hdf5/examples/h5_group.c

/*
 * This program creates a group in the file and two datasets in the group. 
 * Hard link to the group object is created and one of the datasets is accessed
 * under new name. 
 * Iterator functions are used to find information about the objects
 * in the root group and in the created group. 
 */ 


#include "hdf5.h"


#define H5FILE_NAME    "group.h5"
#define RANK    2

herr_t file_info(hid_t loc_id, const char *name, void *opdata);
                                     /* Operator function */
herr_t group_info(hid_t loc_id, const char *name, void *opdata);
                                     /* Operator function */
int
main(void)
{

    hid_t    file;
    hid_t    grp;
    hid_t    dataset, dataspace;
    hid_t    plist; 

    herr_t   status;
    hsize_t  dims[2];
    hsize_t  cdims[2];
 
    int      idx_f, idx_g;

    /*
     * Create a file.
     */
    file = H5Fcreate(H5FILE_NAME, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create a group in the file. 
     */
    grp = H5Gcreate(file, "/Data", 0);

    /*
     * Create dataset "Compressed Data" in the group using absolute
     * name. Dataset creation property list is modified to use 
     * GZIP compression with the compression effort set to 6. 
     * Note that compression can be used only when dataset is chunked. 
     */
    dims[0] = 1000;
    dims[1] = 20;
    cdims[0] = 20;
    cdims[1] = 20;
    dataspace = H5Screate_simple(RANK, dims, NULL);
    plist     = H5Pcreate(H5P_DATASET_CREATE);
                H5Pset_chunk(plist, 2, cdims);
                H5Pset_deflate( plist, 6); 
    dataset = H5Dcreate(file, "/Data/Compressed_Data", H5T_NATIVE_INT, 
                        dataspace, plist); 
    /* 
     * Close the first dataset .
     */
    H5Sclose(dataspace);
    H5Dclose(dataset);

    /* 
     * Create the second dataset.
     */
    dims[0] = 500;
    dims[1] = 20;
    dataspace = H5Screate_simple(RANK, dims, NULL);
    dataset = H5Dcreate(file, "/Data/Float_Data", H5T_NATIVE_FLOAT,
			dataspace, H5P_DEFAULT);

    /* 
     *Close the second dataset and file.
     */
    H5Sclose(dataspace);
    H5Dclose(dataset);
    H5Fclose(file);

    /*
     * Now reopen the file and group in the file. 
     */
    file = H5Fopen(H5FILE_NAME, H5F_ACC_RDWR, H5P_DEFAULT);
    grp  = H5Gopen(file, "Data");

    /* 
     * Access "Compressed_Data" dataset in the group. 
     */
    dataset = H5Dopen(grp, "Compressed_Data");
    if( dataset < 0) printf(" Dataset 'Compressed-Data' is not found. \n");
    printf("\"/Data/Compressed_Data\" dataset is open \n");

    /*
     * Close the dataset.
     */
    status = H5Dclose(dataset);

    /*
     * Create hard link to the Data group.
     */
    status = H5Glink(file, H5G_LINK_HARD, "Data", "Data_new");

    /* 
     * We can access "Compressed_Data" dataset using created
     * hard link "Data_new". 
     */
    dataset = H5Dopen(file, "/Data_new/Compressed_Data");
    if( dataset < 0) printf(" Dataset is not found. \n");
    printf("\"/Data_new/Compressed_Data\" dataset is open \n");

    /*
     * Close the dataset.
     */
    status = H5Dclose(dataset);


    /* 
     * Use iterator to see the names of the objects in the root group.
     */
    idx_f = H5Giterate(file, "/", NULL, file_info, NULL);

    /*
     * Unlink  name "Data" and use iterator to see the names
     * of the objects in the file root direvtory.
     */
    if (H5Gunlink(file, "Data") < 0)  
      printf(" H5Gunlink failed \n");
    else  
      printf("\"Data\" is unlinked \n");

    idx_f = H5Giterate(file, "/", NULL, file_info, NULL);

    /* 
     * Use iterator to see the names of the objects in the group 
     * /Data_new.
     */
    idx_g = H5Giterate(grp, "/Data_new", NULL, group_info, NULL);

    /*
     * Close the file.
     */
     
    status = H5Fclose(file);

    return 0;
}

/*
 * Operator function.
 */
herr_t file_info(hid_t loc_id, const char *name, void *opdata)
{
    /* avoid warnings */
    loc_id = loc_id;
    opdata = opdata;

    /*
     * Display group name. The name is passed to the function by 
     * the Library. Some magic :-)
     */
    printf("\n");
    printf("Name : ");
    puts(name);
    
    return 0;
 }


/*
 * Operator function.
 */
herr_t group_info(hid_t loc_id, const char *name, void *opdata)
{
  hid_t did;  /* dataset identifier  */
  hid_t tid;  /* datatype identifier */
  H5T_class_t t_class;
  hid_t pid;  /* data_property identifier */
  hsize_t chunk_dims_out[2];

  int  rank_chunk;

  /* avoid warnings */
  opdata = opdata;

  /*
   * Open the datasets using their names.
   */
  did = H5Dopen(loc_id, name);
 
  /*
   * Display dataset name.
   */
  printf("\n");
  printf("Name : ");
  puts(name);
  
  /*    
   * Display dataset information.
   */
  tid = H5Dget_type(did);  /* get datatype*/
  pid = H5Dget_create_plist(did); /* get creation property list */
  
  /*
   * Check if dataset is chunked.
   */
  if(H5D_CHUNKED == H5Pget_layout(pid)){
    /*
     * get chunking information: rank and dimensions.
     */
    rank_chunk = H5Pget_chunk(pid, 2, chunk_dims_out);
    printf("chunk rank %d, dimensions %lu x %lu\n", rank_chunk, 
	   (unsigned long)(chunk_dims_out[0]),
	   (unsigned long)(chunk_dims_out[1]));
  } 
  else{
    t_class = H5Tget_class(tid);
    if(t_class < 0){ 
      puts(" Invalid datatype.\n");
    }
    else {
      if(t_class == H5T_INTEGER)
      puts(" Datatype is 'H5T_NATIVE_INTEGER'.\n");
      if(t_class == H5T_FLOAT)
      puts(" Datatype is 'H5T_NATIVE_FLOAT'.\n");
      if(t_class == H5T_STRING)
      puts(" Datatype is 'H5T_NATIVE_STRING'.\n");
      if(t_class == H5T_BITFIELD)
      puts(" Datatype is 'H5T_NATIVE_BITFIELD'.\n");
      if(t_class == H5T_OPAQUE)
      puts(" Datatype is 'H5T_NATIVE_OPAQUE'.\n");
      if(t_class == H5T_COMPOUND)
      puts(" Datatype is 'H5T_NATIVE_COMPOUND'.\n");
    }
  }
    

  H5Dclose(did);
  H5Pclose(pid);
  H5Tclose(tid);
  return 0;
 }