2 * Copyright (c) 1987, 1989 Regents of the University of California.
5 * This code is derived from software contributed to Berkeley by
6 * Arthur David Olson of the National Cancer Institute.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
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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.
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36 /*static char *sccsid = "from: @(#)ctime.c 5.26 (Berkeley) 2/23/91";*/
37 /*static char *rcsid = "$Id: mktime.c,v 1.5 2006/05/25 01:47:12 johnfranks Exp $";*/
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
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.
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.
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.
72 /* some constants from tzfile.h */
74 #define MINSPERHOUR 60
75 #define HOURSPERDAY 24
77 #define DAYSPERNYEAR 365
78 #define DAYSPERLYEAR 366
79 #define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
80 #define SECSPERDAY ((long) SECSPERHOUR * HOURSPERDAY)
81 #define MONSPERYEAR 12
82 #define TM_YEAR_BASE 1900
83 #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
85 static int mon_lengths[2][MONSPERYEAR] = {
86 { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
87 { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
90 static int year_lengths[2] = {
91 DAYSPERNYEAR, DAYSPERLYEAR
95 ** Adapted from code provided by Robert Elz, who writes:
96 ** The "best" way to do mktime I think is based on an idea of Bob
97 ** Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
98 ** It does a binary search of the time_t space. Since time_t's are
99 ** just 32 bits, its a max of 32 iterations (even at 64 bits it
100 ** would still be very reasonable).
105 #endif /* !defined WRONG */
108 normalize(tensptr, unitsptr, base)
113 if (*unitsptr >= base) {
114 *tensptr += *unitsptr / base;
116 } else if (*unitsptr < 0) {
120 *tensptr -= 1 + (-*unitsptr) / base;
121 *unitsptr = base - (-*unitsptr) % base;
131 static struct tm tmbuf;
135 tmbuf.tm_min += DSTMINUTES;
136 normalize(&tmbuf.tm_hour, &tmbuf.tm_min, MINSPERHOUR);
142 register struct tm * atmp;
143 register struct tm * btmp;
147 /* compare down to the same day */
149 if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
150 (result = (atmp->tm_mon - btmp->tm_mon)) == 0)
151 result = (atmp->tm_mday - btmp->tm_mday);
156 /* get rid of one-sided dst bias */
158 if(atmp->tm_isdst == 1 && !btmp->tm_isdst)
160 else if(btmp->tm_isdst == 1 && !atmp->tm_isdst)
163 /* compare the rest of the way */
165 if ((result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
166 (result = (atmp->tm_min - btmp->tm_min)) == 0)
167 result = atmp->tm_sec - btmp->tm_sec;
180 register int saved_seconds;
182 struct tm yourtm, mytm;
186 if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
187 normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
188 normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
189 normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
190 normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
191 while (yourtm.tm_mday <= 0) {
194 year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
197 i = mon_lengths[isleap(yourtm.tm_year +
198 TM_YEAR_BASE)][yourtm.tm_mon];
199 if (yourtm.tm_mday <= i)
202 if (++yourtm.tm_mon >= MONSPERYEAR) {
207 saved_seconds = yourtm.tm_sec;
210 ** Calculate the number of magnitude bits in a time_t
211 ** (this works regardless of whether time_t is
212 ** signed or unsigned, though lint complains if unsigned).
214 for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
217 ** If time_t is signed, then 0 is the median value,
218 ** if time_t is unsigned, then 1 << bits is median.
220 t = (t < 0) ? 0 : ((time_t) 1 << bits);
222 mytm = *localtime(&t);
223 dir = tmcomp(&mytm, &yourtm);
230 t -= (time_t) 1 << bits;
231 else t += (time_t) 1 << bits;
234 if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
240 *tmp = *localtime(&t);
252 if (tmp->tm_isdst > 1)
254 t = time2(tmp, &okay);
255 if (okay || tmp->tm_isdst < 0)