dos33fsprogs/tfv/tfv_old.s

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;=================
; load RLE image
;=================
; Output is BASH/BASL
; Input is in GBASH/GBASL
load_rle_gr:
lda #$0
tax
tay ; init X and Y to 0
sta CV ; ycoord=0
lda (GBASL),y ; load xsize
sta CH
iny ; (we should check if we had
; bad luck and overflows page)
iny ; skip ysize
rle_loop:
lda (GBASL),y ; load run value
cmp #$ff ; if 0xff
beq rle_done ; we are done
sta RUN
iny ; point to next value
bne rle_yskip1 ; if overflow, increment address
inc GBASH
rle_yskip1:
lda (GBASL),y ; load value to write
iny
bne rle_yskip2
inc GBASH
rle_yskip2:
sty TEMP2 ; save y for later
pha
lda #$0
tay
pla ; convoluted way to set y to 0
rle_run_loop:
sta (BASL),y ; write out the value
inc BASL ; increment the pointer
bne rle_skip3 ; if wrapped
inc BASH ; then increment the high value
rle_skip3:
inx ; increment the X value
cpx CH ; compare against the image width
bcc rle_not_eol ; if less then keep going
pha ; save out value on stack
lda BASL ; cheat to avoid a 16-bit add
cmp #$a7 ; we are adding 0x58 to get
bcc rle_add_skip ; to the next line
inc BASH
rle_add_skip:
clc
adc #$58 ; actually do the 0x58 add
sta BASL ; and store it back
inc CV ; add 2 to ypos
inc CV ; each "line" is two high
lda CV ; load value
cmp #15 ; if it's greater than 14 it wraps
bcc rle_no_wrap ; Thanks Woz
lda #$0 ; we wrapped, so set to zero
sta CV
; when wrapping have to sub 0x3d8
sec ; this is a 16-bit subtract routine
lda BASL
sbc #$d8 ; LSB
sta BASL
lda BASH ; MSB
sbc #$3 ;
sta BASH
rle_no_wrap:
lda #$0 ; set X value back to zero
tax
pla ; restore value to write from stack
rle_not_eol:
dec RUN ; decrement run value
bne rle_run_loop ; if not zero, keep looping
ldy TEMP2 ; restore the input pointer
sec
bcs rle_loop ; and branch always
rle_done:
lda #$15 ; move the cursor somewhere sane
sta CV
rts