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-rw-r--r--libc/misc/time/mktime.c327
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diff --git a/libc/misc/time/mktime.c b/libc/misc/time/mktime.c
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-/* 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>
-#include <limits.h>
-
-#if 0
-#ifndef CHAR_BIT
-# 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 TYPE_MINIMUM (int)
-#endif
-#ifndef INT_MAX
-# define INT_MAX TYPE_MAXIMUM (int)
-#endif
-
-#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 TM_YEAR_BASE 1900
-#define EPOCH_YEAR 1970
-
-
-/* How many days come before each month (0-12). */
-extern const unsigned short int __mon_yday[2][13];
-
-
-
-/* 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 (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 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));
- }
-}
-
-/* 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;
-
- 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 (struct tm *tp,
- struct tm *(*convert) (const time_t *, struct tm *), time_t *offset)
-{
- 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. */
- 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 = 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;
-
-#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);
- if (! (*convert) (&t, &tm))
- 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;
-}
-
-
-
-/* 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