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 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; 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 } 301 302 303 #ifndef HAS_LOCALTIME_R 304 /* Simulate localtime_r() to the best of our ability */ 305 static struct tm * S_localtime_r(const time_t *clock, struct tm *result) { 306 dTHX; /* in case the following is defined as Perl_my_localtime(aTHX_ ...) */ 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 } 320 #endif 321 322 #ifndef HAS_GMTIME_R 323 /* Simulate gmtime_r() to the best of our ability */ 324 static struct tm * S_gmtime_r(const time_t *clock, struct tm *result) { 325 dTHX; /* in case the following is defined as Perl_my_gmtime(aTHX_ ...) */ 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 } 339 #endif 340 341 static struct TM *S_gmtime64_r (const Time64_T *in_time, struct TM *p) 342 { 343 int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday; 344 Time64_T v_tm_tday; 345 int leap; 346 Time64_T m; 347 Time64_T time = *in_time; 348 Year year = 70; 349 int cycles = 0; 350 351 assert(p != NULL); 352 353 /* Use the system gmtime() if time_t is small enough */ 354 if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) { 355 time_t safe_time = (time_t)*in_time; 356 struct tm safe_date; 357 GMTIME_R(&safe_time, &safe_date); 358 359 S_copy_little_tm_to_big_TM(&safe_date, p); 360 assert(S_check_tm(p)); 361 362 return p; 363 } 364 365 #ifdef HAS_TM_TM_GMTOFF 366 p->tm_gmtoff = 0; 367 #endif 368 p->tm_isdst = 0; 369 370 #ifdef HAS_TM_TM_ZONE 371 p->tm_zone = "UTC"; 372 #endif 373 374 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); 380 v_tm_tday = time; 381 382 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); 385 386 v_tm_wday = (int)fmod((v_tm_tday + 4.0), 7.0); 387 if (v_tm_wday < 0) 388 v_tm_wday += 7; 389 m = v_tm_tday; 390 391 if (m >= CHEAT_DAYS) { 392 year = CHEAT_YEARS; 393 m -= CHEAT_DAYS; 394 } 395 396 if (m >= 0) { 397 /* Gregorian cycles, this is huge optimization for distant times */ 398 cycles = (int)floor(m / (Time64_T) days_in_gregorian_cycle); 399 if( cycles ) { 400 m -= (cycles * (Time64_T) days_in_gregorian_cycle); 401 year += (cycles * years_in_gregorian_cycle); 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 { 419 year--; 420 421 /* Gregorian cycles */ 422 cycles = (int)ceil((m / (Time64_T) days_in_gregorian_cycle) + 1); 423 if( cycles ) { 424 m -= (cycles * (Time64_T) days_in_gregorian_cycle); 425 year += (cycles * years_in_gregorian_cycle); 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 ) { 447 #ifdef EOVERFLOW 448 errno = EOVERFLOW; 449 #endif 450 return NULL; 451 } 452 453 /* At this point m is less than a year so casting to an int is safe */ 454 p->tm_mday = (int) m + 1; 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; 461 462 assert(S_check_tm(p)); 463 464 return p; 465 } 466 467 468 static struct TM *S_localtime64_r (const Time64_T *time, struct TM *local_tm) 469 { 470 time_t safe_time; 471 struct tm safe_date; 472 struct TM gm_tm; 473 Year orig_year; 474 int month_diff; 475 476 assert(local_tm != NULL); 477 478 /* Use the system localtime() if time_t is small enough */ 479 if( SHOULD_USE_SYSTEM_LOCALTIME(*time) ) { 480 safe_time = (time_t)*time; 481 482 TIME64_TRACE1("Using system localtime for %lld\n", *time); 483 484 LOCALTIME_R(&safe_time, &safe_date); 485 486 S_copy_little_tm_to_big_TM(&safe_date, local_tm); 487 assert(S_check_tm(local_tm)); 488 489 return local_tm; 490 } 491 492 if( S_gmtime64_r(time, &gm_tm) == NULL ) { 493 TIME64_TRACE1("gmtime64_r returned null for %lld\n", *time); 494 return NULL; 495 } 496 497 orig_year = gm_tm.tm_year; 498 499 if (gm_tm.tm_year > (2037 - 1900) || 500 gm_tm.tm_year < (1970 - 1900) 501 ) 502 { 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; 505 } 506 507 safe_time = (time_t)S_timegm64(&gm_tm); 508 if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) { 509 TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time); 510 return NULL; 511 } 512 513 S_copy_little_tm_to_big_TM(&safe_date, local_tm); 514 515 local_tm->tm_year = orig_year; 516 if( local_tm->tm_year != orig_year ) { 517 TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n", 518 (Year)local_tm->tm_year, (Year)orig_year); 519 520 #ifdef EOVERFLOW 521 errno = EOVERFLOW; 522 #endif 523 return NULL; 524 } 525 526 527 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--; 551 552 assert(S_check_tm(local_tm)); 553 554 return local_tm; 555 } 556