/* file:    ClockSyncServer.c */
/* author:  MLehr */

/*
 *                     Copyright (C) 1994
 *           by the Rector and Board of Visitors of
 *                 the University of Virginia
 *
 *                   for more information:
 *                        Sanghyuk Son
 *               Department of Computer Science
 *         School of Engineering and Applied Science
 *                   University of Virginia
 *                 Charlottesville, VA  22903
 */


#include "ClockSync.h"

/* This program is inspired by "Time, Clocks, and the Ordering of
   Events in a Distributed System" by Lamport.

   Start up a server on the two hosts to be synchronized, then
   start up the client portion of this program on each host. */

static ClockSyncReplyMessage	reply;
static ClockSyncRequestMessage	request;
static mach_port_t		clock;
static mach_port_t		servicePort;
static rt_priority_data_t	priority;


void main ()
  {
  kern_return_t		status;
  rt_mach_port_attr_t	portAttrs;

  OPEN_RT_CLOCK (clock, status);

  /* here we don't care what values we initialize with
     since RT-IPC will perform priority handoff for us */
     
  bzero ((char *) &priority, sizeof (rt_priority_data_t));

  INIT_RT_MESSAGE_HEADER (request,
			  request.header,
			  request.descriptor,
			  0,
			  priority.rt_deadline,
			  priority.rt_period,
			  CRITICALITY);
  INIT_RT_MESSAGE_HEADER (reply,
			  reply.header,
			  reply.descriptor,
			  0,
			  priority.rt_deadline,
			  priority.rt_period,
			  CRITICALITY);

  /* create the service port and register it with
     Mach's network name server */

  INIT_RT_PORT_ATTR (portAttrs,
		     sizeof (ClockSyncRequestMessage),
		     2,
		     DISP_PRI,
		     PRI_BPI,
		     HANDOFF_MSG);
  CREATE_RT_PORT (servicePort, portAttrs, status);
  RT_PORT_ASSOCIATE (mach_thread_self (),
		     servicePort,
		     priority,
		     status);

  status = netname_check_in (name_server_port,
			     "ClockSyncServer",
                             mach_task_self (),
                             servicePort);
  if (status != KERN_SUCCESS)
    MACH_CRASH ("netname_check_in", status);

  while (TRUE)
    {
    RECEIVE_RT_MESSAGE (servicePort, request.header, status);

    /* "IR2: If event a is the sending of a message m by process P[i],
       then the message m contains a timestamp T[m] = C[i]<a>." */

    READ_TIME (clock, reply.timeStamp, status);
    SEND_RT_MESSAGE (request.header.msgh_remote_port, reply.header, status);
    }
  exit (-1);
  }