From 448ee2f09f1c1bc67555ff2c8be45e368dea028c Mon Sep 17 00:00:00 2001
From: "Adrian.Conlon" <adrian.conlon@gmail.com>
Date: Thu, 24 Aug 2017 10:28:31 +0100
Subject: [PATCH] Refactor the MBC implementation to allow a single point of
 definition.

Signed-off-by: Adrian.Conlon <adrian.conlon@gmail.com>
---
 LR35902/inc/Bus.h   |  4 +++-
 LR35902/src/Bus.cpp | 36 ++++++++++++++++--------------------
 inc/Memory.h        |  4 ++--
 inc/Processor.h     |  2 +-
 src/Memory.cpp      |  4 ++--
 5 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/LR35902/inc/Bus.h b/LR35902/inc/Bus.h
index 5651afa..c215723 100644
--- a/LR35902/inc/Bus.h
+++ b/LR35902/inc/Bus.h
@@ -182,7 +182,7 @@ namespace EightBit {
 		void loadBootRom(const std::string& path);
 		void loadGameRom(const std::string& path);
 
-		virtual uint8_t peek(uint16_t address) const;
+		virtual uint8_t peek(uint16_t address);
 		virtual void poke(uint16_t address, uint8_t value);
 
 		virtual uint8_t& reference();
@@ -213,5 +213,7 @@ namespace EightBit {
 		void checkTimer(int cycles);
 
 		void validateCartridgeType();
+
+		uint8_t& reference(uint16_t address, bool& rom);
 	};
 }
\ No newline at end of file
diff --git a/LR35902/src/Bus.cpp b/LR35902/src/Bus.cpp
index 4e697d1..fc9687a 100644
--- a/LR35902/src/Bus.cpp
+++ b/LR35902/src/Bus.cpp
@@ -40,18 +40,8 @@ void EightBit::Bus::loadGameRom(const std::string& path) {
 	validateCartridgeType();
 }
 
-uint8_t& EightBit::Bus::reference() {
-	auto effective = effectiveAddress(ADDRESS().word);
-	if ((effective < 0x100) && bootRomEnabled())
-		return placeDATA(m_bootRom[effective]);
-	if ((effective < 0x4000) && gameRomEnabled())
-		return placeDATA(m_gameRom[effective]);
-	if ((effective < 0x8000) && gameRomEnabled())
-		return placeDATA(m_gameRom[effective + (m_romBank * 0x4000)]);
-	return Memory::reference();
-}
-
-uint8_t EightBit::Bus::peek(uint16_t address) const {
+uint8_t& EightBit::Bus::reference(uint16_t address, bool& rom) {
+	rom = true;
 	auto effective = effectiveAddress(address);
 	if ((effective < 0x100) && bootRomEnabled())
 		return m_bootRom[effective];
@@ -59,18 +49,24 @@ uint8_t EightBit::Bus::peek(uint16_t address) const {
 		return m_gameRom[effective];
 	if ((effective < 0x8000) && gameRomEnabled())
 		return m_gameRom[effective + (m_romBank * 0x4000)];
+	rom = false;
 	return m_bus[effective];
 }
 
+uint8_t& EightBit::Bus::reference() {
+	bool rom;
+	auto& value = reference(ADDRESS().word, rom);
+	return rom ? placeDATA(value) : referenceDATA(value);
+}
+
+uint8_t EightBit::Bus::peek(uint16_t address) {
+	bool rom;
+	return reference(address, rom);
+}
+
 void EightBit::Bus::poke(uint16_t address, uint8_t value) {
-	auto effective = effectiveAddress(address);
-	if ((effective < 0x100) && bootRomEnabled())
-		m_bootRom[effective] = value;
-	if ((effective < 0x4000) && gameRomEnabled())
-		m_gameRom[effective] = value;
-	if ((effective < 0x8000) && gameRomEnabled())
-		m_gameRom[effective + (m_romBank * 0x4000)] = value;
-	m_bus[effective] = value;
+	bool rom;
+	reference(address, rom) = value;
 }
 
 void EightBit::Bus::Bus_WrittenByte(const AddressEventArgs& e) {
diff --git a/inc/Memory.h b/inc/Memory.h
index 488ed44..70216d7 100644
--- a/inc/Memory.h
+++ b/inc/Memory.h
@@ -53,10 +53,10 @@ namespace EightBit {
 			return DATA();
 		}
 
-		virtual uint8_t peek(uint16_t address) const;
+		virtual uint8_t peek(uint16_t address);
 		virtual void poke(uint16_t address, uint8_t value);
 
-		virtual uint16_t peekWord(uint16_t address) const;
+		virtual uint16_t peekWord(uint16_t address);
 
 		virtual int effectiveAddress(int address) const {
 			return address & m_addressMask;
diff --git a/inc/Processor.h b/inc/Processor.h
index 1bb556f..9dae3af 100644
--- a/inc/Processor.h
+++ b/inc/Processor.h
@@ -44,7 +44,7 @@ namespace EightBit {
 		static int promoteNibble(int value) { return value << 4; }
 		static int demoteNibble(int value) { return highNibble(value); }
 
-		const Memory& getMemory() const { return m_memory; }
+		Memory& getMemory() { return m_memory; }
 
 		register16_t& PC() { return pc; }
 
diff --git a/src/Memory.cpp b/src/Memory.cpp
index 73d8815..3e486f5 100644
--- a/src/Memory.cpp
+++ b/src/Memory.cpp
@@ -19,7 +19,7 @@ EightBit::Memory::Memory(uint16_t addressMask)
 EightBit::Memory::~Memory() {
 }
 
-uint8_t EightBit::Memory::peek(uint16_t address) const {
+uint8_t EightBit::Memory::peek(uint16_t address) {
 	return m_bus[address];
 }
 
@@ -27,7 +27,7 @@ void EightBit::Memory::poke(uint16_t address, uint8_t value) {
 	m_bus[address] = value;
 }
 
-uint16_t EightBit::Memory::peekWord(uint16_t address) const {
+uint16_t EightBit::Memory::peekWord(uint16_t address) {
 	register16_t returned;
 	returned.low = peek(address);
 	returned.high = peek(address + 1);