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3 Copyright (C) 2012-2016 GNUnet e.V.
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13 Affero General Public License for more details.
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18 SPDX-License-Identifier: AGPL3.0-or-later
22 * @author Florian Dold
23 * @author Christian Grothoff
26 * General-purpose message queue
28 * @defgroup mq MQ library
29 * General-purpose message queue
31 * @see [Documentation](https://gnunet.org/message-queue-api)
35 #ifndef GNUNET_MQ_LIB_H
36 #define GNUNET_MQ_LIB_H
38 #include "gnunet_scheduler_lib.h"
41 * Allocate an envelope, with extra space allocated after the space needed
42 * by the message struct.
43 * The allocated message will already have the type and size field set.
45 * @param mvar variable to store the allocated message in;
46 * must have a header field;
48 * @param esize extra space to allocate after the message
49 * @param type type of the message
50 * @return the MQ message
52 #define GNUNET_MQ_msg_extra(mvar, esize, type) \
53 GNUNET_MQ_msg_ (((struct GNUNET_MessageHeader **) &(mvar)), \
54 (esize) + sizeof *(mvar), \
58 * Allocate a GNUNET_MQ_Envelope.
59 * The contained message will already have the type and size field set.
61 * @param mvar variable to store the allocated message in;
62 * must have a header field;
64 * @param type type of the message
65 * @return the allocated envelope
67 #define GNUNET_MQ_msg(mvar, type) GNUNET_MQ_msg_extra (mvar, 0, type)
71 * Allocate a GNUNET_MQ_Envelope, where the message only consists of a header.
72 * The allocated message will already have the type and size field set.
74 * @param type type of the message
76 #define GNUNET_MQ_msg_header(type) \
77 GNUNET_MQ_msg_ (NULL, sizeof(struct GNUNET_MessageHeader), type)
81 * Allocate a GNUNET_MQ_Envelope, where the message only consists of a header and extra space.
82 * The allocated message will already have the type and size field set.
84 * @param mh pointer that will changed to point at to the allocated message header
85 * @param esize extra space to allocate after the message header
86 * @param type type of the message
88 #define GNUNET_MQ_msg_header_extra(mh, esize, type) \
89 GNUNET_MQ_msg_ (&mh, (esize) + sizeof(struct GNUNET_MessageHeader), type)
93 * Allocate a GNUNET_MQ_Envelope, and append a payload message after the given
96 * @param mvar pointer to a message struct, will be changed to point at the newly allocated message,
97 * whose size is 'sizeof(*mvar) + ntohs (mh->size)'
98 * @param type message type of the allocated message, has no effect on the nested message
99 * @param mh message to nest
100 * @return a newly allocated 'struct GNUNET_MQ_Envelope *'
102 #define GNUNET_MQ_msg_nested_mh(mvar, type, mh) \
104 struct GNUNET_MQ_Envelope *_ev; \
105 _ev = GNUNET_MQ_msg_nested_mh_ ((struct GNUNET_MessageHeader **) &(mvar), \
109 (void) (mvar)->header; /* type check */ \
115 * Return a pointer to the message at the end of the given message.
117 * @param var pointer to a message struct, the type of the expression determines the base size,
118 * the space after the base size is the nested message
119 * @return a 'struct GNUNET_MessageHeader *' that points at the nested message of the given message,
120 * or NULL if the given message in @a var does not have any space after the message struct
122 #define GNUNET_MQ_extract_nested_mh(var) \
123 GNUNET_MQ_extract_nested_mh_ ((struct GNUNET_MessageHeader *) (var), \
128 * Implementation of the #GNUNET_MQ_extract_nexted_mh macro.
130 * @param mh message header to extract nested message header from
131 * @param base_size size of the message before the nested message's header appears
132 * @return pointer to the nested message, does not copy the message
133 * OR NULL in case of a malformed message.
135 const struct GNUNET_MessageHeader *
136 GNUNET_MQ_extract_nested_mh_ (const struct GNUNET_MessageHeader *mh,
141 * Opaque handle to an envelope.
143 struct GNUNET_MQ_Envelope;
147 * Obtain message contained in envelope.
149 * @param env the envelope
150 * @return message contained in the envelope
152 const struct GNUNET_MessageHeader *
153 GNUNET_MQ_env_get_msg (const struct GNUNET_MQ_Envelope *env);
157 * Return next envelope in queue.
159 * @param env a queued envelope
160 * @return next one, or NULL
162 const struct GNUNET_MQ_Envelope *
163 GNUNET_MQ_env_next (const struct GNUNET_MQ_Envelope *env);
167 * Implementation of the #GNUNET_MQ_msg_nested_mh macro.
169 * @param mhp pointer to the message header pointer that will be changed to allocate at
170 * the newly allocated space for the message.
171 * @param base_size size of the data before the nested message
172 * @param type type of the message in the envelope
173 * @param nested_mh the message to append to the message after base_size
175 struct GNUNET_MQ_Envelope *
176 GNUNET_MQ_msg_nested_mh_ (struct GNUNET_MessageHeader **mhp,
179 const struct GNUNET_MessageHeader *nested_mh);
183 * Opaque handle to a message queue.
185 struct GNUNET_MQ_Handle;
189 * Error codes for the queue.
194 * Failed to read message from the network.
195 * FIXME: Likely not properly distinguished
196 * from TIMEOUT case in the code!
198 GNUNET_MQ_ERROR_READ = 1,
203 GNUNET_MQ_ERROR_WRITE = 2,
208 GNUNET_MQ_ERROR_TIMEOUT = 4,
211 * We received a message that was malformed and thus
212 * could not be passed to its handler.
214 GNUNET_MQ_ERROR_MALFORMED = 8,
217 * We received a message for which we have no matching
220 GNUNET_MQ_ERROR_NO_MATCH = 16
225 * Per envelope preferences and priorities.
227 enum GNUNET_MQ_PriorityPreferences
230 * Lowest priority, i.e. background traffic (i.e. NSE, FS).
231 * This is the default!
233 GNUNET_MQ_PRIO_BACKGROUND = 0,
236 * Best-effort traffic (i.e. CADET relay, DHT)
238 GNUNET_MQ_PRIO_BEST_EFFORT = 1,
241 * Urgent traffic (local peer, i.e. Conversation).
243 GNUNET_MQ_PRIO_URGENT = 2,
246 * Highest priority, control traffic (i.e. CORE/CADET KX).
248 GNUNET_MQ_PRIO_CRITICAL_CONTROL = 3,
251 * Bit mask to apply to extract the priority bits.
253 GNUNET_MQ_PRIORITY_MASK = 3,
256 * Flag to indicate that unreliable delivery is acceptable. This
257 * means TRANSPORT will not attempt to receive an
258 * acknowledgment. CORE will just pass this flag through. CADET
259 * will use unreliable delivery if this flag is set.
261 * Note that even without this flag, messages may be lost by
262 * TRANSPORT and CORE.
264 * Thus, how "strong" the semantics of reliable delivery are depends
267 GNUNET_MQ_PREF_UNRELIABLE = 16,
270 * Flag to indicate that low latency is important. This flag must
271 * generally not be used in combination with
272 * #GNUNET_MQ_PREF_CORKING_ALLOWED as it would be a contradiction.
273 * When this flags is set, the envelope may skip forward in the
274 * queue (depending on priority) and also TRANSPORT should attempt
275 * to pick a communicator with particularly low latency.
277 GNUNET_MQ_PREF_LOW_LATENCY = 32,
280 * Flag to indicate that CORKing is acceptable. This allows the
281 * receiver to delay transmission in hope of combining this message
282 * with other messages into a larger transmission with less
283 * per-message overhead.
285 GNUNET_MQ_PREF_CORK_ALLOWED = 64,
288 * Flag to indicate that high bandwidth is desired. This flag
289 * indicates that the method chosen for transmission should focus on
290 * overall goodput. It rarely makes sense to combine this flag with
291 * #GNUNET_MQ_PREF_LOW_LATENCY.
293 GNUNET_MQ_PREF_GOODPUT = 128,
296 * Flag to indicate that out-of-order delivery is OK.
298 GNUNET_MQ_PREF_OUT_OF_ORDER = 256,
303 * Called when a message has been received.
306 * @param msg the received message
308 typedef void (*GNUNET_MQ_MessageCallback) (
310 const struct GNUNET_MessageHeader *msg);
314 * Called when a message needs to be validated.
317 * @param msg the received message
318 * @return #GNUNET_OK if the message is well-formed,
319 * #GNUNET_SYSERR if not
321 typedef int (*GNUNET_MQ_MessageValidationCallback) (
323 const struct GNUNET_MessageHeader *msg);
327 * Signature of functions implementing the
328 * sending functionality of a message queue.
330 * @param mq the message queue
331 * @param msg the message to send
332 * @param impl_state state of the implementation
334 typedef void (*GNUNET_MQ_SendImpl) (struct GNUNET_MQ_Handle *mq,
335 const struct GNUNET_MessageHeader *msg,
340 * Signature of functions implementing the
341 * destruction of a message queue.
342 * Implementations must not free @a mq, but should
343 * take care of @a impl_state.
345 * @param mq the message queue to destroy
346 * @param impl_state state of the implementation
348 typedef void (*GNUNET_MQ_DestroyImpl) (struct GNUNET_MQ_Handle *mq,
353 * Implementation function that cancels the currently sent message.
355 * @param mq message queue
356 * @param impl_state state specific to the implementation
358 typedef void (*GNUNET_MQ_CancelImpl) (struct GNUNET_MQ_Handle *mq,
363 * Generic error handler, called with the appropriate
364 * error code and the same closure specified at the creation of
366 * Not every message queue implementation supports an error handler.
369 * @param error error code
371 typedef void (*GNUNET_MQ_ErrorHandler) (void *cls, enum GNUNET_MQ_Error error);
375 * Insert @a env into the envelope DLL starting at @a env_head
376 * Note that @a env must not be in any MQ while this function
377 * is used with DLLs defined outside of the MQ module. This
378 * is just in case some application needs to also manage a
379 * FIFO of envelopes independent of MQ itself and wants to
380 * re-use the pointers internal to @a env. Use with caution.
382 * @param[in|out] env_head of envelope DLL
383 * @param[in|out] env_tail tail of envelope DLL
384 * @param[in|out] env element to insert at the tail
387 GNUNET_MQ_dll_insert_head (struct GNUNET_MQ_Envelope **env_head,
388 struct GNUNET_MQ_Envelope **env_tail,
389 struct GNUNET_MQ_Envelope *env);
393 * Insert @a env into the envelope DLL starting at @a env_head
394 * Note that @a env must not be in any MQ while this function
395 * is used with DLLs defined outside of the MQ module. This
396 * is just in case some application needs to also manage a
397 * FIFO of envelopes independent of MQ itself and wants to
398 * re-use the pointers internal to @a env. Use with caution.
400 * @param[in|out] env_head of envelope DLL
401 * @param[in|out] env_tail tail of envelope DLL
402 * @param[in|out] env element to insert at the tail
405 GNUNET_MQ_dll_insert_tail (struct GNUNET_MQ_Envelope **env_head,
406 struct GNUNET_MQ_Envelope **env_tail,
407 struct GNUNET_MQ_Envelope *env);
411 * Remove @a env from the envelope DLL starting at @a env_head.
412 * Note that @a env must not be in any MQ while this function
413 * is used with DLLs defined outside of the MQ module. This
414 * is just in case some application needs to also manage a
415 * FIFO of envelopes independent of MQ itself and wants to
416 * re-use the pointers internal to @a env. Use with caution.
418 * @param[in|out] env_head of envelope DLL
419 * @param[in|out] env_tail tail of envelope DLL
420 * @param[in|out] env element to remove from the DLL
423 GNUNET_MQ_dll_remove (struct GNUNET_MQ_Envelope **env_head,
424 struct GNUNET_MQ_Envelope **env_tail,
425 struct GNUNET_MQ_Envelope *env);
429 * Copy an array of handlers.
431 * Useful if the array has been delared in local memory and needs to be
432 * persisted for future use.
434 * @param handlers Array of handlers to be copied.
435 * @return A newly allocated array of handlers.
436 * Needs to be freed with #GNUNET_free.
438 struct GNUNET_MQ_MessageHandler *
439 GNUNET_MQ_copy_handlers (const struct GNUNET_MQ_MessageHandler *handlers);
443 * Copy an array of handlers, appending AGPL handler.
445 * Useful if the array has been delared in local memory and needs to be
446 * persisted for future use.
448 * @param handlers Array of handlers to be copied. Can be NULL (nothing done).
449 * @param agpl_handler function to call for AGPL handling
450 * @param agpl_cls closure for @a agpl_handler
451 * @return A newly allocated array of handlers.
452 * Needs to be freed with #GNUNET_free.
454 struct GNUNET_MQ_MessageHandler *
455 GNUNET_MQ_copy_handlers2 (const struct GNUNET_MQ_MessageHandler *handlers,
456 GNUNET_MQ_MessageCallback agpl_handler,
461 * Count the handlers in a handler array.
463 * @param handlers Array of handlers to be counted.
464 * @return The number of handlers in the array.
467 GNUNET_MQ_count_handlers (const struct GNUNET_MQ_MessageHandler *handlers);
471 * Message handler for a specific message type.
473 struct GNUNET_MQ_MessageHandler
476 * Callback to validate a message of the specified @e type.
477 * The closure given to @e mv will be this struct (not @e ctx).
478 * Using NULL means only size-validation using
479 * @e expected_size. In this case, @e expected_size must
482 GNUNET_MQ_MessageValidationCallback mv;
485 * Callback, called every time a new message of
486 * the specified @e type has been receied.
487 * The closure given to @e mv will be this struct (not @e ctx).
489 GNUNET_MQ_MessageCallback cb;
492 * Closure for @e mv and @e cb.
497 * Type of the message this handler covers, in host byte order.
502 * Expected size of messages of this type. Minimum size of the
503 * message if @e mv is non-NULL. Messages of the given type will be
504 * discarded (and the connection closed with an error reported to
505 * the application) if they do not have the right size.
507 uint16_t expected_size;
512 * End-marker for the handlers array
514 #define GNUNET_MQ_handler_end() \
516 NULL, NULL, NULL, 0, 0 \
521 * Defines a static function @a name which takes as a single argument
522 * a message handler for fixed-sized messages of type @a code and with
523 * a message type argument of @a str. Given such an argument, the
524 * function @name will return a `struct GNUNET_MQ_MessageHandler`
525 * for the given message type.
527 * The macro is to be used as follows:
529 * struct GNUNET_MessageTest { ... }; // must be fixed size
531 * handle_test_message (void *cls,
532 * const struct GNUNET_MessageTest *msg)
535 * struct GNUNET_MQ_MessageHandler handlers[] = {
536 * GNUNET_MQ_hd_fixed_size(test_message,
537 * GNUNET_MESSAGE_TYPE_TEST,
538 * struct GNUNET_MessageTest,
540 * GNUNET_MQ_handler_end()
543 * @param name unique basename for the functions
544 * @param code message type constant
545 * @param str type of the message (a struct)
546 * @param ctx context for the callbacks
548 #define GNUNET_MQ_hd_fixed_size(name, code, str, ctx) \
550 void (*_cb)(void *cls, const str * msg) = &handle_ ## name; \
551 ((struct GNUNET_MQ_MessageHandler){ NULL, \
552 (GNUNET_MQ_MessageCallback) _cb, \
560 * Defines a static function @a name which takes two arguments and a
561 * context-pointer for validating and handling variable-sized messages
562 * of type @a code and with a message type argument of @a str. Given
563 * such arguments, the function @name will return a `struct
564 * GNUNET_MQ_MessageHandler` for the given message type.
566 * The macro is to be used as follows:
568 * struct GNUNET_MessageTest { ... }; // can be variable size
570 * check_test (void *cls,
571 * const struct GNUNET_MessageTest *msg)
573 * const char *ctx = cls;
574 * GNUNET_assert (0 == strcmp ("context", ctx));
578 * handle_test (void *cls,
579 * const struct GNUNET_MessageTest *msg)
581 * const char *ctx = cls;
582 * GNUNET_assert (0 == strcmp ("context", ctx));
586 * struct GNUNET_MQ_MessageHandler handlers[] = {
587 * GNUNET_MQ_hd_var_size(test_message,
588 * GNUNET_MESSAGE_TYPE_TEST,
589 * struct GNUNET_MessageTest,
591 * GNUNET_MQ_handler_end()
594 * @param name unique basename for the functions
595 * @param code message type constant
596 * @param str type of the message (a struct)
597 * @param ctx context for the callbacks
599 #define GNUNET_MQ_hd_var_size(name, code, str, ctx) \
601 int (*_mv)(void *cls, const str * msg) = &check_ ## name; \
602 void (*_cb)(void *cls, const str * msg) = &handle_ ## name; \
603 ((struct GNUNET_MQ_MessageHandler){ (GNUNET_MQ_MessageValidationCallback) \
605 (GNUNET_MQ_MessageCallback) _cb, \
613 * Insert code for a "check_" function that verifies that
614 * a given variable-length message received over the network
615 * is followed by a 0-terminated string. If the message @a m
616 * is not followed by a 0-terminated string, an error is logged
617 * and the function is returned with #GNUNET_NO.
619 * @param an IPC message with proper type to determine
620 * the size, starting with a `struct GNUNET_MessageHeader`
622 #define GNUNET_MQ_check_zero_termination(m) \
624 const char *str = (const char *) &m[1]; \
625 const struct GNUNET_MessageHeader *hdr = \
626 (const struct GNUNET_MessageHeader *) m; \
627 uint16_t slen = ntohs (hdr->size) - sizeof(*m); \
628 if ((0 == slen) || (memchr (str, 0, slen) != &str[slen - 1])) \
637 * Insert code for a "check_" function that verifies that
638 * a given variable-length message received over the network
639 * is followed by another variable-length message that fits
640 * exactly with the given size. If the message @a m
641 * is not followed by another `struct GNUNET_MessageHeader`
642 * with a size that adds up to the total size, an error is logged
643 * and the function is returned with #GNUNET_NO.
645 * @param an IPC message with proper type to determine
646 * the size, starting with a `struct GNUNET_MessageHeader`
648 #define GNUNET_MQ_check_boxed_message(m) \
650 const struct GNUNET_MessageHeader *inbox = \
651 (const struct GNUNET_MessageHeader *) &m[1]; \
652 const struct GNUNET_MessageHeader *hdr = \
653 (const struct GNUNET_MessageHeader *) m; \
654 uint16_t slen = ntohs (hdr->size) - sizeof(*m); \
655 if ((slen < sizeof(struct GNUNET_MessageHeader)) || \
656 (slen != ntohs (inbox->size))) \
665 * Call the message message handler that was registered
666 * for the type of the given message in the given @a handlers list.
668 * This function is indended to be used for the implementation
671 * @param handlers a set of handlers
672 * @param mh message to dispatch
673 * @return #GNUNET_OK on success, #GNUNET_NO if no handler matched,
674 * #GNUNET_SYSERR if message was rejected by check function
677 GNUNET_MQ_handle_message (const struct GNUNET_MQ_MessageHandler *handlers,
678 const struct GNUNET_MessageHeader *mh);
682 * Create a new envelope.
684 * @param mhp message header to store the allocated message header in, can be NULL
685 * @param size size of the message to allocate
686 * @param type type of the message, will be set in the allocated message
687 * @return the allocated MQ message
689 struct GNUNET_MQ_Envelope *
690 GNUNET_MQ_msg_ (struct GNUNET_MessageHeader **mhp,
696 * Create a new envelope by copying an existing message.
698 * @param hdr header of the message to copy
699 * @return envelope containing @a hdr
701 struct GNUNET_MQ_Envelope *
702 GNUNET_MQ_msg_copy (const struct GNUNET_MessageHeader *hdr);
706 * Discard the message queue message, free all
707 * allocated resources. Must be called in the event
708 * that a message is created but should not actually be sent.
710 * @param mqm the message to discard
713 GNUNET_MQ_discard (struct GNUNET_MQ_Envelope *mqm);
717 * Function to obtain the current envelope
718 * from within #GNUNET_MQ_SendImpl implementations.
720 * @param mq message queue to interrogate
721 * @return the current envelope
723 struct GNUNET_MQ_Envelope *
724 GNUNET_MQ_get_current_envelope (struct GNUNET_MQ_Handle *mq);
728 * Function to copy an envelope. The envelope must not yet
729 * be in any queue or have any options or callbacks set.
731 * @param env envelope to copy
732 * @return copy of @a env
734 struct GNUNET_MQ_Envelope *
735 GNUNET_MQ_env_copy (struct GNUNET_MQ_Envelope *env);
739 * Function to obtain the last envelope in the queue.
741 * @param mq message queue to interrogate
742 * @return the last envelope in the queue
744 struct GNUNET_MQ_Envelope *
745 GNUNET_MQ_get_last_envelope (struct GNUNET_MQ_Handle *mq);
749 * Set application-specific options for this envelope.
750 * Overrides the options set for the queue with
751 * #GNUNET_MQ_set_options() for this message only.
753 * @param env message to set options for
754 * @param pp priority and preferences to set for @a env
757 GNUNET_MQ_env_set_options (struct GNUNET_MQ_Envelope *env,
758 enum GNUNET_MQ_PriorityPreferences pp);
762 * Get performance preferences set for this envelope.
764 * @param env message to set options for
765 * @return priority and preferences to use
767 enum GNUNET_MQ_PriorityPreferences
768 GNUNET_MQ_env_get_options (struct GNUNET_MQ_Envelope *env);
772 * Combine performance preferences set for different
773 * envelopes that are being combined into one larger envelope.
775 * @param p1 one set of preferences
776 * @param p2 second set of preferences
777 * @return combined priority and preferences to use
779 enum GNUNET_MQ_PriorityPreferences
780 GNUNET_MQ_env_combine_options (enum GNUNET_MQ_PriorityPreferences p1,
781 enum GNUNET_MQ_PriorityPreferences p2);
785 * Remove the first envelope that has not yet been sent from the message
786 * queue and return it.
788 * @param mq queue to remove envelope from
789 * @return NULL if queue is empty (or has no envelope that is not under transmission)
791 struct GNUNET_MQ_Envelope *
792 GNUNET_MQ_unsent_head (struct GNUNET_MQ_Handle *mq);
796 * Set application-specific options for this queue.
798 * @param mq message queue to set options for
799 * @param pp priority and preferences to use by default
802 GNUNET_MQ_set_options (struct GNUNET_MQ_Handle *mq,
803 enum GNUNET_MQ_PriorityPreferences pp);
807 * Obtain the current length of the message queue.
809 * @param mq queue to inspect
810 * @return number of queued, non-transmitted messages
813 GNUNET_MQ_get_length (struct GNUNET_MQ_Handle *mq);
817 * Send a message with the given message queue.
818 * May only be called once per message.
820 * @param mq message queue
821 * @param ev the envelope with the message to send.
824 GNUNET_MQ_send (struct GNUNET_MQ_Handle *mq, struct GNUNET_MQ_Envelope *ev);
828 * Send a copy of a message with the given message queue.
829 * Can be called repeatedly on the same envelope.
831 * @param mq message queue
832 * @param ev the envelope with the message to send.
835 GNUNET_MQ_send_copy (struct GNUNET_MQ_Handle *mq,
836 const struct GNUNET_MQ_Envelope *ev);
840 * Cancel sending the message. Message must have been sent with
841 * #GNUNET_MQ_send before. May not be called after the notify sent
842 * callback has been called
844 * @param ev queued envelope to cancel
847 GNUNET_MQ_send_cancel (struct GNUNET_MQ_Envelope *ev);
851 * Associate the assoc_data in @a mq with a unique request id.
853 * @param mq message queue, id will be unique for the queue
854 * @param assoc_data to associate
857 GNUNET_MQ_assoc_add (struct GNUNET_MQ_Handle *mq, void *assoc_data);
861 * Get the data associated with a @a request_id in a queue
863 * @param mq the message queue with the association
864 * @param request_id the request id we are interested in
865 * @return the associated data
868 GNUNET_MQ_assoc_get (struct GNUNET_MQ_Handle *mq, uint32_t request_id);
872 * Remove the association for a @a request_id
874 * @param mq the message queue with the association
875 * @param request_id the request id we want to remove
876 * @return the associated data
879 GNUNET_MQ_assoc_remove (struct GNUNET_MQ_Handle *mq, uint32_t request_id);
883 * Create a message queue for the specified handlers.
885 * @param send function the implements sending messages
886 * @param destroy function that implements destroying the queue
887 * @param cancel function that implements canceling a message
888 * @param impl_state for the queue, passed to @a send, @a destroy and @a cancel
889 * @param handlers array of message handlers
890 * @param error_handler handler for read and write errors
891 * @param cls closure for message handlers and error handler
892 * @return a new message queue
894 struct GNUNET_MQ_Handle *
895 GNUNET_MQ_queue_for_callbacks (GNUNET_MQ_SendImpl send,
896 GNUNET_MQ_DestroyImpl destroy,
897 GNUNET_MQ_CancelImpl cancel,
899 const struct GNUNET_MQ_MessageHandler *handlers,
900 GNUNET_MQ_ErrorHandler error_handler,
905 * Change the closure argument in all of the `handlers` of the
908 * @param mq to modify
909 * @param handlers_cls new closure to use
912 GNUNET_MQ_set_handlers_closure (struct GNUNET_MQ_Handle *mq,
917 * Call a callback once the envelope has been sent, that is,
918 * sending it can not be canceled anymore.
919 * There can be only one notify sent callback per envelope.
921 * @param ev message to call the notify callback for
922 * @param cb the notify callback
923 * @param cb_cls closure for the callback
926 GNUNET_MQ_notify_sent (struct GNUNET_MQ_Envelope *ev,
927 GNUNET_SCHEDULER_TaskCallback cb,
932 * Destroy the message queue.
934 * @param mq message queue to destroy
937 GNUNET_MQ_destroy (struct GNUNET_MQ_Handle *mq);
941 * Handle we return for callbacks registered to be
942 * notified when #GNUNET_MQ_destroy() is called on a queue.
944 struct GNUNET_MQ_DestroyNotificationHandle;
948 * Register function to be called whenever @a mq is being
951 * @param mq message queue to watch
952 * @param cb function to call on @a mq destruction
953 * @param cb_cls closure for @a cb
954 * @return handle for #GNUNET_MQ_destroy_notify_cancel().
956 struct GNUNET_MQ_DestroyNotificationHandle *
957 GNUNET_MQ_destroy_notify (struct GNUNET_MQ_Handle *mq,
958 GNUNET_SCHEDULER_TaskCallback cb,
962 * Cancel registration from #GNUNET_MQ_destroy_notify().
964 * @param dnh handle for registration to cancel
967 GNUNET_MQ_destroy_notify_cancel (
968 struct GNUNET_MQ_DestroyNotificationHandle *dnh);
972 * Call the message message handler that was registered
973 * for the type of the given message in the given message queue.
975 * This function is indended to be used for the implementation
978 * @param mq message queue with the handlers
979 * @param mh message to dispatch
982 GNUNET_MQ_inject_message (struct GNUNET_MQ_Handle *mq,
983 const struct GNUNET_MessageHeader *mh);
987 * Call the error handler of a message queue with the given
988 * error code. If there is no error handler, log a warning.
990 * This function is intended to be used for the implementation
993 * @param mq message queue
994 * @param error the error type
997 GNUNET_MQ_inject_error (struct GNUNET_MQ_Handle *mq,
998 enum GNUNET_MQ_Error error);
1002 * Call the send implementation for the next queued message, if any.
1003 * Calls the send notification for the current message unless
1004 * #GNUNET_MQ_impl_send_in_flight was called for this envelope.
1006 * Only useful for implementing message queues, results in undefined
1007 * behavior if not used carefully.
1009 * @param mq message queue to send the next message with
1012 GNUNET_MQ_impl_send_continue (struct GNUNET_MQ_Handle *mq);
1016 * Call the send notification for the current message, but do not
1017 * try to send the next message until #gnunet_mq_impl_send_continue
1020 * Only useful for implementing message queues, results in undefined
1021 * behavior if not used carefully.
1023 * @param mq message queue to send the next message with
1026 GNUNET_MQ_impl_send_in_flight (struct GNUNET_MQ_Handle *mq);
1030 * Get the implementation state associated with the
1033 * While the GNUNET_MQ_Impl* callbacks receive the
1034 * implementation state, continuations that are scheduled
1035 * by the implementation function often only have one closure
1036 * argument, with this function it is possible to get at the
1037 * implementation state when only passing the `struct GNUNET_MQ_Handle`
1040 * @param mq message queue with the current message
1041 * @return message to send, never NULL
1044 GNUNET_MQ_impl_state (struct GNUNET_MQ_Handle *mq);
1048 * Get the message that should currently be sent.
1049 * Fails if there is no current message.
1050 * Only useful for implementing message queues,
1051 * results in undefined behavior if not used carefully.
1053 * @param mq message queue with the current message
1054 * @return message to send, never NULL
1056 const struct GNUNET_MessageHeader *
1057 GNUNET_MQ_impl_current (struct GNUNET_MQ_Handle *mq);
1061 * Enum defining all known preference categories.
1063 * @deprecated will be replaced by `enum GNUNET_MQ_PriorityPreference`
1065 enum GNUNET_MQ_PreferenceKind
1068 * No preference was expressed.
1070 GNUNET_MQ_PREFERENCE_NONE = 0,
1073 * The preferred transmission for this envelope focuses on
1074 * maximizing bandwidth.
1076 GNUNET_MQ_PREFERENCE_BANDWIDTH = 1,
1079 * The preferred transmission for this envelope foces on
1080 * minimizing latency.
1082 GNUNET_MQ_PREFERENCE_LATENCY = 2,
1085 * The preferred transmission for this envelope foces on
1088 GNUNET_MQ_PREFERENCE_RELIABILITY = 3
1091 * Number of preference values allowed.
1093 #define GNUNET_MQ_PREFERENCE_COUNT 4
1098 * Convert an `enum GNUNET_MQ_PreferenceType` to a string
1100 * @param type the preference type
1101 * @return a string or NULL if invalid
1103 * @deprecated will be replaced by `enum GNUNET_MQ_PriorityPreference`
1106 GNUNET_MQ_preference_to_string (enum GNUNET_MQ_PreferenceKind type);
1111 /** @} */ /* end of group mq */