H5O.visit

Visit objects specified by object identifier

Syntax

[status,opdata_out] = H5O.visit(obj_id,index_type,order,iter_func,opdata_in)

Description

[status,opdata_out] = H5O.visit(obj_id,index_type,order,iter_func,opdata_in) 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. This provides a mechanism for an application to perform a common set of operations across all of those objects or a dynamically selected subset.

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 data type, there is no iteration.

Two parameters are used to establish the iteration: index_type and order. The index_type parameter specifies the index used. If the links in a group have not been indexed by the index type, they are first sorted by that index, and then the iteration will begin. If the links have been so indexed, the sorting step is unnecessary, so the iteration can 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 callback function iter_func must have the following signature:

function [status,opdata_out] = iter_func(group_id,name,opdata_in)

opdata_in is a user-defined value or structure and is passed to the first step of the iteration in the iter_func opdata_in parameter. The opdata_out of an iteration step forms the opdata_in for the next iteration step. The final opdata_out at the end of the iteration is then returned to the caller as opdata_out.

status value returned by iter_func is interpreted as follows.

zeroContinues with the iteration or returns zero status value to the caller if all members have been processed
positiveStops the iteration and returns the positive status value to the caller
negativeStops the iteration and throws an error indicating failure

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