xref: /freebsd/contrib/ntp/libntp/caltontp.c (revision f4b37ed0f8b307b1f3f0f630ca725d68f1dff30d)
1 /*
2  * caltontp - convert a date to an NTP time
3  */
4 #include <config.h>
5 #include <sys/types.h>
6 
7 #include "ntp_types.h"
8 #include "ntp_calendar.h"
9 #include "ntp_stdlib.h"
10 #include "ntp_assert.h"
11 #include "ntp_unixtime.h"
12 
13 /*
14  * Juergen Perlinger, 2008-11-12
15  * Add support for full calendar calculatios. If the day-of-year is provided
16  * (that is, not zero) it will be used instead of month and day-of-month;
17  * otherwise a full turn through the calendar calculations will be taken.
18  *
19  * I know that Harlan Stenn likes to see assertions in production code, and I
20  * agree there, but it would be a tricky thing here. The algorithm is quite
21  * capable of producing sensible answers even to seemingly weird inputs: the
22  * date <any year here>-03-00, the 0.th March of the year, will be automtically
23  * treated as the last day of February, no matter whether the year is a leap
24  * year or not. So adding constraints is merely for the benefit of the callers,
25  * because the only thing we can check for consistency is our input, produced
26  * by somebody else.
27  *
28  * BTW: A total roundtrip using 'caljulian' would be a quite shaky thing:
29  * Because of the truncation of the NTP time stamp to 32 bits and the epoch
30  * unfolding around the current time done by 'caljulian' the roundtrip does
31  * *not* necessarily reproduce the input, especially if the time spec is more
32  * than 68 years off from the current time...
33  */
34 
35 uint32_t
36 caltontp(
37 	const struct calendar *jt
38 	)
39 {
40 	int32_t eraday;	/* CE Rata Die number	*/
41 	vint64  ntptime;/* resulting NTP time	*/
42 
43 	NTP_INSIST(jt != NULL);
44 
45 	NTP_REQUIRE(jt->month <= 13);	/* permit month 0..13! */
46 	NTP_REQUIRE(jt->monthday <= 32);
47 	NTP_REQUIRE(jt->yearday <= 366);
48 	NTP_REQUIRE(jt->hour <= 24);
49 	NTP_REQUIRE(jt->minute <= MINSPERHR);
50 	NTP_REQUIRE(jt->second <= SECSPERMIN);
51 
52 	/*
53 	 * First convert the date to he corresponding RataDie
54 	 * number. If yearday is not zero, assume that it contains a
55 	 * useable value and avoid all calculations involving month
56 	 * and day-of-month. Do a full evaluation otherwise.
57 	 */
58 	if (jt->yearday)
59 		eraday = ntpcal_year_to_ystart(jt->year)
60 		       + jt->yearday - 1;
61 	else
62 		eraday = ntpcal_date_to_rd(jt);
63 
64 	ntptime = ntpcal_dayjoin(eraday - DAY_NTP_STARTS,
65 				 ntpcal_etime_to_seconds(jt->hour, jt->minute,
66 							 jt->second));
67 	return ntptime.d_s.lo;
68 }
69