metamod-r/metamod/src/meta_eiface.h

#pragma once

// We use our own versions of the engine/dll interface structs. We add a
// few dummy entries to the end and set them to 0. That way we are
// protected from updates to the HL SDK adding new functions which would
// cause a) the game dll copying arbitrary values from us and b) the game
// dll overwriting our memory when using an old Metamod with a new game
// dll.

// meta_new_dll_functions_t
struct meta_new_dll_functions_t: public NEW_DLL_FUNCTIONS
{
	// Fill this object with pointers copied from a NEW_DLL_FUNCTIONS struct.
	void set_from(NEW_DLL_FUNCTIONS* pFuncs);

	// Copy the pointers from this object to a NEW_DLL_FUNCTIONS struct.
	void copy_to(NEW_DLL_FUNCTIONS* pFuncs) const;
};

// meta_enginefuncs_t
struct meta_enginefuncs_t : public enginefuncs_t
{
	// Fill this object with pointers copied from an enginefuncs_t struct.
	void set_from(enginefuncs_t* pFuncs);

	// Copy the pointers from this object to an enginefuncs_t struct.
	void copy_to(enginefuncs_t* pFuncs) const;
};

// This is a specialisation of the meta_enginefuncs_t struct which is only
// used for the initial copy of the engine functions, i.e. those we get
// passed from the HL engine right at the beginning.
// Since there is only one master copy of engine functions this could be
// implemented as a singleton. This is left as an option for later.
struct HL_enginefuncs_t: public meta_enginefuncs_t
{
	HL_enginefuncs_t() {};

	// Fill this object with pointers copied from an enginefuncs_t struct
	// and fixup the interface.
	// For this class this happens in the GiveFptrsToDll() function
	// with the pointers passed from the HL engine.
	void initialise_interface(enginefuncs_t* pFuncs);

private:
	// Moving copy_to() and set_from() to the private space.
	void set_from(enginefuncs_t* pFuncs)
	{
		meta_enginefuncs_t::set_from(pFuncs);
	}

	void copy_to(enginefuncs_t* pFuncs)
	{
		meta_enginefuncs_t::copy_to(pFuncs);
	}
};