DEV-793 Support midday/midnight splits of LSM6DSV tagged-FIFO data blocks

The gen-1 accelerometers (LIS2DW12/LSM6DS3) get midday/midnight CSV splits through the generic fixed-size-packet path: each split half byte-advances by dataPacketSize*sampleCount. The LSM6DSV tagged FIFO cannot be walked that way (its raw layout interleaves accel/gyro/mag/timestamp entries behind a count prefix), which is why the byte-offset walk carried a deliberate fail-loud IllegalStateException for split LSM6DSV blocks.

Replaces the guard with an entry-aware split: both halves of a split block are handed the SAME raw block bytes - the LSM6DSV entry parser selects each half's aligned-sample range from the part's metadata-time sampleCount (first half = leading range, second half = trailing range), mag entries are assigned to halves by FIFO arrival order relative to the aligned boundary, and the byte walk advances by nothing for the first half and by the raw on-disk size for the second, keeping every subsequent block aligned. The metadata-time sample-split already worked in the aligned-sample domain and is unchanged.

Validated with an RWC-shifted copy of the DEV-793 B9 recording (GSR 128 Hz + accel 60 Hz straddling 00:00 device time): accel CSV ends 23:59:59.985 / resumes 00:00:00.001 and GSR ends 23:59:59.995 / resumes 00:00:00.003 (one sample period each), and the concatenated split output is byte-for-byte identical to the unsplit parse (58,752 GSR + 26,705 accel rows). Full ASM_PC_00005 suite green (130 tests) - all existing LSM6DSV references bit-identical through the parser refactor.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: marknolan

ShimmerDriver/src/main/java/com/shimmerresearch/verisense/VerisenseDevice.java

@@ -2027,9 +2027,20 @@ private void parseDataBlockDataLsm6dsv(DataBlockDetails dataBlockDetails, byte[]
 		int numEntries = (byteBuffer[currentByteIndex] & 0xFF) | ((byteBuffer[currentByteIndex+1] & 0xFF) << 8);
 		int entriesStart = currentByteIndex + 2;
 
+		boolean accelEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_ACCEL);
+		boolean gyroEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_GYRO);
+		boolean magEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_MAG);
+
+		// The aligned (accel/gyro) reference stream drives per-sample timing and, for
+		// midday/midnight-split blocks, defines each half's share of the FIFO. Each mag
+		// entry records how many reference entries preceded it in the FIFO so it can be
+		// assigned to the correct half by arrival order.
+		int refTag = accelEn ? LSM6DSV_TAG_ACCEL : LSM6DSV_TAG_GYRO;
 		List<byte[]> accelSamples = new ArrayList<byte[]>();
 		List<byte[]> gyroSamples = new ArrayList<byte[]>();
 		List<byte[]> magSamples = new ArrayList<byte[]>();
+		List<Integer> magAlignedPos = new ArrayList<Integer>();
+		int alignedSeen = 0;
 		for(int k=0;k<numEntries;k++) {
 			int eo = entriesStart + k*7;
 			int tag = ((byteBuffer[eo] & 0xFF) >> 3) & 0x1F;
@@ -2038,17 +2049,42 @@ private void parseDataBlockDataLsm6dsv(DataBlockDetails dataBlockDetails, byte[]
 				System.arraycopy(byteBuffer, eo+1, xyz, 0, 6);
 				if(tag==LSM6DSV_TAG_ACCEL) { accelSamples.add(xyz); }
 				else if(tag==LSM6DSV_TAG_GYRO) { gyroSamples.add(xyz); }
-				else { magSamples.add(xyz); }
+				else {
+					magSamples.add(xyz);
+					magAlignedPos.add(alignedSeen);
+				}
+				if(tag==refTag) { alignedSeen++; }
 			}
 			// tag 0x04 (timestamp) intentionally skipped
 		}
 
-		boolean accelEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_ACCEL);
-		boolean gyroEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_GYRO);
-		boolean magEn = isSensorEnabled(Configuration.Verisense.SENSOR_ID.LSM6DSV_MAG);
+		int alignedCountFull = accelEn ? accelSamples.size() : (gyroEn ? gyroSamples.size() : 0);
+
+		// Midday/midnight-split support: both halves of a split block are handed the SAME
+		// raw block bytes (see the byte-offset walk in PayloadContentsDetailsV8orAbove);
+		// each half parses only its own aligned-sample range. The metadata-time split set
+		// each part's sampleCount in the aligned-sample domain.
+		int alignedFrom = 0;
+		int alignedTo = alignedCountFull;
+		if(dataBlockDetails.isFirstPartOfSplitDataBlock()) {
+			alignedTo = Math.min(dataBlockDetails.getSampleCount(), alignedCountFull);
+		} else if(dataBlockDetails.isSecondPartOfSplitDataBlock()) {
+			alignedFrom = Math.max(0, alignedCountFull - dataBlockDetails.getSampleCount());
+		}
+		int alignedCount = alignedTo - alignedFrom;
 
-		int alignedCount = accelEn ? accelSamples.size() : (gyroEn ? gyroSamples.size() : 0);
-		int magCount = magEn ? magSamples.size() : 0;
+		// Mag entries are assigned to a split half by FIFO arrival order relative to the
+		// aligned boundary: an entry that arrived before the first aligned sample of the
+		// second half belongs to the first half.
+		List<byte[]> magSamplesPart = new ArrayList<byte[]>();
+		if(magEn) {
+			for(int i=0;i<magSamples.size();i++) {
+				int pos = magAlignedPos.get(i);
+				boolean inPart = dataBlockDetails.isSecondPartOfSplitDataBlock() ? (pos > alignedFrom) : (pos <= alignedTo);
+				if(inPart) { magSamplesPart.add(magSamples.get(i)); }
+			}
+		}
+		int magCount = magSamplesPart.size();
 		dataBlockDetails.setupOjcArray(alignedCount + magCount);
 
 		// SensorDetails for per-stream enable toggling. Accel + gyro are synchronous (same
@@ -2078,7 +2114,7 @@ private void parseDataBlockDataLsm6dsv(DataBlockDetails dataBlockDetails, byte[]
 				if(magDet!=null) { magDet.setIsEnabled(false); }
 				int alignedPacketSize = getExpectedDataPacketSize(SENSORS.LSM6DSV);
 				double timeMsCurrentSample = startTimeMs;
-				for(int i=0;i<alignedCount;i++) {
+				for(int i=alignedFrom;i<alignedTo;i++) {
 					byte[] byteBuf = new byte[alignedPacketSize];
 					int offset = 0;
 					if(accelEn && i<accelSamples.size()) { System.arraycopy(accelSamples.get(i), 0, byteBuf, offset, 6); }
@@ -2092,7 +2128,7 @@ private void parseDataBlockDataLsm6dsv(DataBlockDetails dataBlockDetails, byte[]
 				}
 			}
 
-			// Pass 2: mag stream (only mag enabled), spread evenly across the block duration
+			// Pass 2: mag stream (only mag enabled), spread evenly across this part's duration
 			if(magCount>0) {
 				if(accelDet!=null) { accelDet.setIsEnabled(false); }
 				if(gyroDet!=null) { gyroDet.setIsEnabled(false); }
@@ -2112,7 +2148,7 @@ private void parseDataBlockDataLsm6dsv(DataBlockDetails dataBlockDetails, byte[]
 				double magTimeMs = startTimeMs;
 				for(int i=0;i<magCount;i++) {
 					byte[] byteBuf = new byte[magPacketSize];
-					System.arraycopy(magSamples.get(i), 0, byteBuf, 0, 6);
+					System.arraycopy(magSamplesPart.get(i), 0, byteBuf, 0, 6);
 					ObjectCluster ojcCurrent = buildMsgForSensorList(byteBuf, commType, dataBlockDetails.listOfSensorClassKeys, magTimeMs);
 					dataHandler(ojcCurrent);
 					dataBlockDetails.setOjcArrayAtIndex(ojcIndex++, ojcCurrent);

ShimmerDriver/src/main/java/com/shimmerresearch/verisense/payloaddesign/PayloadContentsDetailsV8orAbove.java

@@ -420,12 +420,18 @@ public void parsePayloadSensorData() {
 				// dataPacketSize*sampleCount recomputation cannot reproduce).
 				if(dataBlockDetails.isFirstPartOfSplitDataBlock() || dataBlockDetails.isSecondPartOfSplitDataBlock()) {
 					if(dataBlockDetails.datablockSensorId==DATABLOCK_SENSOR_ID.LSM6DSV) {
-						// A split FIFO block cannot be byte-walked from sample counts; supporting
-						// it needs a FIFO-entry-aware split. Fail loudly rather than misparse
-						// every subsequent block (no such recording exists yet - see DEV-793).
-						throw new IllegalStateException("Midday/midnight-split LSM6DSV FIFO data blocks are not supported by the byte-offset walk");
+						// A split tagged-FIFO block cannot be byte-walked from recomputed
+						// sample counts (the raw layout interleaves tag/mag/timestamp
+						// entries). Instead BOTH halves are handed the same raw block bytes
+						// and the LSM6DSV entry parser selects each half's aligned-sample
+						// range - so the first half advances by nothing and the second half
+						// advances by the raw on-disk size, keeping subsequent blocks aligned.
+						if(dataBlockDetails.isSecondPartOfSplitDataBlock()) {
+							currentByteIndex += dataBlockDetails.getQtySensorDataBytesInDatablockRaw();
+						}
+					} else {
+						currentByteIndex += dataBlockDetails.qtySensorDataBytesInDatablock;
 					}
-					currentByteIndex += dataBlockDetails.qtySensorDataBytesInDatablock;
 				} else {
 					currentByteIndex += dataBlockDetails.getQtySensorDataBytesInDatablockRaw();
 				}