event_bus.c File Reference

Implementation of the event bus. More...

#include "event_bus.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/queue.h"
#include "runtime_tasks.h"
#include "string.h"

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Data Structures
struct	subscriber_t
	Subscriber structure. More...

Macros
#define	EVENT_BUS_MAX_SUBSCRIBERS   (8U)
#define	EVENT_BUS_COUNT_BACKOFF_WATERMARK   (5U)

Functions
static void	event_bus_task (void *parameters_void_ptr)
	Event bus task.
static void	event_bus_stop_task (void)
	Stop event bus task.
esp_err_t	event_bus_init (size_t queue_size)
	Initialize event bus.
bool	event_bus_publish (const event_bus_t *event_ptr)
	Publish an event.
int8_t	event_bus_subscribe (event_bus_event_t type, event_bus_cb_t cb, void *ctx)
	Subscribe to event.
bool	event_bus_unsubscribe (int8_t slot)
	Unsubscribe from event.
void	event_bus_deinit (void)
	deinitialize event bus

Variables
static const char *	TAG = "EVENT_BUS"
static TaskHandle_t	event_bus_task_handle = NULL
static QueueHandle_t	event_queue
static subscriber_t	subscribers [(8U)]
runtime_task_config_t	event_bus_task_config

Detailed Description

Implementation of the event bus.

Author

Abanoub Salah

• Uses queues for publishers
• Starts a task for dispatching events to subscribers
• Subscribers can subscribe if slots are available which are limited
• Subscribers can unsubscribe using their slot ID provided during subscribing

Macro Definition Documentation

EVENT_BUS_COUNT_BACKOFF_WATERMARK

#define EVENT_BUS_COUNT_BACKOFF_WATERMARK   (5U)

Task backoff when queue reach watermark

EVENT_BUS_MAX_SUBSCRIBERS

#define EVENT_BUS_MAX_SUBSCRIBERS   (8U)

Maximum possible subscribers

Function Documentation

event_bus_init()

esp_err_t event_bus_init

(

size_t

queue_size

)

Initialize event bus.

Parameters

queue_size

Size of the event queue

Returns

esp_err_t Initialize result

Return values

ESP_OK	Initialize success
BLACKBOX_FAIL	Failed to create event task
ESP_ERR_INVALID_ARG	Provided invalid argument(s)
ESP_ERR_NO_MEM	No available memory for resource allocation

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event_bus_publish()

bool event_bus_publish

(

const event_bus_t *

event_ptr

)

Publish an event.

Publish an event by queue it to the event bus queue

Parameters

event_ptr

Pointer to an event

Returns

bool true on publish false otherwise

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event_bus_subscribe()

int8_t event_bus_subscribe	(	event_bus_event_t	type,
		event_bus_cb_t	cb,
		void *	ctx
	)

Subscribe to event.

Parameters

type	Event type
cb	Callback for when event happens
ctx	Context for the callback

Returns

int8_t Subscription slot number and '-1' On fail

< Maximum possible subscribers

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event_bus_task()

static void event_bus_task ( void *  parameters_void_ptr )

static

Event bus task.

Loops over subscribers calling them if their event match current one

Parameters

parameters_void_ptr

Void pointer to task parameters

< Maximum possible subscribers

< Task backoff when queue reach watermark

event_bus_unsubscribe()

bool event_bus_unsubscribe

(

int8_t

slot

)

Unsubscribe from event.

Parameters

slot	Subscription slot number

Returns

true on unsubscription false otherwise

< Maximum possible subscribers

Variable Documentation

event_bus_task_config

runtime_task_config_t event_bus_task_config

Initial value:

= {.name        = EVENT_BUS_TASK_NAME,
                                               .entry       = event_bus_task,
                                               .arg         = NULL,
                                               .stack_depth = EVENT_BUS_TASK_STACK_DEPTH,
                                               .priority    = EVENT_BUS_TASK_PRIORITY,
                                               .core_id     = EVENT_BUS_TASK_CPU_AFFINITY,
                                               .handle      = &event_bus_task_handle,
                                               .stop_func   = event_bus_stop_task}

Event bus task configuration structure

event_bus_task_handle

TaskHandle_t event_bus_task_handle = NULL

static

Event bus task handle

event_queue

QueueHandle_t event_queue

static

Event bus queue handle

subscribers

subscriber_t subscribers[(8U)]

static

Event bus subscribers list

TAG

const char* TAG = "EVENT_BUS"

static

Event bus TAG name