dmzel fix code

int main(int argc, char* argv[])
{
  std::vector<uint8_t> rom;
  {
    std::ifstream file("C:\\dmg\\dmzel", std::ios::binary);
    if (file && file.is_open())
    {
      file.seekg(0, std::ios::end);
      uint64_t size = file.tellg();
      file.seekg(0x4000, std::ios::beg);

      int addr = 0;
      // read 0x4000 bytes from 0x4000 - 0x7FFF in each 0x10000 segment
      while (size > file.tellg())
      {
        rom.resize(rom.size() + 0x4000);
        file.read((char*)rom.data() + addr, 0x4000);
        addr += 0x4000;
        file.seekg(0xc000, std::ios::cur);
      }
    }
  }

  auto p = (char*)rom.data();

  // Fix header mapper type
  p[0x147] = 0x1b;

  // Fix header checksum
  uint8_t hdr_sum = 0;
  for (int i = 0x134; i < 0x14D; i++)
    hdr_sum = hdr_sum - p[i] - 1;

  p[0x14D] = hdr_sum;

  // Fix global checksum
  uint16_t gbsum = 0;
  for (int i = 0; i < rom.size(); i++)
  {
    if (i == 0x14E || i == 0x14F)
      continue; // cksum field not included in sum
    gbsum += (uint8_t)p[i];
  }

  p[0x14E] = (gbsum >> 8) & 0xFF;
  p[0x14F] = gbsum & 0xFF;

  // Write out file
  std::ofstream out("C:\\dmg\\dmzel_fixed.gbc", std::ios_base::binary);
  if (out && out.is_open())
    out.write(p, rom.size());

  return 0;
}