; xos/s  20-Jun-2005  J.G.Harston

;
; Error-trapping MOS calls
;

;
; r[0]=A; r[1]=X; r[2]=Y; r[3]=P
; status=xos_call(r);
; status==0  - no error returned, A=r[0]; X=r[1]; Y=r[2]; P=r[3];
; status<>0  - error occured, ERR=status[0]; REPORT=status+1;
; status==-1 - escape occured and acknowledged

_xos_cli
	jsr ~xos
	.word oscli-1
_xos_byte
	jsr ~xos
	.word osbyte-1
_xos_word
	jsr ~xos
	.word osword-1
_xos_wrch
	jsr ~xos
	.word oswrch-1
_xos_asci
	jsr ~xos
	.word osasci-1
_xos_file
	jsr ~xos
	.word osfile-1
_xos_args
	jsr ~xos
	.word osargs-1
_xos_bget
	jsr ~xos
	.word osbget-1
_xos_bput
	jsr ~xos
	.word osbput-1
_xos_gbpb
	jsr ~xos
	.word osgbpb-1
_xos_find
	jsr ~xos
	.word osfind-1

; xos(reg *r)
; -----------
~xos
	pla
	sta tr+0		; (tr)=address of data after JSR
	pla
	sta tr+1
	ldy #0
	lda (sp),y
	sta pr+0
	iny
	lda (sp),y		;
	sta pr+1		; (pr)=address of register block
	lda (brk+1)
	pha
	lda (brkv+0)
	pha			; Save current BRKV
	lda #>~xostrap
	sta (brkv+1)
	lda #<~xostrap
	sta (brkv+0)
	lda rsp
	pha			; Save current return stack pointer
	tsx
	stx rsp			; Save stack pointer
	jsr ~xosjmp		; Call inline address
	sta tr+0		; Store returned values
	stx tr+1
	sty tr+2
	php
	pla
	sta tr+3
	dey
~xos2
	lda (tr),y		; Copy returned registers
	sta (pr),y
	iny
	cpy #4
	bne ~xos2
	ldx #0
	ldy #0			; Prepare to return zero
	bit 0xff
	bpl ~xosexit		; No pending escape
	lda #126
	jsr osbyte		; Acknowledge escape state
	dex
	dey			; Return -1 to indicate escape
~xosexit
	pla
	sta rsp			; Restore return stack pointer
	pla
	sta (brkv+0)
	pla
	sta (brkv+1)		; Restore BRKV
	rts

~xosjmp
	ldy #1
	lda (tr),y		; Point to inline address
	pha
	iny
	lda (tr),y
	pha			; Push it onto the stack
	iny
	lda (pr),y		; Get P
	pha			; Push it for later
	ldy #0
	lda (pr),y		; Get A
	pha			; Push it for later
	iny
	lda (pr),y		; Get X
	tax
	iny
	lda (pr),y		; Get Y
	tay
	pla			; Get A back
	plp			; Get P back
	rts			; Jump to OS routine

~xostrap
	ldx rsp
	txs			; Restore stack pointer
	ldx &FD
	ldy &FE			; Get pointer to error in &XXAA
	jmp ~xosexit