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 int 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 static const int safe_years[28] = {
62 2016, 2017, 2018, 2019,
63 2020, 2021, 2022, 2023,
64 2024, 2025, 2026, 2027,
65 2028, 2029, 2030, 2031,
66 2032, 2033, 2034, 2035,
67 2036, 2037, 2010, 2011,
68 2012, 2013, 2014, 2015
71 #define SOLAR_CYCLE_LENGTH 28
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 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 /* timegm() is a GNU extension, so emulate it here if we need it */
116 # define TIMEGM(n) timegm(n);
118 # define TIMEGM(n) ((time_t)timegm64(n));
121 Time64_T timegm64(struct tm *date) {
126 if( date->tm_year > 70 ) {
128 while( year < date->tm_year ) {
129 days += length_of_year[IS_LEAP(year)];
133 else if ( date->tm_year < 70 ) {
136 days -= length_of_year[IS_LEAP(year)];
138 } while( year >= date->tm_year );
141 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
142 days += date->tm_mday - 1;
144 /* Avoid overflowing the days integer */
146 seconds = seconds * 60 * 60 * 24;
148 seconds += date->tm_hour * 60 * 60;
149 seconds += date->tm_min * 60;
150 seconds += date->tm_sec;
152 return((Time64_T)seconds);
156 int _check_tm(struct tm *tm)
158 /* Don't forget leap seconds */
159 assert(tm->tm_sec >= 0);
160 assert(tm->tm_sec <= 61);
162 assert(tm->tm_min >= 0);
163 assert(tm->tm_min <= 59);
165 assert(tm->tm_hour >= 0);
166 assert(tm->tm_hour <= 23);
168 assert(tm->tm_mday >= 1);
169 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
171 assert(tm->tm_mon >= 0);
172 assert(tm->tm_mon <= 11);
174 assert(tm->tm_wday >= 0);
175 assert(tm->tm_wday <= 6);
177 assert(tm->tm_yday >= 0);
178 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
180 #ifdef HAS_TM_TM_GMTOFF
181 assert(tm->tm_gmtoff >= -24 * 60 * 60);
182 assert(tm->tm_gmtoff <= 24 * 60 * 60);
189 /* The exceptional centuries without leap years cause the cycle to
192 Year _cycle_offset(Year year)
194 const Year start_year = 2000;
195 Year year_diff = year - start_year;
198 if( year > start_year )
201 exceptions = year_diff / 100;
202 exceptions -= year_diff / 400;
205 fprintf(stderr, "# year: %lld, exceptions: %lld, year_diff: %lld\n",
206 year, exceptions, year_diff);
209 return exceptions * 16;
212 /* For a given year after 2038, pick the latest possible matching
213 year in the 28 year calendar cycle.
216 1) Starts on the same day of the week.
217 2) Has the same leap year status.
219 This is so the calendars match up.
221 Also the previous year must match. When doing Jan 1st you might
222 wind up on Dec 31st the previous year when doing a -UTC time zone.
224 Finally, the next year must have the same start day of week. This
225 is for Dec 31st with a +UTC time zone.
226 It doesn't need the same leap year status since we only care about
229 int _safe_year(Year year)
232 Year year_cycle = year + _cycle_offset(year);
234 /* Change non-leap xx00 years to an equivalent */
235 if( _is_exception_century(year) )
238 /* Also xx01 years, since the previous year will be wrong */
239 if( _is_exception_century(year - 1) )
242 year_cycle %= SOLAR_CYCLE_LENGTH;
244 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
246 assert( year_cycle >= 0 );
247 assert( year_cycle < SOLAR_CYCLE_LENGTH );
248 safe_year = safe_years[year_cycle];
250 assert(safe_year <= 2037 && safe_year >= 2010);
253 printf("year: %d, year_cycle: %d, safe_year: %d\n",
254 year, year_cycle, safe_year);
261 /* Simulate localtime_r() to the best of our ability */
262 struct tm * fake_localtime_r(const time_t *clock, struct tm *result) {
263 const struct tm *static_result = localtime(clock);
265 assert(result != NULL);
267 if( static_result == NULL ) {
268 memset(result, 0, sizeof(*result));
272 memcpy(result, static_result, sizeof(*result));
278 /* Simulate gmtime_r() to the best of our ability */
279 struct tm * fake_gmtime_r(const time_t *clock, struct tm *result) {
280 const struct tm *static_result = gmtime(clock);
282 assert(result != NULL);
284 if( static_result == NULL ) {
285 memset(result, 0, sizeof(*result));
289 memcpy(result, static_result, sizeof(*result));
295 struct tm *gmtime64_r (const Time64_T *in_time, struct tm *p)
297 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
301 Time64_T time = *in_time;
306 /* Use the system gmtime() if time_t is small enough */
307 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
308 time_t safe_time = *in_time;
309 GMTIME_R(&safe_time, p);
310 assert(_check_tm(p));
314 #ifdef HAS_TM_TM_GMTOFF
319 #ifdef HAS_TM_TM_ZONE
323 v_tm_sec = (int)(time % 60);
325 v_tm_min = (int)(time % 60);
327 v_tm_hour = (int)(time % 24);
331 WRAP (v_tm_sec, v_tm_min, 60);
332 WRAP (v_tm_min, v_tm_hour, 60);
333 WRAP (v_tm_hour, v_tm_tday, 24);
335 v_tm_wday = (int)((v_tm_tday + 4) % 7);
340 if (m >= CHEAT_DAYS) {
346 /* Gregorian cycles, this is huge optimization for distant times */
347 while (m >= (Time64_T) days_in_gregorian_cycle) {
348 m -= (Time64_T) days_in_gregorian_cycle;
349 year += years_in_gregorian_cycle;
353 leap = IS_LEAP (year);
354 while (m >= (Time64_T) length_of_year[leap]) {
355 m -= (Time64_T) length_of_year[leap];
357 leap = IS_LEAP (year);
362 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
363 m -= (Time64_T) days_in_month[leap][v_tm_mon];
369 /* Gregorian cycles */
370 while (m < (Time64_T) -days_in_gregorian_cycle) {
371 m += (Time64_T) days_in_gregorian_cycle;
372 year -= years_in_gregorian_cycle;
376 leap = IS_LEAP (year);
377 while (m < (Time64_T) -length_of_year[leap]) {
378 m += (Time64_T) length_of_year[leap];
380 leap = IS_LEAP (year);
385 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
386 m += (Time64_T) days_in_month[leap][v_tm_mon];
389 m += (Time64_T) days_in_month[leap][v_tm_mon];
393 if( p->tm_year != year ) {
400 p->tm_mday = (int) m + 1;
401 p->tm_yday = (int) julian_days_by_month[leap][v_tm_mon] + m;
402 p->tm_sec = v_tm_sec, p->tm_min = v_tm_min, p->tm_hour = v_tm_hour,
403 p->tm_mon = v_tm_mon, p->tm_wday = v_tm_wday;
405 assert(_check_tm(p));
411 struct tm *localtime64_r (const Time64_T *time, struct tm *local_tm)
418 assert(local_tm != NULL);
420 /* Use the system localtime() if time_t is small enough */
421 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
423 LOCALTIME_R(&safe_time, local_tm);
424 assert(_check_tm(local_tm));
428 if( gmtime64_r(time, &gm_tm) == NULL )
431 orig_year = gm_tm.tm_year;
433 if (gm_tm.tm_year > (2037 - 1900) ||
434 gm_tm.tm_year < (1902 - 1900)
437 gm_tm.tm_year = _safe_year(gm_tm.tm_year + 1900) - 1900;
440 safe_time = TIMEGM(&gm_tm);
441 if( LOCALTIME_R(&safe_time, local_tm) == NULL )
444 local_tm->tm_year = orig_year;
445 if( local_tm->tm_year != orig_year ) {
453 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
455 /* When localtime is Dec 31st previous year and
456 gmtime is Jan 1st next year.
458 if( month_diff == 11 ) {
462 /* When localtime is Jan 1st, next year and
463 gmtime is Dec 31st, previous year.
465 if( month_diff == -11 ) {
469 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
470 in a non-leap xx00. There is one point in the cycle
471 we can't account for which the safe xx00 year is a leap
472 year. So we need to correct for Dec 31st comming out as
473 the 366th day of the year.
475 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
478 assert(_check_tm(local_tm));