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
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24 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
31 * This thing all things devours:
32 * Birds, beasts, trees, flowers;
33 * Gnaws iron, bites steel;
34 * Grinds hard stones to meal;
35 * Slays king, ruins town,
36 * And beats high mountain down."
38 * Poor Bilbo sat in the dark thinking of all the horrible names of all the
39 * giants and ogres he had ever heard told of in tales, but not one of them had
40 * done all these things. He had a feeling that the answer was quite different
41 * and that he ought to know it, but he could not think of it. He began to get
42 * frightened, and that is bad for thinking. Gollum began to get out of his
43 * boat. He flapped into the water and paddled to the bank; Bilbo could see his
44 * eyes coming towards him. His tongue seemed to stick in his mouth; he wanted
45 * to shout out: "Give me more time! Give me time!" But all that came out with
46 * a sudden squeal was:
50 * Bilbo was saved by pure luck. For that of course was the answer.
52 * [p.84 of _The Hobbit_: "Riddles in the Dark"]
58 Programmers who have available to them 64-bit time values as a 'long
59 long' type can use localtime64_r() and gmtime64_r() which correctly
60 converts the time even on 32-bit systems. Whether you have 64-bit time
61 values will depend on the operating system.
63 Perl_localtime64_r() is a 64-bit equivalent of localtime_r().
65 Perl_gmtime64_r() is a 64-bit equivalent of gmtime_r().
70 #define PERL_IN_TIME64_C
74 static const char days_in_month[2][12] = {
75 {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
76 {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
79 static const short julian_days_by_month[2][12] = {
80 {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
81 {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
84 static const short length_of_year[2] = { 365, 366 };
86 /* Number of days in a 400 year Gregorian cycle */
87 static const Year years_in_gregorian_cycle = 400;
88 static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1;
90 /* 28 year calendar cycle between 2010 and 2037 */
91 #define SOLAR_CYCLE_LENGTH 28
92 static const short safe_years[SOLAR_CYCLE_LENGTH] = {
93 2016, 2017, 2018, 2019,
94 2020, 2021, 2022, 2023,
95 2024, 2025, 2026, 2027,
96 2028, 2029, 2030, 2031,
97 2032, 2033, 2034, 2035,
98 2036, 2037, 2010, 2011,
99 2012, 2013, 2014, 2015
102 /* Let's assume people are going to be looking for dates in the future.
103 Let's provide some cheats so you can skip ahead.
104 This has a 4x speed boost when near 2008.
106 /* Number of days since epoch on Jan 1st, 2008 GMT */
107 #define CHEAT_DAYS (1199145600 / 24 / 60 / 60)
108 #define CHEAT_YEARS 108
110 #define IS_LEAP(n) ((!(((n) + 1900) % 400) || (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
111 #undef WRAP /* some <termios.h> define this */
112 #define WRAP(a,b,m) ((a) = ((a) < 0 ) ? ((b)--, (a) + (m)) : (a))
114 #ifdef USE_SYSTEM_LOCALTIME
115 # define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
116 (a) <= SYSTEM_LOCALTIME_MAX && \
117 (a) >= SYSTEM_LOCALTIME_MIN \
120 # define SHOULD_USE_SYSTEM_LOCALTIME(a) (0)
123 #ifdef USE_SYSTEM_GMTIME
124 # define SHOULD_USE_SYSTEM_GMTIME(a) ( \
125 (a) <= SYSTEM_GMTIME_MAX && \
126 (a) >= SYSTEM_GMTIME_MIN \
129 # define SHOULD_USE_SYSTEM_GMTIME(a) (0)
132 /* Multi varadic macros are a C99 thing, alas */
134 # define TIME64_TRACE(format) (fprintf(stderr, format))
135 # define TIME64_TRACE1(format, var1) (fprintf(stderr, format, var1))
136 # define TIME64_TRACE2(format, var1, var2) (fprintf(stderr, format, var1, var2))
137 # define TIME64_TRACE3(format, var1, var2, var3) (fprintf(stderr, format, var1, var2, var3))
139 # define TIME64_TRACE(format) ((void)0)
140 # define TIME64_TRACE1(format, var1) ((void)0)
141 # define TIME64_TRACE2(format, var1, var2) ((void)0)
142 # define TIME64_TRACE3(format, var1, var2, var3) ((void)0)
145 static int S_is_exception_century(Year year)
147 const int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
148 TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");
150 return(is_exception);
154 static Time64_T S_timegm64(const struct TM *date) {
156 Time64_T seconds = 0;
158 if( date->tm_year > 70 ) {
160 while( year < date->tm_year ) {
161 days += length_of_year[IS_LEAP(year)];
165 else if ( date->tm_year < 70 ) {
168 days -= length_of_year[IS_LEAP(year)];
170 } while( year >= date->tm_year );
173 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
174 days += date->tm_mday - 1;
176 /* Avoid overflowing the days integer */
178 seconds = seconds * 60 * 60 * 24;
180 seconds += date->tm_hour * 60 * 60;
181 seconds += date->tm_min * 60;
182 seconds += date->tm_sec;
189 static int S_check_tm(const struct TM *tm)
191 /* Don't forget leap seconds */
192 assert(tm->tm_sec >= 0);
193 assert(tm->tm_sec <= 61);
195 assert(tm->tm_min >= 0);
196 assert(tm->tm_min <= 59);
198 assert(tm->tm_hour >= 0);
199 assert(tm->tm_hour <= 23);
201 assert(tm->tm_mday >= 1);
202 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
204 assert(tm->tm_mon >= 0);
205 assert(tm->tm_mon <= 11);
207 assert(tm->tm_wday >= 0);
208 assert(tm->tm_wday <= 6);
210 assert(tm->tm_yday >= 0);
211 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
213 #ifdef HAS_TM_TM_GMTOFF
214 assert(tm->tm_gmtoff >= -24 * 60 * 60);
215 assert(tm->tm_gmtoff <= 24 * 60 * 60);
223 /* The exceptional centuries without leap years cause the cycle to
226 static Year S_cycle_offset(Year year)
228 const Year start_year = 2000;
229 Year year_diff = year - start_year;
232 if( year > start_year )
235 exceptions = year_diff / 100;
236 exceptions -= year_diff / 400;
238 TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
239 year, exceptions, year_diff);
241 return exceptions * 16;
244 /* For a given year after 2038, pick the latest possible matching
245 year in the 28 year calendar cycle.
248 1) Starts on the same day of the week.
249 2) Has the same leap year status.
251 This is so the calendars match up.
253 Also the previous year must match. When doing Jan 1st you might
254 wind up on Dec 31st the previous year when doing a -UTC time zone.
256 Finally, the next year must have the same start day of week. This
257 is for Dec 31st with a +UTC time zone.
258 It doesn't need the same leap year status since we only care about
261 static int S_safe_year(Year year)
264 Year year_cycle = year + S_cycle_offset(year);
266 /* Change non-leap xx00 years to an equivalent */
267 if( S_is_exception_century(year) )
270 /* Also xx01 years, since the previous year will be wrong */
271 if( S_is_exception_century(year - 1) )
274 year_cycle %= SOLAR_CYCLE_LENGTH;
276 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
278 assert( year_cycle >= 0 );
279 assert( year_cycle < SOLAR_CYCLE_LENGTH );
280 safe_year = safe_years[year_cycle];
282 assert(safe_year <= 2037 && safe_year >= 2010);
284 TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
285 year, year_cycle, safe_year);
291 static void S_copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) {
295 dest->tm_sec = src->tm_sec;
296 dest->tm_min = src->tm_min;
297 dest->tm_hour = src->tm_hour;
298 dest->tm_mday = src->tm_mday;
299 dest->tm_mon = src->tm_mon;
300 dest->tm_year = (Year)src->tm_year;
301 dest->tm_wday = src->tm_wday;
302 dest->tm_yday = src->tm_yday;
303 dest->tm_isdst = src->tm_isdst;
305 # ifdef HAS_TM_TM_GMTOFF
306 dest->tm_gmtoff = src->tm_gmtoff;
309 # ifdef HAS_TM_TM_ZONE
310 dest->tm_zone = src->tm_zone;
314 /* They're the same type */
315 memcpy(dest, src, sizeof(*dest));
319 struct TM *Perl_gmtime64_r (const Time64_T *in_time, struct TM *p)
321 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
325 Time64_T time = *in_time;
331 /* Use the system gmtime() if time_t is small enough */
332 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
333 time_t safe_time = (time_t)*in_time;
339 /* reentr.h will automatically replace this with a call to gmtime_r()
340 * when appropriate */
341 result = gmtime(&safe_time);
343 assert(result != NULL);
345 #if defined(HAS_GMTIME_R) && defined(USE_REENTRANT_API)
347 PERL_UNUSED_VAR(safe_date);
349 /* Here, no gmtime_r() and is a threaded perl where the result can be
350 * overwritten by a call in another thread. Copy to a safe place,
351 * hopefully before another gmtime that isn't using the mutexes can
352 * jump in and trash this result. */
353 memcpy(&safe_date, result, sizeof(safe_date));
358 S_copy_little_tm_to_big_TM(result, p);
359 assert(S_check_tm(p));
364 #ifdef HAS_TM_TM_GMTOFF
369 #ifdef HAS_TM_TM_ZONE
373 v_tm_sec = (int)Perl_fmod(time, 60.0);
374 time = time >= 0 ? Perl_floor(time / 60.0) : Perl_ceil(time / 60.0);
375 v_tm_min = (int)Perl_fmod(time, 60.0);
376 time = time >= 0 ? Perl_floor(time / 60.0) : Perl_ceil(time / 60.0);
377 v_tm_hour = (int)Perl_fmod(time, 24.0);
378 time = time >= 0 ? Perl_floor(time / 24.0) : Perl_ceil(time / 24.0);
381 WRAP (v_tm_sec, v_tm_min, 60);
382 WRAP (v_tm_min, v_tm_hour, 60);
383 WRAP (v_tm_hour, v_tm_tday, 24);
385 v_tm_wday = (int)Perl_fmod((v_tm_tday + 4.0), 7.0);
390 if (m >= CHEAT_DAYS) {
396 /* Gregorian cycles, this is huge optimization for distant times */
397 const int cycles = (int)Perl_floor(m / (Time64_T) days_in_gregorian_cycle);
399 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
400 year += (cycles * years_in_gregorian_cycle);
404 leap = IS_LEAP (year);
405 while (m >= (Time64_T) length_of_year[leap]) {
406 m -= (Time64_T) length_of_year[leap];
408 leap = IS_LEAP (year);
413 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
414 m -= (Time64_T) days_in_month[leap][v_tm_mon];
422 /* Gregorian cycles */
423 cycles = (int)Perl_ceil((m / (Time64_T) days_in_gregorian_cycle) + 1);
425 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
426 year += (cycles * years_in_gregorian_cycle);
430 leap = IS_LEAP (year);
431 while (m < (Time64_T) -length_of_year[leap]) {
432 m += (Time64_T) length_of_year[leap];
434 leap = IS_LEAP (year);
439 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
440 m += (Time64_T) days_in_month[leap][v_tm_mon];
443 m += (Time64_T) days_in_month[leap][v_tm_mon];
447 if( p->tm_year != year ) {
454 /* At this point m is less than a year so casting to an int is safe */
455 p->tm_mday = (int) m + 1;
456 p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
457 p->tm_sec = v_tm_sec;
458 p->tm_min = v_tm_min;
459 p->tm_hour = v_tm_hour;
460 p->tm_mon = v_tm_mon;
461 p->tm_wday = v_tm_wday;
463 assert(S_check_tm(p));
469 struct TM *Perl_localtime64_r (const Time64_T *time, struct TM *local_tm)
473 const struct tm * result;
475 Year orig_year = 0; /* initialise to avoid spurious compiler warning */
477 const bool use_system = SHOULD_USE_SYSTEM_LOCALTIME(*time);
480 assert(local_tm != NULL);
482 /* Use the system localtime() if time_t is small enough */
484 safe_time = (time_t)*time;
486 TIME64_TRACE1("Using system localtime for %lld\n", *time);
489 if (Perl_gmtime64_r(time, &gm_tm) == NULL) {
490 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time);
494 orig_year = gm_tm.tm_year;
496 if (gm_tm.tm_year > (2037 - 1900) ||
497 gm_tm.tm_year < (1970 - 1900)
500 TIME64_TRACE1("Mapping tm_year %lld to safe_year\n",
501 (Year)gm_tm.tm_year);
502 gm_tm.tm_year = S_safe_year((Year)(gm_tm.tm_year + 1900)) - 1900;
505 safe_time = (time_t)S_timegm64(&gm_tm);
510 /* reentr.h will automatically replace this with a call to localtime_r()
511 * when appropriate */
512 result = localtime(&safe_time);
514 if(UNLIKELY(result == NULL)) {
516 TIME64_TRACE1("localtime(%d) returned NULL\n", (int)safe_time);
520 #if ! defined(USE_REENTRANT_API) || defined(PERL_REENTR_USING_LOCALTIME_R)
522 PERL_UNUSED_VAR(safe_date);
526 /* Here, would be using localtime_r() if it could, meaning there isn't one,
527 * and is a threaded perl where the result can be overwritten by a call in
528 * another thread. Copy to a safe place, hopefully before another
529 * localtime that isn't using the mutexes can jump in and trash this
531 memcpy(&safe_date, result, sizeof(safe_date));
538 S_copy_little_tm_to_big_TM(result, local_tm);
542 local_tm->tm_year = orig_year;
543 if( local_tm->tm_year != orig_year ) {
544 TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
545 (Year)local_tm->tm_year, (Year)orig_year);
553 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
555 /* When localtime is Dec 31st previous year and
556 gmtime is Jan 1st next year.
558 if( month_diff == 11 ) {
562 /* When localtime is Jan 1st, next year and
563 gmtime is Dec 31st, previous year.
565 if( month_diff == -11 ) {
569 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
570 in a non-leap xx00. There is one point in the cycle
571 we can't account for which the safe xx00 year is a leap
572 year. So we need to correct for Dec 31st coming out as
573 the 366th day of the year.
575 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
580 assert(S_check_tm(local_tm));