H5Lvisit
(
hid_t group_id
,
H5_index_t index_type
,
H5_iter_order_t order
,
H5L_iterate_t op
,
void *op_data
)
H5Lvisit
is a recursive iteration function
to visit all links in and below a group in an HDF5 file,
thus providing a mechanism for an application to perform
a common set of operations across all of those links
or a dynamically selected subset.
For non-recursive iteration across the members of a group,
see H5Literate
.
The group serving as the root of the iteration is specified by
its group identifier, group_id
.
Two parameters are used to establish the iteration:
index_type
and order
.
index_type
specifies the index to be used.
If the links 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 H5Lpublic.h
):
(*H5L_iterate_t)(
hid_t g_id,
const char *name,
const H5L_info_t *info,
void *op_data)
The parameters of this callback function have the following values or meanings:
|
g_id
|
Group that serves as root of the iteration; same value
as the H5Lvisit group_id parameter
|
|
name
|
Name of link, relative to g_id ,
being examined at current step of the iteration
|
|
info
| H5L_info_t struct containing information regarding that link |
|
op_data
|
User-defined pointer to data required by the application
in processing the link;
a pass-through of the op_data pointer provided
with the H5Lvisit function call
|
The H5L_info_t struct is defined (in H5Lpublic.h
)
as follows:
typedef struct { H5L_type_t type; /* Type of link */ hbool_t corder_valid; /* Indicates whether creation */ /* order is valid */ int64_t corder; /* Creation order */ H5T_cset_t cset; /* Character set of link name */ union { haddr_t address; /* Address hard link points to */ size_t val_size; /* Size of soft link or */ /* user-defined link value */ } u; } H5L_info_t;
The possible return values from the callback function, and the effect of each, are as follows:
The H5Lvisit
op_data
parameter is a
user-defined pointer to the data required to process links
in the course of the iteration.
This pointer is passed back to each step of the iteration in the
op
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.
hid_t group_id
|
IN: Identifier of the group 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
|
H5L_iterate_t op
|
IN: Callback function passing data regarding the link to the calling application |
void *op_data
|
IN: User-defined pointer to data required by the application for its processing of the link |
On failure, returns a negative value if something goes wrong within the library, or the first negative value returned by an operator.
Release | C |
1.8.0 | Function introduced in this release. |