hdf5/examples/h5_compound.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * This example shows how to create a compound data type,
 * write an array which has the compound data type to the file,
 * and read back fields' subsets.
 */

#include "hdf5.h"

#define H5FILE_NAME "SDScompound.h5"
#define DATASETNAME "ArrayOfStructures"
#define LENGTH      10
#define RANK        1

int
main(void)
{

    /* First structure  and dataset*/
    typedef struct s1_t {
        int    a;
        float  b;
        double c;
    } s1_t;
    s1_t  s1[LENGTH];
    hid_t s1_tid; /* File datatype identifier */

    /* Second structure (subset of s1_t)  and dataset*/
    typedef struct s2_t {
        double c;
        int    a;
    } s2_t;
    s2_t  s2[LENGTH];
    hid_t s2_tid; /* Memory datatype handle */

    /* Third "structure" ( will be used to read float field of s1) */
    hid_t s3_tid; /* Memory datatype handle */
    float s3[LENGTH];

    int     i;
    hid_t   file, dataset, space; /* Handles */
    herr_t  status;
    hsize_t dim[] = {LENGTH}; /* Dataspace dimensions */

    /*
     * Initialize the data
     */
    for (i = 0; i < LENGTH; i++) {
        s1[i].a = i;
        s1[i].b = i * i;
        s1[i].c = 1. / (i + 1);
    }

    /*
     * Create the data space.
     */
    space = H5Screate_simple(RANK, dim, NULL);

    /*
     * Create the file.
     */
    file = H5Fcreate(H5FILE_NAME, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create the memory data type.
     */
    s1_tid = H5Tcreate(H5T_COMPOUND, sizeof(s1_t));
    H5Tinsert(s1_tid, "a_name", HOFFSET(s1_t, a), H5T_NATIVE_INT);
    H5Tinsert(s1_tid, "c_name", HOFFSET(s1_t, c), H5T_NATIVE_DOUBLE);
    H5Tinsert(s1_tid, "b_name", HOFFSET(s1_t, b), H5T_NATIVE_FLOAT);

    /*
     * Create the dataset.
     */
    dataset = H5Dcreate2(file, DATASETNAME, s1_tid, space, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Wtite data to the dataset;
     */
    status = H5Dwrite(dataset, s1_tid, H5S_ALL, H5S_ALL, H5P_DEFAULT, s1);

    /*
     * Release resources
     */
    H5Tclose(s1_tid);
    H5Sclose(space);
    H5Dclose(dataset);
    H5Fclose(file);

    /*
     * Open the file and the dataset.
     */
    file = H5Fopen(H5FILE_NAME, H5F_ACC_RDONLY, H5P_DEFAULT);

    dataset = H5Dopen2(file, DATASETNAME, H5P_DEFAULT);

    /*
     * Create a data type for s2
     */
    s2_tid = H5Tcreate(H5T_COMPOUND, sizeof(s2_t));

    H5Tinsert(s2_tid, "c_name", HOFFSET(s2_t, c), H5T_NATIVE_DOUBLE);
    H5Tinsert(s2_tid, "a_name", HOFFSET(s2_t, a), H5T_NATIVE_INT);

    /*
     * Read two fields c and a from s1 dataset. Fields in the file
     * are found by their names "c_name" and "a_name".
     */
    status = H5Dread(dataset, s2_tid, H5S_ALL, H5S_ALL, H5P_DEFAULT, s2);

    /*
     * Display the fields
     */
    printf("\n");
    printf("Field c : \n");
    for (i = 0; i < LENGTH; i++)
        printf("%.4f ", s2[i].c);
    printf("\n");

    printf("\n");
    printf("Field a : \n");
    for (i = 0; i < LENGTH; i++)
        printf("%d ", s2[i].a);
    printf("\n");

    /*
     * Create a data type for s3.
     */
    s3_tid = H5Tcreate(H5T_COMPOUND, sizeof(float));

    status = H5Tinsert(s3_tid, "b_name", 0, H5T_NATIVE_FLOAT);

    /*
     * Read field b from s1 dataset. Field in the file is found by its name.
     */
    status = H5Dread(dataset, s3_tid, H5S_ALL, H5S_ALL, H5P_DEFAULT, s3);

    /*
     * Display the field
     */
    printf("\n");
    printf("Field b : \n");
    for (i = 0; i < LENGTH; i++)
        printf("%.4f ", s3[i]);
    printf("\n");

    /*
     * Release resources
     */
    H5Tclose(s2_tid);
    H5Tclose(s3_tid);
    H5Dclose(dataset);
    H5Fclose(file);

    return 0;
}