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/* $Id$ */

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/** @file newgrf_commons.h This file simplyfies and embeds a common mechanism of

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 * loading/saving and mapping of grf entities.

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 */

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#ifndef NEWGRF_COMMONS_H

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#define NEWGRF_COMMONS_H

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/**

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 * Maps an entity id stored on the map to a GRF file.

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 * Entities are objects used ingame (houses, industries, industry tiles) for

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 * which we need to correlate the ids from the grf files with the ones in the

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 * the savegames themselves.

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 * An array of EntityIDMapping structs is saved with the savegame so

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 * that those GRFs can be loaded in a different order, or removed safely. The

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 * index in the array is the entity's ID stored on the map.

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 *

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 * The substitute ID is the ID of an original entity that should be used instead

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 * if the GRF containing the new entity is not available.

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 */

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struct EntityIDMapping {

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	uint32 grfid;          ///< The GRF ID of the file the entity belongs to

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	uint8  entity_id;      ///< The entity ID within the GRF file

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	uint8  substitute_id;  ///< The (original) entity ID to use if this GRF is not available

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};

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class OverrideManagerBase

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{

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protected:

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	uint16 *entity_overrides;

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	uint16 max_offset;       ///< what is the length of the original entity's array of specs

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	uint16 max_new_entities; ///< what is the amount of entities, old and new summed

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	uint16 invalid_ID;       ///< ID used to dected invalid entities;

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	virtual uint16 AddEntityID(byte grf_local_id, uint32 grfid, byte substitute_id);

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public:

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	EntityIDMapping *mapping_ID; ///< mapping of ids from grf files.  Public out of convenience

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	OverrideManagerBase(uint16 offset, uint16 maximum, uint16 invalid);

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	virtual ~OverrideManagerBase();

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	void ResetOverride();

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	void ResetMapping();

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	void Add(uint8 local_id, uint entity_type);

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	uint16 GetSubstituteID(byte entity_id);

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	uint16 GetID(uint8 grf_local_id, uint32 grfid);

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	inline uint16 GetMaxMapping() { return max_new_entities; };

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	inline uint16 GetMaxOffset() { return max_offset; };

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};

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struct HouseSpec;

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class HouseOverrideManager : public OverrideManagerBase

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{

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public:

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	HouseOverrideManager(uint16 offset, uint16 maximum, uint16 invalid) : OverrideManagerBase(offset, maximum, invalid) {};

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	void SetEntitySpec(const HouseSpec *hs);

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};

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extern HouseOverrideManager _house_mngr;

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#endif /* NEWGRF_COMMONS_H */