Announcements

The Announcement primitive does local area announcements.

An announcement is an (ID, value) tuple that is disseminated to local area neighbors. An application or protocol can explicitly listen to announcements from neighbors. When an announcement is heard, a callback is invoked.

Announcements can be used for a variety of network mechanisms such as neighbor discovery, node-level service discovery, or routing metric dissemination.

Application programs and protocols register announcements with the announcement module. An announcement back-end, implemented by the system, takes care of sending out announcements over the radio, as well as collecting announcements heard from neighbors.

Data Structures
struct	announcement
	Representation of an announcement. More...

Files
file	announcement.h
	Header file for the announcement primitive

Typedefs
typedef void(*	announcement_callback_t )(struct announcement *a, const linkaddr_t *from, uint16_t id, uint16_t val)

Application API
void	announcement_register (struct announcement *a, uint16_t id, announcement_callback_t callback)
	Register an announcement. More...
void	announcement_remove (struct announcement *a)
	Remove a previously registered announcement. More...
void	announcement_set_value (struct announcement *a, uint16_t value)
	Set the value of an announcement. More...
void	announcement_remove_value (struct announcement *a)
	Remove the value of an announcement. More...
void	announcement_bump (struct announcement *a)
	Bump an announcement. More...
void	announcement_listen (int periods)
	Listen for announcements for a specific amount of announcement periods. More...

System API
enum	{   ANNOUNCEMENT_NOBUMP,   ANNOUNCEMENT_BUMP }
typedef void(*	announcement_observer )(uint16_t id, uint8_t has_value, uint16_t newvalue, uint16_t oldvalue, uint8_t bump)
void	announcement_init (void)
	Initialize the announcement module. More...
struct announcement *	announcement_list (void)
	Get the list of registered announcements. More...
void	announcement_heard (const linkaddr_t *from, uint16_t id, uint16_t value)
	Inform the announcement module of an incoming announcement. More...
void	announcement_register_listen_callback (void(*callback)(int time))
	Register a listen callback with the announcement module. More...
void	announcement_register_observer_callback (announcement_observer observer)
	Register an observer callback with the announcement module. More...

typedef void(* announcement_callback_t)(struct announcement *a, const linkaddr_t *from, uint16_t id, uint16_t val)

typedef void(* announcement_observer)(uint16_t id, uint8_t has_value, uint16_t newvalue, uint16_t oldvalue, uint8_t bump)

anonymous enum

Enumerator
ANNOUNCEMENT_NOBUMP
ANNOUNCEMENT_BUMP

void announcement_bump

(

struct announcement *

a

)

Bump an announcement.

Parameters

a	A pointer to a struct announcement that has previously been registered

This function is called to inform the announcement module that a particular announcement has changed in a way that it should be bumped. When an announcement is bumped, the announcement back-end may send out a new announcement to neighbors.

void announcement_heard	(	const linkaddr_t *	from,
		uint16_t	id,
		uint16_t	value
	)

Inform the announcement module of an incoming announcement.

Parameters

from	The address of the sender of the announcement
id	The identifier of the announcement
value	The value of the announcement This function is called by the back-end to inform the announcement module that an announcement from a neighbor has been heard.

void announcement_init

(

void

)

Initialize the announcement module.

This function initializes the announcement module, and is called by the system at boot up.

struct announcement* announcement_list

(

void

)

Get the list of registered announcements.

Returns

The list of registered announcements

        This function returns the list of registered
        announcements. This function is used by the back-end to
        compile announcement packets from the registered
        announcements.

        The announcement list is an ordinary Contiki list, as
        defined by the \ref list "list module".

void announcement_listen

(

int

periods

)

Listen for announcements for a specific amount of announcement periods.

Parameters

periods

The number of periods to listen for announcement This function starts to listen for announcements for the specified amount of announcement periods. This function is called to ensure that the announcement module hears announcements from neighbors. The announcement module may hear announcements even if listening is not explicitly enabled, but with listening enabled, more announcements will be heard.

void announcement_register	(	struct announcement *	a,
		uint16_t	id,
		announcement_callback_t	callback
	)

Register an announcement.

Parameters

a	A pointer to a struct announcement
id	The identifying number of the announcement
callback	A pointer to a callback function that is called when an announcement is heard

This function registers an announcement with the announcement module. The state of the announcement is held in a struct announcement variable, which is passed as an argument to this function. This variable must be allocated by the caller. An announcement is identified with a 16-bit number, which is passed as a parameter to the function. The announcement also has an initial value, that can later be changed with announcement_set_value().

void announcement_register_listen_callback

(

void(*)(int time)

callback

)

Register a listen callback with the announcement module.

Parameters

callback

A pointer to a callback function This function is called by the back-end to register a listen callback with the announcement module. The listen callback function is called by the announcement module as part of the announcement_listen() function.

void announcement_register_observer_callback

(

announcement_observer

observer

)

Register an observer callback with the announcement module.

Parameters

observer

A pointer to an observer function This function is callback by the back-end to register an observer callback with the announcement module. The observer callback is called by the announcement module when an announcement is registered, removed, or have its identifier or value updated. The back-end may chose to send out a new announcement message with the updated values.

void announcement_remove

(

struct announcement *

a

)

Remove a previously registered announcement.

Parameters

a	A pointer to a struct announcement that has previously been registered

This function removes an announcement that has previously been registered with announcement_register().

void announcement_remove_value

(

struct announcement *

a

)

Remove the value of an announcement.

Parameters

a	A pointer to a struct announcement that has previously been registered

This function removes the value of an announcement that has previously been registered with announcement_register().

void announcement_set_value	(	struct announcement *	a,
		uint16_t	value
	)

Set the value of an announcement.

Parameters

a	A pointer to a struct announcement that has previously been registered

This function sets the value of an announcement that has previously been registered with announcement_register().