rcv_dtq

Outline

Receive from data queue (waiting forever).

C format

 ER      rcv_dtq (ID dtqid, VP_INT *p_data);

Parameter(s)

I/O	Parameter	Description
I	ID dtqid;	ID number of the data queue from which a data element is received.
O	VP_INT *p_data;	Data element received from the data queue.

Explanation

This service call reads data in the data queue area of the data queue specified by parameter dtqid and stores it to the area specified by parameter p_data.

If no data could be read from the data queue area of the target data queue (no data has been written to the data queue area) when this service call is issued, the service call does not read data but queues the invoking task to the reception wait queue of the target data queue and moves it from the RUNNING state to the WAITING state (data reception wait state).

The receiving WAITING state for a data queue is cancelled in the following cases, and then moved to the READY state.

Receiving WAITING State for a Data Queue Cancel Operation	Return Value
Data was written to the data queue area of the target data queue as a result of issuing snd_dtq.	E_OK
Data was written to the data queue area of the target data queue as a result of issuing psnd_dtq.	E_OK
Data was written to the data queue area of the target data queue as a result of issuing ipsnd_dtq.	E_OK
Data was written to the data queue area of the target data queue as a result of issuing tsnd_dtq.	E_OK
Data was written to the data queue area of the target data queue as a result of issuing fsnd_dtq.	E_OK
Data was written to the data queue area of the target data queue as a result of issuing ifsnd_dtq.	E_OK
Forced release from waiting (accept rel_wai while waiting).	E_RLWAI
Forced release from waiting (accept irel_wai while waiting).	E_RLWAI

Note 1 Invoking tasks are queued to the reception wait queue of the target data queue in the order of the data reception request.

Note 2 If the receiving

Note 3 for a data queue is forcibly released by issuing rel_wai or irel_wai, the contents of the area specified by parameter p_data will be undefined.

Return value

Macro	Value	Description
E_OK	0	Normal completion.
E_ID	-18	Invalid ID number. - dtqid < 0x0 - dtqid > Maximum ID number
E_CTX	-25	Context error. - This service call was issued from a non-task. - This service call was issued in the CPU locked state. - This service call was issued in the dispatching disabled state.
E_NOEXS	-42	Non-existent object. - Specified data queue is not registered.
E_RLWAI	-49	Forced release from the WAITING state. - Accept rel_wai/irel_wai while waiting.