Rev 4921 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* |
| 2 | * gmtime_r.c |
||
| 6099 | serge | 3 | * Original Author: Adapted from tzcode maintained by Arthur David Olson. |
| 4 | * Modifications: |
||
| 5 | * - Changed to mktm_r and added __tzcalc_limits - 04/10/02, Jeff Johnston |
||
| 6 | * - Fixed bug in mday computations - 08/12/04, Alex Mogilnikov |
||
| 7 | * - Fixed bug in __tzcalc_limits - 08/12/04, Alex Mogilnikov |
||
| 8 | * - Move code from _mktm_r() to gmtime_r() - 05/09/14, Freddie Chopin |
||
| 9 | * - Fixed bug in calculations for dates after year 2069 or before year 1901. Ideas for |
||
| 10 | * solution taken from musl's __secs_to_tm() - 07/12/2014, Freddie Chopin |
||
| 11 | * |
||
| 12 | * - Use faster algorithm from civil_from_days() by Howard Hinnant - 12/06/2014, |
||
| 13 | * Freddie Chopin |
||
| 14 | * |
||
| 15 | * Converts the calendar time pointed to by tim_p into a broken-down time |
||
| 16 | * expressed as local time. Returns a pointer to a structure containing the |
||
| 17 | * broken-down time. |
||
| 4349 | Serge | 18 | */ |
| 19 | |||
| 20 | #include "local.h" |
||
| 21 | |||
| 6099 | serge | 22 | /* Move epoch from 01.01.1970 to 01.03.0000 (yes, Year 0) - this is the first |
| 23 | * day of a 400-year long "era", right after additional day of leap year. |
||
| 24 | * This adjustment is required only for date calculation, so instead of |
||
| 25 | * modifying time_t value (which would require 64-bit operations to work |
||
| 26 | * correctly) it's enough to adjust the calculated number of days since epoch. |
||
| 27 | */ |
||
| 28 | #define EPOCH_ADJUSTMENT_DAYS 719468L |
||
| 29 | /* year to which the adjustment was made */ |
||
| 30 | #define ADJUSTED_EPOCH_YEAR 0 |
||
| 31 | /* 1st March of year 0 is Wednesday */ |
||
| 32 | #define ADJUSTED_EPOCH_WDAY 3 |
||
| 33 | /* there are 97 leap years in 400-year periods. ((400 - 97) * 365 + 97 * 366) */ |
||
| 34 | #define DAYS_PER_ERA 146097L |
||
| 35 | /* there are 24 leap years in 100-year periods. ((100 - 24) * 365 + 24 * 366) */ |
||
| 36 | #define DAYS_PER_CENTURY 36524L |
||
| 37 | /* there is one leap year every 4 years */ |
||
| 38 | #define DAYS_PER_4_YEARS (3 * 365 + 366) |
||
| 39 | /* number of days in a non-leap year */ |
||
| 40 | #define DAYS_PER_YEAR 365 |
||
| 41 | /* number of days in January */ |
||
| 42 | #define DAYS_IN_JANUARY 31 |
||
| 43 | /* number of days in non-leap February */ |
||
| 44 | #define DAYS_IN_FEBRUARY 28 |
||
| 45 | /* number of years per era */ |
||
| 46 | #define YEARS_PER_ERA 400 |
||
| 47 | |||
| 4349 | Serge | 48 | struct tm * |
| 49 | _DEFUN (gmtime_r, (tim_p, res), |
||
| 4921 | Serge | 50 | _CONST time_t *__restrict tim_p _AND |
| 51 | struct tm *__restrict res) |
||
| 4349 | Serge | 52 | { |
| 6099 | serge | 53 | long days, rem; |
| 54 | _CONST time_t lcltime = *tim_p; |
||
| 55 | int era, weekday, year; |
||
| 56 | unsigned erayear, yearday, month, day; |
||
| 57 | unsigned long eraday; |
||
| 58 | |||
| 59 | days = ((long)lcltime) / SECSPERDAY + EPOCH_ADJUSTMENT_DAYS; |
||
| 60 | rem = ((long)lcltime) % SECSPERDAY; |
||
| 61 | if (rem < 0) |
||
| 62 | { |
||
| 63 | rem += SECSPERDAY; |
||
| 64 | --days; |
||
| 65 | } |
||
| 66 | |||
| 67 | /* compute hour, min, and sec */ |
||
| 68 | res->tm_hour = (int) (rem / SECSPERHOUR); |
||
| 69 | rem %= SECSPERHOUR; |
||
| 70 | res->tm_min = (int) (rem / SECSPERMIN); |
||
| 71 | res->tm_sec = (int) (rem % SECSPERMIN); |
||
| 72 | |||
| 73 | /* compute day of week */ |
||
| 74 | if ((weekday = ((ADJUSTED_EPOCH_WDAY + days) % DAYSPERWEEK)) < 0) |
||
| 75 | weekday += DAYSPERWEEK; |
||
| 76 | res->tm_wday = weekday; |
||
| 77 | |||
| 78 | /* compute year, month, day & day of year */ |
||
| 79 | /* for description of this algorithm see |
||
| 80 | * http://howardhinnant.github.io/date_algorithms.html#civil_from_days */ |
||
| 81 | era = (days >= 0 ? days : days - (DAYS_PER_ERA - 1)) / DAYS_PER_ERA; |
||
| 82 | eraday = days - era * DAYS_PER_ERA; /* [0, 146096] */ |
||
| 83 | erayear = (eraday - eraday / (DAYS_PER_4_YEARS - 1) + eraday / DAYS_PER_CENTURY - |
||
| 84 | eraday / (DAYS_PER_ERA - 1)) / 365; /* [0, 399] */ |
||
| 85 | yearday = eraday - (DAYS_PER_YEAR * erayear + erayear / 4 - erayear / 100); /* [0, 365] */ |
||
| 86 | month = (5 * yearday + 2) / 153; /* [0, 11] */ |
||
| 87 | day = yearday - (153 * month + 2) / 5 + 1; /* [1, 31] */ |
||
| 88 | month += month < 10 ? 2 : -10; |
||
| 89 | year = ADJUSTED_EPOCH_YEAR + erayear + era * YEARS_PER_ERA + (month <= 1); |
||
| 90 | |||
| 91 | res->tm_yday = yearday >= DAYS_PER_YEAR - DAYS_IN_JANUARY - DAYS_IN_FEBRUARY ? |
||
| 92 | yearday - (DAYS_PER_YEAR - DAYS_IN_JANUARY - DAYS_IN_FEBRUARY) : |
||
| 93 | yearday + DAYS_IN_JANUARY + DAYS_IN_FEBRUARY + isleap(erayear); |
||
| 94 | res->tm_year = year - YEAR_BASE; |
||
| 95 | res->tm_mon = month; |
||
| 96 | res->tm_mday = day; |
||
| 97 | |||
| 98 | res->tm_isdst = 0; |
||
| 99 | |||
| 100 | return (res); |
||
| 4349 | Serge | 101 | } |