Iterator

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

Synopsis

typedef             librdf_iterator;
enum                librdf_iterator_get_method_flags;
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.

enum librdf_iterator_get_method_flags

typedef enum {
  LIBRDF_ITERATOR_GET_METHOD_GET_OBJECT  = 0,
  LIBRDF_ITERATOR_GET_METHOD_GET_CONTEXT = 1,
  LIBRDF_ITERATOR_GET_METHOD_GET_KEY     = 2,
  LIBRDF_ITERATOR_GET_METHOD_GET_VALUE   = 3
} librdf_iterator_get_method_flags;

Flags for librdf_new_iterator() get_method function pointer.

LIBRDF_ITERATOR_GET_METHOD_GET_OBJECT

 get object from iterator - implementing librdf_iterator_get_context()

LIBRDF_ITERATOR_GET_METHOD_GET_CONTEXT

 get context from iterator - implementing librdf_iterator_get_object()

LIBRDF_ITERATOR_GET_METHOD_GET_KEY

 get iterator key object from iterator - implementing librdf_iterator_get_key()

LIBRDF_ITERATOR_GET_METHOD_GET_VALUE

 get iterator value from iterator - implementing librdf_iterator_get_value()

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. The iterator object takes ownership of context and frees it with finished_method. The finished method is not called if librdf_new_iterator fails and returns NULL.

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 (can be NULL) 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
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