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Silence a warning in time64.c. Need to downgrade a const char *
[perl5.git] / time64.c
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a272e669
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1/*
2
3Copyright (c) 2007-2008 Michael G Schwern
4
5This software originally derived from Paul Sheer's pivotal_gmtime_r.c.
6
7The MIT License:
8
9Permission is hereby granted, free of charge, to any person obtaining a copy
10of this software and associated documentation files (the "Software"), to deal
11in the Software without restriction, including without limitation the rights
12to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
13copies of the Software, and to permit persons to whom the Software is
14furnished to do so, subject to the following conditions:
15
16The above copyright notice and this permission notice shall be included in
17all copies or substantial portions of the Software.
18
19THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
22AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
23LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
24OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
25THE SOFTWARE.
26
27*/
28
29/*
30
31Programmers who have available to them 64-bit time values as a 'long
32long' type can use localtime64_r() and gmtime64_r() which correctly
33converts the time even on 32-bit systems. Whether you have 64-bit time
34values will depend on the operating system.
35
7430375d 36S_localtime64_r() is a 64-bit equivalent of localtime_r().
a272e669 37
7430375d 38S_gmtime64_r() is a 64-bit equivalent of gmtime_r().
a272e669
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39
40*/
41
7643e68f 42#include "time64.h"
af9b2bf5 43
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44static 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
49static 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
54static const int length_of_year[2] = { 365, 366 };
55
56/* Number of days in a 400 year Gregorian cycle */
806a119a 57static const Year years_in_gregorian_cycle = 400;
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58static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1;
59
60/* 28 year calendar cycle between 2010 and 2037 */
806a119a
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61#define SOLAR_CYCLE_LENGTH 28
62static const int safe_years[SOLAR_CYCLE_LENGTH] = {
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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 72static const int dow_year_start[SOLAR_CYCLE_LENGTH] = {
003c3b95
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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 */
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80};
81
9af24521
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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
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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
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93#ifdef USE_SYSTEM_LOCALTIME
94# define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
7bda3dfc
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95 (a) <= SYSTEM_LOCALTIME_MAX && \
96 (a) >= SYSTEM_LOCALTIME_MIN \
97)
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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) ( \
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104 (a) <= SYSTEM_GMTIME_MAX && \
105 (a) >= SYSTEM_GMTIME_MIN \
106)
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107#else
108# define SHOULD_USE_SYSTEM_GMTIME(a) (0)
109#endif
a64acb40 110
d4fb0a1f 111/* Multi varadic macros are a C99 thing, alas */
461d5a49 112#ifdef TIME_64_DEBUG
7430375d
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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))
461d5a49 117#else
7430375d
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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)
461d5a49 122#endif
a64acb40 123
7430375d 124static int S_is_exception_century(Year year)
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125{
126 int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
7430375d 127 TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");
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128
129 return(is_exception);
130}
131
9af24521 132
7430375d 133static Time64_T S_timegm64(struct TM *date) {
b86b480f
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134 int days = 0;
135 Time64_T seconds = 0;
136 Year year;
a272e669 137
9af24521
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138 if( date->tm_year > 70 ) {
139 year = 70;
140 while( year < date->tm_year ) {
141 days += length_of_year[IS_LEAP(year)];
142 year++;
a272e669
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143 }
144 }
9af24521
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145 else if ( date->tm_year < 70 ) {
146 year = 69;
147 do {
148 days -= length_of_year[IS_LEAP(year)];
149 year--;
150 } while( year >= date->tm_year );
151 }
152
153 days += julian_days_by_month[IS_LEAP(date->tm_year)][date->tm_mon];
154 days += date->tm_mday - 1;
155
ea722b76
MS
156 /* Avoid overflowing the days integer */
157 seconds = days;
158 seconds = seconds * 60 * 60 * 24;
159
9af24521
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160 seconds += date->tm_hour * 60 * 60;
161 seconds += date->tm_min * 60;
162 seconds += date->tm_sec;
163
b86b480f 164 return(seconds);
9af24521
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165}
166
167
554fcfb9 168#ifdef DEBUGGING
7430375d 169static int S_check_tm(struct TM *tm)
9af24521 170{
9af24521 171 /* Don't forget leap seconds */
af9b2bf5 172 assert(tm->tm_sec >= 0);
9af24521
MS
173 assert(tm->tm_sec <= 61);
174
af9b2bf5 175 assert(tm->tm_min >= 0);
9af24521
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176 assert(tm->tm_min <= 59);
177
178 assert(tm->tm_hour >= 0);
179 assert(tm->tm_hour <= 23);
180
181 assert(tm->tm_mday >= 1);
af9b2bf5 182 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);
9af24521
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183
184 assert(tm->tm_mon >= 0);
185 assert(tm->tm_mon <= 11);
186
187 assert(tm->tm_wday >= 0);
188 assert(tm->tm_wday <= 6);
189
190 assert(tm->tm_yday >= 0);
af9b2bf5 191 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);
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192
193#ifdef HAS_TM_TM_GMTOFF
194 assert(tm->tm_gmtoff >= -24 * 60 * 60);
195 assert(tm->tm_gmtoff <= 24 * 60 * 60);
196#endif
af9b2bf5
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197
198 return 1;
a272e669 199}
554fcfb9 200#endif
a64acb40 201
a272e669
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202
203/* The exceptional centuries without leap years cause the cycle to
204 shift by 16
205*/
7430375d 206static Year S_cycle_offset(Year year)
a272e669 207{
750c447b
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208 const Year start_year = 2000;
209 Year year_diff = year - start_year;
210 Year exceptions;
003c3b95
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211
212 if( year > start_year )
213 year_diff--;
214
750c447b
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215 exceptions = year_diff / 100;
216 exceptions -= year_diff / 400;
a272e669 217
7430375d 218 TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
461d5a49 219 year, exceptions, year_diff);
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220
221 return exceptions * 16;
222}
223
224/* For a given year after 2038, pick the latest possible matching
225 year in the 28 year calendar cycle.
ea722b76
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226
227 A matching year...
228 1) Starts on the same day of the week.
229 2) Has the same leap year status.
230
231 This is so the calendars match up.
232
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.
003c3b95
MS
235
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
239 January 1st.
a272e669 240*/
7430375d 241static int S_safe_year(Year year)
a272e669
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242{
243 int safe_year;
7430375d 244 Year year_cycle = year + S_cycle_offset(year);
a272e669
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245
246 /* Change non-leap xx00 years to an equivalent */
7430375d 247 if( S_is_exception_century(year) )
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248 year_cycle += 11;
249
003c3b95 250 /* Also xx01 years, since the previous year will be wrong */
7430375d 251 if( S_is_exception_century(year - 1) )
003c3b95
MS
252 year_cycle += 17;
253
a272e669 254 year_cycle %= SOLAR_CYCLE_LENGTH;
ea722b76
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255 if( year_cycle < 0 )
256 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;
a272e669 257
003c3b95
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258 assert( year_cycle >= 0 );
259 assert( year_cycle < SOLAR_CYCLE_LENGTH );
a272e669
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260 safe_year = safe_years[year_cycle];
261
262 assert(safe_year <= 2037 && safe_year >= 2010);
263
7430375d 264 TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
461d5a49 265 year, year_cycle, safe_year);
a272e669
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266
267 return safe_year;
268}
269
750c447b 270
7430375d 271static void S_copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) {
806a119a
MS
272 if( src == NULL ) {
273 memset(dest, 0, sizeof(*dest));
274 }
275 else {
276# ifdef USE_TM64
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;
806a119a
MS
283 dest->tm_wday = src->tm_wday;
284 dest->tm_yday = src->tm_yday;
285 dest->tm_isdst = src->tm_isdst;
286
287# ifdef HAS_TM_TM_GMTOFF
288 dest->tm_gmtoff = src->tm_gmtoff;
289# endif
290
291# ifdef HAS_TM_TM_ZONE
292 dest->tm_zone = src->tm_zone;
293# endif
294
295# else
296 /* They're the same type */
297 memcpy(dest, src, sizeof(*dest));
298# endif
299 }
300}
301
302
7430375d 303#ifndef HAS_LOCALTIME_R
948ea7a9 304/* Simulate localtime_r() to the best of our ability */
7430375d 305static struct tm * S_localtime_r(const time_t *clock, struct tm *result) {
478780ab 306 dTHX; /* in case the following is defined as Perl_my_localtime(aTHX_ ...) */
948ea7a9
MS
307 const struct tm *static_result = localtime(clock);
308
309 assert(result != NULL);
310
311 if( static_result == NULL ) {
312 memset(result, 0, sizeof(*result));
313 return NULL;
314 }
315 else {
316 memcpy(result, static_result, sizeof(*result));
317 return result;
318 }
319}
7430375d 320#endif
948ea7a9 321
7430375d 322#ifndef HAS_GMTIME_R
948ea7a9 323/* Simulate gmtime_r() to the best of our ability */
7430375d 324static struct tm * S_gmtime_r(const time_t *clock, struct tm *result) {
478780ab 325 dTHX; /* in case the following is defined as Perl_my_gmtime(aTHX_ ...) */
948ea7a9
MS
326 const struct tm *static_result = gmtime(clock);
327
328 assert(result != NULL);
329
330 if( static_result == NULL ) {
331 memset(result, 0, sizeof(*result));
332 return NULL;
333 }
334 else {
335 memcpy(result, static_result, sizeof(*result));
336 return result;
337 }
338}
7430375d 339#endif
948ea7a9 340
7430375d 341static struct TM *S_gmtime64_r (const Time64_T *in_time, struct TM *p)
a272e669
MS
342{
343 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
b86b480f 344 Time64_T v_tm_tday;
a272e669 345 int leap;
b86b480f 346 Time64_T m;
a272e669 347 Time64_T time = *in_time;
750c447b 348 Year year = 70;
806a119a 349 int cycles = 0;
a272e669 350
948ea7a9
MS
351 assert(p != NULL);
352
a64acb40
MS
353 /* Use the system gmtime() if time_t is small enough */
354 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
cd1759d8 355 time_t safe_time = (time_t)*in_time;
806a119a
MS
356 struct tm safe_date;
357 GMTIME_R(&safe_time, &safe_date);
358
7430375d
CB
359 S_copy_little_tm_to_big_TM(&safe_date, p);
360 assert(S_check_tm(p));
806a119a 361
a64acb40
MS
362 return p;
363 }
364
9af24521 365#ifdef HAS_TM_TM_GMTOFF
a272e669
MS
366 p->tm_gmtoff = 0;
367#endif
368 p->tm_isdst = 0;
369
9af24521 370#ifdef HAS_TM_TM_ZONE
1cefca6b 371 p->tm_zone = (char *)"UTC";
a272e669
MS
372#endif
373
d95a2ea5
CB
374 v_tm_sec = (int)fmod(time, 60.0);
375 time = time >= 0 ? floor(time / 60.0) : ceil(time / 60.0);
376 v_tm_min = (int)fmod(time, 60.0);
377 time = time >= 0 ? floor(time / 60.0) : ceil(time / 60.0);
378 v_tm_hour = (int)fmod(time, 24.0);
379 time = time >= 0 ? floor(time / 24.0) : ceil(time / 24.0);
455f2c6c 380 v_tm_tday = time;
750c447b 381
a272e669
MS
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);
750c447b 385
d95a2ea5 386 v_tm_wday = (int)fmod((v_tm_tday + 4.0), 7.0);
750c447b 387 if (v_tm_wday < 0)
a272e669
MS
388 v_tm_wday += 7;
389 m = v_tm_tday;
a272e669 390
9af24521
MS
391 if (m >= CHEAT_DAYS) {
392 year = CHEAT_YEARS;
393 m -= CHEAT_DAYS;
394 }
395
396 if (m >= 0) {
a272e669 397 /* Gregorian cycles, this is huge optimization for distant times */
d95a2ea5 398 cycles = (int)floor(m / (Time64_T) days_in_gregorian_cycle);
806a119a
MS
399 if( cycles ) {
400 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
401 year += (cycles * years_in_gregorian_cycle);
a272e669
MS
402 }
403
404 /* Years */
405 leap = IS_LEAP (year);
406 while (m >= (Time64_T) length_of_year[leap]) {
407 m -= (Time64_T) length_of_year[leap];
408 year++;
409 leap = IS_LEAP (year);
410 }
411
412 /* Months */
413 v_tm_mon = 0;
414 while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
415 m -= (Time64_T) days_in_month[leap][v_tm_mon];
416 v_tm_mon++;
417 }
418 } else {
9af24521 419 year--;
a272e669
MS
420
421 /* Gregorian cycles */
d95a2ea5 422 cycles = (int)ceil((m / (Time64_T) days_in_gregorian_cycle) + 1);
806a119a
MS
423 if( cycles ) {
424 m -= (cycles * (Time64_T) days_in_gregorian_cycle);
425 year += (cycles * years_in_gregorian_cycle);
a272e669
MS
426 }
427
428 /* Years */
429 leap = IS_LEAP (year);
430 while (m < (Time64_T) -length_of_year[leap]) {
431 m += (Time64_T) length_of_year[leap];
432 year--;
433 leap = IS_LEAP (year);
434 }
435
436 /* Months */
437 v_tm_mon = 11;
438 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
439 m += (Time64_T) days_in_month[leap][v_tm_mon];
440 v_tm_mon--;
441 }
442 m += (Time64_T) days_in_month[leap][v_tm_mon];
443 }
444
445 p->tm_year = year;
446 if( p->tm_year != year ) {
9af24521 447#ifdef EOVERFLOW
a272e669 448 errno = EOVERFLOW;
9af24521 449#endif
a272e669
MS
450 return NULL;
451 }
452
b86b480f 453 /* At this point m is less than a year so casting to an int is safe */
a272e669 454 p->tm_mday = (int) m + 1;
b86b480f
MS
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;
a272e669 461
7430375d 462 assert(S_check_tm(p));
a272e669
MS
463
464 return p;
465}
466
467
673062a9 468static struct TM *S_localtime64_r (const Time64_T *time, struct TM *local_tm)
a272e669
MS
469{
470 time_t safe_time;
806a119a
MS
471 struct tm safe_date;
472 struct TM gm_tm;
750c447b 473 Year orig_year;
a272e669
MS
474 int month_diff;
475
948ea7a9
MS
476 assert(local_tm != NULL);
477
a64acb40
MS
478 /* Use the system localtime() if time_t is small enough */
479 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) {
cd1759d8 480 safe_time = (time_t)*time;
806a119a 481
7430375d 482 TIME64_TRACE1("Using system localtime for %lld\n", *time);
461d5a49 483
806a119a
MS
484 LOCALTIME_R(&safe_time, &safe_date);
485
7430375d
CB
486 S_copy_little_tm_to_big_TM(&safe_date, local_tm);
487 assert(S_check_tm(local_tm));
806a119a 488
a64acb40
MS
489 return local_tm;
490 }
491
7430375d
CB
492 if( S_gmtime64_r(time, &gm_tm) == NULL ) {
493 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time);
af832814 494 return NULL;
461d5a49 495 }
af832814 496
a272e669
MS
497 orig_year = gm_tm.tm_year;
498
c07fe26c 499 if (gm_tm.tm_year > (2037 - 1900) ||
461d5a49 500 gm_tm.tm_year < (1970 - 1900)
c07fe26c
MS
501 )
502 {
7430375d
CB
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;
c07fe26c 505 }
a272e669 506
7430375d 507 safe_time = (time_t)S_timegm64(&gm_tm);
461d5a49 508 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
7430375d 509 TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time);
af832814 510 return NULL;
461d5a49 511 }
a272e669 512
7430375d 513 S_copy_little_tm_to_big_TM(&safe_date, local_tm);
806a119a 514
a272e669 515 local_tm->tm_year = orig_year;
af832814 516 if( local_tm->tm_year != orig_year ) {
7430375d 517 TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
461d5a49
MS
518 (Year)local_tm->tm_year, (Year)orig_year);
519
af832814
MS
520#ifdef EOVERFLOW
521 errno = EOVERFLOW;
522#endif
523 return NULL;
524 }
525
526
a272e669
MS
527 month_diff = local_tm->tm_mon - gm_tm.tm_mon;
528
529 /* When localtime is Dec 31st previous year and
530 gmtime is Jan 1st next year.
531 */
532 if( month_diff == 11 ) {
533 local_tm->tm_year--;
534 }
535
536 /* When localtime is Jan 1st, next year and
537 gmtime is Dec 31st, previous year.
538 */
539 if( month_diff == -11 ) {
540 local_tm->tm_year++;
541 }
542
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.
548 */
549 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
550 local_tm->tm_yday--;
551
7430375d 552 assert(S_check_tm(local_tm));
a272e669
MS
553
554 return local_tm;
555}