h5ex_d_checksum.c

/************************************************************

  This example shows how to read and write data to a dataset
  using the Fletcher32 checksum filter.  The program first
  checks if the Fletcher32 filter is available, then if it
  is it writes integers to a dataset using Fletcher32, then
  closes the file.  Next, it reopens the file, reads back
  the data, checks if the filter detected an error and
  outputs the type of filter and the maximum value in the
  dataset to the screen.

 ************************************************************/

#include "hdf5.h"
#include <stdio.h>
#include <stdlib.h>

#define FILE    "h5ex_d_checksum.h5"
#define DATASET "DS1"
#define DIM0    32
#define DIM1    64
#define CHUNK0  4
#define CHUNK1  8

int
main(void)
{
    hid_t file  = H5I_INVALID_HID;
    hid_t space = H5I_INVALID_HID;
    hid_t dset  = H5I_INVALID_HID;
    hid_t dcpl  = H5I_INVALID_HID;
    /* Handles */
    herr_t       status;
    htri_t       avail;
    H5Z_filter_t filter_type;
    hsize_t      dims[2] = {DIM0, DIM1}, chunk[2] = {CHUNK0, CHUNK1};
    size_t       nelmts;
    unsigned int flags, filter_info;
    int          wdata[DIM0][DIM1]; /* Write buffer */
    int          rdata[DIM0][DIM1]; /* Read buffer */
    int          max;
    hsize_t      i, j;

    /*
     * Check if the Fletcher32 filter is available and can be used for
     * both encoding and decoding.  Normally we do not perform error
     * checking in these examples for the sake of clarity, but in this
     * case we will make an exception because this filter is an
     * optional part of the hdf5 library.
     */
    avail = H5Zfilter_avail(H5Z_FILTER_FLETCHER32);
    if (!avail) {
        printf("Fletcher32 filter not available.\n");
        return 1;
    }
    status = H5Zget_filter_info(H5Z_FILTER_FLETCHER32, &filter_info);
    if (!(filter_info & H5Z_FILTER_CONFIG_ENCODE_ENABLED) ||
        !(filter_info & H5Z_FILTER_CONFIG_DECODE_ENABLED)) {
        printf("Fletcher32 filter not available for encoding and decoding.\n");
        return 1;
    }

    /*
     * Initialize data.
     */
    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++)
            wdata[i][j] = i * j - j;

    /*
     * Create a new file using the default properties.
     */
    file = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create dataspace.  Setting maximum size to NULL sets the maximum
     * size to be the current size.
     */
    space = H5Screate_simple(2, dims, NULL);

    /*
     * Create the dataset creation property list, add the Fletcher32 filter
     * and set the chunk size.
     */
    dcpl   = H5Pcreate(H5P_DATASET_CREATE);
    status = H5Pset_fletcher32(dcpl);
    status = H5Pset_chunk(dcpl, 2, chunk);

    /*
     * Create the dataset.
     */
    dset = H5Dcreate(file, DATASET, H5T_STD_I32LE, space, H5P_DEFAULT, dcpl, H5P_DEFAULT);

    /*
     * Write the data to the dataset.
     */
    status = H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata[0]);

    /*
     * Close and release resources.
     */
    status = H5Pclose(dcpl);
    status = H5Dclose(dset);
    status = H5Sclose(space);
    status = H5Fclose(file);

    /*
     * Now we begin the read section of this example.
     */

    /*
     * Open file and dataset using the default properties.
     */
    file = H5Fopen(FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
    dset = H5Dopen(file, DATASET, H5P_DEFAULT);

    /*
     * Retrieve dataset creation property list.
     */
    dcpl = H5Dget_create_plist(dset);

    /*
     * Retrieve and print the filter type.  Here we only retrieve the
     * first filter because we know that we only added one filter.
     */
    nelmts      = 0;
    filter_type = H5Pget_filter(dcpl, 0, &flags, &nelmts, NULL, 0, NULL, &filter_info);
    printf("Filter type is: ");
    switch (filter_type) {
        case H5Z_FILTER_DEFLATE:
            printf("H5Z_FILTER_DEFLATE\n");
            break;
        case H5Z_FILTER_SHUFFLE:
            printf("H5Z_FILTER_SHUFFLE\n");
            break;
        case H5Z_FILTER_FLETCHER32:
            printf("H5Z_FILTER_FLETCHER32\n");
            break;
        case H5Z_FILTER_SZIP:
            printf("H5Z_FILTER_SZIP\n");
            break;
        case H5Z_FILTER_NBIT:
            printf("H5Z_FILTER_NBIT\n");
            break;
        case H5Z_FILTER_SCALEOFFSET:
            printf("H5Z_FILTER_SCALEOFFSET\n");
    }

    /*
     * Read the data using the default properties.
     */
    status = H5Dread(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, rdata[0]);

    /*
     * Check if the read was successful.  Normally we do not perform
     * error checking in these examples for the sake of clarity, but in
     * this case we will make an exception because this is how the
     * fletcher32 checksum filter reports data errors.
     */
    if (status < 0) {
        fprintf(stderr, "Dataset read failed!\n");
        status = H5Pclose(dcpl);
        status = H5Dclose(dset);
        status = H5Fclose(file);
        return 2;
    }

    /*
     * Find the maximum value in the dataset, to verify that it was
     * read correctly.
     */
    max = rdata[0][0];
    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++)
            if (max < rdata[i][j])
                max = rdata[i][j];

    /*
     * Print the maximum value.
     */
    printf("Maximum value in %s is: %d\n", DATASET, max);

    /*
     * Close and release resources.
     */
    status = H5Pclose(dcpl);
    status = H5Dclose(dset);
    status = H5Fclose(file);

    return 0;
}