uInt8 CartridgeMC::peek()

in atari_py/ale_interface/src/emucore/CartMC.cxx [120:177]

• 44 lines of code
• 11 McCabe index (conditional complexity)

uInt8 CartridgeMC::peek(uInt16 address)
{
  address = address & 0x1FFF;

  // Accessing the RESET vector so lets handle the powerup special case
  if((address == 0x1FFC) || (address == 0x1FFD))
  {
    // Indicate that slot 3 is locked for now
    mySlot3Locked = true;
  }
  // Should we unlock slot 3?
  else if(mySlot3Locked && (address >= 0x1000) && (address <= 0x1BFF))
  {
    // Indicate that slot 3 is unlocked now
    mySlot3Locked = false;
  }

  // Handle reads made to the TIA addresses
  if(address < 0x1000)
  {
    return 0;
  }
  else
  {
    uInt8 block;

    if(mySlot3Locked && ((address & 0x0C00) == 0x0C00))
    {
      block = 0xFF;
    }
    else
    {
      block = myCurrentBlock[(address & 0x0C00) >> 10];
    }

    // Is this a RAM or a ROM access
    if(block & 0x80)
    {
      // ROM access
      return myImage[(uInt32)(block & 0x7F) * 1024 + (address & 0x03FF)];
    }
    else
    {
      // This is a RAM access, however, is it to the read or write port?
      if(address & 0x0200)
      {
        // Reading from the read port of the RAM block
        return myRAM[(uInt32)(block & 0x3F) * 512 + (address & 0x01FF)];
      }
      else
      {
        // Oops, reading from the write port of the RAM block!
        myRAM[(uInt32)(block & 0x3F) * 512 + (address & 0x01FF)] = 0;
        return 0;
      }
    }
  }  
}