Handling a Language Event

This example describes the lang_execute event handler provided in the sample gateway application. This event handler is implemented as a callback function that sends a client's language command to the SQL Server example remote database, receives the results, and returns the results to the client.

1. Define the lang_execute function and the following parameters:

   int lang_execute(srvproc)
   SRV_PROC *srvproc;
   {
   REMOTE_DBMS *rmt_dbms;        // Remote database pointer             
   DBPROCESS *rmtproc;            // Open Data Services DBPROCESS pointer
   DBCHAR *query;                // Pointer to language buffer          
   int query_len;                // Length of query                     
   int status;                    // Status of DB-Library calls          
   

2. Get the remote DBPROCESS pointer *rmtproc in the SRV_PROC connection structure with srv_getuserdata. This is a pointer that was saved using srv_setuserdata after the client connected to a remote database.

   rmt_dbms = (REMOTE_DBMS *)srv_getuserdata(srvproc);
   rmtproc = rmt_dbms->dbproc;
   

3. Get the pointer to the client's language request command buffer using the srv_langptr function, and put the pointer in the DBPROCESS structure of the SQL Server database:

   // Get the pointer to the client language request command buffer. 
   
   query = srv_langptr (srvproc);
   
   // Place the pointer in the remote DBPROCESS pointer rmtproc.     
   
   status = dbcmd (rmtproc, query);
   

4. Send the SQL command to the remote database using the DB-Library dbsqlexec function if the previous DB-Library dbcmd function call was successful:

   if (status == SUCCEED)    // Previous DB-Library call successful   
       status = dbsqlexec (rmtproc);
   else
   
     // If an attention event was issued or if the previous DB-Library
     // call was not successful, acknowledge and send a results       
     // completion message to the client.                             
   
       srv_senddone (srvproc, SRV_DONE_FINAL, (DBUSMALLINT) 0,
            (DBINT) 0);
   

5. Get the remote database results and pass them back to the client using the handle_results function:

   handle_results (rmtproc, srvproc);
   

   (For more information about this function, see Receiving Results from a Remote Database.

6. Return the srv_continue constant to continue processing events:

   return (SRV_CONTINUE);