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/*
* Stolen from Jef Poskanzer's tws time library, which was stolen from
* Marshall Rose's MH Message Handling system...
*
* tmclock() will convert time from a tm struct back to a clock value.
* tmjuliandate() converts a tm struct to its julian day number.
* tmsubdayclock() takes hours, minutes, and seconds from a tm struct
* and returns the number of seconds since midnight of that day. (?)
* -- Howard Chu, August 1 1988 hyc@umix.cc.umich.edu, umix!hyc
*/
/* $Header: tmclock.c,v 1.2 88/08/01 14:34:38 hyc Exp $ */
/* Julian day number of the Unix* clock's origin, 01 Jan 1970. */
#define JD1970 2440587L
#define CENTURY 19
#if BSD
#include <sys/time.h>
int daylight;
long timezone;
#else
#include <time.h>
#endif
long
tmjuliandate( tm )
struct tm *tm;
{
register int mday, mon, year;
register long a, b;
double jd;
if ( (mday = tm -> tm_mday) < 1 || mday > 31 ||
(mon = tm -> tm_mon + 1) < 1 || mon > 12 ||
(year = tm -> tm_year) < 1 || year > 10000 )
return ( -1L );
if ( year < 100 )
year += CENTURY * 100;
if ( mon == 1 || mon == 2 )
{
--year;
mon += 12;
}
if ( year < 1583 )
return ( -1L );
a = year / 100;
b = 2 - a + a / 4;
b += (long) ( (double) year * 365.25 );
b += (long) ( 30.6001 * ( (double) mon + 1.0 ) );
jd = mday + b + 1720994.5;
return ( (long) jd );
}
long
tmsubdayclock( tm )
struct tm *tm;
{
register int sec, min, hour;
register long result;
#if BSD
{
struct timeval tp;
struct timezone tzp;
gettimeofday(&tp, &tzp);
daylight=tzp.tz_dsttime;
timezone=tzp.tz_minuteswest*(-60);
}
#endif
if ( (sec = tm -> tm_sec) < 0 || sec > 59 ||
(min = tm -> tm_min) < 0 || min > 59 ||
(hour = tm -> tm_hour) < 0 || hour > 23 )
return ( -1L );
result = ( hour * 60 + min ) * 60 + sec;
result -= timezone;
if ( daylight )
result -= 60 * 60;
return ( result );
}
long
tmclock( tm )
struct tm *tm;
{
register long jd, sdc, result;
if ( ( jd = tmjuliandate( tm ) ) == -1L )
return ( -1L );
if ( ( sdc = tmsubdayclock( tm ) ) == -1L )
return ( -1L );
result = ( jd - JD1970 ) * 24 * 60 * 60 + sdc;
return ( result );
}
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