| /* Convert a 'struct tm' to a time_t value. |
| Copyright (C) 1993-2020 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="); |
| # elif HAVE_TZSET |
| 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. 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) |
| { |
| 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; |
| } |
| } |
| } |
| } |
| |
| __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) |