add more tiles_around than memory allocated for it.
+ */
+typedef void AyStar_GetNeighbours(AyStar *aystar, OpenListNode *current);
+
+/*
+ * If the End Node is found, this function is called.
+ *  It can do, for example, calculate the route and put that in an array
+ */
+typedef void AyStar_FoundEndNode(AyStar *aystar, OpenListNode *current);
+
+// For internal use, see aystar.c
+typedef void AyStar_AddStartNode(AyStar *aystar, AyStarNode* start_node);
+typedef int AyStar_Main(AyStar *aystar);
+typedef int AyStar_Loop(AyStar *aystar);
+typedef int AyStar_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent);
+typedef void AyStar_Free(AyStar *aystar);
+typedef void AyStar_Clear(AyStar *aystar);
+
+struct AyStar {
+/* These fields should be filled before initting the AyStar, but not changed
+ * afterwards (except for user_data and user_path)! (free and init again to change them) */
+
+	/* These should point to the application specific routines that do the
+	 * actual work */
+	AyStar_CalculateG* CalculateG;
+	AyStar_CalculateH* CalculateH;
+	AyStar_GetNeighbours* GetNeighbours;
+	AyStar_EndNodeCheck* EndNodeCheck;
+	AyStar_FoundEndNode* FoundEndNode;
+	
+	/* These are completely untouched by AyStar, they can be accesed by
+	 * the application specific routines to input and output data.
+	 * user_path should typically contain data about the resulting path
+	 * afterwards, user_target should typically contain information about
+	 * what where looking for, and user_data can contain just about
+	 * everything */
+	void *user_path;
+	void *user_target;
+	uint user_data[10];
+	
+	/* How many loops are there called before AyStarMain_Main gives
+	 * control back to the caller. 0 = until done */
+	byte loops_per_tick;
+	/* If the g-value goes over this number, it stops searching
+	 *  0 = infinite */
+	uint max_path_cost;
+	/* The maximum amount of nodes that will be expanded, 0 = infinite */
+	uint max_search_nodes; 
+
+	/* These should be filled with the neighbours of a tile by
+	 * GetNeighbours */
+	AyStarNode neighbours[12];
+	byte num_neighbours;
+
+	/* These will contain the methods for manipulating the AyStar. Only
+	 * main() should be called externally */
+	AyStar_AddStartNode* addstart;
+	AyStar_Main* main;
+	AyStar_Loop* loop;
+	AyStar_Free* free;
+	AyStar_Clear* clear;
+	AyStar_CheckTile* checktile;
+	
+	/* These will contain the open and closed lists */
+
+	/* The actual closed list */
+	Hash ClosedListHash;
+	/* The open queue */
+	Queue OpenListQueue;
+	/* An extra hash to speed up the process of looking up an element in
+	 * the open list */
+	Hash OpenListHash;
+};
+
+
+void AyStarMain_AddStartNode(AyStar *aystar, AyStarNode *start_node);
+int AyStarMain_Main(AyStar *aystar);
+int AyStarMain_Loop(AyStar *aystar);
+int AyStarMain_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent);
+void AyStarMain_Free(AyStar *aystar);
+void AyStarMain_Clear(AyStar *aystar);
+
+/* Initialize an AyStar. You should fill all appropriate fields before
+ * callling init_AyStar (see the declaration of AyStar for which fields are
+ * internal */
+void init_AyStar(AyStar* aystar, Hash_HashProc hash, uint num_buckets);
+	
+
+#endif