350 lines
4.1 KiB
ArmAsm
350 lines
4.1 KiB
ArmAsm
;
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; Lauri Kasanen, 6 Jun 2017
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; (C) Mega Cat Studios
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; An optimized LZ4 decompressor
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;
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.importzp sp, sreg, regsave, regbank
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.importzp tmp1, tmp2, tmp3, tmp4, ptr1, ptr2, ptr3, ptr4
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.macpack longbranch
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.import pushax,popax,_vram_write
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.export _vram_unlz4
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_out = regsave
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_written = regsave + 2
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_tmp = tmp1
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_token = tmp2
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_offset = ptr3
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_in = sreg
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_outlen = ptr4
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PPU_ADDR = $2006
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PPU_DATA = $2007
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; ---------------------------------------------------------------
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; void decompress_lz4 (const u8 *in, u8 * const out, const u16 outlen)
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; ---------------------------------------------------------------
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.segment "CODE"
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; size in ptr3, src in ptr1, dest in ptr2
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; don't touch size
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memcpy_r2v:
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lda ptr2+1
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sta PPU_ADDR
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lda ptr2
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sta PPU_ADDR
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lda ptr1
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ldx ptr1+1
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jsr pushax
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lda ptr3
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ldx ptr3+1
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jmp _vram_write
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memcpy_v2v:
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lda #0
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sta tmp3
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sta tmp4
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jmp @check
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@loop:
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; read source byte
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lda ptr1+1
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sta PPU_ADDR
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lda ptr1
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sta PPU_ADDR
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ldx PPU_DATA
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ldx PPU_DATA
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inc ptr1
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bne @nosrcinc
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inc ptr1+1
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@nosrcinc:
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; write dst byte
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lda ptr2+1
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sta PPU_ADDR
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lda ptr2
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sta PPU_ADDR
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stx PPU_DATA
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inc ptr2
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bne @nodstinc
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inc ptr2+1
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@nodstinc:
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; increase counter
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inc tmp3
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bne @noinc
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inc tmp4
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@noinc:
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@check:
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lda tmp3
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cmp ptr3
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lda tmp4
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sbc ptr3+1
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bcc @loop
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rts
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.proc _vram_unlz4: near
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sta _outlen
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stx _outlen+1
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jsr popax
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sta _out
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stx _out+1
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jsr popax
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sta _in
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stx _in+1
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;
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; written = 0;
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;
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lda #$00
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sta _written
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;
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; while (written < outlen) {
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;
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jmp L0046
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;
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; token = *in++;
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;
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L0004: ldy #0
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lda (_in),y
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sta _token
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inc _in
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bne L000A
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inc _in+1
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L000A:
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;
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; offset = token >> 4;
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;
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ldx #$00
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lsr a
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lsr a
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lsr a
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lsr a
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sta _offset
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stx _offset+1
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;
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; token &= 0xf;
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; token += 4; // Minmatch
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;
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lda _token
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and #$0F
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clc
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adc #4
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sta _token
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;
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; if (offset == 15) {
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;
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lda _offset
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cmp #$0F
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L0013: bne L001A
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;
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; tmp = *in++;
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;
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ldy #0
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lda (_in),y
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sta _tmp
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inc _in
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bne L0017
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inc _in+1
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L0017:
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;
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; offset += tmp;
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;
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clc
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adc _offset
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sta _offset
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lda #$00
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adc _offset+1
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sta _offset+1
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;
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; if (tmp == 255)
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;
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lda _tmp
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cmp #$FF
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;
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; goto moreliterals;
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;
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jmp L0013
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;
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; if (offset) {
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;
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L001A: lda _offset
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ora _offset+1
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beq L001C
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;
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; memcpy(&out[written], in, offset);
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;
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lda _out
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clc
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adc _written
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sta ptr2
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lda _out+1
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adc _written+1
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tax
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stx ptr2+1
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lda _in
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ldx _in+1
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sta ptr1
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stx ptr1+1
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jsr memcpy_r2v
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;
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; written += offset;
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;
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lda _offset
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clc
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adc _written
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sta _written
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lda _offset+1
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adc _written+1
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sta _written+1
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;
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; in += offset;
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;
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lda _offset
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clc
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adc _in
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sta _in
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lda _offset+1
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adc _in+1
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sta _in+1
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;
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; if (written >= outlen)
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;
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L001C: lda _written
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cmp _outlen
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lda _written+1
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sbc _outlen+1
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;
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; return;
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;
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bcc L0047
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rts
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;
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; memcpy(&offset, in, 2);
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;
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L0047: ldy #0
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lda (_in),y
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sta _offset
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iny
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lda (_in),y
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sta _offset+1
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;
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; in += 2;
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;
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lda #$02
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clc
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adc _in
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sta _in
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bcc L002F
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inc _in+1
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;
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; copysrc = out + written - offset;
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;
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L002F: lda _out
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clc
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adc _written
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pha
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lda _out+1
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adc _written+1
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tax
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pla
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sec
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sbc _offset
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sta ptr1
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txa
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sbc _offset+1
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sta ptr1+1
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;
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; offset = token;
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;
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lda #$00
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sta _offset+1
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lda _token
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sta _offset
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;
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; if (token == 19) {
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;
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cmp #$13
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L0045: bne L003C
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;
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; tmp = *in++;
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;
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ldy #0
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lda (_in),y
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sta _tmp
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inc _in
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bne L0039
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inc _in+1
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L0039:
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;
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; offset += tmp;
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;
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clc
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adc _offset
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sta _offset
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tya
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adc _offset+1
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sta _offset+1
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;
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; if (tmp == 255)
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;
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lda _tmp
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cmp #$FF
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;
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; goto morematches;
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;
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jmp L0045
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;
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; memcpy(&out[written], copysrc, offset);
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;
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L003C: lda _out
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clc
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adc _written
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sta ptr2
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lda _out+1
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adc _written+1
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tax
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stx ptr2+1
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jsr memcpy_v2v
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;
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; written += offset;
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;
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lda _offset
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clc
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adc _written
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sta _written
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lda _offset+1
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adc _written+1
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L0046: sta _written+1
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;
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; while (written < outlen) {
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;
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lda _written
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cmp _outlen
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lda _written+1
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sbc _outlen+1
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jcc L0004
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rts
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.endproc
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