h5ex_t_cmpdatt.c

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

  This example shows how to read and write compound
  datatypes to an attribute.  The program first writes
  compound structures to an attribute with a dataspace of
  DIM0, then closes the file.  Next, it reopens the file,
  reads back the data, and outputs it to the screen.

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

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

#define FILE      "h5ex_t_cmpdatt.h5"
#define DATASET   "DS1"
#define ATTRIBUTE "A1"
#define DIM0      4

typedef struct {
    int    serial_no;
    char  *location;
    double temperature;
    double pressure;
} sensor_t; /* Compound type */

int
main(void)
{
    hid_t file, filetype, memtype, strtype, space, dset, attr;
    /* Handles */
    herr_t   status;
    hsize_t  dims[1] = {DIM0};
    sensor_t wdata[DIM0], /* Write buffer */
        *rdata;           /* Read buffer */
    int     ndims;
    hsize_t i;

    /*
     * Initialize data.
     */
    wdata[0].serial_no   = 1153;
    wdata[0].location    = "Exterior (static)";
    wdata[0].temperature = 53.23;
    wdata[0].pressure    = 24.57;
    wdata[1].serial_no   = 1184;
    wdata[1].location    = "Intake";
    wdata[1].temperature = 55.12;
    wdata[1].pressure    = 22.95;
    wdata[2].serial_no   = 1027;
    wdata[2].location    = "Intake manifold";
    wdata[2].temperature = 103.55;
    wdata[2].pressure    = 31.23;
    wdata[3].serial_no   = 1313;
    wdata[3].location    = "Exhaust manifold";
    wdata[3].temperature = 1252.89;
    wdata[3].pressure    = 84.11;

    /*
     * Create a new file using the default properties.
     */
    file = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);

    /*
     * Create variable-length string datatype.
     */
    strtype = H5Tcopy(H5T_C_S1);
    status  = H5Tset_size(strtype, H5T_VARIABLE);

    /*
     * Create the compound datatype for memory.
     */
    memtype = H5Tcreate(H5T_COMPOUND, sizeof(sensor_t));
    status  = H5Tinsert(memtype, "Serial number", HOFFSET(sensor_t, serial_no), H5T_NATIVE_INT);
    status  = H5Tinsert(memtype, "Location", HOFFSET(sensor_t, location), strtype);
    status  = H5Tinsert(memtype, "Temperature (F)", HOFFSET(sensor_t, temperature), H5T_NATIVE_DOUBLE);
    status  = H5Tinsert(memtype, "Pressure (inHg)", HOFFSET(sensor_t, pressure), H5T_NATIVE_DOUBLE);

    /*
     * Create the compound datatype for the file.  Because the standard
     * types we are using for the file may have different sizes than
     * the corresponding native types, we must manually calculate the
     * offset of each member.
     */
    filetype = H5Tcreate(H5T_COMPOUND, 8 + sizeof(hvl_t) + 8 + 8);
    status   = H5Tinsert(filetype, "Serial number", 0, H5T_STD_I64BE);
    status   = H5Tinsert(filetype, "Location", 8, strtype);
    status   = H5Tinsert(filetype, "Temperature (F)", 8 + sizeof(hvl_t), H5T_IEEE_F64BE);
    status   = H5Tinsert(filetype, "Pressure (inHg)", 8 + sizeof(hvl_t) + 8, H5T_IEEE_F64BE);

    /*
     * Create dataset with a null dataspace.
     */
    space  = H5Screate(H5S_NULL);
    dset   = H5Dcreate(file, DATASET, H5T_STD_I32LE, space, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
    status = H5Sclose(space);

    /*
     * Create dataspace.  Setting maximum size to NULL sets the maximum
     * size to be the current size.
     */
    space = H5Screate_simple(1, dims, NULL);

    /*
     * Create the attribute and write the compound data to it.
     */
    attr   = H5Acreate(dset, ATTRIBUTE, filetype, space, H5P_DEFAULT, H5P_DEFAULT);
    status = H5Awrite(attr, memtype, wdata);

    /*
     * Close and release resources.
     */
    status = H5Aclose(attr);
    status = H5Dclose(dset);
    status = H5Sclose(space);
    status = H5Tclose(filetype);
    status = H5Fclose(file);

    /*
     * Now we begin the read section of this example.  Here we assume
     * the attribute has the same name and rank, but can have any size.
     * Therefore we must allocate a new array to read in data using
     * malloc().  For simplicity, we do not rebuild memtype.
     */

    /*
     * Open file, dataset, and attribute.
     */
    file = H5Fopen(FILE, H5F_ACC_RDONLY, H5P_DEFAULT);
    dset = H5Dopen(file, DATASET, H5P_DEFAULT);
    attr = H5Aopen(dset, ATTRIBUTE, H5P_DEFAULT);

    /*
     * Get dataspace and allocate memory for read buffer.
     */
    space = H5Aget_space(attr);
    ndims = H5Sget_simple_extent_dims(space, dims, NULL);
    rdata = (sensor_t *)malloc(dims[0] * sizeof(sensor_t));

    /*
     * Read the data.
     */
    status = H5Aread(attr, memtype, rdata);

    /*
     * Output the data to the screen.
     */
    for (i = 0; i < dims[0]; i++) {
        printf("%s[%" PRIuHSIZE "]:\n", ATTRIBUTE, i);
        printf("Serial number   : %d\n", rdata[i].serial_no);
        printf("Location        : %s\n", rdata[i].location);
        printf("Temperature (F) : %f\n", rdata[i].temperature);
        printf("Pressure (inHg) : %f\n\n", rdata[i].pressure);
    }

    /*
     * Close and release resources.  H5Dvlen_reclaim will automatically
     * traverse the structure and free any vlen data (strings in this
     * case).
     */
    status = H5Dvlen_reclaim(memtype, space, H5P_DEFAULT, rdata);
    free(rdata);
    status = H5Aclose(attr);
    status = H5Dclose(dset);
    status = H5Sclose(space);
    status = H5Tclose(memtype);
    status = H5Tclose(strtype);
    status = H5Fclose(file);

    return 0;
}