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explode.c
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explode.c
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#include <stdio.h>
static unsigned char explode_token_base[4] = { 6, 10, 10, 18 };
static unsigned char static_token_extra_bits[12] = { 1, 1, 1, 1, 2, 3, 3, 4, 4, 5, 7, 14 };
unsigned char *src, *cmpr_data;
unsigned int write_pos, src_size, src_end /*a4*/, token_run_len /*d2*/;
int cmpr_pos /*a3*/;
unsigned char token;
unsigned short run_base_off_tbl[8];
unsigned char run_extra_bits_tbl[12];
static void copy_bytes(unsigned char *dst, unsigned char *src, int count){
for (int i = 0; i < count; i++){
dst[i] = src[i];
}
}
static unsigned short read_word(unsigned char *buf){
return ((buf[0] << 8) | buf[1]);
}
static unsigned int read_dword(unsigned char *buf){
return ((read_word(&buf[0]) << 16) | read_word(&buf[2]));
}
static void write_word(unsigned char *dst, unsigned short value){
dst[0] = (value >> 8) & 0xFF;
dst[1] = (value >> 0) & 0xFF;
}
static void write_dword(unsigned char *dst, unsigned int value){
write_word(&dst[0], (value >> 16) & 0xFFFF);
write_word(&dst[2], (value >> 0) & 0xFFFF);
}
unsigned int read_bits(unsigned char count){
unsigned int retn = 0;
for (int i = 0; i < count; i++){
char bit = (token >> 7);
token <<= 1;
if (!token){
token = (cmpr_data[cmpr_pos-1] << 1) | bit;
bit = (cmpr_data[--cmpr_pos] >> 7);
}
retn <<= 1;
retn |= bit;
}
return retn;
}
int check_imp(unsigned char *input){
unsigned int id, end_off, out_len;
if (!input){
return 0;
}
id = read_dword(&input[0]);
out_len = read_dword(&input[4]);
end_off = read_dword(&input[8]);
/* check for magic ID 'IMP!', or one of the other IDs used by Imploder
clones; ATN!, BDPI, CHFI, Dupa, EDAM, FLT!, M.H., PARA and RDC9 */
if (id != 0x494d5021 && id != 0x41544e21 && id != 0x42445049 && id != 0x43484649 && id != 0x44757061 &&
id != 0x4544414d && id != 0x464c5421 && id != 0x4d2e482e && id != 0x50415241 && id != 0x52444339){
return 0;
}
/* sanity checks */
return !((end_off & 1) || (end_off < 14) || ((end_off + 0x26) > out_len));
}
int explode(unsigned char *input){
if (!check_imp(input)){
return 0;
}
write_pos = 0, src_size = 0, src_end = 0 /*a4*/, token_run_len = 0 /*d2*/;
cmpr_pos = 0 /*a3*/;
token = 0;
src = input;
src_end = src_size = read_dword(&src[0x04]);
cmpr_data = &src[read_dword(&src[0x08])];
cmpr_pos = 0;
write_dword(&src[0x08], read_dword(&cmpr_data[0x00]));
write_dword(&src[0x04], read_dword(&cmpr_data[0x04]));
write_dword(&src[0x00], read_dword(&cmpr_data[0x08]));
token_run_len = read_dword(&cmpr_data[0x0C]);
if (!(cmpr_data[0x10] & 0x80)){
cmpr_pos--;
}
token /*d3*/ = cmpr_data[0x11];
for (int i = 0; i < 8; i++){
/*a1*/run_base_off_tbl[i] = read_word(&cmpr_data[0x12+i*2]);
}
copy_bytes(&run_extra_bits_tbl[0], &cmpr_data[0x22], 12);
//int cnt = 0;
while (1){
for (int i = 0; (i < token_run_len) && (src_end > 0); i++){
src[--src_end] = cmpr_data[--cmpr_pos];
}
if (src_end == 0){
break;
}
unsigned int match_len, selector;
if (read_bits(1)){
if (read_bits(1)){
if (read_bits(1)){
if (read_bits(1)){
if (read_bits(1)){
match_len = cmpr_data[--cmpr_pos];
selector = 3;
}
else{
match_len = read_bits(3) + 6;
selector = 3;
}
}
else{
match_len = 5;
selector = 3;
}
}
else{
match_len = 4;
selector = 2;
}
}
else{
match_len = 3;
selector = 1;
}
}
else{
match_len = 2;
selector = 0;
}
if (read_bits(1)){
if (read_bits(1)){
token_run_len = read_bits(static_token_extra_bits[selector+8]) + explode_token_base[selector];
}
else{
token_run_len = read_bits(static_token_extra_bits[selector+4]) + 2;
}
}
else{
token_run_len = read_bits(static_token_extra_bits[selector]);
}
unsigned char *match;
if (read_bits(1)){
if (read_bits(1)){
match = &src[src_end + read_bits(run_extra_bits_tbl[8+selector]) + run_base_off_tbl[4+selector] + 1];
}
else{
match = &src[src_end + read_bits(run_extra_bits_tbl[4+selector]) + run_base_off_tbl[selector] + 1];
}
}
else{
match = &src[src_end + read_bits(run_extra_bits_tbl[selector]) + 1];
}
//printf("%06X-%06X\n", match_len, src_end); cnt++;
for (int i = 0; (i < match_len) && (src_end > 0); i++){
src[--src_end] = *--match;
}
}
return src_size;
}
int imploded_size(unsigned char *input){
if(!check_imp(input)) return 0;
return read_dword(&input[8]) + 0x32;
}
int exploded_size(unsigned char *input){
if(!check_imp(input)) return 0;
return read_dword(&input[4]);
}