/*
 *   This example opens an NPP example file and reads a dataset with region references 
 *   VIIRS-MOD_GTM-EDR-GEO_Gran_0 under the /Data_Products/VIIRS-MOD-GTM-EDR-GEO group. 
 *   Then it finds information about the selected elements pointed by the third reference 
 *   and reads the data in.  
 *   Main illustrative functions: H5LRget_region_info, H5LRread_region
 */
#include <stdlib.h>
#include "hdf5.h"
#include "hdf5_hl.h"
#include "H5LTpublic.h"
#include "h5hl_region.h"

#define filename "GMGTO_npp_d20030125_t0657104_e0659047_b00014_c20090811150425926728_unkn_SCI.h5"
#define dsetname "/Data_Products/VIIRS-MOD-GTM-EDR-GEO/VIIRS-MOD-GTM-EDR-GEO_Gran_0"     /* dataset with region references */


int main(void)
{
    hid_t file_id;           /* file identifier */
    hid_t dset_id;       /* region reference dataset identifier */
    hsize_t dims[1] =  {15}; /* size of the VIIRS-MOD_GTM-EDR-GEO_Gran_0 dataset */
    hdset_reg_ref_t ref[15]; /* array to read region references */
    hsize_t buf[4];          /* buffer to read hyperslab coordinates defining region references */
    herr_t status;
    size_t name_length = {1024};
    char name[1024];
    hid_t dtype;
    size_t numelem;
    char type_string[15];
    size_t type_string_length = {15};
    hsize_t rdims[2];
    float *rdata;
    size_t rnumelem;
    int i;
    

    /*
     * Open the NPP file.
     */
    file_id = H5Fopen(filename, H5F_ACC_RDWR, H5P_DEFAULT);
    /*
     * Open dataset and read the dataset with the region references.
     * We made an assumption that the size of the dataset is known.
     */
    dset_id = H5Dopen(file_id, dsetname, H5P_DEFAULT);
    status = H5Dread(dset_id, H5T_STD_REF_DSETREG, H5S_ALL, H5S_ALL, H5P_DEFAULT,ref); 

    /* 
     * Get region reference information such as a name of the dataset the region reference point to,
     * number of contiguous blocks in the selection (should be 1) and the hyperslab coordinates (0,0) - (770,4120)
     */
    status = H5LRget_region_info(file_id, (const hdset_reg_ref_t*)ref[2], &name_length, name, NULL, &dtype,
				 NULL, &numelem, buf);

    /*
     * Display the info
     */
    H5LTdtype_to_text(dtype, type_string, H5LT_DDL, &type_string_length);
    printf(" Information retrieved by H5LRget_region_info: \n");
    printf(" Third element of the array with the region references points to  %s \n", name);
    printf(" Length of the string above is %d \n", (int)name_length); 
    printf(" Region's datatype is %s \n", type_string);
    printf(" Number of blocks in the region is %d \n", (int)numelem);
    printf(" Block's coordinates are (%d,%d) - (%d,%d) \n", (int)buf[0],(int)buf[1],(int)buf[2],(int)buf[3]);
    printf("\n");

    /*
     * We will read data to the floating-point buffer; using information provided by H5LRget_region_info
     * allocate the buffer to read data in.
     */
    rdims[0] = buf[2] - buf[0] + 1;
    rdims[1] = buf[3] - buf[1] + 1;
    rdata = (float *) malloc (rdims[0] * rdims[1] * sizeof(float));

    /*
     * Read data pointed by the third region reference into a buffer and display the first six elements.
     */
    status = H5LRread_region(file_id,(const hdset_reg_ref_t*)ref[2], H5T_NATIVE_FLOAT, &rnumelem, rdata);
    printf(" Information retrieved by H5LRread_region: \n");
    printf(" Number of elements pointed by a region reference is %ld \n", rnumelem);
    printf(" The first six elements are: \n");
    for (i=0; i<6; i++) printf(" %7.3f ", rdata[i]);
    printf("\n");
    free(rdata);

    /*
     * Close dataset with region references and file.
     */
    status = H5Dclose(dset_id);
    status = H5Fclose(file_id);

    return 0;
}