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22 * @file include/gnunet_psyc_service.h
23 * @brief PSYC service; high-level access to the PSYC protocol
24 * note that clients of this API are NOT expected to
25 * understand the PSYC message format, only the semantics!
26 * Parsing (and serializing) the PSYC stream format is done
27 * within the implementation of the libgnunetpsyc library,
28 * and this API deliberately exposes as little as possible
29 * of the actual data stream format to the application!
30 * @author Christian Grothoff
31 * @author Gabor X Toth
34 * - this API does not know about psyc's "root" and "places";
35 * there is no 'root' in GNUnet-Psyc as we're decentralized;
36 * 'places' and 'persons' are combined within the same
37 * abstraction, that of a "channel". Channels are identified
38 * and accessed in this API using a public/private key.
39 * Higher-level applications should use NAMES within GNS
40 * to obtain public keys, and the distinction between
41 * 'places' and 'persons' can then be made with the help
42 * of the naming system (and/or conventions).
43 * Channels are (as in PSYC) organized into a hierarchy; each
44 * channel master (the one with the private key) is then
45 * the operator of the multicast group (its Origin in
46 * the terminology of the multicast API).
47 * - The API supports passing large amounts of data using
48 * 'streaming' for the argument passed to a method. State
49 * and variables must fit into memory and cannot be streamed
50 * (thus, no passing of 4 GB of data in a variable;
51 * once we implement this, we might want to create a
52 * @c \#define for the maximum size of a variable).
53 * - PSYC defines standard variables, methods, etc. This
54 * library deliberately abstracts over all of these; a
55 * higher-level API should combine the naming system (GNS)
56 * and standard methods (message, join, part, warn,
57 * fail, error) and variables (action, color, time,
58 * tag, etc.). However, this API does take over the
59 * routing variables, specifically 'context' (channel),
60 * and 'source'. We only kind-of support 'target', as
61 * the target is either everyone in the group or the
62 * origin, and never just a single member of the group;
63 * for such individual messages, an application needs to
64 * construct an 'inbox' channel where the master (only)
65 * receives messages (but never forwards; private responses
66 * would be transmitted by joining the senders 'inbox'
67 * channel -- or a inbox#bob subchannel). The
68 * goal for all of this is to keep the abstractions in this
69 * API minimal: interaction with multicast, try \& slice,
70 * state/variable/channel management. Higher-level
71 * operations belong elsewhere (so maybe this API should
72 * be called 'PSYC-low', whereas a higher-level API
73 * implementing defaults for standard methods and
74 * variables might be called 'PSYC-std' or 'PSYC-high'.
77 #ifndef GNUNET_PSYC_SERVICE_H
78 #define GNUNET_PSYC_SERVICE_H
83 #if 0 /* keep Emacsens' auto-indent happy */
88 #include "gnunet_util_lib.h"
89 #include "gnunet_env_lib.h"
90 #include "gnunet_multicast_service.h"
94 * Version number of GNUnet-PSYC API.
96 #define GNUNET_PSYC_VERSION 0x00000000
100 * Policy flags for a channel.
102 enum GNUNET_PSYC_ChannelFlags
105 * Admission must be confirmed by the master.
107 GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL = 1 << 0,
110 * Past messages are only available to slaves who were admitted at the time
111 * they were sent to the channel.
113 GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY = 1 << 1
117 * PSYC channel policies.
119 enum GNUNET_PSYC_Policy
122 * Anyone can join the channel, without announcing his presence;
123 * all messages are always public and can be distributed freely.
124 * Joins may be announced, but this is not required.
126 GNUNET_PSYC_CHANNEL_ANONYMOUS = 0,
129 * The master must approve membership to the channel, messages must only be
130 * distributed to current channel slaves. This includes the channel
131 * state as well as transient messages.
133 GNUNET_PSYC_CHANNEL_PRIVATE
134 = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL
135 | GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY
139 * Anyone can freely join the channel (no approval required);
140 * however, messages must only be distributed to current channel
141 * slaves, so the master must still acknowledge that the slave
142 * joined before transient messages are delivered. As approval is
143 * guaranteed, the presistent channel state can be synchronized freely
144 * immediately, prior to master confirmation.
146 GNUNET_PSYC_CHANNEL_OPEN
147 = GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY,
150 * The master must approve joins to the channel, but past messages can be
151 * freely distributed to slaves.
153 GNUNET_PSYC_CHANNEL_CLOSED
154 = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL,
159 enum GNUNET_PSYC_MessageFlags
162 * Historic message, retrieved from PSYCstore.
164 GNUNET_PSYC_MESSAGE_HISTORIC = 1 << 0,
167 * Request from slave to master.
169 GNUNET_PSYC_MESSAGE_REQUEST = 1 << 1
172 GNUNET_NETWORK_STRUCT_BEGIN
175 * Header of a PSYC message.
177 struct GNUNET_PSYC_MessageHeader
180 * Generic message header with size and type information.
182 struct GNUNET_MessageHeader header;
185 * Flags for this message fragment.
187 * @see enum GNUNET_PSYC_MessageFlags
189 uint32_t flags GNUNET_PACKED;
192 * Number of the message this message part belongs to.
194 uint64_t message_id GNUNET_PACKED;
197 * Sending slave's public key.
198 * Not set if the message is from the master.
200 struct GNUNET_CRYPTO_EddsaPublicKey slave_key;
202 /* Followed by concatenated PSYC message parts:
203 * messages with GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_* types
209 * The method of a message.
211 struct GNUNET_PSYC_MessageMethod
214 * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
216 struct GNUNET_MessageHeader header;
219 * OR'ed GNUNET_PSYC_MasterTransmitFlags
221 uint32_t flags GNUNET_PACKED;
223 /* Followed by NUL-terminated method name. */
228 * A modifier of a message.
230 struct GNUNET_PSYC_MessageModifier
233 * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
235 struct GNUNET_MessageHeader header;
240 uint32_t value_size GNUNET_PACKED;
243 * Size of name, including NUL terminator.
245 uint16_t name_size GNUNET_PACKED;
248 * enum GNUNET_ENV_Operator
252 /* Followed by NUL-terminated name, then the value. */
255 GNUNET_NETWORK_STRUCT_END
257 #define GNUNET_PSYC_MODIFIER_MAX_PAYLOAD \
258 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
259 - sizeof (struct GNUNET_PSYC_MessageModifier)
261 #define GNUNET_PSYC_MOD_CONT_MAX_PAYLOAD \
262 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
263 - sizeof (struct GNUNET_MessageHeader)
265 #define GNUNET_PSYC_DATA_MAX_PAYLOAD \
266 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
267 - sizeof (struct GNUNET_MessageHeader)
270 * Handle that identifies a join request.
272 * Used to match calls to #GNUNET_PSYC_JoinCallback to the
273 * corresponding calls to GNUNET_PSYC_join_decision().
275 struct GNUNET_PSYC_JoinHandle;
279 * Method called from PSYC upon receiving part of a message.
281 * @param cls Closure.
282 * @param msg Message part, one of the following types:
283 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_HEADER
284 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
285 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
286 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MOD_CONT
287 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_DATA
290 (*GNUNET_PSYC_MessageCallback) (void *cls,
293 const struct GNUNET_MessageHeader *msg);
297 * Method called from PSYC upon receiving a join request.
299 * @param cls Closure.
300 * @param slave requesting to join.
301 * @param method_name Method name in the join request.
302 * @param variable_count Number of elements in the @a variables array.
303 * @param variables Transient variables for the join request.
304 * @param data Data stream given to the method (might not be zero-terminated
305 * if data is binary).
306 * @param data_size Number of bytes in @a data.
307 * @param jh Join handle to use with GNUNET_PSYC_join_decision()
310 (*GNUNET_PSYC_JoinCallback) (void *cls,
311 const struct GNUNET_CRYPTO_EddsaPublicKey
313 const char *method_name,
314 size_t variable_count,
315 const struct GNUNET_ENV_Modifier *variables,
318 struct GNUNET_PSYC_JoinHandle *jh);
322 * Function to call with the decision made for a join request.
324 * Must be called once and only once in response to an invocation of the
325 * #GNUNET_PSYC_JoinCallback.
327 * @param jh Join request handle.
328 * @param is_admitted #GNUNET_YES if joining is approved,
329 * #GNUNET_NO if it is disapproved.
330 * @param relay_count Number of relays given.
331 * @param relays Array of suggested peers that might be useful relays to use
332 * when joining the multicast group (essentially a list of peers that
333 * are already part of the multicast group and might thus be willing
334 * to help with routing). If empty, only this local peer (which must
335 * be the multicast origin) is a good candidate for building the
336 * multicast tree. Note that it is unnecessary to specify our own
337 * peer identity in this array.
338 * @param method_name Method name for the message transmitted with the response.
339 * @param env Environment containing transient variables for the message,
341 * @param data Data of the message.
342 * @param data_size Size of @a data.
345 GNUNET_PSYC_join_decision (struct GNUNET_PSYC_JoinHandle *jh,
347 uint32_t relay_count,
348 const struct GNUNET_PeerIdentity *relays,
349 const char *method_name,
350 const struct GNUNET_ENV_Environment *env,
356 * Handle for the master of a PSYC channel.
358 struct GNUNET_PSYC_Master;
362 * Function called after the channel master started.
364 * @param cls Closure.
365 * @param last_message_id Last message ID sent to the channel.
368 (*GNUNET_PSYC_MasterStartCallback) (void *cls, uint64_t max_message_id);
372 * Start a PSYC master channel.
374 * Will start a multicast group identified by the given ECC key. Messages
375 * received from group members will be given to the respective handler methods.
376 * If a new member wants to join a group, the "join" method handler will be
377 * invoked; the join handler must then generate a "join" message to approve the
378 * joining of the new member. The channel can also change group membership
379 * without explicit requests. Note that PSYC doesn't itself "understand" join
380 * or part messages, the respective methods must call other PSYC functions to
381 * inform PSYC about the meaning of the respective events.
383 * @param cfg Configuration to use (to connect to PSYC service).
384 * @param channel_key ECC key that will be used to sign messages for this
385 * PSYC session. The public key is used to identify the PSYC channel.
386 * Note that end-users will usually not use the private key directly, but
387 * rather look it up in GNS for places managed by other users, or select
388 * a file with the private key(s) when setting up their own channels
389 * FIXME: we'll likely want to use NOT the p521 curve here, but a cheaper
391 * @param policy Channel policy specifying join and history restrictions.
392 * Used to automate join decisions.
393 * @param message_cb Function to invoke on message parts received from slaves.
394 * @param join_cb Function to invoke when a peer wants to join.
395 * @param master_started_cb Function to invoke after the channel master started.
396 * @param cls Closure for @a method and @a join_cb.
397 * @return Handle for the channel master, NULL on error.
399 struct GNUNET_PSYC_Master *
400 GNUNET_PSYC_master_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
401 const struct GNUNET_CRYPTO_EddsaPrivateKey *channel_key,
402 enum GNUNET_PSYC_Policy policy,
403 GNUNET_PSYC_MessageCallback message_cb,
404 GNUNET_PSYC_JoinCallback join_cb,
405 GNUNET_PSYC_MasterStartCallback master_started_cb,
410 * Function called to provide data for a transmission via PSYC.
412 * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
413 * invalidates the respective transmission handle.
415 * @param cls Closure.
416 * @param[in,out] data_size Initially set to the number of bytes available in
417 * @a data, should be set to the number of bytes written to data.
418 * @param[out] data Where to write the body of the message to give to the
419 * method. The function must copy at most @a data_size bytes to @a data.
420 * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
421 * #GNUNET_NO on success, if more data is to be transmitted later.
422 * Should be used if @a data_size was not big enough to take all the
423 * data. If 0 is returned in @a data_size the transmission is paused,
424 * and can be resumed with GNUNET_PSYC_master_transmit_resume().
425 * #GNUNET_YES if this completes the transmission (all data supplied)
428 (*GNUNET_PSYC_TransmitNotifyData) (void *cls,
433 * Function called to provide a modifier for a transmission via PSYC.
435 * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
436 * invalidates the respective transmission handle.
438 * @param cls Closure.
439 * @param[in,out] data_size Initially set to the number of bytes available in
440 * @a data, should be set to the number of bytes written to data.
441 * @param[out] data Where to write the modifier's name and value.
442 * The function must copy at most @a data_size bytes to @a data.
443 * When this callback is first called for a modifier, @a data should
444 * contain: "name\0value". If the whole value does not fit, subsequent
445 * calls to this function should write continuations of the value to
447 * @param[out] oper Where to write the operator of the modifier.
448 * Only needed during the first call to this callback at the beginning
449 * of the modifier. In case of subsequent calls asking for value
450 * continuations @a oper is set to #NULL.
451 * @param[out] value_size Where to write the full size of the value.
452 * Only needed during the first call to this callback at the beginning
453 * of the modifier. In case of subsequent calls asking for value
454 * continuations @a value_size is set to #NULL.
455 * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
456 * #GNUNET_NO on success, if more data is to be transmitted later.
457 * Should be used if @a data_size was not big enough to take all the
458 * data for the modifier's value (the name must be always returned
459 * during the first call to this callback).
460 * If 0 is returned in @a data_size the transmission is paused,
461 * and can be resumed with GNUNET_PSYC_master_transmit_resume().
462 * #GNUNET_YES if this completes the modifier (the whole value is supplied).
465 (*GNUNET_PSYC_TransmitNotifyModifier) (void *cls,
469 uint32_t *value_size);
472 * Flags for transmitting messages to a channel by the master.
474 enum GNUNET_PSYC_MasterTransmitFlags
476 GNUNET_PSYC_MASTER_TRANSMIT_NONE = 0,
478 * Whether this message should reset the channel state,
479 * i.e. remove all previously stored state variables.
481 GNUNET_PSYC_MASTER_TRANSMIT_RESET_STATE = 1 << 0,
484 * Whether we need to increment the group generation counter after
485 * transmitting this message.
487 GNUNET_PSYC_MASTER_TRANSMIT_INC_GROUP_GEN = 1 << 1,
490 * Add PSYC header variable with the hash of the current channel state.
492 GNUNET_PSYC_MASTER_TRANSMIT_ADD_STATE_HASH = 1 << 2
497 * Handle for a pending PSYC transmission operation.
499 struct GNUNET_PSYC_MasterTransmitHandle;
503 * Send a message to call a method to all members in the PSYC channel.
505 * @param master Handle to the PSYC channel.
506 * @param method_name Which method should be invoked.
507 * @param notify_mod Function to call to obtain modifiers.
508 * @param notify_data Function to call to obtain fragments of the data.
509 * @param notify_cls Closure for @a notify_mod and @a notify_data.
510 * @param flags Flags for the message being transmitted.
511 * @return Transmission handle, NULL on error (i.e. more than one request queued).
513 struct GNUNET_PSYC_MasterTransmitHandle *
514 GNUNET_PSYC_master_transmit (struct GNUNET_PSYC_Master *master,
515 const char *method_name,
516 GNUNET_PSYC_TransmitNotifyModifier notify_mod,
517 GNUNET_PSYC_TransmitNotifyData notify_data,
519 enum GNUNET_PSYC_MasterTransmitFlags flags);
523 * Resume transmission to the channel.
525 * @param th Handle of the request that is being resumed.
528 GNUNET_PSYC_master_transmit_resume (struct GNUNET_PSYC_MasterTransmitHandle *th);
532 * Abort transmission request to channel.
534 * @param th Handle of the request that is being aborted.
537 GNUNET_PSYC_master_transmit_cancel (struct GNUNET_PSYC_MasterTransmitHandle *th);
541 * Stop a PSYC master channel.
543 * @param master PSYC channel master to stop.
546 GNUNET_PSYC_master_stop (struct GNUNET_PSYC_Master *master);
550 * Handle for a PSYC channel slave.
552 struct GNUNET_PSYC_Slave;
556 * Function called after the slave joined.
558 * @param cls Closure.
559 * @param max_message_id Last message ID sent to the channel.
562 (*GNUNET_PSYC_SlaveJoinCallback) (void *cls, uint64_t max_message_id);
566 * Join a PSYC channel.
568 * The entity joining is always the local peer. The user must immediately use
569 * the GNUNET_PSYC_slave_transmit() functions to transmit a @e join_msg to the
570 * channel; if the join request succeeds, the channel state (and @e recent
571 * method calls) will be replayed to the joining member. There is no explicit
572 * notification on failure (as the channel may simply take days to approve,
573 * and disapproval is simply being ignored).
575 * @param cfg Configuration to use.
576 * @param channel_key ECC public key that identifies the channel we wish to join.
577 * @param slave_key ECC private-public key pair that identifies the slave, and
578 * used by multicast to sign the join request and subsequent unicast
579 * requests sent to the master.
580 * @param origin Peer identity of the origin.
581 * @param relay_count Number of peers in the @a relays array.
582 * @param relays Peer identities of members of the multicast group, which serve
583 * as relays and used to join the group at.
584 * @param message_cb Function to invoke on message parts received from the
585 * channel, typically at least contains method handlers for @e join and
587 * @param join_cb function invoked once we have joined with the current
588 * message ID of the channel
589 * @param slave_joined_cb Function to invoke when a peer wants to join.
590 * @param cls Closure for @a message_cb and @a slave_joined_cb.
591 * @param method_name Method name for the join request.
592 * @param env Environment containing transient variables for the request, or NULL.
593 * @param data Payload for the join message.
594 * @param data_size Number of bytes in @a data.
595 * @return Handle for the slave, NULL on error.
597 struct GNUNET_PSYC_Slave *
598 GNUNET_PSYC_slave_join (const struct GNUNET_CONFIGURATION_Handle *cfg,
599 const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
600 const struct GNUNET_CRYPTO_EddsaPrivateKey *slave_key,
601 const struct GNUNET_PeerIdentity *origin,
602 uint32_t relay_count,
603 const struct GNUNET_PeerIdentity *relays,
604 GNUNET_PSYC_MessageCallback message_cb,
605 GNUNET_PSYC_JoinCallback join_cb,
606 GNUNET_PSYC_SlaveJoinCallback slave_joined_cb,
608 const char *method_name,
609 const struct GNUNET_ENV_Environment *env,
615 * Part a PSYC channel.
617 * Will terminate the connection to the PSYC service. Polite clients should
618 * first explicitly send a part request (via GNUNET_PSYC_slave_transmit()).
620 * @param slave Slave handle.
623 GNUNET_PSYC_slave_part (struct GNUNET_PSYC_Slave *slave);
627 * Flags for transmitting messages to the channel master by a slave.
629 enum GNUNET_PSYC_SlaveTransmitFlags
631 GNUNET_PSYC_SLAVE_TRANSMIT_NONE = 0
636 * Handle for a pending PSYC transmission operation.
638 struct GNUNET_PSYC_SlaveTransmitHandle;
642 * Request a message to be sent to the channel master.
644 * @param slave Slave handle.
645 * @param method_name Which (PSYC) method should be invoked (on host).
646 * @param notify_mod Function to call to obtain modifiers.
647 * @param notify_data Function to call to obtain fragments of the data.
648 * @param notify_cls Closure for @a notify.
649 * @param flags Flags for the message being transmitted.
650 * @return Transmission handle, NULL on error (i.e. more than one request queued).
652 struct GNUNET_PSYC_SlaveTransmitHandle *
653 GNUNET_PSYC_slave_transmit (struct GNUNET_PSYC_Slave *slave,
654 const char *method_name,
655 GNUNET_PSYC_TransmitNotifyModifier notify_mod,
656 GNUNET_PSYC_TransmitNotifyData notify_data,
658 enum GNUNET_PSYC_SlaveTransmitFlags flags);
662 * Resume transmission to the master.
664 * @param th Handle of the request that is being resumed.
667 GNUNET_PSYC_slave_transmit_resume (struct GNUNET_PSYC_SlaveTransmitHandle *th);
671 * Abort transmission request to master.
673 * @param th Handle of the request that is being aborted.
676 GNUNET_PSYC_slave_transmit_cancel (struct GNUNET_PSYC_SlaveTransmitHandle *th);
680 * Handle to access PSYC channel operations for both the master and slaves.
682 struct GNUNET_PSYC_Channel;
686 * Convert a channel @a master to a @e channel handle to access the @e channel
689 * @param master Channel master handle.
690 * @return Channel handle, valid for as long as @a master is valid.
692 struct GNUNET_PSYC_Channel *
693 GNUNET_PSYC_master_get_channel (struct GNUNET_PSYC_Master *master);
697 * Convert @a slave to a @e channel handle to access the @e channel APIs.
699 * @param slave Slave handle.
700 * @return Channel handle, valid for as long as @a slave is valid.
702 struct GNUNET_PSYC_Channel *
703 GNUNET_PSYC_slave_get_channel (struct GNUNET_PSYC_Slave *slave);
707 * Add a slave to the channel's membership list.
709 * Note that this will NOT generate any PSYC traffic, it will merely update the
710 * local database to modify how we react to <em>membership test</em> queries.
711 * The channel master still needs to explicitly transmit a @e join message to
712 * notify other channel members and they then also must still call this function
713 * in their respective methods handling the @e join message. This way, how @e
714 * join and @e part operations are exactly implemented is still up to the
715 * application; for example, there might be a @e part_all method to kick out
718 * Note that channel slaves are explicitly trusted to execute such methods
719 * correctly; not doing so correctly will result in either denying other slaves
720 * access or offering access to channel data to non-members.
722 * @param channel Channel handle.
723 * @param slave_key Identity of channel slave to add.
724 * @param announced_at ID of the message that announced the membership change.
725 * @param effective_since Addition of slave is in effect since this message ID.
728 GNUNET_PSYC_channel_slave_add (struct GNUNET_PSYC_Channel *channel,
729 const struct GNUNET_CRYPTO_EddsaPublicKey *slave_key,
730 uint64_t announced_at,
731 uint64_t effective_since);
735 * Remove a slave from the channel's membership list.
737 * Note that this will NOT generate any PSYC traffic, it will merely update the
738 * local database to modify how we react to <em>membership test</em> queries.
739 * The channel master still needs to explicitly transmit a @e part message to
740 * notify other channel members and they then also must still call this function
741 * in their respective methods handling the @e part message. This way, how
742 * @e join and @e part operations are exactly implemented is still up to the
743 * application; for example, there might be a @e part_all message to kick out
746 * Note that channel members are explicitly trusted to perform these
747 * operations correctly; not doing so correctly will result in either
748 * denying members access or offering access to channel data to
751 * @param channel Channel handle.
752 * @param slave_key Identity of channel slave to remove.
753 * @param announced_at ID of the message that announced the membership change.
756 GNUNET_PSYC_channel_slave_remove (struct GNUNET_PSYC_Channel *channel,
757 const struct GNUNET_CRYPTO_EddsaPublicKey
759 uint64_t announced_at);
763 * Function called to inform a member about stored state values for a channel.
765 * @param cls Closure.
766 * @param name Name of the state variable. A NULL value indicates that there
767 * are no more state variables to be returned.
768 * @param value Value of the state variable.
769 * @param value_size Number of bytes in @a value.
772 (*GNUNET_PSYC_StateCallback) (void *cls,
779 * Function called when a requested operation has finished.
781 * @param cls Closure.
784 (*GNUNET_PSYC_FinishCallback) (void *cls);
788 * Handle to a story telling operation.
790 struct GNUNET_PSYC_Story;
794 * Request to be told the message history of the channel.
796 * Historic messages (but NOT the state at the time) will be replayed (given to
797 * the normal method handlers) if available and if access is permitted.
799 * To get the latest message, use 0 for both the start and end message ID.
801 * @param channel Which channel should be replayed?
802 * @param start_message_id Earliest interesting point in history.
803 * @param end_message_id Last (exclusive) interesting point in history.
804 * @param message_cb Function to invoke on message parts received from the story.
805 * @param finish_cb Function to call when the requested story has been fully
806 * told (counting message IDs might not suffice, as some messages
807 * might be secret and thus the listener would not know the story is
808 * finished without being told explicitly); once this function
809 * has been called, the client must not call
810 * GNUNET_PSYC_channel_story_tell_cancel() anymore.
811 * @param cls Closure for the callbacks.
812 * @return Handle to cancel story telling operation.
814 struct GNUNET_PSYC_Story *
815 GNUNET_PSYC_channel_story_tell (struct GNUNET_PSYC_Channel *channel,
816 uint64_t start_message_id,
817 uint64_t end_message_id,
818 GNUNET_PSYC_MessageCallback message_cb,
819 GNUNET_PSYC_FinishCallback finish_cb,
824 * Abort story telling.
826 * This function must not be called from within method handlers (as given to
827 * GNUNET_PSYC_slave_join()) of the slave.
829 * @param story Story telling operation to stop.
832 GNUNET_PSYC_channel_story_tell_cancel (struct GNUNET_PSYC_Story *story);
836 * Handle for a state query operation.
838 struct GNUNET_PSYC_StateQuery;
842 * Retrieve the best matching channel state variable.
844 * If the requested variable name is not present in the state, the nearest
845 * less-specific name is matched; for example, requesting "_a_b" will match "_a"
846 * if "_a_b" does not exist.
848 * @param channel Channel handle.
849 * @param full_name Full name of the requested variable, the actual variable
850 * returned might have a shorter name..
851 * @param cb Function called once when a matching state variable is found.
852 * Not called if there's no matching state variable.
853 * @param cb_cls Closure for the callbacks.
854 * @return Handle that can be used to cancel the query operation.
856 struct GNUNET_PSYC_StateQuery *
857 GNUNET_PSYC_channel_state_get (struct GNUNET_PSYC_Channel *channel,
858 const char *full_name,
859 GNUNET_PSYC_StateCallback cb,
864 * Return all channel state variables whose name matches a given prefix.
866 * A name matches if it starts with the given @a name_prefix, thus requesting
867 * the empty prefix ("") will match all values; requesting "_a_b" will also
868 * return values stored under "_a_b_c".
870 * The @a state_cb is invoked on all matching state variables asynchronously, as
871 * the state is stored in and retrieved from the PSYCstore,
873 * @param channel Channel handle.
874 * @param name_prefix Prefix of the state variable name to match.
875 * @param cb Function to call with the matching state variables.
876 * @param cb_cls Closure for the callbacks.
877 * @return Handle that can be used to cancel the query operation.
879 struct GNUNET_PSYC_StateQuery *
880 GNUNET_PSYC_channel_state_get_prefix (struct GNUNET_PSYC_Channel *channel,
881 const char *name_prefix,
882 GNUNET_PSYC_StateCallback cb,
887 * Cancel a state query operation.
889 * @param query Handle for the operation to cancel.
892 GNUNET_PSYC_channel_state_get_cancel (struct GNUNET_PSYC_StateQuery *query);
895 #if 0 /* keep Emacsens' auto-indent happy */
902 /* ifndef GNUNET_PSYC_SERVICE_H */
904 /* end of gnunet_psyc_service.h */