hdf5/examples/h5_cmprss.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * 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://support.hdfgroup.org/ftp/HDF5/releases.  *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 *  This example illustrates how to create a compressed dataset.
 *  It is used in the HDF5 Tutorial.
 */

#include "hdf5.h"

#define FILE "cmprss.h5"
#define RANK 2
#define DIM0 100
#define DIM1 20

int
main()
{

    hid_t file_id, dataset_id, dataspace_id; /* identifiers */
    hid_t plist_id;

    size_t       nelmts;
    unsigned     flags, filter_info;
    H5Z_filter_t filter_type;

    herr_t  status;
    hsize_t dims[2];
    hsize_t cdims[2];

    int i, j, numfilt;
    int buf[DIM0][DIM1];
    int rbuf[DIM0][DIM1];

    /* Uncomment these variables to use SZIP compression
    unsigned szip_options_mask;
    unsigned szip_pixels_per_block;
    */

    /* Create a file.  */
    file_id = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /* Create dataset "Compressed Data" in the group using absolute name.  */
    dims[0]      = DIM0;
    dims[1]      = DIM1;
    dataspace_id = H5Screate_simple(RANK, dims, NULL);

    plist_id = H5Pcreate(H5P_DATASET_CREATE);

    /* Dataset must be chunked for compression */
    cdims[0] = 20;
    cdims[1] = 20;
    status   = H5Pset_chunk(plist_id, 2, cdims);

    /* Set ZLIB / DEFLATE Compression using compression level 6.
     * To use SZIP Compression comment out these lines.
     */
    status = H5Pset_deflate(plist_id, 6);

    /* Uncomment these lines to set SZIP Compression
    szip_options_mask = H5_SZIP_NN_OPTION_MASK;
    szip_pixels_per_block = 16;
    status = H5Pset_szip (plist_id, szip_options_mask, szip_pixels_per_block);
    */

    dataset_id = H5Dcreate2(file_id, "Compressed_Data", H5T_STD_I32BE, dataspace_id, H5P_DEFAULT, plist_id,
                            H5P_DEFAULT);

    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++)
            buf[i][j] = i + j;

    status = H5Dwrite(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf);

    status = H5Sclose(dataspace_id);
    status = H5Dclose(dataset_id);
    status = H5Pclose(plist_id);
    status = H5Fclose(file_id);

    /* Now reopen the file and dataset in the file. */
    file_id    = H5Fopen(FILE, H5F_ACC_RDWR, H5P_DEFAULT);
    dataset_id = H5Dopen2(file_id, "Compressed_Data", H5P_DEFAULT);

    /* Retrieve filter information. */
    plist_id = H5Dget_create_plist(dataset_id);

    numfilt = H5Pget_nfilters(plist_id);
    printf("Number of filters associated with dataset: %i\n", numfilt);

    for (i = 0; i < numfilt; i++) {
        nelmts      = 0;
        filter_type = H5Pget_filter2(plist_id, i, &flags, &nelmts, NULL, 0, NULL, &filter_info);
        printf("Filter Type: ");
        switch (filter_type) {
            case H5Z_FILTER_DEFLATE:
                printf("H5Z_FILTER_DEFLATE\n");
                break;
            case H5Z_FILTER_SZIP:
                printf("H5Z_FILTER_SZIP\n");
                break;
            default:
                printf("Other filter type included.\n");
        }
    }

    status = H5Dread(dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, rbuf);

    status = H5Dclose(dataset_id);
    status = H5Pclose(plist_id);
    status = H5Fclose(file_id);
}