Last modified: 10 April 2013
Name: H5Ovisit
Signature:
  herr_t `H5Ovisit`( hid_t `object_id`, H5_index_t `index_type`, H5_iter_order_t `order`, H5O_iterate_t `op`, void *`op_data` )

Purpose:
  Recursively visits all objects accessible from a specified object.

Description:
  `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`): herr_t `(*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:

  - Zero causes the visit iterator to continue, returning zero when all group members have been processed.
  - A positive value causes the visit iterator to immediately return that positive value, indicating short-circuit success.
  - A negative value causes the visit iterator to immediately return that value, indicating failure.

  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.

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 `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.

Parameters:

  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

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.

Fortran2003 Interface: h5ovisit_f

History:

  Release | Change
  1.8.8 | Fortran subroutine and data structure added.
  1.8.0 | C function introduced.