109 lines
2.5 KiB
C++
109 lines
2.5 KiB
C++
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/* REminiscence - Flashback interpreter
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* Copyright (C) 2005-2015 Gregory Montoir
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (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, see <http://www.gnu.org/licenses/>.
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*/
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#include "unpack.h"
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struct UnpackCtx {
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int size, datasize;
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uint32_t crc;
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uint32_t bits;
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uint8_t *dst;
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const uint8_t *src;
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};
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static int shiftBit(UnpackCtx *uc, int CF) {
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int rCF = (uc->bits & 1);
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uc->bits >>= 1;
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if (CF) {
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uc->bits |= 0x80000000;
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}
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return rCF;
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}
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static int nextBit(UnpackCtx *uc) {
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int CF = shiftBit(uc, 0);
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if (uc->bits == 0) {
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uc->bits = READ_BE_UINT32(uc->src); uc->src -= 4;
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uc->crc ^= uc->bits;
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CF = shiftBit(uc, 1);
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}
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return CF;
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}
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static uint16_t getBits(UnpackCtx *uc, uint8_t num_bits) {
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uint16_t c = 0;
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while (num_bits--) {
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c <<= 1;
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if (nextBit(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, uint8_t num_bits, uint8_t add_count) {
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uint16_t count = getBits(uc, num_bits) + add_count + 1;
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uc->datasize -= count;
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while (count--) {
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*uc->dst = (uint8_t)getBits(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, uint8_t num_bits) {
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uint16_t i = getBits(uc, num_bits);
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uint16_t 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 delphine_unpack(uint8_t *dst, const uint8_t *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); 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); uc.src -= 4;
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uc.bits = READ_BE_UINT32(uc.src); uc.src -= 4;
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uc.crc ^= uc.bits;
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do {
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if (!nextBit(&uc)) {
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uc.size = 1;
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if (!nextBit(&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_t c = getBits(&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 = getBits(&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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