The HDF5 Group interface has a function, H5Giterate, to iterate over the group members.
Operations on each group member can be performed during the iteration process. The operator function and its data are passed to the iterator as parameters. There are no restrictions on what kind of operations can be performed on group members during the iteration procedure.
The following steps are involved:
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#include <hdf5.h>
#define FILE "iterate.h5"
#define FALSE 0
/* 1-D dataset with fixed dimensions */
#define SPACE1_NAME "Space1"
#define SPACE1_RANK 1
#define SPACE1_DIM1 4
herr_t file_info(hid_t loc_id, const char *name, void *opdata);
/* Operator function */
int
main(void) {
hid_t file; /* HDF5 File IDs */
hid_t dataset; /* Dataset ID */
hid_t group; /* Group ID */
hid_t sid; /* Dataspace ID */
hid_t tid; /* Datatype ID */
hsize_t dims[] = {SPACE1_DIM1};
herr_t ret; /* Generic return value */
/* Compound datatype */
typedef struct s1_t {
unsigned int a;
unsigned int b;
float c;
} s1_t;
/* Create file */
file = H5Fcreate(FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
/* Create dataspace for datasets */
sid = H5Screate_simple(SPACE1_RANK, dims, NULL);
/* Create a group */
group=H5Gcreate(file,"Group1",-1);
/* Close a group */
ret = H5Gclose(group);
/* Create a dataset */
dataset=H5Dcreate(file,"Dataset1",H5T_STD_U32LE,sid,H5P_DEFAULT);
/* Close Dataset */
ret = H5Dclose(dataset);
/* Create a datatype */
tid = H5Tcreate (H5T_COMPOUND, sizeof(s1_t));
/* Insert fields */
ret=H5Tinsert (tid, "a", HOFFSET(s1_t,a), H5T_NATIVE_INT);
ret=H5Tinsert (tid, "b", HOFFSET(s1_t,b), H5T_NATIVE_INT);
ret=H5Tinsert (tid, "c", HOFFSET(s1_t,c), H5T_NATIVE_FLOAT);
/* Save datatype for later */
ret=H5Tcommit (file, "Datatype1", tid);
/* Close datatype */
ret = H5Tclose(tid);
/* Iterate through the file to see members of the root group */
printf(" Objects in the root group are:\n");
printf("\n");
H5Giterate(file, "/", NULL, file_info, NULL);
/* Close file */
ret = H5Fclose(file);
return 0;
}
/*
* Operator function.
*/
herr_t file_info(hid_t loc_id, const char *name, void *opdata)
{
H5G_stat_t statbuf;
/*
* Get type of the object and display its name and type.
* The name of the object is passed to this function by
* the Library. Some magic :-)
*/
H5Gget_objinfo(loc_id, name, FALSE, &statbuf);
switch (statbuf.type) {
case H5G_GROUP:
printf(" Object with name %s is a group \n", name);
break;
case H5G_DATASET:
printf(" Object with name %s is a dataset \n", name);
break;
case H5G_TYPE:
printf(" Object with name %s is a named datatype \n", name);
break;
default:
printf(" Unable to identify an object ");
}
return 0;
}
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The output of this program is:
Objects in the root group are: Object with name Dataset1 is a dataset Object with name Datatype1 is a named datatype Object with name Group1 is a group +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
herr_t *(H5G_operator_t) (hid_group_id, const char* name, void *operator_data)
The operator return value defines the behavior of the iterator.
In this example the operator function returns 0, which causes the iterator to continue and go through all group members.
The signature of this function is as follows:
herr_t H5Gget_objinfo(hid_t loc_id, const char * name, hbool_t follow_link,
H5G_stat_t *statbuf)
int H5Giterate(hid_t loc_id, const char *name , idx,
H5G_operator_t operator, void * operator_data)