From 02a6df73c5094993fa85a0bc44c1893578836c48 Mon Sep 17 00:00:00 2001
From: tomcw <tomcw@users.noreply.github.com>
Date: Sat, 20 Jan 2018 17:18:24 +0000
Subject: [PATCH] DiskFormat: tweaks and fixed some TODOs in comments

---
 source/DiskDefs.h          |  2 ++
 source/DiskFormatTrack.cpp | 30 +++++++++++++-----------------
 source/DiskFormatTrack.h   |  1 -
 source/DiskImageHelper.cpp | 18 ++++++++++--------
 source/DiskImageHelper.h   |  3 ++-
 5 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/source/DiskDefs.h b/source/DiskDefs.h
index cd89cbf1..90a2e17b 100644
--- a/source/DiskDefs.h
+++ b/source/DiskDefs.h
@@ -1,3 +1,5 @@
 #pragma once
 
 #define NIBBLES_PER_TRACK 0x1A00
+
+const UINT NUM_SECTORS = 16;
diff --git a/source/DiskFormatTrack.cpp b/source/DiskFormatTrack.cpp
index 5e821b04..75ae977e 100644
--- a/source/DiskFormatTrack.cpp
+++ b/source/DiskFormatTrack.cpp
@@ -120,13 +120,13 @@ void FormatTrack::DriveSwitchedToReadMode(Disk_t* const fptr)
 	// Either up to 0x18F0 (if less than 0x18F0) or up to 0x1A00 (for .nib).
 
 	// When there's no spin (enhanced=1), then 0x18F0 is still too long, eg: (see GH#125)
-	//  Gap1 = 0x81, Gap3 = 0x1D (29), TrackSize = 0x1963
-	//  Gap1 = 0x81, Gap3 = 0x1C (28), TrackSize = 0x1954
-	//  Gap1 = 0x81, Gap3 = 0x1B (27), TrackSize = 0x1945
-	//  Gap1 = 0x81, Gap3 = 0x1A (26), TrackSize = 0x1936
+	//  Gap1 = 0x81, Gap2 = 0x05, Gap3 = 0x1D (29), TrackSize = 0x1963
+	//  Gap1 = 0x81, Gap2 = 0x05, Gap3 = 0x1C (28), TrackSize = 0x1954
+	//  Gap1 = 0x81, Gap2 = 0x05, Gap3 = 0x1B (27), TrackSize = 0x1945
+	//  Gap1 = 0x81, Gap2 = 0x05, Gap3 = 0x1A (26), TrackSize = 0x1936
 	//
-	// 0x1936 - 0x81(gap1) = 0x18B5
-	// So need a track size of 0x18B0 (rounding down)
+	// And 0x1936 - 0x81(gap1) = 0x18B5
+	// So need a track size between 0x18B0 (rounding down) and 0x182F
 	const UINT kShortTrackLen = 0x18B0;
 
 	LPBYTE TrackBuffer = fptr->trackimage;
@@ -171,22 +171,18 @@ void FormatTrack::DriveSwitchedToReadMode(Disk_t* const fptr)
 
 void FormatTrack::DriveSwitchedToWriteMode(UINT uTrackIndex)
 {
-	DecodeLatchNibbleReset();
-
-	if (m_bmWrittenSectorAddrFields == 0x0000)	// written no sectors
-	{
-		m_WriteTrackStartIndex = (UINT)-1;		// wait for 1st write 
-	}
-}
-
-void FormatTrack::DecodeLatchNibbleReset(void)
-{
-	// ProDOS: switches to write mode between Address Field & Gap2; and between Data Field & Gap3
+	// ProDOS/DOS3.3: during track write, switches to read mode then back to write mode:
+	// . between Address Field & Gap2; and between Data Field & Gap3
 	// . so if at TS_GAP2_START then stay at TS_GAP2_START
 	if (m_trackState != TS_GAP2_START)
 		m_trackState = (m_bmWrittenSectorAddrFields == 0x0000) ? TS_GAP1 : TS_GAP3;
 	m_uLast3Bytes = 0;
 	m_4and4idx = 0;
+
+	if (m_bmWrittenSectorAddrFields == 0x0000)	// written no sectors
+	{
+		m_WriteTrackStartIndex = (UINT)-1;		// wait for 1st write 
+	}
 }
 
 // This is just for debug/logging: used to output when a new Address Field has been read
diff --git a/source/DiskFormatTrack.h b/source/DiskFormatTrack.h
index 1c03fb04..4db08d29 100644
--- a/source/DiskFormatTrack.h
+++ b/source/DiskFormatTrack.h
@@ -43,7 +43,6 @@ public:
 	void LoadSnapshot(class YamlLoadHelper& yamlLoadHelper);
 
 private:
-	void DecodeLatchNibbleReset(void);
 	void UpdateOnWriteLatch(UINT uSpinNibbleCount, const Disk_t* const fptr);
 	void DecodeLatchNibble(BYTE floppylatch, BOOL bIsWrite);
 
diff --git a/source/DiskImageHelper.cpp b/source/DiskImageHelper.cpp
index a9d7f453..56b9f688 100644
--- a/source/DiskImageHelper.cpp
+++ b/source/DiskImageHelper.cpp
@@ -419,8 +419,8 @@ void CImageBase::DenibblizeTrack(LPBYTE trackimage, SectorOrder_e SectorOrder, i
 #endif
 
 	int offset    = 0;
-	int partsleft = 33;		// TODO-TC: 32 = 16*2 prologues
-	int sector    = 0;
+	int partsleft = NUM_SECTORS*2+1;	// TC: 32+1 prologues - need 1 extra if trackimage starts between Addr Field & Data Field
+	int sector    = -1;
 	while (partsleft--)
 	{
 		BYTE byteval[3] = {0,0,0};
@@ -454,8 +454,8 @@ void CImageBase::DenibblizeTrack(LPBYTE trackimage, SectorOrder_e SectorOrder, i
 						| (*(ms_pWorkBuffer+TRACK_DENIBBLIZED_SIZE+5) & 0x55);
 
 #ifdef _DEBUG
-				_ASSERT( sector <= 15 );
-				if (partsleft != 0)	// Don't need this if partsleft is initialised to 32 (not 33)
+				_ASSERT( sector < NUM_SECTORS );
+				if (partsleft != 0)
 				{
 					_ASSERT( (bmWrittenSectorAddrFields & (1<<sector)) == 0 );
 					bmWrittenSectorAddrFields |= (1<<sector);
@@ -464,12 +464,14 @@ void CImageBase::DenibblizeTrack(LPBYTE trackimage, SectorOrder_e SectorOrder, i
 			}
 			else if (byteval[2] == 0xAD)
 			{
+				if (sector >= 0 && sector < NUM_SECTORS)
+				{
 #ifdef _DEBUG
-				uWriteDataFieldPrologueCount++;
-				_ASSERT(uWriteDataFieldPrologueCount <= 16);
+					uWriteDataFieldPrologueCount++;
+					_ASSERT(uWriteDataFieldPrologueCount <= NUM_SECTORS);
 #endif
-
-				Decode62(ms_pWorkBuffer+(ms_SectorNumber[SectorOrder][sector] << 8));
+					Decode62(ms_pWorkBuffer+(ms_SectorNumber[SectorOrder][sector] << 8));
+				}
 				sector = 0;
 			}
 		}
diff --git a/source/DiskImageHelper.h b/source/DiskImageHelper.h
index 01a07b49..2b8a8a4d 100644
--- a/source/DiskImageHelper.h
+++ b/source/DiskImageHelper.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "DiskDefs.h"
 #include "zip.h"
 
 #define GZ_SUFFIX ".gz"
@@ -90,7 +91,7 @@ public:
 
 protected:
 	static BYTE ms_DiskByte[0x40];
-	static BYTE ms_SectorNumber[NUM_SECTOR_ORDERS][0x10];
+	static BYTE ms_SectorNumber[NUM_SECTOR_ORDERS][NUM_SECTORS];
 	BYTE m_uVolumeNumber;
 };