hdf5/HDF5Examples/C/H5D/h5ex_d_chunk.c

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

  This example shows how to create a chunked dataset.  The
  program first writes integers in a hyperslab selection to
  a chunked dataset with dataspace dimensions of DIM0xDIM1
  and chunk size of CHUNK0xCHUNK1, then closes the file.
  Next, it reopens the file, reads back the data, and
  outputs it to the screen.  Finally it reads the data again
  using a different hyperslab selection, and outputs
  the result to the screen.

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

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

#define FILE    "h5ex_d_chunk.h5"
#define DATASET "DS1"
#define DIM0    6
#define DIM1    8
#define CHUNK0  4
#define CHUNK1  4

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;
    herr_t       status;
    H5D_layout_t layout;
    hsize_t      dims[2]  = {DIM0, DIM1};
    hsize_t      chunk[2] = {CHUNK0, CHUNK1};
    hsize_t      start[2];
    hsize_t      stride[2];
    hsize_t      count[2];
    hsize_t      block[2];
    int          wdata[DIM0][DIM1]; /* Write buffer */
    int          rdata[DIM0][DIM1]; /* Read buffer */
    hsize_t      i, j;

    /*
     * Initialize data to "1", to make it easier to see the selections.
     */
    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++)
            wdata[i][j] = 1;

    /*
     * Print the data to the screen.
     */
    printf("Original Data:\n");
    for (i = 0; i < DIM0; i++) {
        printf(" [");
        for (j = 0; j < DIM1; j++)
            printf(" %3d", wdata[i][j]);
        printf("]\n");
    }

    /*
     * 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, and set the chunk
     * size.
     */
    dcpl   = H5Pcreate(H5P_DATASET_CREATE);
    status = H5Pset_chunk(dcpl, 2, chunk);

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

    /*
     * Define and select the first part of the hyperslab selection.
     */
    start[0]  = 0;
    start[1]  = 0;
    stride[0] = 3;
    stride[1] = 3;
    count[0]  = 2;
    count[1]  = 3;
    block[0]  = 2;
    block[1]  = 2;
    status    = H5Sselect_hyperslab(space, H5S_SELECT_SET, start, stride, count, block);

    /*
     * Define and select the second part of the hyperslab selection,
     * which is subtracted from the first selection by the use of
     * H5S_SELECT_NOTB
     */
    block[0] = 1;
    block[1] = 1;
    status   = H5Sselect_hyperslab(space, H5S_SELECT_NOTB, start, stride, count, block);

    /*
     * Write the data to the dataset.
     */
    status = H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, space, 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 the dataset creation property list, and print the
     * storage layout.
     */
    dcpl   = H5Dget_create_plist(dset);
    layout = H5Pget_layout(dcpl);
    printf("\nStorage layout for %s is: ", DATASET);
    switch (layout) {
        case H5D_COMPACT:
            printf("H5D_COMPACT\n");
            break;
        case H5D_CONTIGUOUS:
            printf("H5D_CONTIGUOUS\n");
            break;
        case H5D_CHUNKED:
            printf("H5D_CHUNKED\n");
            break;
#if H5_VERSION_GE(1, 10, 0) && !defined(H5_USE_18_API) && !defined(H5_USE_16_API)
        case H5D_VIRTUAL:
            printf("H5D_VIRTUAL\n");
            break;
#endif
        case H5D_LAYOUT_ERROR:
        case H5D_NLAYOUTS:
            printf("H5D_LAYOUT_ERROR\n");
    }

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

    /*
     * Output the data to the screen.
     */
    printf("\nData as written to disk by hyberslabs:\n");
    for (i = 0; i < DIM0; i++) {
        printf(" [");
        for (j = 0; j < DIM1; j++)
            printf(" %3d", rdata[i][j]);
        printf("]\n");
    }

    /*
     * Initialize the read array.
     */
    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++)
            rdata[i][j] = 0;

    /*
     * Define and select the hyperslab to use for reading.
     */
    space     = H5Dget_space(dset);
    start[0]  = 0;
    start[1]  = 1;
    stride[0] = 4;
    stride[1] = 4;
    count[0]  = 2;
    count[1]  = 2;
    block[0]  = 2;
    block[1]  = 3;
    status    = H5Sselect_hyperslab(space, H5S_SELECT_SET, start, stride, count, block);

    /*
     * Read the data using the previously defined hyperslab.
     */
    status = H5Dread(dset, H5T_NATIVE_INT, H5S_ALL, space, H5P_DEFAULT, rdata[0]);

    /*
     * Output the data to the screen.
     */
    printf("\nData as read from disk by hyperslab:\n");
    for (i = 0; i < DIM0; i++) {
        printf(" [");
        for (j = 0; j < DIM1; j++)
            printf(" %3d", rdata[i][j]);
        printf("]\n");
    }

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

    return 0;
}