109 lines
3.1 KiB
C
109 lines
3.1 KiB
C
/* datetime.c - Module for common datetime function. */
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/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2008 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <grub/datetime.h>
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#include <grub/i18n.h>
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static const char *const grub_weekday_names[] =
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{
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N_("Sunday"),
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N_("Monday"),
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N_("Tuesday"),
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N_("Wednesday"),
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N_("Thursday"),
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N_("Friday"),
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N_("Saturday"),
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};
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int
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grub_get_weekday (struct grub_datetime *datetime)
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{
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unsigned a, y, m;
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if (datetime->month <= 2)
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a = 1;
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else
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a = 0;
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y = datetime->year - a;
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m = datetime->month + 12 * a - 2;
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return (datetime->day + y + y / 4 - y / 100 + y / 400 + (31 * m / 12)) % 7;
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}
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const char *
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grub_get_weekday_name (struct grub_datetime *datetime)
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{
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return _ (grub_weekday_names[grub_get_weekday (datetime)]);
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}
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#define SECPERMIN 60
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#define SECPERHOUR (60*SECPERMIN)
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#define SECPERDAY (24*SECPERHOUR)
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#define DAYSPERYEAR 365
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#define DAYSPER4YEARS (4*DAYSPERYEAR+1)
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void
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grub_unixtime2datetime (grub_int32_t nix, struct grub_datetime *datetime)
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{
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int i;
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grub_uint8_t months[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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/* In the period of validity of unixtime all years divisible by 4
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are bissextile*/
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/* Convenience: let's have 3 consecutive non-bissextile years
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at the beginning of the counting date. So count from 1901. */
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int days_epoch;
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/* Number of days since 1st Januar, 1901. */
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unsigned days;
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/* Seconds into current day. */
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unsigned secs_in_day;
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/* Transform C divisions and modulos to mathematical ones */
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if (nix < 0)
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days_epoch = -(((unsigned) (SECPERDAY-nix-1)) / SECPERDAY);
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else
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days_epoch = ((unsigned) nix) / SECPERDAY;
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secs_in_day = nix - days_epoch * SECPERDAY;
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days = days_epoch + 69 * DAYSPERYEAR + 17;
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datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
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days %= DAYSPER4YEARS;
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/* On 31st December of bissextile years 365 days from the beginning
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of the year elapsed but year isn't finished yet */
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if (days / DAYSPERYEAR == 4)
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{
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datetime->year += 3;
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days -= 3*DAYSPERYEAR;
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}
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else
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{
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datetime->year += days / DAYSPERYEAR;
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days %= DAYSPERYEAR;
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}
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for (i = 0; i < 12
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&& days >= (i==1 && datetime->year % 4 == 0
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? 29 : months[i]); i++)
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days -= (i==1 && datetime->year % 4 == 0
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? 29 : months[i]);
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datetime->month = i + 1;
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datetime->day = 1 + days;
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datetime->hour = (secs_in_day / SECPERHOUR);
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secs_in_day %= SECPERHOUR;
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datetime->minute = secs_in_day / SECPERMIN;
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datetime->second = secs_in_day % SECPERMIN;
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}
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