SNAX/HLS Application Programming Manual

RECEIVE-CONTROL Verb
SNAX/HLS Verbs
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RECEIVE-CONTROL
Verb
RECEIVE–CONTROL is mainly intended for a nowait check of the user receive queue.
It permits your application to check for the presence of data on the receive queue.
Responses to previously sent data and queued completions are be removed from your
receive queue. That is, when SNAX/HLS performs a RECEIVE–CONTROL verb, the
top element of the receive queue for the session ID is inspected. If it records anything
other than a data message, then the verb completion also removes the entry from the
session’s receive queue. Data messages can be removed from the session’s receive
queue only in reply to RECEIVE–DATA or SEND–AND–RECEIVE–DATA verbs.
The verb code of the reply indicates the action taken by SNAX/HLS in response to the
RECEIVE–CONTROL verb:
If the top element is a data message SNAX/HLS replies with the
RECEIVE–CONTROL–REPLY format and a return code of RC–OK. Note that all
indicators on the reply format are set to valid states, except that no data is
presented. In this context, a data message is anything that would produce a
RECEIVE–DATA response to a RECEIVE–DATA verb.
In particular, the RECEIVE–DATA–QUEUED indicator contains Y, and the user
can determine the length of the data that is awaiting delivery.
If the top element is a positive or negative response to previously sent data, the
SNAX/HLS replies with a SEND–DATA–REPLY and a RETURN–CODE of
RC–NOTIFICATION or RC–REQUEST–REJECT.
If the top element records the completion of a verb issued with the queued
completion mode selected (or whose operation was interrupted), the completion
notification is passed to your program.
If the receive data queue is empty, SNAX/HLS replies with
RECEIVE–CONTROL–REPLY and a return code of
RC–NO–DATA–AVAILABLE.