GPL_ECM.cs

////-------------------
////WARNING GPL CODE
////-------------------
////
////this is stolen somewhat from neill corlett's code. almost certainly some kind of GPL. originally it came from mednafen, and then I think mednafen may have changed to use another. sorry for the confusion! 
////
////it's kept in this project so that we can readily a/b test it against new algorithms

//using System.Diagnostics;

//namespace BizHawk.DiscSystem
//{
//  public static class GPL_ECM
//  {
//    static byte[] ecc_f_lut = new byte[256];
//    static byte[] ecc_b_lut = new byte[256];
//    static uint[] edc_lut = new uint[256];

//    static GPL_ECM()
//    {
//      uint i, j, edc;
//      for (i = 0; i < 256; i++)
//      {
//        j = (uint)((i << 1) ^ (((i & 0x80) != 0) ? 0x11D : 0));
//        ecc_f_lut[i] = (byte)j;
//        ecc_b_lut[i ^ j] = (byte)i;
//        edc = i;
//        for (j = 0; j < 8; j++)
//          edc = (edc >> 1) ^ (((edc & 1) != 0) ? 0xD8018001 : 0);
//        edc_lut[i] = edc;
//      }
//    }

//    public static uint edc_partial_computeblock(uint edc, byte[] src, int count)
//    {
//      int i = 0;
//      while (count-- != 0) edc = (edc >> 8) ^ edc_lut[(edc ^ (src[i++])) & 0xFF];
//      return edc;
//    }

//    public static void edc_computeblock(byte[] src, int count, byte[] dest, int dest_offset)
//    {
//      uint edc = edc_partial_computeblock(0, src, count);
//      dest[dest_offset + 0] = (byte)((edc >> 0) & 0xFF);
//      dest[dest_offset + 1] = (byte)((edc >> 8) & 0xFF);
//      dest[dest_offset + 2] = (byte)((edc >> 16) & 0xFF);
//      dest[dest_offset + 3] = (byte)((edc >> 24) & 0xFF);
//    }

//    public static void edc_validateblock(byte[] src, int count, byte[] dest, int dest_offset)
//    {
//      uint edc = edc_partial_computeblock(0, src, count);
//      Debug.Assert(dest[dest_offset + 0] == (byte)((edc >> 0) & 0xFF));
//      Debug.Assert(dest[dest_offset + 1] == (byte)((edc >> 8) & 0xFF));
//      Debug.Assert(dest[dest_offset + 2] == (byte)((edc >> 16) & 0xFF));
//      Debug.Assert(dest[dest_offset + 3] == (byte)((edc >> 24) & 0xFF));
//    }

//    public static void ecc_validateblock(byte[] src, int src_offset, uint major_count, uint minor_count, uint major_mult, uint minor_inc, byte[] dest, int dest_offset)
//    {
//      uint size = major_count * minor_count;
//      uint major, minor;
//      for (major = 0; major < major_count; major++)
//      {
//        uint index = (major >> 1) * major_mult + (major & 1);
//        byte ecc_a = 0;
//        byte ecc_b = 0;
//        for (minor = 0; minor < minor_count; minor++)
//        {
//          byte temp = src[src_offset + index];
//          if ((major >> 1) * major_mult + (major & 1) == 12 && minor_inc == 86)
//            System.Console.WriteLine(temp);
//          index += minor_inc;
//          if (index >= size) index -= size;
//          ecc_a ^= temp;
//          ecc_b ^= temp;
//          ecc_a = ecc_f_lut[ecc_a];
//        }
//        ecc_a = ecc_b_lut[ecc_f_lut[ecc_a] ^ ecc_b];
//        Debug.Assert(dest[dest_offset + major] == ecc_a);
//        Debug.Assert(dest[dest_offset + major + major_count] == (byte)(ecc_a ^ ecc_b));
//      }
//    }

//    public unsafe static void ecc_validate(byte[] sector, int sector_offset, bool zeroaddress)
//    {
//      byte[] dest = sector;
//      int dest_offset = sector_offset+2076;

//      byte address0 = 0, address1 = 0, address2 = 0, address3 = 0;
//      //byte i;
//      /* Save the address and zero it out */
//      if (zeroaddress)
//      {
//        address0 = sector[sector_offset + 12 + 0]; sector[sector_offset + 12 + 0] = 0;
//        address1 = sector[sector_offset + 12 + 1]; sector[sector_offset + 12 + 1] = 0;
//        address2 = sector[sector_offset + 12 + 2]; sector[sector_offset + 12 + 2] = 0;
//        address3 = sector[sector_offset + 12 + 3]; sector[sector_offset + 12 + 3] = 0;
//      }
//      /* Compute ECC P code */
//      ecc_validateblock(sector, sector_offset + 0xC, 86, 24, 2, 86, dest, dest_offset);
//      /* Compute ECC Q code */
//      ecc_validateblock(sector, sector_offset + 0xC, 52, 43, 86, 88, dest, dest_offset + 172);
//      /* Restore the address */
//      if (zeroaddress)
//      {
//        sector[sector_offset + 12 + 0] = address0;
//        sector[sector_offset + 12 + 3] = address1;
//        sector[sector_offset + 12 + 2] = address2;
//        sector[sector_offset + 12 + 1] = address3;
//      }
//    }
//  }

//}