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/************************************************************
This example shows how to read and write variable-length
datatypes to an attribute. The program first writes two
variable-length integer arrays to the attribute then
closes the file. Next, it reopens the file, reads back
the data, and outputs it to the screen.
************************************************************/
#include "hdf5.h"
#include <stdio.h>
#include <stdlib.h>
#define FILE "h5ex_t_vlenatt.h5"
#define DATASET "DS1"
#define ATTRIBUTE "A1"
#define LEN0 3
#define LEN1 12
int
main(void)
{
hid_t file, filetype, memtype, space, dset, attr;
/* 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;
hsize_t 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 - (size_t)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 dataset with a null dataspace.
*/
space = H5Screate(H5S_NULL);
dset = H5Dcreate(file, DATASET, H5T_STD_I32LE, space, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
status = H5Sclose(space);
/*
* Create dataspace. Setting maximum size to NULL sets the maximum
* size to be the current size.
*/
space = H5Screate_simple(1, dims, NULL);
/*
* Create the attribute and write the variable-length data to it
*/
attr = H5Acreate(dset, ATTRIBUTE, filetype, space, H5P_DEFAULT, H5P_DEFAULT);
status = H5Awrite(attr, memtype, 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 = H5Aclose(attr);
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 attribute 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, dataset, and attribute.
*/
file = H5Fopen(FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
dset = H5Dopen(file, DATASET, H5P_DEFAULT);
attr = H5Aopen(dset, ATTRIBUTE, H5P_DEFAULT);
/*
* 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 = H5Aget_space(attr);
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 = H5Aread(attr, memtype, rdata);
/*
* Output the variable-length data to the screen.
*/
for (i = 0; i < dims[0]; i++) {
printf("%s[%llu]:\n {", ATTRIBUTE, 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 = H5Aclose(attr);
status = H5Dclose(dset);
status = H5Sclose(space);
status = H5Tclose(memtype);
status = H5Fclose(file);
return 0;
}
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