/************************************************************

  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.

  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_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,
                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 dataset with a scalar dataspace.
     */
    space = H5Screate (H5S_SCALAR);
    dset = H5Dcreate (file, DATASET, H5T_STD_I32LE, space, 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);
    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);
    attr = H5Aopen_name (dset, ATTRIBUTE);

    /*
     * 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[%u]:\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;
}