2 This file is part of GNUnet.
3 (C) 2012, 2013 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 3, or (at your
8 option) any later version.
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11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.
23 * @brief api for the set service
24 * @author Florian Dold
27 #include "gnunet_util_lib.h"
28 #include "gnunet_protocols.h"
29 #include "gnunet_client_lib.h"
30 #include "gnunet_set_service.h"
34 #define LOG(kind,...) GNUNET_log_from (kind, "set-api",__VA_ARGS__)
37 * Opaque handle to a set.
39 struct GNUNET_SET_Handle
42 * Client connected to the set service.
44 struct GNUNET_CLIENT_Connection *client;
47 * Message queue for 'client'.
49 struct GNUNET_MQ_Handle *mq;
52 * Linked list of operations on the set.
54 struct GNUNET_SET_OperationHandle *ops_head;
57 * Linked list of operations on the set.
59 struct GNUNET_SET_OperationHandle *ops_tail;
62 * Should the set be destroyed once all operations are gone?
64 int destroy_requested;
67 * Has the set become invalid (e.g. service died)?
72 * Callback for the current iteration over the set,
73 * NULL if no iterator is active.
75 GNUNET_SET_ElementIterator iterator;
78 * Closure for 'iterator'
85 * Opaque handle to a set operation request from another peer.
87 struct GNUNET_SET_Request
90 * Id of the request, used to identify the request when
91 * accepting/rejecting it.
96 * Has the request been accepted already?
97 * GNUNET_YES/GNUNET_NO
104 * Handle to an operation.
105 * Only known to the service after commiting
106 * the handle with a set.
108 struct GNUNET_SET_OperationHandle
111 * Function to be called when we have a result,
114 GNUNET_SET_ResultIterator result_cb;
117 * Closure for result_cb.
122 * Local set used for the operation,
123 * NULL if no set has been provided by conclude yet.
125 struct GNUNET_SET_Handle *set;
128 * Request ID to identify the operation within the set.
133 * Message sent to the server on calling conclude,
134 * NULL if conclude has been called.
136 struct GNUNET_MQ_Envelope *conclude_mqm;
139 * Address of the request if in the conclude message,
140 * used to patch the request id into the message when the set is known.
142 uint32_t *request_id_addr;
145 * Handles are kept in a linked list.
147 struct GNUNET_SET_OperationHandle *prev;
150 * Handles are kept in a linked list.
152 struct GNUNET_SET_OperationHandle *next;
157 * Opaque handle to a listen operation.
159 struct GNUNET_SET_ListenHandle
162 * Connection to the service.
164 struct GNUNET_CLIENT_Connection *client;
167 * Message queue for the client.
169 struct GNUNET_MQ_Handle* mq;
172 * Configuration handle for the listener, stored
173 * here to be able to reconnect transparently on
174 * connection failure.
176 const struct GNUNET_CONFIGURATION_Handle *cfg;
179 * Function to call on a new incoming request,
182 GNUNET_SET_ListenCallback listen_cb;
185 * Closure for listen_cb.
190 * Operation we listen for.
192 enum GNUNET_SET_OperationType operation;
195 * Application ID we listen for.
197 struct GNUNET_HashCode app_id;
200 * Time to wait until we try to reconnect on failure.
202 struct GNUNET_TIME_Relative reconnect_backoff;
205 * Task for reconnecting when the listener fails.
207 GNUNET_SCHEDULER_TaskIdentifier reconnect_task;
211 /* forward declaration */
213 listen_connect (void *cls,
214 const struct GNUNET_SCHEDULER_TaskContext *tc);
218 * Handle element for iteration over the set.
221 * @param mh the message
224 handle_iter_element (void *cls, const struct GNUNET_MessageHeader *mh)
226 struct GNUNET_SET_Handle *set = cls;
227 struct GNUNET_SET_Element element;
228 const struct GNUNET_SET_IterResponseMessage *msg =
229 (const struct GNUNET_SET_IterResponseMessage *) mh;
230 struct GNUNET_SET_IterAckMessage *ack_msg;
231 struct GNUNET_MQ_Envelope *ev;
233 if (NULL == set->iterator)
236 element.size = ntohs (mh->size) - sizeof (struct GNUNET_SET_IterResponseMessage);
237 element.element_type = htons (msg->element_type);
238 element.data = &msg[1];
239 set->iterator (set->iterator_cls, &element);
240 ev = GNUNET_MQ_msg (ack_msg, GNUNET_MESSAGE_TYPE_SET_ITER_ACK);
241 ack_msg->send_more = htonl (1);
242 GNUNET_MQ_send (set->mq, ev);
247 * Handle element for iteration over the set.
250 * @param mh the message
253 handle_iter_done (void *cls, const struct GNUNET_MessageHeader *mh)
255 struct GNUNET_SET_Handle *set = cls;
257 if (NULL == set->iterator)
260 set->iterator (set->iterator_cls, NULL);
265 * Handle result message for a set operation.
268 * @param mh the message
271 handle_result (void *cls, const struct GNUNET_MessageHeader *mh)
273 const struct GNUNET_SET_ResultMessage *msg;
274 struct GNUNET_SET_Handle *set = cls;
275 struct GNUNET_SET_OperationHandle *oh;
276 struct GNUNET_SET_Element e;
277 enum GNUNET_SET_Status result_status;
279 msg = (const struct GNUNET_SET_ResultMessage *) mh;
280 GNUNET_assert (NULL != set);
281 GNUNET_assert (NULL != set->mq);
283 result_status = ntohs (msg->result_status);
285 oh = GNUNET_MQ_assoc_get (set->mq, ntohl (msg->request_id));
286 // 'oh' can be NULL if we canceled the operation, but the service
287 // did not get the cancel message yet.
290 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "ignoring result from canceled operation\n");
293 /* status is not STATUS_OK => there's no attached element,
294 * and this is the last result message we get */
295 if (GNUNET_SET_STATUS_OK != result_status)
297 GNUNET_MQ_assoc_remove (set->mq, ntohl (msg->request_id));
298 GNUNET_CONTAINER_DLL_remove (oh->set->ops_head, oh->set->ops_tail, oh);
299 if (GNUNET_YES == oh->set->destroy_requested)
300 GNUNET_SET_destroy (oh->set);
301 if (NULL != oh->result_cb)
302 oh->result_cb (oh->result_cls, NULL, result_status);
308 e.size = ntohs (mh->size) - sizeof (struct GNUNET_SET_ResultMessage);
309 e.element_type = msg->element_type;
310 if (NULL != oh->result_cb)
311 oh->result_cb (oh->result_cls, &e, result_status);
316 * Handle request message for a listen operation
318 * @param cls the listen handle
319 * @param mh the message
322 handle_request (void *cls,
323 const struct GNUNET_MessageHeader *mh)
325 const struct GNUNET_SET_RequestMessage *msg = (const struct GNUNET_SET_RequestMessage *) mh;
326 struct GNUNET_SET_ListenHandle *lh = cls;
327 struct GNUNET_SET_Request *req;
328 const struct GNUNET_MessageHeader *context_msg;
330 LOG (GNUNET_ERROR_TYPE_DEBUG,
331 "processing operation request\n");
332 req = GNUNET_new (struct GNUNET_SET_Request);
333 req->accept_id = ntohl (msg->accept_id);
334 context_msg = GNUNET_MQ_extract_nested_mh (msg);
335 /* calling #GNUNET_SET_accept() in the listen cb will set req->accepted */
336 lh->listen_cb (lh->listen_cls, &msg->peer_id, context_msg, req);
338 /* we got another request => reset the backoff */
339 lh->reconnect_backoff = GNUNET_TIME_UNIT_MILLISECONDS;
341 if (GNUNET_NO == req->accepted)
343 struct GNUNET_MQ_Envelope *mqm;
344 struct GNUNET_SET_RejectMessage *rmsg;
346 mqm = GNUNET_MQ_msg (rmsg,
347 GNUNET_MESSAGE_TYPE_SET_REJECT);
348 rmsg->accept_reject_id = msg->accept_id;
349 GNUNET_MQ_send (lh->mq, mqm);
350 LOG (GNUNET_ERROR_TYPE_DEBUG,
351 "rejecting request\n");
355 LOG (GNUNET_ERROR_TYPE_DEBUG,
356 "processed op request from service\n");
358 /* the accept-case is handled in GNUNET_SET_accept,
359 * as we have the accept message available there */
364 handle_client_listener_error (void *cls,
365 enum GNUNET_MQ_Error error)
367 struct GNUNET_SET_ListenHandle *lh = cls;
369 LOG (GNUNET_ERROR_TYPE_DEBUG,
370 "listener broke down, re-connecting\n");
371 GNUNET_CLIENT_disconnect (lh->client);
373 GNUNET_MQ_destroy (lh->mq);
375 lh->reconnect_task = GNUNET_SCHEDULER_add_delayed (lh->reconnect_backoff,
376 &listen_connect, lh);
377 lh->reconnect_backoff = GNUNET_TIME_STD_BACKOFF (lh->reconnect_backoff);
382 * Destroy the set handle if no operations are left, mark the set
383 * for destruction otherwise.
385 * @param set set handle to destroy
388 set_destroy (struct GNUNET_SET_Handle *set)
390 if (NULL != set->ops_head)
392 set->destroy_requested = GNUNET_YES;
395 LOG (GNUNET_ERROR_TYPE_DEBUG, "Really destroying set\n");
396 GNUNET_CLIENT_disconnect (set->client);
398 GNUNET_MQ_destroy (set->mq);
406 * Cancel the given set operation. We need to send an explicit cancel message,
407 * as all operations one one set communicate using one handle.
409 * In contrast to #GNUNET_SET_operation_cancel(), this function indicates whether
410 * the set of the operation has been destroyed because all operations are done and
411 * the set's destruction was requested before.
413 * @param oh set operation to cancel
414 * @return #GNUNET_YES if the set of the operation was destroyed
417 set_operation_cancel (struct GNUNET_SET_OperationHandle *oh)
421 if (NULL != oh->conclude_mqm)
422 GNUNET_MQ_discard (oh->conclude_mqm);
424 /* is the operation already commited? */
427 struct GNUNET_SET_OperationHandle *h_assoc;
428 struct GNUNET_SET_CancelMessage *m;
429 struct GNUNET_MQ_Envelope *mqm;
431 GNUNET_CONTAINER_DLL_remove (oh->set->ops_head,
434 h_assoc = GNUNET_MQ_assoc_remove (oh->set->mq,
436 GNUNET_assert ((h_assoc == NULL) || (h_assoc == oh));
437 mqm = GNUNET_MQ_msg (m, GNUNET_MESSAGE_TYPE_SET_CANCEL);
438 m->request_id = htonl (oh->request_id);
439 GNUNET_MQ_send (oh->set->mq, mqm);
441 if (GNUNET_YES == oh->set->destroy_requested)
443 LOG (GNUNET_ERROR_TYPE_DEBUG,
444 "Destroying set after operation cancel\n");
445 ret = set_destroy (oh->set);
454 * Cancel the given set operation. We need to send an explicit cancel
455 * message, as all operations one one set communicate using one
458 * @param oh set operation to cancel
461 GNUNET_SET_operation_cancel (struct GNUNET_SET_OperationHandle *oh)
463 (void) set_operation_cancel (oh);
468 handle_client_set_error (void *cls, enum GNUNET_MQ_Error error)
470 struct GNUNET_SET_Handle *set = cls;
472 LOG (GNUNET_ERROR_TYPE_DEBUG,
473 "handling client set error\n");
475 while (NULL != set->ops_head)
477 if (NULL != set->ops_head->result_cb)
478 set->ops_head->result_cb (set->ops_head->result_cls, NULL,
479 GNUNET_SET_STATUS_FAILURE);
480 if (GNUNET_YES == set_operation_cancel (set->ops_head))
481 return; /* stop if the set is destroyed */
483 set->invalid = GNUNET_YES;
488 * Create an empty set, supporting the specified operation.
490 * @param cfg configuration to use for connecting to the
492 * @param op operation supported by the set
493 * Note that the operation has to be specified
494 * beforehand, as certain set operations need to maintain
495 * data structures spefific to the operation
496 * @return a handle to the set
498 struct GNUNET_SET_Handle *
499 GNUNET_SET_create (const struct GNUNET_CONFIGURATION_Handle *cfg,
500 enum GNUNET_SET_OperationType op)
502 static const struct GNUNET_MQ_MessageHandler mq_handlers[] = {
503 {handle_result, GNUNET_MESSAGE_TYPE_SET_RESULT, 0},
504 {handle_iter_element, GNUNET_MESSAGE_TYPE_SET_ITER_ELEMENT, 0},
505 {handle_iter_done, GNUNET_MESSAGE_TYPE_SET_ITER_DONE, 0},
506 GNUNET_MQ_HANDLERS_END
508 struct GNUNET_SET_Handle *set;
509 struct GNUNET_MQ_Envelope *mqm;
510 struct GNUNET_SET_CreateMessage *msg;
512 set = GNUNET_new (struct GNUNET_SET_Handle);
513 set->client = GNUNET_CLIENT_connect ("set", cfg);
514 LOG (GNUNET_ERROR_TYPE_DEBUG, "set client created\n");
515 GNUNET_assert (NULL != set->client);
516 set->mq = GNUNET_MQ_queue_for_connection_client (set->client, mq_handlers,
517 handle_client_set_error, set);
518 GNUNET_assert (NULL != set->mq);
519 mqm = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SET_CREATE);
520 msg->operation = htonl (op);
521 GNUNET_MQ_send (set->mq, mqm);
527 * Add an element to the given set.
528 * After the element has been added (in the sense of being
529 * transmitted to the set service), cont will be called.
530 * Calls to add_element can be queued
532 * @param set set to add element to
533 * @param element element to add to the set
534 * @param cont continuation called after the element has been added
535 * @param cont_cls closure for @a cont
536 * @return #GNUNET_OK on success, #GNUNET_SYSERR if the
537 * set is invalid (e.g. the set service crashed)
540 GNUNET_SET_add_element (struct GNUNET_SET_Handle *set,
541 const struct GNUNET_SET_Element *element,
542 GNUNET_SET_Continuation cont,
545 struct GNUNET_MQ_Envelope *mqm;
546 struct GNUNET_SET_ElementMessage *msg;
548 if (GNUNET_YES == set->invalid)
552 return GNUNET_SYSERR;
555 mqm = GNUNET_MQ_msg_extra (msg, element->size, GNUNET_MESSAGE_TYPE_SET_ADD);
556 msg->element_type = element->element_type;
557 memcpy (&msg[1], element->data, element->size);
558 GNUNET_MQ_notify_sent (mqm, cont, cont_cls);
559 GNUNET_MQ_send (set->mq, mqm);
565 * Remove an element to the given set.
566 * After the element has been removed (in the sense of the
567 * request being transmitted to the set service), cont will be called.
568 * Calls to remove_element can be queued
570 * @param set set to remove element from
571 * @param element element to remove from the set
572 * @param cont continuation called after the element has been removed
573 * @param cont_cls closure for @a cont
574 * @return #GNUNET_OK on success, #GNUNET_SYSERR if the
575 * set is invalid (e.g. the set service crashed)
578 GNUNET_SET_remove_element (struct GNUNET_SET_Handle *set,
579 const struct GNUNET_SET_Element *element,
580 GNUNET_SET_Continuation cont,
583 struct GNUNET_MQ_Envelope *mqm;
584 struct GNUNET_SET_ElementMessage *msg;
586 if (GNUNET_YES == set->invalid)
590 return GNUNET_SYSERR;
593 mqm = GNUNET_MQ_msg_extra (msg,
595 GNUNET_MESSAGE_TYPE_SET_REMOVE);
596 msg->element_type = element->element_type;
597 memcpy (&msg[1], element->data, element->size);
598 GNUNET_MQ_notify_sent (mqm, cont, cont_cls);
599 GNUNET_MQ_send (set->mq, mqm);
605 * Destroy the set handle, and free all associated resources.
607 * @param set set handle to destroy
610 GNUNET_SET_destroy (struct GNUNET_SET_Handle *set)
612 (void) set_destroy (set);
617 * Prepare a set operation to be evaluated with another peer.
618 * The evaluation will not start until the client provides
619 * a local set with #GNUNET_SET_commit().
621 * @param other_peer peer with the other set
622 * @param app_id hash for the application using the set
623 * @param context_msg additional information for the request
624 * @param result_mode specified how results will be returned,
625 * see `enum GNUNET_SET_ResultMode`.
626 * @param result_cb called on error or success
627 * @param result_cls closure for @e result_cb
628 * @return a handle to cancel the operation
630 struct GNUNET_SET_OperationHandle *
631 GNUNET_SET_prepare (const struct GNUNET_PeerIdentity *other_peer,
632 const struct GNUNET_HashCode *app_id,
633 const struct GNUNET_MessageHeader *context_msg,
634 enum GNUNET_SET_ResultMode result_mode,
635 GNUNET_SET_ResultIterator result_cb,
638 struct GNUNET_MQ_Envelope *mqm;
639 struct GNUNET_SET_OperationHandle *oh;
640 struct GNUNET_SET_EvaluateMessage *msg;
642 oh = GNUNET_new (struct GNUNET_SET_OperationHandle);
643 oh->result_cb = result_cb;
644 oh->result_cls = result_cls;
645 mqm = GNUNET_MQ_msg_nested_mh (msg,
646 GNUNET_MESSAGE_TYPE_SET_EVALUATE,
648 msg->app_id = *app_id;
649 msg->result_mode = htonl (result_mode);
650 msg->target_peer = *other_peer;
651 oh->conclude_mqm = mqm;
652 oh->request_id_addr = &msg->request_id;
659 * Connect to the set service in order to listen
662 * @param cls the listen handle to connect
663 * @param tc task context if invoked as a task, NULL otherwise
666 listen_connect (void *cls,
667 const struct GNUNET_SCHEDULER_TaskContext *tc)
669 struct GNUNET_MQ_Envelope *mqm;
670 struct GNUNET_SET_ListenMessage *msg;
671 struct GNUNET_SET_ListenHandle *lh = cls;
672 static const struct GNUNET_MQ_MessageHandler mq_handlers[] = {
673 {handle_request, GNUNET_MESSAGE_TYPE_SET_REQUEST},
674 GNUNET_MQ_HANDLERS_END
677 if ((tc != NULL) &&(tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN) != 0)
679 LOG (GNUNET_ERROR_TYPE_DEBUG, "listener not reconnecting due to shutdown\n");
683 lh->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
685 GNUNET_assert (NULL == lh->client);
686 lh->client = GNUNET_CLIENT_connect ("set", lh->cfg);
687 if (NULL == lh->client)
689 LOG (GNUNET_ERROR_TYPE_ERROR,
690 "could not connect to set (wrong configuration?), giving up listening\n");
693 GNUNET_assert (NULL == lh->mq);
694 lh->mq = GNUNET_MQ_queue_for_connection_client (lh->client, mq_handlers,
695 handle_client_listener_error, lh);
696 mqm = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SET_LISTEN);
697 msg->operation = htonl (lh->operation);
698 msg->app_id = lh->app_id;
699 GNUNET_MQ_send (lh->mq, mqm);
704 * Wait for set operation requests for the given application id
706 * @param cfg configuration to use for connecting to
707 * the set service, needs to be valid for the lifetime of the listen handle
708 * @param operation operation we want to listen for
709 * @param app_id id of the application that handles set operation requests
710 * @param listen_cb called for each incoming request matching the operation
712 * @param listen_cls handle for listen_cb
713 * @return a handle that can be used to cancel the listen operation
715 struct GNUNET_SET_ListenHandle *
716 GNUNET_SET_listen (const struct GNUNET_CONFIGURATION_Handle *cfg,
717 enum GNUNET_SET_OperationType operation,
718 const struct GNUNET_HashCode *app_id,
719 GNUNET_SET_ListenCallback listen_cb,
722 struct GNUNET_SET_ListenHandle *lh;
724 lh = GNUNET_new (struct GNUNET_SET_ListenHandle);
725 lh->listen_cb = listen_cb;
726 lh->listen_cls = listen_cls;
728 lh->operation = operation;
729 lh->app_id = *app_id;
730 lh->reconnect_backoff = GNUNET_TIME_UNIT_MILLISECONDS;
731 listen_connect (lh, NULL);
737 * Cancel the given listen operation.
739 * @param lh handle for the listen operation
742 GNUNET_SET_listen_cancel (struct GNUNET_SET_ListenHandle *lh)
744 LOG (GNUNET_ERROR_TYPE_DEBUG, "canceling listener\n");
745 /* listener's connection may have failed, thus mq/client could be NULL */
748 GNUNET_MQ_destroy (lh->mq);
751 if (NULL != lh->client)
753 GNUNET_CLIENT_disconnect (lh->client);
756 if (GNUNET_SCHEDULER_NO_TASK != lh->reconnect_task)
758 GNUNET_SCHEDULER_cancel (lh->reconnect_task);
759 lh->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
766 * Accept a request we got via #GNUNET_SET_listen. Must be called during
767 * #GNUNET_SET_listen, as the 'struct GNUNET_SET_Request' becomes invalid
769 * Call #GNUNET_SET_commit to provide the local set to use for the operation,
770 * and to begin the exchange with the remote peer.
772 * @param request request to accept
773 * @param result_mode specified how results will be returned,
774 * see `enum GNUNET_SET_ResultMode`.
775 * @param result_cb callback for the results
776 * @param result_cls closure for @a result_cb
777 * @return a handle to cancel the operation
779 struct GNUNET_SET_OperationHandle *
780 GNUNET_SET_accept (struct GNUNET_SET_Request *request,
781 enum GNUNET_SET_ResultMode result_mode,
782 GNUNET_SET_ResultIterator result_cb,
785 struct GNUNET_MQ_Envelope *mqm;
786 struct GNUNET_SET_OperationHandle *oh;
787 struct GNUNET_SET_AcceptMessage *msg;
789 GNUNET_assert (NULL != request);
790 GNUNET_assert (GNUNET_NO == request->accepted);
791 request->accepted = GNUNET_YES;
793 oh = GNUNET_new (struct GNUNET_SET_OperationHandle);
794 oh->result_cb = result_cb;
795 oh->result_cls = result_cls;
797 mqm = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SET_ACCEPT);
798 msg->accept_reject_id = htonl (request->accept_id);
799 msg->result_mode = htonl (result_mode);
801 oh->conclude_mqm = mqm;
802 oh->request_id_addr = &msg->request_id;
809 * Commit a set to be used with a set operation.
810 * This function is called once we have fully constructed
811 * the set that we want to use for the operation. At this
812 * time, the P2P protocol can then begin to exchange the
813 * set information and call the result callback with the
814 * result information.
816 * @param oh handle to the set operation
817 * @param set the set to use for the operation
818 * @return #GNUNET_OK on success, #GNUNET_SYSERR if the
819 * set is invalid (e.g. the set service crashed)
822 GNUNET_SET_commit (struct GNUNET_SET_OperationHandle *oh,
823 struct GNUNET_SET_Handle *set)
825 GNUNET_assert (NULL == oh->set);
826 if (GNUNET_YES == set->invalid)
827 return GNUNET_SYSERR;
828 GNUNET_assert (NULL != oh->conclude_mqm);
830 GNUNET_CONTAINER_DLL_insert (set->ops_head,
833 oh->request_id = GNUNET_MQ_assoc_add (set->mq, oh);
834 *oh->request_id_addr = htonl (oh->request_id);
835 GNUNET_MQ_send (set->mq, oh->conclude_mqm);
836 oh->conclude_mqm = NULL;
837 oh->request_id_addr = NULL;
843 * Iterate over all elements in the given set.
844 * Note that this operation involves transferring every element of the set
845 * from the service to the client, and is thus costly.
847 * @param set the set to iterate over
848 * @param iter the iterator to call for each element
849 * @param iter_cls closure for @a iter
850 * @return #GNUNET_YES if the iteration started successfuly,
851 * #GNUNET_NO if another iteration is active
852 * #GNUNET_SYSERR if the set is invalid (e.g. the server crashed, disconnected)
855 GNUNET_SET_iterate (struct GNUNET_SET_Handle *set,
856 GNUNET_SET_ElementIterator iter,
859 struct GNUNET_MQ_Envelope *ev;
862 GNUNET_assert (NULL != iter);
864 if (GNUNET_YES == set->invalid)
865 return GNUNET_SYSERR;
866 if (NULL != set->iterator)
868 LOG (GNUNET_ERROR_TYPE_DEBUG,
870 set->iterator = iter;
871 set->iterator_cls = iter_cls;
872 ev = GNUNET_MQ_msg_header (GNUNET_MESSAGE_TYPE_SET_ITER_REQUEST);
873 GNUNET_MQ_send (set->mq, ev);
877 /* end of set_api.c */