time: add function to convert between calendar time and broken-down time for universal use

struct tms;

extern void do_sys_times(struct tms *);

/*

 * Similar to the struct tm in userspace <time.h>, but it needs to be here so

 * that the kernel source is self contained.

 */

struct tm {

	/*

	 * the number of seconds after the minute, normally in the range

	 * 0 to 59, but can be up to 60 to allow for leap seconds

	 */

	int tm_sec;

	/* the number of minutes after the hour, in the range 0 to 59*/

	int tm_min;

	/* the number of hours past midnight, in the range 0 to 23 */

	int tm_hour;

	/* the day of the month, in the range 1 to 31 */

	int tm_mday;

	/* the number of months since January, in the range 0 to 11 */

	int tm_mon;

	/* the number of years since 1900 */

	long tm_year;

	/* the number of days since Sunday, in the range 0 to 6 */

	int tm_wday;

	/* the number of days since January 1, in the range 0 to 365 */

	int tm_yday;

};

void time_to_tm(time_t totalsecs, int offset, struct tm *result);

/**

 * timespec_to_ns - Convert timespec to nanoseconds

 * @ts:		pointer to the timespec variable to be converted

obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o

obj-y += timekeeping.o ntp.o clocksource.o jiffies.o timer_list.o timecompare.o timeconv.o

obj-$(CONFIG_GENERIC_CLOCKEVENTS_BUILD)		+= clockevents.o

obj-$(CONFIG_GENERIC_CLOCKEVENTS)		+= tick-common.o

/*

 * 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);