HDF5 C++ API  1.8.20
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writedata.cpp
This example shows how to write 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 program shows how the select_hyperslab and select_elements
* functions are used to write selected data from memory to the file.
* Program takes 48 elements from the linear buffer and writes them into
* the matrix using 3x2 blocks, (4,3) stride and (2,4) count.
* Then four elements of the matrix are overwritten with the new values and
* file is closed. Program reopens the file and reads and displays the result.
*/
#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( "Select.h5" );
const H5std_string DATASET_NAME( "Matrix in file" );
const int MSPACE1_RANK = 1; // Rank of the first dataset in memory
const int MSPACE1_DIM = 50; // Dataset size in memory
const int MSPACE2_RANK = 1; // Rank of the second dataset in memory
const int MSPACE2_DIM = 4; // Dataset size in memory
const int FSPACE_RANK = 2; // Dataset rank as it is stored in the file
const int FSPACE_DIM1 = 8; // Dimension sizes of the dataset as it is
const int FSPACE_DIM2 = 12; // stored in the file
const int MSPACE_RANK = 2; // Rank of the first dataset in memory
const int MSPACE_DIM1 = 8; // We will read dataset back from the file
const int MSPACE_DIM2 = 9; // to the dataset in memory with these
// dataspace parameters
const int NPOINTS = 4; // Number of points that will be selected
// and overwritten
int main (void)
{
int i,j; // loop indices */
/*
* 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 file.
*/
H5File* file = new H5File( FILE_NAME, H5F_ACC_TRUNC );
/*
* Create property list for a dataset and set up fill values.
*/
int fillvalue = 0; /* Fill value for the dataset */
DSetCreatPropList plist;
plist.setFillValue(PredType::NATIVE_INT, &fillvalue);
/*
* Create dataspace for the dataset in the file.
*/
hsize_t fdim[] = {FSPACE_DIM1, FSPACE_DIM2}; // dim sizes of ds (on disk)
DataSpace fspace( FSPACE_RANK, fdim );
/*
* Create dataset and write it into the file.
*/
DataSet* dataset = new DataSet(file->createDataSet(
DATASET_NAME, PredType::NATIVE_INT, fspace, plist));
/*
* Select hyperslab for the dataset in the file, using 3x2 blocks,
* (4,3) stride and (2,4) count starting at the position (0,1).
*/
hsize_t start[2]; // Start of hyperslab
hsize_t stride[2]; // Stride of hyperslab
hsize_t count[2]; // Block count
hsize_t block[2]; // Block sizes
start[0] = 0; start[1] = 1;
stride[0] = 4; stride[1] = 3;
count[0] = 2; count[1] = 4;
block[0] = 3; block[1] = 2;
fspace.selectHyperslab( H5S_SELECT_SET, count, start, stride, block);
/*
* Create dataspace for the first dataset.
*/
hsize_t dim1[] = {MSPACE1_DIM}; /* Dimension size of the first dataset
(in memory) */
DataSpace mspace1( MSPACE1_RANK, dim1 );
/*
* Select hyperslab.
* We will use 48 elements of the vector buffer starting at the
* second element. Selected elements are 1 2 3 . . . 48
*/
start[0] = 1;
stride[0] = 1;
count[0] = 48;
block[0] = 1;
mspace1.selectHyperslab( H5S_SELECT_SET, count, start, stride, block);
/*
* Write selection from the vector buffer to the dataset in the file.
*
* File dataset should look like this:
* 0 1 2 0 3 4 0 5 6 0 7 8
* 0 9 10 0 11 12 0 13 14 0 15 16
* 0 17 18 0 19 20 0 21 22 0 23 24
* 0 0 0 0 0 0 0 0 0 0 0 0
* 0 25 26 0 27 28 0 29 30 0 31 32
* 0 33 34 0 35 36 0 37 38 0 39 40
* 0 41 42 0 43 44 0 45 46 0 47 48
* 0 0 0 0 0 0 0 0 0 0 0 0
*/
int vector[MSPACE1_DIM]; // vector buffer for dset
/*
* Buffer initialization.
*/
vector[0] = vector[MSPACE1_DIM - 1] = -1;
for (i = 1; i < MSPACE1_DIM - 1; i++)
vector[i] = i;
dataset->write( vector, PredType::NATIVE_INT, mspace1, fspace );
/*
* Reset the selection for the file dataspace fid.
*/
fspace.selectNone();
/*
* Create dataspace for the second dataset.
*/
hsize_t dim2[] = {MSPACE2_DIM}; /* Dimension size of the second dataset
(in memory */
DataSpace mspace2( MSPACE2_RANK, dim2 );
/*
* Select sequence of NPOINTS points in the file dataspace.
*/
hsize_t coord[NPOINTS][FSPACE_RANK]; /* Array to store selected points
from the file dataspace */
coord[0][0] = 0; coord[0][1] = 0;
coord[1][0] = 3; coord[1][1] = 3;
coord[2][0] = 3; coord[2][1] = 5;
coord[3][0] = 5; coord[3][1] = 6;
fspace.selectElements( H5S_SELECT_SET, NPOINTS, (const hsize_t *)coord);
/*
* Write new selection of points to the dataset.
*/
int values[] = {53, 59, 61, 67}; /* New values to be written */
dataset->write( values, PredType::NATIVE_INT, mspace2, fspace );
/*
* File dataset should look like this:
* 53 1 2 0 3 4 0 5 6 0 7 8
* 0 9 10 0 11 12 0 13 14 0 15 16
* 0 17 18 0 19 20 0 21 22 0 23 24
* 0 0 0 59 0 61 0 0 0 0 0 0
* 0 25 26 0 27 28 0 29 30 0 31 32
* 0 33 34 0 35 36 67 37 38 0 39 40
* 0 41 42 0 43 44 0 45 46 0 47 48
* 0 0 0 0 0 0 0 0 0 0 0 0
*
*/
/*
* Close the dataset and the file.
*/
delete dataset;
delete file;
/*
* Open the file.
*/
file = new H5File( FILE_NAME, H5F_ACC_RDONLY );
/*
* Open the dataset.
*/
dataset = new DataSet( file->openDataSet( DATASET_NAME ));
/*
* Get dataspace of the dataset.
*/
fspace = dataset->getSpace();
/*
* Select first hyperslab for the dataset in the file. The following
* elements are selected:
* 10 0 11 12
* 18 0 19 20
* 0 59 0 61
*
*/
start[0] = 1; start[1] = 2;
block[0] = 1; block[1] = 1;
stride[0] = 1; stride[1] = 1;
count[0] = 3; count[1] = 4;
fspace.selectHyperslab(H5S_SELECT_SET, count, start, stride, block);
/*
* Add second selected hyperslab to the selection.
* The following elements are selected:
* 19 20 0 21 22
* 0 61 0 0 0
* 27 28 0 29 30
* 35 36 67 37 38
* 43 44 0 45 46
* 0 0 0 0 0
* Note that two hyperslabs overlap. Common elements are:
* 19 20
* 0 61
*/
start[0] = 2; start[1] = 4;
block[0] = 1; block[1] = 1;
stride[0] = 1; stride[1] = 1;
count[0] = 6; count[1] = 5;
fspace.selectHyperslab(H5S_SELECT_OR, count, start, stride, block);
/*
* Create memory dataspace.
*/
hsize_t mdim[] = {MSPACE_DIM1, MSPACE_DIM2}; /* Dimension sizes of the
dataset in memory when we
read selection from the
dataset on the disk */
DataSpace mspace(MSPACE_RANK, mdim);
/*
* Select two hyperslabs in memory. Hyperslabs has the same
* size and shape as the selected hyperslabs for the file dataspace.
*/
start[0] = 0; start[1] = 0;
block[0] = 1; block[1] = 1;
stride[0] = 1; stride[1] = 1;
count[0] = 3; count[1] = 4;
mspace.selectHyperslab(H5S_SELECT_SET, count, start, stride, block);
start[0] = 1; start[1] = 2;
block[0] = 1; block[1] = 1;
stride[0] = 1; stride[1] = 1;
count[0] = 6; count[1] = 5;
mspace.selectHyperslab(H5S_SELECT_OR, count, start, stride, block);
/*
* Initialize data buffer.
*/
int matrix_out[MSPACE_DIM1][MSPACE_DIM2];
for (i = 0; i < MSPACE_DIM1; i++)
for (j = 0; j < MSPACE_DIM2; j++)
matrix_out[i][j] = 0;
/*
* Read data back to the buffer matrix.
*/
dataset->read(matrix_out, PredType::NATIVE_INT, mspace, fspace);
/*
* Display the result. Memory dataset is:
*
* 10 0 11 12 0 0 0 0 0
* 18 0 19 20 0 21 22 0 0
* 0 59 0 61 0 0 0 0 0
* 0 0 27 28 0 29 30 0 0
* 0 0 35 36 67 37 38 0 0
* 0 0 43 44 0 45 46 0 0
* 0 0 0 0 0 0 0 0 0
* 0 0 0 0 0 0 0 0 0
*/
for (i=0; i < MSPACE_DIM1; i++)
{
for(j=0; j < MSPACE_DIM2; j++)
cout << matrix_out[i][j] << " ";
cout << endl;
}
/*
* Close the dataset and the file.
*/
delete dataset;
delete file;
} // 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;
}
return 0;
}

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