Function esp_idf_sys::esp_event_handler_instance_register_with

pub unsafe extern "C" fn esp_event_handler_instance_register_with(
    event_loop: esp_event_loop_handle_t,
    event_base: esp_event_base_t,
    event_id: i32,
    event_handler: esp_event_handler_t,
    event_handler_arg: *mut c_void,
    instance: *mut esp_event_handler_instance_t
) -> esp_err_t

@brief Register an instance of event handler to a specific loop.

This function can be used to register a handler for either: (1) specific events, (2) all events of a certain event base, or (3) all events known by the system event loop.

• specific events: specify exact event_base and event_id
• all events of a certain base: specify exact event_base and use ESP_EVENT_ANY_ID as the event_id
• all events known by the loop: use ESP_EVENT_ANY_BASE for event_base and ESP_EVENT_ANY_ID as the event_id

Besides the error, the function returns an instance object as output parameter to identify each registration. This is necessary to remove (unregister) the registration before the event loop is deleted.

Registering multiple handlers to events, registering a single handler to multiple events as well as registering the same handler to the same event multiple times is possible. Each registration yields a distinct instance object which identifies it over the registration lifetime.

@param[in] event_loop the event loop to register this handler function to, must not be NULL @param[in] event_base the base ID of the event to register the handler for @param[in] event_id the ID of the event to register the handler for @param[in] event_handler the handler function which gets called when the event is dispatched @param[in] event_handler_arg data, aside from event data, that is passed to the handler when it is called @param[out] instance An event handler instance object related to the registered event handler and data, can be NULL. This needs to be kept if the specific callback instance should be unregistered before deleting the whole event loop. Registering the same event handler multiple times is possible and yields distinct instance objects. The data can be the same for all registrations. If no unregistration is needed, but the handler should be deleted when the event loop is deleted, instance can be NULL.

@note the event loop library does not maintain a copy of event_handler_arg, therefore the user should ensure that event_handler_arg still points to a valid location by the time the handler gets called

@return

• ESP_OK: Success
• ESP_ERR_NO_MEM: Cannot allocate memory for the handler
• ESP_ERR_INVALID_ARG: Invalid combination of event base and event ID or instance is NULL
• Others: Fail