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From: singer@endor.harvard.edu (Rich Siegel)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Executing a code segement from Lightspeed Pascal?
Message-ID: <439@husc6.harvard.edu>
Date: 6 Oct 88 11:11:56 GMT
References: <8810051239.AA09466@decwrl.dec.com>
Sender: news@husc6.harvard.edu
Reply-To: singer@endor.UUCP (Rich Siegel)
Organization: Symantec/THINK Technologies, Bedford, MA
Lines: 77

In article <8810051239.AA09466@decwrl.dec.com> harrow@bagels.dec.com (Jeff Harrow, NMSG LKG2-2/Y10 DTN=226-5564) writes:
>I've got  a  programming question (which will show my weakness in
>Pascal... Oh well)
>
>
>Now, I tried to convert this to Pascal (Lightspeed, of course) as
>follows:
>
>procedure ShowHelp;
>  var
>   rsrcH : Handle;
>   pp : ProcPtr;
>
> begin
>  if rsrcH = GetResource('code', 2000) then
>   begin
>    HLock(rsrcH);
>    pp := @rsrcH;
>    pp;         <<<<<THIS, nor @PP, nor (@PP) works<<<<<<<<
>    ReleaseResource(rsrcH);
>   end;
> end;
>
>but I can't figure out how  to  actually  EXECUTE the code, whose
>entry point address should, I think, be  in pp.  (Some varients I
>tried are shown above.)

>I know that you have to be tricky in Pascal to do this, but what
>am I missing?

	Two things to do:

	First, if you're writing your code resource in C, the main routine
should be of type "pascal", as in

	pascal void main()

Second, to call a ProcPtr, you need the following inLine:

	PROCEDURE CallProc(p : ProcPtr);
	inline $205F, $4E90;

	which pops the last argument off the stack, and JSRs to it.

So...

	procedure ShowHelp;
	var 
		H : Handle;
		hState : SignedByte;
	
	begin
		H := GetResource('Code', 2000);
		if H <> NIL) then begin
			hState := HGetState(h);
			MoveHHi(h);
			HLock(h);
			CallProc(h^);
			HSetState(h, hState);
		end
	end;

The calls to HGetState and HSetState ensure that the resource is returned
to the same state of locked-ness when you're done with it, instead of
unconditionally unlocking it every time.

		--Rich

Rich Siegel
Staff Software Developer
THINK Technologies Division, Symantec Corp.
Internet: singer@endor.harvard.edu
UUCP: ..harvard!endor!singer
Phone: (617) 275-4800 x305

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or policies of Symantec Corporation or its employees.