1/*	$NetBSD: mktime.c,v 1.5 2020/05/25 20:47:24 christos Exp $	*/
2
3/*
4 * Copyright (c) 1987, 1989 Regents of the University of California.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Arthur David Olson of the National Cancer Institute.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 *    must display the following acknowledgement:
20 *	This product includes software developed by the University of
21 *	California, Berkeley and its contributors.
22 * 4. Neither the name of the University nor the names of its contributors
23 *    may be used to endorse or promote products derived from this software
24 *    without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.  */
37
38/*static char *sccsid = "from: @(#)ctime.c	5.26 (Berkeley) 2/23/91";*/
39
40/*
41 * This implementation of mktime is lifted straight from the NetBSD (BSD 4.4)
42 * version.  I modified it slightly to divorce it from the internals of the
43 * ctime library.  Thus this version can't use details of the internal
44 * timezone state file to figure out strange unnormalized struct tm values,
45 * as might result from someone doing date math on the tm struct then passing
46 * it to mktime.
47 *
48 * It just does as well as it can at normalizing the tm input, then does a
49 * binary search of the time space using the system's localtime() function.
50 *
51 * The original binary search was defective in that it didn't consider the
52 * setting of tm_isdst when comparing tm values, causing the search to be
53 * flubbed for times near the dst/standard time changeover.  The original
54 * code seems to make up for this by grubbing through the timezone info
55 * whenever the binary search barfed.  Since I don't have that luxury in
56 * portable code, I have to take care of tm_isdst in the comparison routine.
57 * This requires knowing how many minutes offset dst is from standard time.
58 *
59 * So, if you live somewhere in the world where dst is not 60 minutes offset,
60 * and your vendor doesn't supply mktime(), you'll have to edit this variable
61 * by hand.  Sorry about that.
62 */
63
64#include <config.h>
65#include "ntp_machine.h"
66
67#if !defined(HAVE_MKTIME) || ( !defined(HAVE_TIMEGM) && defined(WANT_TIMEGM) )
68
69#if SIZEOF_TIME_T >= 8
70#error libntp supplied mktime()/timegm() do not support 64-bit time_t
71#endif
72
73#ifndef DSTMINUTES
74#define DSTMINUTES 60
75#endif
76
77#define FALSE 0
78#define TRUE 1
79
80/* some constants from tzfile.h */
81#define SECSPERMIN      60
82#define MINSPERHOUR     60
83#define HOURSPERDAY     24
84#define DAYSPERWEEK     7
85#define DAYSPERNYEAR    365
86#define DAYSPERLYEAR    366
87#define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
88#define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
89#define MONSPERYEAR     12
90#define TM_YEAR_BASE    1900
91#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
92
93static int	mon_lengths[2][MONSPERYEAR] = {
94	{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
95	{ 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
96};
97
98static int	year_lengths[2] = {
99	DAYSPERNYEAR, DAYSPERLYEAR
100};
101
102/*
103** Adapted from code provided by Robert Elz, who writes:
104**	The "best" way to do mktime I think is based on an idea of Bob
105**	Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
106**	It does a binary search of the time_t space.  Since time_t's are
107**	just 32 bits, its a max of 32 iterations (even at 64 bits it
108**	would still be very reasonable).
109*/
110
111#ifndef WRONG
112#define WRONG	(-1)
113#endif /* !defined WRONG */
114
115static void
116normalize(
117	int * tensptr,
118	int * unitsptr,
119	int	base
120	)
121{
122	if (*unitsptr >= base) {
123		*tensptr += *unitsptr / base;
124		*unitsptr %= base;
125	} else if (*unitsptr < 0) {
126		--*tensptr;
127		*unitsptr += base;
128		if (*unitsptr < 0) {
129			*tensptr -= 1 + (-*unitsptr) / base;
130			*unitsptr = base - (-*unitsptr) % base;
131		}
132	}
133}
134
135static struct tm *
136mkdst(
137	struct tm *	tmp
138	)
139{
140    /* jds */
141    static struct tm tmbuf;
142
143    tmbuf = *tmp;
144    tmbuf.tm_isdst = 1;
145    tmbuf.tm_min += DSTMINUTES;
146    normalize(&tmbuf.tm_hour, &tmbuf.tm_min, MINSPERHOUR);
147    return &tmbuf;
148}
149
150static int
151tmcomp(
152	register struct tm * atmp,
153	register struct tm * btmp
154	)
155{
156	register int	result;
157
158	/* compare down to the same day */
159
160	if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
161	    (result = (atmp->tm_mon - btmp->tm_mon)) == 0)
162	    result = (atmp->tm_mday - btmp->tm_mday);
163
164	if(result != 0)
165	    return result;
166
167	/* get rid of one-sided dst bias */
168
169	if(atmp->tm_isdst == 1 && !btmp->tm_isdst)
170	    btmp = mkdst(btmp);
171	else if(btmp->tm_isdst == 1 && !atmp->tm_isdst)
172	    atmp = mkdst(atmp);
173
174	/* compare the rest of the way */
175
176	if ((result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
177	    (result = (atmp->tm_min - btmp->tm_min)) == 0)
178	    result = atmp->tm_sec - btmp->tm_sec;
179	return result;
180}
181
182
183static time_t
184time2(
185	struct tm *	tmp,
186	int * 		okayp,
187	int		usezn
188	)
189{
190	register int			dir;
191	register int			bits;
192	register int			i;
193	register int			saved_seconds;
194	time_t				t;
195	struct tm			yourtm, mytm;
196
197	*okayp = FALSE;
198	yourtm = *tmp;
199	if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
200		normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
201	normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
202	normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
203	normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
204	while (yourtm.tm_mday <= 0) {
205		--yourtm.tm_year;
206		yourtm.tm_mday +=
207			year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
208	}
209	for ( ; ; ) {
210		i = mon_lengths[isleap(yourtm.tm_year +
211			TM_YEAR_BASE)][yourtm.tm_mon];
212		if (yourtm.tm_mday <= i)
213			break;
214		yourtm.tm_mday -= i;
215		if (++yourtm.tm_mon >= MONSPERYEAR) {
216			yourtm.tm_mon = 0;
217			++yourtm.tm_year;
218		}
219	}
220	saved_seconds = yourtm.tm_sec;
221	yourtm.tm_sec = 0;
222	/*
223	** Calculate the number of magnitude bits in a time_t
224	** (this works regardless of whether time_t is
225	** signed or unsigned, though lint complains if unsigned).
226	*/
227	for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
228		;
229	/*
230	** If time_t is signed, then 0 is the median value,
231	** if time_t is unsigned, then 1 << bits is median.
232	*/
233	t = (t < 0) ? 0 : ((time_t) 1 << bits);
234	for ( ; ; ) {
235		if (usezn)
236			mytm = *localtime(&t);
237		else
238			mytm = *gmtime(&t);
239		dir = tmcomp(&mytm, &yourtm);
240		if (dir != 0) {
241			if (bits-- < 0)
242				return WRONG;
243			if (bits < 0)
244				--t;
245			else if (dir > 0)
246				t -= (time_t) 1 << bits;
247			else	t += (time_t) 1 << bits;
248			continue;
249		}
250		if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
251			break;
252
253		return WRONG;
254	}
255	t += saved_seconds;
256	if (usezn)
257		*tmp = *localtime(&t);
258	else
259		*tmp = *gmtime(&t);
260	*okayp = TRUE;
261	return t;
262}
263#else
264int mktime_bs;
265#endif /* !HAVE_MKTIME || !HAVE_TIMEGM */
266
267#ifndef HAVE_MKTIME
268static time_t
269time1(
270	struct tm * tmp
271	)
272{
273	register time_t			t;
274	int				okay;
275
276	if (tmp->tm_isdst > 1)
277		tmp->tm_isdst = 1;
278	t = time2(tmp, &okay, 1);
279	if (okay || tmp->tm_isdst < 0)
280		return t;
281
282	return WRONG;
283}
284
285time_t
286mktime(
287	struct tm * tmp
288	)
289{
290	return time1(tmp);
291}
292#endif /* !HAVE_MKTIME */
293
294#ifdef WANT_TIMEGM
295#ifndef HAVE_TIMEGM
296time_t
297timegm(
298	struct tm * tmp
299	)
300{
301	register time_t			t;
302	int				okay;
303
304	tmp->tm_isdst = 0;
305	t = time2(tmp, &okay, 0);
306	if (okay || tmp->tm_isdst < 0)
307		return t;
308
309	return WRONG;
310}
311#endif /* !HAVE_TIMEGM */
312#endif /* WANT_TIMEGM */
313