Add Implicit Index Support

jhdf/src/main/java/io/jhdf/Utils.java

@@ -456,4 +456,15 @@ private static void flattenInternal(Object data, List<Object> flat) {
 			flat.add(data);
 		}
 	}
+
+	public static int totalChunks(int[] datasetDimensions, int[] chunkDimensions) {
+		int chunks = 1;
+		for (int i = 0; i < datasetDimensions.length; i++) {
+			int chunksInDim = datasetDimensions[i] / chunkDimensions[i];
+			// If there is a partial chunk then we need to add one chunk in this dim
+			if(datasetDimensions[i] % chunkDimensions[i] != 0 ) chunksInDim++;
+			chunks *=  chunksInDim;
+		}
+		return chunks;
+	}
 }

jhdf/src/main/java/io/jhdf/dataset/chunked/ChunkedDatasetV4.java

@@ -17,9 +17,9 @@
 import io.jhdf.dataset.chunked.indexing.EmptyChunkIndex;
 import io.jhdf.dataset.chunked.indexing.ExtensibleArrayIndex;
 import io.jhdf.dataset.chunked.indexing.FixedArrayIndex;
+import io.jhdf.dataset.chunked.indexing.ImplicitChunkIndex;
 import io.jhdf.dataset.chunked.indexing.SingleChunkIndex;
 import io.jhdf.exceptions.HdfException;
-import io.jhdf.exceptions.UnsupportedHdfException;
 import io.jhdf.object.message.DataLayoutMessage.ChunkedDataLayoutMessageV4;
 import io.jhdf.storage.HdfBackingStorage;
 import org.apache.commons.lang3.ArrayUtils;
@@ -85,7 +85,9 @@ protected Map<ChunkOffset, Chunk> initialize() {
 						chunkIndex = new SingleChunkIndex(layoutMessage, datasetInfo);
 						break;
 					case 2: // Implicit
-						throw new UnsupportedHdfException("Implicit indexing is currently not supported");
+						logger.debug("Reading implicit indexed dataset");
+						chunkIndex = new ImplicitChunkIndex(layoutMessage.getAddress(), datasetInfo);
+						break;
 					case 3: // Fixed array
 						logger.debug("Reading fixed array indexed dataset");
 						chunkIndex = new FixedArrayIndex(hdfBackingStorage, layoutMessage.getAddress(), datasetInfo);

jhdf/src/main/java/io/jhdf/dataset/chunked/indexing/ImplicitChunkIndex.java

@@ -0,0 +1,46 @@
+/*
+ * This file is part of jHDF. A pure Java library for accessing HDF5 files.
+ *
+ * https://jhdf.io
+ *
+ * Copyright (c) 2024 James Mudd
+ *
+ * MIT License see 'LICENSE' file
+ */
+package io.jhdf.dataset.chunked.indexing;
+
+import io.jhdf.Utils;
+import io.jhdf.dataset.chunked.Chunk;
+import io.jhdf.dataset.chunked.DatasetInfo;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public class ImplicitChunkIndex implements ChunkIndex {
+
+	private final int chunkSize;
+	private final int[] datasetDimensions;
+	private final int[] chunkDimensions;
+	private final long baseAddress;
+
+	public ImplicitChunkIndex(long baseAddress, DatasetInfo datasetInfo) {
+		this.baseAddress = baseAddress;
+		this.chunkSize = datasetInfo.getChunkSizeInBytes();
+		this.datasetDimensions = datasetInfo.getDatasetDimensions();
+		this.chunkDimensions = datasetInfo.getChunkDimensions();
+	}
+
+	@Override
+	public Collection<Chunk> getAllChunks() {
+		int totalChunks = Utils.totalChunks(datasetDimensions, chunkDimensions);
+		List<Chunk> chunks = new ArrayList<>(totalChunks);
+		for (int i = 0; i < totalChunks; i++) {
+			chunks.add(new ChunkImpl(baseAddress + i* chunkSize,
+				chunkSize,
+				Utils.chunkIndexToChunkOffset(i, chunkDimensions, datasetDimensions)));
+		}
+		return chunks;
+	}
+
+}

jhdf/src/test/java/io/jhdf/dataset/chunked/indexing/ImplicitIndexTest.java

@@ -0,0 +1,57 @@
+/*
+ * This file is part of jHDF. A pure Java library for accessing HDF5 files.
+ *
+ * https://jhdf.io
+ *
+ * Copyright (c) 2024 James Mudd
+ *
+ * MIT License see 'LICENSE' file
+ */
+package io.jhdf.dataset.chunked.indexing;
+
+import io.jhdf.HdfFile;
+import io.jhdf.api.Dataset;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import static io.jhdf.TestUtils.loadTestHdfFile;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+class ImplicitIndexTest {
+
+	private static final String HDF5_TEST_FILE_NAME = "implicit_index_datasets.hdf5";
+
+	private static HdfFile hdfFile;
+
+	@BeforeAll
+	static void setup() throws Exception {
+		hdfFile = loadTestHdfFile(HDF5_TEST_FILE_NAME);
+	}
+
+	@AfterAll
+	static void tearDown() {
+		hdfFile.close();
+	}
+
+	@Test
+	void testDataReadCorrectly() {
+		// Unfiltered
+		Dataset implicitIndex = hdfFile.getDatasetByPath("implicit_index_exact");
+		int[] implicitIndexDataFlat = (int[]) implicitIndex.getDataFlat();
+		assertThat(implicitIndexDataFlat).isEqualTo(expectedData(Math.toIntExact(implicitIndex.getSize())));
+
+		Dataset indexMismatch = hdfFile.getDatasetByPath("implicit_index_mismatch");
+		int[] indexMismatchDataFlat = (int[]) indexMismatch.getDataFlat();
+		assertThat(indexMismatchDataFlat).isEqualTo(expectedData(Math.toIntExact(indexMismatch.getSize())));
+
+	}
+
+	private int[] expectedData(int length) {
+		int[] data = new int[length];
+		for (int i = 0; i < length; i++) {
+			data[i] = i;
+		}
+		return data;
+	}
+}

jhdf/src/test/resources/scripts/implicit_index_datasets.py

@@ -0,0 +1,56 @@
+# -------------------------------------------------------------------------------
+# This file is part of jHDF. A pure Java library for accessing HDF5 files.
+#
+# https://jhdf.io
+#
+# Copyright (c) 2024 James Mudd
+#
+# MIT License see 'LICENSE' file
+# -------------------------------------------------------------------------------
+import h5py
+import numpy
+
+f = h5py.File("implicit_index_datasets.hdf5", "w",  libver='latest')
+
+data = numpy.arange(20)
+
+dataspace = h5py.h5s.create_simple(data.shape)  # Create simple dataspace
+datatype = h5py.h5t.NATIVE_INT32
+
+# Dataset creation property list
+dcpl = h5py.h5p.create(h5py.h5p.DATASET_CREATE)
+dcpl.set_alloc_time(h5py.h5d.ALLOC_TIME_EARLY)
+# Set chunk dimensions (e.g., chunks of size 5)
+chunk_dims = (5,)  # Ensure chunks are compatible with dataspace shape
+dcpl.set_chunk(chunk_dims)
+
+# Create the dataset
+dataset_name = "implicit_index_exact".encode('utf-8')  # Dataset name must be bytes
+dataset = h5py.h5d.create(f.id, dataset_name, datatype, dataspace, dcpl)
+
+# Write data to the dataset
+dataset.write(h5py.h5s.ALL, h5py.h5s.ALL, data)
+dataset.close()
+
+# Second dataset with chunk size mismatch
+data = numpy.arange(50).reshape(10,5)
+
+dataspace = h5py.h5s.create_simple(data.shape)  # Create simple dataspace
+datatype = h5py.h5t.NATIVE_INT32
+
+# Dataset creation property list
+dcpl = h5py.h5p.create(h5py.h5p.DATASET_CREATE)
+dcpl.set_alloc_time(h5py.h5d.ALLOC_TIME_EARLY)
+# Set chunk dimensions
+chunk_dims = (3,2) # mismatched to data shape
+dcpl.set_chunk(chunk_dims)
+
+# Create the dataset
+dataset_name = "implicit_index_mismatch".encode('utf-8')  # Dataset name must be bytes
+dataset = h5py.h5d.create(f.id, dataset_name, datatype, dataspace, dcpl)
+
+# Write data to the dataset
+dataset.write(h5py.h5s.ALL, h5py.h5s.ALL, data)
+dataset.close()
+
+f.close()