/* * Copyright (C) 1993, 1994, 1995, 1996, 1997 Free Software Foundation, Inc. * This file is part of the GNU C Library. * Contributed by Paul Eggert (eggert@twinsun.com). * * The GNU C Library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * The GNU C Library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with the GNU C Library; see the file COPYING.LIB.  If not, * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. */ /* * Converts the calendar time to broken-down time representation * Based on code from glibc-2.6 * * 2009-7-14: *   Moved from glibc-2.6 to kernel by Zhaolei<zhaolei@cn.fujitsu.com> */ #include <linux/time.h>#include <linux/module.h> /* * Nonzero if YEAR is a leap year (every 4 years, * except every 100th isn't, and every 400th is). */static int __isleap(long year){	return (year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0);} /* do a mathdiv for long type */static long math_div(long a, long b){	return a / b - (a % b < 0);} /* How many leap years between y1 and y2, y1 must less or equal to y2 */static long leaps_between(long y1, long y2){	long leaps1 = math_div(y1 - 1, 4) - math_div(y1 - 1, 100)		+ math_div(y1 - 1, 400);	long leaps2 = math_div(y2 - 1, 4) - math_div(y2 - 1, 100)		+ math_div(y2 - 1, 400);	return leaps2 - leaps1;} /* How many days come before each month (0-12). */static const unsigned short __mon_yday[2][13] = {	/* Normal years. */	{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},	/* Leap years. */	{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}}; #define SECS_PER_HOUR	(60 * 60)#define SECS_PER_DAY	(SECS_PER_HOUR * 24) /** * time_to_tm - converts the calendar time to local broken-down time * * @totalsecs	the number of seconds elapsed since 00:00:00 on January 1, 1970, *		Coordinated Universal Time (UTC). * @offset	offset seconds adding to totalsecs. * @result	pointer to struct tm variable to receive broken-down time */void time_to_tm(time_t totalsecs, int offset, struct tm *result){	long days, rem, y;	const unsigned short *ip; 	days = totalsecs / SECS_PER_DAY;	rem = totalsecs % SECS_PER_DAY;	rem += offset;	while (rem < 0) {		rem += SECS_PER_DAY;		--days;	}	while (rem >= SECS_PER_DAY) {		rem -= SECS_PER_DAY;		++days;	} 	result->tm_hour = rem / SECS_PER_HOUR;	rem %= SECS_PER_HOUR;	result->tm_min = rem / 60;	result->tm_sec = rem % 60; 	/* January 1, 1970 was a Thursday. */	result->tm_wday = (4 + days) % 7;	if (result->tm_wday < 0)		result->tm_wday += 7; 	y = 1970; 	while (days < 0 || days >= (__isleap(y) ? 366 : 365)) {		/* Guess a corrected year, assuming 365 days per year. */		long yg = y + math_div(days, 365); 		/* Adjust DAYS and Y to match the guessed year. */		days -= (yg - y) * 365 + leaps_between(y, yg);		y = yg;	} 	result->tm_year = y - 1900; 	result->tm_yday = days; 	ip = __mon_yday[__isleap(y)];	for (y = 11; days < ip[y]; y--)		continue;	days -= ip[y]; 	result->tm_mon = y;	result->tm_mday = days + 1;}EXPORT_SYMBOL(time_to_tm);