From 41d1db14ef0c4f5d3c829e36de84e814053e43bc Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Sun, 14 Oct 2018 09:45:13 -0500
Subject: [PATCH] GBHawk: HuC1 support

---
 .../Nintendo/GBHawk/Mappers/Mapper_HuC1.cs    | 108 ++++++++++++++++--
 1 file changed, 98 insertions(+), 10 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_HuC1.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_HuC1.cs
index cef7f2bbdc..6f63e13541 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_HuC1.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Mappers/Mapper_HuC1.cs
@@ -4,31 +4,75 @@ using System;
 
 namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 {
-	// Default mapper with no bank switching
+	// hudson mapper used in ex Daikaijuu monogatari
 	public class MapperHuC1 : MapperBase
 	{
+		public int ROM_bank;
+		public int RAM_bank;
+		public bool RAM_enable;
+		public int ROM_mask;
+		public int RAM_mask;
+		public bool IR_signal;
+
 		public override void Initialize()
 		{
-			// nothing to initialize
+			ROM_bank = 0;
+			RAM_bank = 0;
+			RAM_enable = false;
+			ROM_mask = Core._rom.Length / 0x4000 - 1;
+
+			// some games have sizes that result in a degenerate ROM, account for it here
+			if (ROM_mask > 4) { ROM_mask |= 3; }
+
+			RAM_mask = 0;
+			if (Core.cart_RAM != null)
+			{
+				RAM_mask = Core.cart_RAM.Length / 0x2000 - 1;
+				if (Core.cart_RAM.Length == 0x800) { RAM_mask = 0; }
+			}
 		}
 
 		public override byte ReadMemory(ushort addr)
 		{
-			if (addr < 0x8000)
+			if (addr < 0x4000)
 			{
 				return Core._rom[addr];
 			}
-			else
+			else if (addr < 0x8000)
 			{
-				if (Core.cart_RAM != null)
+				return Core._rom[(addr - 0x4000) + ROM_bank * 0x4000];
+			}
+			else if ((addr >= 0xA000) && (addr < 0xC000))
+			{
+				if (RAM_enable)
 				{
-					return Core.cart_RAM[addr - 0xA000];
+					if (Core.cart_RAM != null)
+					{
+						if (((addr - 0xA000) + RAM_bank * 0x2000) < Core.cart_RAM.Length)
+						{
+							return Core.cart_RAM[(addr - 0xA000) + RAM_bank * 0x2000];
+						}
+						else
+						{
+							return 0xFF;
+						}
+					}
+					else
+					{
+						return 0xFF;
+					}
 				}
 				else
 				{
-					return 0;
+					// when RAM isn't enabled, reading from this area will return IR sensor reading
+					// for now we'll assume it never sees light (0xC0)
+					return 0xC0;
 				}
 			}
+			else
+			{
+				return 0xFF;
+			}
 		}
 
 		public override byte PeekMemory(ushort addr)
@@ -40,13 +84,47 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		{
 			if (addr < 0x8000)
 			{
-				// no mapping hardware available
+				if (addr < 0x2000)
+				{
+					RAM_enable = (value & 0xF) != 0xE;
+				}
+				else if (addr < 0x4000)
+				{
+					value &= 0x3F;
+
+					ROM_bank &= 0xC0;
+					ROM_bank |= value;
+					ROM_bank &= ROM_mask;
+				}
+				else if (addr < 0x6000)
+				{
+					RAM_bank = value & 3;
+					RAM_bank &= RAM_mask;
+				}
 			}
 			else
 			{
-				if (Core.cart_RAM != null)
+				if (RAM_enable)
 				{
-					Core.cart_RAM[addr - 0xA000] = value;
+					if (Core.cart_RAM != null)
+					{
+						if (((addr - 0xA000) + RAM_bank * 0x2000) < Core.cart_RAM.Length)
+						{
+							Core.cart_RAM[(addr - 0xA000) + RAM_bank * 0x2000] = value;
+						}
+					}
+				}
+				else
+				{
+					// I don't know if other bits here have an effect
+					if (value == 1)
+					{
+						IR_signal = true;
+					}
+					else if (value == 0)
+					{
+						IR_signal = false;
+					}
 				}
 			}
 		}
@@ -55,5 +133,15 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		{
 			WriteMemory(addr, value);
 		}
+
+		public override void SyncState(Serializer ser)
+		{
+			ser.Sync("ROM_Bank", ref ROM_bank);
+			ser.Sync("ROM_Mask", ref ROM_mask);
+			ser.Sync("RAM_Bank", ref RAM_bank);
+			ser.Sync("RAM_Mask", ref RAM_mask);
+			ser.Sync("RAM_enable", ref RAM_enable);
+			ser.Sync("IR_signal", ref IR_signal);
+		}
 	}
 }