[perl5.git] / localtime64.c

/*

Copyright (c) 2007-2008  Michael G Schwern

This software originally derived from Paul Sheer's pivotal_gmtime_r.c.

The MIT License:

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

*/

/*

Programmers who have available to them 64-bit time values as a 'long
long' type can use localtime64_r() and gmtime64_r() which correctly
converts the time even on 32-bit systems. Whether you have 64-bit time
values will depend on the operating system.

localtime64_r() is a 64-bit equivalent of localtime_r().

gmtime64_r() is a 64-bit equivalent of gmtime_r().

*/

#include "localtime64.h"

static const int days_in_month[2][12] = {
    {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
    {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
};

static const int julian_days_by_month[2][12] = {
    {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
    {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
};

static const int length_of_year[2] = { 365, 366 };

/* Number of days in a 400 year Gregorian cycle */
static const int years_in_gregorian_cycle = 400;
static const int days_in_gregorian_cycle  = (365 * 400) + 100 - 4 + 1;

/* 28 year calendar cycle between 2010 and 2037 */
static const int safe_years[28] = {
    2016, 2017, 2018, 2019,
    2020, 2021, 2022, 2023,
    2024, 2025, 2026, 2027,
    2028, 2029, 2030, 2031,
    2032, 2033, 2034, 2035,
    2036, 2037, 2010, 2011,
    2012, 2013, 2014, 2015
};

#define SOLAR_CYCLE_LENGTH 28
static const int dow_year_start[SOLAR_CYCLE_LENGTH] = {
    5, 0, 1, 2,     /* 0       2016 - 2019 */
    3, 5, 6, 0,     /* 4  */
    1, 3, 4, 5,     /* 8  */
    6, 1, 2, 3,     /* 12 */
    4, 6, 0, 1,     /* 16 */
    2, 4, 5, 6,     /* 20      2036, 2037, 2010, 2011 */
    0, 2, 3, 4      /* 24      2012, 2013, 2014, 2015 */
};

/* Let's assume people are going to be looking for dates in the future.
   Let's provide some cheats so you can skip ahead.
   This has a 4x speed boost when near 2008.
*/
/* Number of days since epoch on Jan 1st, 2008 GMT */
#define CHEAT_DAYS  (1199145600 / 24 / 60 / 60)
#define CHEAT_YEARS 108

#define IS_LEAP(n)	((!(((n) + 1900) % 400) || (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
#define WRAP(a,b,m)	((a) = ((a) <  0  ) ? ((b)--, (a) + (m)) : (a))

#define SHOULD_USE_SYSTEM_LOCALTIME(a)  (       \
    USE_SYSTEM_LOCALTIME        &&              \
    (a) <= SYSTEM_LOCALTIME_MAX &&              \
    (a) >= SYSTEM_LOCALTIME_MIN                 \
)
#define SHOULD_USE_SYSTEM_GMTIME(a)     (       \
    USE_SYSTEM_GMTIME           &&              \
    (a) <= SYSTEM_GMTIME_MAX    &&              \
    (a) >= SYSTEM_GMTIME_MIN                    \
)


int _is_exception_century(Int64 year)
{
    int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
    /* printf("is_exception_century: %s\n", is_exception ? "yes" : "no"); */

    return(is_exception);
}


/* timegm() is a GNU extension, so emulate it here if we need it */
#ifdef HAS_TIMEGM
#    define TIMEGM(n) timegm(n);
#else
#    define TIMEGM(n) ((time_t)timegm64(n));
#endif

Time64_T timegm64(struct tm *date) {
    int   days    = 0;
    Int64 seconds = 0;
    Int64 year;

    if( date->tm_year > 70 ) {
        year = 70;
        while( year < date->tm_year ) {
            days += length_of_year[IS_LEAP(year)];
            year++;
        }
    }
    else if ( date->tm_year < 70 ) {
        year = 69;
        do {
            days -= length_of_year[IS_LEAP(year)];
            year--;
        } while( year >= date->tm_year );
    }

    days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
    days += date->tm_mday - 1;

    /* Avoid overflowing the days integer */
    seconds = days;
    seconds = seconds * 60 * 60 * 24;

    seconds += date->tm_hour * 60 * 60;
    seconds += date->tm_min * 60;
    seconds += date->tm_sec;

    return((Time64_T)seconds);
}


int _check_tm(struct tm *tm)
{
    /* Don't forget leap seconds */
    assert(tm->tm_sec >= 0);
    assert(tm->tm_sec <= 61);

    assert(tm->tm_min >= 0);
    assert(tm->tm_min <= 59);

    assert(tm->tm_hour >= 0);
    assert(tm->tm_hour <= 23);

    assert(tm->tm_mday >= 1);
    assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);

    assert(tm->tm_mon  >= 0);
    assert(tm->tm_mon  <= 11);

    assert(tm->tm_wday >= 0);
    assert(tm->tm_wday <= 6);

    assert(tm->tm_yday >= 0);
    assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);

#ifdef HAS_TM_TM_GMTOFF
    assert(tm->tm_gmtoff >= -24 * 60 * 60);
    assert(tm->tm_gmtoff <=  24 * 60 * 60);
#endif

    return 1;
}


/* The exceptional centuries without leap years cause the cycle to
   shift by 16
*/
Year _cycle_offset(Year year)
{
    const Year start_year = 2000;
    Year year_diff  = year - start_year;
    Year exceptions;

    if( year > start_year )
        year_diff--;

    exceptions  = year_diff / 100;
    exceptions -= year_diff / 400;

    /*
    fprintf(stderr, "# year: %lld, exceptions: %lld, year_diff: %lld\n",
            year, exceptions, year_diff);
    */

    return exceptions * 16;
}

/* For a given year after 2038, pick the latest possible matching
   year in the 28 year calendar cycle.

   A matching year...
   1) Starts on the same day of the week.
   2) Has the same leap year status.

   This is so the calendars match up.

   Also the previous year must match.  When doing Jan 1st you might
   wind up on Dec 31st the previous year when doing a -UTC time zone.

   Finally, the next year must have the same start day of week.  This
   is for Dec 31st with a +UTC time zone.
   It doesn't need the same leap year status since we only care about
   January 1st.
*/
int _safe_year(Year year)
{
    int safe_year;
    Year year_cycle = year + _cycle_offset(year);

    /* Change non-leap xx00 years to an equivalent */
    if( _is_exception_century(year) )
        year_cycle += 11;

    /* Also xx01 years, since the previous year will be wrong */
    if( _is_exception_century(year - 1) )
        year_cycle += 17;

    year_cycle %= SOLAR_CYCLE_LENGTH;
    if( year_cycle < 0 )
        year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;

    assert( year_cycle >= 0 );
    assert( year_cycle < SOLAR_CYCLE_LENGTH );
    safe_year = safe_years[year_cycle];

    assert(safe_year <= 2037 && safe_year >= 2010);

    /*
    printf("year: %d, year_cycle: %d, safe_year: %d\n",
           year, year_cycle, safe_year);
    */

    return safe_year;
}


struct tm *gmtime64_r (const Time64_T *in_time, struct tm *p)
{
    int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
    Int64 v_tm_tday;
    int leap;
    Int64 m;
    Time64_T time = *in_time;
    Year year = 70;

    /* Use the system gmtime() if time_t is small enough */
    if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
        time_t safe_time = *in_time;
        gmtime_r(&safe_time, p);
        assert(_check_tm(p));
        return p;
    }

#ifdef HAS_TM_TM_GMTOFF
    p->tm_gmtoff = 0;
#endif
    p->tm_isdst  = 0;

#ifdef HAS_TM_TM_ZONE
    p->tm_zone   = "UTC";
#endif

    v_tm_sec =  (int)(time % 60);
    time /= 60;
    v_tm_min =  (int)(time % 60);
    time /= 60;
    v_tm_hour = (int)(time % 24);
    time /= 24;
    v_tm_tday = time;

    WRAP (v_tm_sec, v_tm_min, 60);
    WRAP (v_tm_min, v_tm_hour, 60);
    WRAP (v_tm_hour, v_tm_tday, 24);

    v_tm_wday = (int)((v_tm_tday + 4) % 7);
    if (v_tm_wday < 0)
        v_tm_wday += 7;
    m = v_tm_tday;

    if (m >= CHEAT_DAYS) {
        year = CHEAT_YEARS;
        m -= CHEAT_DAYS;
    }

    if (m >= 0) {
        /* Gregorian cycles, this is huge optimization for distant times */
        while (m >= (Time64_T) days_in_gregorian_cycle) {
            m -= (Time64_T) days_in_gregorian_cycle;
            year += years_in_gregorian_cycle;
        }

        /* Years */
        leap = IS_LEAP (year);
        while (m >= (Time64_T) length_of_year[leap]) {
            m -= (Time64_T) length_of_year[leap];
            year++;
            leap = IS_LEAP (year);
        }

        /* Months */
        v_tm_mon = 0;
        while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
            m -= (Time64_T) days_in_month[leap][v_tm_mon];
            v_tm_mon++;
        }
    } else {
        year--;

        /* Gregorian cycles */
        while (m < (Time64_T) -days_in_gregorian_cycle) {
            m += (Time64_T) days_in_gregorian_cycle;
            year -= years_in_gregorian_cycle;
        }

        /* Years */
        leap = IS_LEAP (year);
        while (m < (Time64_T) -length_of_year[leap]) {
            m += (Time64_T) length_of_year[leap];
            year--;
            leap = IS_LEAP (year);
        }

        /* Months */
        v_tm_mon = 11;
        while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
            m += (Time64_T) days_in_month[leap][v_tm_mon];
            v_tm_mon--;
        }
        m += (Time64_T) days_in_month[leap][v_tm_mon];
    }

    p->tm_year = year;
    if( p->tm_year != year ) {
#ifdef EOVERFLOW
        errno = EOVERFLOW;
#endif
        return NULL;
    }

    p->tm_mday = (int) m + 1;
    p->tm_yday = (int) julian_days_by_month[leap][v_tm_mon] + m;
    p->tm_sec = v_tm_sec, p->tm_min = v_tm_min, p->tm_hour = v_tm_hour,
        p->tm_mon = v_tm_mon, p->tm_wday = v_tm_wday;

    assert(_check_tm(p));

    return p;
}


struct tm *localtime64_r (const Time64_T *time, struct tm *local_tm)
{
    time_t safe_time;
    struct tm gm_tm;
    Year orig_year;
    int month_diff;

    /* Use the system localtime() if time_t is small enough */
    if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
        safe_time = *time;
        localtime_r(&safe_time, local_tm);
        assert(_check_tm(local_tm));
        return local_tm;
    }

    if( gmtime64_r(time, &gm_tm) == NULL )
        return NULL;

    orig_year = gm_tm.tm_year;

    if (gm_tm.tm_year > (2037 - 1900) ||
        gm_tm.tm_year < (1902 - 1900)
       )
    {
        gm_tm.tm_year = _safe_year(gm_tm.tm_year + 1900) - 1900;
    }

    safe_time = TIMEGM(&gm_tm);
    if( localtime_r(&safe_time, local_tm) == NULL )
        return NULL;

    local_tm->tm_year = orig_year;
    if( local_tm->tm_year != orig_year ) {
#ifdef EOVERFLOW
        errno = EOVERFLOW;
#endif
        return NULL;
    }


    month_diff = local_tm->tm_mon - gm_tm.tm_mon;

    /*  When localtime is Dec 31st previous year and
        gmtime is Jan 1st next year.
    */
    if( month_diff == 11 ) {
        local_tm->tm_year--;
    }

    /*  When localtime is Jan 1st, next year and
        gmtime is Dec 31st, previous year.
    */
    if( month_diff == -11 ) {
        local_tm->tm_year++;
    }

    /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
       in a non-leap xx00.  There is one point in the cycle
       we can't account for which the safe xx00 year is a leap
       year.  So we need to correct for Dec 31st comming out as
       the 366th day of the year.
    */
    if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
        local_tm->tm_yday--;

    assert(_check_tm(local_tm));

    return local_tm;
}
Commit	Line	Data
a272e669 MS	1	/*
	2
	3	Copyright (c) 2007-2008 Michael G Schwern
	4
	5	This software originally derived from Paul Sheer's pivotal_gmtime_r.c.
	6
	7	The MIT License:
	8
	9	Permission is hereby granted, free of charge, to any person obtaining a copy
	10	of this software and associated documentation files (the "Software"), to deal
	11	in the Software without restriction, including without limitation the rights
	12	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	13	copies of the Software, and to permit persons to whom the Software is
	14	furnished to do so, subject to the following conditions:
	15
	16	The above copyright notice and this permission notice shall be included in
	17	all copies or substantial portions of the Software.
	18
	19	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	20	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	21	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	22	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	23	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	24	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	25	THE SOFTWARE.
	26
	27	*/
	28
	29	/*
	30
	31	Programmers who have available to them 64-bit time values as a 'long
	32	long' type can use localtime64_r() and gmtime64_r() which correctly
	33	converts the time even on 32-bit systems. Whether you have 64-bit time
	34	values will depend on the operating system.
	35
	36	localtime64_r() is a 64-bit equivalent of localtime_r().
	37
	38	gmtime64_r() is a 64-bit equivalent of gmtime_r().
	39
	40	*/
	41
af9b2bf5 MS	42	#include "localtime64.h"
af9b2bf5 MS	43
a272e669 MS	44	static const int days_in_month[2][12] = {
	45	{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
	46	{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
	47	};
	48
	49	static const int julian_days_by_month[2][12] = {
	50	{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
	51	{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
	52	};
	53
	54	static const int length_of_year[2] = { 365, 366 };
	55
	56	/* Number of days in a 400 year Gregorian cycle */
	57	static const int years_in_gregorian_cycle = 400;
	58	static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1;
	59
	60	/* 28 year calendar cycle between 2010 and 2037 */
	61	static const int safe_years[28] = {
	62	2016, 2017, 2018, 2019,
	63	2020, 2021, 2022, 2023,
	64	2024, 2025, 2026, 2027,
	65	2028, 2029, 2030, 2031,
	66	2032, 2033, 2034, 2035,
	67	2036, 2037, 2010, 2011,
	68	2012, 2013, 2014, 2015
	69	};
	70
ea722b76 MS	71	#define SOLAR_CYCLE_LENGTH 28
ea722b76 MS	72	static const int dow_year_start[SOLAR_CYCLE_LENGTH] = {
003c3b95 MS	73	5, 0, 1, 2, /* 0 2016 - 2019 */
	74	3, 5, 6, 0, /* 4 */
	75	1, 3, 4, 5, /* 8 */
	76	6, 1, 2, 3, /* 12 */
	77	4, 6, 0, 1, /* 16 */
	78	2, 4, 5, 6, /* 20 2036, 2037, 2010, 2011 */
	79	0, 2, 3, 4 /* 24 2012, 2013, 2014, 2015 */
a272e669 MS	80	};
a272e669 MS	81
9af24521 MS	82	/* Let's assume people are going to be looking for dates in the future.
	83	Let's provide some cheats so you can skip ahead.
	84	This has a 4x speed boost when near 2008.
	85	*/
	86	/* Number of days since epoch on Jan 1st, 2008 GMT */
	87	#define CHEAT_DAYS (1199145600 / 24 / 60 / 60)
	88	#define CHEAT_YEARS 108
a272e669 MS	89
	90	#define IS_LEAP(n) ((!(((n) + 1900) % 400) \|\| (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
	91	#define WRAP(a,b,m) ((a) = ((a) < 0 ) ? ((b)--, (a) + (m)) : (a))
	92
7bda3dfc MS	93	#define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
	94	USE_SYSTEM_LOCALTIME && \
	95	(a) <= SYSTEM_LOCALTIME_MAX && \
	96	(a) >= SYSTEM_LOCALTIME_MIN \
	97	)
	98	#define SHOULD_USE_SYSTEM_GMTIME(a) ( \
	99	USE_SYSTEM_GMTIME && \
	100	(a) <= SYSTEM_GMTIME_MAX && \
	101	(a) >= SYSTEM_GMTIME_MIN \
	102	)
a64acb40 MS	103
a64acb40 MS	104
9af24521	105	int _is_exception_century(Int64 year)
a272e669 MS	106	{
	107	int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
	108	/* printf("is_exception_century: %s\n", is_exception ? "yes" : "no"); */
	109
	110	return(is_exception);
	111	}
	112
9af24521 MS	113
	114	/* timegm() is a GNU extension, so emulate it here if we need it */
	115	#ifdef HAS_TIMEGM
	116	# define TIMEGM(n) timegm(n);
	117	#else
ea722b76	118	# define TIMEGM(n) ((time_t)timegm64(n));
a272e669 MS	119	#endif
a272e669 MS	120
ea722b76 MS	121	Time64_T timegm64(struct tm *date) {
	122	int days = 0;
	123	Int64 seconds = 0;
	124	Int64 year;
a272e669	125
9af24521 MS	126	if( date->tm_year > 70 ) {
	127	year = 70;
	128	while( year < date->tm_year ) {
	129	days += length_of_year[IS_LEAP(year)];
	130	year++;
a272e669 MS	131	}
a272e669 MS	132	}
9af24521 MS	133	else if ( date->tm_year < 70 ) {
	134	year = 69;
	135	do {
	136	days -= length_of_year[IS_LEAP(year)];
	137	year--;
	138	} while( year >= date->tm_year );
	139	}
	140
	141	days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
	142	days += date->tm_mday - 1;
	143
ea722b76 MS	144	/* Avoid overflowing the days integer */
	145	seconds = days;
	146	seconds = seconds * 60 * 60 * 24;
	147
9af24521 MS	148	seconds += date->tm_hour * 60 * 60;
	149	seconds += date->tm_min * 60;
	150	seconds += date->tm_sec;
	151
ea722b76	152	return((Time64_T)seconds);
9af24521 MS	153	}
	154
	155
af9b2bf5	156	int _check_tm(struct tm *tm)
9af24521	157	{
9af24521	158	/* Don't forget leap seconds */
af9b2bf5	159	assert(tm->tm_sec >= 0);
9af24521 MS	160	assert(tm->tm_sec <= 61);
9af24521 MS	161
af9b2bf5	162	assert(tm->tm_min >= 0);
9af24521 MS	163	assert(tm->tm_min <= 59);
	164
	165	assert(tm->tm_hour >= 0);
	166	assert(tm->tm_hour <= 23);
	167
	168	assert(tm->tm_mday >= 1);
af9b2bf5	169	assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
9af24521 MS	170
	171	assert(tm->tm_mon >= 0);
	172	assert(tm->tm_mon <= 11);
	173
	174	assert(tm->tm_wday >= 0);
	175	assert(tm->tm_wday <= 6);
	176
	177	assert(tm->tm_yday >= 0);
af9b2bf5	178	assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
9af24521 MS	179
	180	#ifdef HAS_TM_TM_GMTOFF
	181	assert(tm->tm_gmtoff >= -24 * 60 * 60);
	182	assert(tm->tm_gmtoff <= 24 * 60 * 60);
	183	#endif
af9b2bf5 MS	184
af9b2bf5 MS	185	return 1;
a272e669	186	}
a64acb40	187
a272e669 MS	188
	189	/* The exceptional centuries without leap years cause the cycle to
	190	shift by 16
	191	*/
750c447b	192	Year _cycle_offset(Year year)
a272e669	193	{
750c447b MS	194	const Year start_year = 2000;
	195	Year year_diff = year - start_year;
	196	Year exceptions;
003c3b95 MS	197
	198	if( year > start_year )
	199	year_diff--;
	200
750c447b MS	201	exceptions = year_diff / 100;
750c447b MS	202	exceptions -= year_diff / 400;
a272e669	203
003c3b95 MS	204	/*
	205	fprintf(stderr, "# year: %lld, exceptions: %lld, year_diff: %lld\n",
	206	year, exceptions, year_diff);
	207	*/
a272e669 MS	208
	209	return exceptions * 16;
	210	}
	211
	212	/* For a given year after 2038, pick the latest possible matching
	213	year in the 28 year calendar cycle.
ea722b76 MS	214
	215	A matching year...
	216	1) Starts on the same day of the week.
	217	2) Has the same leap year status.
	218
	219	This is so the calendars match up.
	220
	221	Also the previous year must match. When doing Jan 1st you might
	222	wind up on Dec 31st the previous year when doing a -UTC time zone.
003c3b95 MS	223
	224	Finally, the next year must have the same start day of week. This
	225	is for Dec 31st with a +UTC time zone.
	226	It doesn't need the same leap year status since we only care about
	227	January 1st.
a272e669	228	*/
750c447b	229	int _safe_year(Year year)
a272e669 MS	230	{
a272e669 MS	231	int safe_year;
750c447b	232	Year year_cycle = year + _cycle_offset(year);
a272e669 MS	233
	234	/* Change non-leap xx00 years to an equivalent */
	235	if( _is_exception_century(year) )
	236	year_cycle += 11;
	237
003c3b95 MS	238	/* Also xx01 years, since the previous year will be wrong */
	239	if( _is_exception_century(year - 1) )
	240	year_cycle += 17;
	241
a272e669	242	year_cycle %= SOLAR_CYCLE_LENGTH;
ea722b76 MS	243	if( year_cycle < 0 )
ea722b76 MS	244	year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
a272e669	245
003c3b95 MS	246	assert( year_cycle >= 0 );
003c3b95 MS	247	assert( year_cycle < SOLAR_CYCLE_LENGTH );
a272e669 MS	248	safe_year = safe_years[year_cycle];
	249
	250	assert(safe_year <= 2037 && safe_year >= 2010);
	251
	252	/*
	253	printf("year: %d, year_cycle: %d, safe_year: %d\n",
	254	year, year_cycle, safe_year);
	255	*/
	256
	257	return safe_year;
	258	}
	259
750c447b	260
a272e669 MS	261	struct tm gmtime64_r (const Time64_T in_time, struct tm *p)
	262	{
	263	int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
9af24521	264	Int64 v_tm_tday;
a272e669	265	int leap;
9af24521	266	Int64 m;
a272e669	267	Time64_T time = *in_time;
750c447b	268	Year year = 70;
a272e669	269
a64acb40 MS	270	/* Use the system gmtime() if time_t is small enough */
	271	if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
	272	time_t safe_time = *in_time;
750c447b	273	gmtime_r(&safe_time, p);
af9b2bf5	274	assert(_check_tm(p));
a64acb40 MS	275	return p;
	276	}
	277
9af24521	278	#ifdef HAS_TM_TM_GMTOFF
a272e669 MS	279	p->tm_gmtoff = 0;
	280	#endif
	281	p->tm_isdst = 0;
	282
9af24521	283	#ifdef HAS_TM_TM_ZONE
a272e669 MS	284	p->tm_zone = "UTC";
	285	#endif
	286
750c447b	287	v_tm_sec = (int)(time % 60);
a272e669	288	time /= 60;
750c447b	289	v_tm_min = (int)(time % 60);
a272e669	290	time /= 60;
750c447b	291	v_tm_hour = (int)(time % 24);
a272e669 MS	292	time /= 24;
a272e669 MS	293	v_tm_tday = time;
750c447b	294
a272e669 MS	295	WRAP (v_tm_sec, v_tm_min, 60);
	296	WRAP (v_tm_min, v_tm_hour, 60);
	297	WRAP (v_tm_hour, v_tm_tday, 24);
750c447b MS	298
	299	v_tm_wday = (int)((v_tm_tday + 4) % 7);
	300	if (v_tm_wday < 0)
a272e669 MS	301	v_tm_wday += 7;
a272e669 MS	302	m = v_tm_tday;
a272e669	303
9af24521 MS	304	if (m >= CHEAT_DAYS) {
	305	year = CHEAT_YEARS;
	306	m -= CHEAT_DAYS;
	307	}
	308
	309	if (m >= 0) {
a272e669 MS	310	/* Gregorian cycles, this is huge optimization for distant times */
	311	while (m >= (Time64_T) days_in_gregorian_cycle) {
	312	m -= (Time64_T) days_in_gregorian_cycle;
	313	year += years_in_gregorian_cycle;
	314	}
	315
	316	/* Years */
	317	leap = IS_LEAP (year);
	318	while (m >= (Time64_T) length_of_year[leap]) {
	319	m -= (Time64_T) length_of_year[leap];
	320	year++;
	321	leap = IS_LEAP (year);
	322	}
	323
	324	/* Months */
	325	v_tm_mon = 0;
	326	while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
	327	m -= (Time64_T) days_in_month[leap][v_tm_mon];
	328	v_tm_mon++;
	329	}
	330	} else {
9af24521	331	year--;
a272e669 MS	332
	333	/* Gregorian cycles */
	334	while (m < (Time64_T) -days_in_gregorian_cycle) {
	335	m += (Time64_T) days_in_gregorian_cycle;
	336	year -= years_in_gregorian_cycle;
	337	}
	338
	339	/* Years */
	340	leap = IS_LEAP (year);
	341	while (m < (Time64_T) -length_of_year[leap]) {
	342	m += (Time64_T) length_of_year[leap];
	343	year--;
	344	leap = IS_LEAP (year);
	345	}
	346
	347	/* Months */
	348	v_tm_mon = 11;
	349	while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
	350	m += (Time64_T) days_in_month[leap][v_tm_mon];
	351	v_tm_mon--;
	352	}
	353	m += (Time64_T) days_in_month[leap][v_tm_mon];
	354	}
	355
	356	p->tm_year = year;
	357	if( p->tm_year != year ) {
9af24521	358	#ifdef EOVERFLOW
a272e669	359	errno = EOVERFLOW;
9af24521	360	#endif
a272e669 MS	361	return NULL;
	362	}
	363
	364	p->tm_mday = (int) m + 1;
750c447b	365	p->tm_yday = (int) julian_days_by_month[leap][v_tm_mon] + m;
a272e669 MS	366	p->tm_sec = v_tm_sec, p->tm_min = v_tm_min, p->tm_hour = v_tm_hour,
	367	p->tm_mon = v_tm_mon, p->tm_wday = v_tm_wday;
	368
af9b2bf5	369	assert(_check_tm(p));
a272e669 MS	370
	371	return p;
	372	}
	373
	374
	375	struct tm localtime64_r (const Time64_T time, struct tm *local_tm)
	376	{
	377	time_t safe_time;
	378	struct tm gm_tm;
750c447b	379	Year orig_year;
a272e669 MS	380	int month_diff;
a272e669 MS	381
a64acb40 MS	382	/* Use the system localtime() if time_t is small enough */
	383	if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
	384	safe_time = *time;
	385	localtime_r(&safe_time, local_tm);
af9b2bf5	386	assert(_check_tm(local_tm));
a64acb40 MS	387	return local_tm;
	388	}
	389
af832814 MS	390	if( gmtime64_r(time, &gm_tm) == NULL )
	391	return NULL;
	392
a272e669 MS	393	orig_year = gm_tm.tm_year;
a272e669 MS	394
c07fe26c MS	395	if (gm_tm.tm_year > (2037 - 1900) \|\|
	396	gm_tm.tm_year < (1902 - 1900)
	397	)
	398	{
a272e669	399	gm_tm.tm_year = _safe_year(gm_tm.tm_year + 1900) - 1900;
c07fe26c	400	}
a272e669	401
9af24521	402	safe_time = TIMEGM(&gm_tm);
af832814 MS	403	if( localtime_r(&safe_time, local_tm) == NULL )
af832814 MS	404	return NULL;
a272e669 MS	405
a272e669 MS	406	local_tm->tm_year = orig_year;
af832814 MS	407	if( local_tm->tm_year != orig_year ) {
	408	#ifdef EOVERFLOW
	409	errno = EOVERFLOW;
	410	#endif
	411	return NULL;
	412	}
	413
	414
a272e669 MS	415	month_diff = local_tm->tm_mon - gm_tm.tm_mon;
	416
	417	/* When localtime is Dec 31st previous year and
	418	gmtime is Jan 1st next year.
	419	*/
	420	if( month_diff == 11 ) {
	421	local_tm->tm_year--;
	422	}
	423
	424	/* When localtime is Jan 1st, next year and
	425	gmtime is Dec 31st, previous year.
	426	*/
	427	if( month_diff == -11 ) {
	428	local_tm->tm_year++;
	429	}
	430
	431	/* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
	432	in a non-leap xx00. There is one point in the cycle
	433	we can't account for which the safe xx00 year is a leap
	434	year. So we need to correct for Dec 31st comming out as
	435	the 366th day of the year.
	436	*/
	437	if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
	438	local_tm->tm_yday--;
	439
af9b2bf5	440	assert(_check_tm(local_tm));
a272e669 MS	441
	442	return local_tm;
	443	}