;Copyright (C) 2008 Pierre Baudemont
;
;    This file is part of bf.
;
;    bf is free software; you can redistribute it and/or modify
;    it under the terms of the GNU General Public License as published by
;    the Free Software Foundation; either version 2 of the License, or
;    (at your option) any later version.
;
;    bf is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;    GNU General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with bf; if not, write to the Free Software
;    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA


;------------------------------------------------------------------------------;
;|vat lib - vat_var_open                                                      |;
;|given a var SYM name ( <folder>\<name> or <name>, the last will search in   |;
;|the current folder ), return the adress of its RAM page                     |;
;|                                                                            |;
;|STACK PARAMS (push in this order):                                          |;
;|-  var name, which must be a SYM_STR ! (null byte at the beginning and at   |;
;|the end of the string, and the pointeur must ref the final zero byte !)     |;
;|                                                                            |;
;|RETURN                                                                      |;
;|-  a0 : adress of the var page, null on error (ex: var not found, ...)      |;
;------------------------------------------------------------------------------;

	section ".data"
	include "OS.h"

	xdef vat_var_open

vat_var_open:

	; save the used registries
	move.l a2,-(a7)

	; put the ROM CALL table adr in a2
	move.l $C8,a2

	; perform the SymFindPtr ROM CALL
	clr.w -(a7)	; search the given folder
	move.l 10(a7),-(a7)	; get the name from the stack (param)
	move.l SymFindPtr*4(a2),a0	; adr of the ROM CALL put in a0
	jsr (a0)	; perform the ROM CALL, result in a0
	addq.l #6,a7	; clean the stack

	; if a0 is null, an error occurred (ex: var not found,...)
	move.l a0,d0
	tst.l d0
	beq	error	; on an error go to the end of the function (return null)

	; perform the HeapDeref ROM CALL
	move.w 12(a0),-(a7)	; HeapDeref needs the handle as param
	move.l HeapDeref*4(a2),a0
	jsr (a0)	; result in a0
	addq.l #2,a7	; clean the stack

error:
	; restore the saved registries
	move.l (a7)+,a2

	rts