Convert .dat files from "Sonic Mega Collection" on GameCube to .md Genesis ROMs

dat2bin.cpp

#include <fstream>
#include <string>

int processdata(unsigned char *InData, unsigned char *OutData, int filedatasize) // OutData=0 to get size
{
   int CurrIn = 0x4; //Skip size
   int CurrOut = 0;
   while (CurrIn < filedatasize)
   {
      int Code = InData[CurrIn++];
      for (int i = 0; (i < 8) && (CurrIn < filedatasize); i++)
      {
         if (Code & 1)
         {
            if (OutData)
               OutData[CurrOut] = InData[CurrIn];
            CurrOut++;
            CurrIn++;
         }
         else
         {
            int OutDict = InData[CurrIn++];
            int OutCnt = InData[CurrIn++];
            OutDict |= ((OutCnt << 4) & 0xF00);
            OutCnt = (OutCnt & 0xF) + 2;
            OutDict |= (CurrOut & ~0xFFF);
            OutDict += 0x12;
            if (OutDict >= CurrOut)
               OutDict -= 0x1000;
            for (int j = 0; j <= OutCnt; j++)
            {
               if (OutData)
                  OutData[CurrOut] = OutDict >= 0 ? OutData[OutDict] : 0;
               CurrOut++;
               OutDict++;
            }
         }
         Code >>= 1;
      }
   }
   return CurrOut;
}

int main(int argc, char* argv[])
{
   if (argc < 3)
   {
      printf("Wrong number of arguments\n");
      return -1;
   }
   std::ifstream InFile(argv[1], std::ios::binary);
   printf("Decompressing %s to %s...\n", argv[1], argv[2]);
   InFile.seekg(0, std::ios::end);
   int filesize = InFile.tellg();
   InFile.seekg(0, std::ios::beg);
   unsigned char *InData = new unsigned char[filesize];
   InFile.read((char*)InData, filesize);
   int swapend = 0x702;
   if (filesize <= swapend)
      swapend = filesize-1;
   for (int i = 0; (3 * i) < swapend; i++)
   {
      char Tmp = InData[i];
      InData[i] = InData[swapend - i];
      InData[swapend - i] = Tmp;
   }
   int filedatasize = 0;
   for (int Curr = 0; Curr < 4; Curr++)
   {
      filedatasize <<= 8;
      filedatasize |= InData[3 - Curr];
   }

   for (int i = 0; i < filedatasize; i++)
      InData[i] ^= 0x54;

   // Only calling to get the output size.  Will be same as OutSize below.
   // Can skip this if using e.g. push_back() instead of unsigned char[]
   // or just set MaxBinSize large enough (max output file size).
   const int MaxBinSize = processdata(InData, 0, filedatasize);

   unsigned char* OutData = new unsigned char[MaxBinSize];
   const int OutSize = processdata(InData, OutData, filedatasize);
   swapend = 156;
   for (int i = 0; i < OutSize; i += (swapend + 1))
   {
      if (i + swapend >= OutSize)
         swapend = OutSize - i - 1;
      for (int j = 0; (j * 3) < swapend; j++)
      {
         char Tmp = OutData[i+j];
         OutData[i+j] = OutData[i+swapend-j];
         OutData[i+swapend-j] = Tmp;
      }
   }

   std::ofstream OutFile(argv[2], std::ios::binary);
   OutFile.write((char*)OutData, OutSize);

   delete[] InData;
   delete[] OutData;
   return 0;
}