Commit | Line | Data |
a272e669 |
1 | /* |
2 | |
3 | Copyright (c) 2007-2008 Michael G Schwern |
4 | |
5 | This software originally derived from Paul Sheer's pivotal_gmtime_r.c. |
6 | |
7 | The MIT License: |
8 | |
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: |
15 | |
16 | The above copyright notice and this permission notice shall be included in |
17 | all copies or substantial portions of the Software. |
18 | |
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 |
25 | THE SOFTWARE. |
26 | |
27 | */ |
28 | |
29 | /* |
30 | |
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. |
35 | |
36 | localtime64_r() is a 64-bit equivalent of localtime_r(). |
37 | |
38 | gmtime64_r() is a 64-bit equivalent of gmtime_r(). |
39 | |
40 | */ |
41 | |
7643e68f |
42 | #include "time64.h" |
af9b2bf5 |
43 | |
a272e669 |
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}, |
47 | }; |
48 | |
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}, |
52 | }; |
53 | |
54 | static const int length_of_year[2] = { 365, 366 }; |
55 | |
56 | /* Number of days in a 400 year Gregorian cycle */ |
806a119a |
57 | static const Year years_in_gregorian_cycle = 400; |
a272e669 |
58 | static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1; |
59 | |
60 | /* 28 year calendar cycle between 2010 and 2037 */ |
806a119a |
61 | #define SOLAR_CYCLE_LENGTH 28 |
62 | static const int safe_years[SOLAR_CYCLE_LENGTH] = { |
a272e669 |
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 |
70 | }; |
71 | |
ea722b76 |
72 | static const int dow_year_start[SOLAR_CYCLE_LENGTH] = { |
003c3b95 |
73 | 5, 0, 1, 2, /* 0 2016 - 2019 */ |
74 | 3, 5, 6, 0, /* 4 */ |
75 | 1, 3, 4, 5, /* 8 */ |
76 | 6, 1, 2, 3, /* 12 */ |
77 | 4, 6, 0, 1, /* 16 */ |
78 | 2, 4, 5, 6, /* 20 2036, 2037, 2010, 2011 */ |
79 | 0, 2, 3, 4 /* 24 2012, 2013, 2014, 2015 */ |
a272e669 |
80 | }; |
81 | |
9af24521 |
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. |
85 | */ |
86 | /* Number of days since epoch on Jan 1st, 2008 GMT */ |
87 | #define CHEAT_DAYS (1199145600 / 24 / 60 / 60) |
88 | #define CHEAT_YEARS 108 |
a272e669 |
89 | |
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)) |
92 | |
b86b480f |
93 | #ifdef USE_SYSTEM_LOCALTIME |
94 | # define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \ |
7bda3dfc |
95 | (a) <= SYSTEM_LOCALTIME_MAX && \ |
96 | (a) >= SYSTEM_LOCALTIME_MIN \ |
97 | ) |
b86b480f |
98 | #else |
99 | # define SHOULD_USE_SYSTEM_LOCALTIME(a) (0) |
100 | #endif |
101 | |
102 | #ifdef USE_SYSTEM_GMTIME |
103 | # define SHOULD_USE_SYSTEM_GMTIME(a) ( \ |
7bda3dfc |
104 | (a) <= SYSTEM_GMTIME_MAX && \ |
105 | (a) >= SYSTEM_GMTIME_MIN \ |
106 | ) |
b86b480f |
107 | #else |
108 | # define SHOULD_USE_SYSTEM_GMTIME(a) (0) |
109 | #endif |
a64acb40 |
110 | |
461d5a49 |
111 | #ifdef TIME_64_DEBUG |
112 | # define TRACE(format, ...) (fprintf(stderr, format, __VA_ARGS__)) |
113 | # define TRACE_NO_VARS(format) (fprintf(stderr, format)) |
114 | #else |
115 | # define TRACE(format, ...) ((void)0) |
116 | # define TRACE_NO_VARS(format) ((void)0) |
117 | #endif |
a64acb40 |
118 | |
b86b480f |
119 | static int is_exception_century(Year year) |
a272e669 |
120 | { |
121 | int is_exception = ((year % 100 == 0) && !(year % 400 == 0)); |
461d5a49 |
122 | TRACE("# is_exception_century: %s\n", is_exception ? "yes" : "no"); |
a272e669 |
123 | |
124 | return(is_exception); |
125 | } |
126 | |
9af24521 |
127 | |
806a119a |
128 | Time64_T timegm64(struct TM *date) { |
b86b480f |
129 | int days = 0; |
130 | Time64_T seconds = 0; |
131 | Year year; |
a272e669 |
132 | |
9af24521 |
133 | if( date->tm_year > 70 ) { |
134 | year = 70; |
135 | while( year < date->tm_year ) { |
136 | days += length_of_year[IS_LEAP(year)]; |
137 | year++; |
a272e669 |
138 | } |
139 | } |
9af24521 |
140 | else if ( date->tm_year < 70 ) { |
141 | year = 69; |
142 | do { |
143 | days -= length_of_year[IS_LEAP(year)]; |
144 | year--; |
145 | } while( year >= date->tm_year ); |
146 | } |
147 | |
148 | days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon]; |
149 | days += date->tm_mday - 1; |
150 | |
ea722b76 |
151 | /* Avoid overflowing the days integer */ |
152 | seconds = days; |
153 | seconds = seconds * 60 * 60 * 24; |
154 | |
9af24521 |
155 | seconds += date->tm_hour * 60 * 60; |
156 | seconds += date->tm_min * 60; |
157 | seconds += date->tm_sec; |
158 | |
b86b480f |
159 | return(seconds); |
9af24521 |
160 | } |
161 | |
162 | |
806a119a |
163 | static int check_tm(struct TM *tm) |
9af24521 |
164 | { |
9af24521 |
165 | /* Don't forget leap seconds */ |
af9b2bf5 |
166 | assert(tm->tm_sec >= 0); |
9af24521 |
167 | assert(tm->tm_sec <= 61); |
168 | |
af9b2bf5 |
169 | assert(tm->tm_min >= 0); |
9af24521 |
170 | assert(tm->tm_min <= 59); |
171 | |
172 | assert(tm->tm_hour >= 0); |
173 | assert(tm->tm_hour <= 23); |
174 | |
175 | assert(tm->tm_mday >= 1); |
af9b2bf5 |
176 | assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]); |
9af24521 |
177 | |
178 | assert(tm->tm_mon >= 0); |
179 | assert(tm->tm_mon <= 11); |
180 | |
181 | assert(tm->tm_wday >= 0); |
182 | assert(tm->tm_wday <= 6); |
183 | |
184 | assert(tm->tm_yday >= 0); |
af9b2bf5 |
185 | assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]); |
9af24521 |
186 | |
187 | #ifdef HAS_TM_TM_GMTOFF |
188 | assert(tm->tm_gmtoff >= -24 * 60 * 60); |
189 | assert(tm->tm_gmtoff <= 24 * 60 * 60); |
190 | #endif |
af9b2bf5 |
191 | |
192 | return 1; |
a272e669 |
193 | } |
a64acb40 |
194 | |
a272e669 |
195 | |
196 | /* The exceptional centuries without leap years cause the cycle to |
197 | shift by 16 |
198 | */ |
806a119a |
199 | static Year cycle_offset(Year year) |
a272e669 |
200 | { |
750c447b |
201 | const Year start_year = 2000; |
202 | Year year_diff = year - start_year; |
203 | Year exceptions; |
003c3b95 |
204 | |
205 | if( year > start_year ) |
206 | year_diff--; |
207 | |
750c447b |
208 | exceptions = year_diff / 100; |
209 | exceptions -= year_diff / 400; |
a272e669 |
210 | |
461d5a49 |
211 | TRACE("# year: %lld, exceptions: %lld, year_diff: %lld\n", |
212 | year, exceptions, year_diff); |
a272e669 |
213 | |
214 | return exceptions * 16; |
215 | } |
216 | |
217 | /* For a given year after 2038, pick the latest possible matching |
218 | year in the 28 year calendar cycle. |
ea722b76 |
219 | |
220 | A matching year... |
221 | 1) Starts on the same day of the week. |
222 | 2) Has the same leap year status. |
223 | |
224 | This is so the calendars match up. |
225 | |
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. |
003c3b95 |
228 | |
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 |
232 | January 1st. |
a272e669 |
233 | */ |
806a119a |
234 | static int safe_year(Year year) |
a272e669 |
235 | { |
236 | int safe_year; |
806a119a |
237 | Year year_cycle = year + cycle_offset(year); |
a272e669 |
238 | |
239 | /* Change non-leap xx00 years to an equivalent */ |
806a119a |
240 | if( is_exception_century(year) ) |
a272e669 |
241 | year_cycle += 11; |
242 | |
003c3b95 |
243 | /* Also xx01 years, since the previous year will be wrong */ |
806a119a |
244 | if( is_exception_century(year - 1) ) |
003c3b95 |
245 | year_cycle += 17; |
246 | |
a272e669 |
247 | year_cycle %= SOLAR_CYCLE_LENGTH; |
ea722b76 |
248 | if( year_cycle < 0 ) |
249 | year_cycle = SOLAR_CYCLE_LENGTH + year_cycle; |
a272e669 |
250 | |
003c3b95 |
251 | assert( year_cycle >= 0 ); |
252 | assert( year_cycle < SOLAR_CYCLE_LENGTH ); |
a272e669 |
253 | safe_year = safe_years[year_cycle]; |
254 | |
255 | assert(safe_year <= 2037 && safe_year >= 2010); |
256 | |
461d5a49 |
257 | TRACE("# year: %lld, year_cycle: %lld, safe_year: %d\n", |
258 | year, year_cycle, safe_year); |
a272e669 |
259 | |
260 | return safe_year; |
261 | } |
262 | |
750c447b |
263 | |
806a119a |
264 | void copy_tm_to_TM(const struct tm *src, struct TM *dest) { |
265 | if( src == NULL ) { |
266 | memset(dest, 0, sizeof(*dest)); |
267 | } |
268 | else { |
269 | # ifdef USE_TM64 |
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; |
279 | |
280 | # ifdef HAS_TM_TM_GMTOFF |
281 | dest->tm_gmtoff = src->tm_gmtoff; |
282 | # endif |
283 | |
284 | # ifdef HAS_TM_TM_ZONE |
285 | dest->tm_zone = src->tm_zone; |
286 | # endif |
287 | |
288 | # else |
289 | /* They're the same type */ |
290 | memcpy(dest, src, sizeof(*dest)); |
291 | # endif |
292 | } |
293 | } |
294 | |
295 | |
296 | void copy_TM_to_tm(const struct TM *src, struct tm *dest) { |
297 | if( src == NULL ) { |
298 | memset(dest, 0, sizeof(*dest)); |
299 | } |
300 | else { |
301 | # ifdef USE_TM64 |
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; |
311 | |
312 | # ifdef HAS_TM_TM_GMTOFF |
313 | dest->tm_gmtoff = src->tm_gmtoff; |
314 | # endif |
315 | |
316 | # ifdef HAS_TM_TM_ZONE |
317 | dest->tm_zone = src->tm_zone; |
318 | # endif |
319 | |
320 | # else |
321 | /* They're the same type */ |
322 | memcpy(dest, src, sizeof(*dest)); |
323 | # endif |
324 | } |
325 | } |
326 | |
327 | |
948ea7a9 |
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); |
331 | |
332 | assert(result != NULL); |
333 | |
334 | if( static_result == NULL ) { |
335 | memset(result, 0, sizeof(*result)); |
336 | return NULL; |
337 | } |
338 | else { |
339 | memcpy(result, static_result, sizeof(*result)); |
340 | return result; |
341 | } |
342 | } |
343 | |
344 | |
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); |
348 | |
349 | assert(result != NULL); |
350 | |
351 | if( static_result == NULL ) { |
352 | memset(result, 0, sizeof(*result)); |
353 | return NULL; |
354 | } |
355 | else { |
356 | memcpy(result, static_result, sizeof(*result)); |
357 | return result; |
358 | } |
359 | } |
360 | |
361 | |
806a119a |
362 | struct TM *gmtime64_r (const Time64_T *in_time, struct TM *p) |
a272e669 |
363 | { |
364 | int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday; |
b86b480f |
365 | Time64_T v_tm_tday; |
a272e669 |
366 | int leap; |
b86b480f |
367 | Time64_T m; |
a272e669 |
368 | Time64_T time = *in_time; |
750c447b |
369 | Year year = 70; |
806a119a |
370 | int cycles = 0; |
a272e669 |
371 | |
948ea7a9 |
372 | assert(p != NULL); |
373 | |
a64acb40 |
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; |
806a119a |
377 | struct tm safe_date; |
378 | GMTIME_R(&safe_time, &safe_date); |
379 | |
380 | copy_tm_to_TM(&safe_date, p); |
381 | assert(check_tm(p)); |
382 | |
a64acb40 |
383 | return p; |
384 | } |
385 | |
9af24521 |
386 | #ifdef HAS_TM_TM_GMTOFF |
a272e669 |
387 | p->tm_gmtoff = 0; |
388 | #endif |
389 | p->tm_isdst = 0; |
390 | |
9af24521 |
391 | #ifdef HAS_TM_TM_ZONE |
a272e669 |
392 | p->tm_zone = "UTC"; |
393 | #endif |
394 | |
750c447b |
395 | v_tm_sec = (int)(time % 60); |
a272e669 |
396 | time /= 60; |
750c447b |
397 | v_tm_min = (int)(time % 60); |
a272e669 |
398 | time /= 60; |
750c447b |
399 | v_tm_hour = (int)(time % 24); |
a272e669 |
400 | time /= 24; |
401 | v_tm_tday = time; |
750c447b |
402 | |
a272e669 |
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); |
750c447b |
406 | |
407 | v_tm_wday = (int)((v_tm_tday + 4) % 7); |
408 | if (v_tm_wday < 0) |
a272e669 |
409 | v_tm_wday += 7; |
410 | m = v_tm_tday; |
a272e669 |
411 | |
9af24521 |
412 | if (m >= CHEAT_DAYS) { |
413 | year = CHEAT_YEARS; |
414 | m -= CHEAT_DAYS; |
415 | } |
416 | |
417 | if (m >= 0) { |
a272e669 |
418 | /* Gregorian cycles, this is huge optimization for distant times */ |
461d5a49 |
419 | cycles = (int)(m / (Time64_T) days_in_gregorian_cycle); |
806a119a |
420 | if( cycles ) { |
421 | m -= (cycles * (Time64_T) days_in_gregorian_cycle); |
422 | year += (cycles * years_in_gregorian_cycle); |
a272e669 |
423 | } |
424 | |
425 | /* Years */ |
426 | leap = IS_LEAP (year); |
427 | while (m >= (Time64_T) length_of_year[leap]) { |
428 | m -= (Time64_T) length_of_year[leap]; |
429 | year++; |
430 | leap = IS_LEAP (year); |
431 | } |
432 | |
433 | /* Months */ |
434 | v_tm_mon = 0; |
435 | while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) { |
436 | m -= (Time64_T) days_in_month[leap][v_tm_mon]; |
437 | v_tm_mon++; |
438 | } |
439 | } else { |
9af24521 |
440 | year--; |
a272e669 |
441 | |
442 | /* Gregorian cycles */ |
461d5a49 |
443 | cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1); |
806a119a |
444 | if( cycles ) { |
445 | m -= (cycles * (Time64_T) days_in_gregorian_cycle); |
446 | year += (cycles * years_in_gregorian_cycle); |
a272e669 |
447 | } |
448 | |
449 | /* Years */ |
450 | leap = IS_LEAP (year); |
451 | while (m < (Time64_T) -length_of_year[leap]) { |
452 | m += (Time64_T) length_of_year[leap]; |
453 | year--; |
454 | leap = IS_LEAP (year); |
455 | } |
456 | |
457 | /* Months */ |
458 | v_tm_mon = 11; |
459 | while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) { |
460 | m += (Time64_T) days_in_month[leap][v_tm_mon]; |
461 | v_tm_mon--; |
462 | } |
463 | m += (Time64_T) days_in_month[leap][v_tm_mon]; |
464 | } |
465 | |
466 | p->tm_year = year; |
467 | if( p->tm_year != year ) { |
9af24521 |
468 | #ifdef EOVERFLOW |
a272e669 |
469 | errno = EOVERFLOW; |
9af24521 |
470 | #endif |
a272e669 |
471 | return NULL; |
472 | } |
473 | |
b86b480f |
474 | /* At this point m is less than a year so casting to an int is safe */ |
a272e669 |
475 | p->tm_mday = (int) m + 1; |
b86b480f |
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; |
a272e669 |
482 | |
806a119a |
483 | assert(check_tm(p)); |
a272e669 |
484 | |
485 | return p; |
486 | } |
487 | |
488 | |
806a119a |
489 | struct TM *localtime64_r (const Time64_T *time, struct TM *local_tm) |
a272e669 |
490 | { |
491 | time_t safe_time; |
806a119a |
492 | struct tm safe_date; |
493 | struct TM gm_tm; |
750c447b |
494 | Year orig_year; |
a272e669 |
495 | int month_diff; |
496 | |
948ea7a9 |
497 | assert(local_tm != NULL); |
498 | |
a64acb40 |
499 | /* Use the system localtime() if time_t is small enough */ |
500 | if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) { |
501 | safe_time = *time; |
806a119a |
502 | |
461d5a49 |
503 | TRACE("Using system localtime for %lld\n", *time); |
504 | |
806a119a |
505 | LOCALTIME_R(&safe_time, &safe_date); |
506 | |
507 | copy_tm_to_TM(&safe_date, local_tm); |
508 | assert(check_tm(local_tm)); |
509 | |
a64acb40 |
510 | return local_tm; |
511 | } |
512 | |
461d5a49 |
513 | if( gmtime64_r(time, &gm_tm) == NULL ) { |
514 | TRACE("gmtime64_r returned null for %lld\n", *time); |
af832814 |
515 | return NULL; |
461d5a49 |
516 | } |
af832814 |
517 | |
a272e669 |
518 | orig_year = gm_tm.tm_year; |
519 | |
c07fe26c |
520 | if (gm_tm.tm_year > (2037 - 1900) || |
461d5a49 |
521 | gm_tm.tm_year < (1970 - 1900) |
c07fe26c |
522 | ) |
523 | { |
461d5a49 |
524 | TRACE("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year); |
b86b480f |
525 | gm_tm.tm_year = safe_year((Year)(gm_tm.tm_year + 1900)) - 1900; |
c07fe26c |
526 | } |
a272e669 |
527 | |
806a119a |
528 | safe_time = timegm64(&gm_tm); |
461d5a49 |
529 | if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) { |
530 | TRACE("localtime_r(%d) returned NULL\n", (int)safe_time); |
af832814 |
531 | return NULL; |
461d5a49 |
532 | } |
a272e669 |
533 | |
806a119a |
534 | copy_tm_to_TM(&safe_date, local_tm); |
535 | |
a272e669 |
536 | local_tm->tm_year = orig_year; |
af832814 |
537 | if( local_tm->tm_year != orig_year ) { |
461d5a49 |
538 | TRACE("tm_year overflow: tm_year %lld, orig_year %lld\n", |
539 | (Year)local_tm->tm_year, (Year)orig_year); |
540 | |
af832814 |
541 | #ifdef EOVERFLOW |
542 | errno = EOVERFLOW; |
543 | #endif |
544 | return NULL; |
545 | } |
546 | |
547 | |
a272e669 |
548 | month_diff = local_tm->tm_mon - gm_tm.tm_mon; |
549 | |
550 | /* When localtime is Dec 31st previous year and |
551 | gmtime is Jan 1st next year. |
552 | */ |
553 | if( month_diff == 11 ) { |
554 | local_tm->tm_year--; |
555 | } |
556 | |
557 | /* When localtime is Jan 1st, next year and |
558 | gmtime is Dec 31st, previous year. |
559 | */ |
560 | if( month_diff == -11 ) { |
561 | local_tm->tm_year++; |
562 | } |
563 | |
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. |
569 | */ |
570 | if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 ) |
571 | local_tm->tm_yday--; |
572 | |
806a119a |
573 | assert(check_tm(local_tm)); |
a272e669 |
574 | |
575 | return local_tm; |
576 | } |