Informix DataBlade API Programmer's Manual DataBlade API Function Descriptions

The mi_register_callback() function registers a callback function for a single event type or for all event types.

MI_CALLBACK_HANDLE *mi_register_callback(conn, event_type, cback_func,

user_data, parent)

MI_CONNECTION *conn;

MI_EVENT_TYPE event_type;

MI_CALLBACK_FUNC cback_func;

void *user_data;

MI_CALLBACK_HANDLE *parent;

conn	is either NULL or the connection descriptor that a previous call to mi_open(), mi_server_connect(), or mi_server_reconnect() has established.
event_type	is the type of event that the cback_func callback handles. For a list of valid event types, see Figure 10-1 on page 10-4.
cback_func	is a pointer to the callback function.
user_data	is a pointer to a user-provided structure that is passed to the callback function when the event specified by event_type occurs. It can be used to pass additional information to the callback.
parent	must be a NULL-valued pointer.

Valid in Client LIBMI Application?	Valid in User-Defined Routine?
Yes	Yes

The mi_register_callback() function registers the callback that cback_func identifies for the event that event_type specifies. If event_type is MI_All_Events, the callback is registered for all events.

For a C UDR, conn must be NULL for the following event types:

• MI_EVENT_END_STMT
• MI_EVENT_END_XACT
• MI_EVENT_END_SESSION

For a client LIBMI application, you must provide a valid connection descriptor to mi_register_callback() to register callbacks for the following event types:

• MI_Exception
• MI_Xact_State_Change
• MI_Client_Library_Error

The callback is enabled when it is registered. You can explicitly disable the callback with the mi_disable_callback() function and reenable it with mi_enable_callback().

The mi_register_callback() function initializes the DataBlade API when it is the first DataBlade API function in a client LIBMI application or a C UDR. For more information, see Initializing the DataBlade API.

You can use the user_data parameter to specify the address of a user-defined error structure, which the callback can use to hold additional error information.

See the descriptions of the following functions: mi_disable_callback(), mi_enable_callback(), mi_retrieve_callback(), and mi_unregister_callback().

For more information, see Registering a Callback.