; Use a 020-capable assembler for this!!
		MC68020

		BSS
;first longword: data read pointer
;second longword: data end pointer (the last sample WORD to play)
;third longword: stereo offset pointer (# of bytes to add to get the right channel, 0 = mono)
;fourth longword: value to add (fixed rate only)
;fifth longword: remaining add offset (only lower word used)
Auradata	ds.l	5
owntimer	ds.w	1
Aurachmode	ds.w	1
Auraratemode	ds.w	1
vbr_addr	ds.l	1
		DATA
Auraperlimit	dc.w	248
Aurahandler	dc.l	AuraIntHandler
playing_Aura	dc.w	0

		SECTION	"text",CODE
		XDEF	_InitAura,_RemAura,_PlayAura,_StopAura,_SetAuraParams

; For Barfly...
		BOPT	ws-,w4-

; _InitAura (void) -- initialize sample playback system
; returns: 0 = ok, nonzero = error
_InitAura
		tst.w	owntimer
		bne.s	rm_rts
		movem.l	a5/a6,-(sp)
		move.w	#$400,$dff09a	;audio ch #3 interrupt off
		movea.l	4.w,a6
		btst	#0,$129(a6)	;test 68010+ of AttnFlags
		beq.s	1$
		lea	initaura_superv(pc),a5
		jsr	-$1E(a6)	;Supervisor()
		move.l	a0,vbr_addr
1$		move.l	vbr_addr,a0
		move.l	$70(a0),oldaudiointr	;MODIFIED CODE... therefore...
		jsr	-$27C(a6)		;CacheClearU()
		move.w	#1,owntimer
		moveq	#0,d0
		movem.l	(sp)+,a5/a6
		rts

initaura_superv	movec	VBR,a0
		rte

;_RemAura (void) -- deallocate sample playback system resources
_RemAura	tst.w	owntimer
		beq.s	rm_rts
		clr.w	owntimer
		move.w	#$400,$dff09a	;audio ch #3 interrupt off
		move.l	vbr_addr,a0
		move.l	oldaudiointr,$70(a0)
rm_rts		rts

AuraSIntHandler	;single channel playback
		move.l	d0,-(sp)
		move.w	$dff01e,d0
		btst	#$A,d0		;intr 3?
		beq.w	jmpoldintr
		move.l	a0,-(sp)
		move.w	#$400,$dff09c
		movea.l	Auradata,a0	;addr...
		move.w	(a0)+,$A20000	;final...
		move.w	#0,$dff0da
		cmpa.l	Auradata+4,a0
		bhi.s	Auraaudintr_end
		move.l	a0,Auradata
		move.l	(sp)+,a0
		move.l	(sp)+,d0
		rte

AuraIntHandler	; plays through both channels
		move.l	d0,-(sp)
		move.w	$dff01e,d0
		btst	#$A,d0		;intr 3?
		beq.s	jmpoldintr
		move.l	a0,-(sp)
		move.w	#$400,$dff09c
		movea.l	Auradata,a0	;addr...
		move.w	(a0)+,$A20000	;final...
		move.l	Auradata+8,d0
		move.w	-2(a0,d0.l),$A20002	;stereo offset
		move.w	#0,$dff0da
		cmpa.l	Auradata+4,a0
		bhi.s	Auraaudintr_end
		move.l	a0,Auradata
		move.l	(sp)+,a0
		move.l	(sp)+,d0
		rte

jmpoldintr	move.l	(sp)+,d0
		dc.w	$4ef9
oldaudiointr	dc.l	0

Auraaudintr_end_f
		move.l	(sp)+,a1
Auraaudintr_end	move.w	#$400,$dff09a
		move.l	(sp)+,a0
		move.l	(sp)+,d0
		clr.b	playing_Aura
		rte

AuraFIntHandler	; plays through both channels, fixed output rate
		move.l	d0,-(sp)
		move.w	$dff01e,d0
		btst	#$A,d0		;intr 3?
		beq.s	jmpoldintr
		move.l	a0,-(sp)
		move.l	a1,-(sp)
		lea	Auradata,a1
		move.w	#$400,$dff09c
		movea.l	(a1),a0	;addr...
		move.w	(a0),$A20000	;final...
		move.l	8(a1),d0
		move.w	0(a0,d0.l),$A20002 ;stereo offset (only mono (= 0) in V5.04 though)
		moveq	#0,d0
		move.w	d0,$dff0da
		move.w	18(a1),d0	;get remaining offset fraction (always < 1 [0x10000])
		add.l	12(a1),d0	;add rate value
		swap	d0
		adda.w	d0,a0		;add to sample pointer
		adda.w	d0,a0		;twice, because we handle words!
		swap	d0
		move.w	d0,18(a1)	;store current fraction...
		cmpa.l	4(a1),a0
		bhi.s	Auraaudintr_end_f
		move.l	a0,(a1)
		move.l	(sp)+,a1
		move.l	(sp)+,a0
		move.l	(sp)+,d0
		rte

AuraSFIntHandler ; plays through single channel, fixed output rate
		move.l	d0,-(sp)
		move.w	$dff01e,d0
		btst	#$A,d0		;intr 3?
		beq.w	jmpoldintr
		move.l	a0,-(sp)
		move.l	a1,-(sp)
		lea	Auradata,a1
		move.w	#$400,$dff09c
		movea.l	(a1),a0	;addr...
		move.w	(a0),$A20000	;final...
		moveq	#0,d0
		move.w	d0,$dff0da
		move.w	18(a1),d0	;get remaining offset fraction (always < 1 [0x10000])
		add.l	12(a1),d0	;add rate value
		swap	d0
		adda.w	d0,a0		;add to sample pointer
		adda.w	d0,a0		;twice, because we handle words!
		swap	d0
		move.w	d0,18(a1)	;store current fraction...
		cmpa.l	4(a1),a0
		bhi.w	Auraaudintr_end_f
		move.l	a0,(a1)
		move.l	(sp)+,a1
		move.l	(sp)+,a0
		move.l	(sp)+,d0
		rte

;_PlayAura -- Play Aura sample, input registers:
;	A0 = sample (struct Soitin *)
;	D0 = sample start offset (in WORDs)
;	D1 = sample period (UWORD)
;	D2 = sample end offset (i.e. offs to first word NOT to play) (0 = play until end)

_PlayAura	tst.w	owntimer
		beq.w	playAura_exit
		addq.l	#6,a0		;skip header
		add.l	d0,d0		;words to bytes
		add.l	a0,d0		;d0 = sample start
		move.l	d0,Auradata
		btst	#5,-1(a0)	;STEREO?
		bne.s	pmd_stereo
		moveq	#0,d0
		bra.s	pmd_setstereo
pmd_stereo	move.l	a0,d0
		add.l	-6(a0),d0	;add sample length...
pmd_setstereo	move.l	d0,Auradata+8	;store stereo offset
		tst.l	d2
		bne.s	pmd_givenend
		move.l	-6(a0),d0	;get length
		bra.s	pmd_setend
pmd_givenend	move.l	d2,d0
		add.l	d0,d0
pmd_setend	lea	-2(a0,d0.l),a0	;ptr to last WORD
		move.l	a0,Auradata+4
		moveq	#0,d0
		move.w	Auraperlimit,d0
		tst.w	Auraratemode
		bne.s	pmd_fixedrate
		cmp.w	d0,d1
		bhi.s	playAura_noovf
		move.w	d0,d1
playAura_noovf
		lsr.w	#1,d1
		movea.l	vbr_addr,a1
		move.l	Aurahandler,$70(a1)
		lea	$dff000,a0
		move.w	#$8400,$9a(a0)	;INTENA
		move.w	#$0380,$9a(a0)
		move.w	d1,$d6(a0)
		move.w	#0,$d8(a0)
		move.w	#$8400,$9c(a0)	;INTREQ
		st	playing_Aura
playAura_exit	rts

;	calculations for fixed playback rate...
pmd_fixedrate
; multiply playback period by 16384...
		swap	d0
		lsr.l	#2,d0
; divide by note period...
		divu	d1,d0
; clear upper word and multiply by 4
		swap	d0
		clr.w	d0
		swap	d0
		add.l	d0,d0
		add.l	d0,d0
; now we have a rate multiplier...
		move.l	d0,Auradata+12
		clr.l	Auradata+16
		move.w	Auraperlimit,d1
		bra.s	playAura_noovf	;set timer to run at maximum rate

; _StopAura - may only trash A1!
_StopAura	tst.w	owntimer
		beq.s	stopAura_exit
		clr.b	playing_Aura
		move.w	#$400,$dff09a	;audio 3 INTENA = 0
stopAura_exit	rts

SetHandlerAddr	tst.w	Aurachmode
		beq.s	sha_dual
		tst.w	Auraratemode
		beq.s	sha_s_var
		lea	AuraSFIntHandler(pc),a0
		bra.s	sha_set
sha_s_var	lea	AuraSIntHandler(pc),a0
		bra.s	sha_set
sha_dual	tst.w	Auraratemode
		beq.s	sha_d_var
		lea	AuraFIntHandler(pc),a0
		bra.s	sha_set
sha_d_var	lea	AuraIntHandler(pc),a0
sha_set		move.l	a0,Aurahandler
		rts

; SetAuraParams:
; D0 = flags:
;	bit 0:	0 = normal stereo/mono mode
;		1 = use only one channel (no stereo, slightly faster)
;	bit 1:	0 = use variable output rate
;		1 = locked output rate at max. period
; D1 = max. period
_SetAuraParams:
		move.w	d1,Auraratemode
		btst	#0,d0
		sne	Aurachmode+1
		btst	#1,d0
		sne	Auraratemode+1
		rts