mirror of
https://github.com/libretro/scummvm.git
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123 lines
2.7 KiB
C++
123 lines
2.7 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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#include "common/endian.h"
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namespace Cruise {
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struct UnpackCtx {
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int size, datasize;
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uint32 crc;
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uint32 chk;
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byte *dst;
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const byte *src;
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};
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static int rcr(UnpackCtx *uc, int CF) {
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int rCF = (uc->chk & 1);
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uc->chk >>= 1;
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if (CF) {
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uc->chk |= 0x80000000;
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}
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return rCF;
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}
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static int nextChunk(UnpackCtx *uc) {
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int CF = rcr(uc, 0);
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if (uc->chk == 0) {
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uc->chk = READ_BE_UINT32(uc->src);
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uc->src -= 4;
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uc->crc ^= uc->chk;
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CF = rcr(uc, 1);
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}
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return CF;
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}
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static uint16 getCode(UnpackCtx *uc, byte numChunks) {
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uint16 c = 0;
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while (numChunks--) {
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c <<= 1;
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if (nextChunk(uc)) {
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c |= 1;
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}
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}
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return c;
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}
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static void unpackHelper1(UnpackCtx *uc, byte numChunks, byte addCount) {
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uint16 count = getCode(uc, numChunks) + addCount + 1;
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uc->datasize -= count;
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while (count--) {
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*uc->dst = (byte)getCode(uc, 8);
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--uc->dst;
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}
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}
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static void unpackHelper2(UnpackCtx *uc, byte numChunks) {
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uint16 i = getCode(uc, numChunks);
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uint16 count = uc->size + 1;
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uc->datasize -= count;
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while (count--) {
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*uc->dst = *(uc->dst + i);
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--uc->dst;
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}
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}
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bool delphineUnpack(byte *dst, const byte *src, int len) {
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UnpackCtx uc;
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uc.src = src + len - 4;
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uc.datasize = READ_BE_UINT32(uc.src);
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uc.src -= 4;
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uc.dst = dst + uc.datasize - 1;
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uc.size = 0;
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uc.crc = READ_BE_UINT32(uc.src);
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uc.src -= 4;
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uc.chk = READ_BE_UINT32(uc.src);
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uc.src -= 4;
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uc.crc ^= uc.chk;
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do {
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if (!nextChunk(&uc)) {
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uc.size = 1;
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if (!nextChunk(&uc)) {
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unpackHelper1(&uc, 3, 0);
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} else {
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unpackHelper2(&uc, 8);
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}
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} else {
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uint16 c = getCode(&uc, 2);
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if (c == 3) {
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unpackHelper1(&uc, 8, 8);
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} else if (c < 2) {
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uc.size = c + 2;
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unpackHelper2(&uc, c + 9);
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} else {
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uc.size = getCode(&uc, 8);
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unpackHelper2(&uc, 12);
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}
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}
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} while (uc.datasize > 0);
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return uc.crc == 0;
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}
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} // End of namespace Cruise
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