135 lines
3.0 KiB
C
135 lines
3.0 KiB
C
/* $NetBSD: clocktime.c,v 1.1.1.1 2000/03/29 12:38:49 simonb Exp $ */
|
|
|
|
/*
|
|
* clocktime - compute the NTP date from a day of year, hour, minute
|
|
* and second.
|
|
*/
|
|
#include "ntp_fp.h"
|
|
#include "ntp_unixtime.h"
|
|
#include "ntp_stdlib.h"
|
|
|
|
/*
|
|
* Hacks to avoid excercising the multiplier. I have no pride.
|
|
*/
|
|
#define MULBY10(x) (((x)<<3) + ((x)<<1))
|
|
#define MULBY60(x) (((x)<<6) - ((x)<<2)) /* watch overflow */
|
|
#define MULBY24(x) (((x)<<4) + ((x)<<3))
|
|
|
|
/*
|
|
* Two days, in seconds.
|
|
*/
|
|
#define TWODAYS (2*24*60*60)
|
|
|
|
/*
|
|
* We demand that the time be within CLOSETIME seconds of the receive
|
|
* time stamp. This is about 4 hours, which hopefully should be
|
|
* wide enough to collect most data, while close enough to keep things
|
|
* from getting confused.
|
|
*/
|
|
#define CLOSETIME (4*60*60)
|
|
|
|
|
|
int
|
|
clocktime(
|
|
int yday,
|
|
int hour,
|
|
int minute,
|
|
int second,
|
|
int tzoff,
|
|
u_long rec_ui,
|
|
u_long *yearstart,
|
|
u_int32 *ts_ui
|
|
)
|
|
{
|
|
register long tmp;
|
|
register u_long date;
|
|
register u_long yst;
|
|
|
|
/*
|
|
* Compute the offset into the year in seconds. Note that
|
|
* this could come out to be a negative number.
|
|
*/
|
|
tmp = (long)(MULBY24((yday-1)) + hour + tzoff);
|
|
tmp = MULBY60(tmp) + (long)minute;
|
|
tmp = MULBY60(tmp) + (long)second;
|
|
|
|
/*
|
|
* Initialize yearstart, if necessary.
|
|
*/
|
|
yst = *yearstart;
|
|
if (yst == 0) {
|
|
yst = calyearstart(rec_ui);
|
|
*yearstart = yst;
|
|
}
|
|
|
|
/*
|
|
* Now the fun begins. We demand that the received clock time
|
|
* be within CLOSETIME of the receive timestamp, but
|
|
* there is uncertainty about the year the timestamp is in.
|
|
* Use the current year start for the first check, this should
|
|
* work most of the time.
|
|
*/
|
|
date = (u_long)(tmp + (long)yst);
|
|
if (date < (rec_ui + CLOSETIME) &&
|
|
date > (rec_ui - CLOSETIME)) {
|
|
*ts_ui = date;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Trouble. Next check is to see if the year rolled over and, if
|
|
* so, try again with the new year's start.
|
|
*/
|
|
yst = calyearstart(rec_ui);
|
|
if (yst != *yearstart) {
|
|
date = (u_long)((long)yst + tmp);
|
|
*ts_ui = date;
|
|
if (date < (rec_ui + CLOSETIME) &&
|
|
date > (rec_ui - CLOSETIME)) {
|
|
*yearstart = yst;
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Here we know the year start matches the current system
|
|
* time. One remaining possibility is that the time code
|
|
* is in the year previous to that of the system time. This
|
|
* is only worth checking if the receive timestamp is less
|
|
* than a couple of days into the new year.
|
|
*/
|
|
if ((rec_ui - yst) < TWODAYS) {
|
|
yst = calyearstart(yst - TWODAYS);
|
|
if (yst != *yearstart) {
|
|
date = (u_long)(tmp + (long)yst);
|
|
if (date < (rec_ui + CLOSETIME) &&
|
|
date > (rec_ui - CLOSETIME)) {
|
|
*yearstart = yst;
|
|
*ts_ui = date;
|
|
return 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* One last possibility is that the time stamp is in the year
|
|
* following the year the system is in. Try this one before
|
|
* giving up.
|
|
*/
|
|
yst = calyearstart(rec_ui + TWODAYS);
|
|
if (yst != *yearstart) {
|
|
date = (u_long)((long)yst + tmp);
|
|
if (date < (rec_ui + CLOSETIME) &&
|
|
date > (rec_ui - CLOSETIME)) {
|
|
*yearstart = yst;
|
|
*ts_ui = date;
|
|
return 1;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Give it up.
|
|
*/
|
|
return 0;
|
|
}
|