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 * 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."
37 *
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:
47 *
48 * "Time! Time!"
49 *
50 * Bilbo was saved by pure luck. For that of course was the answer.
51 *
52 * [p.84 of _The Hobbit_: "Riddles in the Dark"]
53 *
54 */
55
56 /*
57
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.
62
63 Perl_localtime64_r() is a 64-bit equivalent of localtime_r().
64
65 Perl_gmtime64_r() is a 64-bit equivalent of gmtime_r().
66
67 */
68
69 #include "EXTERN.h"
70 #define PERL_IN_TIME64_C
71 #include "perl.h"
72 #include "time64.h"
73
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},
77 };
78
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},
82 };
83
84 static const short length_of_year[2] = { 365, 366 };
85
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;
89
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
100 };
101
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.
105 */
106 /* Number of days since epoch on Jan 1st, 2008 GMT */
107 #define CHEAT_DAYS (1199145600 / 24 / 60 / 60)
108 #define CHEAT_YEARS 108
109
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))
113
114 #ifdef USE_SYSTEM_LOCALTIME
115 # define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
116 (a) <= SYSTEM_LOCALTIME_MAX && \
117 (a) >= SYSTEM_LOCALTIME_MIN \
118 )
119 #else
120 # define SHOULD_USE_SYSTEM_LOCALTIME(a) (0)
121 #endif
122
123 #ifdef USE_SYSTEM_GMTIME
124 # define SHOULD_USE_SYSTEM_GMTIME(a) ( \
125 (a) <= SYSTEM_GMTIME_MAX && \
126 (a) >= SYSTEM_GMTIME_MIN \
127 )
128 #else
129 # define SHOULD_USE_SYSTEM_GMTIME(a) (0)
130 #endif
131
132 /* Multi varadic macros are a C99 thing, alas */
133 #ifdef TIME_64_DEBUG
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))
138 #else
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)
143 #endif
144
S_is_exception_century(Year year)145 static int S_is_exception_century(Year year)
146 {
147 const int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
148 TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");
149
150 return(is_exception);
151 }
152
153
S_timegm64(const struct TM * date)154 static Time64_T S_timegm64(const struct TM *date) {
155 int days = 0;
156 Time64_T seconds = 0;
157
158 if( date->tm_year > 70 ) {
159 Year year = 70;
160 while( year < date->tm_year ) {
161 days += length_of_year[IS_LEAP(year)];
162 year++;
163 }
164 }
165 else if ( date->tm_year < 70 ) {
166 Year year = 69;
167 do {
168 days -= length_of_year[IS_LEAP(year)];
169 year--;
170 } while( year >= date->tm_year );
171 }
172
173 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
174 days += date->tm_mday - 1;
175
176 /* Avoid overflowing the days integer */
177 seconds = days;
178 seconds = seconds * 60 * 60 * 24;
179
180 seconds += date->tm_hour * 60 * 60;
181 seconds += date->tm_min * 60;
182 seconds += date->tm_sec;
183
184 return(seconds);
185 }
186
187
188 #ifdef DEBUGGING
S_check_tm(const struct TM * tm)189 static int S_check_tm(const struct TM *tm)
190 {
191 /* Don't forget leap seconds */
192 assert(tm->tm_sec >= 0);
193 assert(tm->tm_sec <= 61);
194
195 assert(tm->tm_min >= 0);
196 assert(tm->tm_min <= 59);
197
198 assert(tm->tm_hour >= 0);
199 assert(tm->tm_hour <= 23);
200
201 assert(tm->tm_mday >= 1);
202 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
203
204 assert(tm->tm_mon >= 0);
205 assert(tm->tm_mon <= 11);
206
207 assert(tm->tm_wday >= 0);
208 assert(tm->tm_wday <= 6);
209
210 assert(tm->tm_yday >= 0);
211 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
212
213 #ifdef HAS_TM_TM_GMTOFF
214 assert(tm->tm_gmtoff >= -24 * 60 * 60);
215 assert(tm->tm_gmtoff <= 24 * 60 * 60);
216 #endif
217
218 return 1;
219 }
220 #endif
221
222
223 /* The exceptional centuries without leap years cause the cycle to
224 shift by 16
225 */
S_cycle_offset(Year year)226 static Year S_cycle_offset(Year year)
227 {
228 const Year start_year = 2000;
229 Year year_diff = year - start_year;
230 Year exceptions;
231
232 if( year > start_year )
233 year_diff--;
234
235 exceptions = year_diff / 100;
236 exceptions -= year_diff / 400;
237
238 TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
239 year, exceptions, year_diff);
240
241 return exceptions * 16;
242 }
243
244 /* For a given year after 2038, pick the latest possible matching
245 year in the 28 year calendar cycle.
246
247 A matching year...
248 1) Starts on the same day of the week.
249 2) Has the same leap year status.
250
251 This is so the calendars match up.
252
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.
255
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
259 January 1st.
260 */
S_safe_year(Year year)261 static int S_safe_year(Year year)
262 {
263 int safe_year;
264 Year year_cycle = year + S_cycle_offset(year);
265
266 /* Change non-leap xx00 years to an equivalent */
267 if( S_is_exception_century(year) )
268 year_cycle += 11;
269
270 /* Also xx01 years, since the previous year will be wrong */
271 if( S_is_exception_century(year - 1) )
272 year_cycle += 17;
273
274 year_cycle %= SOLAR_CYCLE_LENGTH;
275 if( year_cycle < 0 )
276 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
277
278 assert( year_cycle >= 0 );
279 assert( year_cycle < SOLAR_CYCLE_LENGTH );
280 safe_year = safe_years[year_cycle];
281
282 assert(safe_year <= 2037 && safe_year >= 2010);
283
284 TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
285 year, year_cycle, safe_year);
286
287 return safe_year;
288 }
289
290
S_copy_little_tm_to_big_TM(const struct tm * src,struct TM * dest)291 static void S_copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) {
292 assert(src);
293 assert(dest);
294 #ifdef USE_TM64
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;
304
305 # ifdef HAS_TM_TM_GMTOFF
306 dest->tm_gmtoff = src->tm_gmtoff;
307 # endif
308
309 # ifdef HAS_TM_TM_ZONE
310 dest->tm_zone = src->tm_zone;
311 # endif
312
313 #else
314 /* They're the same type */
315 memcpy(dest, src, sizeof(*dest));
316 #endif
317 }
318
Perl_gmtime64_r(const Time64_T * in_time,struct TM * p)319 struct TM *Perl_gmtime64_r (const Time64_T *in_time, struct TM *p)
320 {
321 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
322 Time64_T v_tm_tday;
323 int leap;
324 Time64_T m;
325 Time64_T time = *in_time;
326 Year year = 70;
327 dTHX;
328
329 assert(p != NULL);
330
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;
334 struct tm safe_date;
335 struct tm * result;
336
337 GMTIME_LOCK;
338
339 /* reentr.h will automatically replace this with a call to gmtime_r()
340 * when appropriate */
341 result = gmtime(&safe_time);
342
343 assert(result != NULL);
344
345 #if defined(HAS_GMTIME_R) && defined(USE_REENTRANT_API)
346
347 PERL_UNUSED_VAR(safe_date);
348 #else
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));
354 result = &safe_date;
355 #endif
356 GMTIME_UNLOCK;
357
358 S_copy_little_tm_to_big_TM(result, p);
359 assert(S_check_tm(p));
360
361 return p;
362 }
363
364 #ifdef HAS_TM_TM_GMTOFF
365 p->tm_gmtoff = 0;
366 #endif
367 p->tm_isdst = 0;
368
369 #ifdef HAS_TM_TM_ZONE
370 p->tm_zone = "UTC";
371 #endif
372
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);
379 v_tm_tday = time;
380
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);
384
385 v_tm_wday = (int)Perl_fmod((v_tm_tday + 4.0), 7.0);
386 if (v_tm_wday < 0)
387 v_tm_wday += 7;
388 m = v_tm_tday;
389
390 if (m >= CHEAT_DAYS) {
391 year = CHEAT_YEARS;
392 m -= CHEAT_DAYS;
393 }
394
395 if (m >= 0) {
396 /* Gregorian cycles, this is huge optimization for distant times */
397 const int cycles = (int)Perl_floor(m / (Time64_T) days_in_gregorian_cycle);
398 if( cycles ) {
399 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
400 year += (cycles * years_in_gregorian_cycle);
401 }
402
403 /* Years */
404 leap = IS_LEAP (year);
405 while (m >= (Time64_T) length_of_year[leap]) {
406 m -= (Time64_T) length_of_year[leap];
407 year++;
408 leap = IS_LEAP (year);
409 }
410
411 /* Months */
412 v_tm_mon = 0;
413 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
414 m -= (Time64_T) days_in_month[leap][v_tm_mon];
415 v_tm_mon++;
416 }
417 } else {
418 int cycles;
419
420 year--;
421
422 /* Gregorian cycles */
423 cycles = (int)Perl_ceil((m / (Time64_T) days_in_gregorian_cycle) + 1);
424 if( cycles ) {
425 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
426 year += (cycles * years_in_gregorian_cycle);
427 }
428
429 /* Years */
430 leap = IS_LEAP (year);
431 while (m < (Time64_T) -length_of_year[leap]) {
432 m += (Time64_T) length_of_year[leap];
433 year--;
434 leap = IS_LEAP (year);
435 }
436
437 /* Months */
438 v_tm_mon = 11;
439 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
440 m += (Time64_T) days_in_month[leap][v_tm_mon];
441 v_tm_mon--;
442 }
443 m += (Time64_T) days_in_month[leap][v_tm_mon];
444 }
445
446 p->tm_year = year;
447 if( p->tm_year != year ) {
448 #ifdef EOVERFLOW
449 errno = EOVERFLOW;
450 #endif
451 return NULL;
452 }
453
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;
462
463 assert(S_check_tm(p));
464
465 return p;
466 }
467
468
Perl_localtime64_r(const Time64_T * time,struct TM * local_tm)469 struct TM *Perl_localtime64_r (const Time64_T *time, struct TM *local_tm)
470 {
471 time_t safe_time;
472 struct tm safe_date;
473 const struct tm * result;
474 struct TM gm_tm;
475 Year orig_year = 0; /* initialise to avoid spurious compiler warning */
476 int month_diff;
477 const bool use_system = SHOULD_USE_SYSTEM_LOCALTIME(*time);
478 dTHX;
479
480 assert(local_tm != NULL);
481
482 /* Use the system localtime() if time_t is small enough */
483 if (use_system) {
484 safe_time = (time_t)*time;
485
486 TIME64_TRACE1("Using system localtime for %lld\n", *time);
487 }
488 else {
489 if (Perl_gmtime64_r(time, &gm_tm) == NULL) {
490 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time);
491 return NULL;
492 }
493
494 orig_year = gm_tm.tm_year;
495
496 if (gm_tm.tm_year > (2037 - 1900) ||
497 gm_tm.tm_year < (1970 - 1900)
498 )
499 {
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;
503 }
504
505 safe_time = (time_t)S_timegm64(&gm_tm);
506 }
507
508 LOCALTIME_LOCK;
509
510 /* reentr.h will automatically replace this with a call to localtime_r()
511 * when appropriate */
512 result = localtime(&safe_time);
513
514 if(UNLIKELY(result == NULL)) {
515 LOCALTIME_UNLOCK;
516 TIME64_TRACE1("localtime(%d) returned NULL\n", (int)safe_time);
517 return NULL;
518 }
519
520 #if ! defined(USE_REENTRANT_API) || defined(PERL_REENTR_USING_LOCALTIME_R)
521
522 PERL_UNUSED_VAR(safe_date);
523
524 #else
525
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
530 * result. */
531 memcpy(&safe_date, result, sizeof(safe_date));
532 result = &safe_date;
533
534 #endif
535
536 LOCALTIME_UNLOCK;
537
538 S_copy_little_tm_to_big_TM(result, local_tm);
539
540 if (! use_system) {
541
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);
546
547 #ifdef EOVERFLOW
548 errno = EOVERFLOW;
549 #endif
550 return NULL;
551 }
552
553 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
554
555 /* When localtime is Dec 31st previous year and
556 gmtime is Jan 1st next year.
557 */
558 if( month_diff == 11 ) {
559 local_tm->tm_year--;
560 }
561
562 /* When localtime is Jan 1st, next year and
563 gmtime is Dec 31st, previous year.
564 */
565 if( month_diff == -11 ) {
566 local_tm->tm_year++;
567 }
568
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.
574 */
575 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
576 local_tm->tm_yday--;
577
578 }
579
580 assert(S_check_tm(local_tm));
581
582 return local_tm;
583 }
584