HP-UX SNAplus2 R7 LUA Programmer's Guide

Sample LUA Application
Processing Overview
6 Sample LUA Application
This chapter describes the SNAplus2 sample LUA program /opt/sna/samples/lsample.c, written for the
HP-UX operating system, which illustrates the use of LUA RUI verbs.
The following information is provided:
• Processing overview of the application
• Instructions for compiling, linking, and running the application
6.1 Processing Overview
The application is a very simple 3270 emulation program. It provides an unformatted display of screen data sent
from the host (on both the LU and SSCP sessions), together with status messages (indicating whether the application
is connected to the LU session or the SSCP session). When a definite-response request is received from the host,
a positive response is sent automatically. Data typed in by the user is sent to the host, with the exception of two
special keystrokes:
[ (left square bracket)
Toggles between the LU and SSCP sessions
] (right square bracket)
Terminates the application
Once it has completed some initialization processing, the program essentially consists of two main loops: one
reading data from the host and one sending data supplied by the user to the host. These are implemented as follows:
The
read loop uses recursive calls to the RUI_READ verb. The following processing is performed by the callback
routine, which LUA calls when the verb completes asynchronously:
• Any screen data is written to the screen
• Any session status information is processed
• If a response is required, a positive response is built and sent
• The RUI_READ verb is then re-issued to continue the loop
If the verb completes synchronously, the same routine used as a callback routine is called explicitly on return. This
ensures that the same processing is done whatever the type of return.
The
write loop
reads data from the keyboard. If either of the two special keystrokes is supplied, it is acted on;
otherwise, the incoming data is translated to extended binary coded decimal interchange code (EBCDIC) (using the
CSV CONVERT verb) to be sent to the host on either the LU session or the SSCP session, depending on which
the application is currently connected to. The data is sent using the RUI_WRITE verb; again, the callback routine
is used whether or not the verb returns asynchronously. The program waits for a semaphore to be cleared by the
callback routine before continuing with the loop.
When the user types the ] keystroke to terminate the application, the program breaks out of the write loop and issues
the RUI_TERM verb to end the session. The session is also terminated if the read loop encounters a non-LUA_OK
return code from the RUI_READ verb.
The program flow can be represented by the diagram shown in Figure 6–1, Program Flow for the Sample LUA
Application:
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