dat_evd_dequeue man page on SmartOS

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       dat_evd_dequeue	-  remove  the	first  event from the Event Dispatcher
       event queue

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

	   IN	 DAT_EVD_HANDLE	   evd_handle,
	   OUT	 DAT_EVENT	   *event

		     Handle for an instance of the Event Dispatcher.

		     Pointer to the Consumer-allocated structure that Provider
		     fills with the event data.

       The  dat_evd_dequeue()  function removes the first event from the Event
       Dispatcher event queue and fills the Consumer allocated event structure
       with  event data. The first element in this structure provides the type
       of the event; the rest provides the event-type-specific parameters. The
       Consumer	 should	 allocate  an  event  structure big enough to hold any
       event that the Event Dispatcher can deliver.

       For all events the Provider fills the dat_event that the Consumer allo‐
       cates. So for all events, all fields of dat_event are OUT from the Con‐
       sumer point of view.  For  DAT_CONNECTION_REQUEST_EVENT,	 the  Provider
       creates	a  Connection  Request whose cr_handle is returned to the Con‐
       sumer in DAT_CR_ARRIVAL_EVENT_DATA. That object	is  destroyed  by  the
       Provider	  as  part  of	dat_cr_accept(3DAT),  dat_cr_reject(3DAT),  or
       dat_cr_handoff(3DAT). The Consumer should not use cr_handle or  any  of
       its  parameters,	 including private_data, after one of these operations
       destroys the Connection Request.

       For DAT_CONNECTION_EVENT_ESTABLISHED for the Active side of  connection
       establishment,  the  Provider  returns the pointer for private_data and
       the   private_data_size.	  For	the    Passive	  side,	   DAT_CONNEC‐
       TION_EVENT_ESTABLISHED  event  private_data  is	not  defined  and pri‐
       vate_data_size returns zero. The Provider is responsible for the memory
       allocation and deallocation for private_data. The private_data is valid
       until  the  Active  side	 Consumer  destroys  the  connected   Endpoint
       (dat_ep_free(3DAT)), or transitions the Endpoint into Unconnected state
       so it is ready for the next connection. So while	 the  Endpoint	is  in
       Connected,  Disconnect Pending, or Disconnected state, the private_data
       of DAT_CONNECTION_REQUEST_EVENT is still valid  for  Active  side  Con‐

       Provider	 must  pass  to	 the Consumer the entire Private Data that the
       remote  Consumer	 provided  for	dat_ep_connect(3DAT),  dat_ep_dup_con‐
       nect(3DAT),  and	 dat_cr_accept().  If  the Consumer provides more data
       than the Provider and Transport can support (larger than	 IA  Attribute
       of  max_private_data_size),  DAT_INVALID_PARAMETER is returned for that

       The returned event that was posted from an Event Stream guarantees Con‐
       sumers  that  all  events  that	were posted from the same Event Stream
       prior to the  returned  event  were  already  returned  to  a  Consumer
       directly through a dat_evd_dequeue() or dat_evd_wait(3DAT) operation.

       The  ordering of events dequeued by overlapping calls to dat_evd_wait()
       or dat_evd_dequeue() is not specified.

			     The  operation  was  successful.  An  event   was
			     returned to a Consumer.

			     Invalid DAT handle; evd_handle is invalid.

			     There  are	 no  entries  on  the Event Dispatcher

			     One of the parameters was invalid for this opera‐
			     tion. There is already a waiter on the EVD.

       No  matter  how	many  contexts	attempt	 to dequeue from an Event Dis‐
       patcher, each event is delivered exactly once. However, which  Consumer
       receives	 which	event is not defined. The Provider is not obligated to
       provide the first caller the first event unless it is the only  caller.
       The  Provider  is not obligated to ensure that the caller receiving the
       first event executes earlier than contexts receiving later events.

       Preservation of event ordering within an Event Stream is	 an  important
       feature	of  the DAT Event Model. Consumers are cautioned that overlap‐
       ping or concurrent calls to dat_evd_dequeue()  from  multiple  contexts
       can  undermine  this  ordering information. After multiple contexts are
       involved, the Provider can only guarantee the order  that  it  delivers
       events  into  the EVD. The Provider cannot guarantee that they are pro‐
       cessed in the correct order.

       Although calling dat_evd_dequeue() does not cause a context switch, the
       Provider	 is  under  no obligation to prevent one. A context could suc‐
       cessfully complete a dequeue, and then reach the end of its  timeslice,
       before  returning  control  to  the Consumer code. Meanwhile, a context
       receiving a later event could be executing.

       The Event ordering is preserved when dequeueing is  serialized.	Poten‐
       tial  Consumer  serialization  methods include, but are not limited to,
       performing all dequeueing from a single context or protecting  dequeue‐
       ing by way of lock or semaphore.

       See attributes(5) for descriptions of the following attributes:

       │Interface Stability │ Standard: uDAPL, 1.1, 1.2 │
       │MT-Level	    │ Safe			│

       dat_cr_accept(3DAT),	dat_cr_handoff(3DAT),	  dat_cr_reject(3DAT),
       dat_ep_connect(3DAT),   dat_ep_dup_connect(3DAT),    dat_ep_free(3DAT),
       dat_evd_wait(3DAT)libdat(3LIB), attributes(5)

				 Jul 16, 2004		 DAT_EVD_DEQUEUE(3DAT)

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