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/*
* This example shows how to read data from a chunked dataset.
* We will read from the file created by h5_extend_write.c
*/
#include "hdf5.h"
#define FILE "SDSextendible.h5"
#define DATASETNAME "ExtendibleArray"
#define RANK 2
#define RANKC 1
#define NX 10
#define NY 5
main ()
{
hid_t file; /* handles */
hid_t datatype, dataset;
hid_t filespace;
hid_t memspace;
hid_t cparms;
H5T_class_t class; /* data type class */
size_t elem_size; /* size of the data element
stored in file */
size_t dims[2]; /* dataset and chunk dimensions */
size_t chunk_dims[2];
size_t col_dims[1];
size_t size[2];
size_t count[2];
int offset[2];
herr_t status, status_n;
int data_out[NX][NY]; /* buffer for dataset to be read */
int chunk_out[2][5]; /* buffer for chunk to be read */
int column[10]; /* buffer for column to be read */
int i, j, rank, rank_chunk;
/*
* Open the file and the dataset.
*/
file = H5Fopen(FILE, H5F_ACC_RDONLY, H5C_DEFAULT);
dataset = H5Dopen(file, DATASETNAME);
/*
* Get dataset rank and dimension.
*/
filespace = H5Dget_space(dataset); /* Get filespace handle first. */
rank = H5Pget_ndims(filespace);
status_n = H5Pget_dims(filespace, dims);
printf("dataset rank %d, dimensions %d x %d \n", rank, dims[0], dims[1]);
/*
* Get creation properties.
*/
cparms = H5Dget_create_parms(dataset); /* Get properties handle first. */
/*
* Check if dataset is chunked.
*/
if (H5D_CHUNKED == H5Cget_layout(cparms)) {
/*
* Get chunking information: rank and dimensions
*/
rank_chunk = H5Cget_chunk(cparms, 2, chunk_dims);
printf("chunk rank %d, dimensions %d x %d \n", rank_chunk,
chunk_dims[0], chunk_dims[1]);
}
/*
* Define the memory space to read dataset.
*/
memspace = H5Pcreate_simple(RANK,dims,NULL);
/*
* Read dataset back and display.
*/
status = H5Dread(dataset, H5T_NATIVE_INT, memspace, filespace,
H5C_DEFAULT, data_out);
printf("\n");
printf("Dataset: \n");
for (j = 0; j < dims[0]; j++) {
for (i = 0; i < dims[1]; i++) printf("%d ", data_out[j][i]);
printf("\n");
}
/*
dataset rank 2, dimensions 10 x 5
chunk rank 2, dimensions 2 x 5
Dataset:
1 1 1 3 3
1 1 1 3 3
1 1 1 0 0
2 0 0 0 0
2 0 0 0 0
2 0 0 0 0
2 0 0 0 0
2 0 0 0 0
2 0 0 0 0
2 0 0 0 0
*/
/*
* Read the third column from the dataset.
* First define memory dataspace, then define hyperslab
* and read it into column array.
*/
col_dims[0] = 10;
memspace = H5Pcreate_simple(RANKC, col_dims, NULL);
/*
* Define the column (hyperslab) to read.
*/
offset[0] = 0;
offset[1] = 2;
count[0] = 10;
count[1] = 1;
status = H5Pset_hyperslab(filespace, offset, count, NULL);
status = H5Dread(dataset, H5T_NATIVE_INT, memspace, filespace,
H5C_DEFAULT, column);
printf("\n");
printf("Third column: \n");
for (i = 0; i < 10; i++) {
printf("%d \n", column[i]);
}
/*
Third column:
1
1
1
0
0
0
0
0
0
0
*/
/*
* Define the memory space to read a chunk.
*/
memspace = H5Pcreate_simple(rank_chunk,chunk_dims,NULL);
/*
* Define chunk in the file (hyperslab) to read.
*/
offset[0] = 2;
offset[1] = 0;
count[0] = chunk_dims[0];
count[1] = chunk_dims[1];
status = H5Pset_hyperslab(filespace, offset, count, NULL);
/*
* Read chunk back and display.
*/
status = H5Dread(dataset, H5T_NATIVE_INT, memspace, filespace,
H5C_DEFAULT, chunk_out);
printf("\n");
printf("Chunk: \n");
for (j = 0; j < chunk_dims[0]; j++) {
for (i = 0; i < chunk_dims[1]; i++) printf("%d ", chunk_out[j][i]);
printf("\n");
}
/*
Chunk:
1 1 1 0 0
2 0 0 0 0
*/
/*
* Close/release resources.
*/
H5Cclose(cparms);
H5Dclose(dataset);
H5Pclose(filespace);
H5Pclose(memspace);
H5Fclose(file);
}
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