/* Convert a `struct tm' to a time_t value. Copyright (C) 1993-1999, 2002-2005, 2006, 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Paul Eggert <eggert@twinsun.com>. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. This program 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ /* Define this to have a standalone program to test this implementation of mktime. */ /* #define DEBUG 1 */ #ifndef _LIBC # include <config.h> #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 <time.h> #include <limits.h> #include <string.h> /* For the real memcpy prototype. */ #if DEBUG # include <stdio.h> # include <stdlib.h> /* Make it work even if the system's libc has its own mktime routine. */ # define mktime my_mktime #endif /* DEBUG */ /* Shift A right by B bits portably, by dividing A by 2**B and truncating towards minus infinity. A and B should be free of side effects, and B should be in the range 0 <= B <= INT_BITS - 2, where INT_BITS is the number of useful bits in an int. GNU code can assume that INT_BITS is at least 32. ISO C99 says that A >> B is implementation-defined if A < 0. Some implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift right in the usual way when A < 0, so SHR falls back on division if ordinary A >> B doesn't seem to be the usual signed shift. */ #define SHR(a, b) \ (-1 >> 1 == -1 \ ? (a) >> (b) \ : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0)) /* The extra casts in the following macros work around compiler bugs, e.g., in Cray C 5.0.3.0. */ /* True if the arithmetic type T is an integer type. bool counts as an integer. */ #define TYPE_IS_INTEGER(t) ((t) 1.5 == 1) /* True if negative values of the signed integer type T use two's complement, ones' complement, or signed magnitude representation, respectively. Much GNU code assumes two's complement, but some people like to be portable to all possible C hosts. */ #define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1) #define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0) #define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1) /* True if the arithmetic type T is signed. */ #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1)) /* The maximum and minimum values for the integer type T. These macros have undefined behavior if T is signed and has padding bits. If this is a problem for you, please let us know how to fix it for your host. */ #define TYPE_MINIMUM(t) \ ((t) (! TYPE_SIGNED (t) \ ? (t) 0 \ : TYPE_SIGNED_MAGNITUDE (t) \ ? ~ (t) 0 \ : ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))) #define TYPE_MAXIMUM(t) \ ((t) (! TYPE_SIGNED (t) \ ? (t) -1 \ : ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1)))) #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 TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1) /* 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, TYPE_IS_INTEGER (time_t)); verify (twos_complement_arithmetic, TYPE_TWOS_COMPLEMENT (int)); /* 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.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. */ # undef __localtime_r # define __localtime_r localtime_r # define __mktime_internal mktime_internal #endif /* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) - (YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks were not adjusted between the time stamps. The YEAR values uses the same numbering as TP->tm_year. Values need not be in the usual range. However, YEAR1 must not be less than 2 * INT_MIN or greater than 2 * INT_MAX. The result may overflow. It is the caller's responsibility to detect overflow. */ static inline time_t ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1, int year0, int yday0, int hour0, int min0, int sec0) { verify (C99_integer_division, -1 / 2 == 0); verify (long_int_year_and_yday_are_wide_enough, INT_MAX <= LONG_MAX / 2 || TIME_T_MAX <= UINT_MAX); /* Compute intervening leap days correctly even if year is negative. Take care to avoid integer overflow here. */ int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3); int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3); int a100 = a4 / 25 - (a4 % 25 < 0); int b100 = b4 / 25 - (b4 % 25 < 0); int a400 = SHR (a100, 2); int b400 = SHR (b100, 2); int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); /* Compute the desired time in time_t precision. Overflow might occur here. */ time_t tyear1 = year1; time_t years = tyear1 - year0; time_t days = 365 * years + yday1 - yday0 + intervening_leap_days; time_t hours = 24 * days + hour1 - hour0; time_t minutes = 60 * hours + min1 - min0; time_t seconds = 60 * minutes + sec1 - sec0; return seconds; } /* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC), assuming that *T corresponds to *TP and that no clock adjustments occurred between *TP and the desired time. If TP is null, return a value not equal to *T; this avoids false matches. If overflow occurs, yield the minimal or maximal value, except do not yield a value equal to *T. */ static time_t guess_time_tm (long int year, long int yday, int hour, int min, int sec, const time_t *t, const struct tm *tp) { if (tp) { time_t d = ydhms_diff (year, yday, hour, min, sec, tp->tm_year, tp->tm_yday, tp->tm_hour, tp->tm_min, tp->tm_sec); time_t t1 = *t + d; if ((t1 < *t) == (TYPE_SIGNED (time_t) ? d < 0 : TIME_T_MAX / 2 < d)) return t1; } /* Overflow occurred one way or another. Return the nearest result that is actually in range, except don't report a zero difference if the actual difference is nonzero, as that would cause a false match; and don't oscillate between two values, as that would confuse the spring-forward gap detector. */ return (*t < TIME_T_MIDPOINT ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN) : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX)); } /* 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 = convert (t, tp); if (!r && *t) { time_t bad = *t; time_t ok = 0; /* 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)); r = convert (t, tp); if (r) ok = mid; else bad = mid; } if (!r && ok) { /* The last conversion attempt failed; revert to the most recent successful attempt. */ *t = ok; r = convert (t, 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. This function is external because it is used also by timegm.c. */ time_t __mktime_internal (struct tm *tp, struct tm *(*convert) (const time_t *, struct tm *), time_t *offset) { time_t t, gt, 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 mon_yday = ((__mon_yday[leapyear (year)] [mon_remainder + 12 * negative_mon_remainder]) - 1); long int lmday = mday; long int yday = mon_yday + lmday; time_t guessed_offset = *offset; 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; } /* Invert CONVERT by probing. First assume the same offset as last time. */ t0 = ydhms_diff (year, yday, hour, min, sec, EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset); if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) { /* time_t isn't large enough to rule out overflows, so check for major overflows. A gross check suffices, since if t0 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. */ /* Approximate log base 2 of the number of time units per biennium. A biennium is 2 years; use this unit instead of years to avoid integer overflow. For example, 2 average Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds, which is 63113904 seconds, and rint (log2 (63113904)) is 26. */ int ALOG2_SECONDS_PER_BIENNIUM = 26; int ALOG2_MINUTES_PER_BIENNIUM = 20; int ALOG2_HOURS_PER_BIENNIUM = 14; int ALOG2_DAYS_PER_BIENNIUM = 10; int LOG2_YEARS_PER_BIENNIUM = 1; int approx_requested_biennia = (SHR (year_requested, LOG2_YEARS_PER_BIENNIUM) - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM) + SHR (mday, ALOG2_DAYS_PER_BIENNIUM) + SHR (hour, ALOG2_HOURS_PER_BIENNIUM) + SHR (min, ALOG2_MINUTES_PER_BIENNIUM) + (LEAP_SECONDS_POSSIBLE ? 0 : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM))); int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM); int diff = approx_biennia - approx_requested_biennia; int abs_diff = diff < 0 ? - diff : diff; /* IRIX 4.0.5 cc miscaculates TIME_T_MIN / 3: it erroneously gives a positive value of 715827882. Setting a variable first then doing math on it seems to work. (ghazi@caip.rutgers.edu) */ time_t time_t_max = TIME_T_MAX; time_t time_t_min = TIME_T_MIN; time_t overflow_threshold = (time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM; if (overflow_threshold < abs_diff) { /* Overflow occurred. Try repairing it; this might work if the time zone offset is enough to undo the overflow. */ time_t repaired_t0 = -1 - t0; approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM); diff = approx_biennia - approx_requested_biennia; abs_diff = diff < 0 ? - diff : diff; if (overflow_threshold < abs_diff) return -1; guessed_offset += repaired_t0 - t0; t0 = repaired_t0; } } /* Repeatedly use the error to improve the guess. */ for (t = t1 = t2 = t0, dst2 = 0; (gt = guess_time_tm (year, yday, hour, min, sec, &t, ranged_convert (convert, &t, &tm)), t != gt); t1 = t2, t2 = t, t = gt, 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 GT - T. Follow the common practice in this case, which is to return a time that is GT - T 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. */ goto offset_found; else if (--remaining_probes == 0) return -1; /* We have a match. Check whether tm.tm_isdst has the requested value, if any. */ if (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 adjacent timestamps in both directions, looking for the desired isdst. This should work for all real time zone histories in the tz database. */ /* Distance between probes when looking for a DST boundary. In tzdata2003a, the shortest period of DST is 601200 seconds (e.g., America/Recife starting 2000-10-08 01:00), and the shortest period of non-DST surrounded by DST is 694800 seconds (Africa/Tunis starting 1943-04-17 01:00). Use the minimum of these two values, so we don't miss these short periods when probing. */ int stride = 601200; /* The longest period of DST in tzdata2003a is 536454000 seconds (e.g., America/Jujuy starting 1946-10-01 01:00). The longest period of non-DST is much longer, but it makes no real sense to search for more than a year of non-DST, so use the DST max. */ int duration_max = 536454000; /* Search in both directions, so the maximum distance is half the duration; add the stride to avoid off-by-1 problems. */ int delta_bound = duration_max / 2 + stride; int delta, direction; for (delta = stride; delta < delta_bound; delta += stride) for (direction = -1; direction <= 1; direction += 2) { time_t ot = t + delta * direction; if ((ot < t) == (direction < 0)) { 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 = guess_time_tm (year, yday, hour, min, sec, &ot, &otm); ranged_convert (convert, &t, &tm); goto offset_found; } } } } offset_found: *offset = guessed_offset + t - t0; if (LEAP_SECONDS_POSSIBLE && 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. */ int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec; t1 = t + sec_requested; t2 = t1 + sec_adjustment; if (((t1 < t) != (sec_requested < 0)) | ((t2 < t1) != (sec_adjustment < 0)) | ! convert (&t2, &tm)) return -1; t = t2; } *tp = tm; return t; } /* FIXME: This should use a signed type wide enough to hold any UTC offset in seconds. 'int' should be good enough for GNU code. We can't fix this unilaterally though, as other modules invoke __mktime_internal. */ 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_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: */