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Diffstat (limited to 'libntp/caltontp.c')
-rw-r--r-- | libntp/caltontp.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/libntp/caltontp.c b/libntp/caltontp.c new file mode 100644 index 000000000000..808c94c64afd --- /dev/null +++ b/libntp/caltontp.c @@ -0,0 +1,68 @@ +/* + * caltontp - convert a date to an NTP time + */ +#include <config.h> +#include <sys/types.h> + +#include "ntp_types.h" +#include "ntp_calendar.h" +#include "ntp_stdlib.h" +#include "ntp_assert.h" +#include "ntp_unixtime.h" + +/* + * Juergen Perlinger, 2008-11-12 + * Add support for full calendar calculatios. If the day-of-year is provided + * (that is, not zero) it will be used instead of month and day-of-month; + * otherwise a full turn through the calendar calculations will be taken. + * + * I know that Harlan Stenn likes to see assertions in production code, and I + * agree there, but it would be a tricky thing here. The algorithm is quite + * capable of producing sensible answers even to seemingly weird inputs: the + * date <any year here>-03-00, the 0.th March of the year, will be automtically + * treated as the last day of February, no matter whether the year is a leap + * year or not. So adding constraints is merely for the benefit of the callers, + * because the only thing we can check for consistency is our input, produced + * by somebody else. + * + * BTW: A total roundtrip using 'caljulian' would be a quite shaky thing: + * Because of the truncation of the NTP time stamp to 32 bits and the epoch + * unfolding around the current time done by 'caljulian' the roundtrip does + * *not* necessarily reproduce the input, especially if the time spec is more + * than 68 years off from the current time... + */ + +uint32_t +caltontp( + const struct calendar *jt + ) +{ + int32_t eraday; /* CE Rata Die number */ + vint64 ntptime;/* resulting NTP time */ + + REQUIRE(jt != NULL); + + REQUIRE(jt->month <= 13); /* permit month 0..13! */ + REQUIRE(jt->monthday <= 32); + REQUIRE(jt->yearday <= 366); + REQUIRE(jt->hour <= 24); + REQUIRE(jt->minute <= MINSPERHR); + REQUIRE(jt->second <= SECSPERMIN); + + /* + * First convert the date to he corresponding RataDie + * number. If yearday is not zero, assume that it contains a + * useable value and avoid all calculations involving month + * and day-of-month. Do a full evaluation otherwise. + */ + if (jt->yearday) + eraday = ntpcal_year_to_ystart(jt->year) + + jt->yearday - 1; + else + eraday = ntpcal_date_to_rd(jt); + + ntptime = ntpcal_dayjoin(eraday - DAY_NTP_STARTS, + ntpcal_etime_to_seconds(jt->hour, jt->minute, + jt->second)); + return ntptime.d_s.lo; +} |