X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmktime.c;h=c8ecd07f12b6592b92b6425e7bf353d316b41550;hb=24552d14072b435cf47c5b6da7262bcb43578046;hp=bff026f3e1ebef9713ad1aec8c2db0d0bc46ff12;hpb=6d8337bfc808cddc275899c03482eceb6aff8547;p=gnulib.git diff --git a/lib/mktime.c b/lib/mktime.c index bff026f3e..c8ecd07f1 100644 --- a/lib/mktime.c +++ b/lib/mktime.c @@ -1,79 +1,91 @@ -/* Copyright (C) 1993, 1994, 1995 Free Software Foundation, Inc. +/* Convert a `struct tm' to a time_t value. + Copyright (C) 1993, 94, 95, 96, 97, 98, 99 Free Software Foundation, Inc. + This file is part of the GNU C Library. Contributed by Paul Eggert (eggert@twinsun.com). -This file is part of the GNU C Library. + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. -The GNU C Library is free software; you can redistribute it and/or -modify it under the terms of the GNU Library General Public License as -published by the Free Software Foundation; either version 2 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 + Library General Public License for more details. -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 -Library General Public License for more details. - -You should have received a copy of the GNU Library General Public -License along with the GNU C Library; see the file COPYING.LIB. If -not, write to the Free Software Foundation, Inc., 59 Temple Place - -Suite 330, Boston, MA 02111-1307, USA. */ + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. 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 +# include +#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 +# define LEAP_SECONDS_POSSIBLE 1 #endif #include /* Some systems define `time_t' here. */ #include -#if __STDC__ || __GNU_LIBRARY__ || STDC_HEADERS -#include +#if HAVE_LIMITS_H +# include #endif #if DEBUG -#include -#if __STDC__ || __GNU_LIBRARY__ || STDC_HEADERS -#include -#endif +# include +# if STDC_HEADERS +# include +# endif /* Make it work even if the system's libc has its own mktime routine. */ -#define mktime my_mktime +# define mktime my_mktime #endif /* DEBUG */ #ifndef __P -#if defined (__GNUC__) || (defined (__STDC__) && __STDC__) -#define __P(args) args -#else -#define __P(args) () -#endif /* GCC. */ +# 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 +# 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 (~0 << (sizeof (int) * CHAR_BIT - 1)) +# define INT_MIN TYPE_MINIMUM (int) #endif #ifndef INT_MAX -#define INT_MAX (~0 - INT_MIN) +# define INT_MAX TYPE_MAXIMUM (int) #endif #ifndef TIME_T_MIN -#define TIME_T_MIN (0 < (time_t) -1 ? (time_t) 0 \ - : ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1)) +# define TIME_T_MIN TYPE_MINIMUM (time_t) #endif #ifndef TIME_T_MAX -#define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN) +# define TIME_T_MAX TYPE_MAXIMUM (time_t) #endif #define TM_YEAR_BASE 1900 @@ -82,7 +94,7 @@ Suite 330, Boston, MA 02111-1307, USA. */ #ifndef __isleap /* Nonzero if YEAR is a leap year (every 4 years, except every 100th isn't, and every 400th is). */ -#define __isleap(year) \ +# define __isleap(year) \ ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0)) #endif @@ -95,23 +107,15 @@ const unsigned short int __mon_yday[2][13] = { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 } }; -static time_t ydhms_tm_diff __P ((int, int, int, int, int, const struct tm *)); -time_t __mktime_internal __P ((struct tm *, - struct tm *(*) (const time_t *, struct tm *), - time_t *)); - -#if ! HAVE_LOCALTIME_R && ! defined (localtime_r) #ifdef _LIBC -#define localtime_r __localtime_r +# define my_mktime_localtime_r __localtime_r #else -/* Approximate localtime_r as best we can in its absence. */ -#define localtime_r my_localtime_r -static struct tm *localtime_r __P ((const time_t *, struct tm *)); +/* 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 * -localtime_r (t, tp) - const time_t *t; - struct tm *tp; +my_mktime_localtime_r (const time_t *t, struct tm *tp) { struct tm *l = localtime (t); if (! l) @@ -120,60 +124,107 @@ localtime_r (t, tp) return tp; } #endif /* ! _LIBC */ -#endif /* ! HAVE_LOCALTIME_R && ! defined (localtime_r) */ /* 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 (year, yday, hour, min, sec, tp) - int year, yday, hour, min, sec; - const struct tm *tp; +ydhms_tm_diff (int year, int yday, int hour, int min, int sec, + const struct tm *tp) { - time_t ay = year + (time_t) (TM_YEAR_BASE - 1); - time_t by = tp->tm_year + (time_t) (TM_YEAR_BASE - 1); - time_t intervening_leap_days = - (ay/4 - by/4) - (ay/100 - by/100) + (ay/400 - by/400); - time_t years = ay - by; - 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)); + 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)); + } } - -/* Convert *TP to a time_t value. */ -time_t -mktime (tp) - struct tm *tp; +/* 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) { - static time_t localtime_offset; - return __mktime_internal (tp, localtime_r, &localtime_offset); + 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 (tp, convert, offset) - struct tm *tp; - struct tm *(*convert) __P ((const time_t *, struct tm *)); - time_t *offset; +__mktime_internal (struct tm *tp, + struct tm *(*convert) (const time_t *, struct tm *), + time_t *offset) { - time_t t, dt, t0; + 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, - and leap seconds. Posix.1 prohibits leap seconds, but some hosts - have them anyway. */ - int remaining_probes = 4; + 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. */ @@ -202,10 +253,10 @@ __mktime_internal (tp, convert, offset) [mon_remainder + 12 * negative_mon_remainder]) + mday - 1); + int sec_requested = sec; #if LEAP_SECONDS_POSSIBLE /* Handle out-of-range seconds specially, since ydhms_tm_diff assumes every minute has 60 seconds. */ - int sec_requested = sec; if (sec < 0) sec = 0; if (59 < sec) @@ -219,35 +270,52 @@ __mktime_internal (tp, convert, offset) 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 = t0 + *offset; - (dt = ydhms_tm_diff (year, yday, hour, min, sec, (*convert) (&t, &tm))); - t += dt) - if (--remaining_probes == 0) + for (t = t1 = t2 = t0 + *offset; + (dt = ydhms_tm_diff (year, yday, hour, min, sec, + ranged_convert (convert, &t, &tm))); + t1 = t2, t2 = t, t += dt) + if (t == t1 && t != t2 + && (isdst < 0 || 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. In practice, + this is more useful than returning -1. */ + break; + else if (--remaining_probes == 0) return -1; - /* Check whether tm.tm_isdst has the requested value, if any. */ - if (0 <= isdst && 0 <= tm.tm_isdst) + /* 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) { - int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); - if (dst_diff) + /* 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++) { - /* Move two hours in the direction indicated by the disagreement, - probe some more, and switch to a new time if found. - The largest known fallback due to daylight savings is two hours: - once, in Newfoundland, 1988-10-30 02:00 -> 00:00. */ - time_t ot = t - 2 * 60 * 60 * dst_diff; - while (--remaining_probes != 0) + time_t ot = t - i * quarter; + struct tm otm; + ranged_convert (convert, &ot, &otm); + if (otm.tm_isdst == isdst) { - struct tm otm; - if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec, - (*convert) (&ot, &otm)))) - { - t = ot; - tm = otm; - break; - } - if ((ot += dt) == t) - break; /* Avoid a redundant probe. */ + /* 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; } } } @@ -260,7 +328,8 @@ __mktime_internal (tp, convert, offset) /* 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); - (*convert) (&t, &tm); + if (! (*convert) (&t, &tm)) + return -1; } #endif @@ -276,7 +345,15 @@ __mktime_internal (tp, convert, offset) double dday = 366 * dyear + mday; double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested; - if (TIME_T_MAX / 3 - TIME_T_MIN / 3 < (dsec < 0 ? - dsec : dsec)) + /* 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; } @@ -284,6 +361,24 @@ __mktime_internal (tp, convert, offset) 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 @@ -310,25 +405,28 @@ static void print_tm (tp) struct tm *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); + 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, tml) +check_result (tk, tmk, tl, lt) time_t tk; struct tm tmk; time_t tl; - struct tm tml; + struct tm *lt; { - if (tk != tl || not_equal_tm (&tmk, &tml)) + if (tk != tl || !lt || not_equal_tm (&tmk, lt)) { printf ("mktime ("); print_tm (&tmk); printf (")\nyields ("); - print_tm (&tml); + print_tm (lt); printf (") == %ld, should be %ld\n", (long) tl, (long) tk); return 1; } @@ -343,6 +441,7 @@ main (argc, argv) { int status = 0; struct tm tm, tmk, tml; + struct tm *lt; time_t tk, tl; char trailer; @@ -359,11 +458,16 @@ main (argc, argv) tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]); tmk = tm; tl = mktime (&tmk); - tml = *localtime (&tl); + 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, tml); + status = check_result (tl, tmk, tl, lt); } else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0)) { @@ -374,19 +478,35 @@ main (argc, argv) if (argc == 4) for (tl = from; tl <= to; tl += by) { - tml = *localtime (&tl); - tmk = tml; - tk = mktime (&tmk); - status |= check_result (tk, tmk, tl, tml); + 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. */ - tml = *localtime (&tl); - tmk = tml; - tk = tl; - status |= check_result (tk, tmk, tl, tml); + 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 @@ -403,6 +523,6 @@ main (argc, argv) /* Local Variables: -compile-command: "gcc -DDEBUG=1 -Wall -O -g mktime.c -o mktime" +compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime" End: */