diff options
Diffstat (limited to 'tools/fixrom/fixrom.c')
| -rw-r--r-- | tools/fixrom/fixrom.c | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/tools/fixrom/fixrom.c b/tools/fixrom/fixrom.c new file mode 100644 index 00000000..0acbbe11 --- /dev/null +++ b/tools/fixrom/fixrom.c @@ -0,0 +1,190 @@ +#include <stdlib.h> +#include <stdio.h> +#include <stddef.h> +#include <stdint.h> +#include <string.h> +#include <stdnoreturn.h> +#include <stdarg.h> + +#define HEADER_SIZE 0x4000 + +uint8_t RomHeader[HEADER_SIZE]; + +static inline noreturn __attribute__((format(printf, 1, 2))) void fatal_error(const char * message, ...) +{ + va_list va_args; + va_start(va_args, message); + fputs("Error: ", stderr); + vfprintf(stderr, message, va_args); + fputc('\n', stderr); + va_end(va_args); + exit(EXIT_FAILURE); +} + +static inline void OffsetCheck(int offset) +{ + if (offset < 0 || offset >= HEADER_SIZE) + { + fatal_error("illegal access to header+%d", offset); + } +} + +static inline uint16_t HeaderReadU16LE(int offset) +{ + OffsetCheck(offset); + return RomHeader[offset] | + (RomHeader[offset + 1] << 8); +} + +static inline uint32_t HeaderReadU32LE(int offset) +{ + OffsetCheck(offset); + return RomHeader[offset] | + (RomHeader[offset + 1] << 8) | + (RomHeader[offset + 2] << 16) | + (RomHeader[offset + 3] << 24); +} + +static inline void HeaderWriteU16LE(int offset, uint16_t value) +{ + OffsetCheck(offset); + RomHeader[offset] = value; + RomHeader[offset + 1] = value >> 8; +} +static inline void HeaderWriteU32LE(int offset, uint32_t value) +{ + OffsetCheck(offset); + RomHeader[offset] = value; + RomHeader[offset + 1] = value >> 8; + RomHeader[offset + 2] = value >> 16; + RomHeader[offset + 3] = value >> 24; +} + +static uint16_t Calc_CRC16(uint8_t * data, size_t length, uint16_t crc) +{ + static uint16_t CrcTable[16] = { + 0x0000, + 0xCC01, + 0xD801, + 0x1400, + 0xF001, + 0x3C00, + 0x2800, + 0xE401, + 0xA001, + 0x6C00, + 0x7800, + 0xB401, + 0x5000, + 0x9C01, + 0x8801, + 0x4400, + }; + + uint16_t x = 0; + uint16_t y; + uint16_t bit = 0; + uint8_t * end = data + length; + while (data < end) + { + if (bit == 0) + { + x = data[0] | (data[1] << 8); + } + y = CrcTable[crc & 15]; + crc >>= 4; + crc ^= y; + y = CrcTable[(x >> bit) & 15]; + crc ^= y; + bit += 4; + if (bit == 16) + { + data += 2; + bit = 0; + } + } + return crc; +} + +int main(int argc, char ** argv) +{ + uint16_t secure_crc = 0xFFFF; + char game_code[4] = "NTRJ"; + int override_crc = 0; + int override_code = 0; + FILE * rom = NULL; + + for (int i = 1; i < argc; i++) { + if (strcmp(argv[i], "--secure-crc") == 0) + { + if (override_crc) + { + fatal_error("multiple --secure-crc options specified"); + } + char * endptr; + ulong secure_crc_l = strtoul(argv[++i], &endptr, 0); + if (secure_crc_l == 0 && endptr == argv[i]) + { + fatal_error("argument to --secure-crc must be an integer"); + } + if (secure_crc_l >= 0x10000) + { + fatal_error("argument to --secure-crc must be a 16-bit integer"); + } + secure_crc = secure_crc_l; + override_crc = 1; + } + else if (strcmp(argv[i], "--game-code") == 0) + { + if (override_code) + { + fatal_error("multiple --game-code options specified"); + } + if (strlen(argv[++i]) > 4) + { + fatal_error("argument to --game-code must be 4 characters or fewer"); + } + strncpy(game_code, argv[i], 4); + override_code = 1; + } + else + { + if (rom != NULL) + { + fatal_error("unrecognized %s argument: %s", argv[i][0] == '-' ? "flag" : "positional", argv[i]); + } + rom = fopen(argv[i], "r+b"); + if (rom == NULL) + { + fatal_error(argv[i][0] == '-' ? "unrecognized flag argument: %s" : "unable to open file '%s' for reading", argv[i]); + } + } + } + + if (fread(RomHeader, 1, HEADER_SIZE, rom) != HEADER_SIZE) + { + fatal_error("error reading the ROM header"); + } + + if (override_crc) + { + HeaderWriteU16LE(0x6C, secure_crc); + } + + if (override_code) + { + memcpy(RomHeader + 0xC, game_code, 4); + } + + uint16_t header_crc = Calc_CRC16((uint8_t *)RomHeader, 0x15E, 0xFFFF); + HeaderWriteU16LE(0x15E, header_crc); + + fseek(rom, 0, SEEK_SET); + if (fwrite(RomHeader, 1, HEADER_SIZE, rom) != HEADER_SIZE) + { + fatal_error("error writing the ROM header"); + } + + fclose(rom); + return EXIT_SUCCESS; +} |