readdata.cpp

This example shows how to read datasets.

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * 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://www.hdfgroup.org/licenses.               *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
//
//      This example reads hyperslab from the SDS.h5 file into
//      two-dimensional plane of a three-dimensional array.  Various
//      information about the dataset in the SDS.h5 file is obtained.
//
 
#include <iostream>
using std::cout;
using std::endl;
 
#include <string>
#include "H5Cpp.h"
using namespace H5;
 
const H5std_string FILE_NAME("SDS.h5");
const H5std_string DATASET_NAME("IntArray");
const int          NX_SUB   = 3; // hyperslab dimensions
const int          NY_SUB   = 4;
const int          NX       = 7; // output buffer dimensions
const int          NY       = 7;
const int          NZ       = 3;
const int          RANK_OUT = 3;
 
int
main(void)
{
    /*
     * Output buffer initialization.
     */
    int i, j, k;
    int data_out[NX][NY][NZ]; /* output buffer */
    for (j = 0; j < NX; j++) {
        for (i = 0; i < NY; i++) {
            for (k = 0; k < NZ; k++)
                data_out[j][i][k] = 0;
        }
    }
 
    /*
     * 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();
 
        /*
         * Open the specified file and the specified dataset in the file.
         */
        H5File  file(FILE_NAME, H5F_ACC_RDONLY);
        DataSet dataset = file.openDataSet(DATASET_NAME);
 
        /*
         * Get the class of the datatype that is used by the dataset.
         */
        H5T_class_t type_class = dataset.getTypeClass();
 
        /*
         * Get class of datatype and print message if it's an integer.
         */
        if (type_class == H5T_INTEGER) {
            cout << "Data set has INTEGER type" << endl;
 
            /*
             * Get the integer datatype
             */
            IntType intype = dataset.getIntType();
 
            /*
             * Get order of datatype and print message if it's a little endian.
             */
            H5std_string order_string;
            H5T_order_t  order = intype.getOrder(order_string);
            cout << order_string << endl;
 
            /*
             * Get size of the data element stored in file and print it.
             */
            size_t size = intype.getSize();
            cout << "Data size is " << size << endl;
        }
 
        /*
         * Get dataspace of the dataset.
         */
        DataSpace dataspace = dataset.getSpace();
 
        /*
         * Get the number of dimensions in the dataspace.
         */
        int rank = dataspace.getSimpleExtentNdims();
 
        /*
         * Get the dimension size of each dimension in the dataspace and
         * display them.
         */
        hsize_t dims_out[2];
        int     ndims = dataspace.getSimpleExtentDims(dims_out, NULL);
        cout << "rank " << rank << ", dimensions " << (unsigned long)(dims_out[0]) << " x "
             << (unsigned long)(dims_out[1]) << endl;
 
        /*
         * Define hyperslab in the dataset; implicitly giving strike and
         * block NULL.
         */
        hsize_t offset[2]; // hyperslab offset in the file
        hsize_t count[2];  // size of the hyperslab in the file
        offset[0] = 1;
        offset[1] = 2;
        count[0]  = NX_SUB;
        count[1]  = NY_SUB;
        dataspace.selectHyperslab(H5S_SELECT_SET, count, offset);
 
        /*
         * Define the memory dataspace.
         */
        hsize_t dimsm[3]; /* memory space dimensions */
        dimsm[0] = NX;
        dimsm[1] = NY;
        dimsm[2] = NZ;
        DataSpace memspace(RANK_OUT, dimsm);
 
        /*
         * Define memory hyperslab.
         */
        hsize_t offset_out[3]; // hyperslab offset in memory
        hsize_t count_out[3];  // size of the hyperslab in memory
        offset_out[0] = 3;
        offset_out[1] = 0;
        offset_out[2] = 0;
        count_out[0]  = NX_SUB;
        count_out[1]  = NY_SUB;
        count_out[2]  = 1;
        memspace.selectHyperslab(H5S_SELECT_SET, count_out, offset_out);
 
        /*
         * Read data from hyperslab in the file into the hyperslab in
         * memory and display the data.
         */
        dataset.read(data_out, PredType::NATIVE_INT, memspace, dataspace);
 
        for (j = 0; j < NX; j++) {
            for (i = 0; i < NY; i++)
                cout << data_out[j][i][0] << " ";
            cout << endl;
        }
        /*
         * 0 0 0 0 0 0 0
         * 0 0 0 0 0 0 0
         * 0 0 0 0 0 0 0
         * 3 4 5 6 0 0 0
         * 4 5 6 7 0 0 0
         * 5 6 7 8 0 0 0
         * 0 0 0 0 0 0 0
         */
    } // 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; // successfully terminated
}