1 /* $OpenBSD: clock_subr.c,v 1.6 2016/08/26 07:09:56 guenther Exp $ */
2 /* $NetBSD: clock_subr.c,v 1.3 1997/03/15 18:11:16 is Exp $ */
3
4 /*
5 * Copyright (c) 1988 University of Utah.
6 * Copyright (c) 1982, 1990, 1993
7 * The Regents of the University of California. All rights reserved.
8 *
9 * This code is derived from software contributed to Berkeley by
10 * the Systems Programming Group of the University of Utah Computer
11 * Science Department.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 * 3. Neither the name of the University nor the names of its contributors
22 * may be used to endorse or promote products derived from this software
23 * without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * SUCH DAMAGE.
36 *
37 * from: Utah $Hdr: clock.c 1.18 91/01/21$
38 *
39 * @(#)clock.c 8.2 (Berkeley) 1/12/94
40 */
41
42 /*
43 * Generic routines to convert between a POSIX date
44 * (seconds since 1/1/1970) and yr/mo/day/hr/min/sec
45 * Derived from arch/hp300/hp300/clock.c
46 */
47
48 #include <sys/types.h>
49 #include <sys/time.h>
50 #include <sys/systm.h>
51
52 static inline int leapyear(int year);
53 #define FEBRUARY 2
54 #define days_in_year(a) (leapyear(a) ? 366 : 365)
55 #define days_in_month(a) (month_days[(a) - 1])
56
57 static const int month_days[12] = {
58 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
59 };
60
61 /*
62 * This inline avoids some unnecessary modulo operations
63 * as compared with the usual macro:
64 * ( ((year % 4) == 0 &&
65 * (year % 100) != 0) ||
66 * ((year % 400) == 0) )
67 * It is otherwise equivalent.
68 */
69 static inline int
leapyear(int year)70 leapyear(int year)
71 {
72 int rv = 0;
73
74 if ((year & 3) == 0) {
75 rv = 1;
76 if ((year % 100) == 0) {
77 rv = 0;
78 if ((year % 400) == 0)
79 rv = 1;
80 }
81 }
82 return (rv);
83 }
84
85 time_t
clock_ymdhms_to_secs(struct clock_ymdhms * dt)86 clock_ymdhms_to_secs(struct clock_ymdhms *dt)
87 {
88 time_t secs;
89 int i, year, days;
90
91 year = dt->dt_year;
92
93 /*
94 * Compute days since start of time.
95 * First from years, then from months.
96 */
97 days = 0;
98 for (i = POSIX_BASE_YEAR; i < year; i++)
99 days += days_in_year(i);
100 if (leapyear(year) && dt->dt_mon > FEBRUARY)
101 days++;
102
103 /* Months */
104 for (i = 1; i < dt->dt_mon; i++)
105 days += days_in_month(i);
106 days += (dt->dt_day - 1);
107
108 /* Add hours, minutes, seconds. */
109 secs = (time_t)((days
110 * 24 + dt->dt_hour)
111 * 60 + dt->dt_min)
112 * 60 + dt->dt_sec;
113
114 return (secs);
115 }
116
117 /* This function uses a copy of month_days[] */
118 #undef days_in_month
119 #define days_in_month(a) (mthdays[(a) - 1])
120
121 void
clock_secs_to_ymdhms(time_t secs,struct clock_ymdhms * dt)122 clock_secs_to_ymdhms(time_t secs, struct clock_ymdhms *dt)
123 {
124 int mthdays[12];
125 int i, days;
126 int rsec; /* remainder seconds */
127
128 memcpy(mthdays, month_days, sizeof(mthdays));
129
130 days = secs / SECDAY;
131 rsec = secs % SECDAY;
132
133 /* Day of week (Note: 1/1/1970 was a Thursday) */
134 dt->dt_wday = (days + 4) % 7;
135
136 /* Subtract out whole years, counting them in i. */
137 for (i = POSIX_BASE_YEAR; days >= days_in_year(i); i++)
138 days -= days_in_year(i);
139 dt->dt_year = i;
140
141 /* Subtract out whole months, counting them in i. */
142 if (leapyear(i))
143 days_in_month(FEBRUARY) = 29;
144 for (i = 1; days >= days_in_month(i); i++)
145 days -= days_in_month(i);
146 dt->dt_mon = i;
147
148 /* Days are what is left over (+1) from all that. */
149 dt->dt_day = days + 1;
150
151 /* Hours, minutes, seconds are easy */
152 dt->dt_hour = rsec / 3600;
153 rsec = rsec % 3600;
154 dt->dt_min = rsec / 60;
155 rsec = rsec % 60;
156 dt->dt_sec = rsec;
157 }
158