/contrib/ntp/libntp/mktime.c
https://bitbucket.org/freebsd/freebsd-head/ · C · 303 lines · 190 code · 33 blank · 80 comment · 49 complexity · a97d4114ae0271994ad7c6bc7e475de4 MD5 · raw file
- /*
- * Copyright (c) 1987, 1989 Regents of the University of California.
- * All rights reserved.
- *
- * This code is derived from software contributed to Berkeley by
- * Arthur David Olson of the National Cancer Institute.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- * This product includes software developed by the University of
- * California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE. */
- /*static char *sccsid = "from: @(#)ctime.c 5.26 (Berkeley) 2/23/91";*/
- /*
- * This implementation of mktime is lifted straight from the NetBSD (BSD 4.4)
- * version. I modified it slightly to divorce it from the internals of the
- * ctime library. Thus this version can't use details of the internal
- * timezone state file to figure out strange unnormalized struct tm values,
- * as might result from someone doing date math on the tm struct then passing
- * it to mktime.
- *
- * It just does as well as it can at normalizing the tm input, then does a
- * binary search of the time space using the system's localtime() function.
- *
- * The original binary search was defective in that it didn't consider the
- * setting of tm_isdst when comparing tm values, causing the search to be
- * flubbed for times near the dst/standard time changeover. The original
- * code seems to make up for this by grubbing through the timezone info
- * whenever the binary search barfed. Since I don't have that luxury in
- * portable code, I have to take care of tm_isdst in the comparison routine.
- * This requires knowing how many minutes offset dst is from standard time.
- *
- * So, if you live somewhere in the world where dst is not 60 minutes offset,
- * and your vendor doesn't supply mktime(), you'll have to edit this variable
- * by hand. Sorry about that.
- */
- #include "ntp_machine.h"
- #if !defined(HAVE_MKTIME) || !defined(HAVE_TIMEGM)
- #ifndef DSTMINUTES
- #define DSTMINUTES 60
- #endif
- #define FALSE 0
- #define TRUE 1
- /* some constants from tzfile.h */
- #define SECSPERMIN 60
- #define MINSPERHOUR 60
- #define HOURSPERDAY 24
- #define DAYSPERWEEK 7
- #define DAYSPERNYEAR 365
- #define DAYSPERLYEAR 366
- #define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
- #define SECSPERDAY ((long) SECSPERHOUR * HOURSPERDAY)
- #define MONSPERYEAR 12
- #define TM_YEAR_BASE 1900
- #define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
- static int mon_lengths[2][MONSPERYEAR] = {
- { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
- { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
- };
- static int year_lengths[2] = {
- DAYSPERNYEAR, DAYSPERLYEAR
- };
- /*
- ** Adapted from code provided by Robert Elz, who writes:
- ** The "best" way to do mktime I think is based on an idea of Bob
- ** Kridle's (so its said...) from a long time ago. (mtxinu!kridle now).
- ** It does a binary search of the time_t space. Since time_t's are
- ** just 32 bits, its a max of 32 iterations (even at 64 bits it
- ** would still be very reasonable).
- */
- #ifndef WRONG
- #define WRONG (-1)
- #endif /* !defined WRONG */
- static void
- normalize(
- int * tensptr,
- int * unitsptr,
- int base
- )
- {
- if (*unitsptr >= base) {
- *tensptr += *unitsptr / base;
- *unitsptr %= base;
- } else if (*unitsptr < 0) {
- --*tensptr;
- *unitsptr += base;
- if (*unitsptr < 0) {
- *tensptr -= 1 + (-*unitsptr) / base;
- *unitsptr = base - (-*unitsptr) % base;
- }
- }
- }
- static struct tm *
- mkdst(
- struct tm * tmp
- )
- {
- /* jds */
- static struct tm tmbuf;
- tmbuf = *tmp;
- tmbuf.tm_isdst = 1;
- tmbuf.tm_min += DSTMINUTES;
- normalize(&tmbuf.tm_hour, &tmbuf.tm_min, MINSPERHOUR);
- return &tmbuf;
- }
- static int
- tmcomp(
- register struct tm * atmp,
- register struct tm * btmp
- )
- {
- register int result;
- /* compare down to the same day */
- if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
- (result = (atmp->tm_mon - btmp->tm_mon)) == 0)
- result = (atmp->tm_mday - btmp->tm_mday);
- if(result != 0)
- return result;
- /* get rid of one-sided dst bias */
- if(atmp->tm_isdst == 1 && !btmp->tm_isdst)
- btmp = mkdst(btmp);
- else if(btmp->tm_isdst == 1 && !atmp->tm_isdst)
- atmp = mkdst(atmp);
- /* compare the rest of the way */
- if ((result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
- (result = (atmp->tm_min - btmp->tm_min)) == 0)
- result = atmp->tm_sec - btmp->tm_sec;
- return result;
- }
- static time_t
- time2(
- struct tm * tmp,
- int * okayp,
- int usezn
- )
- {
- register int dir;
- register int bits;
- register int i;
- register int saved_seconds;
- time_t t;
- struct tm yourtm, mytm;
- *okayp = FALSE;
- yourtm = *tmp;
- if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
- normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
- normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
- normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
- normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
- while (yourtm.tm_mday <= 0) {
- --yourtm.tm_year;
- yourtm.tm_mday +=
- year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
- }
- for ( ; ; ) {
- i = mon_lengths[isleap(yourtm.tm_year +
- TM_YEAR_BASE)][yourtm.tm_mon];
- if (yourtm.tm_mday <= i)
- break;
- yourtm.tm_mday -= i;
- if (++yourtm.tm_mon >= MONSPERYEAR) {
- yourtm.tm_mon = 0;
- ++yourtm.tm_year;
- }
- }
- saved_seconds = yourtm.tm_sec;
- yourtm.tm_sec = 0;
- /*
- ** Calculate the number of magnitude bits in a time_t
- ** (this works regardless of whether time_t is
- ** signed or unsigned, though lint complains if unsigned).
- */
- for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
- ;
- /*
- ** If time_t is signed, then 0 is the median value,
- ** if time_t is unsigned, then 1 << bits is median.
- */
- t = (t < 0) ? 0 : ((time_t) 1 << bits);
- for ( ; ; ) {
- if (usezn)
- mytm = *localtime(&t);
- else
- mytm = *gmtime(&t);
- dir = tmcomp(&mytm, &yourtm);
- if (dir != 0) {
- if (bits-- < 0)
- return WRONG;
- if (bits < 0)
- --t;
- else if (dir > 0)
- t -= (time_t) 1 << bits;
- else t += (time_t) 1 << bits;
- continue;
- }
- if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
- break;
- return WRONG;
- }
- t += saved_seconds;
- if (usezn)
- *tmp = *localtime(&t);
- else
- *tmp = *gmtime(&t);
- *okayp = TRUE;
- return t;
- }
- #else
- int mktime_bs;
- #endif /* !HAVE_MKTIME || !HAVE_TIMEGM */
- #ifndef HAVE_MKTIME
- static time_t
- time1(
- struct tm * tmp
- )
- {
- register time_t t;
- int okay;
- if (tmp->tm_isdst > 1)
- tmp->tm_isdst = 1;
- t = time2(tmp, &okay, 1);
- if (okay || tmp->tm_isdst < 0)
- return t;
- return WRONG;
- }
- time_t
- mktime(
- struct tm * tmp
- )
- {
- return time1(tmp);
- }
- #endif /* !HAVE_MKTIME */
- #ifndef HAVE_TIMEGM
- time_t
- timegm(
- struct tm * tmp
- )
- {
- register time_t t;
- int okay;
- tmp->tm_isdst = 0;
- t = time2(tmp, &okay, 0);
- if (okay || tmp->tm_isdst < 0)
- return t;
- return WRONG;
- }
- #endif /* !HAVE_TIMEGM */