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35728b82 | 1 | // SPDX-License-Identifier: LGPL-2.0+ |
57f1f087 Z |
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 | static int __isleap(long year) | |
39 | { | |
40 | return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0); | |
41 | } | |
42 | ||
43 | /* do a mathdiv for long type */ | |
44 | static long math_div(long a, long b) | |
45 | { | |
46 | 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 | static long leaps_between(long y1, long y2) | |
51 | { | |
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; | |
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 | /** | |
e6c2682a | 71 | * time64_to_tm - converts the calendar time to local broken-down time |
57f1f087 Z |
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 | */ | |
e6c2682a | 78 | void time64_to_tm(time64_t totalsecs, int offset, struct tm *result) |
57f1f087 Z |
79 | { |
80 | long days, rem, y; | |
e6c2682a | 81 | int remainder; |
57f1f087 Z |
82 | const unsigned short *ip; |
83 | ||
e6c2682a DD |
84 | days = div_s64_rem(totalsecs, SECS_PER_DAY, &remainder); |
85 | rem = remainder; | |
57f1f087 Z |
86 | rem += offset; |
87 | while (rem < 0) { | |
88 | rem += SECS_PER_DAY; | |
89 | --days; | |
90 | } | |
91 | while (rem >= SECS_PER_DAY) { | |
92 | rem -= SECS_PER_DAY; | |
93 | ++days; | |
94 | } | |
95 | ||
96 | result->tm_hour = rem / SECS_PER_HOUR; | |
97 | rem %= SECS_PER_HOUR; | |
98 | result->tm_min = rem / 60; | |
99 | result->tm_sec = rem % 60; | |
100 | ||
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; | |
105 | ||
106 | y = 1970; | |
107 | ||
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); | |
111 | ||
112 | /* Adjust DAYS and Y to match the guessed year. */ | |
113 | days -= (yg - y) * 365 + leaps_between(y, yg); | |
114 | y = yg; | |
115 | } | |
116 | ||
117 | result->tm_year = y - 1900; | |
118 | ||
119 | result->tm_yday = days; | |
120 | ||
121 | ip = __mon_yday[__isleap(y)]; | |
122 | for (y = 11; days < ip[y]; y--) | |
123 | continue; | |
124 | days -= ip[y]; | |
125 | ||
126 | result->tm_mon = y; | |
127 | result->tm_mday = days + 1; | |
128 | } | |
e6c2682a | 129 | EXPORT_SYMBOL(time64_to_tm); |