mktime.c revision 132452 
1/*
2 * Copyright (c) 1987, 1989 Regents of the University of California.
3 * All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Arthur David Olson of the National Cancer Institute.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.  */
35
36/*static char *sccsid = "from: @(#)ctime.c	5.26 (Berkeley) 2/23/91";*/
37/*static char *rcsid = "mktime.c,v 1.1.1.3 1998/11/15 19:23:34 kardel RELEASE_19990228_A";*/
38
39/*
40 * This implementation of mktime is lifted straight from the NetBSD (BSD 4.4)
41 * version.  I modified it slightly to divorce it from the internals of the
42 * ctime library.  Thus this version can't use details of the internal
43 * timezone state file to figure out strange unnormalized struct tm values,
44 * as might result from someone doing date math on the tm struct then passing
45 * it to mktime.
46 *
47 * It just does as well as it can at normalizing the tm input, then does a
48 * binary search of the time space using the system's localtime() function.
49 *
50 * The original binary search was defective in that it didn't consider the
51 * setting of tm_isdst when comparing tm values, causing the search to be
52 * flubbed for times near the dst/standard time changeover.  The original
53 * code seems to make up for this by grubbing through the timezone info
54 * whenever the binary search barfed.  Since I don't have that luxury in
55 * portable code, I have to take care of tm_isdst in the comparison routine.
56 * This requires knowing how many minutes offset dst is from standard time.
57 *
58 * So, if you live somewhere in the world where dst is not 60 minutes offset,
59 * and your vendor doesn't supply mktime(), you'll have to edit this variable
60 * by hand.  Sorry about that.
61 */
62
63#include "ntp_machine.h"
64
65#if !HAVE_MKTIME || !HAVE_TIMEGM
66
67#ifndef DSTMINUTES
68#define DSTMINUTES 60
69#endif
70
71#define FALSE 0
72#define TRUE 1
73
74/* some constants from tzfile.h */
75#define SECSPERMIN      60
76#define MINSPERHOUR     60
77#define HOURSPERDAY     24
78#define DAYSPERWEEK     7
79#define DAYSPERNYEAR    365
80#define DAYSPERLYEAR    366
81#define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
82#define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
83#define MONSPERYEAR     12
84#define TM_YEAR_BASE    1900
85#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
86
87extern time_t	time P((time_t *));
88
89static int	mon_lengths[2][MONSPERYEAR] = {
90	{ 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
91	{ 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
92};
93
94static int	year_lengths[2] = {
95	DAYSPERNYEAR, DAYSPERLYEAR
96};
97
98/*
99** Adapted from code provided by Robert Elz, who writes:
100**	The "best" way to do mktime I think is based on an idea of Bob
101**	Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
102**	It does a binary search of the time_t space.  Since time_t's are
103**	just 32 bits, its a max of 32 iterations (even at 64 bits it
104**	would still be very reasonable).
105*/
106
107#ifndef WRONG
108#define WRONG	(-1)
109#endif /* !defined WRONG */
110
111static void
112normalize(
113	int * tensptr,
114	int * unitsptr,
115	int	base
116	)
117{
118	if (*unitsptr >= base) {
119		*tensptr += *unitsptr / base;
120		*unitsptr %= base;
121	} else if (*unitsptr < 0) {
122		--*tensptr;
123		*unitsptr += base;
124		if (*unitsptr < 0) {
125			*tensptr -= 1 + (-*unitsptr) / base;
126			*unitsptr = base - (-*unitsptr) % base;
127		}
128	}
129}
130
131static struct tm *
132mkdst(
133	struct tm *	tmp
134	)
135{
136    /* jds */
137    static struct tm tmbuf;
138
139    tmbuf = *tmp;
140    tmbuf.tm_isdst = 1;
141    tmbuf.tm_min += DSTMINUTES;
142    normalize(&tmbuf.tm_hour, &tmbuf.tm_min, MINSPERHOUR);
143    return &tmbuf;
144}
145
146static int
147tmcomp(
148	register struct tm * atmp,
149	register struct tm * btmp
150	)
151{
152	register int	result;
153
154	/* compare down to the same day */
155
156	if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
157	    (result = (atmp->tm_mon - btmp->tm_mon)) == 0)
158	    result = (atmp->tm_mday - btmp->tm_mday);
159
160	if(result != 0)
161	    return result;
162
163	/* get rid of one-sided dst bias */
164
165	if(atmp->tm_isdst == 1 && !btmp->tm_isdst)
166	    btmp = mkdst(btmp);
167	else if(btmp->tm_isdst == 1 && !atmp->tm_isdst)
168	    atmp = mkdst(atmp);
169
170	/* compare the rest of the way */
171
172	if ((result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
173	    (result = (atmp->tm_min - btmp->tm_min)) == 0)
174	    result = atmp->tm_sec - btmp->tm_sec;
175	return result;
176}
177
178
179static time_t
180time2(
181	struct tm *	tmp,
182	int * 		okayp,
183	int		usezn
184	)
185{
186	register int			dir;
187	register int			bits;
188	register int			i;
189	register int			saved_seconds;
190	time_t				t;
191	struct tm			yourtm, mytm;
192
193	*okayp = FALSE;
194	yourtm = *tmp;
195	if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
196		normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
197	normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
198	normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
199	normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
200	while (yourtm.tm_mday <= 0) {
201		--yourtm.tm_year;
202		yourtm.tm_mday +=
203			year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
204	}
205	for ( ; ; ) {
206		i = mon_lengths[isleap(yourtm.tm_year +
207			TM_YEAR_BASE)][yourtm.tm_mon];
208		if (yourtm.tm_mday <= i)
209			break;
210		yourtm.tm_mday -= i;
211		if (++yourtm.tm_mon >= MONSPERYEAR) {
212			yourtm.tm_mon = 0;
213			++yourtm.tm_year;
214		}
215	}
216	saved_seconds = yourtm.tm_sec;
217	yourtm.tm_sec = 0;
218	/*
219	** Calculate the number of magnitude bits in a time_t
220	** (this works regardless of whether time_t is
221	** signed or unsigned, though lint complains if unsigned).
222	*/
223	for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
224		;
225	/*
226	** If time_t is signed, then 0 is the median value,
227	** if time_t is unsigned, then 1 << bits is median.
228	*/
229	t = (t < 0) ? 0 : ((time_t) 1 << bits);
230	for ( ; ; ) {
231		if (usezn)
232	        	mytm = *localtime(&t);
233		else
234	        	mytm = *gmtime(&t);
235		dir = tmcomp(&mytm, &yourtm);
236		if (dir != 0) {
237			if (bits-- < 0)
238				return WRONG;
239			if (bits < 0)
240				--t;
241			else if (dir > 0)
242				t -= (time_t) 1 << bits;
243			else	t += (time_t) 1 << bits;
244			continue;
245		}
246		if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
247			break;
248
249		return WRONG;
250	}
251	t += saved_seconds;
252	if (usezn)
253		*tmp = *localtime(&t);
254	else
255		*tmp = *gmtime(&t);
256	*okayp = TRUE;
257	return t;
258}
259#else
260int mktime_bs;
261#endif /* !HAVE_MKTIME || !HAVE_TIMEGM */
262
263#if !HAVE_MKTIME
264static time_t
265time1(
266	struct tm * tmp
267	)
268{
269	register time_t			t;
270	int				okay;
271
272	if (tmp->tm_isdst > 1)
273		tmp->tm_isdst = 1;
274	t = time2(tmp, &okay, 1);
275	if (okay || tmp->tm_isdst < 0)
276		return t;
277
278	return WRONG;
279}
280
281time_t
282mktime(
283	struct tm * tmp
284	)
285{
286	return time1(tmp);
287}
288#endif /* !HAVE_MKTIME */
289
290#if !HAVE_TIMEGM
291time_t
292timegm(
293	struct tm * tmp
294	)
295{
296	register time_t			t;
297	int				okay;
298
299	tmp->tm_isdst = 0;
300	t = time2(tmp, &okay, 0);
301	if (okay || tmp->tm_isdst < 0)
302		return t;
303
304	return WRONG;
305}
306#endif /* !HAVE_TIMEGM */
307