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+/************************************************************
+
+ This example shows how to read and write variable-length
+ datatypes to a dataset. The program first writes two
+ variable-length integer arrays to a dataset then closes
+ the file. Next, it reopens the file, reads back the data,
+ and outputs it to the screen.
+
+ This file is intended for use with HDF5 Library version 1.6
+
+ ************************************************************/
+
+#include "hdf5.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+#define FILE "h5ex_t_vlen.h5"
+#define DATASET "DS1"
+#define LEN0 3
+#define LEN1 12
+
+int
+main(void)
+{
+ hid_t file, filetype, memtype, space, dset;
+ /* Handles */
+ herr_t status;
+ hvl_t wdata[2], /* Array of vlen structures */
+ *rdata; /* Pointer to vlen structures */
+ hsize_t dims[1] = {2};
+ int *ptr, ndims, i, j;
+
+ /*
+ * Initialize variable-length data. wdata[0] is a countdown of
+ * length LEN0, wdata[1] is a Fibonacci sequence of length LEN1.
+ */
+ wdata[0].len = LEN0;
+ ptr = (int *)malloc(wdata[0].len * sizeof(int));
+ for (i = 0; i < wdata[0].len; i++)
+ ptr[i] = wdata[0].len - i; /* 3 2 1 */
+ wdata[0].p = (void *)ptr;
+
+ wdata[1].len = LEN1;
+ ptr = (int *)malloc(wdata[1].len * sizeof(int));
+ ptr[0] = 1;
+ ptr[1] = 1;
+ for (i = 2; i < wdata[1].len; i++)
+ ptr[i] = ptr[i - 1] + ptr[i - 2]; /* 1 1 2 3 5 8 etc. */
+ wdata[1].p = (void *)ptr;
+
+ /*
+ * Create a new file using the default properties.
+ */
+ file = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+
+ /*
+ * Create variable-length datatype for file and memory.
+ */
+ filetype = H5Tvlen_create(H5T_STD_I32LE);
+ memtype = H5Tvlen_create(H5T_NATIVE_INT);
+
+ /*
+ * Create dataspace. Setting maximum size to NULL sets the maximum
+ * size to be the current size.
+ */
+ space = H5Screate_simple(1, dims, NULL);
+
+ /*
+ * Create the dataset and write the variable-length data to it.
+ */
+ dset = H5Dcreate(file, DATASET, filetype, space, H5P_DEFAULT);
+ status = H5Dwrite(dset, memtype, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata);
+
+ /*
+ * Close and release resources. Note the use of H5Dvlen_reclaim
+ * removes the need to manually free() the previously malloc'ed
+ * data.
+ */
+ status = H5Dvlen_reclaim(memtype, space, H5P_DEFAULT, wdata);
+ status = H5Dclose(dset);
+ status = H5Sclose(space);
+ status = H5Tclose(filetype);
+ status = H5Tclose(memtype);
+ status = H5Fclose(file);
+
+ /*
+ * Now we begin the read section of this example. Here we assume
+ * the dataset has the same name and rank, but can have any size.
+ * Therefore we must allocate a new array to read in data using
+ * malloc().
+ */
+
+ /*
+ * Open file and dataset.
+ */
+ file = H5Fopen(FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
+ dset = H5Dopen(file, DATASET);
+
+ /*
+ * Get dataspace and allocate memory for array of vlen structures.
+ * This does not actually allocate memory for the vlen data, that
+ * will be done by the library.
+ */
+ space = H5Dget_space(dset);
+ ndims = H5Sget_simple_extent_dims(space, dims, NULL);
+ rdata = (hvl_t *)malloc(dims[0] * sizeof(hvl_t));
+
+ /*
+ * Create the memory datatype.
+ */
+ memtype = H5Tvlen_create(H5T_NATIVE_INT);
+
+ /*
+ * Read the data.
+ */
+ status = H5Dread(dset, memtype, H5S_ALL, H5S_ALL, H5P_DEFAULT, rdata);
+
+ /*
+ * Output the variable-length data to the screen.
+ */
+ for (i = 0; i < dims[0]; i++) {
+ printf("%s[%u]:\n {", DATASET, i);
+ ptr = rdata[i].p;
+ for (j = 0; j < rdata[i].len; j++) {
+ printf(" %d", ptr[j]);
+ if ((j + 1) < rdata[i].len)
+ printf(",");
+ }
+ printf(" }\n");
+ }
+
+ /*
+ * Close and release resources. Note we must still free the
+ * top-level pointer "rdata", as H5Dvlen_reclaim only frees the
+ * actual variable-length data, and not the structures themselves.
+ */
+ status = H5Dvlen_reclaim(memtype, space, H5P_DEFAULT, rdata);
+ free(rdata);
+ status = H5Dclose(dset);
+ status = H5Sclose(space);
+ status = H5Tclose(memtype);
+ status = H5Fclose(file);
+
+ return 0;
+}