nes-support mapper 178 and fix a regression from yesterday that made most roms not loadable

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -150,6 +150,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper116.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper164.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper176.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper178.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper180.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper193.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper227.cs" />

BizHawk.Emulation/Consoles/Nintendo/Docs/compatibility.txt

@@ -97,6 +97,7 @@ Open bus and bus conflict emulation is not considered complete or thorough in an
 164	Pirate		Junk - Started
 165	Pirate		Junk
 176 Chinese WXN Decent
+178 Chinese		Decent
 180	Misc (J)	Complete (but we don't implement the crazy climber controller) 
 182	MMC3Variant	Decent
 184	Sunsoft-1	Complete

BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs

@@ -256,6 +256,9 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		//this will be used to track classes that implement boards
 		[AttributeUsage(AttributeTargets.Class)]
 		public class INESBoardImplAttribute : Attribute { }
+		//this tracks derived boards that shouldnt be used by the implementation scanner
+		[AttributeUsage(AttributeTargets.Class)]
+		public class INESBoardImplCancelAttribute : Attribute { }
 		static List<Type> INESBoardImplementors = new List<Type>();
 
 		static NES()
@@ -266,6 +269,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				var attrs = type.GetCustomAttributes(typeof(INESBoardImplAttribute), true);
 				if (attrs.Length == 0) continue;
 				if (type.IsAbstract) continue;
+				var cancelAttrs = type.GetCustomAttributes(typeof(INESBoardImplCancelAttribute), true);
+				if (cancelAttrs.Length != 0) continue;
 				INESBoardImplementors.Add(type);
 			}
 		}

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper116.cs

@@ -8,6 +8,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 {
 	class Mapper116 : NES.NESBoardBase
 	{
+		[NES.INESBoardImplCancel]
 		class MMC3_CustomBoard : MMC3Board_Base
 		{
 			public override void WritePRG(int addr, byte value)

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper178.cs

@@ -0,0 +1,69 @@
+using System;
+using System.IO;
+using System.Diagnostics;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	class Mapper178 : NES.NESBoardBase
+	{
+		//configuration
+		int prg_bank_mask_32k;
+
+		//state
+		ByteBuffer prg_banks_32k = new ByteBuffer(1);
+		int reg4802;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			//configure
+			switch (Cart.board_type)
+			{
+				case "MAPPER178":
+					break;
+				default:
+					return false;
+			}
+			prg_bank_mask_32k = (Cart.prg_size / 32) - 1;
+
+			prg_banks_32k[0] = 0;
+
+			SetMirrorType(EMirrorType.Vertical);
+
+			return true;
+		}
+
+		public override void WriteEXP(int addr, byte value)
+		{
+			switch (addr)
+			{
+				case 0x0800: //$4800
+					SetMirrorType(value.Bit(0) ? EMirrorType.Horizontal : EMirrorType.Vertical);
+					break;
+				case 0x0801: //$4801
+					{
+						int reg4801 = (value >> 1) & 0xF;
+						int prg = reg4801 + (reg4802 << 2);
+						prg_banks_32k[0] = (byte)prg;
+						ApplyMemoryMapMask(prg_bank_mask_32k, prg_banks_32k);
+						break;
+					}
+				case 0x0802: //$4802
+					reg4802 = value;
+					break;
+			}
+			}
+
+		public override byte ReadPRG(int addr)
+		{
+			addr = ApplyMemoryMap(15, prg_banks_32k, addr);
+			return ROM[addr];
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("prg_banks_32k", ref prg_banks_32k);
+			ser.Sync("reg4802", ref reg4802);
+		}
+	}
+}