/*
* calyearstart - determine the NTP time at midnight of January 1 in
* the year of the given date.
*/
#include
#include "ntp_types.h"
#include "ntp_calendar.h"
#include "ntp_stdlib.h"
#include "ntp_assert.h"
/*
* Juergen Perlinger, 2008-11-12
* Use the result of 'caljulian' to get the delta from the time stamp to the
* beginning of the year. Do not make a second trip through 'caltontp' after
* fixing the date, apart for invariant tests.
*/
u_long
calyearstart(u_long ntp_time)
{
struct calendar jt;
ntp_u_int32_t delta;
caljulian(ntp_time,&jt);
/*
* Now we have days since yearstart (unity-based) and the time in that
* day. Simply merge these together to seconds and subtract that from
* input time. That's faster than going through the calendar stuff
* again...
*/
delta = (ntp_u_int32_t)jt.yearday * SECSPERDAY
+ (ntp_u_int32_t)jt.hour * MINSPERHR * SECSPERMIN
+ (ntp_u_int32_t)jt.minute * SECSPERMIN
+ (ntp_u_int32_t)jt.second
- SECSPERDAY; /* yearday is unity-based... */
# if ISC_CHECK_INVARIANT
/*
* check that this computes properly: do a roundtrip! That's the only
* sensible test here, but it's a rather expensive invariant...
*/
jt.yearday = 0;
jt.month = 1;
jt.monthday = 1;
jt.hour = 0;
jt.minute = 0;
jt.second = 0;
NTP_INVARIANT((ntp_u_int32_t)(caltontp(&jt) + delta) == (ntp_u_int32_t)ntp_time);
# endif
/* The NTP time stamps (l_fp) count seconds unsigned mod 2**32, so we
* have to calculate this in the proper way!
*/
return (ntp_u_int32_t)(ntp_time - delta);
}