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 S_localtime64_r() is a 64-bit equivalent of localtime_r().
38 S_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 TIME64_TRACE(format) (fprintf(stderr, format))
114 # define TIME64_TRACE1(format, var1) (fprintf(stderr, format, var1))
115 # define TIME64_TRACE2(format, var1, var2) (fprintf(stderr, format, var1, var2))
116 # define TIME64_TRACE3(format, var1, var2, var3) (fprintf(stderr, format, var1, var2, var3))
118 # define TIME64_TRACE(format) ((void)0)
119 # define TIME64_TRACE1(format, var1) ((void)0)
120 # define TIME64_TRACE2(format, var1, var2) ((void)0)
121 # define TIME64_TRACE3(format, var1, var2, var3) ((void)0)
124 static int S_is_exception_century(Year year)
126 int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
127 TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");
129 return(is_exception);
133 static Time64_T S_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;
169 static int S_check_tm(struct TM *tm)
171 /* Don't forget leap seconds */
172 assert(tm->tm_sec >= 0);
173 assert(tm->tm_sec <= 61);
175 assert(tm->tm_min >= 0);
176 assert(tm->tm_min <= 59);
178 assert(tm->tm_hour >= 0);
179 assert(tm->tm_hour <= 23);
181 assert(tm->tm_mday >= 1);
182 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
184 assert(tm->tm_mon >= 0);
185 assert(tm->tm_mon <= 11);
187 assert(tm->tm_wday >= 0);
188 assert(tm->tm_wday <= 6);
190 assert(tm->tm_yday >= 0);
191 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
193 #ifdef HAS_TM_TM_GMTOFF
194 assert(tm->tm_gmtoff >= -24 * 60 * 60);
195 assert(tm->tm_gmtoff <= 24 * 60 * 60);
203 /* The exceptional centuries without leap years cause the cycle to
206 static Year S_cycle_offset(Year year)
208 const Year start_year = 2000;
209 Year year_diff = year - start_year;
212 if( year > start_year )
215 exceptions = year_diff / 100;
216 exceptions -= year_diff / 400;
218 TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
219 year, exceptions, year_diff);
221 return exceptions * 16;
224 /* For a given year after 2038, pick the latest possible matching
225 year in the 28 year calendar cycle.
228 1) Starts on the same day of the week.
229 2) Has the same leap year status.
231 This is so the calendars match up.
233 Also the previous year must match. When doing Jan 1st you might
234 wind up on Dec 31st the previous year when doing a -UTC time zone.
236 Finally, the next year must have the same start day of week. This
237 is for Dec 31st with a +UTC time zone.
238 It doesn't need the same leap year status since we only care about
241 static int S_safe_year(Year year)
244 Year year_cycle = year + S_cycle_offset(year);
246 /* Change non-leap xx00 years to an equivalent */
247 if( S_is_exception_century(year) )
250 /* Also xx01 years, since the previous year will be wrong */
251 if( S_is_exception_century(year - 1) )
254 year_cycle %= SOLAR_CYCLE_LENGTH;
256 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
258 assert( year_cycle >= 0 );
259 assert( year_cycle < SOLAR_CYCLE_LENGTH );
260 safe_year = safe_years[year_cycle];
262 assert(safe_year <= 2037 && safe_year >= 2010);
264 TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
265 year, year_cycle, safe_year);
271 static void S_copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) {
273 memset(dest, 0, sizeof(*dest));
277 dest->tm_sec = src->tm_sec;
278 dest->tm_min = src->tm_min;
279 dest->tm_hour = src->tm_hour;
280 dest->tm_mday = src->tm_mday;
281 dest->tm_mon = src->tm_mon;
282 dest->tm_year = (Year)src->tm_year;
283 dest->tm_wday = src->tm_wday;
284 dest->tm_yday = src->tm_yday;
285 dest->tm_isdst = src->tm_isdst;
287 # ifdef HAS_TM_TM_GMTOFF
288 dest->tm_gmtoff = src->tm_gmtoff;
291 # ifdef HAS_TM_TM_ZONE
292 dest->tm_zone = src->tm_zone;
296 /* They're the same type */
297 memcpy(dest, src, sizeof(*dest));
303 #ifndef HAS_LOCALTIME_R
304 /* Simulate localtime_r() to the best of our ability */
305 static struct tm * S_localtime_r(const time_t *clock, struct tm *result) {
306 dTHX; /* in case the following is defined as Perl_my_localtime(aTHX_ ...) */
307 const struct tm *static_result = localtime(clock);
309 assert(result != NULL);
311 if( static_result == NULL ) {
312 memset(result, 0, sizeof(*result));
316 memcpy(result, static_result, sizeof(*result));
323 /* Simulate gmtime_r() to the best of our ability */
324 static struct tm * S_gmtime_r(const time_t *clock, struct tm *result) {
325 dTHX; /* in case the following is defined as Perl_my_gmtime(aTHX_ ...) */
326 const struct tm *static_result = gmtime(clock);
328 assert(result != NULL);
330 if( static_result == NULL ) {
331 memset(result, 0, sizeof(*result));
335 memcpy(result, static_result, sizeof(*result));
341 static struct TM *S_gmtime64_r (const Time64_T *in_time, struct TM *p)
343 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
347 Time64_T time = *in_time;
353 /* Use the system gmtime() if time_t is small enough */
354 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
355 time_t safe_time = (time_t)*in_time;
357 GMTIME_R(&safe_time, &safe_date);
359 S_copy_little_tm_to_big_TM(&safe_date, p);
360 assert(S_check_tm(p));
365 #ifdef HAS_TM_TM_GMTOFF
370 #ifdef HAS_TM_TM_ZONE
374 v_tm_sec = (int)(time % 60);
376 v_tm_min = (int)(time % 60);
378 v_tm_hour = (int)(time % 24);
382 WRAP (v_tm_sec, v_tm_min, 60);
383 WRAP (v_tm_min, v_tm_hour, 60);
384 WRAP (v_tm_hour, v_tm_tday, 24);
386 v_tm_wday = (int)((v_tm_tday + 4) % 7);
391 if (m >= CHEAT_DAYS) {
397 /* Gregorian cycles, this is huge optimization for distant times */
398 cycles = (int)(m / (Time64_T) days_in_gregorian_cycle);
400 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
401 year += (cycles * years_in_gregorian_cycle);
405 leap = IS_LEAP (year);
406 while (m >= (Time64_T) length_of_year[leap]) {
407 m -= (Time64_T) length_of_year[leap];
409 leap = IS_LEAP (year);
414 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
415 m -= (Time64_T) days_in_month[leap][v_tm_mon];
421 /* Gregorian cycles */
422 cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1);
424 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
425 year += (cycles * years_in_gregorian_cycle);
429 leap = IS_LEAP (year);
430 while (m < (Time64_T) -length_of_year[leap]) {
431 m += (Time64_T) length_of_year[leap];
433 leap = IS_LEAP (year);
438 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
439 m += (Time64_T) days_in_month[leap][v_tm_mon];
442 m += (Time64_T) days_in_month[leap][v_tm_mon];
446 if( p->tm_year != year ) {
453 /* At this point m is less than a year so casting to an int is safe */
454 p->tm_mday = (int) m + 1;
455 p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
456 p->tm_sec = v_tm_sec;
457 p->tm_min = v_tm_min;
458 p->tm_hour = v_tm_hour;
459 p->tm_mon = v_tm_mon;
460 p->tm_wday = v_tm_wday;
462 assert(S_check_tm(p));
468 struct TM *S_localtime64_r (const Time64_T *time, struct TM *local_tm)
476 assert(local_tm != NULL);
478 /* Use the system localtime() if time_t is small enough */
479 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
480 safe_time = (time_t)*time;
482 TIME64_TRACE1("Using system localtime for %lld\n", *time);
484 LOCALTIME_R(&safe_time, &safe_date);
486 S_copy_little_tm_to_big_TM(&safe_date, local_tm);
487 assert(S_check_tm(local_tm));
492 if( S_gmtime64_r(time, &gm_tm) == NULL ) {
493 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time);
497 orig_year = gm_tm.tm_year;
499 if (gm_tm.tm_year > (2037 - 1900) ||
500 gm_tm.tm_year < (1970 - 1900)
503 TIME64_TRACE1("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year);
504 gm_tm.tm_year = S_safe_year((Year)(gm_tm.tm_year + 1900)) - 1900;
507 safe_time = (time_t)S_timegm64(&gm_tm);
508 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
509 TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time);
513 S_copy_little_tm_to_big_TM(&safe_date, local_tm);
515 local_tm->tm_year = orig_year;
516 if( local_tm->tm_year != orig_year ) {
517 TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
518 (Year)local_tm->tm_year, (Year)orig_year);
527 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
529 /* When localtime is Dec 31st previous year and
530 gmtime is Jan 1st next year.
532 if( month_diff == 11 ) {
536 /* When localtime is Jan 1st, next year and
537 gmtime is Dec 31st, previous year.
539 if( month_diff == -11 ) {
543 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
544 in a non-leap xx00. There is one point in the cycle
545 we can't account for which the safe xx00 year is a leap
546 year. So we need to correct for Dec 31st comming out as
547 the 366th day of the year.
549 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
552 assert(S_check_tm(local_tm));