summaryrefslogtreecommitdiffstats
path: root/lib/mktime.c
diff options
context:
space:
mode:
Diffstat (limited to 'lib/mktime.c')
-rw-r--r--lib/mktime.c578
1 files changed, 578 insertions, 0 deletions
diff --git a/lib/mktime.c b/lib/mktime.c
new file mode 100644
index 0000000..7dc9d67
--- /dev/null
+++ b/lib/mktime.c
@@ -0,0 +1,578 @@
+/* Convert a 'struct tm' to a time_t value.
+ Copyright (C) 1993-2022 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, see
+ <https://www.gnu.org/licenses/>. */
+
+/* The following macros influence what gets defined when this file is compiled:
+
+ Macro/expression Which gnulib module This compilation unit
+ should define
+
+ _LIBC (glibc proper) mktime
+
+ NEED_MKTIME_WORKING mktime rpl_mktime
+ || NEED_MKTIME_WINDOWS
+
+ NEED_MKTIME_INTERNAL mktime-internal mktime_internal
+ */
+
+#ifndef _LIBC
+# include <libc-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 <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <intprops.h>
+#include <verify.h>
+
+#ifndef NEED_MKTIME_INTERNAL
+# define NEED_MKTIME_INTERNAL 0
+#endif
+#ifndef NEED_MKTIME_WINDOWS
+# define NEED_MKTIME_WINDOWS 0
+#endif
+#ifndef NEED_MKTIME_WORKING
+# define NEED_MKTIME_WORKING 0
+#endif
+
+#include "mktime-internal.h"
+
+#if !defined _LIBC && (NEED_MKTIME_WORKING || NEED_MKTIME_WINDOWS)
+static void
+my_tzset (void)
+{
+# if NEED_MKTIME_WINDOWS
+ /* Rectify the value of the environment variable TZ.
+ There are four possible kinds of such values:
+ - Traditional US time zone names, e.g. "PST8PDT". Syntax: see
+ <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/tzset>
+ - Time zone names based on geography, that contain one or more
+ slashes, e.g. "Europe/Moscow".
+ - Time zone names based on geography, without slashes, e.g.
+ "Singapore".
+ - Time zone names that contain explicit DST rules. Syntax: see
+ <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03>
+ The Microsoft CRT understands only the first kind. It produces incorrect
+ results if the value of TZ is of the other kinds.
+ But in a Cygwin environment, /etc/profile.d/tzset.sh sets TZ to a value
+ of the second kind for most geographies, or of the first kind in a few
+ other geographies. If it is of the second kind, neutralize it. For the
+ Microsoft CRT, an absent or empty TZ means the time zone that the user
+ has set in the Windows Control Panel.
+ If the value of TZ is of the third or fourth kind -- Cygwin programs
+ understand these syntaxes as well --, it does not matter whether we
+ neutralize it or not, since these values occur only when a Cygwin user
+ has set TZ explicitly; this case is 1. rare and 2. under the user's
+ responsibility. */
+ const char *tz = getenv ("TZ");
+ if (tz != NULL && strchr (tz, '/') != NULL)
+ _putenv ("TZ=");
+# else
+ tzset ();
+# endif
+}
+# undef __tzset
+# define __tzset() my_tzset ()
+#endif
+
+#if defined _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_INTERNAL
+
+/* A signed type that can represent an integer number of years
+ multiplied by four times the number of seconds in a year. It is
+ needed when converting a tm_year value times the number of seconds
+ in a year. The factor of four comes because these products need
+ to be subtracted from each other, and sometimes with an offset
+ added to them, and then with another timestamp added, without
+ worrying about overflow.
+
+ Much of the code uses long_int to represent __time64_t values, to
+ lessen the hassle of dealing with platforms where __time64_t is
+ unsigned, and because long_int should suffice to represent all
+ __time64_t values that mktime can generate even on platforms where
+ __time64_t is wider than the int components of struct tm. */
+
+#if INT_MAX <= LONG_MAX / 4 / 366 / 24 / 60 / 60
+typedef long int long_int;
+#else
+typedef long long int long_int;
+#endif
+verify (INT_MAX <= TYPE_MAXIMUM (long_int) / 4 / 366 / 24 / 60 / 60);
+
+/* Shift A right by B bits portably, by dividing A by 2**B and
+ truncating towards minus infinity. B should be in the range 0 <= B
+ <= LONG_INT_BITS - 2, where LONG_INT_BITS is the number of useful
+ bits in a long_int. LONG_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. */
+
+static long_int
+shr (long_int a, int b)
+{
+ long_int one = 1;
+ return (-one >> 1 == -1
+ ? a >> b
+ : (a + (a < 0)) / (one << b) - (a < 0));
+}
+
+/* Bounds for the intersection of __time64_t and long_int. */
+
+static long_int const mktime_min
+ = ((TYPE_SIGNED (__time64_t)
+ && TYPE_MINIMUM (__time64_t) < TYPE_MINIMUM (long_int))
+ ? TYPE_MINIMUM (long_int) : TYPE_MINIMUM (__time64_t));
+static long_int const mktime_max
+ = (TYPE_MAXIMUM (long_int) < TYPE_MAXIMUM (__time64_t)
+ ? TYPE_MAXIMUM (long_int) : TYPE_MAXIMUM (__time64_t));
+
+#define EPOCH_YEAR 1970
+#define TM_YEAR_BASE 1900
+verify (TM_YEAR_BASE % 100 == 0);
+
+/* Is YEAR + TM_YEAR_BASE a leap year? */
+static bool
+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 }
+ };
+
+
+/* Do the values A and B differ according to the rules for tm_isdst?
+ A and B differ if one is zero and the other positive. */
+static bool
+isdst_differ (int a, int b)
+{
+ return (!a != !b) && (0 <= a) && (0 <= b);
+}
+
+/* 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 timestamps.
+
+ The YEAR values uses the same numbering as TP->tm_year. Values
+ need not be in the usual range. However, YEAR1 - YEAR0 must not
+ overflow even when multiplied by three times the number of seconds
+ in a year, and likewise for YDAY1 - YDAY0 and three times the
+ number of seconds in a day. */
+
+static long_int
+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 (-1 / 2 == 0);
+
+ /* 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 + (a4 < 0)) / 25 - (a4 < 0);
+ int b100 = (b4 + (b4 < 0)) / 25 - (b4 < 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 without overflowing. */
+ long_int years = year1 - year0;
+ long_int days = 365 * years + yday1 - yday0 + intervening_leap_days;
+ long_int hours = 24 * days + hour1 - hour0;
+ long_int minutes = 60 * hours + min1 - min0;
+ long_int seconds = 60 * minutes + sec1 - sec0;
+ return seconds;
+}
+
+/* Return the average of A and B, even if A + B would overflow.
+ Round toward positive infinity. */
+static long_int
+long_int_avg (long_int a, long_int b)
+{
+ return shr (a, 1) + shr (b, 1) + ((a | b) & 1);
+}
+
+/* Return a long_int value corresponding to (YEAR-YDAY HOUR:MIN:SEC)
+ minus *TP seconds, assuming no clock adjustments occurred between
+ the two timestamps.
+
+ YEAR and YDAY must not be so large that multiplying them by three times the
+ number of seconds in a year (or day, respectively) would overflow long_int.
+ *TP should be in the usual range. */
+static long_int
+tm_diff (long_int year, long_int yday, int hour, int min, int sec,
+ struct tm const *tp)
+{
+ return ydhms_diff (year, yday, hour, min, sec,
+ tp->tm_year, tp->tm_yday,
+ tp->tm_hour, tp->tm_min, tp->tm_sec);
+}
+
+/* Use CONVERT to convert T to a struct tm value in *TM. T must be in
+ range for __time64_t. Return TM if successful, NULL (setting errno) on
+ failure. */
+static struct tm *
+convert_time (struct tm *(*convert) (const __time64_t *, struct tm *),
+ long_int t, struct tm *tm)
+{
+ __time64_t x = t;
+ return convert (&x, tm);
+}
+
+/* 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.
+ A value is in range if it fits in both __time64_t and long_int.
+ Return TP on success, NULL (setting errno) on failure. */
+static struct tm *
+ranged_convert (struct tm *(*convert) (const __time64_t *, struct tm *),
+ long_int *t, struct tm *tp)
+{
+ long_int t1 = (*t < mktime_min ? mktime_min
+ : *t <= mktime_max ? *t : mktime_max);
+ struct tm *r = convert_time (convert, t1, tp);
+ if (r)
+ {
+ *t = t1;
+ return r;
+ }
+ if (errno != EOVERFLOW)
+ return NULL;
+
+ long_int bad = t1;
+ long_int ok = 0;
+ struct tm oktm; oktm.tm_sec = -1;
+
+ /* BAD is a known out-of-range value, and OK is a known in-range one.
+ Use binary search to narrow the range between BAD and OK until
+ they differ by 1. */
+ while (true)
+ {
+ long_int mid = long_int_avg (ok, bad);
+ if (mid == ok || mid == bad)
+ break;
+ if (convert_time (convert, mid, tp))
+ ok = mid, oktm = *tp;
+ else if (errno != EOVERFLOW)
+ return NULL;
+ else
+ bad = mid;
+ }
+
+ if (oktm.tm_sec < 0)
+ return NULL;
+ *t = ok;
+ *tp = oktm;
+ return tp;
+}
+
+
+/* Convert *TP to a __time64_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.
+ If successful, set *TP to the canonicalized struct tm;
+ otherwise leave *TP alone, return ((time_t) -1) and set errno.
+ This function is external because it is used also by timegm.c. */
+__time64_t
+__mktime_internal (struct tm *tp,
+ struct tm *(*convert) (const __time64_t *, struct tm *),
+ mktime_offset_t *offset)
+{
+ 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 = 0;
+
+ /* 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 overflows correctly. */
+
+ /* 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;
+
+ mktime_offset_t off = *offset;
+ int negative_offset_guess;
+
+ int sec_requested = sec;
+
+ if (LEAP_SECONDS_POSSIBLE)
+ {
+ /* Handle out-of-range seconds specially,
+ since ydhms_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. */
+
+ INT_SUBTRACT_WRAPV (0, off, &negative_offset_guess);
+ long_int t0 = ydhms_diff (year, yday, hour, min, sec,
+ EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0,
+ negative_offset_guess);
+ long_int t = t0, t1 = t0, t2 = t0;
+
+ /* Repeatedly use the error to improve the guess. */
+
+ while (true)
+ {
+ if (! ranged_convert (convert, &t, &tm))
+ return -1;
+ long_int dt = tm_diff (year, yday, hour, min, sec, &tm);
+ if (dt == 0)
+ break;
+
+ 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. */
+ goto offset_found;
+
+ remaining_probes--;
+ if (remaining_probes == 0)
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+
+ t1 = t2, t2 = t, t += dt, dst2 = tm.tm_isdst != 0;
+ }
+
+ /* We have a match. Check whether tm.tm_isdst has the requested
+ value, if any. */
+ if (isdst_differ (isdst, 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. If none is found within a
+ reasonable duration bound, assume a one-hour DST difference.
+ This should work for all real time zone histories in the tz
+ database. */
+
+ /* +1 if we wanted standard time but got DST, -1 if the reverse. */
+ int dst_difference = (isdst == 0) - (tm.tm_isdst == 0);
+
+ /* 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;
+
+ /* In TZDB 2021e, the longest period of DST (or of non-DST), in
+ which the DST (or adjacent DST) difference is not one hour,
+ is 457243209 seconds: e.g., America/Cambridge_Bay with leap
+ seconds, starting 1965-10-31 00:00 in a switch from
+ double-daylight time (-05) to standard time (-07), and
+ continuing to 1980-04-27 02:00 in a switch from standard time
+ (-07) to daylight time (-06). */
+ int duration_max = 457243209;
+
+ /* 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)
+ {
+ long_int ot;
+ if (! INT_ADD_WRAPV (t, delta * direction, &ot))
+ {
+ struct tm otm;
+ if (! ranged_convert (convert, &ot, &otm))
+ return -1;
+ if (! isdst_differ (isdst, otm.tm_isdst))
+ {
+ /* We found the desired tm_isdst.
+ Extrapolate back to the desired time. */
+ long_int gt = ot + tm_diff (year, yday, hour, min, sec,
+ &otm);
+ if (mktime_min <= gt && gt <= mktime_max)
+ {
+ if (convert_time (convert, gt, &tm))
+ {
+ t = gt;
+ goto offset_found;
+ }
+ if (errno != EOVERFLOW)
+ return -1;
+ }
+ }
+ }
+ }
+
+ /* No unusual DST offset was found nearby. Assume one-hour DST. */
+ t += 60 * 60 * dst_difference;
+ if (mktime_min <= t && t <= mktime_max && convert_time (convert, t, &tm))
+ goto offset_found;
+
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+
+ offset_found:
+ /* Set *OFFSET to the low-order bits of T - T0 - NEGATIVE_OFFSET_GUESS.
+ This is just a heuristic to speed up the next mktime call, and
+ correctness is unaffected if integer overflow occurs here. */
+ INT_SUBTRACT_WRAPV (t, t0, offset);
+ INT_SUBTRACT_WRAPV (*offset, negative_offset_guess, offset);
+
+ 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. */
+ long_int sec_adjustment = sec == 0 && tm.tm_sec == 60;
+ sec_adjustment -= sec;
+ sec_adjustment += sec_requested;
+ if (INT_ADD_WRAPV (t, sec_adjustment, &t)
+ || ! (mktime_min <= t && t <= mktime_max))
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+ if (! convert_time (convert, t, &tm))
+ return -1;
+ }
+
+ *tp = tm;
+ return t;
+}
+
+#endif /* _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_INTERNAL */
+
+#if defined _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_WINDOWS
+
+/* Convert *TP to a __time64_t value. */
+__time64_t
+__mktime64 (struct tm *tp)
+{
+ /* 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 ();
+
+# if defined _LIBC || NEED_MKTIME_WORKING
+ static mktime_offset_t localtime_offset;
+ return __mktime_internal (tp, __localtime64_r, &localtime_offset);
+# else
+# undef mktime
+ return mktime (tp);
+# endif
+}
+#endif /* _LIBC || NEED_MKTIME_WORKING || NEED_MKTIME_WINDOWS */
+
+#if defined _LIBC && __TIMESIZE != 64
+
+libc_hidden_def (__mktime64)
+
+time_t
+mktime (struct tm *tp)
+{
+ struct tm tm = *tp;
+ __time64_t t = __mktime64 (&tm);
+ if (in_time_t_range (t))
+ {
+ *tp = tm;
+ return t;
+ }
+ else
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+}
+
+#endif
+
+weak_alias (mktime, timelocal)
+libc_hidden_def (mktime)
+libc_hidden_weak (timelocal)