Extract maps from King's Bounty Genesis

#include <stdio.h> // For fputs/fprintf
#include <stdlib.h> // For EXIT_FAILURE/EXIT_SUCCESS
#include <sys/types.h> // For stat()
#include <sys/stat.h> // For stat()
#include <stdint.h> // For uint8_t
#if defined(_WIN32)
#include <direct.h> // For _mkdir
#endif

void print_usage() {
    fputs("Usage: <program> <rom> <output directory>", stderr);
}

int main(int argc, char** argv) {
    if (argc != 3) {
        print_usage();
        return EXIT_FAILURE;
    }

    FILE* rom = fopen(argv[1], "rb");
    if (rom == NULL) {
        fprintf(stderr, "Error: Couldn't open ROM file \"%s\"", argv[1]);
        print_usage();
        return EXIT_FAILURE;
    }

    fseek(rom, 0, SEEK_END);
    size_t rom_size = ftell(rom);
    fseek(rom, 0, SEEK_SET);

    uint8_t data[rom_size];
    fread(&data, sizeof(uint8_t), rom_size, rom);

    fclose(rom);

    // Not sure why I have to minus 64 here, but without it, the top row
    // of tiles is cut off in the output
    const int maps_begin = 0x1AA8E - 64;
    const int map_width = 64;
    const int map_height = 64;
    const int map_size = map_width * map_height;

    static const char* filenames[4] = {
        "continentia.bin",
        "forestria.bin",
        "archipelia.bin",
        "saharia.bin"
    };

    for (int i = 0; i < 4; ++i) {
        int start_offset = maps_begin + (i * map_size);

        uint8_t flipped_vertically[map_size];

        for (int j = 0; j < map_size; ++j) {
            // Break down index
            int x = j % map_width;
            int y = j / map_width;

            // Invert y
            y = map_height - y;

            // Recreate index
            int index = (y * map_width) + x;

            flipped_vertically[j] = data[start_offset + index];
        }

        char outfile_path[256];

#if defined(_WIN32)
        _mkdir(argv[2]);
#else
        mkdir(argv[2], 0700);
#endif

        if (snprintf(outfile_path, 256, "%s/%s", argv[2], filenames[i]) > 256) {
            fputs("Error: Output path too large", stderr);
            return EXIT_FAILURE;
        }

        // Write flipped data to file
        FILE* map_out = fopen(outfile_path, "wb");
        fwrite(flipped_vertically, sizeof(uint8_t), map_size, map_out);
        fclose(map_out);
    }

    return EXIT_SUCCESS;
}