T-Kernel Specification (1.B0.02)

4.5. EXTENDED SYNCHRONIZATION AND COMMUNICATION FUNCTIONS 125
tk ref mbf
Get Message Buffer Status
[C Language Interface]
ER ercd = tk_ref_mbf ( ID mbfid, T_RMBF *pk_rmbf ) ;
[Parameters]
ID mbfid Message buffer ID
T RMBF* pk rmbf Address of packet for returning status information
[Return Parameters]
ER ercd Error code
pk rmbf detail:
VP exinf Extended information
ID wtsk Waiting task information
ID stsk Send task information
INT msgsz Size of the next message to be received (in bytes)
INT frbufsz Free buffer size (in bytes)
INT maxmsz Maximum message size (in bytes)
(Other implementation-dependent parameters may be added beyond this point.)
[Error Codes]
E OK
E ID
E NOEXS
E PAR
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 (the return parameter packet address cannot be used)
[Description]
References the status of the message buffer designated in mbfid, passing in the return parameters sending
task information (stsk), the size of the next message to be received (msgsz), free buffer size (frbufsz),
tmaximum message size (maxmsz), waiting task information (wtsk), and extended information (exinf).
wtsk indicates the ID of a task waiting for receipt from the message buffer. The ID of a task waiting
to send to the message buffer is indicated in stsk. If multiple tasks are waiting in the message buffer
queues, the ID of the task at the head of the queue is returned. If no tasks are waiting, 0 is returned.
If the designated message buffer does not exist, error code E NOEXS is returned.
The size of the message at the head of the queue (the next message to be received) is returned in msgsz.
If there are no queued messages, msgsz = 0 is returned. A message of size 0 cannot be sent. At least one
of msgsz = 0 and wtsk = 0 is always true for this system call. frbufsz indicates the free space in the
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T-Kernel 1.B0.02