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clock_subr.c revision 1.1 
      1 /*	$NetBSD: clock_subr.c,v 1.1 1997/02/19 23:29:28 gwr Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988 University of Utah.
      5  * Copyright (c) 1982, 1990, 1993
      6  *	The Regents of the University of California.  All rights reserved.
      7  *
      8  * This code is derived from software contributed to Berkeley by
      9  * the Systems Programming Group of the University of Utah Computer
     10  * Science Department.
     11  *
     12  * Redistribution and use in source and binary forms, with or without
     13  * modification, are permitted provided that the following conditions
     14  * are met:
     15  * 1. Redistributions of source code must retain the above copyright
     16  *    notice, this list of conditions and the following disclaimer.
     17  * 2. Redistributions in binary form must reproduce the above copyright
     18  *    notice, this list of conditions and the following disclaimer in the
     19  *    documentation and/or other materials provided with the distribution.
     20  * 3. All advertising materials mentioning features or use of this software
     21  *    must display the following acknowledgement:
     22  *	This product includes software developed by the University of
     23  *	California, Berkeley and its contributors.
     24  * 4. Neither the name of the University nor the names of its contributors
     25  *    may be used to endorse or promote products derived from this software
     26  *    without specific prior written permission.
     27  *
     28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     38  * SUCH DAMAGE.
     39  *
     40  * from: Utah $Hdr: clock.c 1.18 91/01/21$
     41  *
     42  *	@(#)clock.c	8.2 (Berkeley) 1/12/94
     43  */
     44 
     45 /*
     46  * Generic routines to convert between a POSIX date
     47  * (seconds since 1/1/1970) and yr/mo/day/hr/min/sec
     48  * Derived from arch/hp300/hp300/clock.c
     49  */
     50 
     51 #include <sys/types.h>
     52 #include <sys/systm.h>
     53 
     54 #include <dev/clock_subr.h>
     55 
     56 /* Traditional POSIX base year */
     57 #define	POSIX_BASE_YEAR	1970
     58 
     59 static inline int leapyear __P((int year));
     60 #define FEBRUARY	2
     61 #define	days_in_year(a) 	(leapyear(a) ? 366 : 365)
     62 #define	days_in_month(a) 	(month_days[(a) - 1])
     63 
     64 static const int month_days[12] = {
     65 	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
     66 };
     67 
     68 /* Use an inline to make the logic more obvious. */
     69 static inline int
     70 leapyear(year)
     71 	int year;
     72 {
     73 	int rv = 0;
     74 
     75 	if ((year % 4) == 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(dt)
     88 	struct clock_ymdhms *dt;
     89 {
     90 	time_t secs;
     91 	int i, year, days;
     92 
     93 	year = dt->dt_year;
     94 
     95 	/*
     96 	 * Compute days since start of time
     97 	 * First from years, then from months.
     98 	 */
     99 	days = 0;
    100 	for (i = POSIX_BASE_YEAR; i < year; i++)
    101 		days += days_in_year(i);
    102 	if (leapyear(year) && dt->dt_mon > FEBRUARY)
    103 		days++;
    104 
    105 	/* Months */
    106 	for (i = 1; i < dt->dt_mon; i++)
    107 	  	days += days_in_month(i);
    108 	days += (dt->dt_day - 1);
    109 
    110 	/* Add hours, minutes, seconds. */
    111 	secs = ((days
    112 	    * 24 + dt->dt_hour)
    113 	    * 60 + dt->dt_min)
    114 	    * 60 + dt->dt_sec;
    115 
    116 	return (secs);
    117 }
    118 
    119 /* This function uses a copy of month_days[] */
    120 #undef	days_in_month
    121 #define	days_in_month(a) 	(mthdays[(a) - 1])
    122 
    123 void
    124 clock_secs_to_ymdhms(secs, dt)
    125 	time_t secs;
    126 	struct clock_ymdhms *dt;
    127 {
    128 	int mthdays[12];
    129 	int i, days;
    130 	int rsec;	/* remainder seconds */
    131 
    132 	bcopy(month_days, mthdays, sizeof(mthdays));
    133 
    134 	days = secs / SECDAY;
    135 	rsec = secs % SECDAY;
    136 
    137 	/* Day of week (Note: 1/1/1970 was a Thursday) */
    138 	dt->dt_wday = (days + 4) % 7;
    139 
    140 	/* Subtract out whole years, counting them in i. */
    141 	for (i = POSIX_BASE_YEAR; days >= days_in_year(i); i++)
    142 		days -= days_in_year(i);
    143 	dt->dt_year = i;
    144 
    145 	/* Subtract out whole months, counting them in i. */
    146 	if (leapyear(i))
    147 		days_in_month(FEBRUARY) = 29;
    148 	for (i = 1; days >= days_in_month(i); i++)
    149 		days -= days_in_month(i);
    150 	dt->dt_mon = i;
    151 
    152 	/* Days are what is left over (+1) from all that. */
    153 	dt->dt_day = days + 1;
    154 
    155 	/* Hours, minutes, seconds are easy */
    156 	dt->dt_hour = rsec / 3600;
    157 	rsec = rsec % 3600;
    158 	dt->dt_min  = rsec / 60;
    159 	rsec = rsec % 60;
    160 	dt->dt_sec  = rsec;
    161 }
    162