Maximum length of a link's name (encoded in a 32-bit unsigned integer)

Macro to indicate operation occurs on same location

Current version of the H5L_class_t struct

Link class types.

Values less than 64 are reserved for the HDF5 library's internal use. Values 64 to 255 are for "user-defined" link class types; these types are defined by HDF5 but their behavior can be overridden by users. Users who want to create new classes of links should contact the HDF5 development team at mailto:hdfhelp@ncsa.uiuc.edu.

These values can never change because they appear in HDF5 files.

Invalid link type id

Hard link id

Soft link id

External link id

Maximum link type id

Maximum value link value for "built-in" link types

Link ids at or above this value are "user-defined" link types.

Link creation callback

typedef herr_t (*H5L_create_func_t)(const char *link_name, hid_t loc_group,
    const void *lnkdata, size_t lnkdata_size, hid_t lcpl_id);

Callback for when the link is moved

typedef herr_t (*H5L_move_func_t)(const char *new_name, hid_t new_loc,
    const void *lnkdata, size_t lnkdata_size);

Callback for when the link is copied

typedef herr_t (*H5L_copy_func_t)(const char *new_name, hid_t new_loc,
    const void *lnkdata, size_t lnkdata_size);

Callback during link traversal

typedef herr_t (*H5L_traverse_func_t)(const char *link_name, hid_t cur_group,
    const void *lnkdata, size_t lnkdata_size, hid_t lapl_id);

Callback for when the link is deleted

typedef herr_t (*H5L_delete_func_t)(const char *link_name, hid_t file,
    const void *lnkdata, size_t lnkdata_size);

Callback for querying the link

Returns the size of the buffer needed

typedef ssize_t (*H5L_query_func_t)(const char *link_name, const void *lnkdata,
    size_t lnkdata_size, void *buf /*out*/, size_t buf_size);

User-defined link types

Version number of this struct

Link type ID

Comment for debugging

Callback during link creation

Callback after moving link

Callback after copying link

Callback during link traversal

Callback for link deletion

Callback for queries

Callback for external link traversal

typedef herr_t (*H5L_elink_traverse_t)(const char *parent_file_name,
    const char *parent_group_name, const char *child_file_name,
    const char *child_object_name, unsigned *acc_flags, hid_t fapl_id,
    void *op_data);

Renames an object within an HDF5 file and moves it to a new group. The original name src is unlinked from the group graph and then inserted with the new name dst (which can specify a new path for the object) as an atomic operation. The names are interpreted relative to src_loc_id and dst_loc_id, which are either file IDs or group ID.

Returns non-negative on success, negative on failure.

herr_t H5Lmove(hid_t src_loc, const char *src_name, hid_t dst_loc,
    const char *dst_name, hid_t lcpl_id, hid_t lapl_id);

Creates a hard link from new_name to cur_name.

cur_name must name an existing object. cur_name and new_name are interpreted relative to cur_loc_id and new_loc_id, which are either file IDs or group IDs.

Returns non-negative on success, negative on failure

herr_t H5Lcreate_hard(hid_t cur_loc, const char *cur_name,
    hid_t dst_loc, const char *dst_name, hid_t lcpl_id, hid_t lapl_id);

Creates a soft link from link_name to link_target.

link_target can be anything and is interpreted at lookup time relative to the group which contains the final component of link_name. For instance, if link_target is "./foo" and link_name is ".xybar" and a request is made for ".xybar" then the actual object looked up is ".xy.foo".

Returns non-negative on success, negative on failure.

herr_t H5Lcreate_soft(const char *link_target, hid_t link_loc_id,
    const char *link_name, hid_t lcpl_id, hid_t lapl_id);

Removes the specified name from the group graph and decrements the link count for the object to which name points. If the link count reaches zero then all file-space associated with the object will be reclaimed (but if the object is open, then the reclamation of the file space is delayed until all handles to the object are closed).

Returns non-negative on success, negative on failure.

herr_t H5Ldelete(hid_t loc_id, const char *name, hid_t lapl_id);

Removes the specified link from the group graph and decrements the link count for the object to which it points, according to the order within an index.

If the link count reaches zero then all file-space associated with the object will be reclaimed (but if the object is open, then the reclamation of the file space is delayed until all handles to the object are closed).

Returns non-negative on success, negative on failure.

herr_t H5Ldelete_by_idx(hid_t loc_id, const char *group_name,
    H5_index_t idx_type, H5_iter_order_t order, hsize_t n, hid_t lapl_id);

Returns the link value of a link whose name is name. For symbolic links, this is the path to which the link points, including the null terminator. For user-defined links, it is the link buffer.

At most size bytes are copied to the buf result buffer.

Returns non-negative on success, negative on failure.

herr_t H5Lget_val(hid_t loc_id, const char *name, void *buf/*out*/,
    size_t size, hid_t lapl_id);

Returns the link value of a link, according to the order of an index. For symbolic links, this is the path to which the link points, including the null terminator. For user-defined links, it is the link buffer.

At most size bytes are copied to the buf result buffer.

Returns non-negative on success, negative on failure.

herr_t H5Lget_val_by_idx(hid_t loc_id, const char *group_name,
    H5_index_t idx_type, H5_iter_order_t order, hsize_t n,
    void *buf/*out*/, size_t size, hid_t lapl_id);

Checks if a link of a given name exists in a group

htri_t H5Lexists(hid_t loc_id, const char *name, hid_t lapl_id);

Gets name for a link, according to the order within an index.

Same pattern of behavior as h5i_get_name.

On success, returns non-negative length of name, with information in name buffer On failure,returns a negative value.

ssize_t H5Lget_name_by_idx(hid_t loc_id, const char *group_name,
    H5_index_t idx_type, H5_iter_order_t order, hsize_t n,
    char *name /*out*/, size_t size, hid_t lapl_id);

Creates a user-defined link of type link_type named link_name with user-specified data udata.

The format of the information pointed to by udata is defined by the user. udata_size holds the size of this buffer.

link_name is interpreted relative to link_loc_id.

The property list specified by lcpl_id holds properties used to create the link.

The link class of the new link must already be registered with the library.

Returns non-negative on success, negative on failure.

herr_t H5Lcreate_ud(hid_t link_loc_id, const char *link_name,
    H5L_type_t link_type, const void *udata, size_t udata_size, hid_t lcpl_id,
    hid_t lapl_id);

Registers a class of user-defined links, or changes the behavior of an existing class.

The link class passed in will override any existing link class for the specified link class ID. It must at least include a H5L_class_t version (which should be h5l_LINK_CLASS_T_VERS), a link class ID, and a traversal function.

Returns non-negative on success, negative on failure.

herr_t H5Lregister(const H5L_class_t *cls);

Unregisters a class of user-defined links, preventing them from being traversed, queried, moved, etc.

A link class can be re-registered using h5l_register.

Returns non-negative on success, negative on failure.

herr_t H5Lunregister(H5L_type_t id);

Tests whether a user-defined link class has been registered or not.

htri_t H5Lis_registered(H5L_type_t id);

Given a buffer holding the "link value" from an external link, gets pointers to the information within the link value buffer.

External link link values contain some flags and two NULL-terminated strings, one after the other.

The flags value will be filled in and filename and obj_path will be set to pointers within ext_linkval (unless any of these values is NULL).

Using this function on strings that aren't external link udata buffers can result in segmentation faults.

Returns non-negative on success, negative on failure.

herr_t H5Lunpack_elink_val(const void *ext_linkval/*in*/, size_t link_size,
   unsigned *flags, const char **filename/*out*/, const char **obj_path /*out*/);

Creates an external link from link_name to obj_name.

External links are links to objects in other HDF5 files. They are allowed to "dangle" like soft links internal to a file. file_name is the name of the file that obj_name is is contained within. If obj_name is given as a relative path name, the path will be relative to the root group of file_name. link_name is interpreted relative to link_loc_id, which is either a file ID or a group ID.

Returns non-negative on success, negative on failure.

herr_t H5Lcreate_external(const char *file_name, const char *obj_name,
    hid_t link_loc_id, const char *link_name, hid_t lcpl_id, hid_t lapl_id);