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/* REminiscence - Flashback interpreter
* Copyright (C) 2005-2011 Gregory Montoir
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "unpack.h"
static int rcr(UnpackCtx *uc, int CF) {
int rCF = (uc->chk & 1);
uc->chk >>= 1;
if (CF) {
uc->chk |= 0x80000000;
}
return rCF;
}
static int next_chunk(UnpackCtx *uc) {
int CF = rcr(uc, 0);
if (uc->chk == 0) {
uc->chk = READ_BE_UINT32(uc->src); uc->src -= 4;
uc->crc ^= uc->chk;
CF = rcr(uc, 1);
}
return CF;
}
static uint16 get_code(UnpackCtx *uc, uint8 num_chunks) {
uint16 c = 0;
while (num_chunks--) {
c <<= 1;
if (next_chunk(uc)) {
c |= 1;
}
}
return c;
}
static void dec_unk1(UnpackCtx *uc, uint8 num_chunks, uint8 add_count) {
uint16 count = get_code(uc, num_chunks) + add_count + 1;
uc->datasize -= count;
while (count--) {
*uc->dst = (uint8)get_code(uc, 8);
--uc->dst;
}
}
static void dec_unk2(UnpackCtx *uc, uint8 num_chunks) {
uint16 i = get_code(uc, num_chunks);
uint16 count = uc->size + 1;
uc->datasize -= count;
while (count--) {
*uc->dst = *(uc->dst + i);
--uc->dst;
}
}
bool delphine_unpack(uint8 *dst, const uint8 *src, int len) {
UnpackCtx uc;
uc.src = src + len - 4;
uc.datasize = READ_BE_UINT32(uc.src); uc.src -= 4;
uc.dst = dst + uc.datasize - 1;
uc.size = 0;
uc.crc = READ_BE_UINT32(uc.src); uc.src -= 4;
uc.chk = READ_BE_UINT32(uc.src); uc.src -= 4;
debug(DBG_UNPACK, "delphine_unpack() crc=0x%X datasize=0x%X", uc.crc, uc.datasize);
uc.crc ^= uc.chk;
do {
if (!next_chunk(&uc)) {
uc.size = 1;
if (!next_chunk(&uc)) {
dec_unk1(&uc, 3, 0);
} else {
dec_unk2(&uc, 8);
}
} else {
uint16 c = get_code(&uc, 2);
if (c == 3) {
dec_unk1(&uc, 8, 8);
} else if (c < 2) {
uc.size = c + 2;
dec_unk2(&uc, c + 9);
} else {
uc.size = get_code(&uc, 8);
dec_unk2(&uc, 12);
}
}
} while (uc.datasize > 0);
return uc.crc == 0;
}
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