1 // SPDX-License-Identifier: LGPL-2.0+
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).
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.
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.
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.
24 * Converts the calendar time to broken-down time representation
25 * Based on code from glibc-2.6
28 * Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com>
31 #include <linux/time.h>
32 #include <linux/module.h>
35 * Nonzero if YEAR is a leap year (every 4 years,
36 * except every 100th isn't, and every 400th is).
38 static int __isleap(long year
)
40 return (year
) % 4 == 0 && ((year
) % 100 != 0 || (year
) % 400 == 0);
43 /* do a mathdiv for long type */
44 static long math_div(long a
, long b
)
46 return a
/ b
- (a
% b
< 0);
49 /* How many leap years between y1 and y2, y1 must less or equal to y2 */
50 static long leaps_between(long y1
, long y2
)
52 long leaps1
= math_div(y1
- 1, 4) - math_div(y1
- 1, 100)
53 + math_div(y1
- 1, 400);
54 long leaps2
= math_div(y2
- 1, 4) - math_div(y2
- 1, 100)
55 + math_div(y2
- 1, 400);
56 return leaps2
- leaps1
;
59 /* How many days come before each month (0-12). */
60 static const unsigned short __mon_yday
[2][13] = {
62 {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
64 {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}
67 #define SECS_PER_HOUR (60 * 60)
68 #define SECS_PER_DAY (SECS_PER_HOUR * 24)
71 * time64_to_tm - converts the calendar time to local broken-down time
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
78 void time64_to_tm(time64_t totalsecs
, int offset
, struct tm
*result
)
82 const unsigned short *ip
;
84 days
= div_s64_rem(totalsecs
, SECS_PER_DAY
, &remainder
);
91 while (rem
>= SECS_PER_DAY
) {
96 result
->tm_hour
= rem
/ SECS_PER_HOUR
;
98 result
->tm_min
= rem
/ 60;
99 result
->tm_sec
= rem
% 60;
101 /* January 1, 1970 was a Thursday. */
102 result
->tm_wday
= (4 + days
) % 7;
103 if (result
->tm_wday
< 0)
104 result
->tm_wday
+= 7;
108 while (days
< 0 || days
>= (__isleap(y
) ? 366 : 365)) {
109 /* Guess a corrected year, assuming 365 days per year. */
110 long yg
= y
+ math_div(days
, 365);
112 /* Adjust DAYS and Y to match the guessed year. */
113 days
-= (yg
- y
) * 365 + leaps_between(y
, yg
);
117 result
->tm_year
= y
- 1900;
119 result
->tm_yday
= days
;
121 ip
= __mon_yday
[__isleap(y
)];
122 for (y
= 11; days
< ip
[y
]; y
--)
127 result
->tm_mday
= days
+ 1;
129 EXPORT_SYMBOL(time64_to_tm
);