425 lines
12 KiB
C
425 lines
12 KiB
C
/* Copyright (C) 1993-2002 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Paul Eggert (eggert@twinsun.com).
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* Define this to have a standalone program to test this implementation of
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mktime. */
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/* #define DEBUG 1 */
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#ifdef _LIBC
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# define HAVE_LIMITS_H 1
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# define HAVE_LOCALTIME_R 1
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# define STDC_HEADERS 1
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#endif
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/* Assume that leap seconds are possible, unless told otherwise.
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If the host has a `zic' command with a `-L leapsecondfilename' option,
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then it supports leap seconds; otherwise it probably doesn't. */
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#ifndef LEAP_SECONDS_POSSIBLE
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#define LEAP_SECONDS_POSSIBLE 1
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#endif
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#ifndef VMS
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#include <sys/types.h> /* Some systems define `time_t' here. */
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#else
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#include <stddef.h>
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#endif
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#include <time.h>
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#if HAVE_LIMITS_H
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#include <limits.h>
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#endif
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#if DEBUG
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#include <stdio.h>
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#if STDC_HEADERS
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#include <stdlib.h>
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#endif
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/* Make it work even if the system's libc has its own mktime routine. */
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#define mktime my_mktime
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#endif /* DEBUG */
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#ifndef __P
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#if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
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#define __P(args) args
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#else
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#define __P(args) ()
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#endif /* GCC. */
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#endif /* Not __P. */
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#ifndef CHAR_BIT
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#define CHAR_BIT 8
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#endif
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#ifndef INT_MIN
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#define INT_MIN (~0 << (sizeof (int) * CHAR_BIT - 1))
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#endif
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#ifndef INT_MAX
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#define INT_MAX (~0 - INT_MIN)
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#endif
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#ifndef TIME_T_MIN
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#define TIME_T_MIN (0 < (time_t) -1 ? (time_t) 0 \
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: ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1))
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#endif
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#ifndef TIME_T_MAX
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#define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN)
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#endif
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#define TM_YEAR_BASE 1900
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#define EPOCH_YEAR 1970
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#ifndef __isleap
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/* Nonzero if YEAR is a leap year (every 4 years,
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except every 100th isn't, and every 400th is). */
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#define __isleap(year) \
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((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
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#endif
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/* How many days come before each month (0-12). */
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const unsigned short int __mon_yday[2][13] =
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{
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/* Normal years. */
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{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
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/* Leap years. */
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{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
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};
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static time_t ydhms_tm_diff __P ((int, int, int, int, int, const struct tm *));
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time_t __mktime_internal __P ((struct tm *,
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struct tm *(*) (const time_t *, struct tm *),
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time_t *));
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static struct tm *my_localtime_r __P ((const time_t *, struct tm *));
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static struct tm *
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my_localtime_r (t, tp)
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const time_t *t;
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struct tm *tp;
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{
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struct tm *l = localtime (t);
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if (! l)
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return 0;
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*tp = *l;
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return tp;
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}
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/* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP),
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measured in seconds, ignoring leap seconds.
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YEAR uses the same numbering as TM->tm_year.
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All values are in range, except possibly YEAR.
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If overflow occurs, yield the low order bits of the correct answer. */
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static time_t
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ydhms_tm_diff (year, yday, hour, min, sec, tp)
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int year, yday, hour, min, sec;
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const struct tm *tp;
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{
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/* Compute intervening leap days correctly even if year is negative.
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Take care to avoid int overflow. time_t overflow is OK, since
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only the low order bits of the correct time_t answer are needed.
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Don't convert to time_t until after all divisions are done, since
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time_t might be unsigned. */
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int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3);
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int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3);
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int a100 = a4 / 25 - (a4 % 25 < 0);
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int b100 = b4 / 25 - (b4 % 25 < 0);
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int a400 = a100 >> 2;
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int b400 = b100 >> 2;
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int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
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time_t years = year - (time_t) tp->tm_year;
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time_t days = (365 * years + intervening_leap_days
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+ (yday - tp->tm_yday));
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return (60 * (60 * (24 * days + (hour - tp->tm_hour))
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+ (min - tp->tm_min))
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+ (sec - tp->tm_sec));
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}
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static time_t localtime_offset;
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/* Convert *TP to a time_t value. */
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time_t
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mktime (tp)
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struct tm *tp;
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{
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#ifdef _LIBC
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/* POSIX.1 8.1.1 requires that whenever mktime() is called, the
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time zone names contained in the external variable `tzname' shall
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be set as if the tzset() function had been called. */
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__tzset ();
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#endif
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return __mktime_internal (tp, my_localtime_r, &localtime_offset);
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}
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/* Convert *TP to a time_t value, inverting
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the monotonic and mostly-unit-linear conversion function CONVERT.
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Use *OFFSET to keep track of a guess at the offset of the result,
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compared to what the result would be for UTC without leap seconds.
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If *OFFSET's guess is correct, only one CONVERT call is needed. */
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time_t
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__mktime_internal (tp, convert, offset)
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struct tm *tp;
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struct tm *(*convert) __P ((const time_t *, struct tm *));
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time_t *offset;
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{
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time_t t, dt, t0;
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struct tm tm;
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/* The maximum number of probes (calls to CONVERT) should be enough
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to handle any combinations of time zone rule changes, solar time,
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and leap seconds. Posix.1 prohibits leap seconds, but some hosts
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have them anyway. */
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int remaining_probes = 4;
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/* Time requested. Copy it in case CONVERT modifies *TP; this can
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occur if TP is localtime's returned value and CONVERT is localtime. */
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int sec = tp->tm_sec;
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int min = tp->tm_min;
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int hour = tp->tm_hour;
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int mday = tp->tm_mday;
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int mon = tp->tm_mon;
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int year_requested = tp->tm_year;
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int isdst = tp->tm_isdst;
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/* Ensure that mon is in range, and set year accordingly. */
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int mon_remainder = mon % 12;
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int negative_mon_remainder = mon_remainder < 0;
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int mon_years = mon / 12 - negative_mon_remainder;
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int year = year_requested + mon_years;
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/* The other values need not be in range:
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the remaining code handles minor overflows correctly,
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assuming int and time_t arithmetic wraps around.
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Major overflows are caught at the end. */
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/* Calculate day of year from year, month, and day of month.
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The result need not be in range. */
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int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)]
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[mon_remainder + 12 * negative_mon_remainder])
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+ mday - 1);
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#if LEAP_SECONDS_POSSIBLE
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/* Handle out-of-range seconds specially,
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since ydhms_tm_diff assumes every minute has 60 seconds. */
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int sec_requested = sec;
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if (sec < 0)
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sec = 0;
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if (59 < sec)
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sec = 59;
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#endif
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/* Invert CONVERT by probing. First assume the same offset as last time.
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Then repeatedly use the error to improve the guess. */
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tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE;
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tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
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t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
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for (t = t0 + *offset;
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(dt = ydhms_tm_diff (year, yday, hour, min, sec, (*convert) (&t, &tm)));
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t += dt)
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if (--remaining_probes == 0)
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return -1;
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/* Check whether tm.tm_isdst has the requested value, if any. */
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if (0 <= isdst && 0 <= tm.tm_isdst)
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{
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int dst_diff = (isdst != 0) - (tm.tm_isdst != 0);
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if (dst_diff)
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{
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/* Move two hours in the direction indicated by the disagreement,
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probe some more, and switch to a new time if found.
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The largest known fallback due to daylight savings is two hours:
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once, in Newfoundland, 1988-10-30 02:00 -> 00:00. */
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time_t ot = t - 2 * 60 * 60 * dst_diff;
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while (--remaining_probes != 0)
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{
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struct tm otm;
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if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec,
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(*convert) (&ot, &otm))))
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{
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t = ot;
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tm = otm;
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break;
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}
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if ((ot += dt) == t)
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break; /* Avoid a redundant probe. */
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}
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}
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}
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*offset = t - t0;
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#if LEAP_SECONDS_POSSIBLE
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if (sec_requested != tm.tm_sec)
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{
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/* Adjust time to reflect the tm_sec requested, not the normalized value.
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Also, repair any damage from a false match due to a leap second. */
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t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60);
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(*convert) (&t, &tm);
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}
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#endif
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if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)
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{
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/* time_t isn't large enough to rule out overflows in ydhms_tm_diff,
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so check for major overflows. A gross check suffices,
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since if t has overflowed, it is off by a multiple of
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TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of
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the difference that is bounded by a small value. */
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double dyear = (double) year_requested + mon_years - tm.tm_year;
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double dday = 366 * dyear + mday;
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double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested;
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if (TIME_T_MAX / 3 - TIME_T_MIN / 3 < (dsec < 0 ? - dsec : dsec))
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return -1;
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}
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*tp = tm;
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return t;
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}
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#ifdef weak_alias
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weak_alias (mktime, timelocal)
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#endif
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#if DEBUG
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static int
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not_equal_tm (a, b)
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struct tm *a;
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struct tm *b;
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{
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return ((a->tm_sec ^ b->tm_sec)
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| (a->tm_min ^ b->tm_min)
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| (a->tm_hour ^ b->tm_hour)
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| (a->tm_mday ^ b->tm_mday)
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| (a->tm_mon ^ b->tm_mon)
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| (a->tm_year ^ b->tm_year)
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| (a->tm_mday ^ b->tm_mday)
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| (a->tm_yday ^ b->tm_yday)
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| (a->tm_isdst ^ b->tm_isdst));
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}
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static void
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print_tm (tp)
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struct tm *tp;
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{
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printf ("%04d-%02d-%02d %02d:%02d:%02d yday %03d wday %d isdst %d",
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tp->tm_year + TM_YEAR_BASE, tp->tm_mon + 1, tp->tm_mday,
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tp->tm_hour, tp->tm_min, tp->tm_sec,
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tp->tm_yday, tp->tm_wday, tp->tm_isdst);
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}
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static int
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check_result (tk, tmk, tl, tml)
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time_t tk;
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struct tm tmk;
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time_t tl;
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struct tm tml;
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{
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if (tk != tl || not_equal_tm (&tmk, &tml))
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{
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printf ("mktime (");
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print_tm (&tmk);
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printf (")\nyields (");
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print_tm (&tml);
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printf (") == %ld, should be %ld\n", (long) tl, (long) tk);
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return 1;
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}
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return 0;
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}
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int
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main (argc, argv)
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int argc;
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char **argv;
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{
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int status = 0;
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struct tm tm, tmk, tml;
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time_t tk, tl;
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char trailer;
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if ((argc == 3 || argc == 4)
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&& (sscanf (argv[1], "%d-%d-%d%c",
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&tm.tm_year, &tm.tm_mon, &tm.tm_mday, &trailer)
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== 3)
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&& (sscanf (argv[2], "%d:%d:%d%c",
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&tm.tm_hour, &tm.tm_min, &tm.tm_sec, &trailer)
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== 3))
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{
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tm.tm_year -= TM_YEAR_BASE;
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tm.tm_mon--;
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tm.tm_isdst = argc == 3 ? -1 : atoi (argv[3]);
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tmk = tm;
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tl = mktime (&tmk);
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tml = *localtime (&tl);
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printf ("mktime returns %ld == ", (long) tl);
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print_tm (&tmk);
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printf ("\n");
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status = check_result (tl, tmk, tl, tml);
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}
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else if (argc == 4 || (argc == 5 && strcmp (argv[4], "-") == 0))
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{
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time_t from = atol (argv[1]);
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time_t by = atol (argv[2]);
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time_t to = atol (argv[3]);
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if (argc == 4)
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for (tl = from; tl <= to; tl += by)
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{
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tml = *localtime (&tl);
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tmk = tml;
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tk = mktime (&tmk);
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status |= check_result (tk, tmk, tl, tml);
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}
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else
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for (tl = from; tl <= to; tl += by)
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{
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/* Null benchmark. */
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tml = *localtime (&tl);
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tmk = tml;
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tk = tl;
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status |= check_result (tk, tmk, tl, tml);
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}
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}
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else
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printf ("Usage:\
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\t%s YYYY-MM-DD HH:MM:SS [ISDST] # Test given time.\n\
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\t%s FROM BY TO # Test values FROM, FROM+BY, ..., TO.\n\
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\t%s FROM BY TO - # Do not test those values (for benchmark).\n",
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argv[0], argv[0], argv[0]);
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return status;
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}
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#endif /* DEBUG */
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/*
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Local Variables:
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compile-command: "gcc -DDEBUG=1 -Wall -O -g mktime.c -o mktime"
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End:
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*/
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