A Modifying DD Consumer Process

The following sample program is a process, that receives every event which has the control word fev.ctlw1 = 1 set. It then merges two consequetive events into a single event and inject these back into the DD system. Note that the fev.ctlw1 for the new event has changed in order to avoid turning in circles. (Note: for simplicity no proper error handling is included in the code).

#include <dd_user.h>

 
main(int argc,char **argv)

{

		   int len, status, status1, status2, status3

		   char fname[100];

		   int mode, reqcnt, prescale, wait,ctl[4];

		   struct fifo_entry fev1, fev2, fev3;

		   int go_on;

		   if (argc < 2) {

		 		     printf("syntax: argument fifo name needed \n");

		 		     exit(0);

		   }

		   strcpy(fname,argv[1]);

		   mode = FMODE_COND;

		   wait = DD_WAIT_SLEEP;

		   prescale = 1;

		   ctl[0] =  1 ;

		   ctl[1] = -1;

		   ctl[2] = -1;

		   ctl[3] = -1;

		   if ( (status = ddu_init(fname,mode,prescale,wait,ctl)) != 0 ) {

		 		     printf("ddu_init: status returned %d\n",status);

		 		     exit(1);

		   }

		   ddu_start();

		   go_on = 1;

		   while (go_on & & ddu_attached() ) {

		 		     status1 = ddu_get_fev(&fev1);

		 		     status2 = ddu_get_fev(&fev2);

		 		     if ( (status1 || status2)  == 0) {

		 		 		 len = fev1.len + fev2.len;

		 		 		 if ( (status3 = ddu_req_fev(&fev3) ) == 0 ) {

		 		 		 		 memcpy(fev3.p2da, fev1.p2da, 4*fev1.len);

		 		 		 		 memcpy(fev3.p2da+4*fev1.len, fev2.p2da, 4*fev2.len);

		 		 		 		 fev3.len = len;

		 		 		 		 fev3.ctlw1 = 2;

		 		 		 		 fev3.ctlb1 = -1;

		 		 		 		 fev3.ctlw2 = -1;

		 		 		 		 fev3.ctlb2 = -1;

		 		 		 		 if ( (status = ddu_ins_fev(fev3)) != 0 ) {

		 		 		 		 		 /* handle error */

		 		 		   		    }

		 		 		 		 if ( (status = ddu_put_fev(fev2)) != 0 ) {

		 		 		 		 		 /* handle error */

		 		 		 		     }

		 		 		 		 if ( (status = ddu_put_fev(fev1)) != 0 ) {

		 		 		 		 		 /* handle error */

		 		 		  		     }

		 		 		 else {

		 		 		 		  /* handle error */

		 		 		 }

		 		 else {

		 		  /* handle error */

		 		 }

		 }

		   ddu_stop();

		   ddu_close();

		   exit(0);

}