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 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 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 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