Line data    Source code

       1             : // SPDX-License-Identifier: LGPL-2.0+
       2             : /*
       3             :  * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
       4             :  * This file is part of the GNU C Library.
       5             :  * Contributed by Paul Eggert (eggert@twinsun.com).
       6             :  *
       7             :  * The GNU C Library is free software; you can redistribute it and/or
       8             :  * modify it under the terms of the GNU Library General Public License as
       9             :  * published by the Free Software Foundation; either version 2 of the
      10             :  * License, or (at your option) any later version.
      11             :  *
      12             :  * The GNU C Library is distributed in the hope that it will be useful,
      13             :  * but WITHOUT ANY WARRANTY; without even the implied warranty of
      14             :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      15             :  * Library General Public License for more details.
      16             :  *
      17             :  * You should have received a copy of the GNU Library General Public
      18             :  * License along with the GNU C Library; see the file COPYING.LIB.  If not,
      19             :  * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
      20             :  * Boston, MA 02111-1307, USA.
      21             :  */
      22             : 
      23             : /*
      24             :  * Converts the calendar time to broken-down time representation
      25             :  * Based on code from glibc-2.6
      26             :  *
      27             :  * 2009-7-14:
      28             :  *   Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
      29             :  */
      30             : 
      31             : #include <linux/time.h>
      32             : #include <linux/module.h>
      33             : 
      34             : /*
      35             :  * Nonzero if YEAR is a leap year (every 4 years,
      36             :  * except every 100th isn't, and every 400th is).
      37             :  */
      38           0 : static int __isleap(long year)
      39             : {
      40           0 :         return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);
      41             : }
      42             : 
      43             : /* do a mathdiv for long type */
      44           0 : static long math_div(long a, long b)
      45             : {
      46           0 :         return a / b - (a % b < 0);
      47             : }
      48             : 
      49             : /* How many leap years between y1 and y2, y1 must less or equal to y2 */
      50           0 : static long leaps_between(long y1, long y2)
      51             : {
      52           0 :         long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100)
      53           0 :                 + math_div(y1 - 1, 400);
      54           0 :         long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100)
      55           0 :                 + math_div(y2 - 1, 400);
      56           0 :         return leaps2 - leaps1;
      57             : }
      58             : 
      59             : /* How many days come before each month (0-12). */
      60             : static const unsigned short __mon_yday[2][13] = {
      61             :         /* Normal years. */
      62             :         {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
      63             :         /* Leap years. */
      64             :         {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
      65             : };
      66             : 
      67             : #define SECS_PER_HOUR   (60 * 60)
      68             : #define SECS_PER_DAY    (SECS_PER_HOUR * 24)
      69             : 
      70             : /**
      71             :  * time64_to_tm - converts the calendar time to local broken-down time
      72             :  *
      73             :  * @totalsecs:  the number of seconds elapsed since 00:00:00 on January 1, 1970,
      74             :  *              Coordinated Universal Time (UTC).
      75             :  * @offset:     offset seconds adding to totalsecs.
      76             :  * @result:     pointer to struct tm variable to receive broken-down time
      77             :  */
      78           0 : void time64_to_tm(time64_t totalsecs, int offset, struct tm *result)
      79             : {
      80           0 :         long days, rem, y;
      81           0 :         int remainder;
      82           0 :         const unsigned short *ip;
      83             : 
      84           0 :         days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder);
      85           0 :         rem = remainder;
      86           0 :         rem += offset;
      87           0 :         while (rem < 0) {
      88           0 :                 rem += SECS_PER_DAY;
      89           0 :                 --days;
      90             :         }
      91           0 :         while (rem >= SECS_PER_DAY) {
      92           0 :                 rem -= SECS_PER_DAY;
      93           0 :                 ++days;
      94             :         }
      95             : 
      96           0 :         result->tm_hour = rem / SECS_PER_HOUR;
      97           0 :         rem %= SECS_PER_HOUR;
      98           0 :         result->tm_min = rem / 60;
      99           0 :         result->tm_sec = rem % 60;
     100             : 
     101             :         /* January 1, 1970 was a Thursday. */
     102           0 :         result->tm_wday = (4 + days) % 7;
     103           0 :         if (result->tm_wday < 0)
     104           0 :                 result->tm_wday += 7;
     105             : 
     106             :         y = 1970;
     107             : 
     108           0 :         while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {
     109             :                 /* Guess a corrected year, assuming 365 days per year. */
     110           0 :                 long yg = y + math_div(days, 365);
     111             : 
     112             :                 /* Adjust DAYS and Y to match the guessed year. */
     113           0 :                 days -= (yg - y) * 365 + leaps_between(y, yg);
     114           0 :                 y = yg;
     115             :         }
     116             : 
     117           0 :         result->tm_year = y - 1900;
     118             : 
     119           0 :         result->tm_yday = days;
     120             : 
     121           0 :         ip = __mon_yday[__isleap(y)];
     122           0 :         for (y = 11; days < ip[y]; y--)
     123           0 :                 continue;
     124           0 :         days -= ip[y];
     125             : 
     126           0 :         result->tm_mon = y;
     127           0 :         result->tm_mday = days + 1;
     128           0 : }
     129             : EXPORT_SYMBOL(time64_to_tm);