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H5O_VISIT_BY_NAME2

Recursively visits all objects starting from a specified object

Procedure:

H5O_VISIT_BY_NAME2(loc_id, object_name, index_type, order, op, op_data, fields, lapl_id)

Signature:

herr_t H5Ovisit_by_name2( hid_t loc_id, const char *object_name, H5_index_t index_type, H5_iter_order_t order,H5O_iterate_t op, void *op_data, unsigned int 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)
    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

Parameters:
hid_t loc_idIN: Location identifier; may be a file, group, dataset, named datatype or attribute identifier
const char *object_nameIN: Name of the object, generally relative to loc_id, that will serve as root of the iteration
H5_index_t index_typeIN: 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 opIN: Callback function passing data regarding the object to the calling application
void *op_dataIN: User-defined pointer to data required by the application for its processing of the object
unsigned int fieldsIN: Flags specifying the fields to be retrieved to the callback function op.
hid_t lapl_idIN: Link access property list identifier

Description:

H5O_VISIT_BY_NAME2 is a recursive iteration function to visit the object specified by the loc_id / object_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 / object_name parameter pair. loc_id specifies a file or an object in a file; object_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, object_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_VISIT instead of H5O_VISIT_BY_NAME.)

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_NAMEAlpha-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_INCIncreasing order
H5_ITER_DECDecreasing 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_VISIT.

The H5O_info_t struct is defined in H5Opublic.h and described in the H5O_GET_INFO 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:

FlagPurpose
H5O_INFO_BASICFill in the fileno, addr, type, and rc fields
H5O_INFO_TIMEFill in the atime, mtime, ctime, and btime fields
H5O_INFO_NUM_ATTRSFill in the num_attrs field
H5O_INFO_HDRFill in the hdr field
H5O_INFO_META_SIZEFill in the meta_size field
H5O_INFO_ALLH5O_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:

Coming Soon!

History:
Release    Change
1.10.3C function introduced in this release.
1.8.11Fortran subroutine introduced in this release.
1.8.0Function introduced in this release.

--- Last Modified: August 16, 2018 | 12:49 PM