2 * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc.
3 * This file is part of the GNU C Library.
4 * Contributed by Paul Eggert (eggert@twinsun.com).
6 * The GNU C Library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public License as
8 * published by the Free Software Foundation; either version 2 of the
9 * License, or (at your option) any later version.
11 * The GNU C Library 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 GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with the GNU C Library; see the file COPYING.LIB. If not,
18 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
23 * Converts the calendar time to broken-down time representation
24 * Based on code from glibc-2.6
27 * Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
30 #include <linux/time.h>
31 #include <linux/module.h>
34 * Nonzero if YEAR is a leap year (every 4 years,
35 * except every 100th isn't, and every 400th is).
37 static int __isleap(long year)
39 return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);
42 /* do a mathdiv for long type */
43 static long math_div(long a, long b)
45 return a / b - (a % b < 0);
48 /* How many leap years between y1 and y2, y1 must less or equal to y2 */
49 static long leaps_between(long y1, long y2)
51 long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100)
52 + math_div(y1 - 1, 400);
53 long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100)
54 + math_div(y2 - 1, 400);
55 return leaps2 - leaps1;
58 /* How many days come before each month (0-12). */
59 static const unsigned short __mon_yday[2][13] = {
61 {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
63 {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
66 #define SECS_PER_HOUR (60 * 60)
67 #define SECS_PER_DAY (SECS_PER_HOUR * 24)
70 * time64_to_tm - converts the calendar time to local broken-down time
72 * @totalsecs the number of seconds elapsed since 00:00:00 on January 1, 1970,
73 * Coordinated Universal Time (UTC).
74 * @offset offset seconds adding to totalsecs.
75 * @result pointer to struct tm variable to receive broken-down time
77 void time64_to_tm(time64_t totalsecs, int offset, struct tm *result)
81 const unsigned short *ip;
83 days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder);
90 while (rem >= SECS_PER_DAY) {
95 result->tm_hour = rem / SECS_PER_HOUR;
97 result->tm_min = rem / 60;
98 result->tm_sec = rem % 60;
100 /* January 1, 1970 was a Thursday. */
101 result->tm_wday = (4 + days) % 7;
102 if (result->tm_wday < 0)
103 result->tm_wday += 7;
107 while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {
108 /* Guess a corrected year, assuming 365 days per year. */
109 long yg = y + math_div(days, 365);
111 /* Adjust DAYS and Y to match the guessed year. */
112 days -= (yg - y) * 365 + leaps_between(y, yg);
116 result->tm_year = y - 1900;
118 result->tm_yday = days;
120 ip = __mon_yday[__isleap(y)];
121 for (y = 11; days < ip[y]; y--)
126 result->tm_mday = days + 1;
128 EXPORT_SYMBOL(time64_to_tm);