Intellivision - add System Ram and Executive Rom memory domains

BizHawk.Emulation.Cores/Consoles/Intellivision/Intellivision.IMemoryDomains.cs

@@ -36,10 +36,60 @@ namespace BizHawk.Emulation.Cores.Intellivision
 					addr => GraphicsRom[addr],
 					(addr, value) => GraphicsRom[addr] = value,
 					1),
+				new MemoryDomainDelegate(
+					"System Ram",
+					SystemRam.Length * 2,
+					MemoryDomain.Endian.Little,
+					addr => ReadByteFromShortArray(addr, SystemRam),
+					(addr, value) => WriteByteToShortArray(addr, value, SystemRam),
+					1
+				),
+				new MemoryDomainDelegate(
+					"Executive Rom",
+					SystemRam.Length * 2,
+					MemoryDomain.Endian.Little,
+					addr => ReadByteFromShortArray(addr, ExecutiveRom),
+					(addr, value) => WriteByteToShortArray(addr, value, ExecutiveRom),
+					1
+				)
 			};
 
 			MemoryDomains = new MemoryDomainList(domains);
 			(ServiceProvider as BasicServiceProvider).Register<IMemoryDomains>(MemoryDomains);
 		}
+
+		// TODO: move these to a common library and maybe add an endian parameter
+		// Little endian
+		private byte ReadByteFromShortArray(long addr, ushort[] array)
+		{
+			if (addr % 2 == 0)
+			{
+				long index = addr / 2;
+				return (byte)(array[index] >> 8);
+				
+			}
+			else
+			{
+				long index = (addr - 1) / 2;
+				return (byte)(array[index] & 0xFF);
+			}
+		}
+
+		private void WriteByteToShortArray(long addr, byte value, ushort[] array)
+		{
+			if (addr % 2 == 0)
+			{
+				long index = (addr - 1) / 2;
+				ushort val = (ushort)((value << 8) + (array[index] & 0xFF));
+				array[index] = val;
+
+			}
+			else
+			{
+				long index = addr / 2;
+				ushort val = (ushort)((((array[index] >> 8) & 0xFF) << 8) + value);
+				array[index] = val;
+			}
+		}
 	}
 }