hdf5/examples/h5_vds-percival.c

/************************************************************

  This example illustrates the concept of the virtual dataset.
  Percival use case. Every fifth 10x10 plane in VDS is stored in 
  the corresponding 3D unlimited dataset. 
  EIP: For now we will use finite dimension.
  There are 4 source datasets total.
  This file is intended for use with HDF5 Library version 1.10

 ************************************************************/
/* EIP Add link to the picture */

#include "hdf5.h"
#include <stdio.h>
#include <stdlib.h>

#define FILE         "vds-percival.h5"
#define DATASET      "VDS-Percival"
/* later
#define VDSDIM0       H5S_UNLIMITED 
*/
#define VDSDIM0       40
#define VDSDIM1       10 
#define VDSDIM2       10 
/* later
#define DIM0          H5S_UNLIMITED 
*/
#define DIM0          10 
#define DIM1          10 
#define DIM2          10 
#define RANK          3 
#define PLANE_STRIDE  4

const char *SRC_FILE[] = {
    "a.h5",
    "b.h5",
    "c.h5",
    "d.h5"
};

const char *SRC_DATASET[] = {
    "A",
    "B",
    "C",
    "D"
};

int
main (void)
{
    hid_t        file, src_space, vspace,
                 dset;                       /* Handles */
    hid_t        dcpl;
    herr_t       status;
    hsize_t      vdsdims[3] = {VDSDIM0, VDSDIM1, VDSDIM2},
                 vdsdims_max[3] = {VDSDIM0, VDSDIM1, VDSDIM2}, 
                 dims[3] = {DIM0, DIM1, DIM2},
                 dims_max[3] = {DIM0, DIM1, DIM2},
                 start[3],                   /* Hyperslab start parameter for VDS */
                 stride[3],
                 count[3],
                 src_count[3],
                 block[3];
    hsize_t      start_out[3],               /* Hyperslab parameter out */
                 stride_out[3],
                 count_out[3],
                 block_out[3];
    int          i, j;
    H5D_layout_t layout;                     /* Storage layout */
    size_t       num_map;                    /* Number of mappings */
    ssize_t      len;                        /* Length of the string; also a return value */
    char         *filename;
    char         *dsetname;
    int          wdata[DIM0*DIM1*DIM2];

    /*
     * Create source files and datasets. This step is optional.
     */
    for (i=0; i < PLANE_STRIDE; i++) {
        /*
         * Initialize data for i-th source dataset.
         */
        for (j = 0; j < DIM0*DIM1*DIM2; j++) wdata[j] = i+1;

        /*
         * Create the source files and  datasets. Write data to each dataset and 
         * close all resources.
         */

        file = H5Fcreate (SRC_FILE[i], H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
        src_space = H5Screate_simple (RANK, dims, NULL);
        dset = H5Dcreate2 (file, SRC_DATASET[i], H5T_NATIVE_INT, src_space, H5P_DEFAULT,
                    H5P_DEFAULT, H5P_DEFAULT);
        status = H5Dwrite (dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT,
                    wdata);
        status = H5Sclose (src_space);
        status = H5Dclose (dset);
        status = H5Fclose (file);
    }    

    file = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /* Create VDS dataspace.  */
    vspace = H5Screate_simple (RANK, vdsdims, vdsdims_max);

    /* Create dataspaces for the source dataset. */
    src_space = H5Screate_simple (RANK, dims, dims_max);

    /* Create VDS creation property */
    dcpl = H5Pcreate (H5P_DATASET_CREATE);
     
    /* Initialize hyperslab values */

    start[0] = 0;
    start[1] = 0;
    start[2] = 0;
    stride[0] = PLANE_STRIDE; /* we will select every fifth plane in VDS */
    stride[1] = 1;
    stride[2] = 1;
/* later
    count[0] = H5S_UNLIMITED;
*/
    count[0] = VDSDIM0/4;
    count[1] = 1;
    count[2] = 1;
/* later
    src_count[0] = H5S_UNLIMITED;
*/
    src_count[0] = DIM0;
    src_count[1] = 1;
    src_count[2] = 1;
    block[0] = 1;
    block[1] = DIM1;
    block[2] = DIM2;

    /* 
     * Build the mappings 
     *
     */
    status = H5Sselect_hyperslab (src_space, H5S_SELECT_SET, start, NULL, src_count, block);
    for (i=0; i < PLANE_STRIDE; i++) {
        status = H5Sselect_hyperslab (vspace, H5S_SELECT_SET, start, stride, count, block);
        status = H5Pset_virtual (dcpl, vspace, SRC_FILE[i], SRC_DATASET[i], src_space);
        start[0]++; 
    } 

    H5Sselect_none(vspace); 

    /* Create a virtual dataset */
    dset = H5Dcreate2 (file, DATASET, H5T_NATIVE_INT, vspace, H5P_DEFAULT,
                dcpl, H5P_DEFAULT);
    status = H5Sclose (vspace);
    status = H5Sclose (src_space);
    status = H5Dclose (dset);
    status = H5Fclose (file);    
     
    /*
     * Now we begin the read section of this example.
     */

    /*
     * Open file and dataset using the default properties.
     */
    file = H5Fopen (FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
    dset = H5Dopen2 (file, DATASET, H5P_DEFAULT);

    /*
     * Get creation property list and mapping properties.
     */
    dcpl = H5Dget_create_plist (dset);

    /*
     * Get storage layout.
     */
    layout = H5Pget_layout (dcpl);

    if (H5D_VIRTUAL == layout) 
        printf(" Dataset has a virtual layout \n");
    else
        printf(" Wrong layout found \n");

     /*
      * Find number of mappings.
      */
     status = H5Pget_virtual_count (dcpl, &num_map);
     printf(" Number of mappings is %lu\n", (unsigned long)num_map);

     /* 
      * Get mapping parameters for each mapping.
      */
      for (i = 0; i < (int)num_map; i++) {   
      printf(" Mapping %d \n", i);
      printf("         Selection in the virtual dataset \n");
      /* Get selection in the virttual  dataset */
          vspace = H5Pget_virtual_vspace (dcpl, (size_t)i);
          if (H5Sget_select_type(vspace) == H5S_SEL_HYPERSLABS) { 
              if (H5Sis_regular_hyperslab(vspace)) {
                   status = H5Sget_regular_hyperslab (vspace, start_out, stride_out, count_out, block_out);
                   printf("         start  = [%llu, %llu, %llu] \n", (unsigned long long)start_out[0], (unsigned long long)start_out[1], (unsigned long long)start_out[2]);
                   printf("         stride = [%llu, %llu, %llu] \n", (unsigned long long)stride_out[0], (unsigned long long)stride_out[1], (unsigned long long)stride_out[2]);
                   printf("         count  = [%llu, %llu, %llu] \n", (unsigned long long)count_out[0], (unsigned long long)count_out[1], (unsigned long long)count_out[2]);
                   printf("         block  = [%llu, %llu, %llu] \n", (unsigned long long)block_out[0], (unsigned long long)block_out[1], (unsigned long long)block_out[2]);
               }
          }
      /* Get source file name */
          len = H5Pget_virtual_filename (dcpl, (size_t)i, NULL, 0);
          filename = (char *)malloc((size_t)len*sizeof(char)+1);
          H5Pget_virtual_filename (dcpl, (size_t)i, filename, len+1);
          printf("         Source filename %s\n", filename);

      /* Get source dataset name */
          len = H5Pget_virtual_dsetname (dcpl, (size_t)i, NULL, 0);
          dsetname = (char *)malloc((size_t)len*sizeof(char)+1);
          H5Pget_virtual_dsetname (dcpl, (size_t)i, dsetname, len+1);
          printf("         Source dataset name %s\n", dsetname);

      /* Get selection in the source dataset */
          printf("         Selection in the source dataset \n");
          src_space = H5Pget_virtual_srcspace (dcpl, (size_t)i);
          if (H5Sget_select_type(src_space) == H5S_SEL_HYPERSLABS) {
              if (H5Sis_regular_hyperslab(src_space)) {
                   status = H5Sget_regular_hyperslab (src_space, start_out, stride_out, count_out, block_out);
                   printf("         start  = [%llu, %llu, %llu] \n", (unsigned long long)start_out[0], (unsigned long long)start_out[1], (unsigned long long)start_out[2]);
                   printf("         stride = [%llu, %llu, %llu] \n", (unsigned long long)stride_out[0], (unsigned long long)stride_out[1], (unsigned long long)stride_out[2]);
                   printf("         count  = [%llu, %llu, %llu] \n", (unsigned long long)count_out[0], (unsigned long long)count_out[1], (unsigned long long)count_out[2]);
                   printf("         block  = [%llu, %llu, %llu] \n", (unsigned long long)block_out[0], (unsigned long long)block_out[1], (unsigned long long)block_out[2]);
               }
          }
          H5Sclose(vspace);
          H5Sclose(src_space);
          free(filename);
          free(dsetname);
      }
    /*
     * Close and release resources.
     */
    status = H5Pclose (dcpl);
    status = H5Dclose (dset);
    status = H5Fclose (file);
    return 0;
}