/**
@file hdf5Compound.c
@author Mitch Richling
@Copyright Copyright 1998 by Mitch Richling. All rights reserved.
@brief Use of HDF5 compound data types.@EOL
@Keywords hdf5 compound types database db
@Std C89 HDF5
This example program demonstrates the details of
creating and using HDF5 compound types (think structs)
that can be stored into an HDF5 array on disk.
The C structs often have "holes" in them because of
hardware word alignment requirements. This example
illustrates a struct that has holes on most modern
architectures, and how to use an H5T_COMPOUND type to
"mirror" the in-RAM layout of this C struct. In
addition, this program illustrates how to use
H5T_COMPOUND types to represent such a structure on disk
in a platform independent, space efficient (no holes),
manner -- this causes a performance hit because of the
required layout conversion upon read/write.
Compound types may be used to simulate the record/field
structure of a database table with HDF5; however, the
HDF5 high level table API is probably a more direct
approach to this particular application. For such an
approach, see hdf5Table.c.
*/
#include /* I/O lib ISOC */
#include /* Strings ISOC */
#include /* HDF5 files */
#include "mjrHDF5.h"
/* This struct can be "tuned" to have "holes" on just about any
hardware platform. It is thus a good example of how to create HDF5
compound data types that describe things in memory vs. describing
them on disk in a portable way.*/
#define PR_NAME_LEN 32
typedef struct personRecordStr {
char name[PR_NAME_LEN];
unsigned char age;
int weight;
float IQ;
} personRecord_t;
#define NUM_RECS 10000
#define TST_FILE_NAME "aCpndtestFile.h5"
int main(int argc, char *argv[]);
int main(int argc, char *argv[]) {
personRecord_t aPersonArr[NUM_RECS];
hid_t memoryPersonRecordTypeID, diskPersonRecordTypeID;
hid_t stringTypeID;
int offset;
hsize_t numRecs = NUM_RECS;
int i;
hid_t fileID, datasetID, dataspaceID;
herr_t hErrVal;
hsize_t chunkDims = NUM_RECS;
hid_t dataSetPList;
int sizeOfParts, sizeOfWhole;
/* We can test for holes by comparing the struct size to the size
of the components. */
sizeOfParts = (int)(sizeof(char)*33+sizeof(int)+sizeof(float));
sizeOfWhole = (int)(sizeof(personRecord_t));
printf("sizeof(personRecord_t)=%d\n", sizeOfWhole);
printf("sizeof(char[PR_NAME_LEN]+char+int+float)=%d\n", sizeOfParts);
if(sizeOfWhole > sizeOfParts)
printf("A personRecord_t HAS holes!\n");
else
printf("A personRecord_t has NO holes!\n");
/* Fill in some bogus data for the the array. */
for(i=0;i