feat(cartridge): add MBC1/MBC3/MBC5 mapper banking
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dualfroz committed
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1 file changed
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@@ -0,0 +1,289 @@
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using System.IO;
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namespace GameBoy.Cartridge
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{
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public sealed class NoMbc : ICartridgeMapper
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{
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private readonly Cartridge cart;
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public NoMbc(Cartridge cart)
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{
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this.cart = cart;
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}
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public byte Read(ushort address)
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{
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if (address < 0x8000)
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return address < cart.Rom.Length ? cart.Rom[address] : (byte)0xFF;
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if (address >= 0xA000 && address < 0xC000 && cart.Ram.Length > 0)
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return cart.Ram[address - 0xA000];
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return 0xFF;
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}
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public void Write(ushort address, byte value)
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{
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if (address >= 0xA000 && address < 0xC000 && cart.Ram.Length > 0)
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cart.Ram[address - 0xA000] = value;
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}
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public void SaveState(BinaryWriter writer)
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{
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}
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public void LoadState(BinaryReader reader)
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{
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}
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}
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public sealed class Mbc1 : ICartridgeMapper
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{
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private readonly Cartridge cart;
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private readonly int romBankCount;
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private readonly int ramBankCount;
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private int bankLow = 1;
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private int bankHigh;
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private int mode;
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private bool ramEnabled;
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public Mbc1(Cartridge cart)
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{
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this.cart = cart;
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romBankCount = cart.Rom.Length / 0x4000;
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ramBankCount = cart.Ram.Length > 0 ? cart.Ram.Length / 0x2000 : 0;
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}
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public byte Read(ushort address)
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{
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if (address < 0x4000)
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{
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int bank = mode == 1 ? (bankHigh << 5) : 0;
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return cart.Rom[MapRom(bank, address)];
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}
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if (address < 0x8000)
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{
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int low = bankLow == 0 ? 1 : bankLow;
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int bank = (bankHigh << 5) | low;
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return cart.Rom[MapRom(bank, address - 0x4000)];
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}
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if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled || ramBankCount == 0)
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return 0xFF;
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int bank = mode == 1 ? bankHigh % ramBankCount : 0;
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return cart.Ram[bank * 0x2000 + (address - 0xA000)];
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}
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return 0xFF;
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}
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public void Write(ushort address, byte value)
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{
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if (address < 0x2000)
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ramEnabled = (value & 0x0F) == 0x0A;
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else if (address < 0x4000)
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bankLow = value & 0x1F;
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else if (address < 0x6000)
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bankHigh = value & 0x03;
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else if (address < 0x8000)
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mode = value & 0x01;
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else if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled || ramBankCount == 0)
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return;
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int bank = mode == 1 ? bankHigh % ramBankCount : 0;
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cart.Ram[bank * 0x2000 + (address - 0xA000)] = value;
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}
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}
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private int MapRom(int bank, int offset)
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{
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int wrapped = bank % romBankCount;
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return wrapped * 0x4000 + offset;
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}
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public void SaveState(BinaryWriter writer)
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{
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writer.Write(bankLow);
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writer.Write(bankHigh);
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writer.Write(mode);
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writer.Write(ramEnabled);
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}
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public void LoadState(BinaryReader reader)
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{
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bankLow = reader.ReadInt32();
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bankHigh = reader.ReadInt32();
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mode = reader.ReadInt32();
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ramEnabled = reader.ReadBoolean();
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}
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}
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public sealed class Mbc3 : ICartridgeMapper
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{
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private readonly Cartridge cart;
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private readonly int romBankCount;
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private readonly int ramBankCount;
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private readonly Mbc3Rtc? rtc;
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private int romBank = 1;
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private int ramBank;
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private int rtcSelect = -1;
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private bool ramEnabled;
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public Mbc3(Cartridge cart, bool hasTimer)
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{
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this.cart = cart;
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romBankCount = cart.Rom.Length / 0x4000;
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ramBankCount = cart.Ram.Length > 0 ? cart.Ram.Length / 0x2000 : 0;
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rtc = hasTimer ? new Mbc3Rtc() : null;
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}
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public Mbc3Rtc? Rtc => rtc;
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public byte Read(ushort address)
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{
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if (address < 0x4000)
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return cart.Rom[address];
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if (address < 0x8000)
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{
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int bank = (romBank == 0 ? 1 : romBank) % romBankCount;
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return cart.Rom[bank * 0x4000 + (address - 0x4000)];
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}
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if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled)
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return 0xFF;
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if (rtcSelect >= 0 && rtc != null)
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return rtc.ReadRegister(rtcSelect);
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if (ramBank < ramBankCount)
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return cart.Ram[ramBank * 0x2000 + (address - 0xA000)];
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return 0xFF;
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}
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return 0xFF;
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}
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public void Write(ushort address, byte value)
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{
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if (address < 0x2000)
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ramEnabled = (value & 0x0F) == 0x0A;
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else if (address < 0x4000)
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romBank = value & 0x7F;
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else if (address < 0x6000)
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{
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if (value <= 0x03)
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{
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ramBank = value;
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rtcSelect = -1;
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}
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else if (value >= 0x08 && value <= 0x0C)
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rtcSelect = value;
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}
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else if (address < 0x8000)
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rtc?.WriteLatch(value);
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else if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled)
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return;
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if (rtcSelect >= 0 && rtc != null)
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{
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rtc.WriteRegister(rtcSelect, value);
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return;
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}
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if (ramBank < ramBankCount)
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cart.Ram[ramBank * 0x2000 + (address - 0xA000)] = value;
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}
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}
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public void SaveState(BinaryWriter writer)
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{
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writer.Write(romBank);
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writer.Write(ramBank);
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writer.Write(rtcSelect);
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writer.Write(ramEnabled);
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writer.Write(rtc != null);
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rtc?.SaveState(writer);
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}
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public void LoadState(BinaryReader reader)
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{
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romBank = reader.ReadInt32();
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ramBank = reader.ReadInt32();
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rtcSelect = reader.ReadInt32();
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ramEnabled = reader.ReadBoolean();
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bool hasRtc = reader.ReadBoolean();
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if (hasRtc)
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rtc?.LoadState(reader);
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}
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}
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public sealed class Mbc5 : ICartridgeMapper
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{
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private readonly Cartridge cart;
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private readonly int romBankCount;
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private readonly int ramBankCount;
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private int romBankLow = 1;
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private int romBankHigh;
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private int ramBank;
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private bool ramEnabled;
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public Mbc5(Cartridge cart)
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{
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this.cart = cart;
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romBankCount = cart.Rom.Length / 0x4000;
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ramBankCount = cart.Ram.Length > 0 ? cart.Ram.Length / 0x2000 : 0;
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}
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public byte Read(ushort address)
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{
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if (address < 0x4000)
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return cart.Rom[address];
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if (address < 0x8000)
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{
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int bank = ((romBankHigh << 8) | romBankLow) % romBankCount;
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return cart.Rom[bank * 0x4000 + (address - 0x4000)];
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}
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if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled || ramBank >= ramBankCount)
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return 0xFF;
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return cart.Ram[ramBank * 0x2000 + (address - 0xA000)];
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}
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return 0xFF;
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}
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public void Write(ushort address, byte value)
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{
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if (address < 0x2000)
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ramEnabled = (value & 0x0F) == 0x0A;
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else if (address < 0x3000)
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romBankLow = value;
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else if (address < 0x4000)
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romBankHigh = value & 0x01;
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else if (address < 0x6000)
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ramBank = value & 0x0F;
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else if (address >= 0xA000 && address < 0xC000)
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{
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if (!ramEnabled || ramBank >= ramBankCount)
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return;
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cart.Ram[ramBank * 0x2000 + (address - 0xA000)] = value;
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}
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}
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public void SaveState(BinaryWriter writer)
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{
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writer.Write(romBankLow);
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writer.Write(romBankHigh);
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writer.Write(ramBank);
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writer.Write(ramEnabled);
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}
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public void LoadState(BinaryReader reader)
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{
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romBankLow = reader.ReadInt32();
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romBankHigh = reader.ReadInt32();
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ramBank = reader.ReadInt32();
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ramEnabled = reader.ReadBoolean();
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}
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}
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}
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