Guardian Procedure Calls Reference Manual

Considerations
• Nowait and CONTROLBUF
The CONTROLBUF procedure must complete with a call to the AWAITIO procedure when
used with a file opened nowait.
• Wait and count-transferred
If a waited CONTROLBUF is executed, the count-transferred parameter indicates the
number of bytes actually transferred.
• Nowait and count-transferred
If a nowait CONTROLBUF is executed, count-transferred has no meaning and can be
omitted. A count of the number of bytes transferred is obtained by the count-transferred
parameter of the AWAITIO procedure when the I/O finishes.
• When object of CONTROLBUF is not accepting messages
If the object of the CONTROLBUF operation is not accepting process CONTROLBUF messages,
the call to CONTROLBUF completes with condition code CCG. A subsequent call to
FILE_GETINFO_ or FILEINFO shows that an error 7 (process not accepting process CONTROL,
CONTROLBUF, or SETMODE messages) occurred.
You can obtain the process identifier of the caller to CONTROLBUF in a call to
FILE_GETRECEIVEINFO_ (or LASTRECEIVE or RECEIVEINFO) after you have read the process
CONTROLBUF message.
• Nonstandard operation and buffer parameters
You can specify any value for the operation parameter, and you can include any data in
buffer. An application-defined protocol should be established for interpreting nonstandard
parameter values.
Messages
• Process CONTROLBUF message
Issuing a CONTROLBUF to a file that represents another process causes a system message
-35 (process CONTROLBUF) to be sent to that process. For detailed information of system
messages sent to processes, see the Guardian Procedure Errors and Messages Manual.
214 Guardian Procedure Calls (C)