1 /* $OpenBSD: clock_subr.c,v 1.2 2006/11/14 18:00:27 jmc 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/systm.h>
50
51 #include <dev/clock_subr.h>
52
53 static inline int leapyear(int year);
54 #define FEBRUARY 2
55 #define days_in_year(a) (leapyear(a) ? 366 : 365)
56 #define days_in_month(a) (month_days[(a) - 1])
57
58 static const int month_days[12] = {
59 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
60 };
61
62 /*
63 * This inline avoids some unnecessary modulo operations
64 * as compared with the usual macro:
65 * ( ((year % 4) == 0 &&
66 * (year % 100) != 0) ||
67 * ((year % 400) == 0) )
68 * It is otherwise equivalent.
69 */
70 static inline int
71 leapyear(int year)
72 {
73 int rv = 0;
74
75 if ((year & 3) == 0) {
76 rv = 1;
77 if ((year % 100) == 0) {
78 rv = 0;
79 if ((year % 400) == 0)
80 rv = 1;
81 }
82 }
83 return (rv);
84 }
85
86 time_t
87 clock_ymdhms_to_secs(struct clock_ymdhms *dt)
88 {
89 time_t secs;
90 int i, year, days;
91
92 year = dt->dt_year;
93
94 /*
95 * Compute days since start of time.
96 * First from years, then from months.
97 */
98 days = 0;
99 for (i = POSIX_BASE_YEAR; i < year; i++)
100 days += days_in_year(i);
101 if (leapyear(year) && dt->dt_mon > FEBRUARY)
102 days++;
103
104 /* Months */
105 for (i = 1; i < dt->dt_mon; i++)
106 days += days_in_month(i);
107 days += (dt->dt_day - 1);
108
109 /* Add hours, minutes, seconds. */
110 secs = ((days
111 * 24 + dt->dt_hour)
112 * 60 + dt->dt_min)
113 * 60 + dt->dt_sec;
114
115 return (secs);
116 }
117
118 /* This function uses a copy of month_days[] */
119 #undef days_in_month
120 #define days_in_month(a) (mthdays[(a) - 1])
121
122 void
123 clock_secs_to_ymdhms(time_t secs, struct clock_ymdhms *dt)
124 {
125 int mthdays[12];
126 int i, days;
127 int rsec; /* remainder seconds */
128
129 bcopy(month_days, mthdays, sizeof(mthdays));
130
131 days = secs / SECDAY;
132 rsec = secs % SECDAY;
133
134 /* Day of week (Note: 1/1/1970 was a Thursday) */
135 dt->dt_wday = (days + 4) % 7;
136
137 /* Subtract out whole years, counting them in i. */
138 for (i = POSIX_BASE_YEAR; days >= days_in_year(i); i++)
139 days -= days_in_year(i);
140 dt->dt_year = i;
141
142 /* Subtract out whole months, counting them in i. */
143 if (leapyear(i))
144 days_in_month(FEBRUARY) = 29;
145 for (i = 1; days >= days_in_month(i); i++)
146 days -= days_in_month(i);
147 dt->dt_mon = i;
148
149 /* Days are what is left over (+1) from all that. */
150 dt->dt_day = days + 1;
151
152 /* Hours, minutes, seconds are easy */
153 dt->dt_hour = rsec / 3600;
154 rsec = rsec % 3600;
155 dt->dt_min = rsec / 60;
156 rsec = rsec % 60;
157 dt->dt_sec = rsec;
158 }