refclock_datum.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

	int error_code;
	struct datum_pts_unit *datum_pts;

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Poll Datum PTS\n");
#endif

	/*
	** Find the right unit and send out a time request once it is found.
	*/

	unit_index = -1;
	for (i=0; i<nunits; i++) {
		if (datum_pts_unit[i]->unit == unit) {
			unit_index = i;
			datum_pts = datum_pts_unit[i];
			error_code = write(datum_pts->PTS_fd, TIME_REQUEST, 6);
			if (error_code != 6) perror("TIME_REQUEST");
			datum_pts->nbytes = 0;
			break;
		}
	}

	/*
	** Print out an error message if we could not find the right unit.
	*/

	if (unit_index == -1) {

#ifdef DEBUG_DATUM_PTC
		if (debug)
		    printf("Error, could not poll unit %d\n",unit);
#endif

		msyslog(LOG_ERR, "Datum_PTS: Could not poll unit %d",unit);
		return;

	}

}


/*......................................................................*/
/*	datum_pts_control - not used					*/
/*......................................................................*/

static void
datum_pts_control(
	int unit,
	struct refclockstat *in,
	struct refclockstat *out,
	struct peer *peer
	)
{

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Control Datum PTS\n");
#endif

}


/*......................................................................*/
/*	datum_pts_init - initializes things for all possible Datum	*/
/*	time code generators that might be used. In practice, this is	*/
/*	only called once at the beginning before anything else is	*/
/*	called.								*/
/*......................................................................*/

static void
datum_pts_init(void)
{

	/*									*/
	/*...... open up the log file if we are debugging ......................*/
	/*									*/

	/*
	** Open up the log file if we are debugging. For now, send data out to the
	** screen (stdout).
	*/

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Init Datum PTS\n");
#endif

	/*
	** Initialize the time request command string. This is the only message
	** that we ever have to send to the Datum PTS (although others are defined).
	*/

	memcpy(TIME_REQUEST, "//k/mn",6);

	/*
	** Initialize the number of units to 0 and set the dynamic array of units to
	** NULL since there are no units defined yet.
	*/

	datum_pts_unit = NULL;
	nunits = 0;

}


/*......................................................................*/
/*	datum_pts_buginfo - not used					*/
/*......................................................................*/

static void
datum_pts_buginfo(
	int unit,
	register struct refclockbug *bug,
	register struct peer *peer
	)
{

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Buginfo Datum PTS\n");
#endif

}


/*......................................................................*/
/*	datum_pts_receive - receive the time buffer that was read in	*/
/*	by the ntpd io handling routines. When 7 bytes have been	*/
/*	received (it may take several tries before all 7 bytes are	*/
/*	received), then the time code must be unpacked and sent to	*/
/*	the ntpd clock_receive() routine which causes the systems	*/
/*	clock to be updated (several layers down).			*/
/*......................................................................*/

static void
datum_pts_receive(
	struct recvbuf *rbufp
	)
{
	int i;
	l_fp tstmp;
	struct datum_pts_unit *datum_pts;
	char *dpt;
	int dpend;
	int tzoff;
	int timerr;
	double ftimerr, abserr;
#ifdef DEBUG_DATUM_PTC
	double dispersion;
#endif
	int goodtime;
      /*double doffset;*/

	/*
	** Get the time code (maybe partial) message out of the rbufp buffer.
	*/

	datum_pts = (struct datum_pts_unit *)rbufp->recv_srcclock;
	dpt = (char *)&rbufp->recv_space;
	dpend = rbufp->recv_length;

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Receive Datum PTS: %d bytes\n", dpend);
#endif

	/*									*/
	/*...... save the ntp system time when the first byte is received ......*/
	/*									*/

	/*
	** Save the ntp system time when the first byte is received. Note that
	** because it may take several calls to this routine before all seven
	** bytes of our return message are finally received by the io handlers in
	** ntpd, we really do want to use the time tag when the first byte is
	** received to reduce the jitter.
	*/

	if (datum_pts->nbytes == 0) {
		datum_pts->lastrec = rbufp->recv_time;
	}

	/*
	** Increment our count to the number of bytes received so far. Return if we
	** haven't gotten all seven bytes yet.
	*/

	for (i=0; i<dpend; i++) {
		datum_pts->retbuf[datum_pts->nbytes+i] = dpt[i];
	}

	datum_pts->nbytes += dpend;

	if (datum_pts->nbytes != 7) {
		return;
	}

	/*
	** Convert the seven bytes received in our time buffer to day, hour, minute,
	** second, and msecond values. The usec value is not used for anything
	** currently. It is just the fractional part of the time stored in units
	** of microseconds.
	*/

	datum_pts->day =	100*(datum_pts->retbuf[0] & 0x0f) +
		10*((datum_pts->retbuf[1] & 0xf0)>>4) +
		(datum_pts->retbuf[1] & 0x0f);

	datum_pts->hour =	10*((datum_pts->retbuf[2] & 0x30)>>4) +
		(datum_pts->retbuf[2] & 0x0f);

	datum_pts->minute =	10*((datum_pts->retbuf[3] & 0x70)>>4) +
		(datum_pts->retbuf[3] & 0x0f);

	datum_pts->second =	10*((datum_pts->retbuf[4] & 0x70)>>4) +
		(datum_pts->retbuf[4] & 0x0f);

	datum_pts->msec =	100*((datum_pts->retbuf[5] & 0xf0) >> 4) + 
		10*(datum_pts->retbuf[5] & 0x0f) +
		((datum_pts->retbuf[6] & 0xf0)>>4);

	datum_pts->usec =	1000*datum_pts->msec;

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("day %d, hour %d, minute %d, second %d, msec %d\n",
		   datum_pts->day,
		   datum_pts->hour,
		   datum_pts->minute,
		   datum_pts->second,
		   datum_pts->msec);
#endif

	/*
	** Get the GMT time zone offset. Note that GMT should be zero if the Datum
	** reference time is using GMT as its time base. Otherwise we have to
	** determine the offset if the Datum PTS is using time of day as its time
	** base.
	*/

	goodtime = 0;		/* We are not sure about the time and offset yet */

#ifdef GMT

	/*
	** This is the case where the Datum PTS is using GMT so there is no time
	** zone offset.
	*/

	tzoff = 0;		/* set time zone offset to 0 */

#else

	/*
	** This is the case where the Datum PTS is using regular time of day for its
	** time so we must compute the time zone offset. The way we do it is kind of
	** funny but it works. We loop through different time zones (0 to 24) and
	** pick the one that gives the smallest error (+- one half hour). The time
	** zone offset is stored in the datum_pts structure for future use. Normally,
	** the clocktime() routine is only called once (unless the time zone offset
	** changes due to daylight savings) since the goodtime flag is set when a
	** good time is found (with a good offset). Note that even if the Datum
	** PTS is using GMT, this mechanism will still work since it should come up
	** with a value for tzoff = 0 (assuming that your system clock is within
	** a half hour of the Datum time (even with time zone differences).
	*/

	for (tzoff=0; tzoff<24; tzoff++) {
		if (clocktime( datum_pts->day,
			       datum_pts->hour,
			       datum_pts->minute,
			       datum_pts->second,
			       (tzoff + datum_pts->tzoff) % 24,
			       datum_pts->lastrec.l_ui,
			       &datum_pts->yearstart,
			       &datum_pts->lastref.l_ui) ) {

			datum_pts->lastref.l_uf = 0;
			error = datum_pts->lastref.l_ui - datum_pts->lastrec.l_ui;

#ifdef DEBUG_DATUM_PTC
			printf("Time Zone (clocktime method) = %d, error = %d\n", tzoff, error);
#endif

			if ((error < 1799) && (error > -1799)) {
				tzoff = (tzoff + datum_pts->tzoff) % 24;
				datum_pts->tzoff = tzoff;
				goodtime = 1;

#ifdef DEBUG_DATUM_PTC
				printf("Time Zone found (clocktime method) = %d\n",tzoff);
#endif

				break;
			}

		}
	}

#endif

	/*
	** Make sure that we have a good time from the Datum PTS. Clocktime() also
	** sets yearstart and lastref.l_ui. We will have to set astref.l_uf (i.e.,
	** the fraction of a second) stuff later.
	*/

	if (!goodtime) {

		if (!clocktime( datum_pts->day,
				datum_pts->hour,
				datum_pts->minute,
				datum_pts->second,
				tzoff,
				datum_pts->lastrec.l_ui,
				&datum_pts->yearstart,
				&datum_pts->lastref.l_ui) ) {

#ifdef DEBUG_DATUM_PTC
			if (debug)
			{
				printf("Error: bad clocktime\n");
				printf("GMT %d, lastrec %d, yearstart %d, lastref %d\n",
				       tzoff,
				       datum_pts->lastrec.l_ui,
				       datum_pts->yearstart,
				       datum_pts->lastref.l_ui);
			}
#endif

			msyslog(LOG_ERR, "Datum_PTS: Bad clocktime");

			return;

		}else{

#ifdef DEBUG_DATUM_PTC
			if (debug)
			    printf("Good clocktime\n");
#endif

		}

	}

	/*
	** We have datum_pts->lastref.l_ui set (which is the integer part of the
	** time. Now set the microseconds field.
	*/

	TVUTOTSF(datum_pts->usec, datum_pts->lastref.l_uf);

	/*
	** Compute the time correction as the difference between the reference
	** time (i.e., the Datum time) minus the receive time (system time).
	*/

	tstmp = datum_pts->lastref;		/* tstmp is the datum ntp time */
	L_SUB(&tstmp, &datum_pts->lastrec);	/* tstmp is now the correction */
	datum_pts->coderecv++;		/* increment a counter */

#ifdef DEBUG_DATUM_PTC
	dispersion = DATUM_DISPERSION;	/* set the dispersion to 0 */
	ftimerr = dispersion;
	ftimerr /= (1024.0 * 64.0);
	if (debug)
	    printf("dispersion = %d, %f\n", dispersion, ftimerr);
#endif

	/*
	** Pass the new time to ntpd through the refclock_receive function. Note
	** that we are not trying to make any corrections due to the time it takes
	** for the Datum PTS to send the message back. I am (erroneously) assuming
	** that the time for the Datum PTS to send the time back to us is negligable.
	** I suspect that this time delay may be as much as 15 ms or so (but probably
	** less). For our needs at JPL, this kind of error is ok so it is not
	** necessary to use fudge factors in the ntp.conf file. Maybe later we will.
	*/
      /*LFPTOD(&tstmp, doffset);*/
	datum_pts->lastref = datum_pts->lastrec;
	refclock_receive(datum_pts->peer);

	/*
	** Compute sigma squared (not used currently). Maybe later, this could be
	** used for the dispersion estimate. The problem is that ntpd does not link
	** in the math library so sqrt() is not available. Anyway, this is useful
	** for debugging. Maybe later I will just use absolute values for the time
	** error to come up with my dispersion estimate. Anyway, for now my dispersion
	** is set to 0.
	*/

	timerr = tstmp.l_ui<<20;
	timerr |= (tstmp.l_uf>>12) & 0x000fffff;
	ftimerr = timerr;
	ftimerr /= 1024*1024;
	abserr = ftimerr;
	if (ftimerr < 0.0) abserr = -ftimerr;

	if (datum_pts->sigma2 == 0.0) {
		if (abserr < DATUM_MAX_ERROR) {
			datum_pts->sigma2 = abserr*abserr;
		}else{
			datum_pts->sigma2 = DATUM_MAX_ERROR2;
		}
	}else{
		if (abserr < DATUM_MAX_ERROR) {
			datum_pts->sigma2 = 0.95*datum_pts->sigma2 + 0.05*abserr*abserr;
		}else{
			datum_pts->sigma2 = 0.95*datum_pts->sigma2 + 0.05*DATUM_MAX_ERROR2;
		}
	}

#ifdef DEBUG_DATUM_PTC
	if (debug)
	    printf("Time error = %f seconds\n", ftimerr);
#endif

#if defined(DEBUG_DATUM_PTC) || defined(LOG_TIME_ERRORS)
	if (debug)
	    printf("PTS: day %d, hour %d, minute %d, second %d, msec %d, Time Error %f\n",
		   datum_pts->day,
		   datum_pts->hour,
		   datum_pts->minute,
		   datum_pts->second,
		   datum_pts->msec,
		   ftimerr);
#endif

}
#else
int refclock_datum_bs;
#endif /* REFCLOCK */