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/******************************************************************************
* time.c
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <xen/config.h>
#include <xen/time.h>
/* Nonzero if YEAR is a leap year (every 4 years,
except every 100th isn't, and every 400th is). */
#define __isleap(year) \
((year) % 4 == 0 && ((year) % 100 != 0 || (year) % 400 == 0))
/* How many days are in each month. */
const unsigned short int __mon_lengths[2][12] = {
/* Normal years. */
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
/* Leap years. */
{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
#define SECS_PER_HOUR (60 * 60)
#define SECS_PER_DAY (SECS_PER_HOUR * 24)
struct tm gmtime(unsigned long t)
{
struct tm tbuf;
long days, rem;
int y;
const unsigned short int *ip;
y = 1970;
#if BITS_PER_LONG >= 64
/* Allow the concept of time before 1970. 64-bit only; for 32-bit
* time after 2038 seems more important than time before 1970. */
while ( t & (1UL<<39) )
{
y -= 400;
t += ((unsigned long)(365 * 303 + 366 * 97)) * SECS_PER_DAY;
}
t &= (1UL << 40) - 1;
#endif
days = t / SECS_PER_DAY;
rem = t % SECS_PER_DAY;
tbuf.tm_hour = rem / SECS_PER_HOUR;
rem %= SECS_PER_HOUR;
tbuf.tm_min = rem / 60;
tbuf.tm_sec = rem % 60;
/* January 1, 1970 was a Thursday. */
tbuf.tm_wday = (4 + days) % 7;
if ( tbuf.tm_wday < 0 )
tbuf.tm_wday += 7;
while ( days >= (rem = __isleap(y) ? 366 : 365) )
{
++y;
days -= rem;
}
while ( days < 0 )
{
--y;
days += __isleap(y) ? 366 : 365;
}
tbuf.tm_year = y - 1900;
tbuf.tm_yday = days;
ip = (const unsigned short int *)__mon_lengths[__isleap(y)];
for ( y = 0; days >= ip[y]; ++y )
days -= ip[y];
tbuf.tm_mon = y;
tbuf.tm_mday = days + 1;
tbuf.tm_isdst = -1;
return tbuf;
}
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