cc [ flag.\|.\|. ] file.\|.\|. -ldat [ library.\|.\|. ]
#include <dat/udat.h>

DAT_RETURN
 dat_ia_open (
 IN const DAT_NAME_PTR ia_name_ptr,
 IN DAT_COUNT async_evd_min_qlen,
 INOUT DAT_EVD_HANDLE *async_evd_handle,
 OUT DAT_IA_HANDLE *ia_handle
 )

The dat_ia_open() function opens an IA by creating an IA instance. Multiple instances (opens) of an IA can exist.

The value of DAT_HANDLE_NULL for async_evd_handle (*async_evd_handle == DAT_HANDLE_NULL) indicates that the default Event Dispatcher is created with the requested async_evd_min_qlen. The async_evd_handle returns the handle of the created Asynchronous Event Dispatcher. The first Consumer that opens an IA must use DAT_HANDLE_NULL because no EVD can yet exist for the requested ia_name_ptr.

The Asynchronous Event Dispatcher (async_evd_handle) is created with no CNO (DAT_HANDLE_NULL). Consumers can change these values using dat_evd_modify_cno(3DAT). The Consumer can modify parameters of the Event Dispatcher using dat_evd_resize(3DAT) and dat_evd_modify_cno().

The Provider is required to provide a queue size at least equal to async_evd_min_qlen, but is free to provide a larger queue size or dynamically enlarge the queue when needed. The Consumer can determine the actual queue size by querying the created Event Dispatcher instance.

If async_evd_handle is not DAT_HANDLE_NULL, the Provider does not create an Event Dispatcher for an asynchronous event and the Provider ignores the async_evd_min_qlen value. The async_evd_handle value passed in by the Consumer must be an asynchronous Event Dispatcher created for the same Provider (ia_name_ptr). The Provider does not have to check for the validity of the Consumer passed in async_evd_handle. It is the Consumer responsibility to guarantee that async_evd_handle is valid and for this Provider. How the async_evd_handle is passed between DAT Consumers is out of scope of the DAT specification. If the Provider determines that the Consumer-provided async_evd_handle is invalid, the operation fails and returns DAT_INVALID_HANDLE. The async_evd_handle remains unchanged, so the returned async_evd_handle is the same the Consumer passed in. All asynchronous notifications for the open instance of the IA are directed by the Provider to the Consumer passed in Asynchronous Event Dispatcher specified by async_evd_handle.

Consumer can specify the value of DAT_EVD_ASYNC_EXISTS to indicate that there exists an event dispatcher somewhere else on the host, in user or kernel space, for asynchronous event notifications. It is up to the Consumer to ensure that this event dispatcher is unique and unambiguous. A special handle may be returned for the Asynchronous Event Dispatcher for this scenario, DAT_EVD_OUT_OF_SCOPE, to indicate that there is a default Event Dispatcher assigned for this Interface Adapter, but that it is not in a scope where this Consumer may directly invoke it.

The Asynchronous Event Dispatcher is an Object of both the Provider and IA. Each Asynchronous Event Dispatcher bound to an IA instance is notified of all asynchronous events, such that binding multiple Asynchronous Event Dispatchers degrades performance by duplicating asynchronous event notifications for all Asynchronous Event Dispatchers. Also, transport and memory resources can be consumed per Event Dispatcher bound to an IA

As with all Event Dispatchers, the Consumer is responsible for synchronizing access to the event queue.

Valid IA names are obtained from dat_registry_list_providers(3DAT).

The dat_ia_open() function is the root method for the Provider, and, thus, all Objects. It is the root handle through which the Consumer obtains all other DAT handles. When the Consumer closes its handle, all its DAT Objects are released.

The dat_ia_open() function is the workhorse method that provides an IA instance. It can also initialize the Provider library or do any other registry-specific functions.

The dat_ia_open() function creates a unique handle for the IA to the Consumer. All further DAT Objects created for this Consumer reference this handle as their owner.

The dat_ia_open() function can use a reference count for the Provider Library to ensure that the Provider Library cannot be removed when it is in use by a DAT Consumer.

See attributes(7) for descriptions of the following attributes:

dat_evd_modify_cno (3DAT), dat_evd_resize (3DAT), dat_ia_close (3DAT), dat_registry_list_providers (3DAT), libdat (3LIB), attributes (7)