101 lines
2.8 KiB
C
101 lines
2.8 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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static char *grub_weekday_names[] =
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{
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"Sunday",
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"Monday",
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"Tuesday",
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"Wednesday",
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"Thursday",
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"Friday",
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"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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int a, y, m;
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a = (14 - datetime->month) / 12;
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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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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 SECPERYEAR (365*SECPERDAY)
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#define SECPER4YEARS (4*SECPERYEAR+SECPERDAY)
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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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int div;
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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 epoch. So count from 1973 instead of 1970 */
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nix -= 3*SECPERYEAR + SECPERDAY;
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/* Transform C divisions and modulos to mathematical ones */
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div = nix / SECPER4YEARS;
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if (nix < 0)
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div--;
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datetime->year = 1973 + 4 * div;
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nix -= div * SECPER4YEARS;
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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 (nix / SECPERYEAR == 4)
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{
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datetime->year += 3;
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nix -= 3*SECPERYEAR;
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}
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else
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{
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datetime->year += nix / SECPERYEAR;
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nix %= SECPERYEAR;
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}
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for (i = 0; i < 12
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&& nix >= ((grub_int32_t) (i==1 && datetime->year % 4 == 0
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? 29 : months[i]))*SECPERDAY; i++)
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nix -= ((grub_int32_t) (i==1 && datetime->year % 4 == 0
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? 29 : months[i]))*SECPERDAY;
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datetime->month = i + 1;
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datetime->day = 1 + (nix / SECPERDAY);
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nix %= SECPERDAY;
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datetime->hour = (nix / SECPERHOUR);
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nix %= SECPERHOUR;
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datetime->minute = nix / SECPERMIN;
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datetime->second = nix % SECPERMIN;
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}
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