T-Kernel Specification (1.B0.02)

4.5. EXTENDED SYNCHRONIZATION AND COMMUNICATION FUNCTIONS 123
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 designation
[Return Parameters]
INT msgsz Received message size
or Error Code
[Error Codes]
E OK
E ID
E NOEXS
E PAR
E DLT
E RLWAI
E DISWAI
E TMOUT
E CTX
Normal completion
Invalid ID number (mbfid is invalid or cannot be used)
Object does not exist (the message buffer designated in mbfid does not exist)
Parameter error (value that cannot be used in msg, or tmout ≤ (−2))
The object being waited for was deleted (message buffer was deleted while waiting)
Wait state released (tk rel wai received in wait state)
Wait released by wait disabled state
Polling failed or timeout
Context error (issued from task-independent portion or in dispatch disabled state)
[Description]
Receives a message from the message buffer designated in mbfid, putting it in the location designated
in msg.
This system call copies the contents of the first queued message in the message buffer designated in
mbfid, and copies it to an area of msgsz bytes starting at address msg.
If no message has been sent to the message buffer designated 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).
Copyright c○ 2002, 2003 by T-Engine Forum
T-Kernel 1.B0.02