arch/all-pc/boot/grub2-aros/grub-core/normal/datetime.c

   1 /* datetime.c - Module for common datetime function.  */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2008  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software: you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation, either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  GRUB is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <grub/datetime.h>
  21 #include <grub/i18n.h>
  22
  23 static const char *const grub_weekday_names[] =
  24 {
  25   N_("Sunday"),
  26   N_("Monday"),
  27   N_("Tuesday"),
  28   N_("Wednesday"),
  29   N_("Thursday"),
  30   N_("Friday"),
  31   N_("Saturday"),
  32 };
  33
  34 int
  35 grub_get_weekday (struct grub_datetime *datetime)
  36 {
  37   unsigned a, y, m;
  38
  39   if (datetime->month <= 2)
  40     a = 1;
  41   else
  42     a = 0;
  43   y = datetime->year - a;
  44   m = datetime->month + 12 * a - 2;
  45
  46   return (datetime->day + y + y / 4 - y / 100 + y / 400 + (31 * m / 12)) % 7;
  47 }
  48
  49 const char *
  50 grub_get_weekday_name (struct grub_datetime *datetime)
  51 {
  52   return _ (grub_weekday_names[grub_get_weekday (datetime)]);
  53 }
  54
  55 #define SECPERMIN 60
  56 #define SECPERHOUR (60*SECPERMIN)
  57 #define SECPERDAY (24*SECPERHOUR)
  58 #define DAYSPERYEAR 365
  59 #define DAYSPER4YEARS (4*DAYSPERYEAR+1)
  60
  61
  62 void
  63 grub_unixtime2datetime (grub_int32_t nix, struct grub_datetime *datetime)
  64 {
  65   int i;
  66   grub_uint8_t months[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  67   /* In the period of validity of unixtime all years divisible by 4
  68      are bissextile*/
  69   /* Convenience: let's have 3 consecutive non-bissextile years
  70      at the beginning of the counting date. So count from 1901. */
  71   int days_epoch;
  72   /* Number of days since 1st Januar, 1901.  */
  73   unsigned days;
  74   /* Seconds into current day.  */
  75   unsigned secs_in_day;
  76   /* Transform C divisions and modulos to mathematical ones */
  77   if (nix < 0)
  78     days_epoch = -(((unsigned) (SECPERDAY-nix-1)) / SECPERDAY);
  79   else
  80     days_epoch = ((unsigned) nix) / SECPERDAY;
  81   secs_in_day = nix - days_epoch * SECPERDAY;
  82   days = days_epoch + 69 * DAYSPERYEAR + 17;
  83
  84   datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
  85   days %= DAYSPER4YEARS;
  86   /* On 31st December of bissextile years 365 days from the beginning
  87      of the year elapsed but year isn't finished yet */
  88   if (days / DAYSPERYEAR == 4)
  89     {
  90       datetime->year += 3;
  91       days -= 3*DAYSPERYEAR;
  92     }
  93   else
  94     {
  95       datetime->year += days / DAYSPERYEAR;
  96       days %= DAYSPERYEAR;
  97     }
  98   for (i = 0; i < 12
  99          && days >= (i==1 && datetime->year % 4 == 0
 100                       ? 29 : months[i]); i++)
 101     days -= (i==1 && datetime->year % 4 == 0
 102                             ? 29 : months[i]);
 103   datetime->month = i + 1;
 104   datetime->day = 1 + days;
 105   datetime->hour = (secs_in_day / SECPERHOUR);
 106   secs_in_day %= SECPERHOUR;
 107   datetime->minute = secs_in_day / SECPERMIN;
 108   datetime->second = secs_in_day % SECPERMIN;
 109 }