diff options
Diffstat (limited to 'main.asm')
| -rw-r--r-- | main.asm | 369 |
1 files changed, 1 insertions, 368 deletions
@@ -1314,374 +1314,7 @@ Functionb06: ; b06 ; b40 -FarDecompress: ; b40 -; Decompress graphics data at a:hl to de - -; put a away for a sec - ld [$c2c4], a -; save bank - ld a, [hROMBank] - push af -; bankswitch - ld a, [$c2c4] - rst Bankswitch - -; what we came here for - call Decompress - -; restore bank - pop af - rst Bankswitch - ret -; b50 - - -Decompress: ; b50 -; Pokemon Crystal uses an lz variant for compression. - -; This is mainly used for graphics, but the intro's -; tilemaps also use this compression. - -; This function decompresses lz-compressed data at hl to de. - - -; Basic rundown: - -; A typical control command consists of: -; -the command (bits 5-7) -; -the count (bits 0-4) -; -and any additional params - -; $ff is used as a terminator. - - -; Commands: - -; 0: literal -; literal data for some number of bytes -; 1: iterate -; one byte repeated for some number of bytes -; 2: alternate -; two bytes alternated for some number of bytes -; 3: zero (whitespace) -; 0x00 repeated for some number of bytes - -; Repeater control commands have a signed parameter used to determine the start point. -; Wraparound is simulated: -; Positive values are added to the start address of the decompressed data -; and negative values are subtracted from the current position. - -; 4: repeat -; repeat some number of bytes from decompressed data -; 5: flipped -; repeat some number of flipped bytes from decompressed data -; ex: $ad = %10101101 -> %10110101 = $b5 -; 6: reverse -; repeat some number of bytes in reverse from decompressed data - -; If the value in the count needs to be larger than 5 bits, -; control code 7 can be used to expand the count to 10 bits. - -; A new control command is read in bits 2-4. -; The new 10-bit count is split: -; bits 0-1 contain the top 2 bits -; another byte is added containing the latter 8 - -; So, the structure of the control command becomes: -; 111xxxyy yyyyyyyy -; | | | | -; | | our new count -; | the control command for this count -; 7 (this command) - -; For more information, refer to the code below and in extras/gfx.py . - -; save starting output address - ld a, e - ld [$c2c2], a - ld a, d - ld [$c2c3], a - -.loop -; get next byte - ld a, [hl] -; done? - cp $ff ; end - ret z - -; get control code - and %11100000 - -; 10-bit param? - cp $e0 ; LZ_HI - jr nz, .normal - - -; 10-bit param: - -; get next 3 bits (%00011100) - ld a, [hl] - add a - add a ; << 3 - add a - -; this is our new control code - and %11100000 - push af - -; get param hi - ld a, [hli] - and %00000011 - ld b, a - -; get param lo - ld a, [hli] - ld c, a - -; read at least 1 byte - inc bc - jr .readers - - -.normal -; push control code - push af -; get param - ld a, [hli] - and %00011111 - ld c, a - ld b, $0 -; read at least 1 byte - inc c - -.readers -; let's get started - -; inc loop counts since we bail as soon as they hit 0 - inc b - inc c - -; get control code - pop af -; command type - bit 7, a ; 80, a0, c0 - jr nz, .repeatertype - -; literals - cp $20 ; LZ_ITER - jr z, .iter - cp $40 ; LZ_ALT - jr z, .alt - cp $60 ; LZ_ZERO - jr z, .zero - ; else $00 - -; 00 ; LZ_LIT -; literal data for bc bytes -.loop1 -; done? - dec c - jr nz, .next1 - dec b - jp z, .loop - -.next1 - ld a, [hli] - ld [de], a - inc de - jr .loop1 - - -; 20 ; LZ_ITER -; write byte for bc bytes -.iter - ld a, [hli] - -.iterloop - dec c - jr nz, .iternext - dec b - jp z, .loop - -.iternext - ld [de], a - inc de - jr .iterloop - - -; 40 ; LZ_ALT -; alternate two bytes for bc bytes - -; next pair -.alt -; done? - dec c - jr nz, .alt0 - dec b - jp z, .altclose0 - -; alternate for bc -.alt0 - ld a, [hli] - ld [de], a - inc de - dec c - jr nz, .alt1 -; done? - dec b - jp z, .altclose1 -.alt1 - ld a, [hld] - ld [de], a - inc de - jr .alt - -; skip past the bytes we were alternating -.altclose0 - inc hl -.altclose1 - inc hl - jr .loop - - -; 60 ; LZ_ZERO -; write 00 for bc bytes -.zero - xor a - -.zeroloop - dec c - jr nz, .zeronext - dec b - jp z, .loop - -.zeronext - ld [de], a - inc de - jr .zeroloop - - -; repeats -; 80, a0, c0 -; repeat decompressed data from output -.repeatertype - push hl - push af -; get next byte - ld a, [hli] -; absolute? - bit 7, a - jr z, .absolute - -; relative -; a = -a - and %01111111 ; forget the bit we just looked at - cpl -; add de (current output address) - add e - ld l, a - ld a, $ff ; -1 - adc d - ld h, a - jr .repeaters - -.absolute -; get next byte (lo) - ld l, [hl] -; last byte (hi) - ld h, a -; add starting output address - ld a, [$c2c2] - add l - ld l, a - ld a, [$c2c3] - adc h - ld h, a - -.repeaters - pop af - cp $80 ; LZ_REPEAT - jr z, .repeat - cp $a0 ; LZ_FLIP - jr z, .flip - cp $c0 ; LZ_REVERSE - jr z, .reverse - -; e0 -> 80 - -; 80 ; LZ_REPEAT -; repeat some decompressed data -.repeat -; done? - dec c - jr nz, .repeatnext - dec b - jr z, .cleanup - -.repeatnext - ld a, [hli] - ld [de], a - inc de - jr .repeat - - -; a0 ; LZ_FLIP -; repeat some decompressed data w/ flipped bit order -.flip - dec c - jr nz, .flipnext - dec b - jp z, .cleanup - -.flipnext - ld a, [hli] - push bc - ld bc, $0008 - -.fliploop - rra - rl b - dec c - jr nz, .fliploop - ld a, b - pop bc - ld [de], a - inc de - jr .flip - - -; c0 ; LZ_REVERSE -; repeat some decompressed data in reverse -.reverse - dec c - jr nz, .reversenext - - dec b - jp z, .cleanup - -.reversenext - ld a, [hld] - ld [de], a - inc de - jr .reverse - - -.cleanup -; get type of repeat we just used - pop hl -; was it relative or absolute? - bit 7, [hl] - jr nz, .next - -; skip two bytes for absolute - inc hl -; skip one byte for relative -.next - inc hl - jp .loop -; c2f - - +INCLUDE "engine/decompress.asm" UpdatePalsIfCGB: ; c2f |