3 Copyright (c) 2007-2008 Michael G Schwern
5 This software originally derived from Paul Sheer's pivotal_gmtime_r.c.
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:
16 The above copyright notice and this permission notice shall be included in
17 all copies or substantial portions of the Software.
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
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.
36 localtime64_r() is a 64-bit equivalent of localtime_r().
38 gmtime64_r() is a 64-bit equivalent of gmtime_r().
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},
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},
54 static const int length_of_year[2] = { 365, 366 };
56 /* Number of days in a 400 year Gregorian cycle */
57 static const Year years_in_gregorian_cycle = 400;
58 static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1;
60 /* 28 year calendar cycle between 2010 and 2037 */
61 #define SOLAR_CYCLE_LENGTH 28
62 static const int safe_years[SOLAR_CYCLE_LENGTH] = {
63 2016, 2017, 2018, 2019,
64 2020, 2021, 2022, 2023,
65 2024, 2025, 2026, 2027,
66 2028, 2029, 2030, 2031,
67 2032, 2033, 2034, 2035,
68 2036, 2037, 2010, 2011,
69 2012, 2013, 2014, 2015
72 static const int dow_year_start[SOLAR_CYCLE_LENGTH] = {
73 5, 0, 1, 2, /* 0 2016 - 2019 */
78 2, 4, 5, 6, /* 20 2036, 2037, 2010, 2011 */
79 0, 2, 3, 4 /* 24 2012, 2013, 2014, 2015 */
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.
86 /* Number of days since epoch on Jan 1st, 2008 GMT */
87 #define CHEAT_DAYS (1199145600 / 24 / 60 / 60)
88 #define CHEAT_YEARS 108
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))
93 #define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
94 USE_SYSTEM_LOCALTIME && \
95 (a) <= SYSTEM_LOCALTIME_MAX && \
96 (a) >= SYSTEM_LOCALTIME_MIN \
98 #define SHOULD_USE_SYSTEM_GMTIME(a) ( \
99 USE_SYSTEM_GMTIME && \
100 (a) <= SYSTEM_GMTIME_MAX && \
101 (a) >= SYSTEM_GMTIME_MIN \
105 static int is_exception_century(Int64 year)
107 int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
108 /* printf("is_exception_century: %s\n", is_exception ? "yes" : "no"); */
110 return(is_exception);
114 Time64_T timegm64(struct TM *date) {
119 if( date->tm_year > 70 ) {
121 while( year < date->tm_year ) {
122 days += length_of_year[IS_LEAP(year)];
126 else if ( date->tm_year < 70 ) {
129 days -= length_of_year[IS_LEAP(year)];
131 } while( year >= date->tm_year );
134 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
135 days += date->tm_mday - 1;
137 /* Avoid overflowing the days integer */
139 seconds = seconds * 60 * 60 * 24;
141 seconds += date->tm_hour * 60 * 60;
142 seconds += date->tm_min * 60;
143 seconds += date->tm_sec;
145 return((Time64_T)seconds);
149 static int check_tm(struct TM *tm)
151 /* Don't forget leap seconds */
152 assert(tm->tm_sec >= 0);
153 assert(tm->tm_sec <= 61);
155 assert(tm->tm_min >= 0);
156 assert(tm->tm_min <= 59);
158 assert(tm->tm_hour >= 0);
159 assert(tm->tm_hour <= 23);
161 assert(tm->tm_mday >= 1);
162 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
164 assert(tm->tm_mon >= 0);
165 assert(tm->tm_mon <= 11);
167 assert(tm->tm_wday >= 0);
168 assert(tm->tm_wday <= 6);
170 assert(tm->tm_yday >= 0);
171 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
173 #ifdef HAS_TM_TM_GMTOFF
174 assert(tm->tm_gmtoff >= -24 * 60 * 60);
175 assert(tm->tm_gmtoff <= 24 * 60 * 60);
182 /* The exceptional centuries without leap years cause the cycle to
185 static Year cycle_offset(Year year)
187 const Year start_year = 2000;
188 Year year_diff = year - start_year;
191 if( year > start_year )
194 exceptions = year_diff / 100;
195 exceptions -= year_diff / 400;
198 fprintf(stderr, "# year: %lld, exceptions: %lld, year_diff: %lld\n",
199 year, exceptions, year_diff);
202 return exceptions * 16;
205 /* For a given year after 2038, pick the latest possible matching
206 year in the 28 year calendar cycle.
209 1) Starts on the same day of the week.
210 2) Has the same leap year status.
212 This is so the calendars match up.
214 Also the previous year must match. When doing Jan 1st you might
215 wind up on Dec 31st the previous year when doing a -UTC time zone.
217 Finally, the next year must have the same start day of week. This
218 is for Dec 31st with a +UTC time zone.
219 It doesn't need the same leap year status since we only care about
222 static int safe_year(Year year)
225 Year year_cycle = year + cycle_offset(year);
227 /* Change non-leap xx00 years to an equivalent */
228 if( is_exception_century(year) )
231 /* Also xx01 years, since the previous year will be wrong */
232 if( is_exception_century(year - 1) )
235 year_cycle %= SOLAR_CYCLE_LENGTH;
237 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
239 assert( year_cycle >= 0 );
240 assert( year_cycle < SOLAR_CYCLE_LENGTH );
241 safe_year = safe_years[year_cycle];
243 assert(safe_year <= 2037 && safe_year >= 2010);
246 printf("year: %d, year_cycle: %d, safe_year: %d\n",
247 year, year_cycle, safe_year);
254 void copy_tm_to_TM(const struct tm *src, struct TM *dest) {
256 memset(dest, 0, sizeof(*dest));
260 dest->tm_sec = src->tm_sec;
261 dest->tm_min = src->tm_min;
262 dest->tm_hour = src->tm_hour;
263 dest->tm_mday = src->tm_mday;
264 dest->tm_mon = src->tm_mon;
265 dest->tm_year = (Year)src->tm_year;
266 dest->tm_wday = src->tm_wday;
267 dest->tm_yday = src->tm_yday;
268 dest->tm_isdst = src->tm_isdst;
270 # ifdef HAS_TM_TM_GMTOFF
271 dest->tm_gmtoff = src->tm_gmtoff;
274 # ifdef HAS_TM_TM_ZONE
275 dest->tm_zone = src->tm_zone;
279 /* They're the same type */
280 memcpy(dest, src, sizeof(*dest));
286 void copy_TM_to_tm(const struct TM *src, struct tm *dest) {
288 memset(dest, 0, sizeof(*dest));
292 dest->tm_sec = src->tm_sec;
293 dest->tm_min = src->tm_min;
294 dest->tm_hour = src->tm_hour;
295 dest->tm_mday = src->tm_mday;
296 dest->tm_mon = src->tm_mon;
297 dest->tm_year = (int)src->tm_year;
298 dest->tm_wday = src->tm_wday;
299 dest->tm_yday = src->tm_yday;
300 dest->tm_isdst = src->tm_isdst;
302 # ifdef HAS_TM_TM_GMTOFF
303 dest->tm_gmtoff = src->tm_gmtoff;
306 # ifdef HAS_TM_TM_ZONE
307 dest->tm_zone = src->tm_zone;
311 /* They're the same type */
312 memcpy(dest, src, sizeof(*dest));
318 /* Simulate localtime_r() to the best of our ability */
319 struct tm * fake_localtime_r(const time_t *clock, struct tm *result) {
320 const struct tm *static_result = localtime(clock);
322 assert(result != NULL);
324 if( static_result == NULL ) {
325 memset(result, 0, sizeof(*result));
329 memcpy(result, static_result, sizeof(*result));
335 /* Simulate gmtime_r() to the best of our ability */
336 struct tm * fake_gmtime_r(const time_t *clock, struct tm *result) {
337 const struct tm *static_result = gmtime(clock);
339 assert(result != NULL);
341 if( static_result == NULL ) {
342 memset(result, 0, sizeof(*result));
346 memcpy(result, static_result, sizeof(*result));
352 struct TM *gmtime64_r (const Time64_T *in_time, struct TM *p)
354 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
358 Time64_T time = *in_time;
364 /* Use the system gmtime() if time_t is small enough */
365 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
366 time_t safe_time = *in_time;
368 GMTIME_R(&safe_time, &safe_date);
370 copy_tm_to_TM(&safe_date, p);
376 #ifdef HAS_TM_TM_GMTOFF
381 #ifdef HAS_TM_TM_ZONE
385 v_tm_sec = (int)(time % 60);
387 v_tm_min = (int)(time % 60);
389 v_tm_hour = (int)(time % 24);
393 WRAP (v_tm_sec, v_tm_min, 60);
394 WRAP (v_tm_min, v_tm_hour, 60);
395 WRAP (v_tm_hour, v_tm_tday, 24);
397 v_tm_wday = (int)((v_tm_tday + 4) % 7);
402 if (m >= CHEAT_DAYS) {
408 /* Gregorian cycles, this is huge optimization for distant times */
409 cycles = floor(m / (Time64_T) days_in_gregorian_cycle);
411 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
412 year += (cycles * years_in_gregorian_cycle);
416 leap = IS_LEAP (year);
417 while (m >= (Time64_T) length_of_year[leap]) {
418 m -= (Time64_T) length_of_year[leap];
420 leap = IS_LEAP (year);
425 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
426 m -= (Time64_T) days_in_month[leap][v_tm_mon];
432 /* Gregorian cycles */
433 cycles = ceil(m / (Time64_T) days_in_gregorian_cycle) + 1;
435 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
436 year += (cycles * years_in_gregorian_cycle);
440 leap = IS_LEAP (year);
441 while (m < (Time64_T) -length_of_year[leap]) {
442 m += (Time64_T) length_of_year[leap];
444 leap = IS_LEAP (year);
449 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
450 m += (Time64_T) days_in_month[leap][v_tm_mon];
453 m += (Time64_T) days_in_month[leap][v_tm_mon];
457 if( p->tm_year != year ) {
464 p->tm_mday = (int) m + 1;
465 p->tm_yday = (int) julian_days_by_month[leap][v_tm_mon] + m;
466 p->tm_sec = v_tm_sec, p->tm_min = v_tm_min, p->tm_hour = v_tm_hour,
467 p->tm_mon = v_tm_mon, p->tm_wday = v_tm_wday;
475 struct TM *localtime64_r (const Time64_T *time, struct TM *local_tm)
483 assert(local_tm != NULL);
485 /* Use the system localtime() if time_t is small enough */
486 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
489 LOCALTIME_R(&safe_time, &safe_date);
491 copy_tm_to_TM(&safe_date, local_tm);
492 assert(check_tm(local_tm));
497 if( gmtime64_r(time, &gm_tm) == NULL )
500 orig_year = gm_tm.tm_year;
502 if (gm_tm.tm_year > (2037 - 1900) ||
503 gm_tm.tm_year < (1902 - 1900)
506 gm_tm.tm_year = safe_year(gm_tm.tm_year + 1900) - 1900;
509 safe_time = timegm64(&gm_tm);
510 if( LOCALTIME_R(&safe_time, &safe_date) == NULL )
513 copy_tm_to_TM(&safe_date, local_tm);
515 local_tm->tm_year = orig_year;
516 if( local_tm->tm_year != orig_year ) {
524 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
526 /* When localtime is Dec 31st previous year and
527 gmtime is Jan 1st next year.
529 if( month_diff == 11 ) {
533 /* When localtime is Jan 1st, next year and
534 gmtime is Dec 31st, previous year.
536 if( month_diff == -11 ) {
540 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
541 in a non-leap xx00. There is one point in the cycle
542 we can't account for which the safe xx00 year is a leap
543 year. So we need to correct for Dec 31st comming out as
544 the 366th day of the year.
546 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
549 assert(check_tm(local_tm));