LXR uboot/drivers/rtc/date.c

   1/*
   2 * (C) Copyright 2001
   3 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4 *
   5 * SPDX-License-Identifier:     GPL-2.0+
   6 */
   7
   8#include <common.h>
   9#include <command.h>
  10#include <errno.h>
  11#include <rtc.h>
  12
  13#if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP)
  14
  15#define FEBRUARY                2
  16#define STARTOFTIME             1970
  17#define SECDAY                  86400L
  18#define SECYR                   (SECDAY * 365)
  19#define leapyear(year)          ((year) % 4 == 0)
  20#define days_in_year(a)         (leapyear(a) ? 366 : 365)
  21#define days_in_month(a)        (month_days[(a) - 1])
  22
  23static int month_days[12] = {
  24        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  25};
  26
  27static int month_offset[] = {
  28        0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
  29};
  30
  31/*
  32 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
  33 */
  34int rtc_calc_weekday(struct rtc_time *tm)
  35{
  36        int leaps_to_date;
  37        int last_year;
  38        int day;
  39
  40        if (tm->tm_year < 1753)
  41                return -1;
  42        last_year = tm->tm_year - 1;
  43
  44        /* Number of leap corrections to apply up to end of last year */
  45        leaps_to_date = last_year / 4 - last_year / 100 + last_year / 400;
  46
  47        /*
  48         * This year is a leap year if it is divisible by 4 except when it is
  49         * divisible by 100 unless it is divisible by 400
  50         *
  51         * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 is.
  52         */
  53        if (tm->tm_year % 4 == 0 &&
  54            ((tm->tm_year % 100 != 0) || (tm->tm_year % 400 == 0)) &&
  55            tm->tm_mon > 2) {
  56                /* We are past Feb. 29 in a leap year */
  57                day = 1;
  58        } else {
  59                day = 0;
  60        }
  61
  62        day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] +
  63                        tm->tm_mday;
  64        tm->tm_wday = day % 7;
  65
  66        return 0;
  67}
  68
  69int rtc_to_tm(int tim, struct rtc_time *tm)
  70{
  71        register int i;
  72        register long hms, day;
  73
  74        day = tim / SECDAY;
  75        hms = tim % SECDAY;
  76
  77        /* Hours, minutes, seconds are easy */
  78        tm->tm_hour = hms / 3600;
  79        tm->tm_min = (hms % 3600) / 60;
  80        tm->tm_sec = (hms % 3600) % 60;
  81
  82        /* Number of years in days */
  83        for (i = STARTOFTIME; day >= days_in_year(i); i++)
  84                day -= days_in_year(i);
  85        tm->tm_year = i;
  86
  87        /* Number of months in days left */
  88        if (leapyear(tm->tm_year))
  89                days_in_month(FEBRUARY) = 29;
  90        for (i = 1; day >= days_in_month(i); i++)
  91                day -= days_in_month(i);
  92        days_in_month(FEBRUARY) = 28;
  93        tm->tm_mon = i;
  94
  95        /* Days are what is left over (+1) from all that */
  96        tm->tm_mday = day + 1;
  97
  98        /* Zero unused fields */
  99        tm->tm_yday = 0;
 100        tm->tm_isdst = 0;
 101
 102        /*
 103         * Determine the day of week
 104         */
 105        return rtc_calc_weekday(tm);
 106}
 107
 108/*
 109 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 110 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 111 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 112 *
 113 * [For the Julian calendar (which was used in Russia before 1917,
 114 * Britain & colonies before 1752, anywhere else before 1582,
 115 * and is still in use by some communities) leave out the
 116 * -year / 100 + year / 400 terms, and add 10.]
 117 *
 118 * This algorithm was first published by Gauss (I think).
 119 *
 120 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 121 * machines where long is 32-bit! (However, as time_t is signed, we
 122 * will already get problems at other places on 2038-01-19 03:14:08)
 123 */
 124unsigned long rtc_mktime(const struct rtc_time *tm)
 125{
 126        int mon = tm->tm_mon;
 127        int year = tm->tm_year;
 128        int days, hours;
 129
 130        mon -= 2;
 131        if (0 >= (int)mon) {    /* 1..12 -> 11, 12, 1..10 */
 132                mon += 12;      /* Puts Feb last since it has leap day */
 133                year -= 1;
 134        }
 135
 136        days = (unsigned long)(year / 4 - year / 100 + year / 400 +
 137                        367 * mon / 12 + tm->tm_mday) +
 138                        year * 365 - 719499;
 139        hours = days * 24 + tm->tm_hour;
 140        return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec;
 141}
 142
 143#endif
 144