/******************************************************************************

 * 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, see <http://www.gnu.org/licenses/>.

 */

#include <xen/sched.h>

#include <xen/shared.h>

#include <xen/spinlock.h>

#include <xen/time.h>

#include <asm/div64.h>

#include <asm/domain.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)

static uint64_t wc_sec; /* UTC time at last 'time update'. */

static unsigned int wc_nsec;

static DEFINE_SPINLOCK(wc_lock);

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;

}

void update_domain_wallclock_time(struct domain *d)

{

    uint32_t *wc_version;

    uint64_t sec;

    spin_lock(&wc_lock);

    wc_version = &shared_info(d, wc_version);

    *wc_version = version_update_begin(*wc_version);

    smp_wmb();

    sec = wc_sec + d->time_offset_seconds;

    shared_info(d, wc_sec)    = sec;

    shared_info(d, wc_nsec)   = wc_nsec;

#ifdef CONFIG_X86

    if ( likely(!has_32bit_shinfo(d)) )

        d->shared_info->native.wc_sec_hi = sec >> 32;

    else

        d->shared_info->compat.arch.wc_sec_hi = sec >> 32;

#else

    shared_info(d, wc_sec_hi) = sec >> 32;

#endif

    smp_wmb();

    *wc_version = version_update_end(*wc_version);

    spin_unlock(&wc_lock);

}

/* Set clock to <secs,usecs> after 00:00:00 UTC, 1 January, 1970. */

void do_settime(u64 secs, unsigned int nsecs, u64 system_time_base)

{

    u64 x;

    u32 y;

    struct domain *d;

    x = SECONDS(secs) + nsecs - system_time_base;

    y = do_div(x, 1000000000);

    spin_lock(&wc_lock);

    wc_sec  = x;

    wc_nsec = y;

    spin_unlock(&wc_lock);

    rcu_read_lock(&domlist_read_lock);

    for_each_domain ( d )

        update_domain_wallclock_time(d);

    rcu_read_unlock(&domlist_read_lock);

}

/* Return secs after 00:00:00 localtime, 1 January, 1970. */

unsigned long get_localtime(struct domain *d)

{

    return wc_sec + (wc_nsec + NOW()) / 1000000000ULL

        + d->time_offset_seconds;

}

/* Return microsecs after 00:00:00 localtime, 1 January, 1970. */

uint64_t get_localtime_us(struct domain *d)

{

    return (SECONDS(wc_sec + d->time_offset_seconds) + wc_nsec + NOW())

           / 1000UL;

}

unsigned long get_sec(void)

{

    return wc_sec + (wc_nsec + NOW()) / 1000000000ULL;

}

struct tm wallclock_time(uint64_t *ns)

{

    uint64_t seconds, nsec;

    if ( !wc_sec )

        return (struct tm) { 0 };

    seconds = NOW() + SECONDS(wc_sec) + wc_nsec;

    nsec = do_div(seconds, 1000000000);

    if ( ns )

        *ns = nsec;

    return gmtime(seconds);

}