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+/************************************************************
+
+ This example illustrates the concept of the virtual dataset.
+ The program creates three 1-dim source datasets and writes
+ data to them. Then it creates 2-dim virtual dataset and
+ maps the first three rows of the virtual dataset to the data
+ in the source datasets. Elements of a row are mapped to all
+ elements of the corresponding source dataset.
+ The fourth row is not mapped and will be filled with the fill
+ values when virtual dataset is read back.
+
+ The program closes all datasets, and then reopens the virtual
+ dataset, and finds and prints its creation properties.
+ Then it reads the values.
+
+ This file is intended for use with HDF5 Library version 1.10
+
+ ************************************************************/
+
+#include "hdf5.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#define FILE "vds.h5"
+#define DATASET "VDS"
+#define VDSDIM1 6
+#define VDSDIM0 4
+#define DIM0 6
+#define RANK1 1
+#define RANK2 2
+
+const char *SRC_FILE[] = {
+ "a.h5",
+ "b.h5",
+ "c.h5"
+};
+
+const char *SRC_DATASET[] = {
+ "A",
+ "B",
+ "C"
+};
+
+int
+main (void)
+{
+ hid_t file, space, src_space, vspace, dset; /* Handles */
+ hid_t dcpl;
+ herr_t status;
+ hsize_t vdsdims[2] = {VDSDIM0, VDSDIM1}, /* Datasets dimension */
+ dims[1] = {DIM0},
+ start[2], /* Hyperslab parameters */
+ stride[2],
+ count[2],
+ block[2];
+ int wdata[DIM0], /* Write buffer for source dataset */
+ rdata[VDSDIM0][VDSDIM1], /* Read buffer for virtual dataset */
+ i, j, k, l;
+ int fill_value = -1; /* Fill value for VDS */
+ H5D_layout_t layout; /* Storage layout */
+ size_t num_map; /* Number of mappings */
+ ssize_t len; /* Length of the string; also a return value */
+ char *filename;
+ char *dsetname;
+ hsize_t nblocks;
+ hsize_t *buf; /* Buffer to hold hyperslab coordinates */
+
+ /*
+ * Create source files and datasets. This step is optional.
+ */
+ for (i=0; i < 3; i++) {
+ /*
+ * Initialize data for i-th source dataset.
+ */
+ for (j = 0; j < DIM0; j++) wdata[j] = i+1;
+
+ /*
+ * Create the source files and datasets. Write data to each dataset and
+ * close all resources.
+ */
+
+ file = H5Fcreate (SRC_FILE[i], H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+ space = H5Screate_simple (RANK1, dims, NULL);
+ dset = H5Dcreate (file, SRC_DATASET[i], H5T_NATIVE_INT, space, H5P_DEFAULT,
+ H5P_DEFAULT, H5P_DEFAULT);
+ status = H5Dwrite (dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT,
+ wdata);
+ status = H5Sclose (space);
+ status = H5Dclose (dset);
+ status = H5Fclose (file);
+ }
+
+ file = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+
+ /* Create VDS dataspace. */
+ space = H5Screate_simple (RANK2, vdsdims, NULL);
+ src_space = H5Screate_simple (RANK1, dims, NULL);
+
+ /* Create VDS creation property */
+ dcpl = H5Pcreate (H5P_DATASET_CREATE);
+ status = H5Pset_fill_value (dcpl, H5T_NATIVE_INT, &fill_value);
+
+ /* Initialize hyperslab values */
+ start[0] = 0;
+ start[1] = 0;
+ count[0] = 1;
+ count[1] = 1;
+ block[0] = 1;
+ block[1] = VDSDIM1;
+
+ /*
+ * Build the mappings.
+ *
+ * Select the first, the second and the third rows and map each row to the data in the
+ * corresponding source datasets.
+ */
+ for (i = 0; i < 3; i++) {
+ start[0] = (hsize_t)i;
+ /* Select i-th row in the virtual dataset; selection in the source datasets is the same. */
+ status = H5Sselect_hyperslab (space, H5S_SELECT_SET, start, NULL, count, block);
+ status = H5Pset_virtual (dcpl, space, SRC_FILE[i], SRC_DATASET[i], src_space);
+ status = H5Sselect_none (space);
+ }
+
+ /* Create a virtual dataset */
+ dset = H5Dcreate (file, DATASET, H5T_NATIVE_INT, space, H5P_DEFAULT,
+ dcpl, H5P_DEFAULT);
+ status = H5Sclose (space);
+ status = H5Sclose (src_space);
+ status = H5Dclose (dset);
+ status = H5Fclose (file);
+
+ /*
+ * Now we begin the read section of this example.
+ */
+
+ /*
+ * Open file and virtual dataset using the default properties.
+ */
+ file = H5Fopen (FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
+ dset = H5Dopen (file, DATASET, H5P_DEFAULT);
+
+ /*
+ * Get creation property list and mapping properties.
+ */
+ dcpl = H5Dget_create_plist (dset);
+
+ /*
+ * Get storage layout.
+ */
+ layout = H5Pget_layout (dcpl);
+ if (H5D_VIRTUAL == layout)
+ printf(" Dataset has a virtual layout \n");
+ else
+ printf("Wrong layout found \n");
+
+ /*
+ * Find number of mappings.
+ */
+ status = H5Pget_virtual_count (dcpl, &num_map);
+ printf("Number of mappings is %d\n", num_map);
+
+ /*
+ * Get mapping parameters for each mapping.
+ */
+ for (i = 0; i < (int)num_map; i++) {
+ printf("Mapping %d \n", i);
+ printf(" Selection in the virtual dataset ");
+ /* Get selection in the virttual dataset */
+ vspace = H5Pget_virtual_vspace (dcpl, (size_t)i);
+
+ /* Make sure that this is a hyperslab selection and then print information. */
+ if (H5Sget_select_type(vspace) == H5S_SEL_HYPERSLABS) {
+ nblocks = H5Sget_select_hyper_nblocks (vspace);
+ buf = (hsize_t *)malloc(sizeof(hsize_t)*2*RANK2*nblocks);
+ status = H5Sget_select_hyper_blocklist (vspace, (hsize_t)0, nblocks, buf);
+ for (l=0; l<nblocks; l++) {
+ printf("(");
+ for (k=0; k<RANK2-1; k++) printf("%d,", (int)buf[k]);
+ printf("%d", (int)buf[k]);
+ printf(") - ");
+ printf("(");
+ for (k=0; k<RANK2-1; k++) printf("%d,", (int)buf[RANK2+k]);
+ printf("%d", (int)buf[RANK2+k]);
+ printf(")");
+ printf ("\n");
+ }
+ }
+ /* Get source file name */
+ len = H5Pget_virtual_filename (dcpl, (size_t)i, NULL, 0);
+ filename = (char *)malloc((size_t)len*sizeof(char)+1);
+ H5Pget_virtual_filename (dcpl, (size_t)i, filename, len+1);
+ printf(" Source filename %s\n", filename);
+
+ /* Get source dataset name */
+ len = H5Pget_virtual_dsetname (dcpl, (size_t)i, NULL, 0);
+ dsetname = (char *)malloc((size_t)len*sizeof(char)+1);
+ H5Pget_virtual_dsetname (dcpl, (size_t)i, dsetname, len+1);
+ printf(" Source dataset name %s\n", dsetname);
+
+ /* Get selection in the source dataset */
+ printf(" Selection in the source dataset ");
+ src_space = H5Pget_virtual_srcspace (dcpl, (size_t)i);
+
+ /* Make sure it is ALL selection and then print the coordinates */
+ if(H5Sget_select_type(src_space) == H5S_SEL_ALL) {
+ printf("(0) - (%d)", DIM0-1);
+ printf ("\n");
+ }
+ H5Sclose(vspace);
+ H5Sclose(src_space);
+ free(filename);
+ free(dsetname);
+ free(buf);
+ }
+
+#ifdef LATER
+ /*
+ * Read the data using the default properties.
+ */
+ status = H5Dread (dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT,
+ rdata[0]);
+
+ /*
+ * Output the data to the screen.
+ */
+ printf (" VDS Data:\n");
+ for (i=0; i<VDSDIM0; i++) {
+ printf (" [");
+ for (j=0; j<VDSDIM1; j++)
+ printf (" %3d", rdata[i][j]);
+ printf ("]\n");
+ }
+#endif
+ /*
+ * Close and release resources.
+ */
+ status = H5Pclose (dcpl);
+ status = H5Dclose (dset);
+ status = H5Fclose (file);
+
+ return 0;
+}
+