- Created by Barbara Jones, last modified on Feb 19, 2020
H5O_VISIT_BY_NAME2
Recursively visits all objects starting from a specified object
As of HDF5-1.12 this function has been deprecated in favor of the function H5O_VISIT_BY_NAME3 or the macro H5O_VISIT_BY_NAME.
Procedure:
H5O_VISIT_BY_NAME2 ( loc_id, obj_name, idx_type, order, op, op_data, fields, lapl_id )
Signature:
herr_t H5Ovisit_by_name2 ( hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order, H5O_iterate1_t op, void *op_data,
unsigned fields, hid_t lapl_id )
SUBROUTINE h5ovisit_by_name_f(loc_id, object_name, index_type, order, &
op, op_data, return_value, hdferr, lapl_id, fields)
USE, INTRINSIC :: ISO_C_BINDING
IMPLICIT NONE
INTEGER(HID_T) , INTENT(IN) :: loc_id
CHARACTER(LEN=*), INTENT(IN) :: object_name
INTEGER , INTENT(IN) :: index_type
INTEGER , INTENT(IN) :: order
TYPE(C_FUNPTR) :: op
TYPE(C_PTR) :: op_data
INTEGER , INTENT(OUT) :: return_value
INTEGER , INTENT(OUT) :: hdferr
INTEGER(HID_T) , INTENT(IN) , OPTIONAL :: lapl_id
INTEGER , INTENT(IN) , OPTIONAL :: fields
Parameters:
hid_t loc_id | IN: Location identifier; may be a file, group, dataset, named datatype or attribute identifier |
const char *obj_name | IN: Name of the object, generally relative to loc_id, that will serve as root of the iteration |
H5_index_t idx_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_iterate1_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 |
unsigned int fields | IN: Flags specifying the fields to be retrieved to the callback function op. |
hid_t lapl_id | IN: Link access property list identifier |
Description:
H5O_VISIT_BY_NAME2 is a recursive iteration function to visit the object specified by the loc_id / obj_name parameter pair and, if that object 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 H5L_ITERATE.
The object serving as the root of the iteration is specified by the loc_id / obj_name parameter pair. loc_id specifies a file or an object in a file; obj_name specifies either an object in the file (with an absolute name based in the file’s root group) or an object name relative to loc_id. If loc_id fully specifies the object that is to serve as the root of the iteration, obj_name should be '.' (a dot). (Note that when loc_id fully specifies the the object that is to serve as the root of the iteration, the user may wish to consider using H5O_VISIT2 instead of H5O_VISIT_BY_NAME.)
Two parameters are used to establish the iteration: idx_type and order.
idx_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 unnecessary, 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 idx_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 idx_type. Valid values include the following:
H5_ITER_INC | Increasing order |
H5_ITER_DEC | Decreasing order |
H5_ITER_NATIVE | Fastest available order |
The op callback function and the effect of the callback function’s return value on the application are described in H5O_VISIT2.
The H5O_info1_t struct is defined in H5Opublic.h and described in the H5O_GET_INFO1 function entry.
The H5O_VISIT_BY_NAME2 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.
lapl_id is a link access property list. In the general case, when default link access properties are acceptable, this can be passed in as H5P_DEFAULT. An example of a situation that requires a non-default link access property list is when the link is an external link; an external link may require that a link prefix be set in a link access property list (see H5P_SET_ELINK_PREFIX).
The fields parameter contains flags to determine which fields will be retrieved by the op callback function. These flags are defined in the H5Opublic.h file:
| Flag | Purpose |
|---|---|
| H5O_INFO_BASIC | Fill in the fileno, addr, type, and rc fields |
| H5O_INFO_TIME | Fill in the atime, mtime, ctime, and btime fields |
| H5O_INFO_NUM_ATTRS | Fill in the num_attrs field |
| H5O_INFO_HDR | Fill in the hdr field |
| H5O_INFO_META_SIZE | Fill in the meta_size field |
| H5O_INFO_ALL | H5O_INFO_BASIC | H5O_INFO_TIME | H5O_INFO_NUM_ATTRS | H5O_INFO_HDR | H5O_INFO_META_SIZE |
H5L_VISIT_BY_NAME and H5O_VISIT_BY_NAME 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.
Programming Note for C++ Developers Using C Functions:
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 H5P_SET_ELINK_CB and H5P_SET_TYPE_CONV_CB and functions such as H5T_CONVERT and H5E_WALK2.
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.
Returns:
On success, returns the return value of the first operator that returns a positive value, or zero if all members were processed with no operator returning non-zero.
On failure, returns a negative value if something goes wrong within the library, or the first negative value returned by an operator.
Example:
History:
| Release | Change |
|---|---|
| 1.10.3 | C function introduced in this release. |
--- Last Modified: February 19, 2020 | 03:23 PM