Merge pull request #127 from davidgiven/fixing

Fix an issue where HD IBM disks can't be read

arch/ibm/decoder.cc

@@ -73,8 +73,10 @@ const FluxPattern FM_TRS80DAM2_PATTERN(16, 0xf56c);
  * encoding (you can't do 10 00). So this can't be spoofed by user data.
  * 
  * shifted: 10 00 10 01 00 01 00 1
+ * 
+ * It's repeated three times.
  */
-const FluxPattern MFM_PATTERN(16, 0x4489);
+const FluxPattern MFM_PATTERN(48, 0x448944894489LL);
 
 const FluxMatchers ANY_RECORD_PATTERN(
     {
@@ -100,7 +102,8 @@ AbstractDecoder::RecordType IbmDecoder::advanceToNextRecord()
     if (_currentHeaderLength > 0)
         readRawBits(_currentHeaderLength*16);
     auto idbits = readRawBits(16);
-    uint8_t id = decodeFmMfm(idbits).slice(0, 1)[0];
+    const Bytes idbytes = decodeFmMfm(idbits);
+    uint8_t id = idbytes.slice(0, 1)[0];
     seek(here);
 
     switch (id)

lib/decoders/decoders.cc

@@ -52,13 +52,11 @@ void AbstractDecoder::decodeToSectors(Track& track)
             sector.headerStartTime = recordStart.ns();
             sector.headerEndTime = recordEnd.ns();
             r = advanceToNextRecord();
+            recordStart = fmr.tell();
             if (r == DATA_RECORD)
-            {
-                recordStart = fmr.tell();
                 decodeDataRecord();
-                recordEnd = fmr.tell();
-                pushRecord(recordStart, recordEnd);
-            }
+            recordEnd = fmr.tell();
+            pushRecord(recordStart, recordEnd);
         }
         sector.dataStartTime = recordStart.ns();
         sector.dataEndTime = recordEnd.ns();

lib/decoders/fluxmapreader.cc

@@ -25,6 +25,11 @@ static DoubleFlag clockIntervalBias(
     "Adjust intervals between pulses by this many clocks before decoding.",
     -0.02);
 
+static DoubleFlag minimumClockUs(
+    { "--minimum-clock-us" },
+    "Refuse to detect clocks shorter than this, to avoid false positives.",
+    0.75);
+
 int FluxmapReader::readOpcode(unsigned& ticks)
 {
     ticks = 0;
@@ -222,7 +227,9 @@ nanoseconds_t FluxmapReader::seekToPattern(const FluxMatcher& pattern, const Flu
             seek(positions[intervalCount-match.intervals]);
             _pos.zeroes = match.zeroes;
             matching = match.matcher;
-            return match.clock * NS_PER_TICK;
+            nanoseconds_t detectedClock = match.clock * NS_PER_TICK;
+            if (detectedClock > (minimumClockUs*1000))
+                return match.clock * NS_PER_TICK;
         }
 
         for (unsigned i=0; i<intervalCount; i++)

lib/reader.cc

@@ -227,8 +227,8 @@ void readDiskCommand(AbstractDecoder& decoder)
 			std::cout << "\nRaw (undecoded) records follow:\n\n";
 			for (auto& record : track->rawrecords)
 			{
-				std::cout << fmt::format("I+{:.2f}us", record.position.ns() / 1000.0)
-						<< std::endl;
+				std::cout << fmt::format("I+{:.2f}us with {:.2f}us clock\n",
+                            record.position.ns() / 1000.0, record.clock / 1000.0);
 				hexdump(std::cout, record.data);
 				std::cout << std::endl;
 			}