HDF5 C++ API  1.8.20
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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://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 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.
//
#ifdef OLD_HEADER_FILENAME
#include <iostream.h>
#else
#include <iostream>
#endif
#include <string>
#ifndef H5_NO_NAMESPACE
#ifndef H5_NO_STD
using std::cout;
using std::endl;
#endif // H5_NO_STD
#endif
#include "H5Cpp.h"
#ifndef H5_NO_NAMESPACE
using namespace H5;
#endif
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
*/
/*
* 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.printError();
return -1;
}
// catch failure caused by the DataSet operations
catch( DataSetIException error )
{
error.printError();
return -1;
}
// catch failure caused by the DataSpace operations
catch( DataSpaceIException error )
{
error.printError();
return -1;
}
// catch failure caused by the DataSpace operations
catch( DataTypeIException error )
{
error.printError();
return -1;
}
return 0; // successfully terminated
}


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