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https://github.com/deater/dos33fsprogs.git
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116 lines
2.1 KiB
ArmAsm
116 lines
2.1 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 #$0
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tay ; init Y to 0
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sta TEMP ; stores the xcoord
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sta CV ; ycoord=0
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jsr load_and_increment ; load xsize
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sta CH
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rle_loop:
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jsr load_and_increment
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cmp #$A1 ; if 0xa1
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beq rle_done ; we are done
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pha
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and #$f0 ; mask
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cmp #$a0 ; see if special AX
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beq decompress_special
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pla ; note, PLA sets flags!
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ldx #$1 ; only want to print 1
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bne decompress_run
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decompress_special:
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pla
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and #$0f ; check if was A0
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bne decompress_color ; if A0 need to read run, color
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decompress_large:
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jsr load_and_increment ; get run length
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decompress_color:
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tax ; put runlen into X
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jsr load_and_increment ; get color
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decompress_run:
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rle_run_loop:
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sta (BASL),y ; write out the value
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inc BASL ; increment the pointer
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bne rle_skip3 ; if wrapped
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inc BASH ; then increment the high value
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rle_skip3:
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pha ; store colore for later
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inc TEMP ; increment the X value
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lda TEMP
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cmp CH ; compare against the image width
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bcc rle_not_eol ; if less then keep going
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lda BASL ; cheat to avoid a 16-bit add
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cmp #$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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sta TEMP
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rle_not_eol:
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pla ; restore color
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dex
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bne rle_run_loop ; if not zero, keep looping
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beq 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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load_and_increment:
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lda (GBASL),y ; load value ; 5?
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inc GBASL ; 5?
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bne lskip2 ; 2nt/3
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inc GBASH ; 5?
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lskip2:
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rts ; 6
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