/* * calyearstart - determine the NTP time at midnight of January 1 in * the year of the given date. */ #include <sys/types.h> #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); }