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 S_localtime64_r() is a 64-bit equivalent of localtime_r(). 37 38 S_gmtime64_r() is a 64-bit equivalent of gmtime_r(). 39 40 */ 41 42 #include "time64.h" 43 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 */ 57 static const Year years_in_gregorian_cycle = 400; 58 static const int days_in_gregorian_cycle = (365 * 400) + 100 - 4 + 1; 59 60 /* 28 year calendar cycle between 2010 and 2037 */ 61 #define SOLAR_CYCLE_LENGTH 28 62 static const int safe_years[SOLAR_CYCLE_LENGTH] = { 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 72 static const int dow_year_start[SOLAR_CYCLE_LENGTH] = { 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 */ 80 }; 81 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 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 93 #ifdef USE_SYSTEM_LOCALTIME 94 # define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \ 95 (a) <= SYSTEM_LOCALTIME_MAX && \ 96 (a) >= SYSTEM_LOCALTIME_MIN \ 97 ) 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) ( \ 104 (a) <= SYSTEM_GMTIME_MAX && \ 105 (a) >= SYSTEM_GMTIME_MIN \ 106 ) 107 #else 108 # define SHOULD_USE_SYSTEM_GMTIME(a) (0) 109 #endif 110 111 /* Multi varadic macros are a C99 thing, alas */ 112 #ifdef TIME_64_DEBUG 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)) 117 #else 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) 122 #endif 123 124 static int S_is_exception_century(Year year) 125 { 126 int is_exception = ((year % 100 == 0) && !(year % 400 == 0)); 127 TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no"); 128 129 return(is_exception); 130 } 131 132 133 static Time64_T S_timegm64(struct TM *date) { 134 int days = 0; 135 Time64_T seconds = 0; 136 Year year; 137 138 if( date->tm_year > 70 ) { 139 year = 70; 140 while( year < date->tm_year ) { 141 days += length_of_year[IS_LEAP(year)]; 142 year++; 143 } 144 } 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; 155 156 /* Avoid overflowing the days integer */ 157 seconds = days; 158 seconds = seconds * 60 * 60 * 24; 159 160 seconds += date->tm_hour * 60 * 60; 161 seconds += date->tm_min * 60; 162 seconds += date->tm_sec; 163 164 return(seconds); 165 } 166 167 168 #ifdef DEBUGGING 169 static int S_check_tm(struct TM *tm) 170 { 171 /* Don't forget leap seconds */ 172 assert(tm->tm_sec >= 0); 173 assert(tm->tm_sec <= 61); 174 175 assert(tm->tm_min >= 0); 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); 182 assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]); 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); 191 assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]); 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 197 198 return 1; 199 } 200 #endif 201 202 203 /* The exceptional centuries without leap years cause the cycle to 204 shift by 16 205 */ 206 static Year S_cycle_offset(Year year) 207 { 208 const Year start_year = 2000; 209 Year year_diff = year - start_year; 210 Year exceptions; 211 212 if( year > start_year ) 213 year_diff--; 214 215 exceptions = year_diff / 100; 216 exceptions -= year_diff / 400; 217 218 TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n", 219 year, exceptions, year_diff); 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. 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. 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. 240 */ 241 static int S_safe_year(Year year) 242 { 243 int safe_year; 244 Year year_cycle = year + S_cycle_offset(year); 245 246 /* Change non-leap xx00 years to an equivalent */ 247 if( S_is_exception_century(year) ) 248 year_cycle += 11; 249 250 /* Also xx01 years, since the previous year will be wrong */ 251 if( S_is_exception_century(year - 1) ) 252 year_cycle += 17; 253 254 year_cycle %= SOLAR_CYCLE_LENGTH; 255 if( year_cycle < 0 ) 256 year_cycle = SOLAR_CYCLE_LENGTH + year_cycle; 257 258 assert( year_cycle >= 0 ); 259 assert( year_cycle < SOLAR_CYCLE_LENGTH ); 260 safe_year = safe_years[year_cycle]; 261 262 assert(safe_year <= 2037 && safe_year >= 2010); 263 264 TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n", 265 year, year_cycle, safe_year); 266 267 return safe_year; 268 } 269 270 271 static void S_copy_little_tm_to_big_TM(const struct tm *src, struct TM *dest) { 272 assert(src); 273 assert(dest); 274 #ifdef USE_TM64 275 dest->tm_sec = src->tm_sec; 276 dest->tm_min = src->tm_min; 277 dest->tm_hour = src->tm_hour; 278 dest->tm_mday = src->tm_mday; 279 dest->tm_mon = src->tm_mon; 280 dest->tm_year = (Year)src->tm_year; 281 dest->tm_wday = src->tm_wday; 282 dest->tm_yday = src->tm_yday; 283 dest->tm_isdst = src->tm_isdst; 284 285 # ifdef HAS_TM_TM_GMTOFF 286 dest->tm_gmtoff = src->tm_gmtoff; 287 # endif 288 289 # ifdef HAS_TM_TM_ZONE 290 dest->tm_zone = src->tm_zone; 291 # endif 292 293 #else 294 /* They're the same type */ 295 memcpy(dest, src, sizeof(*dest)); 296 #endif 297 } 298 299 300 #ifndef HAS_LOCALTIME_R 301 /* Simulate localtime_r() to the best of our ability */ 302 static struct tm * S_localtime_r(const time_t *clock, struct tm *result) { 303 #ifdef VMS 304 dTHX; /* in case the following is defined as Perl_my_localtime(aTHX_ ...) */ 305 #endif 306 const struct tm *static_result = localtime(clock); 307 308 assert(result != NULL); 309 310 if( static_result == NULL ) { 311 memset(result, 0, sizeof(*result)); 312 return NULL; 313 } 314 else { 315 memcpy(result, static_result, sizeof(*result)); 316 return result; 317 } 318 } 319 #endif 320 321 #ifndef HAS_GMTIME_R 322 /* Simulate gmtime_r() to the best of our ability */ 323 static struct tm * S_gmtime_r(const time_t *clock, struct tm *result) { 324 dTHX; /* in case the following is defined as Perl_my_gmtime(aTHX_ ...) */ 325 const struct tm *static_result = gmtime(clock); 326 327 assert(result != NULL); 328 329 if( static_result == NULL ) { 330 memset(result, 0, sizeof(*result)); 331 return NULL; 332 } 333 else { 334 memcpy(result, static_result, sizeof(*result)); 335 return result; 336 } 337 } 338 #endif 339 340 static struct TM *S_gmtime64_r (const Time64_T *in_time, struct TM *p) 341 { 342 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday; 343 Time64_T v_tm_tday; 344 int leap; 345 Time64_T m; 346 Time64_T time = *in_time; 347 Year year = 70; 348 int cycles = 0; 349 350 assert(p != NULL); 351 352 /* Use the system gmtime() if time_t is small enough */ 353 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) { 354 time_t safe_time = (time_t)*in_time; 355 struct tm safe_date; 356 GMTIME_R(&safe_time, &safe_date); 357 358 S_copy_little_tm_to_big_TM(&safe_date, 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 = (char *)"UTC"; 371 #endif 372 373 v_tm_sec = (int)fmod(time, 60.0); 374 time = time >= 0 ? floor(time / 60.0) : ceil(time / 60.0); 375 v_tm_min = (int)fmod(time, 60.0); 376 time = time >= 0 ? floor(time / 60.0) : ceil(time / 60.0); 377 v_tm_hour = (int)fmod(time, 24.0); 378 time = time >= 0 ? floor(time / 24.0) : 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)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 cycles = (int)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 year--; 419 420 /* Gregorian cycles */ 421 cycles = (int)ceil((m / (Time64_T) days_in_gregorian_cycle) + 1); 422 if( cycles ) { 423 m -= (cycles * (Time64_T) days_in_gregorian_cycle); 424 year += (cycles * years_in_gregorian_cycle); 425 } 426 427 /* Years */ 428 leap = IS_LEAP (year); 429 while (m < (Time64_T) -length_of_year[leap]) { 430 m += (Time64_T) length_of_year[leap]; 431 year--; 432 leap = IS_LEAP (year); 433 } 434 435 /* Months */ 436 v_tm_mon = 11; 437 while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) { 438 m += (Time64_T) days_in_month[leap][v_tm_mon]; 439 v_tm_mon--; 440 } 441 m += (Time64_T) days_in_month[leap][v_tm_mon]; 442 } 443 444 p->tm_year = year; 445 if( p->tm_year != year ) { 446 #ifdef EOVERFLOW 447 errno = EOVERFLOW; 448 #endif 449 return NULL; 450 } 451 452 /* At this point m is less than a year so casting to an int is safe */ 453 p->tm_mday = (int) m + 1; 454 p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m; 455 p->tm_sec = v_tm_sec; 456 p->tm_min = v_tm_min; 457 p->tm_hour = v_tm_hour; 458 p->tm_mon = v_tm_mon; 459 p->tm_wday = v_tm_wday; 460 461 assert(S_check_tm(p)); 462 463 return p; 464 } 465 466 467 static struct TM *S_localtime64_r (const Time64_T *time, struct TM *local_tm) 468 { 469 time_t safe_time; 470 struct tm safe_date; 471 struct TM gm_tm; 472 Year orig_year; 473 int month_diff; 474 475 assert(local_tm != NULL); 476 477 /* Use the system localtime() if time_t is small enough */ 478 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) { 479 safe_time = (time_t)*time; 480 481 TIME64_TRACE1("Using system localtime for %lld\n", *time); 482 483 LOCALTIME_R(&safe_time, &safe_date); 484 485 S_copy_little_tm_to_big_TM(&safe_date, local_tm); 486 assert(S_check_tm(local_tm)); 487 488 return local_tm; 489 } 490 491 if( S_gmtime64_r(time, &gm_tm) == NULL ) { 492 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time); 493 return NULL; 494 } 495 496 orig_year = gm_tm.tm_year; 497 498 if (gm_tm.tm_year > (2037 - 1900) || 499 gm_tm.tm_year < (1970 - 1900) 500 ) 501 { 502 TIME64_TRACE1("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year); 503 gm_tm.tm_year = S_safe_year((Year)(gm_tm.tm_year + 1900)) - 1900; 504 } 505 506 safe_time = (time_t)S_timegm64(&gm_tm); 507 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) { 508 TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time); 509 return NULL; 510 } 511 512 S_copy_little_tm_to_big_TM(&safe_date, local_tm); 513 514 local_tm->tm_year = orig_year; 515 if( local_tm->tm_year != orig_year ) { 516 TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n", 517 (Year)local_tm->tm_year, (Year)orig_year); 518 519 #ifdef EOVERFLOW 520 errno = EOVERFLOW; 521 #endif 522 return NULL; 523 } 524 525 526 month_diff = local_tm->tm_mon - gm_tm.tm_mon; 527 528 /* When localtime is Dec 31st previous year and 529 gmtime is Jan 1st next year. 530 */ 531 if( month_diff == 11 ) { 532 local_tm->tm_year--; 533 } 534 535 /* When localtime is Jan 1st, next year and 536 gmtime is Dec 31st, previous year. 537 */ 538 if( month_diff == -11 ) { 539 local_tm->tm_year++; 540 } 541 542 /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st 543 in a non-leap xx00. There is one point in the cycle 544 we can't account for which the safe xx00 year is a leap 545 year. So we need to correct for Dec 31st coming out as 546 the 366th day of the year. 547 */ 548 if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 ) 549 local_tm->tm_yday--; 550 551 assert(S_check_tm(local_tm)); 552 553 return local_tm; 554 } 555