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/* datetime.c - Module for common datetime function. */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2008 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/datetime.h>
#include <grub/i18n.h>
#include <grub/misc.h>
#include <grub/mm.h>
#ifdef GRUB_MACHINE_EMU
#include <grub/dl.h>
GRUB_MOD_LICENSE ("GPLv3+");
#endif
static const char *const grub_weekday_names[] =
{
N_("Sunday"),
N_("Monday"),
N_("Tuesday"),
N_("Wednesday"),
N_("Thursday"),
N_("Friday"),
N_("Saturday"),
};
int
grub_get_weekday (struct grub_datetime *datetime)
{
unsigned a, y, m;
if (datetime->month <= 2)
a = 1;
else
a = 0;
y = datetime->year - a;
m = datetime->month + 12 * a - 2;
return (datetime->day + y + y / 4 - y / 100 + y / 400 + (31 * m / 12)) % 7;
}
const char *
grub_get_weekday_name (struct grub_datetime *datetime)
{
return _ (grub_weekday_names[grub_get_weekday (datetime)]);
}
#define SECPERMIN 60
#define SECPERHOUR (60*SECPERMIN)
#define SECPERDAY (24*SECPERHOUR)
#define DAYSPERYEAR 365
#define DAYSPER4YEARS (4*DAYSPERYEAR+1)
/* 24 leap years in 100 years */
#define DAYSPER100YEARS (100 * DAYSPERYEAR + 24)
/* 97 leap years in 400 years */
#define DAYSPER400YEARS (400 * DAYSPERYEAR + 97)
void
grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
{
int i;
grub_uint8_t months[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
/* In the period of validity of unixtime all years divisible by 4
are bissextile*/
/* Convenience: let's have 3 consecutive non-bissextile years
at the beginning of the counting date. So count from 1901. */
int days_epoch;
/* Number of days since 1st January, 1 (proleptic). */
unsigned days;
/* Seconds into current day. */
unsigned secs_in_day;
/* Tracks whether this is a leap year. */
bool bisextile;
/* Transform C divisions and modulos to mathematical ones */
if (nix < 0)
/*
* The result of division here shouldn't be larger than GRUB_INT_MAX.
* So, it's safe to store the result back in an int.
*/
days_epoch = -(grub_divmod64 (((grub_int64_t) (SECPERDAY) - nix - 1), SECPERDAY, NULL));
else
days_epoch = grub_divmod64 (nix, SECPERDAY, NULL);
secs_in_day = nix - days_epoch * SECPERDAY;
/*
* 1970 is Unix Epoch. Adjust to a year 1 epoch:
* Leap year logic:
* - Years evenly divisible by 400 are leap years
* - Otherwise, if divisible by 100 are not leap years
* - Otherwise, if divisible by 4 are leap years
* There are four 400-year periods (1600 years worth of days with leap days)
* There are 369 years in addition to the four 400 year periods
* There are three 100-year periods worth of leap days (3*24)
* There are 17 leap days in 69 years (beyond the three 100 year periods)
*/
days = 4 * DAYSPER400YEARS + 369 * DAYSPERYEAR + 3 * 24 + 17 + days_epoch;
datetime->year = 1 + 400 * (days / DAYSPER400YEARS);
days %= DAYSPER400YEARS;
/*
* On 31st December of bissextile (leap) years 365 days from the beginning
* of the year elapsed but year isn't finished yet - every 400 years
* 396 is 4 years less than 400 year leap cycle
* 96 is 1 day less than number of leap days in 400 years
*/
if (days / DAYSPER100YEARS == 4)
{
datetime->year += 396;
days -= 396 * DAYSPERYEAR + 96;
}
else
{
datetime->year += 100 * (days / DAYSPER100YEARS);
days %= DAYSPER100YEARS;
}
datetime->year += 4 * (days / DAYSPER4YEARS);
days %= DAYSPER4YEARS;
/*
* On 31st December of bissextile (leap) years 365 days from the beginning
* of the year elapsed but year isn't finished yet - every 4 years
*/
if (days / DAYSPERYEAR == 4)
{
datetime->year += 3;
days -= 3 * DAYSPERYEAR;
}
else
{
datetime->year += days / DAYSPERYEAR;
days %= DAYSPERYEAR;
}
bisextile = (datetime->year % 4 == 0
&& (datetime->year % 100 != 0
|| datetime->year % 400 == 0)) ? true : false;
for (i = 0;
i < 12 && days >= ((i == 1 && bisextile == true) ? 29 : months[i]);
i++)
days -= ((i == 1 && bisextile == true) ? 29 : months[i]);
datetime->month = i + 1;
datetime->day = 1 + days;
datetime->hour = (secs_in_day / SECPERHOUR);
secs_in_day %= SECPERHOUR;
datetime->minute = secs_in_day / SECPERMIN;
datetime->second = secs_in_day % SECPERMIN;
}
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