1/*	$NetBSD: caltontp.c,v 1.6 2020/05/25 20:47:24 christos Exp $	*/
2
3/*
4 * caltontp - convert a date to an NTP time
5 */
6#include <config.h>
7#include <sys/types.h>
8
9#include "ntp_types.h"
10#include "ntp_calendar.h"
11#include "ntp_stdlib.h"
12#include "ntp_assert.h"
13#include "ntp_unixtime.h"
14
15/*
16 * Juergen Perlinger, 2008-11-12
17 * Add support for full calendar calculatios. If the day-of-year is provided
18 * (that is, not zero) it will be used instead of month and day-of-month;
19 * otherwise a full turn through the calendar calculations will be taken.
20 *
21 * I know that Harlan Stenn likes to see assertions in production code, and I
22 * agree there, but it would be a tricky thing here. The algorithm is quite
23 * capable of producing sensible answers even to seemingly weird inputs: the
24 * date <any year here>-03-00, the 0.th March of the year, will be automtically
25 * treated as the last day of February, no matter whether the year is a leap
26 * year or not. So adding constraints is merely for the benefit of the callers,
27 * because the only thing we can check for consistency is our input, produced
28 * by somebody else.
29 *
30 * BTW: A total roundtrip using 'caljulian' would be a quite shaky thing:
31 * Because of the truncation of the NTP time stamp to 32 bits and the epoch
32 * unfolding around the current time done by 'caljulian' the roundtrip does
33 * *not* necessarily reproduce the input, especially if the time spec is more
34 * than 68 years off from the current time...
35 */
36
37uint32_t
38caltontp(
39	const struct calendar *jt
40	)
41{
42	int32_t eraday;	/* CE Rata Die number	*/
43	vint64  ntptime;/* resulting NTP time	*/
44
45	REQUIRE(jt != NULL);
46
47	REQUIRE(jt->month <= 13);	/* permit month 0..13! */
48	REQUIRE(jt->monthday <= 32);
49	REQUIRE(jt->yearday <= 366);
50	REQUIRE(jt->hour <= 24);
51	REQUIRE(jt->minute <= MINSPERHR);
52	REQUIRE(jt->second <= SECSPERMIN);
53
54	/*
55	 * First convert the date to he corresponding RataDie
56	 * number. If yearday is not zero, assume that it contains a
57	 * useable value and avoid all calculations involving month
58	 * and day-of-month. Do a full evaluation otherwise.
59	 */
60	if (jt->yearday)
61		eraday = ntpcal_year_to_ystart(jt->year)
62		       + jt->yearday - 1;
63	else
64		eraday = ntpcal_date_to_rd(jt);
65
66	ntptime = ntpcal_dayjoin(eraday - DAY_NTP_STARTS,
67				 ntpcal_etime_to_seconds(jt->hour, jt->minute,
68							 jt->second));
69	return ntptime.d_s.lo;
70}
71