extend_ds.cpp

This example shows how to work with extendible datasets.

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * 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 work with extendible dataset.
 *   In the current version of the library dataset MUST be
 *   chunked.
 *
 */
 
#include <iostream>
#include <string>
 
using std::cout;
using std::endl;
 
#include <string>
#include "H5Cpp.h"
using namespace H5;
 
const H5std_string FILE_NAME("SDSextendible.h5");
const H5std_string DATASET_NAME("ExtendibleArray");
const int          NX   = 10;
const int          NY   = 5;
const int          RANK = 2;
 
int
main(void)
{
    /*
     * 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 the data space with unlimited dimensions.
         */
        hsize_t   dims[2]    = {3, 3}; // dataset dimensions at creation
        hsize_t   maxdims[2] = {H5S_UNLIMITED, H5S_UNLIMITED};
        DataSpace mspace1(RANK, dims, maxdims);
 
        /*
         * Create a new file. If file exists its contents will be overwritten.
         */
        H5File file(FILE_NAME, H5F_ACC_TRUNC);
 
        /*
         * Modify dataset creation properties, i.e. enable chunking.
         */
        DSetCreatPropList cparms;
 
        hsize_t chunk_dims[2] = {2, 5};
        cparms.setChunk(RANK, chunk_dims);
 
        /*
         * Set fill value for the dataset
         */
        int fill_val = 0;
        cparms.setFillValue(PredType::NATIVE_INT, &fill_val);
 
        /*
         * Create a new dataset within the file using cparms
         * creation properties.
         */
        DataSet dataset = file.createDataSet(DATASET_NAME, PredType::NATIVE_INT, mspace1, cparms);
 
        /*
         * Extend the dataset. This call assures that dataset is at least 3 x 3.
         */
        hsize_t size[2];
        size[0] = 3;
        size[1] = 3;
        dataset.extend(size);
 
        /*
         * Select a hyperslab.
         */
        DataSpace fspace1 = dataset.getSpace();
        hsize_t   offset[2];
        offset[0]        = 0;
        offset[1]        = 0;
        hsize_t dims1[2] = {3, 3}; /* data1 dimensions */
        fspace1.selectHyperslab(H5S_SELECT_SET, dims1, offset);
 
        /*
         * Write the data to the hyperslab.
         */
        int data1[3][3] = {{1, 1, 1}, /* data to write */
                           {1, 1, 1},
                           {1, 1, 1}};
        dataset.write(data1, PredType::NATIVE_INT, mspace1, fspace1);
 
        /*
         * Extend the dataset. Dataset becomes 10 x 3.
         */
        hsize_t dims2[2] = {7, 1}; /* data2 dimensions */
        dims[0]          = dims1[0] + dims2[0];
        size[0]          = dims[0];
        size[1]          = dims[1];
        dataset.extend(size);
 
        /*
         * Select a hyperslab.
         */
        DataSpace fspace2 = dataset.getSpace();
        offset[0]         = 3;
        offset[1]         = 0;
        fspace2.selectHyperslab(H5S_SELECT_SET, dims2, offset);
 
        /*
         * Define memory space
         */
        DataSpace mspace2(RANK, dims2);
 
        /*
         * Write the data to the hyperslab.
         */
        int data2[7] = {2, 2, 2, 2, 2, 2, 2};
        dataset.write(data2, PredType::NATIVE_INT, mspace2, fspace2);
 
        /*
         * Extend the dataset. Dataset becomes 10 x 5.
         */
        hsize_t dims3[2] = {2, 2}; /* data3 dimensions */
        dims[1]          = dims1[1] + dims3[1];
        size[0]          = dims[0];
        size[1]          = dims[1];
        dataset.extend(size);
 
        /*
         * Select a hyperslab
         */
        DataSpace fspace3 = dataset.getSpace();
        offset[0]         = 0;
        offset[1]         = 3;
        fspace3.selectHyperslab(H5S_SELECT_SET, dims3, offset);
 
        /*
         * Define memory space.
         */
        DataSpace mspace3(RANK, dims3);
 
        /*
         * Write the data to the hyperslab.
         */
        int data3[2][2] = {{3, 3}, {3, 3}};
        dataset.write(data3, PredType::NATIVE_INT, mspace3, fspace3);
 
        /*
         * Read the data from this dataset and display it.
         */
        int i, j;
        int data_out[NX][NY];
        for (i = 0; i < NX; i++) {
            for (j = 0; j < NY; j++)
                data_out[i][j] = 0;
        }
        dataset.read(data_out, PredType::NATIVE_INT);
        /*
         * Resulting dataset
         *
         *         1 1 1 3 3
         *         1 1 1 3 3
         *         1 1 1 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         *         2 0 0 0 0
         */
        /*
         * Display the result.
         */
        for (i = 0; i < NX; i++) {
            for (j = 0; j < NY; j++)
                cout << data_out[i][j] << "  ";
            cout << endl;
        }
    } // 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;
    }
 
    // catch failure caused by the DataSpace operations
    catch (DataTypeIException error) {
        error.printErrorStack();
        return -1;
    }
    return 0;
}