sm64/tools/sm64tools/n64cksum.c
2023-08-17 08:56:02 -04:00

143 lines
3.2 KiB
C

#include <stdio.h>
#include <stdlib.h>
#include "n64cksum.h"
#include "utils.h"
#define N64CKSUM_VERSION "0.1"
// compute N64 ROM checksums
// buf: buffer with extended SM64 data
// cksum: two element array to write CRC1 and CRC2 to
void n64cksum_calc_6102(unsigned char *buf, unsigned int cksum[]) {
uint32_t t2, t3, t4, t6, t7, t8, s0;
uint32_t a0, a1, a2, a3;
uint32_t v0, v1;
uint32_t seed, end_offset, cur_offset, buf_offset;
// derived from the SM64 boot code
seed = 0xF8CA4DDB; // 0x3f * 0x5d588b65;
end_offset = 0x100000;
cur_offset = 0;
buf_offset = 0x1000;
seed++;
a3 = seed;
t2 = seed;
t3 = seed;
s0 = seed;
a2 = seed;
t4 = seed;
do {
v0 = read_u32_be(&buf[buf_offset]);
v1 = a3 + v0;
a1 = v1;
if (v1 < a3) {
t2++;
}
v1 = v0 & 0x1F;
t7 = 32 - v1;
t8 = v0 >> t7;
t6 = v0 << v1;
a0 = t6 | t8;
a3 = a1;
t3 ^= v0;
s0 += a0;
if (a2 < v0) {
a2 ^= a3 ^ v0;
} else {
a2 ^= a0;
}
cur_offset += 4;
t7 = v0 ^ s0;
buf_offset += 4;
t4 += t7;
} while (cur_offset != end_offset);
cksum[0] = (a3 ^ t2) ^ t3;
cksum[1] = (s0 ^ a2) ^ t4;
}
void n64cksum_update_checksums(uint8_t *buf)
{
unsigned int cksum_offsets[] = {0x10, 0x14};
uint32_t read_cksum[2];
uint32_t calc_cksum[2];
int i;
// assume CIC-NUS-6102
INFO("BootChip: CIC-NUS-6102\n");
// calculate new N64 header checksum
n64cksum_calc_6102(buf, calc_cksum);
// mimic the n64sums output
for (i = 0; i < 2; i++) {
read_cksum[i] = read_u32_be(&buf[cksum_offsets[i]]);
INFO("CRC%d: 0x%08X ", i+1, read_cksum[i]);
INFO("Calculated: 0x%08X ", calc_cksum[i]);
if (calc_cksum[i] == read_cksum[i]) {
INFO("(Good)\n");
} else {
INFO("(Bad)\n");
}
}
// write checksums into header
INFO("Writing back calculated Checksum\n");
write_u32_be(&buf[cksum_offsets[0]], calc_cksum[0]);
write_u32_be(&buf[cksum_offsets[1]], calc_cksum[1]);
}
#ifdef N64CKSUM_STANDALONE
static void print_usage(void)
{
ERROR("Usage: n64cksum ROM [ROM_OUT]\n"
"\n"
"n64cksum v" N64CKSUM_VERSION ": N64 ROM checksum calculator\n"
"\n"
"File arguments:\n"
" ROM input ROM file\n"
" ROM_OUT output ROM file (default: overwrites input ROM)\n");
}
int main(int argc, char *argv[])
{
unsigned char *rom_data;
char *file_in;
char *file_out;
long length;
long write_length;
if (argc < 2) {
print_usage();
return EXIT_FAILURE;
}
file_in = argv[1];
if (argc > 2) {
file_out = argv[2];
} else {
file_out = argv[1];
}
length = read_file(file_in, &rom_data);
if (length < 0) {
ERROR("Error reading input file \"%s\"\n", file_in);
return EXIT_FAILURE;
}
n64cksum_update_checksums(rom_data);
write_length = write_file(file_out, rom_data, length);
free(rom_data);
if (write_length != length) {
ERROR("Error writing to output file \"%s\"\n", file_out);
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
#endif // N64CKSUM_STANDALONE