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/*
* 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;
}
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