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