mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-23 19:30:10 +00:00
b5ef404e08
2002-02-02 Paul Eggert <eggert@twinsun.com> * src/mktime.c [defined DEBUG && STDC_HEADERS]: Include <string.h>. (__mktime_internal): If no tm_isdst is requested, prefer solutions with tm_isdst > 0 when the requested time falls within a spring-forward gap [PR libc/2894].
537 lines
15 KiB
C
537 lines
15 KiB
C
/* Convert a `struct tm' to a time_t value.
|
||
Copyright (C) 1993, 94, 95, 96, 97, 98, 99 Free Software Foundation, Inc.
|
||
This file is part of the GNU C Library.
|
||
Contributed by Paul Eggert (eggert@twinsun.com).
|
||
|
||
The GNU C Library is free software; you can redistribute it and/or
|
||
modify it under the terms of the GNU Lesser General Public
|
||
License as published by the Free Software Foundation; either
|
||
version 2.1 of the License, or (at your option) any later version.
|
||
|
||
The GNU C Library is distributed in the hope that it will be useful,
|
||
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
Lesser General Public License for more details.
|
||
|
||
You should have received a copy of the GNU Lesser General Public
|
||
License along with the GNU C Library; if not, write to the Free
|
||
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
||
02111-1307 USA. */
|
||
|
||
/* Define this to have a standalone program to test this implementation of
|
||
mktime. */
|
||
/* #define DEBUG 1 */
|
||
|
||
#ifdef HAVE_CONFIG_H
|
||
# include <config.h>
|
||
#endif
|
||
|
||
#ifdef _LIBC
|
||
# define HAVE_LIMITS_H 1
|
||
# define STDC_HEADERS 1
|
||
#endif
|
||
|
||
/* Assume that leap seconds are possible, unless told otherwise.
|
||
If the host has a `zic' command with a `-L leapsecondfilename' option,
|
||
then it supports leap seconds; otherwise it probably doesn't. */
|
||
#ifndef LEAP_SECONDS_POSSIBLE
|
||
# define LEAP_SECONDS_POSSIBLE 1
|
||
#endif
|
||
|
||
#include <sys/types.h> /* Some systems define `time_t' here. */
|
||
#include <time.h>
|
||
|
||
#if HAVE_LIMITS_H
|
||
# include <limits.h>
|
||
#endif
|
||
|
||
#if DEBUG
|
||
# include <stdio.h>
|
||
# if STDC_HEADERS
|
||
# include <stdlib.h>
|
||
# include <string.h>
|
||
# endif
|
||
/* Make it work even if the system's libc has its own mktime routine. */
|
||
# define mktime my_mktime
|
||
#endif /* DEBUG */
|
||
|
||
#ifndef __P
|
||
# if defined __GNUC__ || (defined __STDC__ && __STDC__)
|
||
# define __P(args) args
|
||
# else
|
||
# define __P(args) ()
|
||
# endif /* GCC. */
|
||
#endif /* Not __P. */
|
||
|
||
#ifndef CHAR_BIT
|
||
# define CHAR_BIT 8
|
||
#endif
|
||
|
||
/* The extra casts work around common compiler bugs. */
|
||
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
|
||
/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
|
||
It is necessary at least when t == time_t. */
|
||
#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
|
||
? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
|
||
#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
|
||
|
||
#ifndef INT_MIN
|
||
# define INT_MIN TYPE_MINIMUM (int)
|
||
#endif
|
||
#ifndef INT_MAX
|
||
# define INT_MAX TYPE_MAXIMUM (int)
|
||
#endif
|
||
|
||
#ifndef TIME_T_MIN
|
||
# define TIME_T_MIN TYPE_MINIMUM (time_t)
|
||
#endif
|
||
#ifndef TIME_T_MAX
|
||
# define TIME_T_MAX TYPE_MAXIMUM (time_t)
|
||
#endif
|
||
|
||
#define TM_YEAR_BASE 1900
|
||
#define EPOCH_YEAR 1970
|
||
|
||
#ifndef __isleap
|
||
/* Nonzero if YEAR is a leap year (every 4 years,
|
||
except every 100th isn't, and every 400th is). */
|
||
# define __isleap(year) \
|
||
((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
|
||
#endif
|
||
|
||
/* How many days come before each month (0-12). */
|
||
const unsigned short int __mon_yday[2][13] =
|
||
{
|
||
/* Normal years. */
|
||
{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
|
||
/* Leap years. */
|
||
{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
|
||
};
|
||
|
||
|
||
#ifdef _LIBC
|
||
# define my_mktime_localtime_r __localtime_r
|
||
#else
|
||
/* If we're a mktime substitute in a GNU program, then prefer
|
||
localtime to localtime_r, since many localtime_r implementations
|
||
are buggy. */
|
||
static struct tm *
|
||
my_mktime_localtime_r (const time_t *t, struct tm *tp)
|
||
{
|
||
struct tm *l = localtime (t);
|
||
if (! l)
|
||
return 0;
|
||
*tp = *l;
|
||
return tp;
|
||
}
|
||
#endif /* ! _LIBC */
|
||
|
||
|
||
/* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP),
|
||
measured in seconds, ignoring leap seconds.
|
||
YEAR uses the same numbering as TM->tm_year.
|
||
All values are in range, except possibly YEAR.
|
||
If TP is null, return a nonzero value.
|
||
If overflow occurs, yield the low order bits of the correct answer. */
|
||
static time_t
|
||
ydhms_tm_diff (int year, int yday, int hour, int min, int sec,
|
||
const struct tm *tp)
|
||
{
|
||
if (!tp)
|
||
return 1;
|
||
else
|
||
{
|
||
/* Compute intervening leap days correctly even if year is negative.
|
||
Take care to avoid int overflow. time_t overflow is OK, since
|
||
only the low order bits of the correct time_t answer are needed.
|
||
Don't convert to time_t until after all divisions are done, since
|
||
time_t might be unsigned. */
|
||
int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3);
|
||
int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3);
|
||
int a100 = a4 / 25 - (a4 % 25 < 0);
|
||
int b100 = b4 / 25 - (b4 % 25 < 0);
|
||
int a400 = a100 >> 2;
|
||
int b400 = b100 >> 2;
|
||
int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
|
||
time_t years = year - (time_t) tp->tm_year;
|
||
time_t days = (365 * years + intervening_leap_days
|
||
+ (yday - tp->tm_yday));
|
||
return (60 * (60 * (24 * days + (hour - tp->tm_hour))
|
||
+ (min - tp->tm_min))
|
||
+ (sec - tp->tm_sec));
|
||
}
|
||
}
|
||
|
||
/* Use CONVERT to convert *T to a broken down time in *TP.
|
||
If *T is out of range for conversion, adjust it so that
|
||
it is the nearest in-range value and then convert that. */
|
||
static struct tm *
|
||
ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
|
||
time_t *t, struct tm *tp)
|
||
{
|
||
struct tm *r;
|
||
|
||
if (! (r = (*convert) (t, tp)) && *t)
|
||
{
|
||
time_t bad = *t;
|
||
time_t ok = 0;
|
||
struct tm tm;
|
||
|
||
/* BAD is a known unconvertible time_t, and OK is a known good one.
|
||
Use binary search to narrow the range between BAD and OK until
|
||
they differ by 1. */
|
||
while (bad != ok + (bad < 0 ? -1 : 1))
|
||
{
|
||
time_t mid = *t = (bad < 0
|
||
? bad + ((ok - bad) >> 1)
|
||
: ok + ((bad - ok) >> 1));
|
||
if ((r = (*convert) (t, tp)))
|
||
{
|
||
tm = *r;
|
||
ok = mid;
|
||
}
|
||
else
|
||
bad = mid;
|
||
}
|
||
|
||
if (!r && ok)
|
||
{
|
||
/* The last conversion attempt failed;
|
||
revert to the most recent successful attempt. */
|
||
*t = ok;
|
||
*tp = tm;
|
||
r = tp;
|
||
}
|
||
}
|
||
|
||
return r;
|
||
}
|
||
|
||
|
||
/* Convert *TP to a time_t value, inverting
|
||
the monotonic and mostly-unit-linear conversion function CONVERT.
|
||
Use *OFFSET to keep track of a guess at the offset of the result,
|
||
compared to what the result would be for UTC without leap seconds.
|
||
If *OFFSET's guess is correct, only one CONVERT call is needed. */
|
||
time_t
|
||
__mktime_internal (struct tm *tp,
|
||
struct tm *(*convert) (const time_t *, struct tm *),
|
||
time_t *offset)
|
||
{
|
||
time_t t, dt, t0, t1, t2;
|
||
struct tm tm;
|
||
|
||
/* The maximum number of probes (calls to CONVERT) should be enough
|
||
to handle any combinations of time zone rule changes, solar time,
|
||
leap seconds, and oscillations around a spring-forward gap.
|
||
POSIX.1 prohibits leap seconds, but some hosts have them anyway. */
|
||
int remaining_probes = 6;
|
||
|
||
/* Time requested. Copy it in case CONVERT modifies *TP; this can
|
||
occur if TP is localtime's returned value and CONVERT is localtime. */
|
||
int sec = tp->tm_sec;
|
||
int min = tp->tm_min;
|
||
int hour = tp->tm_hour;
|
||
int mday = tp->tm_mday;
|
||
int mon = tp->tm_mon;
|
||
int year_requested = tp->tm_year;
|
||
int isdst = tp->tm_isdst;
|
||
|
||
/* 1 if the previous probe was DST. */
|
||
int dst2;
|
||
|
||
/* Ensure that mon is in range, and set year accordingly. */
|
||
int mon_remainder = mon % 12;
|
||
int negative_mon_remainder = mon_remainder < 0;
|
||
int mon_years = mon / 12 - negative_mon_remainder;
|
||
int year = year_requested + mon_years;
|
||
|
||
/* The other values need not be in range:
|
||
the remaining code handles minor overflows correctly,
|
||
assuming int and time_t arithmetic wraps around.
|
||
Major overflows are caught at the end. */
|
||
|
||
/* Calculate day of year from year, month, and day of month.
|
||
The result need not be in range. */
|
||
int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
|
||
[mon_remainder + 12 * negative_mon_remainder])
|
||
+ mday - 1);
|
||
|
||
int sec_requested = sec;
|
||
#if LEAP_SECONDS_POSSIBLE
|
||
/* Handle out-of-range seconds specially,
|
||
since ydhms_tm_diff assumes every minute has 60 seconds. */
|
||
if (sec < 0)
|
||
sec = 0;
|
||
if (59 < sec)
|
||
sec = 59;
|
||
#endif
|
||
|
||
/* Invert CONVERT by probing. First assume the same offset as last time.
|
||
Then repeatedly use the error to improve the guess. */
|
||
|
||
tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE;
|
||
tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
|
||
t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
|
||
|
||
for (t = t1 = t2 = t0 + *offset, dst2 = 0;
|
||
(dt = ydhms_tm_diff (year, yday, hour, min, sec,
|
||
ranged_convert (convert, &t, &tm)));
|
||
t1 = t2, t2 = t, t += dt, dst2 = tm.tm_isdst != 0)
|
||
if (t == t1 && t != t2
|
||
&& (tm.tm_isdst < 0
|
||
|| (isdst < 0
|
||
? dst2 <= (tm.tm_isdst != 0)
|
||
: (isdst != 0) != (tm.tm_isdst != 0))))
|
||
/* We can't possibly find a match, as we are oscillating
|
||
between two values. The requested time probably falls
|
||
within a spring-forward gap of size DT. Follow the common
|
||
practice in this case, which is to return a time that is DT
|
||
away from the requested time, preferring a time whose
|
||
tm_isdst differs from the requested value. (If no tm_isdst
|
||
was requested and only one of the two values has a nonzero
|
||
tm_isdst, prefer that value.) In practice, this is more
|
||
useful than returning -1. */
|
||
break;
|
||
else if (--remaining_probes == 0)
|
||
return -1;
|
||
|
||
/* If we have a match, check whether tm.tm_isdst has the requested
|
||
value, if any. */
|
||
if (dt == 0 && isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)
|
||
{
|
||
/* tm.tm_isdst has the wrong value. Look for a neighboring
|
||
time with the right value, and use its UTC offset.
|
||
Heuristic: probe the previous three calendar quarters (approximately),
|
||
looking for the desired isdst. This isn't perfect,
|
||
but it's good enough in practice. */
|
||
int quarter = 7889238; /* seconds per average 1/4 Gregorian year */
|
||
int i;
|
||
|
||
/* If we're too close to the time_t limit, look in future quarters. */
|
||
if (t < TIME_T_MIN + 3 * quarter)
|
||
quarter = -quarter;
|
||
|
||
for (i = 1; i <= 3; i++)
|
||
{
|
||
time_t ot = t - i * quarter;
|
||
struct tm otm;
|
||
ranged_convert (convert, &ot, &otm);
|
||
if (otm.tm_isdst == isdst)
|
||
{
|
||
/* We found the desired tm_isdst.
|
||
Extrapolate back to the desired time. */
|
||
t = ot + ydhms_tm_diff (year, yday, hour, min, sec, &otm);
|
||
ranged_convert (convert, &t, &tm);
|
||
break;
|
||
}
|
||
}
|
||
}
|
||
|
||
*offset = t - t0;
|
||
|
||
#if LEAP_SECONDS_POSSIBLE
|
||
if (sec_requested != tm.tm_sec)
|
||
{
|
||
/* Adjust time to reflect the tm_sec requested, not the normalized value.
|
||
Also, repair any damage from a false match due to a leap second. */
|
||
t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60);
|
||
if (! (*convert) (&t, &tm))
|
||
return -1;
|
||
}
|
||
#endif
|
||
|
||
if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
|
||
{
|
||
/* time_t isn't large enough to rule out overflows in ydhms_tm_diff,
|
||
so check for major overflows. A gross check suffices,
|
||
since if t has overflowed, it is off by a multiple of
|
||
TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of
|
||
the difference that is bounded by a small value. */
|
||
|
||
double dyear = (double) year_requested + mon_years - tm.tm_year;
|
||
double dday = 366 * dyear + mday;
|
||
double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested;
|
||
|
||
/* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce
|
||
correct results, ie., it erroneously gives a positive value
|
||
of 715827882. Setting a variable first then doing math on it
|
||
seems to work. (ghazi@caip.rutgers.edu) */
|
||
|
||
const time_t time_t_max = TIME_T_MAX;
|
||
const time_t time_t_min = TIME_T_MIN;
|
||
|
||
if (time_t_max / 3 - time_t_min / 3 < (dsec < 0 ? - dsec : dsec))
|
||
return -1;
|
||
}
|
||
|
||
*tp = tm;
|
||
return t;
|
||
}
|
||
|
||
|
||
static time_t localtime_offset;
|
||
|
||
/* Convert *TP to a time_t value. */
|
||
time_t
|
||
mktime (tp)
|
||
struct tm *tp;
|
||
{
|
||
#ifdef _LIBC
|
||
/* POSIX.1 8.1.1 requires that whenever mktime() is called, the
|
||
time zone names contained in the external variable `tzname' shall
|
||
be set as if the tzset() function had been called. */
|
||
__tzset ();
|
||
#endif
|
||
|
||
return __mktime_internal (tp, my_mktime_localtime_r, &localtime_offset);
|
||
}
|
||
|
||
#ifdef weak_alias
|
||
weak_alias (mktime, timelocal)
|
||
#endif
|
||
|
||
#if DEBUG
|
||
|
||
static int
|
||
not_equal_tm (a, b)
|
||
struct tm *a;
|
||
struct tm *b;
|
||
{
|
||
return ((a->tm_sec ^ b->tm_sec)
|
||
| (a->tm_min ^ b->tm_min)
|
||
| (a->tm_hour ^ b->tm_hour)
|
||
| (a->tm_mday ^ b->tm_mday)
|
||
| (a->tm_mon ^ b->tm_mon)
|
||
| (a->tm_year ^ b->tm_year)
|
||
| (a->tm_mday ^ b->tm_mday)
|
||
| (a->tm_yday ^ b->tm_yday)
|
||
| (a->tm_isdst ^ b->tm_isdst));
|
||
}
|
||
|
||
static void
|
||
print_tm (tp)
|
||
struct tm *tp;
|
||
{
|
||
if (tp)
|
||
printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
|
||
tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
|
||
tp->tm_hour, tp->tm_min, tp->tm_sec,
|
||
tp->tm_yday, tp->tm_wday, tp->tm_isdst);
|
||
else
|
||
printf ("0");
|
||
}
|
||
|
||
static int
|
||
check_result (tk, tmk, tl, lt)
|
||
time_t tk;
|
||
struct tm tmk;
|
||
time_t tl;
|
||
struct tm *lt;
|
||
{
|
||
if (tk != tl || !lt || not_equal_tm (&tmk, lt))
|
||
{
|
||
printf ("mktime (");
|
||
print_tm (&tmk);
|
||
printf (")\nyields (");
|
||
print_tm (lt);
|
||
printf (") == %ld, should be %ld\n", (long) tl, (long) tk);
|
||
return 1;
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
int
|
||
main (argc, argv)
|
||
int argc;
|
||
char **argv;
|
||
{
|
||
int status = 0;
|
||
struct tm tm, tmk, tml;
|
||
struct tm *lt;
|
||
time_t tk, tl;
|
||
char trailer;
|
||
|
||
if ((argc == 3 || argc == 4)
|
||
&& (sscanf (argv[1], "%d-%d-%d%c",
|
||
&tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
|
||
== 3)
|
||
&& (sscanf (argv[2], "%d:%d:%d%c",
|
||
&tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
|
||
== 3))
|
||
{
|
||
tm.tm_year -= TM_YEAR_BASE;
|
||
tm.tm_mon--;
|
||
tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
|
||
tmk = tm;
|
||
tl = mktime (&tmk);
|
||
lt = localtime (&tl);
|
||
if (lt)
|
||
{
|
||
tml = *lt;
|
||
lt = &tml;
|
||
}
|
||
printf ("mktime returns %ld == ", (long) tl);
|
||
print_tm (&tmk);
|
||
printf ("\n");
|
||
status = check_result (tl, tmk, tl, lt);
|
||
}
|
||
else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
|
||
{
|
||
time_t from = atol (argv[1]);
|
||
time_t by = atol (argv[2]);
|
||
time_t to = atol (argv[3]);
|
||
|
||
if (argc == 4)
|
||
for (tl = from; tl <= to; tl += by)
|
||
{
|
||
lt = localtime (&tl);
|
||
if (lt)
|
||
{
|
||
tmk = tml = *lt;
|
||
tk = mktime (&tmk);
|
||
status |= check_result (tk, tmk, tl, tml);
|
||
}
|
||
else
|
||
{
|
||
printf ("localtime (%ld) yields 0\n", (long) tl);
|
||
status = 1;
|
||
}
|
||
}
|
||
else
|
||
for (tl = from; tl <= to; tl += by)
|
||
{
|
||
/* Null benchmark. */
|
||
lt = localtime (&tl);
|
||
if (lt)
|
||
{
|
||
tmk = tml = *lt;
|
||
tk = tl;
|
||
status |= check_result (tk, tmk, tl, tml);
|
||
}
|
||
else
|
||
{
|
||
printf ("localtime (%ld) yields 0\n", (long) tl);
|
||
status = 1;
|
||
}
|
||
}
|
||
}
|
||
else
|
||
printf ("Usage:\
|
||
\t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
|
||
\t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
|
||
\t%s FROM BY TO - # Do not test those values (for benchmark).\n",
|
||
argv[0], argv[0], argv[0]);
|
||
|
||
return status;
|
||
}
|
||
|
||
#endif /* DEBUG */
|
||
|
||
/*
|
||
Local Variables:
|
||
compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"
|
||
End:
|
||
*/
|