#include "hdf5.h"

#define FILE          "SDScompound.h5"
#define DATASETNAME   "ArrayOfStructures"
#define LENGTH        1
#define RANK          1
#define ITER          100000

int main(void) {

    /* First structure  and dataset*/
    typedef struct s1_t {
      int    a;
      float  b;
      double c;
    } s1_t;

    s1_t       s1[LENGTH];
    hid_t      s1_tid;     /* File datatype identifier */

    int        i=0;
    hid_t      file, dataset, space, filespace, cparms; /* Handles */
    herr_t     status;
    hsize_t    dim[] = { LENGTH };   /* Dataspace dimensions */
    hsize_t    offset[LENGTH], size[LENGTH];   /* Dataspace dimensions */
    hsize_t    maxdims[] = { H5S_UNLIMITED };
    hsize_t    chunk_dims[] = { 1024 }; // what is the best number if I am reading/writing one row at a time

    /*
     * Initialize the data
     */
         s1[i].a = 10;
         s1[i].b = 15;
         s1[i].c = 99.99;
    /*
     * Create the data space.
     */
    space = H5Screate_simple (RANK, dim, maxdims); 

    /*
     * Create the file.
     */
    file = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /* Modify dataset creation properties, i.e. enable chunking  */
    cparms = H5Pcreate (H5P_DATASET_CREATE);
    status = H5Pset_chunk ( cparms, RANK, chunk_dims);

    /*
     * Create the memory data type. 
     */
    s1_tid = H5Tcreate (H5T_COMPOUND, sizeof(s1_t));
    H5Tinsert(s1_tid, "a_name", HOFFSET(s1_t, a), H5T_NATIVE_INT);
    H5Tinsert(s1_tid, "c_name", HOFFSET(s1_t, c), H5T_NATIVE_DOUBLE);
    H5Tinsert(s1_tid, "b_name", HOFFSET(s1_t, b), H5T_NATIVE_FLOAT);

    /* 
     * Create the dataset.
     */
    dataset = H5Dcreate(file, DATASETNAME, s1_tid, space, H5P_DEFAULT,cparms, H5P_DEFAULT);

    /* Extend the dataset to the orig dimension */
    size[0] = dim[0];
    status = H5Dextend (dataset, size);

    /* Select a hyperslab  */
    filespace = H5Dget_space (dataset);
    offset[0] = 0;
    status = H5Sselect_hyperslab (filespace, H5S_SELECT_SET, offset, NULL, dim, NULL);

    /* Write the data to the hyperslab  */    
    status = H5Dwrite (dataset, s1_tid,space, filespace, H5P_DEFAULT, s1);

    for (i = 0; i < ITER; ++i) {

        /* Extend the dataset. Add one more row  */
        ++size[0];  // increase the row size by 1
        status = H5Dextend (dataset, size);

        /* Select a hyperslab  */
        filespace = H5Dget_space (dataset);
        offset[0] = size[0] - 1;   // offset starts at 0
        status = H5Sselect_hyperslab (filespace, H5S_SELECT_SET, offset, NULL, dim, NULL);

        space = H5Screate_simple (RANK, dim, NULL);
        status = H5Dwrite (dataset, s1_tid, space, filespace, H5P_DEFAULT, s1);
        H5Sclose(space);
        // status = H5Fflush(file, H5F_SCOPE_GLOBAL); // program still brings down the system w/ or w/o flush
    }

    /*
     * Release resources
     */
    H5Tclose(s1_tid);
    H5Dclose(dataset);
    H5Fclose(file);

    return 0;
}