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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
118 * PSYC channel policies.
120 enum GNUNET_PSYC_Policy
123 * Anyone can join the channel, without announcing his presence;
124 * all messages are always public and can be distributed freely.
125 * Joins may be announced, but this is not required.
127 GNUNET_PSYC_CHANNEL_ANONYMOUS = 0,
130 * The master must approve membership to the channel, messages must only be
131 * distributed to current channel slaves. This includes the channel
132 * state as well as transient messages.
134 GNUNET_PSYC_CHANNEL_PRIVATE
135 = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL
136 | GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY
140 * Anyone can freely join the channel (no approval required);
141 * however, messages must only be distributed to current channel
142 * slaves, so the master must still acknowledge that the slave
143 * joined before transient messages are delivered. As approval is
144 * guaranteed, the presistent channel state can be synchronized freely
145 * immediately, prior to master confirmation.
147 GNUNET_PSYC_CHANNEL_OPEN
148 = GNUNET_PSYC_CHANNEL_RESTRICTED_HISTORY,
151 * The master must approve joins to the channel, but past messages can be
152 * freely distributed to slaves.
154 GNUNET_PSYC_CHANNEL_CLOSED
155 = GNUNET_PSYC_CHANNEL_ADMISSION_CONTROL,
160 enum GNUNET_PSYC_MessageFlags
163 * Historic message, retrieved from PSYCstore.
165 GNUNET_PSYC_MESSAGE_HISTORIC = 1 << 0,
168 * Request from slave to master.
170 GNUNET_PSYC_MESSAGE_REQUEST = 1 << 1,
173 * Message can be delivered out of order.
175 GNUNET_PSYC_MESSAGE_ORDER_ANY = 1 << 2
180 * Values for the @a state_delta field of GNUNET_PSYC_MessageHeader.
182 enum GNUNET_PSYC_StateDeltaValues
184 GNUNET_PSYC_STATE_RESET = 0,
186 GNUNET_PSYC_STATE_NOT_MODIFIED = UINT64_MAX
190 GNUNET_NETWORK_STRUCT_BEGIN
193 * Header of a PSYC message.
195 * Only present when receiving a message.
197 struct GNUNET_PSYC_MessageHeader
200 * Generic message header with size and type information.
202 struct GNUNET_MessageHeader header;
205 * Flags for this message fragment.
207 * @see enum GNUNET_PSYC_MessageFlags
209 uint32_t flags GNUNET_PACKED;
212 * Number of the message this message part belongs to.
213 * Monotonically increasing from 1.
215 uint64_t message_id GNUNET_PACKED;
218 * Sending slave's public key.
219 * Not set if the message is from the master.
221 struct GNUNET_CRYPTO_EddsaPublicKey slave_key;
223 /* Followed by concatenated PSYC message parts:
224 * messages with GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_* types
230 * The method of a message.
232 struct GNUNET_PSYC_MessageMethod
235 * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
237 struct GNUNET_MessageHeader header;
240 * OR'ed GNUNET_PSYC_MasterTransmitFlags
242 uint32_t flags GNUNET_PACKED;
245 * Number of message IDs since the last message that contained state
246 * operations. @see enum GNUNET_PSYC_StateDeltaValues
248 uint64_t state_delta GNUNET_PACKED;
250 /* Followed by NUL-terminated method name. */
255 * A modifier of a message.
257 struct GNUNET_PSYC_MessageModifier
260 * Type: GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
262 struct GNUNET_MessageHeader header;
267 uint32_t value_size GNUNET_PACKED;
270 * Size of name, including NUL terminator.
272 uint16_t name_size GNUNET_PACKED;
275 * enum GNUNET_ENV_Operator
279 /* Followed by NUL-terminated name, then the value. */
282 GNUNET_NETWORK_STRUCT_END
285 #define GNUNET_PSYC_MODIFIER_MAX_PAYLOAD \
286 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
287 - sizeof (struct GNUNET_PSYC_MessageModifier)
289 #define GNUNET_PSYC_MOD_CONT_MAX_PAYLOAD \
290 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
291 - sizeof (struct GNUNET_MessageHeader)
293 #define GNUNET_PSYC_DATA_MAX_PAYLOAD \
294 GNUNET_MULTICAST_FRAGMENT_MAX_PAYLOAD \
295 - sizeof (struct GNUNET_MessageHeader)
299 * Handle that identifies a join request.
301 * Used to match calls to #GNUNET_PSYC_JoinCallback to the
302 * corresponding calls to GNUNET_PSYC_join_decision().
304 struct GNUNET_PSYC_JoinHandle;
308 * Method called from PSYC upon receiving part of a message.
310 * @param cls Closure.
311 * @param msg Message part, one of the following types:
312 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_HEADER
313 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_METHOD
314 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MODIFIER
315 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_MOD_CONT
316 * - GNUNET_MESSAGE_TYPE_PSYC_MESSAGE_DATA
319 (*GNUNET_PSYC_MessageCallback) (void *cls,
322 const struct GNUNET_MessageHeader *msg);
326 * Method called from PSYC upon receiving a join request.
328 * @param cls Closure.
329 * @param slave requesting to join.
330 * @param join_msg Join message sent along with the request.
331 * @param jh Join handle to use with GNUNET_PSYC_join_decision()
334 (*GNUNET_PSYC_JoinCallback) (void *cls,
335 const struct GNUNET_CRYPTO_EddsaPublicKey
337 const struct GNUNET_PSYC_MessageHeader *join_msg,
338 struct GNUNET_PSYC_JoinHandle *jh);
342 * Function to call with the decision made for a join request.
344 * Must be called once and only once in response to an invocation of the
345 * #GNUNET_PSYC_JoinCallback.
347 * @param jh Join request handle.
348 * @param is_admitted #GNUNET_YES if joining is approved,
349 * #GNUNET_NO if it is disapproved.
350 * @param relay_count Number of relays given.
351 * @param relays Array of suggested peers that might be useful relays to use
352 * when joining the multicast group (essentially a list of peers that
353 * are already part of the multicast group and might thus be willing
354 * to help with routing). If empty, only this local peer (which must
355 * be the multicast origin) is a good candidate for building the
356 * multicast tree. Note that it is unnecessary to specify our own
357 * peer identity in this array.
358 * @param method_name Method name for the message transmitted with the response.
359 * @param env Environment containing transient variables for the message,
361 * @param data Data of the message.
362 * @param data_size Size of @a data.
365 GNUNET_PSYC_join_decision (struct GNUNET_PSYC_JoinHandle *jh,
367 uint32_t relay_count,
368 const struct GNUNET_PeerIdentity *relays,
369 const char *method_name,
370 const struct GNUNET_ENV_Environment *env,
376 * Handle for the master of a PSYC channel.
378 struct GNUNET_PSYC_Master;
382 * Function called after the channel master started.
384 * @param cls Closure.
385 * @param max_message_id Last message ID sent to the channel.
388 (*GNUNET_PSYC_MasterStartCallback) (void *cls, uint64_t max_message_id);
392 * Start a PSYC master channel.
394 * Will start a multicast group identified by the given ECC key. Messages
395 * received from group members will be given to the respective handler methods.
396 * If a new member wants to join a group, the "join" method handler will be
397 * invoked; the join handler must then generate a "join" message to approve the
398 * joining of the new member. The channel can also change group membership
399 * without explicit requests. Note that PSYC doesn't itself "understand" join
400 * or part messages, the respective methods must call other PSYC functions to
401 * inform PSYC about the meaning of the respective events.
403 * @param cfg Configuration to use (to connect to PSYC service).
404 * @param channel_key ECC key that will be used to sign messages for this
405 * PSYC session. The public key is used to identify the PSYC channel.
406 * Note that end-users will usually not use the private key directly, but
407 * rather look it up in GNS for places managed by other users, or select
408 * a file with the private key(s) when setting up their own channels
409 * FIXME: we'll likely want to use NOT the p521 curve here, but a cheaper
411 * @param policy Channel policy specifying join and history restrictions.
412 * Used to automate join decisions.
413 * @param message_cb Function to invoke on message parts received from slaves.
414 * @param join_cb Function to invoke when a peer wants to join.
415 * @param master_started_cb Function to invoke after the channel master started.
416 * @param cls Closure for @a method and @a join_cb.
417 * @return Handle for the channel master, NULL on error.
419 struct GNUNET_PSYC_Master *
420 GNUNET_PSYC_master_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
421 const struct GNUNET_CRYPTO_EddsaPrivateKey *channel_key,
422 enum GNUNET_PSYC_Policy policy,
423 GNUNET_PSYC_MessageCallback message_cb,
424 GNUNET_PSYC_JoinCallback join_cb,
425 GNUNET_PSYC_MasterStartCallback master_started_cb,
430 * Function called to provide data for a transmission via PSYC.
432 * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
433 * invalidates the respective transmission handle.
435 * @param cls Closure.
436 * @param[in,out] data_size Initially set to the number of bytes available in
437 * @a data, should be set to the number of bytes written to data.
438 * @param[out] data Where to write the body of the message to give to the
439 * method. The function must copy at most @a data_size bytes to @a data.
440 * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
441 * #GNUNET_NO on success, if more data is to be transmitted later.
442 * Should be used if @a data_size was not big enough to take all the
443 * data. If 0 is returned in @a data_size the transmission is paused,
444 * and can be resumed with GNUNET_PSYC_master_transmit_resume().
445 * #GNUNET_YES if this completes the transmission (all data supplied)
448 (*GNUNET_PSYC_TransmitNotifyData) (void *cls,
453 * Function called to provide a modifier for a transmission via PSYC.
455 * Note that returning #GNUNET_YES or #GNUNET_SYSERR (but not #GNUNET_NO)
456 * invalidates the respective transmission handle.
458 * @param cls Closure.
459 * @param[in,out] data_size Initially set to the number of bytes available in
460 * @a data, should be set to the number of bytes written to data.
461 * @param[out] data Where to write the modifier's name and value.
462 * The function must copy at most @a data_size bytes to @a data.
463 * When this callback is first called for a modifier, @a data should
464 * contain: "name\0value". If the whole value does not fit, subsequent
465 * calls to this function should write continuations of the value to
467 * @param[out] oper Where to write the operator of the modifier.
468 * Only needed during the first call to this callback at the beginning
469 * of the modifier. In case of subsequent calls asking for value
470 * continuations @a oper is set to #NULL.
471 * @param[out] value_size Where to write the full size of the value.
472 * Only needed during the first call to this callback at the beginning
473 * of the modifier. In case of subsequent calls asking for value
474 * continuations @a value_size is set to #NULL.
475 * @return #GNUNET_SYSERR on error (fatal, aborts transmission)
476 * #GNUNET_NO on success, if more data is to be transmitted later.
477 * Should be used if @a data_size was not big enough to take all the
478 * data for the modifier's value (the name must be always returned
479 * during the first call to this callback).
480 * If 0 is returned in @a data_size the transmission is paused,
481 * and can be resumed with GNUNET_PSYC_master_transmit_resume().
482 * #GNUNET_YES if this completes the modifier (the whole value is supplied).
485 (*GNUNET_PSYC_TransmitNotifyModifier) (void *cls,
489 uint32_t *value_size);
492 * Flags for transmitting messages to a channel by the master.
494 enum GNUNET_PSYC_MasterTransmitFlags
496 GNUNET_PSYC_MASTER_TRANSMIT_NONE = 0,
499 * Whether this message should reset the channel state,
500 * i.e. remove all previously stored state variables.
503 GNUNET_PSYC_MASTER_TRANSMIT_STATE_RESET = 1 << 0,
506 * Whether this message contains any state modifiers.
508 GNUNET_PSYC_MASTER_TRANSMIT_STATE_MODIFY = 1 << 1,
511 * Add PSYC header variable with the hash of the current channel state.
513 GNUNET_PSYC_MASTER_TRANSMIT_STATE_HASH = 1 << 2,
516 * Whether we need to increment the group generation counter after
517 * transmitting this message.
519 GNUNET_PSYC_MASTER_TRANSMIT_INC_GROUP_GEN = 1 << 3
524 * Handle for a pending PSYC transmission operation.
526 struct GNUNET_PSYC_MasterTransmitHandle;
530 * Send a message to call a method to all members in the PSYC channel.
532 * @param master Handle to the PSYC channel.
533 * @param method_name Which method should be invoked.
534 * @param notify_mod Function to call to obtain modifiers.
535 * @param notify_data Function to call to obtain fragments of the data.
536 * @param notify_cls Closure for @a notify_mod and @a notify_data.
537 * @param flags Flags for the message being transmitted.
538 * @return Transmission handle, NULL on error (i.e. more than one request queued).
540 struct GNUNET_PSYC_MasterTransmitHandle *
541 GNUNET_PSYC_master_transmit (struct GNUNET_PSYC_Master *master,
542 const char *method_name,
543 GNUNET_PSYC_TransmitNotifyModifier notify_mod,
544 GNUNET_PSYC_TransmitNotifyData notify_data,
546 enum GNUNET_PSYC_MasterTransmitFlags flags);
550 * Resume transmission to the channel.
552 * @param th Handle of the request that is being resumed.
555 GNUNET_PSYC_master_transmit_resume (struct GNUNET_PSYC_MasterTransmitHandle *th);
559 * Abort transmission request to channel.
561 * @param th Handle of the request that is being aborted.
564 GNUNET_PSYC_master_transmit_cancel (struct GNUNET_PSYC_MasterTransmitHandle *th);
568 * Stop a PSYC master channel.
570 * @param master PSYC channel master to stop.
573 GNUNET_PSYC_master_stop (struct GNUNET_PSYC_Master *master);
577 * Handle for a PSYC channel slave.
579 struct GNUNET_PSYC_Slave;
583 * Function called after the slave joined.
585 * @param cls Closure.
586 * @param max_message_id Last message ID sent to the channel.
589 (*GNUNET_PSYC_SlaveJoinCallback) (void *cls, uint64_t max_message_id);
593 * Join a PSYC channel.
595 * The entity joining is always the local peer. The user must immediately use
596 * the GNUNET_PSYC_slave_transmit() functions to transmit a @e join_msg to the
597 * channel; if the join request succeeds, the channel state (and @e recent
598 * method calls) will be replayed to the joining member. There is no explicit
599 * notification on failure (as the channel may simply take days to approve,
600 * and disapproval is simply being ignored).
602 * @param cfg Configuration to use.
603 * @param channel_key ECC public key that identifies the channel we wish to join.
604 * @param slave_key ECC private-public key pair that identifies the slave, and
605 * used by multicast to sign the join request and subsequent unicast
606 * requests sent to the master.
607 * @param origin Peer identity of the origin.
608 * @param relay_count Number of peers in the @a relays array.
609 * @param relays Peer identities of members of the multicast group, which serve
610 * as relays and used to join the group at.
611 * @param message_cb Function to invoke on message parts received from the
612 * channel, typically at least contains method handlers for @e join and
614 * @param slave_joined_cb Function invoked once we have joined the channel.
615 * @param cls Closure for @a message_cb and @a slave_joined_cb.
616 * @param method_name Method name for the join request.
617 * @param env Environment containing transient variables for the request, or NULL.
618 * @param data Payload for the join message.
619 * @param data_size Number of bytes in @a data.
620 * @return Handle for the slave, NULL on error.
622 struct GNUNET_PSYC_Slave *
623 GNUNET_PSYC_slave_join (const struct GNUNET_CONFIGURATION_Handle *cfg,
624 const struct GNUNET_CRYPTO_EddsaPublicKey *channel_key,
625 const struct GNUNET_CRYPTO_EddsaPrivateKey *slave_key,
626 const struct GNUNET_PeerIdentity *origin,
627 uint32_t relay_count,
628 const struct GNUNET_PeerIdentity *relays,
629 GNUNET_PSYC_MessageCallback message_cb,
630 GNUNET_PSYC_SlaveJoinCallback slave_joined_cb,
632 const char *method_name,
633 const struct GNUNET_ENV_Environment *env,
639 * Part a PSYC channel.
641 * Will terminate the connection to the PSYC service. Polite clients should
642 * first explicitly send a part request (via GNUNET_PSYC_slave_transmit()).
644 * @param slave Slave handle.
647 GNUNET_PSYC_slave_part (struct GNUNET_PSYC_Slave *slave);
651 * Flags for transmitting messages to the channel master by a slave.
653 enum GNUNET_PSYC_SlaveTransmitFlags
655 GNUNET_PSYC_SLAVE_TRANSMIT_NONE = 0
660 * Handle for a pending PSYC transmission operation.
662 struct GNUNET_PSYC_SlaveTransmitHandle;
666 * Request a message to be sent to the channel master.
668 * @param slave Slave handle.
669 * @param method_name Which (PSYC) method should be invoked (on host).
670 * @param notify_mod Function to call to obtain modifiers.
671 * @param notify_data Function to call to obtain fragments of the data.
672 * @param notify_cls Closure for @a notify.
673 * @param flags Flags for the message being transmitted.
674 * @return Transmission handle, NULL on error (i.e. more than one request queued).
676 struct GNUNET_PSYC_SlaveTransmitHandle *
677 GNUNET_PSYC_slave_transmit (struct GNUNET_PSYC_Slave *slave,
678 const char *method_name,
679 GNUNET_PSYC_TransmitNotifyModifier notify_mod,
680 GNUNET_PSYC_TransmitNotifyData notify_data,
682 enum GNUNET_PSYC_SlaveTransmitFlags flags);
686 * Resume transmission to the master.
688 * @param th Handle of the request that is being resumed.
691 GNUNET_PSYC_slave_transmit_resume (struct GNUNET_PSYC_SlaveTransmitHandle *th);
695 * Abort transmission request to master.
697 * @param th Handle of the request that is being aborted.
700 GNUNET_PSYC_slave_transmit_cancel (struct GNUNET_PSYC_SlaveTransmitHandle *th);
704 * Handle to access PSYC channel operations for both the master and slaves.
706 struct GNUNET_PSYC_Channel;
710 * Convert a channel @a master to a @e channel handle to access the @e channel
713 * @param master Channel master handle.
714 * @return Channel handle, valid for as long as @a master is valid.
716 struct GNUNET_PSYC_Channel *
717 GNUNET_PSYC_master_get_channel (struct GNUNET_PSYC_Master *master);
721 * Convert @a slave to a @e channel handle to access the @e channel APIs.
723 * @param slave Slave handle.
724 * @return Channel handle, valid for as long as @a slave is valid.
726 struct GNUNET_PSYC_Channel *
727 GNUNET_PSYC_slave_get_channel (struct GNUNET_PSYC_Slave *slave);
731 * Add a slave to the channel's membership list.
733 * Note that this will NOT generate any PSYC traffic, it will merely update the
734 * local database to modify how we react to <em>membership test</em> queries.
735 * The channel master still needs to explicitly transmit a @e join message to
736 * notify other channel members and they then also must still call this function
737 * in their respective methods handling the @e join message. This way, how @e
738 * join and @e part operations are exactly implemented is still up to the
739 * application; for example, there might be a @e part_all method to kick out
742 * Note that channel slaves are explicitly trusted to execute such methods
743 * correctly; not doing so correctly will result in either denying other slaves
744 * access or offering access to channel data to non-members.
746 * @param channel Channel handle.
747 * @param slave_key Identity of channel slave to add.
748 * @param announced_at ID of the message that announced the membership change.
749 * @param effective_since Addition of slave is in effect since this message ID.
752 GNUNET_PSYC_channel_slave_add (struct GNUNET_PSYC_Channel *channel,
753 const struct GNUNET_CRYPTO_EddsaPublicKey *slave_key,
754 uint64_t announced_at,
755 uint64_t effective_since);
759 * Remove a slave from the channel's membership list.
761 * Note that this will NOT generate any PSYC traffic, it will merely update the
762 * local database to modify how we react to <em>membership test</em> queries.
763 * The channel master still needs to explicitly transmit a @e part message to
764 * notify other channel members and they then also must still call this function
765 * in their respective methods handling the @e part message. This way, how
766 * @e join and @e part operations are exactly implemented is still up to the
767 * application; for example, there might be a @e part_all message to kick out
770 * Note that channel members are explicitly trusted to perform these
771 * operations correctly; not doing so correctly will result in either
772 * denying members access or offering access to channel data to
775 * @param channel Channel handle.
776 * @param slave_key Identity of channel slave to remove.
777 * @param announced_at ID of the message that announced the membership change.
780 GNUNET_PSYC_channel_slave_remove (struct GNUNET_PSYC_Channel *channel,
781 const struct GNUNET_CRYPTO_EddsaPublicKey
783 uint64_t announced_at);
787 * Function called to inform a member about stored state values for a channel.
789 * @param cls Closure.
790 * @param name Name of the state variable. A NULL value indicates that there
791 * are no more state variables to be returned.
792 * @param value Value of the state variable.
793 * @param value_size Number of bytes in @a value.
796 (*GNUNET_PSYC_StateCallback) (void *cls,
803 * Function called when a requested operation has finished.
805 * @param cls Closure.
808 (*GNUNET_PSYC_FinishCallback) (void *cls);
812 * Handle to a story telling operation.
814 struct GNUNET_PSYC_Story;
818 * Request to be told the message history of the channel.
820 * Historic messages (but NOT the state at the time) will be replayed (given to
821 * the normal method handlers) if available and if access is permitted.
823 * To get the latest message, use 0 for both the start and end message ID.
825 * @param channel Which channel should be replayed?
826 * @param start_message_id Earliest interesting point in history.
827 * @param end_message_id Last (exclusive) interesting point in history.
828 * @param message_cb Function to invoke on message parts received from the story.
829 * @param finish_cb Function to call when the requested story has been fully
830 * told (counting message IDs might not suffice, as some messages
831 * might be secret and thus the listener would not know the story is
832 * finished without being told explicitly); once this function
833 * has been called, the client must not call
834 * GNUNET_PSYC_channel_story_tell_cancel() anymore.
835 * @param cls Closure for the callbacks.
836 * @return Handle to cancel story telling operation.
838 struct GNUNET_PSYC_Story *
839 GNUNET_PSYC_channel_story_tell (struct GNUNET_PSYC_Channel *channel,
840 uint64_t start_message_id,
841 uint64_t end_message_id,
842 GNUNET_PSYC_MessageCallback message_cb,
843 GNUNET_PSYC_FinishCallback finish_cb,
848 * Abort story telling.
850 * This function must not be called from within method handlers (as given to
851 * GNUNET_PSYC_slave_join()) of the slave.
853 * @param story Story telling operation to stop.
856 GNUNET_PSYC_channel_story_tell_cancel (struct GNUNET_PSYC_Story *story);
860 * Handle for a state query operation.
862 struct GNUNET_PSYC_StateQuery;
866 * Retrieve the best matching channel state variable.
868 * If the requested variable name is not present in the state, the nearest
869 * less-specific name is matched; for example, requesting "_a_b" will match "_a"
870 * if "_a_b" does not exist.
872 * @param channel Channel handle.
873 * @param full_name Full name of the requested variable, the actual variable
874 * returned might have a shorter name..
875 * @param cb Function called once when a matching state variable is found.
876 * Not called if there's no matching state variable.
877 * @param cb_cls Closure for the callbacks.
878 * @return Handle that can be used to cancel the query operation.
880 struct GNUNET_PSYC_StateQuery *
881 GNUNET_PSYC_channel_state_get (struct GNUNET_PSYC_Channel *channel,
882 const char *full_name,
883 GNUNET_PSYC_StateCallback cb,
888 * Return all channel state variables whose name matches a given prefix.
890 * A name matches if it starts with the given @a name_prefix, thus requesting
891 * the empty prefix ("") will match all values; requesting "_a_b" will also
892 * return values stored under "_a_b_c".
894 * The @a state_cb is invoked on all matching state variables asynchronously, as
895 * the state is stored in and retrieved from the PSYCstore,
897 * @param channel Channel handle.
898 * @param name_prefix Prefix of the state variable name to match.
899 * @param cb Function to call with the matching state variables.
900 * @param cb_cls Closure for the callbacks.
901 * @return Handle that can be used to cancel the query operation.
903 struct GNUNET_PSYC_StateQuery *
904 GNUNET_PSYC_channel_state_get_prefix (struct GNUNET_PSYC_Channel *channel,
905 const char *name_prefix,
906 GNUNET_PSYC_StateCallback cb,
911 * Cancel a state query operation.
913 * @param query Handle for the operation to cancel.
916 GNUNET_PSYC_channel_state_get_cancel (struct GNUNET_PSYC_StateQuery *query);
919 #if 0 /* keep Emacsens' auto-indent happy */
926 /* ifndef GNUNET_PSYC_SERVICE_H */
928 /* end of gnunet_psyc_service.h */