hdf5/HDF5Examples/C/H5T/h5ex_t_objref.c

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

  This example shows how to read and write object references
  to a dataset.  The program first creates objects in the
  file and writes references to those objects to a dataset
  with a dataspace of DIM0, then closes the file.  Next, it
  reopens the file, dereferences the references, and outputs
  the names of their targets to the screen.

Note: This example includes older cases from previous versions
  of HDF5 for historical reference and to illustrate how to
  migrate older code to newer functions. However, readers are
  encouraged to avoid using deprecated functions and earlier
  schemas from those versions.

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

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

#define FILENAME "h5ex_t_objref.h5"
#define DATASET  "DS1"
#define DIM0     2
#define RANK     1

int
main(void)
{
    hid_t   file  = H5I_INVALID_HID; /* File Handle */
    hid_t   space = H5I_INVALID_HID; /* Dataspace Handle */
    hid_t   dset  = H5I_INVALID_HID; /* Dataset Handle */
    hid_t   obj   = H5I_INVALID_HID; /* Object Handle */
    herr_t  status;
    hsize_t dims[1] = {DIM0};
    ssize_t size;
    char   *name = NULL;
    int     ndims;
    hsize_t i;

#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
    hid_t      ref_type = H5T_STD_REF; /* Reference datatype */
    H5R_ref_t  wdata[DIM0];            /* buffer to write to disk */
    H5R_ref_t *rdata = NULL;           /* buffer to read into*/
    H5O_type_t objtype;                /* Reference type */
#else
    hid_t       ref_type = H5T_STD_REF_OBJ; /* Reference datatype */
    hobj_ref_t  wdata[DIM0];                /* Write buffer */
    hobj_ref_t *rdata = NULL;               /* Read buffer */
    H5O_type_t  objtype;
#endif

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

    /*
     * Create a dataset with a null dataspace.
     */
    space  = H5Screate(H5S_NULL);
    obj    = H5Dcreate(file, "DS2", H5T_STD_I32LE, space, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    status = H5Dclose(obj);
    status = H5Sclose(space);

    /*
     * Create a group.
     */
    obj    = H5Gcreate(file, "G1", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    status = H5Gclose(obj);

    /*
     * Create dataspace.  Setting maximum size to NULL sets the maximum
     * size to be the current size.
     */
    space = H5Screate_simple(RANK, dims, NULL);

    /*
     * Create references to the previously created objects.
     */
#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
    status = H5Rcreate_object(file, "G1", H5R_OBJECT, &wdata[0]);
    status = H5Rcreate_object(file, "DS2", H5R_OBJECT, &wdata[1]);
#else
    /*
     * Passing -1
     * as space_id causes this parameter to be ignored.  Other values
     * besides valid dataspaces result in an error.
     */
    status = H5Rcreate(&wdata[0], file, "G1", H5R_OBJECT, -1);
    status = H5Rcreate(&wdata[1], file, "DS2", H5R_OBJECT, -1);
#endif

    /*
     * Create the dataset and write the object references to it.
     */
    dset   = H5Dcreate(file, DATASET, ref_type, space, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    status = H5Dwrite(dset, ref_type, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata);

    /*
     * Close and release resources.
     */
#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
    status = H5Rdestroy(&wdata[0]);
    status = H5Rdestroy(&wdata[1]);
#endif
    status = H5Dclose(dset);
    status = H5Sclose(space);
    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(FILENAME, H5F_ACC_RDONLY, H5P_DEFAULT);
    dset = H5Dopen(file, DATASET, H5P_DEFAULT);

    /*
     * Get dataspace and allocate memory for read buffer.
     */
    space = H5Dget_space(dset);
    ndims = H5Sget_simple_extent_dims(space, dims, NULL);

#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
    rdata = (H5R_ref_t *)malloc(dims[0] * sizeof(H5R_ref_t));
#else
    rdata = (hobj_ref_t *)malloc(dims[0] * sizeof(hobj_ref_t));
#endif
    /*
     * Read the data.
     */
    status = H5Dread(dset, ref_type, H5S_ALL, H5S_ALL, H5P_DEFAULT, rdata);

    /*
     * Output the data to the screen.
     */
    for (i = 0; i < dims[0]; i++) {
        printf("%s[%" PRIuHSIZE "]:\n  ->", DATASET, i);

        /*
         * Open the referenced object, get its name and type.
         */
#if H5_VERSION_GE(1, 10, 0) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
        obj    = H5Ropen_object(&rdata[i], H5P_DEFAULT, H5P_DEFAULT);
        status = H5Rget_obj_type3(&rdata[i], H5P_DEFAULT, &objtype);
#else
        obj    = H5Rdereference(dset, H5P_DEFAULT, H5R_OBJECT, &rdata[i]);
        status = H5Rget_obj_type(dset, H5R_OBJECT, &rdata[i], &objtype);
#endif
#else
        obj    = H5Rdereference(dset, H5R_OBJECT, &rdata[i]);
        status = H5Rget_obj_type(dset, H5R_OBJECT, &rdata[i], &objtype);
#endif

        /*
         * Get the length of the name, allocate space, then retrieve
         * the name.
         */
        size = 1 + H5Iget_name(obj, NULL, 0);
        name = (char *)malloc(size);
        size = H5Iget_name(obj, name, size);

        /*
         * Print the object type and close the object.
         */
        switch (objtype) {
            case H5O_TYPE_GROUP:
                printf("Group");
                break;
            case H5O_TYPE_DATASET:
                printf("Dataset");
                break;
            case H5O_TYPE_NAMED_DATATYPE:
                printf("Named Datatype");
                break;
            case H5O_TYPE_MAP:
                printf("Map Object");
                break;
            case H5O_TYPE_UNKNOWN:
            case H5O_TYPE_NTYPES:
                printf("Unknown");
        }
        status = H5Oclose(obj);

        /*
         * Print the name and deallocate space for the name.
         */
        printf(": %s\n", name);
        free(name);

#if H5_VERSION_GE(1, 12, 0) && !defined(H5_USE_110_API) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
        status = H5Rdestroy(&rdata[i]);
#endif
    }

    /*
     * Close and release resources.
     */
    free(rdata);
    status = H5Dclose(dset);
    status = H5Sclose(space);
    status = H5Fclose(file);

    return 0;
}