Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (R)
Guardian Procedure Calls Reference Manual—522629-013
13-61
REPLY[X] Procedures
•
Using the message-tag
If more than one message is queued by the application process (that is,
receive-
depth > 1), a message tag associated with each incoming message must be
obtained in a call to the FILE_GETRECEIVEINFO_ (or LASTRECEIVE or
RECEIVEINFO) procedure immediately following each call to READUPDATE[X].
To direct a reply back to the originator of the message, the message tag
associated with the incoming message returns to the system in the
message-tag
parameter to the REPLY[X] procedure. If messages are not queued (that is,
sync-or-receive-depth = 1), the message tag is not needed.
•
Error handling
The
error-return parameter can be used to return an error indication to the
requester in response to the open, CONTROL, SETMODE, and CONTROLBUF,
system messages. The error returns to the requester when the associated I/O
procedure finishes.
Considerations for REPLYX Only
•
The buffer and count written may be in the user stack segment or in an extended
data segment. They cannot be in the user’s code space.
•
If the buffer or count transferred is in a selectable extended data segment, the
segment must be in use at the time of the call. Flat segments allocated by a
process are always accessible to the process.
•
The transfer size is the same as for procedure REPLY.
•
If the extended address of the buffer is odd, bounds checking rounds the address
to the next lower word boundary and checks an extra byte. The odd address is
used for the transfer.
Errors for REPLYX Only
In addition to the errors currently returned from REPLY, error 22 is returned from
REPLYX in the following cases:
•
The address of a parameter is extended, but either the extended data segment is
invalid or the address is for a selectable segment that is not in use at the time of
the call.
•
The address of a parameter is extended, but it is an absolute address and the
caller is not privileged.
Example
CALL REPLY ( OUT^BUFFER , 512 );