6.2.1 Example: Using the Same Buffer for Request and Reply Messages

The following listing shows how the client program, audit.c, makes a synchronous call using the same buffer for both the request and reply messages. In this case, using the same buffer is appropriate because the *audv message buffer has been set up to accommodate both request and reply information. The following actions are taken in this code:

1. The service queries the b_id field, but does not overwrite it.
2. The application initializes the bal and ermsg fields to zero and the NULL string, respectively, in preparation for the values to be returned by the service.
3. The svc_name and hdr_type variables represent the service name and the balance type requested, respectively. In this example, these variables represent account and teller, respectively.

Listing 6‑1 Using the Same Buffer for Request and Reply Messages

. . .
/* Create buffer and set data pointer */

audv = (struct aud *)tpalloc("VIEW", "aud", sizeof(struct aud));

      /* Prepare aud structure */

audv->b_id = q_branchid;
audv->balance = 0.0;
(void)strcpy(audv->ermsg, "");

         /* Do tpcall */

if (tpcall(svc_name,(char *)audv,sizeof(struct aud),
      (char **)&audv,(long *)&audrl,0)== -1){
      (void)fprintf (stderr, "%s service failed\n %s: %s\n",
       svc_name, svc_name, audv->ermsg);
       retc = -1;
}
else
       (void)printf ("Branch %ld %s balance is $%.2f\n",
           audv->b_id, hdr_type, audv->balance);
. . .