datetime.c

T-kernel 的extension源代码

/*
 *----------------------------------------------------------------------
 *    T-Kernel / Standard Extension
 *
 *    Copyright (C) 2006 by Ken Sakamura. All rights reserved.
 *    T-Kernel / Standard Extension is distributed 
 *      under the T-License for T-Kernel / Standard Extension.
 *----------------------------------------------------------------------
 *
 *    Version:   1.00.00
 *    Released by T-Engine Forum(http://www.t-engine.org) at 2006/8/11.
 *
 *----------------------------------------------------------------------
 */

/*
 *	datetime.c (libg)
 *
 *	System time STIME
 *	Unit		sec
 *	Reference time/date	1/1/1985 00:00:00
 *	No. of valid years	To 2053 or so
 *	No. of valid seconds	0x00000000  -  0x7fffffff
 *	To allow for time correction based on TIMEZONE, the range of STIME shown below
 *	includes the previous and following days:
 *	0x00000000-24*60*60  -  0x7fffffff+24*60*60
 *
 *	Within the valid range of system time, a leap year simply comes once every four years.
 *	(Year 2000 is a leap year.)
 *
 *	   January 1985
 *	 S  M Tu  W Th  F  S
 *	       1  2  3  4  5
 *	 6  7  8  9 10 11 12
 *	13 14 15 16 17 18 19
 *	20 21 22 23 24 25 26
 *	27 28 29 30 31
 */

#include <basic.h>
#include <extension/datetime.h>
#include <libstr.h>
#include <stdlib.h>
#include <sys/util.h>

/* Number of days in four years */
#define	FourYear	( 365 + 365 + 365 + 366 )

/* Number of days in each month (except for leap year) */
LOCAL const H	Days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

/* Day of week (Count days starting on 1/1/1985) */
#define	weekday(day)	( ((day) + 2) % 7 )

/*
 * Conversion from calendar date to total number of seconds
 *	Convertible from 12/31/1984 00:00:00 onward
 *	The result is undefined outside the convertible range or in case of parameter error.
 */
EXPORT void DATEtoTIME( STIME *time, DATE_TIM *date )
{
	div_t	d;
	STIME	t;
	W	day, i;

	if (( date->d_year == 84 )
	  && ( ((date->d_month ==  0 )&&( date->d_days == 366))
	    || ((date->d_month == 12 )&&( date->d_day  ==  31)) ) ) {
		/* December 31, 1984 */
		t = date->d_hour;
		t = (t * 60) + date->d_min;
		t = (t * 60) + date->d_sec;
		*time = t - (24*60*60);
		return;
	}

	d = div(date->d_year - 85, 4);
	day = d.quot * FourYear + d.rem * 365;		/* year -> day */

	if ( date->d_month == 0 ) {
		day += date->d_days - 1;
	} else {
		for ( i = date->d_month - 2; i >= 0; i-- ) {
			if (( i == 1 )&&( d.rem == 3 )) {
				/* February in a leap year */
				day += 29;
			} else {
				day += Days[i];
			}
		}
		day += date->d_day - 1;
	}

	t = (day * 24) + date->d_hour;			/* day -> hour */
	t = (t * 60) + date->d_min;			/* hour -> minute */
	t = (W)(((UW)t * 60U) + (UW)date->d_sec);	/* minute -> second */

	*time = t;
}

/*
 * Conversion from total number of seconds to calendar date
 *	Valid range of time: 0x00000000-24*60*60  -  0x7fffffff+24*60*60
 *	The result is undefined outside the valid range.
 */
EXPORT void TIMEtoDATE( DATE_TIM *date, STIME time )
{
	div_t	d;
	W	day, i;

	if (( time < 0 )&&( time >= -24*60*60 )) {
		/* December 31, 1984 */
		d = div(time + (24*60*60), 60);
		date->d_sec   = d.rem;
		d = div(d.quot, 60);
		date->d_min   = d.rem;
		date->d_hour  = d.quot;
		date->d_year  = 84;
		date->d_month = 12;
		date->d_day   = 31;
		date->d_week  = 53;
		date->d_wday  = 1;
		date->d_days  = 366;
		return;
	}

	date->d_sec = (W)((UW)time % 60U);		/* Second */
	d = div((W)((UW)time / 60U), 60);
	date->d_min = d.rem;				/* Minute */
	d = div(d.quot, 24);
	date->d_hour = d.rem;				/* Hour */

	day = d.quot;					/* Total number of days */
	date->d_wday = weekday(day);			/* Day of week */

	d = div(day, FourYear);
	date->d_year = 85 + (d.quot * 4);
	d = div(d.rem, 365);
	if ( d.quot > 3 ) {
		d.quot--;
		d.rem += 365;
	}
	date->d_year += d.quot;				/* Year */
	date->d_days = d.rem + 1;			/* Number of days */

	i = weekday(day - d.rem);			/* Day of week on Jan. 1 of that year */
	date->d_week = ((d.rem + i) / 7) + 1;		/* Week */

	day = d.rem;
	for ( i = 0; i < 12; i++ ) {
		if (( i == 1 )&&( d.quot == 3 )) {
			/* February in a leap year */
			if ( day < 29 ) {
				break;
			}
			day -= 29;
		} else {
			if ( day < Days[i] ) {
				break;
			}
			day -= Days[i];
		}
	}
	date->d_month = i + 1;				/* Month */
	date->d_day = day + 1;				/* Day */
}