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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* 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 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, and extracts
the bit field using a given starting bit and number
of bits in the bit-field. The values are returned
as a base-10 integer.
Main illustrative function: H5LTread_bitfield_value
*/
#include <stdlib.h>
#include "hdf5.h"
#include "hdf5_hl.h"
#define filename "ex_bitfield.h5"
#define DIM0 4
#define DIM1 7
#define num_flags 4
int main(void)
{
int qf_data[DIM0][DIM1][num_flags]; /* Read buffer */
unsigned int offset[4] = {0,2,4,6}; /* Starting bits to be extracted from element */
unsigned int length[4] = {2,2,2,2}; /* Number of bits to be extracted for each value */
hid_t file, space; /* Handles */
hid_t qf_dset;
int ndims;
herr_t status;
int rank = 2;
hsize_t dims[2] = {DIM0,DIM1};
hid_t file_id;
unsigned char wdata[DIM0][DIM1]; /* Write buffer */
int i, j, k;
/*
* Initialize data. We will manually fill four 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 file with default file access and file creation properties.
*/
file_id = H5Fcreate(filename, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
/*
* write the data.
*/
status = H5LTmake_dataset ( file_id, "Granule 1", rank, dims, H5T_NATIVE_UCHAR, wdata );
/*
* close the resources.
*/
status = H5Fclose(file_id);
/*
* Open file.
*/
file = H5Fopen (filename, H5F_ACC_RDONLY, H5P_DEFAULT);
/*
* Open the data set
*/
qf_dset = H5Dopen (file, "Granule 1",H5P_DEFAULT );
/*
* Get dataspace and allocate memory for read buffer. Quality flags dataset
* has the same dimensionality as corresponding product dataset;
* we are using its dimensions for illustration purposes only.
*/
space = H5Dget_space (qf_dset);
ndims = H5Sget_simple_extent_dims (space, dims, NULL);
status = H5Sclose (space);
/*
* For each element read the value that takes first two bits and
* store it in a char buffer. This selects all the elements (H5S_ALL)
*/
status = H5LTread_bitfield_value(qf_dset, num_flags, offset, length,
H5S_ALL, qf_data);
/* Print out the bit field */
printf("Bit Field:\n");
for (i = 0; i<DIM0; i++) {
printf (" [");
for (j = 0; j<DIM1; j++) {
printf(" {");
for (k = 0; k<num_flags; k++){
printf(" %d ", qf_data[i][j][k]);
}
printf("} ");
}
printf("]\n");
}
return 0;
}
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