From 35d7c11f918e79f2e244afd32c6e9f71bb275a20 Mon Sep 17 00:00:00 2001
From: AJR <ariedlmayer@gmail.com>
Date: Wed, 20 Nov 2024 18:28:31 -0500
Subject: vt_dsk: Regression fixes for loading and saving both disk formats -
 Remember to put in a flux change at the start of each bit - Revert
 flux_to_image bitstream generator to as it was before
 08f28cee11ce94e6656d4924c7a3c30614811783 (new version simply didn't work)

---
 src/lib/formats/vt_dsk.cpp | 45 +++++++++++++++++++--------------------------
 1 file changed, 19 insertions(+), 26 deletions(-)

diff --git a/src/lib/formats/vt_dsk.cpp b/src/lib/formats/vt_dsk.cpp
index 8792ba86525..040d24b4fb9 100644
--- a/src/lib/formats/vt_dsk.cpp
+++ b/src/lib/formats/vt_dsk.cpp
@@ -21,6 +21,7 @@
 
 void vtech_common_format::wbit(std::vector<uint32_t> &buffer, uint32_t &pos, bool bit)
 {
+	buffer.push_back(pos | floppy_image::MG_F);
 	if(bit) {
 		pos += 2237;
 		buffer.push_back(pos | floppy_image::MG_F);
@@ -93,37 +94,29 @@ std::vector<uint8_t> vtech_common_format::flux_to_image(const floppy_image &imag
 			continue;
 
 		std::vector<bool> bitstream;
-		int cpos = 0;
-		while((buffer[cpos] & floppy_image::MG_MASK) != floppy_image::MG_F) {
-			cpos++;
-			if(cpos == sz) {
-				cpos = -1;
-				break;
+		int lpos = -1;
+		bool looped = !((buffer[sz-1] ^ buffer[0]) & floppy_image::MG_MASK);
+		int cpos = looped ? sz-1 : 0;
+		while(cpos != lpos) {
+			int dt = looped && cpos == sz-1 ? (200000000 - (buffer[cpos] & floppy_image::TIME_MASK)) + (buffer[1] & floppy_image::TIME_MASK) :
+				cpos == sz-1 ? 200000000 - (buffer[cpos] & floppy_image::TIME_MASK) :
+				(buffer[cpos+1] & floppy_image::TIME_MASK) - (buffer[cpos] & floppy_image::TIME_MASK);
+			int t = dt >= 9187 - 143 ? 0 :
+				dt >= 2237 - 143 && dt <= 2237 + 143 ? 1 :
+				2;
+			if(t <= 1) {
+				if(lpos == -1)
+					lpos = cpos;
+				bitstream.push_back(t);
 			}
-		}
-		if(cpos == -1)
-			continue;
-		for(;;) {
-			int npos = cpos;
-			for(;;) {
-				npos++;
-				if(npos == sz)
-					npos = 0;
-				if((buffer[npos] & floppy_image::MG_MASK) == floppy_image::MG_F)
-					break;
-			}
-			int dt = (buffer[npos] & floppy_image::TIME_MASK) - (buffer[cpos] & floppy_image::TIME_MASK);
-			if(dt < 0)
-				cpos += 200000000;
-			bitstream.push_back(dt < 9187 - 143);
-			if(npos <= cpos)
-				break;
-			cpos = npos;
+			cpos += 1;
+			if(cpos == sz)
+				cpos = looped ? 1 : 0;
 		}
 		int mode = 0;
 		int pos = 0;
 		int count = 0;
-		bool looped = false;
+		looped = false;
 		uint8_t *dest = nullptr;
 		[[maybe_unused]] uint16_t checksum = 0;
 		uint64_t buf = 0;
-- 
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