gba: add system bus memory domain

BizHawk.Emulation/Consoles/Nintendo/GBA/LibMeteor.cs

@@ -210,6 +210,20 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 		[DllImport("libmeteor.dll", CallingConvention = CallingConvention.Cdecl)]
 		public static extern bool libmeteor_loadstate(byte[] data, uint size);
 
+		/// <summary>
+		/// read a byte off the system bus.  guaranteed to have no side effects
+		/// </summary>
+		/// <param name="addr"></param>
+		/// <returns></returns>
+		[DllImport("libmeteor.dll", CallingConvention = CallingConvention.Cdecl)]
+		public static extern byte libmeteor_peekbus(uint addr);
 
+		/// <summary>
+		/// write a byte to the system bus.
+		/// </summary>
+		/// <param name="addr"></param>
+		/// <param name="val"></param>
+		[DllImport("libmeteor.dll", CallingConvention = CallingConvention.Cdecl)]
+		public static extern void libmeteor_writebus(uint addr, byte val);
 	}
 }

BizHawk.Emulation/Consoles/Nintendo/GBA/Meteor.cs

@@ -230,6 +230,17 @@ namespace BizHawk.Emulation.Consoles.Nintendo.GBA
 			AddMemoryDomain(LibMeteor.MemoryArea.oam, 1024, "OAM");
 			// even if the rom is less than 32MB, the whole is still valid in meteor
 			AddMemoryDomain(LibMeteor.MemoryArea.rom, 32 * 1024 * 1024, "ROM");
+			// special domain for system bus
+			MemoryDomain sb = new MemoryDomain("BUS", 1 << 28, Endian.Little,
+				delegate(int addr)
+				{
+					return LibMeteor.libmeteor_peekbus((uint)addr);
+				},
+				delegate(int addr, byte val)
+				{
+					LibMeteor.libmeteor_writebus((uint)addr, val);
+				});
+			_MemoryDomains.Add(sb);
 		}
 
 		#endregion

libmeteor/cinterface.cpp

@@ -202,5 +202,13 @@ EXPORT int libmeteor_loadstate(const void *data, unsigned size)
 	return AMeteor::LoadState(ss);
 }
 
-// TODO: cartram and system bus memory domains
+// TODO: cartram memory domain, cartram in system bus memory domain
+EXPORT uint8_t libmeteor_peekbus(uint32_t addr)
+{
+	return AMeteor::_memory.Peek8(addr);
+}
 
+EXPORT void libmeteor_writebus(uint32_t addr, uint8_t val)
+{
+	AMeteor::_memory.Write8(addr, val);
+}

libmeteor/include/ameteor/memory.hpp

@@ -115,6 +115,8 @@ namespace AMeteor
 			bool SaveState (std::ostream& stream);
 			bool LoadState (std::istream& stream);
 
+			uint8_t Peek8 (uint32_t add);
+
 			// TODO make const members
 			uint8_t Read8 (uint32_t add);
 			uint16_t Read16 (uint32_t add);

libmeteor/source/memory.cpp

@@ -583,6 +583,24 @@ namespace AMeteor
 // Read
 ////////////////////////////////////////////////////////////////////////////////
 
+	uint8_t Memory::Peek8 (uint32_t add)
+	{
+		switch (add >> 24)
+		{
+		case 0x04:
+			if (add < 0x04001000)
+				return IO.DRead8(add & 0xfff);
+			else
+				return 0;
+		case 0x0e:
+			// todo: cart reading
+			return 0xff;
+		default:
+			uint8_t *r = (uint8_t*)GetRealAddress(add, 1);
+			return r ? *r : 0;
+		}
+	}
+
 	uint8_t Memory::Read8 (uint32_t add)
 	{
 		switch (add >> 24)