/* Convert a `struct tm' to a time_t value. Copyright (C) 1993-1999, 2002, 2003, 2004 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 #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 /* Some systems define `time_t' here. */ #include #include #if DEBUG # include # include # include /* Make it work even if the system's libc has its own mktime routine. */ # define mktime my_mktime #endif /* DEBUG */ /* 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 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 /* Verify a requirement at compile-time (unlike assert, which is runtime). */ #define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; } verify (time_t_is_integer, (time_t) 0.5 == 0); verify (twos_complement_arithmetic, -1 == ~1 + 1); verify (right_shift_propagates_sign, -1 >> 1 == -1); /* The code also assumes that signed integer overflow silently wraps around, but this assumption can't be stated without causing a diagnostic on some hosts. */ #define EPOCH_YEAR 1970 #define TM_YEAR_BASE 1900 verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0); /* Return 1 if YEAR + TM_YEAR_BASE is a leap year. */ static inline int leapyear (long int year) { /* Don't add YEAR to TM_YEAR_BASE, as that might overflow. Also, work even if YEAR is negative. */ return ((year & 3) == 0 && (year % 100 != 0 || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3))); } /* How many days come before each month (0-12). */ #ifndef _LIBC static #endif 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 } }; #ifndef _LIBC /* Portable standalone applications should supply a "time_r.h" that declares a POSIX-compliant localtime_r, for the benefit of older implementations that lack localtime_r or have a nonstandard one. See the gnulib time_r module for one way to implement this. */ # include "time_r.h" # undef __localtime_r # define __localtime_r localtime_r # define __mktime_internal mktime_internal #endif /* 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 (long int year, int yday, int hour, int min, int sec, const struct tm *tp) { if (!tp) return 1; else { verify (C99_integer_division, -1 / 2 == 0); /* 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; long int lyear_requested = year_requested; long int year = lyear_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[leapyear (year)] [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 (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, __localtime_r, &localtime_offset); } #ifdef weak_alias weak_alias (mktime, timelocal) #endif #ifdef _LIBC libc_hidden_def (mktime) libc_hidden_weak (timelocal) #endif #if DEBUG static int not_equal_tm (const struct tm *a, const 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 (const 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 (time_t tk, struct tm tmk, time_t tl, const struct tm *lt) { if (tk != tl || !lt || not_equal_tm (&tmk, lt)) { printf ("mktime ("); print_tm (lt); printf (")\nyields ("); print_tm (&tmk); printf (") == %ld, should be %ld\n", (long int) tk, (long int) tl); return 1; } return 0; } int main (int argc, char **argv) { int status = 0; struct tm tm, tmk, tml; struct tm *lt; time_t tk, tl, tl1; 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 int) 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; by < 0 ? to <= tl : tl <= to; tl = tl1) { 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 int) tl); status = 1; } tl1 = tl + by; if ((tl1 < tl) != (by < 0)) break; } else for (tl = from; by < 0 ? to <= tl : tl <= to; tl = tl1) { /* 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 int) tl); status = 1; } tl1 = tl + by; if ((tl1 < tl) != (by < 0)) break; } } 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 -Wall -W -O -g mktime.c -o mktime" End: */