H5Ovisit
(
hid_t object_id
,
H5_index_t index_type
,
H5_iter_order_t order
,
H5O_iterate_t op
,
void *op_data
)
H5Ovisit
is a recursive iteration function
to visit the object object_id
and,
if object_id
is a group,
all objects in and below it in an HDF5 file,
thus providing a mechanism for an application to perform
a common set of operations across all of those objects
or a dynamically selected subset.
For non-recursive iteration across the members of a group,
see H5Literate
.
If object_id
is a group identifier,
that group serves as the root of a recursive iteration.
If object_id
is a file identifier, that file’s
root group serves as the root of the recursive iteration.
If object_id
is any other type of object,
such as a dataset or named datatype, there is no iteration.
Two parameters are used to establish the iteration:
index_type
and order
.
index_type
specifies the index to be used.
If the links in a group have not been indexed by the index type,
they will first be sorted by that index then the iteration will begin;
if the links have been so indexed, the sorting step will be
unnecesary, so the iteration may begin more quickly.
Valid values include the following:
H5_INDEX_NAME
| Alpha-numeric index on name | |
H5_INDEX_CRT_ORDER
| Index on creation order |
Note that the index type passed in index_type
is a
best effort setting.
If the application passes in a value indicating iteration in
creation order and a group is encountered that was not tracked
in creation order, that group will be iterated over in
alpha-numeric order by name, or name order.
(Name order is the native order used by the HDF5 Library
and is always available.)
order
specifies the order in which objects are to be
inspected along the index specified in index_type
.
Valid values include the following:
H5_ITER_INC
| Increasing order | |
H5_ITER_DEC
| Decreasing order | |
H5_ITER_NATIVE
| Fastest available order |
The protoype of the callback function op
is as follows
(as defined in the source code file H5Opublic.h
):
(*H5O_iterate_t)(
hid_t o_id,
const char *name,
const H5O_info_t *object_info,
void *op_data)
The parameters of this callback function have the following values or meanings:
|
o_id
|
Object that serves as root of the iteration; same value
as the H5Ovisit object_id parameter
|
|
name
|
Name of object, relative to o_id ,
being examined at current step of the iteration
|
|
object_info
| H5O_info_t struct containing information regarding that object |
|
op_data
|
User-defined pointer to data required by the application
in processing the object;
a pass-through of the op_data pointer provided
with the H5Ovisit_by_name function call
|
The H5O_info_t struct is defined in H5Opublic.h
and described in the
H5Oget_info
function entry.
The return values from an operator are:
The H5Ovisit
op_data
parameter is a
user-defined pointer to the data required to process objects
in the course of the iteration.
This pointer is passed back to each step of the iteration in
the callback function’s op_data
parameter.
H5Lvisit
and
H5Ovisit
are companion functions:
one for examining and operating on links;
the other for examining and operating on the objects that
those links point to.
Both functions ensure that by the time the function completes
successfully, every link or object below the specified point in the
file has been presented to the application for whatever
processing the application requires.
If a C routine that takes a function pointer as an argument is called from within C++ code, the C routine should be returned from normally.
Examples of this kind of routine include callbacks such as
H5Pset_elink_cb
and H5Pset_type_conv_cb
and functions such as H5Tconvert
and
H5Ewalk2
.
Exiting the routine in its normal fashion allows the HDF5 C Library to clean up its work properly. In other words, if the C++ application jumps out of the routine back to the C++ “catch” statement, the library is not given the opportunity to close any temporary data structures that were set up when the routine was called. The C++ application should save some state as the routine is started so that any problem that occurs might be diagnosed.
hid_t object_id
|
IN: Identifier of the object at which the recursive iteration begins. |
H5_index_t index_type
|
IN: Type of index; valid values include:
H5_INDEX_NAME
H5_INDEX_CRT_ORDER
|
H5_iter_order_t order
|
IN: Order in which index is traversed;
valid values include:
H5_ITER_DEC
H5_ITER_INC
H5_ITER_NATIVE
|
H5O_iterate_t op
|
IN: Callback function passing data regarding the object to the calling application |
void *op_data
|
IN: User-defined pointer to data required by the application for its processing of the object |
On failure, returns a negative value if something goes wrong within the library, or the first negative value returned by an operator.
Release | Change |
1.8.8 | Fortran subroutine and data structure added. |
1.8.0 | C function introduced. |