2b72262b4f
I hereby relicense all my work on Sortix under the ISC license as below. All Sortix contributions by other people are already under this license, are not substantial enough to be copyrightable, or have been removed. All imported code from other projects is compatible with this license. All GPL licensed code from other projects had previously been removed. Copyright 2011-2016 Jonas 'Sortie' Termansen and contributors. Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
292 lines
7.2 KiB
C
292 lines
7.2 KiB
C
/*
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* Copyright (c) 2013 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* time/gmtime_r.c
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* Convert a timestamp into a date and time according to UTC.
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*/
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#include <stdbool.h>
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#include <time.h>
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#include <stdint.h>
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#include <time.h>
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static const int DAYS_JANUARY = 31;
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static const int DAYS_FEBRUARY = 28;
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static const int DAYS_MARCH = 31;
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static const int DAYS_APRIL = 30;
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static const int DAYS_MAY = 31;
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static const int DAYS_JUNE = 30;
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static const int DAYS_JULY = 31;
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static const int DAYS_AUGUST = 31;
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static const int DAYS_SEPTEMBER = 30;
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static const int DAYS_OCTOBER = 31;
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static const int DAYS_NOVEMBER = 30;
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static const int DAYS_DECEMBER = 31;
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#define DECL_LEAP_SECOND(year, jun, dec) \
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{0, 0, 0, 0, 0, jun, 0, 0, 0, 0, 0, dec}
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static int8_t leap_seconds[][12] =
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{
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DECL_LEAP_SECOND(1970, 0, 0),
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DECL_LEAP_SECOND(1971, 0, 0),
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DECL_LEAP_SECOND(1972, 1, 1),
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DECL_LEAP_SECOND(1973, 0, 1),
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DECL_LEAP_SECOND(1974, 0, 1),
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DECL_LEAP_SECOND(1975, 0, 1),
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DECL_LEAP_SECOND(1976, 0, 1),
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DECL_LEAP_SECOND(1977, 0, 1),
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DECL_LEAP_SECOND(1978, 0, 1),
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DECL_LEAP_SECOND(1979, 0, 1),
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DECL_LEAP_SECOND(1980, 0, 0),
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DECL_LEAP_SECOND(1981, 1, 0),
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DECL_LEAP_SECOND(1982, 1, 0),
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DECL_LEAP_SECOND(1983, 1, 0),
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DECL_LEAP_SECOND(1984, 0, 0),
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DECL_LEAP_SECOND(1985, 1, 0),
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DECL_LEAP_SECOND(1986, 0, 0),
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DECL_LEAP_SECOND(1987, 0, 1),
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DECL_LEAP_SECOND(1988, 0, 0),
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DECL_LEAP_SECOND(1989, 0, 1),
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DECL_LEAP_SECOND(1990, 0, 1),
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DECL_LEAP_SECOND(1991, 0, 0),
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DECL_LEAP_SECOND(1992, 1, 0),
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DECL_LEAP_SECOND(1993, 1, 0),
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DECL_LEAP_SECOND(1994, 1, 0),
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DECL_LEAP_SECOND(1995, 0, 1),
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DECL_LEAP_SECOND(1996, 0, 0),
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DECL_LEAP_SECOND(1997, 1, 0),
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DECL_LEAP_SECOND(1998, 0, 1),
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DECL_LEAP_SECOND(1999, 0, 0),
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DECL_LEAP_SECOND(2000, 0, 0),
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DECL_LEAP_SECOND(2001, 0, 0),
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DECL_LEAP_SECOND(2002, 0, 0),
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DECL_LEAP_SECOND(2003, 0, 0),
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DECL_LEAP_SECOND(2004, 0, 0),
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DECL_LEAP_SECOND(2005, 0, 1),
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DECL_LEAP_SECOND(2006, 0, 0),
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DECL_LEAP_SECOND(2007, 0, 0),
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DECL_LEAP_SECOND(2008, 0, 1),
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DECL_LEAP_SECOND(2009, 0, 0),
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DECL_LEAP_SECOND(2010, 0, 0),
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DECL_LEAP_SECOND(2011, 0, 0),
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DECL_LEAP_SECOND(2012, 1, 0),
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DECL_LEAP_SECOND(2013, 0, 0),
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DECL_LEAP_SECOND(2014, 0, 0),
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DECL_LEAP_SECOND(2015, 1, 0),
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};
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static time_t get_leap_second(int year, int month)
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{
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const time_t num_years = sizeof(leap_seconds) / sizeof(leap_seconds[0]);
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if ( year < 1970 )
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return 0;
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if ( num_years <= year-1970 )
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return 0;
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return leap_seconds[year-1970][month];
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}
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static time_t leap_seconds_in_year(int year)
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{
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time_t ret = 0;
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for ( int i = 0; i < 12; i++ )
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ret += get_leap_second(year, i);
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return ret;
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}
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static bool is_leap_year(int year)
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{
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return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
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}
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static time_t days_in_year(int year)
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{
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return DAYS_JANUARY +
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DAYS_FEBRUARY + (is_leap_year(year) ? 1 : 0) +
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DAYS_MARCH +
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DAYS_APRIL +
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DAYS_MAY +
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DAYS_JUNE +
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DAYS_JULY +
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DAYS_AUGUST +
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DAYS_SEPTEMBER +
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DAYS_OCTOBER +
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DAYS_NOVEMBER +
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DAYS_DECEMBER;
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}
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struct tm* gmtime_r(const time_t* time_ptr, struct tm* ret)
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{
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time_t left = *time_ptr;
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ret->tm_year = 1970;
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ret->tm_wday = 4 /* Supposedly, the world began on a Thursday. */;
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// If the timestamp is after the epoch.
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while ( 0 < left )
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{
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time_t year_leaps = leap_seconds_in_year(ret->tm_year);
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time_t year_days = days_in_year(ret->tm_year);
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time_t year_seconds = year_days * 24 * 60 * 60 + year_leaps;
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if ( year_seconds <= left )
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{
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left -= year_seconds;
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ret->tm_wday = (ret->tm_wday + year_days) % 7;
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ret->tm_year++;
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continue;
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}
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break;
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}
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// If the timestamp was before the epoch.
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while ( left < 0 )
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{
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ret->tm_year--;
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time_t year_leaps = leap_seconds_in_year(ret->tm_year);
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time_t year_days = days_in_year(ret->tm_year);
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time_t year_seconds = year_days * 24 * 60 * 60 + year_leaps;
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left += year_seconds;
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// We need to avoid taking the modulo of a negative value or the
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// (broken) C modulo operator gives the wrong result.
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ret->tm_wday = (ret->tm_wday - year_days + 7*7*7*7) % 7;
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}
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int month_days_list[12] =
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{
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DAYS_JANUARY,
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DAYS_FEBRUARY + (is_leap_year(ret->tm_year) ? 1 : 0),
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DAYS_MARCH,
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DAYS_APRIL,
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DAYS_MAY,
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DAYS_JUNE,
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DAYS_JULY,
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DAYS_AUGUST,
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DAYS_SEPTEMBER,
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DAYS_OCTOBER,
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DAYS_NOVEMBER,
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DAYS_DECEMBER,
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};
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// Figure out the correct month.
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ret->tm_mon = 0;
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ret->tm_yday = 0;
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while ( true )
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{
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int month_leaps = get_leap_second(ret->tm_year, ret->tm_mon);
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int month_days = month_days_list[ret->tm_mon];
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int month_seconds = month_days * 24 * 60 * 60 + month_leaps;
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if ( month_seconds <= left )
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{
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left -= month_seconds;
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ret->tm_mon++;
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ret->tm_yday += month_days;
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ret->tm_wday = (ret->tm_wday + month_days) % 7;
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continue;
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}
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break;
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}
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ret->tm_mday = left / (24 * 60 * 60);
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left = left % (24 * 60 * 60);
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// If this is a regular timestamp.
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if ( ret->tm_mday < month_days_list[ret->tm_mon] )
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{
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ret->tm_yday += ret->tm_mday;
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ret->tm_hour = left / (60 * 60);
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left = left % (60 * 60);
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ret->tm_min = left / 60;
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left = left % 60;
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ret->tm_sec = left;
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}
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// If we got the timestamp for an added leap second.
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else
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{
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ret->tm_mday--; // Seemingly additional day.
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ret->tm_yday += ret->tm_mday;
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ret->tm_hour = 23;
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ret->tm_min = 59;
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ret->tm_sec = 60;
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}
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ret->tm_wday = (ret->tm_wday + ret->tm_mday) % 7;
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// TODO: Support daylight savings and timezones.
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ret->tm_isdst = -1;
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// Fix the ranges of some of the variables.
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ret->tm_mday += 1;
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ret->tm_year -= 1900;
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return ret;
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}
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time_t timegm(struct tm* tm)
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{
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time_t year = tm->tm_year + 1900;
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time_t month = tm->tm_mon;
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time_t day = tm->tm_mday - 1;
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time_t hour = tm->tm_hour;
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time_t minute = tm->tm_min;
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time_t second = tm->tm_sec;
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time_t ret = 0;
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for ( time_t y = 1970; y < year; y++ )
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{
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time_t year_leaps = leap_seconds_in_year(y);
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time_t year_days = days_in_year(y);
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time_t year_seconds = year_days * 24 * 60 * 60 + year_leaps;
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ret += year_seconds;
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}
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int month_days_list[12] =
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{
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DAYS_JANUARY,
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DAYS_FEBRUARY + (is_leap_year(year) ? 1 : 0),
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DAYS_MARCH,
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DAYS_APRIL,
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DAYS_MAY,
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DAYS_JUNE,
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DAYS_JULY,
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DAYS_AUGUST,
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DAYS_SEPTEMBER,
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DAYS_OCTOBER,
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DAYS_NOVEMBER,
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DAYS_DECEMBER,
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};
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for ( uint8_t m = 0; m < month; m++ )
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{
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int month_leaps = get_leap_second(year, m);
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int month_days = month_days_list[m];
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int month_seconds = month_days * 24 * 60 * 60 + month_leaps;
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ret += month_seconds;
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}
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ret += (time_t) day * 24 * 60 * 60;
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ret += (time_t) hour * 60 * 60;
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ret += (time_t) minute * 60;
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ret += (time_t) second * 1;
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gmtime_r(&ret, tm);
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return ret;
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}
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