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glibc/time/mktime.c
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/* Convert a `struct tm' to a time_t value. | |
Copyright (C) 1993-1999, 2002 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; | |
/* Only years after 1970 are defined. | |
If year is 69, it might still be representable due to | |
timezone differences. */ | |
if (year < 69) | |
return -1; | |
#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; | |
} | |
if (year == 69) | |
{ | |
/* If year was 69, need to check whether the time was representable | |
or not. */ | |
if (t < 0 || t > 2 * 24 * 60 * 60) | |
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: | |
*/ |