; SetBlock.asm  implements inner loop of /SetBlock routine

;~~~~~~  THE BCPL ROUTINE IMPLEMENTED IS ~~~~~~~~

; PaintBlock(height) be
;	[
;	let Cnt = 0
;	let Ptr = SetBPtr; SetBptr = SetBPtr+1
;	[ 
;	if OnBits then @Ptr = @Ptr % (SetBMask & OnBits!(Cnt&3))
;	if OffBits then @Ptr = @Ptr & not (SetBMask & OffBits!(Cnt&1))
;	Ptr=Ptr+Nwrds
;	Cnt=Cnt+1
;	if Cnt ge height then return
;	] repeat
;	] 

;width = width-16
;if width le 0 then break
;SetBMask= width ls 16? MaskTable!width, -1

.srel
PaintBlock: PntBl
	.bextz SetBPtr,OnBits,OffBits,SetBMask,MaskTable,Mag
	.bext PaintBlock, PaintBits 

.nrel
SavedAC2: 	0
SavedAC3: 	0
height:	0
width:	0
Nwrds:	44
Minus16:	177760
Cnt:	0


PntBl:	sta 2 SavedAC2
	sta 3 SavedAC3
	sta 0 height
	sta 1 width
	movl 1 1 SZC
	jmp exit;	return if width is negative

Xloop: 	sub 0 0
	sta 0 Cnt
	lda 3 SetBPtr,0
	inc 3 2
	sta 2 SetBPtr,0

YLoop:	lda 2 OnBits,0
	mov 2 2 SNR
	jmp SkpOn
	lda 1 Cnt
	subzl 0 0;	make the constant 1
	movol 0 0;	make it a 3
	and 0 1
	add 1 2
	lda 2 0,2;	get the OnBits from table
	lda 1 SetBMask,0
	and 1 2
SkpOn: 	lda 0 0,3
	com 2 2
	and 2 0
	adc 2 0;	leave result in AC0

PntOff:	lda 2 OffBits,0
	mov 2 2 SNR
	jmp PntDn
	lda 1 Cnt
	movr# 1 1 SZC
	inc 2 2
	lda 2 0,2;	get the OnBits from table
	lda 1 SetBMask,0
	and 2 1
	com 1 1
	and 1 0

PntDn:	sta 0 0,3
	lda 2 Nwrds
	add 2 3
	lda 2 height
	lda 1 Cnt
	inc 1 1
	sta 1 Cnt
	subo 2 1 SEZ
	jmp YLoop

	lda 1 Minus16
	lda 0 width;	compute width-16
	addz 1 0 SBN;	jump to exit if the result is le 0
	jmp exit
	sta 0 width
	adc 2 2
	addz 0 1 SZC
	jmp SetMsk
	lda 2 MaskTable,0
	add 0 2
	lda 2 0,2
SetMsk:	sta 2 SetBMask,0
	jmp Xloop


exit:	lda 2 SavedAC2
	lda 3 SavedAC3
	jmp 1 3




	.end

;(0,4896)