From 6fb5b3b0e8c511251d4a18b6cb4141b2f0764e16 Mon Sep 17 00:00:00 2001
From: tomcw <tomcw@users.noreply.github.com>
Date: Sat, 10 Nov 2018 10:30:19 +0000
Subject: [PATCH] Refactor: consolidate 'modechanging' optimisations into a
 single function

---
 source/LanguageCard.cpp | 18 ++------------
 source/Memory.cpp       | 53 +++++++++++++++++++++++++----------------
 source/Memory.h         |  2 +-
 3 files changed, 36 insertions(+), 37 deletions(-)

diff --git a/source/LanguageCard.cpp b/source/LanguageCard.cpp
index 2ae13fc3..24d3c64e 100644
--- a/source/LanguageCard.cpp
+++ b/source/LanguageCard.cpp
@@ -85,22 +85,8 @@ BYTE __stdcall LanguageCardUnit::IO(WORD PC, WORD uAddr, BYTE bWrite, BYTE uValu
 
 	//
 
-	if (IS_APPLE2E)
-	{
-		// IF THE EMULATED PROGRAM HAS JUST UPDATED THE MEMORY WRITE MODE AND IS
-		// ABOUT TO UPDATE THE MEMORY READ MODE, HOLD OFF ON ANY PROCESSING UNTIL
-		// IT DOES SO.
-		//
-		// NB. A 6502 interrupt occurring between these memory write & read updates could lead to incorrect behaviour.
-		// - although any data-race is probably a bug in the 6502 code too.
-		if ((PC < 0xC000) &&
-			(((*(LPDWORD)(mem+PC) & 0x00FFFEFF) == 0x00C0048D) ||	// Next: STA $C004 or STA $C005
-			 ((*(LPDWORD)(mem+PC) & 0x00FFFEFF) == 0x00C0028D)))	// Next: STA $C002 or STA $C003
-		{
-				SetModeChanging(1);
-				return bWrite ? 0 : MemReadFloatingBus(nExecutedCycles);
-		}
-	}
+	if (MemOptimizeForModeChanging(PC, uAddr))
+		return bWrite ? 0 : MemReadFloatingBus(nExecutedCycles);
 
 	// IF THE MEMORY PAGING MODE HAS CHANGED, UPDATE OUR MEMORY IMAGES AND
 	// WRITE TABLES.
diff --git a/source/Memory.cpp b/source/Memory.cpp
index da8caa25..0799589e 100644
--- a/source/Memory.cpp
+++ b/source/Memory.cpp
@@ -972,11 +972,6 @@ static bool IsCardInSlot(const UINT uSlot)
 
 //===========================================================================
 
-void SetModeChanging(BOOL value)
-{
-	modechanging = value;
-}
-
 DWORD GetMemMode(void)
 {
 	return memmode;
@@ -1953,21 +1948,8 @@ BYTE __stdcall MemSetPaging(WORD programcounter, WORD address, BYTE write, BYTE
 		}
 	}
 
-	if (IS_APPLE2E)
-	{
-		// IF THE EMULATED PROGRAM HAS JUST UPDATED THE MEMORY WRITE MODE AND IS
-		// ABOUT TO UPDATE THE MEMORY READ MODE, HOLD OFF ON ANY PROCESSING UNTIL
-		// IT DOES SO.
-		//
-		// NB. A 6502 interrupt occurring between these memory write & read updates could lead to incorrect behaviour.
-		// - although any data-race is probably a bug in the 6502 code too.
-		if ((address >= 4) && (address <= 5) &&
-			((*(LPDWORD)(mem+programcounter) & 0x00FFFEFF) == 0x00C0028D))		// Next: STA $C002 or STA $C003
-		{
-				modechanging = 1;
-				return 0;	// For $C004 & $C005: entry to this func is always via a write to $C004 or $C005
-		}
-	}
+	if (MemOptimizeForModeChanging(programcounter, address))
+		return write ? 0 : MemReadFloatingBus(nExecutedCycles);
 
 	// IF THE MEMORY PAGING MODE HAS CHANGED, UPDATE OUR MEMORY IMAGES AND
 	// WRITE TABLES.
@@ -2012,6 +1994,37 @@ BYTE __stdcall MemSetPaging(WORD programcounter, WORD address, BYTE write, BYTE
 
 //===========================================================================
 
+bool MemOptimizeForModeChanging(WORD programcounter, WORD address)
+{
+	if (IS_APPLE2E)
+	{
+		// IF THE EMULATED PROGRAM HAS JUST UPDATED THE MEMORY WRITE MODE AND IS
+		// ABOUT TO UPDATE THE MEMORY READ MODE, HOLD OFF ON ANY PROCESSING UNTIL
+		// IT DOES SO.
+		//
+		// NB. A 6502 interrupt occurring between these memory write & read updates could lead to incorrect behaviour.
+		// - although any data-race is probably a bug in the 6502 code too.
+		if ((address >= 4) && (address <= 5) &&									// Now:  RAMWRTOFF or RAMWRTON
+			((*(LPDWORD)(mem+programcounter) & 0x00FFFEFF) == 0x00C0028D))		// Next: STA $C002(RAMRDOFF) or STA $C003(RAMRDON)
+		{
+				modechanging = 1;
+				return true;
+		}
+
+		if ((address >= 0x80) && (address <= 0x8F) && (programcounter < 0xC000) &&	// Now: LC
+			(((*(LPDWORD)(mem+programcounter) & 0x00FFFEFF) == 0x00C0048D) ||		// Next: STA $C004(RAMWRTOFF) or STA $C005(RAMWRTON)
+			 ((*(LPDWORD)(mem+programcounter) & 0x00FFFEFF) == 0x00C0028D)))		//    or STA $C002(RAMRDOFF)  or STA $C003(RAMRDON)
+		{
+				modechanging = 1;
+				return true;
+		}
+	}
+
+	return false;
+}
+
+//===========================================================================
+
 LPVOID MemGetSlotParameters(UINT uSlot)
 {
 	_ASSERT(uSlot < NUM_SLOTS);
diff --git a/source/Memory.h b/source/Memory.h
index 6538ae01..7ae9c469 100644
--- a/source/Memory.h
+++ b/source/Memory.h
@@ -66,7 +66,7 @@ LPBYTE  MemGetBankPtr(const UINT nBank);
 LPBYTE  MemGetCxRomPeripheral();
 DWORD   GetMemMode(void);
 void    SetMemMode(DWORD memmode);
-void	SetModeChanging(BOOL value);
+bool	MemOptimizeForModeChanging(WORD programcounter, WORD address);
 bool    MemIsAddrCodeMemory(const USHORT addr);
 void    MemInitialize ();
 void    MemInitializeROM(void);