tk_rcv_mbf

Receive Message from Message Buffer

[C Language Interface]

INT msgsz = tk_rcv_mbf ( ID mbfid, VP msg, TMO tmout ) ;
[Parameters]

ID	mbfid	 Message buffer ID


VP	msg	Start address of receive message packet


TMO	tmout	timeout
[Return Parameters]

INT	msgsz	Received message size


	or	Error Code
[Error Codes]

E_OK	Normal completion


E_ID	Invalid ID number (mbfid is invalid or cannot be used)


E_NOEXS	Object does not exist (the message buffer specified in mbfid does not exist)


E_PAR	Parameter error (value in msg cannot be used, or tmout <= (-2))


E_DLT	The object being waited for was deleted (message buffer was deleted while waiting)


E_RLWAI	Wait state released (tk_rel_wai received in wait state)


E_TMOUT	Polling failed or timeout


E_CTX	Context error (issued from task-independent portion or in dispatch disabled state)
[Description]

Receives a message from the message buffer specified in mbfid, putting it in the location specified in msg.

This system call copies the contents of the first queued message in the message buffer specified in mbfid, and copies it to an area of @@msg@sz@ bytes starting at address msg.

If no message has been sent to the message buffer specified in mbfid (the message queue is empty), the task issuing this system call goes to WAIT state and is put in the receive queue of the message buffer to wait for message arrival. Tasks in the receive queue are ordered by FIFO only.

A maximum wait time (timeout) can be set in tmout. If the tmout time elapses before the wait release condition is met (before a message arrives), the system call terminates, returning timeout error code E_TMOUT.

Only positive values can be set in tmout. The time base for tmout (time unit) is the same as that for system time (= 1 ms).

When TMO_POL = 0 is set in tmout, this means 0 was specified as the timeout value, and E_TMOUT is returned without entering WAIT state even if there is no message.

When TMO_FEVR =(-1) is set in tmout, this means infinity was specified as the timeout value, and the task continues to wait for message arrival without timing out.

[Difference with T-Kernel]

E_DISWAI does not exist in error codes. This is because in µT-Kernel, there is no wait disabled function.

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