113 lines
1.7 KiB
ArmAsm
113 lines
1.7 KiB
ArmAsm
;=================
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; load RLE image
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;=================
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; Output is A:00 (assume page aligned)
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; Input is in GBASH/GBASL
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; format: first byte=xsize
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; A0,X,Y means run of X bytes of Y color
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; A1 means end of file
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; A2-AF,X means run of low nibble, X color
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; if high nibble not A: just display color
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; CV = current Y
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; CH = max xsize (usually 40)
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; TEMP = page
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; TEMPY= current X
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load_rle_gr:
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sec
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sbc #4 ; adjust page to write to
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; to match gr_offsets
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sta TEMP
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ldy #$0 ; init Y to 0
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sty CV
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jsr load_and_increment ; load xsize
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sta CH
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jsr unrle_new_y
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rle_loop:
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jsr load_and_increment
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tax
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cmp #$A1 ; if 0xa1
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beq rle_done ; we are done
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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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; not special, just color
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txa ; put color back in A
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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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txa ; put read value back in A
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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 ; run length now in A
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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 into A
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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
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dec TEMPY
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bne rle_not_eol ; if less then keep going
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; if here, we are > max_X
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inc CV
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inc CV
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pha
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jsr unrle_new_y
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pla
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rle_not_eol:
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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
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inc GBASL
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bne lai_no_oflo
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inc GBASH
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lai_no_oflo:
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rts
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unrle_new_y:
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ldy CV
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lda gr_offsets,Y
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sta BASL
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lda gr_offsets+1,Y
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clc
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adc TEMP ; adjust for page
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sta BASH
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lda CH
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sta TEMPY
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ldy #0
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rts
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