Fix a few encoder issues; but while 720kB disks work fine in a real machine,

1440kB disks don't.

arch/ibm/encoder.cc

@@ -6,6 +6,7 @@
 #include "crc.h"
 #include "sectorset.h"
 #include "writer.h"
+#include "fmt/format.h"
 #include <ctype.h>
 
 /* IAM record separator:
@@ -69,7 +70,7 @@ void IbmEncoder::writeRawBits(uint32_t data, int width)
 	{
 		unsigned pos = _cursor - i - 1;
 		if (pos < _bits.size())
-			_bits[pos] = data & 1;
+			_lastBit = _bits[pos] = data & 1;
 		data >>= 1;
 	}
 }
@@ -126,7 +127,6 @@ std::unique_ptr<Fluxmap> IbmEncoder::encode(
 	if (_parameters.emitIam)
 	{
 		writeBytes(_parameters.useFm ? 6 : 12, 0x00);
-		_lastBit = false;
 		if (!_parameters.useFm)
 		{
 			for (int i=0; i<3; i++)
@@ -136,16 +136,17 @@ std::unique_ptr<Fluxmap> IbmEncoder::encode(
 		writeBytes(_parameters.gap1, gapFill);
 	}
 
-	int sectorIndex = 0;
-	while (sectorIndex < _parameters.sectorSkew.size())
+	bool first = true;
+	for (char sectorChar : _parameters.sectorSkew)
 	{
-		if (sectorIndex != 0)
+		int sectorId = charToInt(sectorChar);
+		if (!first)
 			writeBytes(_parameters.gap3, gapFill);
+		first = false;
 
-		int sectorId = charToInt(_parameters.sectorSkew.at(sectorIndex));
 		const auto& sectorData = allSectors.get(physicalTrack, physicalSide, sectorId);
 		if (!sectorData)
-			break;
+			Error() << fmt::format("format tried to find sector {} which wasn't in the input file", sectorId);
 
 		/* Writing the sector and data records are fantastically annoying.
 		 * The CRC is calculated from the *very start* of the record, and
@@ -160,7 +161,6 @@ std::unique_ptr<Fluxmap> IbmEncoder::encode(
 			ByteWriter bw(header);
 
 			writeBytes(_parameters.useFm ? 6 : 12, 0x00);
-			_lastBit = false;
 			if (!_parameters.useFm)
 			{
 				for (int i=0; i<3; i++)
@@ -195,7 +195,6 @@ std::unique_ptr<Fluxmap> IbmEncoder::encode(
 			ByteWriter bw(data);
 
 			writeBytes(_parameters.useFm ? 6 : 12, 0x00);
-			_lastBit = false;
 			if (!_parameters.useFm)
 			{
 				for (int i=0; i<3; i++)
@@ -221,8 +220,6 @@ std::unique_ptr<Fluxmap> IbmEncoder::encode(
 
 			writeBytes(data.slice(conventionalHeaderStart));
 		}
-
-		sectorIndex++;
     }
 
 	if (_cursor >= _bits.size())

src/fe-writeibm.cc

@@ -79,6 +79,7 @@ static ActionFlag preset1440(
 	{ "--ibm-preset-1440" },
 	"Preset parameters to a 3.5\" 1440kB disk.",
 	[] {
+		setWriterDefaultInput(":c=80:h=2:s=18:b=512");
 		trackLengthMs.setDefaultValue(200);
 		sectorSize.setDefaultValue(512);
 		emitIam.setDefaultValue(true);
@@ -88,13 +89,30 @@ static ActionFlag preset1440(
 		gap0.setDefaultValue(80);
 		gap1.setDefaultValue(50);
 		gap2.setDefaultValue(22);
-		gap3.setDefaultValue(54);
+		gap3.setDefaultValue(108);
 		sectorSkew.setDefaultValue("0123456789abcdefgh");
 	});
 
+static ActionFlag preset720(
+	{ "--ibm-preset-720" },
+	"Preset parameters to a 3.5\" 720kB disk.",
+	[] {
+		setWriterDefaultInput(":c=80:h=2:s=9:b=512");
+		trackLengthMs.setDefaultValue(200);
+		sectorSize.setDefaultValue(512);
+		emitIam.setDefaultValue(true);
+		clockRateKhz.setDefaultValue(250);
+		idamByte.setDefaultValue(0x5554);
+		damByte.setDefaultValue(0x5545);
+		gap0.setDefaultValue(80);
+		gap1.setDefaultValue(50);
+		gap2.setDefaultValue(22);
+		gap3.setDefaultValue(80);
+		sectorSkew.setDefaultValue("012345678");
+	});
+
 int mainWriteIbm(int argc, const char* argv[])
 {
-    setWriterDefaultInput(":c=80:h=2:s=18:b=512");
 	setWriterDefaultDest(":d=0:t=0-79:s=0-1");
     flags.parseFlags(argc, argv);
 

tests/fmmfm.cc

@@ -38,6 +38,15 @@ static void testDecode(void)
     ) == Bytes{ 0x80 });
 }
 
+static std::vector<bool> wrappedEncodeMfm(const Bytes& bytes)
+{
+	std::vector<bool> bits(16);
+	unsigned cursor = 0;
+	bool lastBit = false;
+	encodeMfm(bits, cursor, bytes, lastBit);
+	return bits;
+}
+
 static std::vector<bool> wrappedEncodeFm(const Bytes& bytes)
 {
 	std::vector<bool> bits(16);
@@ -46,6 +55,35 @@ static std::vector<bool> wrappedEncodeFm(const Bytes& bytes)
 	return bits;
 }
 
+static void testEncodeMfm(void)
+{
+	assert(wrappedEncodeMfm(Bytes{ 0xa1 })
+		== (std::vector<bool>{
+			false, true,
+			false, false,
+			false, true,
+			false, false,
+			true, false,
+			true, false,
+			true, false,
+			false, true
+		})
+	);
+
+	assert(wrappedEncodeMfm(Bytes{ 0xc2 })
+		== (std::vector<bool>{
+			false, true,
+			false, true,
+			false, false,
+			true, false,
+			true, false,
+			true, false,
+			false, true,
+			false, false
+		})
+	);
+}
+
 static void testEncodeFm(void)
 {
 	assert(wrappedEncodeFm(Bytes{ 0x00 })
@@ -78,6 +116,7 @@ static void testEncodeFm(void)
 int main(int argc, const char* argv[])
 {
 	testDecode();
+	testEncodeMfm();
 	testEncodeFm();
     return 0;
 }