SNAX/HLS Application Programming Manual

RECEIVECONTROL Verb
Application Prototyping and Simulation (APS) System
6–38 104707 Tandem Computers Incorporated
RC:
RECEIVE-CONTROL
Verb (F4)
The RECEIVE-CONTROL request is intended as a nowait check of the user’s receive
queue. In other words, the RECEIVE-CONTROL verb causes SNAX/HLS to examine
the top element of the receive queue. If the receive queue is empty, the verb is
completed with RC-NO-DATA-AVAILABLE. If the receive queue is not empty, the
verb is completed just like a RECEIVE-DATA verb, except that messages are not
removed from the queue. All indicator fields are valid; for example, the user-data
length and the TIP (TRANSACTION-IN-PROGRESS) indicator are valid. The user-
data length returned from this verb could be used to allocate storage.
There are four basic formats for verb replies to RECEIVE-CONTROL:
1. A RECEIVE-CONTROL-REPLY structure if the top element on the receive queue
is a message. The message is not dequeued, nor is the text of the message
transferred to your program. A subsequent RECEIVE-DATA verb can be used to
retrieve and dequeue such messages.
2. A SEND-DATA-REPLY structure to deliver both positive and negative responses
from the session partner. See the SEND-DATA verb description for details.
3. Queued completions, noting the actual completion of a verb previously reported
as RC-FORTHCOMING. Consult the description of the individual verb reply for
details.
4. A RECEIVE-CONTROL-REPLY structure indicating RC-NO-DATA-AVAILABLE.
APS displays the appropriate reply screen automatically.