BizHawk/BizHawk.Emulation.Cores/Computers/Commodore64/Cartridge/Mapper000F.cs

using System;
using System.Collections.Generic;
using System.Linq;
using BizHawk.Common;

namespace BizHawk.Emulation.Cores.Computers.Commodore64.Cartridge
{
	// This is a mapper used commonly by System 3. It is
	// also utilized by the short-lived C64 Game System.

	// Bank select is DExx. You select them by writing to the
	// register DE00+BankNr. For example, bank 01 is a write
	// to DE01.

	public abstract partial class CartridgeDevice
	{
		private class Mapper000F : CartridgeDevice
		{
			[SaveState.DoNotSave]
			private readonly int[][] _banks; //8000
			[SaveState.SaveWithName("BankMask")]
			private readonly int _bankMask;
			[SaveState.SaveWithName("BankNumber")]
			private int _bankNumber;
			[SaveState.SaveWithName("CurrentBank")]
			private int[] _currentBank;

			public Mapper000F(IList<int> newAddresses, IList<int> newBanks, IList<int[]> newData)
			{
				var count = newAddresses.Count;

				pinGame = true;
				pinExRom = false;

				// build dummy bank
				var dummyBank = new int[0x2000];
				for (var i = 0; i < 0x2000; i++)
					dummyBank[i] = 0xFF; // todo: determine if this is correct

				switch (count)
				{
					case 64:
						_bankMask = 0x3F;
						_banks = new int[64][];
						break;
					case 32:
						_bankMask = 0x1F;
						_banks = new int[32][];
						break;
					case 16:
						_bankMask = 0x0F;
						_banks = new int[16][];
						break;
					case 8:
						_bankMask = 0x07;
						_banks = new int[8][];
						break;
					case 4:
						_bankMask = 0x03;
						_banks = new int[4][];
						break;
					case 2:
						_bankMask = 0x01;
						_banks = new int[2][];
						break;
					case 1:
						_bankMask = 0x00;
						_banks = new int[1][];
						break;
					default:
						throw new Exception("This looks like a System 3/C64GS cartridge but cannot be loaded...");
				}

				// for safety, initialize all banks to dummy
				for (var i = 0; i < _banks.Length; i++)
					_banks[i] = dummyBank;

				// now load in the banks
				for (var i = 0; i < count; i++)
				{
					if (newAddresses[i] == 0x8000)
					{
						_banks[newBanks[i] & _bankMask] = newData[i];
					}
				}

				BankSet(0);
			}

			protected void BankSet(int index)
			{
				_bankNumber = index & _bankMask;
				UpdateState();
			}

			public override int Peek8000(int addr)
			{
				return _currentBank[addr];
			}

			public override void PokeDE00(int addr, int val)
			{
				BankSet(addr);
			}

			public override int Read8000(int addr)
			{
				return _currentBank[addr];
			}

			private void UpdateState()
			{
				_currentBank = _banks[_bankNumber];
			}

			public override void WriteDE00(int addr, int val)
			{
				BankSet(addr);
			}

			public override void SyncState(Serializer ser)
			{
				base.SyncState(ser);
				if (ser.IsReader)
					BankSet(_bankNumber);
			}
		}
	}
}