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

  This example shows how to read and write opaque datatypes
  to a dataset.  The program first writes opaque data to a
  dataset with a dataspace of DIM0, 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 1.8

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

#include "hdf5.h"
#include <stdio.h>
#include <stdlib.h>

#define FILE            "opqext.h5"
#define DATASET         "DS1"
#define DIM0            4
#define LEN             7
#define RANK            1

int
main (void)
{
    hid_t       file, space, dtype, dset, prop, memspace, filespace;   
    herr_t      status;
    hsize_t     dims[1] = {DIM0};
    hsize_t     maxdims[1] = {H5S_UNLIMITED};
    hsize_t     chunk_dims[1]= {2};
    size_t      len;
    char        wdata[DIM0*LEN],            /* Write buffer */
                str[LEN] = "OPAQUE",
                *tag;
    char        edata[DIM0*10];
    int         ndims,
                i, j;
    hsize_t     dimsext[1]={10};
    hsize_t     size[1];
    hsize_t     offset[1];

    /*
     * Initialize data.
     */
    for (i=0; i<DIM0; i++) {
        for (j=0; j<LEN-1; j++)
            wdata[j + i * LEN] = str[j];
        wdata[LEN - 1 + i * LEN] = (char) i + '0';
    }

    /*
     * Create a new file using the default properties.
     */
    file = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create opaque datatype and set the tag to something appropriate.
     * For this example we will write and view the data as a character
     * array.
     */
    dtype = H5Tcreate (H5T_OPAQUE, LEN);
    status = H5Tset_tag (dtype, "Character array");

    prop = H5Pcreate (H5P_DATASET_CREATE);
    status = H5Pset_chunk (prop, RANK, chunk_dims);

    space = H5Screate_simple (1, dims, maxdims);

    /*
     * Create the dataset and write the opaque data to it.
     */
    dset = H5Dcreate (file, DATASET, dtype, space,  H5P_DEFAULT, prop,
                H5P_DEFAULT);
    status = H5Dwrite (dset, dtype, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata);

    size[0] = dims[0]+ dimsext[0];
    status = H5Dset_extent (dset, size);

    for (i=0; i< dimsext[0]; i++) 
        for (j=0; j<LEN; j++)
            edata[j + i * LEN] = 'a';


    filespace = H5Dget_space (dset);
    memspace = H5Screate_simple (RANK, dimsext, NULL);

    offset[0] = 4;
    status = H5Sselect_hyperslab (filespace, H5S_SELECT_SET, offset, NULL, dimsext, NULL);
    status = H5Dwrite (dset, dtype, memspace, filespace, H5P_DEFAULT, edata);

    status = H5Sclose (memspace);
    status = H5Sclose (filespace);

    status = H5Pclose (prop);
    status = H5Dclose (dset);
    status = H5Sclose (space);
    status = H5Tclose (dtype);
    status = H5Fclose (file);

    return 0;
}