NetBSD/dist/ntp/libntp/mktime.c

285 lines
7.9 KiB
C

/* $NetBSD: mktime.c,v 1.1.1.1 2000/03/29 12:38:49 simonb Exp $ */
/*
* 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";*/
/*static char *rcsid = "mktime.c,v 1.1.1.3 1998/11/15 19:23:34 kardel RELEASE_19990228_A";*/
/*
* 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.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#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)
#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#include <time.h>
extern time_t time();
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
)
{
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 ( ; ; ) {
mytm = *localtime(&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;
*tmp = *localtime(&t);
*okayp = TRUE;
return t;
}
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);
if (okay || tmp->tm_isdst < 0)
return t;
return WRONG;
}
time_t
mktime(
struct tm * tmp
)
{
return time1(tmp);
}