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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>
static char *grub_weekday_names[] =
{
"Sunday",
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
};
int
grub_get_weekday (struct grub_datetime *datetime)
{
int a, y, m;
a = (14 - datetime->month) / 12;
y = datetime->year - a;
m = datetime->month + 12 * a - 2;
return (datetime->day + y + y / 4 - y / 100 + y / 400 + (31 * m / 12)) % 7;
}
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 SECPERYEAR (365*SECPERDAY)
#define SECPER4YEARS (4*SECPERYEAR+SECPERDAY)
void
grub_unixtime2datetime (grub_int32_t nix, struct grub_datetime *datetime)
{
int i;
int div;
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 epoch. So count from 1973 instead of 1970 */
nix -= 3*SECPERYEAR + SECPERDAY;
/* Transform C divisions and modulos to mathematical ones */
div = nix / SECPER4YEARS;
if (nix < 0)
div--;
datetime->year = 1973 + 4 * div;
nix -= div * SECPER4YEARS;
/* On 31st December of bissextile years 365 days from the beginning
of the year elapsed but year isn't finished yet */
if (nix / SECPERYEAR == 4)
{
datetime->year += 3;
nix -= 3*SECPERYEAR;
}
else
{
datetime->year += nix / SECPERYEAR;
nix %= SECPERYEAR;
}
for (i = 0; i < 12
&& nix >= ((grub_int32_t) (i==1 && datetime->year % 4 == 0
? 29 : months[i]))*SECPERDAY; i++)
nix -= ((grub_int32_t) (i==1 && datetime->year % 4 == 0
? 29 : months[i]))*SECPERDAY;
datetime->month = i + 1;
datetime->day = 1 + (nix / SECPERDAY);
nix %= SECPERDAY;
datetime->hour = (nix / SECPERHOUR);
nix %= SECPERHOUR;
datetime->minute = nix / SECPERMIN;
datetime->second = nix % SECPERMIN;
}
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