hdf5/c++/examples/h5tutr_cmprss.cpp

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

#include <iostream>
using std::cout;
using std::endl;

#include <string>
#include "H5Cpp.h"
using namespace H5;

const H5std_string FILE_NAME("h5tutr_cmprss.h5");
const H5std_string DATASET_NAME("Compressed_Data");
const int          DIM0 = 100;
const int          DIM1 = 20;

int
main(void)
{
    hsize_t dims[2]       = {DIM0, DIM1}; // dataset dimensions
    hsize_t chunk_dims[2] = {20, 20};     // chunk dimensions
    int     i, j, buf[DIM0][DIM1];

    // Try block to detect exceptions raised by any of the calls inside it
    try {
        // Turn off the auto-printing when failure occurs so that we can
        // handle the errors appropriately
        Exception::dontPrint();

        // Create a new file using the default property lists.
        H5File file(FILE_NAME, H5F_ACC_TRUNC);

        // Create the data space for the dataset.
        DataSpace *dataspace = new DataSpace(2, dims);

        // Modify dataset creation property to enable chunking
        DSetCreatPropList *plist = new DSetCreatPropList;
        plist->setChunk(2, chunk_dims);

        // Set ZLIB (DEFLATE) Compression using level 6.
        // To use SZIP compression comment out this line.
        plist->setDeflate(6);

        // Uncomment these lines to set SZIP Compression
        // unsigned szip_options_mask = H5_SZIP_NN_OPTION_MASK;
        // unsigned szip_pixels_per_block = 16;
        // plist->setSzip(szip_options_mask, szip_pixels_per_block);

        // Create the dataset.
        DataSet *dataset =
            new DataSet(file.createDataSet(DATASET_NAME, PredType::STD_I32BE, *dataspace, *plist));

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

        // Write data to dataset.
        dataset->write(buf, PredType::NATIVE_INT);

        // Close objects and file.  Either approach will close the HDF5 item.
        delete dataspace;
        delete dataset;
        delete plist;
        file.close();

        // -----------------------------------------------
        // Re-open the file and dataset, retrieve filter
        // information for dataset and read the data back.
        // -----------------------------------------------

        int          rbuf[DIM0][DIM1];
        int          numfilt;
        size_t       nelmts = {1}, namelen = {1};
        unsigned     flags, filter_info, cd_values[1], idx;
        char         name[1];
        H5Z_filter_t filter_type;

        // Open the file and the dataset in the file.
        file.openFile(FILE_NAME, H5F_ACC_RDONLY);
        dataset = new DataSet(file.openDataSet(DATASET_NAME));

        // Get the create property list of the dataset.
        plist = new DSetCreatPropList(dataset->getCreatePlist());

        // Get the number of filters associated with the dataset.
        numfilt = plist->getNfilters();
        cout << "Number of filters associated with dataset: " << numfilt << endl;

        for (idx = 0; idx < numfilt; idx++) {
            nelmts = 0;

            filter_type = plist->getFilter(idx, flags, nelmts, cd_values, namelen, name, filter_info);

            cout << "Filter Type: ";

            switch (filter_type) {
                case H5Z_FILTER_DEFLATE:
                    cout << "H5Z_FILTER_DEFLATE" << endl;
                    break;
                case H5Z_FILTER_SZIP:
                    cout << "H5Z_FILTER_SZIP" << endl;
                    break;
                default:
                    cout << "Other filter type included." << endl;
            }
        }

        // Read data.
        dataset->read(rbuf, PredType::NATIVE_INT);

        delete plist;
        delete dataset;
        file.close(); // can be skipped

    } // end of try block

    // catch failure caused by the H5File operations
    catch (FileIException error) {
        error.printErrorStack();
        return -1;
    }

    // catch failure caused by the DataSet operations
    catch (DataSetIException error) {
        error.printErrorStack();
        return -1;
    }

    // catch failure caused by the DataSpace operations
    catch (DataSpaceIException error) {
        error.printErrorStack();
        return -1;
    }

    return 0; // successfully terminated
}