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)
111 /* Multi varadic macros are a C99 thing, alas */
113 # define TRACE(format) (fprintf(stderr, format))
114 # define TRACE1(format, var1) (fprintf(stderr, format, var1))
115 # define TRACE2(format, var1, var2) (fprintf(stderr, format, var1, var2))
116 # define TRACE3(format, var1, var2, var3) (fprintf(stderr, format, var1, var2, var3))
118 # define TRACE(format) ((void)0)
119 # define TRACE1(format, var1) ((void)0)
120 # define TRACE2(format, var1, var2) ((void)0)
121 # define TRACE3(format, var1, var2, var3) ((void)0)
124 static int is_exception_century(Year year)
126 int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
127 TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");
129 return(is_exception);
133 Time64_T timegm64(struct TM *date) {
135 Time64_T seconds = 0;
138 if( date->tm_year > 70 ) {
140 while( year < date->tm_year ) {
141 days += length_of_year[IS_LEAP(year)];
145 else if ( date->tm_year < 70 ) {
148 days -= length_of_year[IS_LEAP(year)];
150 } while( year >= date->tm_year );
153 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
154 days += date->tm_mday - 1;
156 /* Avoid overflowing the days integer */
158 seconds = seconds * 60 * 60 * 24;
160 seconds += date->tm_hour * 60 * 60;
161 seconds += date->tm_min * 60;
162 seconds += date->tm_sec;
168 static int check_tm(struct TM *tm)
170 /* Don't forget leap seconds */
171 assert(tm->tm_sec >= 0);
172 assert(tm->tm_sec <= 61);
174 assert(tm->tm_min >= 0);
175 assert(tm->tm_min <= 59);
177 assert(tm->tm_hour >= 0);
178 assert(tm->tm_hour <= 23);
180 assert(tm->tm_mday >= 1);
181 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
183 assert(tm->tm_mon >= 0);
184 assert(tm->tm_mon <= 11);
186 assert(tm->tm_wday >= 0);
187 assert(tm->tm_wday <= 6);
189 assert(tm->tm_yday >= 0);
190 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
192 #ifdef HAS_TM_TM_GMTOFF
193 assert(tm->tm_gmtoff >= -24 * 60 * 60);
194 assert(tm->tm_gmtoff <= 24 * 60 * 60);
201 /* The exceptional centuries without leap years cause the cycle to
204 static Year cycle_offset(Year year)
206 const Year start_year = 2000;
207 Year year_diff = year - start_year;
210 if( year > start_year )
213 exceptions = year_diff / 100;
214 exceptions -= year_diff / 400;
216 TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
217 year, exceptions, year_diff);
219 return exceptions * 16;
222 /* For a given year after 2038, pick the latest possible matching
223 year in the 28 year calendar cycle.
226 1) Starts on the same day of the week.
227 2) Has the same leap year status.
229 This is so the calendars match up.
231 Also the previous year must match. When doing Jan 1st you might
232 wind up on Dec 31st the previous year when doing a -UTC time zone.
234 Finally, the next year must have the same start day of week. This
235 is for Dec 31st with a +UTC time zone.
236 It doesn't need the same leap year status since we only care about
239 static int safe_year(Year year)
242 Year year_cycle = year + cycle_offset(year);
244 /* Change non-leap xx00 years to an equivalent */
245 if( is_exception_century(year) )
248 /* Also xx01 years, since the previous year will be wrong */
249 if( is_exception_century(year - 1) )
252 year_cycle %= SOLAR_CYCLE_LENGTH;
254 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
256 assert( year_cycle >= 0 );
257 assert( year_cycle < SOLAR_CYCLE_LENGTH );
258 safe_year = safe_years[year_cycle];
260 assert(safe_year <= 2037 && safe_year >= 2010);
262 TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
263 year, year_cycle, safe_year);
269 void copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) {
271 memset(dest, 0, sizeof(*dest));
275 dest->tm_sec = src->tm_sec;
276 dest->tm_min = src->tm_min;
277 dest->tm_hour = src->tm_hour;
278 dest->tm_mday = src->tm_mday;
279 dest->tm_mon = src->tm_mon;
280 dest->tm_year = (Year)src->tm_year;
281 dest->tm_wday = src->tm_wday;
282 dest->tm_yday = src->tm_yday;
283 dest->tm_isdst = src->tm_isdst;
285 # ifdef HAS_TM_TM_GMTOFF
286 dest->tm_gmtoff = src->tm_gmtoff;
289 # ifdef HAS_TM_TM_ZONE
290 dest->tm_zone = src->tm_zone;
294 /* They're the same type */
295 memcpy(dest, src, sizeof(*dest));
301 void copy_big_TM_to_little_tm(const struct TM *src, struct tm *dest) {
303 memset(dest, 0, sizeof(*dest));
307 dest->tm_sec = src->tm_sec;
308 dest->tm_min = src->tm_min;
309 dest->tm_hour = src->tm_hour;
310 dest->tm_mday = src->tm_mday;
311 dest->tm_mon = src->tm_mon;
312 dest->tm_year = (int)src->tm_year;
313 dest->tm_wday = src->tm_wday;
314 dest->tm_yday = src->tm_yday;
315 dest->tm_isdst = src->tm_isdst;
317 # ifdef HAS_TM_TM_GMTOFF
318 dest->tm_gmtoff = src->tm_gmtoff;
321 # ifdef HAS_TM_TM_ZONE
322 dest->tm_zone = src->tm_zone;
326 /* They're the same type */
327 memcpy(dest, src, sizeof(*dest));
333 /* Simulate localtime_r() to the best of our ability */
334 struct tm * fake_localtime_r(const time_t *clock, struct tm *result) {
335 dTHX; /* in case the following is defined as Perl_my_localtime(aTHX_ ...) */
336 const struct tm *static_result = localtime(clock);
338 assert(result != NULL);
340 if( static_result == NULL ) {
341 memset(result, 0, sizeof(*result));
345 memcpy(result, static_result, sizeof(*result));
351 /* Simulate gmtime_r() to the best of our ability */
352 struct tm * fake_gmtime_r(const time_t *clock, struct tm *result) {
353 dTHX; /* in case the following is defined as Perl_my_gmtime(aTHX_ ...) */
354 const struct tm *static_result = gmtime(clock);
356 assert(result != NULL);
358 if( static_result == NULL ) {
359 memset(result, 0, sizeof(*result));
363 memcpy(result, static_result, sizeof(*result));
369 struct TM *gmtime64_r (const Time64_T *in_time, struct TM *p)
371 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
375 Time64_T time = *in_time;
381 /* Use the system gmtime() if time_t is small enough */
382 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
383 time_t safe_time = *in_time;
385 GMTIME_R(&safe_time, &safe_date);
387 copy_little_tm_to_big_TM(&safe_date, p);
393 #ifdef HAS_TM_TM_GMTOFF
398 #ifdef HAS_TM_TM_ZONE
402 v_tm_sec = (int)(time % 60);
404 v_tm_min = (int)(time % 60);
406 v_tm_hour = (int)(time % 24);
410 WRAP (v_tm_sec, v_tm_min, 60);
411 WRAP (v_tm_min, v_tm_hour, 60);
412 WRAP (v_tm_hour, v_tm_tday, 24);
414 v_tm_wday = (int)((v_tm_tday + 4) % 7);
419 if (m >= CHEAT_DAYS) {
425 /* Gregorian cycles, this is huge optimization for distant times */
426 cycles = (int)(m / (Time64_T) days_in_gregorian_cycle);
428 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
429 year += (cycles * years_in_gregorian_cycle);
433 leap = IS_LEAP (year);
434 while (m >= (Time64_T) length_of_year[leap]) {
435 m -= (Time64_T) length_of_year[leap];
437 leap = IS_LEAP (year);
442 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
443 m -= (Time64_T) days_in_month[leap][v_tm_mon];
449 /* Gregorian cycles */
450 cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1);
452 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
453 year += (cycles * years_in_gregorian_cycle);
457 leap = IS_LEAP (year);
458 while (m < (Time64_T) -length_of_year[leap]) {
459 m += (Time64_T) length_of_year[leap];
461 leap = IS_LEAP (year);
466 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
467 m += (Time64_T) days_in_month[leap][v_tm_mon];
470 m += (Time64_T) days_in_month[leap][v_tm_mon];
474 if( p->tm_year != year ) {
481 /* At this point m is less than a year so casting to an int is safe */
482 p->tm_mday = (int) m + 1;
483 p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
484 p->tm_sec = v_tm_sec;
485 p->tm_min = v_tm_min;
486 p->tm_hour = v_tm_hour;
487 p->tm_mon = v_tm_mon;
488 p->tm_wday = v_tm_wday;
496 struct TM *localtime64_r (const Time64_T *time, struct TM *local_tm)
504 assert(local_tm != NULL);
506 /* Use the system localtime() if time_t is small enough */
507 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
510 TRACE1("Using system localtime for %lld\n", *time);
512 LOCALTIME_R(&safe_time, &safe_date);
514 copy_little_tm_to_big_TM(&safe_date, local_tm);
515 assert(check_tm(local_tm));
520 if( gmtime64_r(time, &gm_tm) == NULL ) {
521 TRACE1("gmtime64_r returned null for %lld\n", *time);
525 orig_year = gm_tm.tm_year;
527 if (gm_tm.tm_year > (2037 - 1900) ||
528 gm_tm.tm_year < (1970 - 1900)
531 TRACE1("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year);
532 gm_tm.tm_year = safe_year((Year)(gm_tm.tm_year + 1900)) - 1900;
535 safe_time = timegm64(&gm_tm);
536 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
537 TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time);
541 copy_little_tm_to_big_TM(&safe_date, local_tm);
543 local_tm->tm_year = orig_year;
544 if( local_tm->tm_year != orig_year ) {
545 TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
546 (Year)local_tm->tm_year, (Year)orig_year);
555 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
557 /* When localtime is Dec 31st previous year and
558 gmtime is Jan 1st next year.
560 if( month_diff == 11 ) {
564 /* When localtime is Jan 1st, next year and
565 gmtime is Dec 31st, previous year.
567 if( month_diff == -11 ) {
571 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
572 in a non-leap xx00. There is one point in the cycle
573 we can't account for which the safe xx00 year is a leap
574 year. So we need to correct for Dec 31st comming out as
575 the 366th day of the year.
577 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
580 assert(check_tm(local_tm));