Iterator

Iterator — Iterate a sequence of objects across some other object.

Synopsis




typedef     librdf_iterator;
void*       (*librdf_iterator_map_handler)  (librdf_iterator *iterator,
                                             void *map_context,
                                             void *item);
void        (*librdf_iterator_map_free_context_handler)
                                            (void *map_context);
librdf_iterator* librdf_new_iterator        (librdf_world *world,
                                             void *context,
                                             int (*is_end_method) (void*),
                                             int (*next_method) (void*),
                                             void* (*get_method) (void*, int),
                                             void (*finished_method) (void*));
void        librdf_free_iterator            (librdf_iterator *iterator);
int         librdf_iterator_end             (librdf_iterator *iterator);
int         librdf_iterator_have_elements   (librdf_iterator *iterator);
int         librdf_iterator_next            (librdf_iterator *iterator);
void*       librdf_iterator_get_object      (librdf_iterator *iterator);
void*       librdf_iterator_get_context     (librdf_iterator *iterator);
void*       librdf_iterator_get_key         (librdf_iterator *iterator);
void*       librdf_iterator_get_value       (librdf_iterator *iterator);
int         librdf_iterator_add_map         (librdf_iterator *iterator,
                                             librdf_iterator_map_handler map_function,
                                             librdf_iterator_map_free_context_handler free_context,
                                             void *map_context);
librdf_iterator* librdf_new_empty_iterator  (librdf_world *world);

Description

Provides a way to operate across a sequence of objects that are generated one-by-one on demand. The returned objects can be of any type but the main public methods are on the librdf_model classs and return sequence of librdf_node objects such as librdf_model_get_sources().

Details

librdf_iterator

typedef struct librdf_iterator_s librdf_iterator;

Redland iterator class.


librdf_iterator_map_handler ()

void*       (*librdf_iterator_map_handler)  (librdf_iterator *iterator,
                                             void *map_context,
                                             void *item);

Map function for a librdf_iterator map operation.

See librdf_iterator_add_map().

iterator : Iterator that this map is operating over.
map_context : Map data context pointer.
item : Pointer to the current item in the iteration.
Returns : ; item in keep the iteration or NULL to remove it

librdf_iterator_map_free_context_handler ()

void        (*librdf_iterator_map_free_context_handler)
                                            (void *map_context);

Free handler function for a librdf_iterator map operation.

See librdf_iterator_add_map().

map_context : Map data context pointer.

librdf_new_iterator ()

librdf_iterator* librdf_new_iterator        (librdf_world *world,
                                             void *context,
                                             int (*is_end_method) (void*),
                                             int (*next_method) (void*),
                                             void* (*get_method) (void*, int),
                                             void (*finished_method) (void*));

Constructor - create a new librdf_iterator object.

world : redland world object
context : context to pass to the iterator functions
is_end_method : function to call to see if the iteration has ended
next_method : function to get the next element
get_method : function to get the next element
finished_method : function to destroy the iterator context (or NULL if not needed)
Returns : a new librdf_iterator object or NULL on failure

librdf_free_iterator ()

void        librdf_free_iterator            (librdf_iterator *iterator);

Destructor - destroy a librdf_iterator object.

iterator : the librdf_iterator object

librdf_iterator_end ()

int         librdf_iterator_end             (librdf_iterator *iterator);

Test if the iterator has finished.

iterator : the librdf_iterator object
Returns : non 0 if the iterator has finished

librdf_iterator_have_elements ()

int         librdf_iterator_have_elements   (librdf_iterator *iterator);

Test if the iterator has finished.

DEPRECATED - use !librdf_iterator_end(iterator)

iterator : the librdf_iterator object
Returns : 0 if the iterator has finished

librdf_iterator_next ()

int         librdf_iterator_next            (librdf_iterator *iterator);

Move to the next iterator element.

iterator : the librdf_iterator object
Returns : non 0 if the iterator has finished

librdf_iterator_get_object ()

void*       librdf_iterator_get_object      (librdf_iterator *iterator);

Get the current object from the iterator.

This method returns a SHARED pointer to the current iterator object which should be copied by the caller to preserve it if the iterator is moved on librdf_iterator_next or if it should last after the iterator is closed.

iterator : the librdf_iterator object
Returns : The next element or NULL if the iterator has finished.

librdf_iterator_get_context ()

void*       librdf_iterator_get_context     (librdf_iterator *iterator);

Get the context of the current object on the iterator.

This method returns a SHARED pointer to the current context node object which should be copied by the caller to preserve it if the iterator is moved on librdf_iterator_next or if it should last after the iterator is closed.

iterator : the librdf_iterator object
Returns : The context or NULL if the iterator has finished.

librdf_iterator_get_key ()

void*       librdf_iterator_get_key         (librdf_iterator *iterator);

Get the key of the current object on the iterator.

iterator : the librdf_iterator object
Returns : The context or NULL if the iterator has finished.

librdf_iterator_get_value ()

void*       librdf_iterator_get_value       (librdf_iterator *iterator);

Get the value of the current object on the iterator.

iterator : the librdf_iterator object
Returns : The context or NULL if the iterator has finished.

librdf_iterator_add_map ()

int         librdf_iterator_add_map         (librdf_iterator *iterator,
                                             librdf_iterator_map_handler map_function,
                                             librdf_iterator_map_free_context_handler free_context,
                                             void *map_context);

Add a librdf_iterator mapping function.

Adds an iterator mapping function which operates over the iterator to select which elements are returned; it will be applied as soon as this method is called.

Several mapping functions can be added and they are applied in the order given

The mapping function should return non 0 to allow the element to be returned.

iterator : the iterator
map_function : the function to operate
free_context : the function to use to free the context (or NULL)
map_context : the context to pass to the map function
Returns : Non 0 on failure

librdf_new_empty_iterator ()

librdf_iterator* librdf_new_empty_iterator  (librdf_world *world);

Constructor - create a new librdf_iterator with no content.

world : redland world object
Returns : a new librdf_iterator object or NULL on failure