GDSX Manual

DEVICE^HANDLER Example, Design
Extended General Device Support (GDSX) Manual–134303
5-10
The DEVICE^HANDLER Procedure
The first, term^file^num, is the pseudo-file number (not a Guardian file number) used
for I/O to the file that this task is to manage. Note that the DEVICE^HANDLER does
not open this file; TSCODE opens it, assigns a term^file^num for the task to use, and
passes this number when the call to DEVICE^HANDLER creates the task.
The second parameter is the internal^term^no. Each DEVICE^HANDLER task has
exactly one device control block (DCB) associated with it. Internal^term^no is an index
used to find this task’s DCB in the array of DCBs. This is discussed later in this section.
If a task is configured with the SCF ADD SU command (which is discussed in Section
6), the SU’s SUTYPE attribute can be set, indicating what type of terminal is being
configured. When TSCODE calls the DEVICE^HANDLER procedure, it passes this
setting as the term^type parameter; the DEVICE^HANDLER task can then use a CASE
statement on term^type to branch to different code for different types of terminals.
Example 5-2 also shows miscellaneous pointers as well as literals used for analyzing the
five different kinds of requests that may be received.
Reading and Decoding Requests
Although the SCAN^BUF subprocedure appears next in the source code (see Appendix
B), it is discussed with the different types of request processing below.
Within the main loop of the DEVICE^HANDLER (see Example 5-3 and Example 5-6),
a buffer of size buf^size is requested from the byte-addressable extended buffer pool.
The buffer holds a message read from the pseudo-$RECEIVE file. Because tasks are
Example 5-2. DEVICE^HANDLER Local Declarations
PROC DEVICE^HANDLER (TERM^FILE^NUM, INTERNAL^TERM^NO, TERM^TYPE);
INT TERM^FILE^NUM , ! FILE^NUM FOR THIS D^H TASK
INTERNAL^TERM^NO, ! TERM NUMBER FOR THIS D^H TASK
TERM^TYPE ; ! TERMINAL TYPE
BEGIN
!===============================================================
! Comment - USCODE can declare desired Device^Handler Local
! Variables here
!===============================================================
INT .EXT MY^DCB(DCB^TEMPLATE);
INT .EXT TERM^BUF;
STRING .EXT S^TERM^BUF;
INT .EXT RCV^BUF;
STRING .EXT S^RCV^BUF;
INT .EXT E^RCV^BUF := 0D;
INT RQSTR^WT^CT;
INT RQSTR^RD^CT;
INT TERM^CT^RD;
INT DOLR^RCV := 0;
INT RQST^TYPE := 0;
INT FERR;
INT TAKE^OVER;
LITERAL WT=1, RD=2, WT^RD=3, CTRL=4, SET^MD=5;
LITERAL BUF^SIZE = 1024;