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

  This example shows how to read and write bitfield
  datatypes to a dataset.  The program first writes bit
  fields to a dataset with a dataspace of DIM0xDIM1, then
  closes the file.  Next, it reopens the file, reads back
  the data, and outputs it to the screen.

  This file is intended for use with HDF5 Library version 1.6

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

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

#define FILE    "h5ex_t_bit.h5"
#define DATASET "DS1"
#define DIM0    4
#define DIM1    7

int
main(void)
{
    hid_t         file, space, dset; /* Handles */
    herr_t        status;
    hsize_t       dims[2] = {DIM0, DIM1};
    unsigned char wdata[DIM0][DIM1], /* Write buffer */
        **rdata;                     /* Read buffer */
    int ndims, A, B, C, D, i, j;

    /*
     * Initialize data.  We will manually pack 4 2-bit integers into
     * each unsigned char data element.
     */
    for (i = 0; i < DIM0; i++)
        for (j = 0; j < DIM1; j++) {
            wdata[i][j] = 0;
            wdata[i][j] |= (i * j - j) & 0x03;    /* Field "A" */
            wdata[i][j] |= (i & 0x03) << 2;       /* Field "B" */
            wdata[i][j] |= (j & 0x03) << 4;       /* Field "C" */
            wdata[i][j] |= ((i + j) & 0x03) << 6; /* Field "D" */
        }

    /*
     * 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 and write the bitfield data to it.
     */
    dset   = H5Dcreate(file, DATASET, H5T_STD_B8BE, space, H5P_DEFAULT);
    status = H5Dwrite(dset, H5T_NATIVE_B8, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata[0]);

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

    /*
     * Now we begin the read section of this example.  Here we assume
     * the dataset has the same name and rank, but can have any size.
     * Therefore we must allocate a new array to read in data using
     * malloc().
     */

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

    /*
     * Get dataspace and allocate memory for read buffer.  This is a
     * two dimensional dataset so the dynamic allocation must be done
     * in steps.
     */
    space = H5Dget_space(dset);
    ndims = H5Sget_simple_extent_dims(space, dims, NULL);

    /*
     * Allocate array of pointers to rows.
     */
    rdata = (unsigned char **)malloc(dims[0] * sizeof(unsigned char *));

    /*
     * Allocate space for bitfield data.
     */
    rdata[0] = (unsigned char *)malloc(dims[0] * dims[1] * sizeof(unsigned char));

    /*
     * Set the rest of the pointers to rows to the correct addresses.
     */
    for (i = 1; i < dims[0]; i++)
        rdata[i] = rdata[0] + i * dims[1];

    /*
     * Read the data.
     */
    status = H5Dread(dset, H5T_NATIVE_B8, H5S_ALL, H5S_ALL, H5P_DEFAULT, rdata[0]);

    /*
     * Output the data to the screen.
     */
    printf("%s:\n", DATASET);
    for (i = 0; i < dims[0]; i++) {
        printf(" [");
        for (j = 0; j < dims[1]; j++) {
            A = rdata[i][j] & 0x03;        /* Retrieve field "A" */
            B = (rdata[i][j] >> 2) & 0x03; /* Retrieve field "B" */
            C = (rdata[i][j] >> 4) & 0x03; /* Retrieve field "C" */
            D = (rdata[i][j] >> 6) & 0x03; /* Retrieve field "D" */
            printf(" {%d, %d, %d, %d}", A, B, C, D);
        }
        printf(" ]\n");
    }

    /*
     * Close and release resources.
     */
    free(rdata[0]);
    free(rdata);
    status = H5Dclose(dset);
    status = H5Sclose(space);
    status = H5Fclose(file);

    return 0;
}
