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	CallHookPkt -- invoke a Hook function callback. (V36)

	return = CallHookPkt(hook,object,message);
	D0		     A0   A2	 A1

	ULONG CallHookPkt(struct Hook *,APTR,APTR);

	Performs the callback standard defined by a Hook structure.
	This function is really very simple; it effectively performs
	a JMP to Hook->h_Entry.

	It is probably just as well to do this operation in an
	assembly language function linked in to your program, possibly
	from a compiler supplied library or a builtin function.

	It is anticipated that C programs will often call a 'varargs'
	variant of this function which will be named CallHook. This
	function must be provided in a compiler specific library, but
	an example of use would be:

	result = CallHook(hook,dataobject,COMMAND_ID,param1,param2);

	The function CallHook() can be implemented in many C compilers
	like this:

	ULONG CallHook(struct Hook *hook, APTR object, ULONG command, ... )

	hook - pointer to an initialized Hook structure as defined in
	object - useful data structure in the particular context the hook is
		 being used for.
	message - pointer to a message to be passed to the hook. This is not
		  an Exec Message structure, but is a message in the OOP sense.

	return - the value returned by the hook function.

	The functions called through this function should follow normal
	register conventions unless EXPLICITLY documented otherwise (and
	they have a good reason too).


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