mirror of
https://github.com/deater/dos33fsprogs.git
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99 lines
1.9 KiB
ArmAsm
99 lines
1.9 KiB
ArmAsm
;=================
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; load RLE image
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;=================
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; Output is BASH/BASL
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; Input is in GBASH/GBASL
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load_rle_gr:
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lda #$0
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tax
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tay ; init X and Y to 0
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sta CV ; ycoord=0
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lda (GBASL),y ; load xsize
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sta CH
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iny ; (we should check if we had
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; bad luck and overflows page)
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iny ; skip ysize
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rle_loop:
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lda (GBASL),y ; load run value
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cmp #$ff ; if 0xff
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beq rle_done ; we are done
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sta RUN
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iny ; point to next value
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bne rle_yskip1 ; if overflow, increment address
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inc GBASH
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rle_yskip1:
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lda (GBASL),y ; load value to write
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iny
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bne rle_yskip2
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inc GBASH
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rle_yskip2:
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sty TEMP2 ; save y for later
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pha
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lda #$0
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tay
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pla ; convoluted way to set y to 0
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rle_run_loop:
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sta (BASL),y ; write out the value
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inc BASL ; increment the pointer
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bne rle_skip3 ; if wrapped
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inc BASH ; then increment the high value
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rle_skip3:
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inx ; increment the X value
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cpx CH ; compare against the image width
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bcc rle_not_eol ; if less then keep going
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pha ; save out value on stack
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lda BASL ; cheat to avoid a 16-bit add
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cmp #$a7 ; we are adding 0x58 to get
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bcc rle_add_skip ; to the next line
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inc BASH
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rle_add_skip:
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clc
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adc #$58 ; actually do the 0x58 add
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sta BASL ; and store it back
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inc CV ; add 2 to ypos
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inc CV ; each "line" is two high
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lda CV ; load value
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cmp #15 ; if it's greater than 14 it wraps
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bcc rle_no_wrap ; Thanks Woz
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lda #$0 ; we wrapped, so set to zero
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sta CV
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; when wrapping have to sub 0x3d8
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sec ; this is a 16-bit subtract routine
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lda BASL
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sbc #$d8 ; LSB
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sta BASL
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lda BASH ; MSB
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sbc #$3 ;
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sta BASH
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rle_no_wrap:
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lda #$0 ; set X value back to zero
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tax
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pla ; restore value to write from stack
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rle_not_eol:
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dec RUN ; decrement run value
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bne rle_run_loop ; if not zero, keep looping
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ldy TEMP2 ; restore the input pointer
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sec
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bcs rle_loop ; and branch always
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rle_done:
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lda #$15 ; move the cursor somewhere sane
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sta CV
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rts
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