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 #ifdef USE_SYSTEM_LOCALTIME
94 # define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
95 (a) <= SYSTEM_LOCALTIME_MAX && \
96 (a) >= SYSTEM_LOCALTIME_MIN \
99 # define SHOULD_USE_SYSTEM_LOCALTIME(a) (0)
102 #ifdef USE_SYSTEM_GMTIME
103 # define SHOULD_USE_SYSTEM_GMTIME(a) ( \
104 (a) <= SYSTEM_GMTIME_MAX && \
105 (a) >= SYSTEM_GMTIME_MIN \
108 # define SHOULD_USE_SYSTEM_GMTIME(a) (0)
112 # define TRACE(format, ...) (fprintf(stderr, format, __VA_ARGS__))
113 # define TRACE_NO_VARS(format) (fprintf(stderr, format))
115 # define TRACE(format, ...) ((void)0)
116 # define TRACE_NO_VARS(format) ((void)0)
119 static int is_exception_century(Year year)
121 int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
122 TRACE("# is_exception_century: %s\n", is_exception ? "yes" : "no");
124 return(is_exception);
128 Time64_T timegm64(struct TM *date) {
130 Time64_T seconds = 0;
133 if( date->tm_year > 70 ) {
135 while( year < date->tm_year ) {
136 days += length_of_year[IS_LEAP(year)];
140 else if ( date->tm_year < 70 ) {
143 days -= length_of_year[IS_LEAP(year)];
145 } while( year >= date->tm_year );
148 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
149 days += date->tm_mday - 1;
151 /* Avoid overflowing the days integer */
153 seconds = seconds * 60 * 60 * 24;
155 seconds += date->tm_hour * 60 * 60;
156 seconds += date->tm_min * 60;
157 seconds += date->tm_sec;
163 static int check_tm(struct TM *tm)
165 /* Don't forget leap seconds */
166 assert(tm->tm_sec >= 0);
167 assert(tm->tm_sec <= 61);
169 assert(tm->tm_min >= 0);
170 assert(tm->tm_min <= 59);
172 assert(tm->tm_hour >= 0);
173 assert(tm->tm_hour <= 23);
175 assert(tm->tm_mday >= 1);
176 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
178 assert(tm->tm_mon >= 0);
179 assert(tm->tm_mon <= 11);
181 assert(tm->tm_wday >= 0);
182 assert(tm->tm_wday <= 6);
184 assert(tm->tm_yday >= 0);
185 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
187 #ifdef HAS_TM_TM_GMTOFF
188 assert(tm->tm_gmtoff >= -24 * 60 * 60);
189 assert(tm->tm_gmtoff <= 24 * 60 * 60);
196 /* The exceptional centuries without leap years cause the cycle to
199 static Year cycle_offset(Year year)
201 const Year start_year = 2000;
202 Year year_diff = year - start_year;
205 if( year > start_year )
208 exceptions = year_diff / 100;
209 exceptions -= year_diff / 400;
211 TRACE("# year: %lld, exceptions: %lld, year_diff: %lld\n",
212 year, exceptions, year_diff);
214 return exceptions * 16;
217 /* For a given year after 2038, pick the latest possible matching
218 year in the 28 year calendar cycle.
221 1) Starts on the same day of the week.
222 2) Has the same leap year status.
224 This is so the calendars match up.
226 Also the previous year must match. When doing Jan 1st you might
227 wind up on Dec 31st the previous year when doing a -UTC time zone.
229 Finally, the next year must have the same start day of week. This
230 is for Dec 31st with a +UTC time zone.
231 It doesn't need the same leap year status since we only care about
234 static int safe_year(Year year)
237 Year year_cycle = year + cycle_offset(year);
239 /* Change non-leap xx00 years to an equivalent */
240 if( is_exception_century(year) )
243 /* Also xx01 years, since the previous year will be wrong */
244 if( is_exception_century(year - 1) )
247 year_cycle %= SOLAR_CYCLE_LENGTH;
249 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
251 assert( year_cycle >= 0 );
252 assert( year_cycle < SOLAR_CYCLE_LENGTH );
253 safe_year = safe_years[year_cycle];
255 assert(safe_year <= 2037 && safe_year >= 2010);
257 TRACE("# year: %lld, year_cycle: %lld, safe_year: %d\n",
258 year, year_cycle, safe_year);
264 void copy_tm_to_TM(const struct tm *src, struct TM *dest) {
266 memset(dest, 0, sizeof(*dest));
270 dest->tm_sec = src->tm_sec;
271 dest->tm_min = src->tm_min;
272 dest->tm_hour = src->tm_hour;
273 dest->tm_mday = src->tm_mday;
274 dest->tm_mon = src->tm_mon;
275 dest->tm_year = (Year)src->tm_year;
276 dest->tm_wday = src->tm_wday;
277 dest->tm_yday = src->tm_yday;
278 dest->tm_isdst = src->tm_isdst;
280 # ifdef HAS_TM_TM_GMTOFF
281 dest->tm_gmtoff = src->tm_gmtoff;
284 # ifdef HAS_TM_TM_ZONE
285 dest->tm_zone = src->tm_zone;
289 /* They're the same type */
290 memcpy(dest, src, sizeof(*dest));
296 void copy_TM_to_tm(const struct TM *src, struct tm *dest) {
298 memset(dest, 0, sizeof(*dest));
302 dest->tm_sec = src->tm_sec;
303 dest->tm_min = src->tm_min;
304 dest->tm_hour = src->tm_hour;
305 dest->tm_mday = src->tm_mday;
306 dest->tm_mon = src->tm_mon;
307 dest->tm_year = (int)src->tm_year;
308 dest->tm_wday = src->tm_wday;
309 dest->tm_yday = src->tm_yday;
310 dest->tm_isdst = src->tm_isdst;
312 # ifdef HAS_TM_TM_GMTOFF
313 dest->tm_gmtoff = src->tm_gmtoff;
316 # ifdef HAS_TM_TM_ZONE
317 dest->tm_zone = src->tm_zone;
321 /* They're the same type */
322 memcpy(dest, src, sizeof(*dest));
328 /* Simulate localtime_r() to the best of our ability */
329 struct tm * fake_localtime_r(const time_t *clock, struct tm *result) {
330 const struct tm *static_result = localtime(clock);
332 assert(result != NULL);
334 if( static_result == NULL ) {
335 memset(result, 0, sizeof(*result));
339 memcpy(result, static_result, sizeof(*result));
345 /* Simulate gmtime_r() to the best of our ability */
346 struct tm * fake_gmtime_r(const time_t *clock, struct tm *result) {
347 const struct tm *static_result = gmtime(clock);
349 assert(result != NULL);
351 if( static_result == NULL ) {
352 memset(result, 0, sizeof(*result));
356 memcpy(result, static_result, sizeof(*result));
362 struct TM *gmtime64_r (const Time64_T *in_time, struct TM *p)
364 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
368 Time64_T time = *in_time;
374 /* Use the system gmtime() if time_t is small enough */
375 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
376 time_t safe_time = *in_time;
378 GMTIME_R(&safe_time, &safe_date);
380 copy_tm_to_TM(&safe_date, p);
386 #ifdef HAS_TM_TM_GMTOFF
391 #ifdef HAS_TM_TM_ZONE
395 v_tm_sec = (int)(time % 60);
397 v_tm_min = (int)(time % 60);
399 v_tm_hour = (int)(time % 24);
403 WRAP (v_tm_sec, v_tm_min, 60);
404 WRAP (v_tm_min, v_tm_hour, 60);
405 WRAP (v_tm_hour, v_tm_tday, 24);
407 v_tm_wday = (int)((v_tm_tday + 4) % 7);
412 if (m >= CHEAT_DAYS) {
418 /* Gregorian cycles, this is huge optimization for distant times */
419 cycles = (int)(m / (Time64_T) days_in_gregorian_cycle);
421 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
422 year += (cycles * years_in_gregorian_cycle);
426 leap = IS_LEAP (year);
427 while (m >= (Time64_T) length_of_year[leap]) {
428 m -= (Time64_T) length_of_year[leap];
430 leap = IS_LEAP (year);
435 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
436 m -= (Time64_T) days_in_month[leap][v_tm_mon];
442 /* Gregorian cycles */
443 cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1);
445 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
446 year += (cycles * years_in_gregorian_cycle);
450 leap = IS_LEAP (year);
451 while (m < (Time64_T) -length_of_year[leap]) {
452 m += (Time64_T) length_of_year[leap];
454 leap = IS_LEAP (year);
459 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
460 m += (Time64_T) days_in_month[leap][v_tm_mon];
463 m += (Time64_T) days_in_month[leap][v_tm_mon];
467 if( p->tm_year != year ) {
474 /* At this point m is less than a year so casting to an int is safe */
475 p->tm_mday = (int) m + 1;
476 p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
477 p->tm_sec = v_tm_sec;
478 p->tm_min = v_tm_min;
479 p->tm_hour = v_tm_hour;
480 p->tm_mon = v_tm_mon;
481 p->tm_wday = v_tm_wday;
489 struct TM *localtime64_r (const Time64_T *time, struct TM *local_tm)
497 assert(local_tm != NULL);
499 /* Use the system localtime() if time_t is small enough */
500 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
503 TRACE("Using system localtime for %lld\n", *time);
505 LOCALTIME_R(&safe_time, &safe_date);
507 copy_tm_to_TM(&safe_date, local_tm);
508 assert(check_tm(local_tm));
513 if( gmtime64_r(time, &gm_tm) == NULL ) {
514 TRACE("gmtime64_r returned null for %lld\n", *time);
518 orig_year = gm_tm.tm_year;
520 if (gm_tm.tm_year > (2037 - 1900) ||
521 gm_tm.tm_year < (1970 - 1900)
524 TRACE("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year);
525 gm_tm.tm_year = safe_year((Year)(gm_tm.tm_year + 1900)) - 1900;
528 safe_time = timegm64(&gm_tm);
529 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
530 TRACE("localtime_r(%d) returned NULL\n", (int)safe_time);
534 copy_tm_to_TM(&safe_date, local_tm);
536 local_tm->tm_year = orig_year;
537 if( local_tm->tm_year != orig_year ) {
538 TRACE("tm_year overflow: tm_year %lld, orig_year %lld\n",
539 (Year)local_tm->tm_year, (Year)orig_year);
548 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
550 /* When localtime is Dec 31st previous year and
551 gmtime is Jan 1st next year.
553 if( month_diff == 11 ) {
557 /* When localtime is Jan 1st, next year and
558 gmtime is Dec 31st, previous year.
560 if( month_diff == -11 ) {
564 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
565 in a non-leap xx00. There is one point in the cycle
566 we can't account for which the safe xx00 year is a leap
567 year. So we need to correct for Dec 31st comming out as
568 the 366th day of the year.
570 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
573 assert(check_tm(local_tm));