BYTE *__cdecl sub_51A450(BYTE *pBuffer, signed __int64 dwSize, signed __int64 dwFlag1, int dwFlag2)
{
  BYTE *result;
  int v5;
  int v6;
  int v7;
  int v8;
  BYTE *Buffer;
  int v10;
  unsigned int v11;
  int v12;
  int v13;
  BYTE *v14;
  unsigned int v15;
  signed int v16;

  v16 = dwFlag1 % 12;
  if ( dwSize > 0xFFFFFFFFi64 )
  {
    Buffer = pBuffer;
    result = (BYTE *)dwFlag2;
    if ( dwSize >= 12 )
    {
      if ( v16 )
      {
        do
        {
          *Buffer++ ^= *(BYTE *)(v16++ + dwFlag2);
          result = (BYTE *)((unsigned __int64)(dwSize-- - 1) >> 32);
        }
        while ( v16 < 12 );
        v16 = 0;
      }
      if ( dwSize >= 12 )
      {
        v6 = dwSize / 12;
        dwSize -= (unsigned int)(12 * v6);
        v8 = *(DWORD *)dwFlag2;
        v7 = *(DWORD *)(dwFlag2 + 4);
        v5 = *(DWORD *)(dwFlag2 + 8);
        do
        {
          *(DWORD *)Buffer ^= v8;
          *((DWORD *)Buffer + 1) ^= v7;
          result = Buffer;
          *((DWORD *)Buffer + 2) ^= v5;
          Buffer += 12;
          --v6;
        }
        while ( v6 );
      }
    }
    if ( SHIDWORD(dwSize) >= 0 && (SHIDWORD(dwSize) > 0 || (DWORD)dwSize) )
    {
      do
      {
        *Buffer++ ^= *(BYTE *)(v16 + dwFlag2);
        result = (BYTE *)(v16++ + 1);
        if ( v16 == 12 )
          v16 = 0;
        --dwSize;
      }
      while ( SHIDWORD(dwSize) > 0 || SHIDWORD(dwSize) >= 0 && (DWORD)dwSize );
    }
  }
  else
  {
    v15 = dwSize;
    result = pBuffer;
    v14 = pBuffer;
    if ( (unsigned int)dwSize >= 0xC )
    {
      if ( v16 )
      {
        do
        {
          *v14++ ^= *(BYTE *)(v16++ + dwFlag2);
          result = (BYTE *)(v15-- - 1);
        }
        while ( v16 < 12 );
        v16 = 0;
      }
      if ( v15 >= 0xC )
      {
        v11 = v15 / 0xC;
        v15 %= 0xCu;
        v13 = *(DWORD *)dwFlag2;
        v12 = *(DWORD *)(dwFlag2 + 4);
        v10 = *(DWORD *)(dwFlag2 + 8);
        do
        {
          *(DWORD *)v14 ^= v13;
          *((DWORD *)v14 + 1) ^= v12;
          result = v14;
          *((DWORD *)v14 + 2) ^= v10;
          v14 += 12;
          --v11;
        }
        while ( v11 );
      }
    }
    for ( ; v15; --v15 )
    {
      *v14++ ^= *(BYTE *)(v16 + dwFlag2);
      result = (BYTE *)(v16++ + 1);
      if ( v16 == 12 )
        v16 = 0;
    }
  }
  return result;
}