hdf5/examples/h5_subset.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * 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 files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
 * access to either file, you may request a copy from help@hdfgroup.org.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/* 
 *  This example illustrates how to read/write a subset of data (a slab) 
 *  from/to a dataset in an HDF5 file.  It is used in the HDF5 Tutorial.
 */
 
#include "hdf5.h"

#define FILE        "subset.h5"
#define DATASETNAME "IntArray" 
#define RANK  2

#define DIM0_SUB  3                         /* subset dimensions */ 
#define DIM1_SUB  4 


#define DIM0     8                          /* size of dataset */       
#define DIM1     10 

int
main (void)
{
    hsize_t     dims[2], dimsm[2];   
    int         data[DIM0][DIM1];           /* data to write */
    int         sdata[DIM0_SUB][DIM1_SUB];  /* subset to write */
    int         rdata[DIM0][DIM1];          /* buffer for read */
 
    hid_t       file_id, dataset_id;        /* handles */
    hid_t       dataspace_id, memspace_id; 

    herr_t      status;                             
   
    hsize_t     count[2];              /* size of subset in the file */
    hsize_t     offset[2];             /* subset offset in the file */
    hsize_t     stride[2];
    hsize_t     block[2];
    int         i, j;

    
    /*****************************************************************
     * Create a new file with default creation and access properties.*
     * Then create a dataset and write data to it and close the file *
     * and dataset.                                                  *
     *****************************************************************/

    file_id = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    dims[0] = DIM0;
    dims[1] = DIM1;
    dataspace_id = H5Screate_simple (RANK, dims, NULL); 

    dataset_id = H5Dcreate2 (file_id, DATASETNAME, H5T_STD_I32BE, dataspace_id,
                            H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);


    for (j = 0; j < DIM0; j++) {
	for (i = 0; i < DIM1; i++)
            if (i< (DIM1/2))
	       data[j][i] = 1;
            else
               data[j][i] = 2;
    }     

    status = H5Dwrite (dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL,
                      H5P_DEFAULT, data);

    printf ("\nData Written to File:\n");
    for (i = 0; i<DIM0; i++){
       for (j = 0; j<DIM1; j++)
           printf (" %i", data[i][j]);
       printf ("\n");
    }
    status = H5Sclose (dataspace_id);
    status = H5Dclose (dataset_id);
    status = H5Fclose (file_id);


    /*****************************************************
     * Reopen the file and dataset and write a subset of *
     * values to the dataset. 
     *****************************************************/

    file_id = H5Fopen (FILE, H5F_ACC_RDWR, H5P_DEFAULT);
    dataset_id = H5Dopen2 (file_id, DATASETNAME, H5P_DEFAULT);

    /* Specify size and shape of subset to write. */

    offset[0] = 1;
    offset[1] = 2;

    count[0]  = DIM0_SUB;  
    count[1]  = DIM1_SUB;

    stride[0] = 1;
    stride[1] = 1;

    block[0] = 1;
    block[1] = 1;

    /* Create memory space with size of subset. Get file dataspace 
       and select subset from file dataspace. */

    dimsm[0] = DIM0_SUB;
    dimsm[1] = DIM1_SUB;
    memspace_id = H5Screate_simple (RANK, dimsm, NULL); 

    dataspace_id = H5Dget_space (dataset_id);
    status = H5Sselect_hyperslab (dataspace_id, H5S_SELECT_SET, offset,
                                  stride, count, block);

    /* Write a subset of data to the dataset, then read the 
       entire dataset back from the file.  */

    printf ("\nWrite subset to file specifying:\n");
    printf ("    offset=1x2 stride=1x1 count=3x4 block=1x1\n");
    for (j = 0; j < DIM0_SUB; j++) {
	for (i = 0; i < DIM1_SUB; i++)
	   sdata[j][i] = 5;
    }     

    status = H5Dwrite (dataset_id, H5T_NATIVE_INT, memspace_id,
                       dataspace_id, H5P_DEFAULT, sdata);
    
    status = H5Dread (dataset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL,
                       H5P_DEFAULT, rdata);

    printf ("\nData in File after Subset is Written:\n");
    for (i = 0; i<DIM0; i++){
       for (j = 0; j<DIM1; j++)
           printf (" %i", rdata[i][j]);
       printf ("\n");
    }

    status = H5Sclose (memspace_id);
    status = H5Sclose (dataspace_id);
    status = H5Dclose (dataset_id);
    status = H5Fclose (file_id);
 
}