diff options
Diffstat (limited to 'libc/misc/time/mktime.c')
| -rw-r--r-- | libc/misc/time/mktime.c | 475 |
1 files changed, 258 insertions, 217 deletions
diff --git a/libc/misc/time/mktime.c b/libc/misc/time/mktime.c index 7286e666b..065126e0e 100644 --- a/libc/misc/time/mktime.c +++ b/libc/misc/time/mktime.c @@ -1,92 +1,90 @@ - -/* This is adapted from glibc */ -/* Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc. */ - - -/* 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 <sys/types.h> /* Some systems define `time_t' here. */ +/* 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). + + 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. */ + +#include <features.h> +/* Assume that leap seconds are not possible */ +#undef LEAP_SECONDS_POSSIBLE +#include <sys/types.h> /* Some systems define `time_t' here. */ #include <time.h> - -#if __STDC__ || __GNU_LIBRARY__ || STDC_HEADERS #include <limits.h> -#endif - -#if DEBUG -#include <stdio.h> -#if __STDC__ || __GNU_LIBRARY__ || STDC_HEADERS -#include <stdlib.h> -#endif -/* Make it work even if the system's libc has its own mktime routine. */ -#define mktime my_mktime -#endif /* DEBUG */ - -#ifndef __P -#if defined (__GNUC__) || (defined (__STDC__) && __STDC__) -#define __P(args) args -#else -#define __P(args) () -#endif /* GCC. */ -#endif /* Not __P. */ +#if 0 #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 #define EPOCH_YEAR 1970 -#ifndef __isleap -/* Nonzero if YEAR is a leap year (every 4 years, - except every 100th isn't, and every 400th is). */ -#define __isleap(year) \ - ((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0)) -#endif +/* How many days come before each month (0-12). */ extern const unsigned short int __mon_yday[2][13]; -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 *)); /* 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; +static time_t +__ydhms_tm_diff (int year, int yday, int hour, int min, int sec, + const struct tm *tp) { + 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 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; @@ -94,193 +92,236 @@ const struct tm *tp; 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)); + + (yday - tp->tm_yday)); return (60 * (60 * (24 * days + (hour - tp->tm_hour)) - + (min - tp->tm_min)) - + (sec - tp->tm_sec)); + + (min - tp->tm_min)) + + (sec - tp->tm_sec)); + } } - -/* This structure contains all the information about a - timezone given in the POSIX standard TZ envariable. */ -typedef struct - { - const char *name; - - /* When to change. */ - enum { J0, J1, M } type; /* Interpretation of: */ - unsigned short int m, n, d; /* Month, week, day. */ - unsigned int secs; /* Time of day. */ - - long int offset; /* Seconds east of GMT (west if < 0). */ - - /* We cache the computed time of change for a - given year so we don't have to recompute it. */ - time_t change; /* When to change to this zone. */ - int computed_for; /* Year above is computed for. */ - } tz_rule; - -/* tz_rules[0] is standard, tz_rules[1] is daylight. */ -static tz_rule tz_rules[2]; - -/* Warning -- this function is a stub andd always does UTC - * no matter what it is given */ -void tzset (void) +/* 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) { - tz_rules[0].name = tz_rules[1].name = "UTC"; - tz_rules[0].type = tz_rules[1].type = J0; - tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0; - tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0; - tz_rules[0].secs = tz_rules[1].secs = 0; - tz_rules[0].offset = tz_rules[1].offset = 0L; - tz_rules[0].change = tz_rules[1].change = (time_t) -1; - tz_rules[0].computed_for = tz_rules[1].computed_for = 0; -} - + struct tm *r; + if (! (r = (*convert) (t, tp)) && *t) + { + time_t bad = *t; + time_t ok = 0; + struct tm tm; -static time_t localtime_offset; + /* 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; + } -/* 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 + if (!r && ok) + { + /* The last conversion attempt failed; + revert to the most recent successful attempt. */ + *t = ok; + *tp = tm; + r = tp; + } + } - return __mktime_internal(tp, localtime_r, &localtime_offset); + 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; +time_t __mktime_internal (struct tm *tp, + struct tm *(*convert) (const time_t *, struct tm *), time_t *offset) { - time_t t, dt, t0; - 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; - - /* 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; - - /* 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; - int year = year_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[__isleap(year + TM_YEAR_BASE)] - [mon_remainder + 12 * negative_mon_remainder]) - + mday - 1); - + 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; + + /* 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; + int year = year_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[__isleap (year + TM_YEAR_BASE)] + [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) - sec = 59; + /* 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 = t0 + *offset; - (dt = - ydhms_tm_diff(year, yday, hour, min, sec, (*convert) (&t, &tm))); - t += dt) - if (--remaining_probes == 0) - return -1; - - /* Check whether tm.tm_isdst has the requested value, if any. */ - if (0 <= isdst && 0 <= tm.tm_isdst) { - int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); - - if (dst_diff) { - /* 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) { - 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. */ - } - } + /* 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; + (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; + + /* 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; + *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); - (*convert) (&t, &tm); - } + 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 0 - 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; - - if (TIME_T_MAX / 3 - TIME_T_MIN / 3 < (dsec < 0 ? -dsec : dsec)) - 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; + } - *tp = tm; - return t; + *tp = tm; + return t; } + + + +/* Convert *TP to a time_t value. */ +time_t mktime (struct tm *tp) +{ + static time_t localtime_offset; + /* 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 (); + + return __mktime_internal (tp, localtime_r, &localtime_offset); +} +#else + +/* Convert *TP to a time_t value. */ +time_t mktime (struct tm *tp) +{ + time_t m_secs=tp->tm_min*60; + time_t h_secs=tp->tm_hour*3600; + time_t d_secs=tp->tm_yday*86400; + time_t y_secs=(tp->tm_year-70)*31536000; + time_t l_secs1=((tp->tm_year-69)/4)*86400; + time_t l_secs2=((tp->tm_year-1)/100)*86400; + time_t l_secs3=((tp->tm_year+299)/400)*86400; + return m_secs+h_secs+d_secs+y_secs+l_secs1-l_secs2+l_secs3+tp->tm_gmtoff; +} +#endif |