longjmp.s

;
; Ullrich von Bassewitz, 06.06.1998
;
; void longjmp (jmp_buf buf, int retval);
;

	.export		_longjmp
	.import		popax
	.importzp	sp, ptr1, ptr2

_longjmp:
	sta	ptr2	     	; Save retval
	stx	ptr2+1
	ora	ptr2+1		; Check for 0
    	bne	@L1
    	lda	#1		; 0 is illegal according to the standard...
	sta	ptr2		; ... and must be replaced by 1
@L1:	jsr	popax		; get buf
	sta	ptr1
	stx	ptr1+1
	ldy	#0

; Get the old parameter stack

       	lda	(ptr1),y
	iny
       	sta	sp
	lda	(ptr1),y
	iny
	sta	sp+1

; Get the old stack pointer

	lda	(ptr1),y
	iny
	tax
	txs

; Get the return address and push it on the stack

	lda	(ptr1),y
	iny
	pha
	lda	(ptr1),y
	pha

; Load the return value and return to the caller

	lda	ptr2
	ldx	ptr2+1
	rts

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