/time.c

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

  time.c -

  $Author$
  created at: Tue Dec 28 14:31:59 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto

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

#include "ruby/ruby.h"
#include <sys/types.h>
#include <time.h>
#include <errno.h>
#include "ruby/encoding.h"

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <float.h>
#include <math.h>

#include "timev.h"

#ifndef TYPEOF_TIMEVAL_TV_SEC
# define TYPEOF_TIMEVAL_TV_SEC time_t
#endif
#ifndef TYPEOF_TIMEVAL_TV_USEC
# if INT_MAX >= 1000000
# define TYPEOF_TIMEVAL_TV_USEC int
# else
# define TYPEOF_TIMEVAL_TV_USEC long
# endif
#endif

#if SIZEOF_TIME_T == SIZEOF_LONG
typedef unsigned long unsigned_time_t;
#elif SIZEOF_TIME_T == SIZEOF_INT
typedef unsigned int unsigned_time_t;
#elif SIZEOF_TIME_T == SIZEOF_LONG_LONG
typedef unsigned LONG_LONG unsigned_time_t;
#else
# error cannot find integer type which size is same as time_t.
#endif

#define TIMET_MAX (~(time_t)0 <= 0 ? (time_t)((~(unsigned_time_t)0) >> 1) : (~(unsigned_time_t)0))
#define TIMET_MIN (~(time_t)0 <= 0 ? (time_t)(((unsigned_time_t)1) << (sizeof(time_t) * CHAR_BIT - 1)) : (time_t)0)

VALUE rb_cTime;
static VALUE time_utc_offset _((VALUE));

static int obj2int(VALUE obj);
static VALUE obj2vint(VALUE obj);
static int month_arg(VALUE arg);
static void validate_utc_offset(VALUE utc_offset);
static void validate_vtm(struct vtm *vtm);

static VALUE time_gmtime(VALUE);
static VALUE time_localtime(VALUE);
static VALUE time_fixoff(VALUE);

static time_t timegm_noleapsecond(struct tm *tm);
static int tmcmp(struct tm *a, struct tm *b);
static int vtmcmp(struct vtm *a, struct vtm *b);
static const char *find_time_t(struct tm *tptr, int utc_p, time_t *tp);

static struct vtm *localtimexv(VALUE timexv, struct vtm *result);

static int leap_year_p(long y);
#define leap_year_v_p(y) leap_year_p(NUM2LONG(mod(v, INT2FIX(400))))

#define NDIV(x,y) (-(-((x)+1)/(y))-1)
#define NMOD(x,y) ((y)-(-((x)+1)%(y))-1)
#define DIV(n,d) ((n)<0 ? NDIV((n),(d)) : (n)/(d))

#ifdef HAVE_GMTIME_R
#define IF_HAVE_GMTIME_R(x) x
#define ASCTIME(tm, buf) asctime_r((tm), (buf))
#define GMTIME(tm, result) gmtime_r((tm), &(result))
#define LOCALTIME(tm, result) (tzset(),localtime_r((tm), &(result)))
#else
#define IF_HAVE_GMTIME_R(x) 	/* nothing */
#define ASCTIME(tm, buf) asctime(tm)
#define GMTIME(tm, result) rb_gmtime((tm), &(result))
#define LOCALTIME(tm, result) rb_localtime((tm), &(result))

static inline struct tm *
rb_gmtime(const time_t *tm, struct tm *result)
{
    struct tm *t = gmtime(tm);
    if (t) *result = *t;
    return t;
}

static inline struct tm *
rb_localtime(const time_t *tm, struct tm *result)
{
    struct tm *t = localtime(tm);
    if (t) *result = *t;
    return t;
}
#endif

static ID id_divmod, id_mul, id_submicro, id_nano_num, id_nano_den, id_offset;
static ID id_eq, id_ne, id_quo, id_div, id_cmp, id_lshift;

#define eq(x,y) (RTEST(rb_funcall((x), id_eq, 1, (y))))
#define ne(x,y) (RTEST(rb_funcall((x), id_ne, 1, (y))))
#define lt(x,y) (RTEST(rb_funcall((x), '<', 1, (y))))
#define gt(x,y) (RTEST(rb_funcall((x), '>', 1, (y))))
#define le(x,y) (!gt(x,y))
#define ge(x,y) (!lt(x,y))

static VALUE
add(VALUE x, VALUE y)
{
    if (FIXNUM_P(x) && FIXNUM_P(y)) {
        long l = FIX2LONG(x) + FIX2LONG(y);
        if (FIXABLE(l)) return LONG2FIX(l);
        return LONG2NUM(l);
    }
    if (TYPE(x) == T_BIGNUM) return rb_big_plus(x, y);
    return rb_funcall(x, '+', 1, y);
}

static VALUE
sub(VALUE x, VALUE y)
{
    if (FIXNUM_P(x) && FIXNUM_P(y)) {
        long l = FIX2LONG(x) - FIX2LONG(y);
        if (FIXABLE(l)) return LONG2FIX(l);
        return LONG2NUM(l);
    }
    if (TYPE(x) == T_BIGNUM) return rb_big_minus(x, y);
    return rb_funcall(x, '-', 1, y);
}

static VALUE
mul(VALUE x, VALUE y)
{
    if (FIXNUM_P(x) && FIXNUM_P(y)) {
#if HAVE_LONG_LONG && SIZEOF_LONG * 2 <= SIZEOF_LONG_LONG 
        LONG_LONG ll = (LONG_LONG)FIX2LONG(x) * FIX2LONG(y);
        if (FIXABLE(ll)) return LONG2FIX(ll);
        return LL2NUM(ll);
#else
        long a, b, c;
        a = FIX2LONG(x);
        if (a == 0) return x;
        b = FIX2LONG(y);
        c = a * b;
        if (c / a == b && FIXABLE(c)) return LONG2FIX(c);
#endif
    }
    if (TYPE(x) == T_BIGNUM) return rb_big_mul(x, y);
    return rb_funcall(x, '*', 1, y);
}

#define div(x,y) (rb_funcall((x), id_div, 1, (y)))

static VALUE
mod(VALUE x, VALUE y)
{
    switch (TYPE(x)) {
      case T_BIGNUM: return rb_big_modulo(x, y);
      default: return rb_funcall(x, '%', 1, y);
    }
}

#define neg(x) (sub(INT2FIX(0), (x)))
#define cmp(x,y) (rb_funcall((x), id_cmp, 1, (y)))
#define lshift(x,y) (rb_funcall((x), id_lshift, 1, (y)))

static VALUE
quo(VALUE x, VALUE y)
{
    VALUE ret;
    ret = rb_funcall((x), id_quo, 1, (y));
    if (TYPE(ret) == T_RATIONAL &&
        RRATIONAL(ret)->den == INT2FIX(1)) {
        ret = RRATIONAL(ret)->num;
    }
    return ret;
}

#define mulquo(x,y,z) ((y == z) ? x : quo(mul(x,y),z))

static void
divmodv(VALUE n, VALUE d, VALUE *q, VALUE *r)
{
    VALUE tmp, ary;
    tmp = rb_funcall(n, id_divmod, 1, d);
    ary = rb_check_array_type(tmp);
    if (NIL_P(ary)) {
        rb_raise(rb_eTypeError, "unexpected divmod result: into %s",
                 rb_obj_classname(tmp));
    }
    *q = rb_ary_entry(ary, 0);
    *r = rb_ary_entry(ary, 1);
}

static VALUE
num_exact(VALUE v)
{
    switch (TYPE(v)) {
      case T_FIXNUM:
      case T_BIGNUM:
      case T_RATIONAL:
        break;

      case T_FLOAT:
        v = rb_convert_type(v, T_RATIONAL, "Rational", "to_r");
        break;

      case T_STRING:
      case T_NIL:
        goto typeerror;

      default: {
        VALUE tmp;
        if (!NIL_P(tmp = rb_check_convert_type(v, T_RATIONAL, "Rational", "to_r"))) {
	    if (rb_respond_to(v, rb_intern("to_str"))) goto typeerror;
            v = tmp;
	}
        else if (!NIL_P(tmp = rb_check_to_integer(v, "to_int")))
            v = tmp;
        else {
          typeerror:
            rb_raise(rb_eTypeError, "can't convert %s into an exact number",
		                    NIL_P(v) ? "nil" : rb_obj_classname(v));
        }
        break;
      }
    }
    return v;
}

static VALUE
rb_time_magnify(VALUE v)
{
    return mul(v, INT2FIX(TIME_SCALE));
}

static VALUE
rb_time_unmagnify(VALUE v)
{
    return quo(v, INT2FIX(TIME_SCALE));
}

static const int common_year_yday_offset[] = {
    -1,
    -1 + 31,
    -1 + 31 + 28,
    -1 + 31 + 28 + 31,
    -1 + 31 + 28 + 31 + 30,
    -1 + 31 + 28 + 31 + 30 + 31,
    -1 + 31 + 28 + 31 + 30 + 31 + 30,
    -1 + 31 + 28 + 31 + 30 + 31 + 30 + 31,
    -1 + 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31,
    -1 + 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
    -1 + 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
    -1 + 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30
      /* 1    2    3    4    5    6    7    8    9    10   11 */
};
static const int leap_year_yday_offset[] = {
    -1,
    -1 + 31,
    -1 + 31 + 29,
    -1 + 31 + 29 + 31,
    -1 + 31 + 29 + 31 + 30,
    -1 + 31 + 29 + 31 + 30 + 31,
    -1 + 31 + 29 + 31 + 30 + 31 + 30,
    -1 + 31 + 29 + 31 + 30 + 31 + 30 + 31,
    -1 + 31 + 29 + 31 + 30 + 31 + 30 + 31 + 31,
    -1 + 31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
    -1 + 31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
    -1 + 31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30
      /* 1    2    3    4    5    6    7    8    9    10   11 */
};

static const int common_year_days_in_month[] = {
    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
static const int leap_year_days_in_month[] = {
    31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

static VALUE
timegmxv_noleapsecond(struct vtm *vtm)
{
    VALUE year1900;
    VALUE q400, r400;
    int year_mod400;
    int yday = vtm->mday;
    long days_in400;
    VALUE ret;

    year1900 = sub(vtm->year, INT2FIX(1900));

    divmodv(year1900, INT2FIX(400), &q400, &r400);
    year_mod400 = NUM2INT(r400);

    if (leap_year_p(year_mod400 + 1900))
	yday += leap_year_yday_offset[vtm->mon-1];
    else
	yday += common_year_yday_offset[vtm->mon-1];

    /*
     *  `Seconds Since the Epoch' in SUSv3:
     *  tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
     *  (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
     *  ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
     */
    ret = LONG2NUM(vtm->sec
                 + vtm->min*60
                 + vtm->hour*3600);
    days_in400 = yday
               - 70*365
               + DIV(year_mod400 - 69, 4)
               - DIV(year_mod400 - 1, 100)
               + (year_mod400 + 299) / 400;
    ret = add(ret, mul(LONG2NUM(days_in400), INT2FIX(86400)));
    ret = add(ret, mul(q400, INT2FIX(97*86400)));
    ret = add(ret, mul(year1900, INT2FIX(365*86400)));
    ret = add(rb_time_magnify(ret), vtm->subsecx);

    return ret;
}

static st_table *zone_table;

static const char *
zone_str(const char *s)
{
    st_data_t k, v;

    if (!zone_table)
        zone_table = st_init_strtable();

    k = (st_data_t)s;
    if (st_lookup(zone_table, k, &v)) {
        return (const char *)v;
    }
    s = strdup(s);
    k = (st_data_t)s;
    st_add_direct(zone_table, k, k);

    return s;
}

static void
gmtimexv_noleapsecond(VALUE timexv, struct vtm *vtm)
{
    VALUE v;
    int i, n, x, y;
    const int *yday_offset;
    int wday;
    VALUE timev;

    vtm->isdst = 0;

    divmodv(timexv, INT2FIX(TIME_SCALE), &timev, &vtm->subsecx);
    divmodv(timev, INT2FIX(86400), &timev, &v);

    wday = NUM2INT(mod(timev, INT2FIX(7)));
    vtm->wday = (wday + 4) % 7;

    n = NUM2INT(v);
    vtm->sec = n % 60; n = n / 60;
    vtm->min = n % 60; n = n / 60;
    vtm->hour = n;

    /* 97 leap days in the 400 year cycle */
    divmodv(timev, INT2FIX(400*365 + 97), &timev, &v);
    vtm->year = mul(timev, INT2FIX(400));

    /* n is the days in the 400 year cycle.
     * the start of the cycle is 1970-01-01. */

    n = NUM2INT(v);
    y = 1970;

    /* 30 years including 7 leap days (1972, 1976, ... 1996),
     * 31 days in January 2000 and
     * 29 days in February 2000
     * from 1970-01-01 to 2000-02-29 */
    if (30*365+7+31+29-1 <= n) {
        /* 2000-02-29 or after */
        if (n < 31*365+8) {
            /* 2000-02-29 to 2000-12-31 */
            y += 30;
            n -= 30*365+7;
            goto found;
        }
        else {
            /* 2001-01-01 or after */
            n -= 1;
        }
    }

    x = n / (365*100 + 24);
    n = n % (365*100 + 24);
    y += x * 100;
    if (30*365+7+31+29-1 <= n) {
        if (n < 31*365+7) {
            y += 30;
            n -= 30*365+7;
            goto found;
        }
        else
            n += 1;
    }

    x = n / (365*4 + 1);
    n = n % (365*4 + 1);
    y += x * 4;
    if (365*2+31+29-1 <= n) {
        if (n < 365*2+366) {
            y += 2;
            n -= 365*2;
            goto found;
        }
        else
            n -= 1;
    }

    x = n / 365;
    n = n % 365;
    y += x;

  found:
    vtm->yday = n+1;
    vtm->year = add(vtm->year, INT2NUM(y));

    if (leap_year_p(y))
        yday_offset = leap_year_yday_offset;
    else
        yday_offset = common_year_yday_offset;

    for (i = 0; i < 12; i++) {
        if (yday_offset[i] < n) {
            vtm->mon = i+1;
            vtm->mday = n - yday_offset[i];
        }
        else
            break;
    }

    vtm->utc_offset = INT2FIX(0);
    vtm->zone = "UTC";
}

static struct tm *
gmtime_with_leapsecond(const time_t *timep, struct tm *result)
{
#if defined(HAVE_STRUCT_TM_TM_GMTOFF)
    /* 4.4BSD counts leap seconds only with localtime, not with gmtime. */
    struct tm *t;
    int sign;
    int gmtoff_sec, gmtoff_min, gmtoff_hour, gmtoff_day;
    long gmtoff;
    t = localtime_r(timep, result);
    if (t == NULL)
        return NULL;

    /* subtract gmtoff */
    if (t->tm_gmtoff < 0) {
        sign = 1;
        gmtoff = -t->tm_gmtoff;
    }
    else {
        sign = -1;
        gmtoff = t->tm_gmtoff;
    }
    gmtoff_sec = (int)(gmtoff % 60);
    gmtoff = gmtoff / 60;
    gmtoff_min = (int)(gmtoff % 60);
    gmtoff = gmtoff / 60;
    gmtoff_hour = (int)gmtoff;	/* <= 12 */

    gmtoff_sec *= sign;
    gmtoff_min *= sign;
    gmtoff_hour *= sign;

    gmtoff_day = 0;

    if (gmtoff_sec) {
        /* If gmtoff_sec == 0, don't change result->tm_sec.
         * It may be 60 which is a leap second. */
        result->tm_sec += gmtoff_sec;
        if (result->tm_sec < 0) {
            result->tm_sec += 60;
            gmtoff_min -= 1;
        }
        if (60 <= result->tm_sec) {
            result->tm_sec -= 60;
            gmtoff_min += 1;
        }
    }
    if (gmtoff_min) {
        result->tm_min += gmtoff_min;
        if (result->tm_min < 0) {
            result->tm_min += 60;
            gmtoff_hour -= 1;
        }
        if (60 <= result->tm_min) {
            result->tm_min -= 60;
            gmtoff_hour += 1;
        }
    }
    if (gmtoff_hour) {
        result->tm_hour += gmtoff_hour;
        if (result->tm_hour < 0) {
            result->tm_hour += 24;
            gmtoff_day = -1;
        }
        if (24 <= result->tm_hour) {
            result->tm_hour -= 24;
            gmtoff_day = 1;
        }
    }

    if (gmtoff_day) {
        if (gmtoff_day < 0) {
            if (result->tm_yday == 0) {
                result->tm_mday = 31;
                result->tm_mon = 11; /* December */
                result->tm_year--;
                result->tm_yday = leap_year_p(result->tm_year + 1900) ? 365 : 364;
            }
            else if (result->tm_mday == 1) {
                const int *days_in_month = leap_year_p(result->tm_year + 1900) ?
                                           leap_year_days_in_month :
                                           common_year_days_in_month;
                result->tm_mon--;
                result->tm_mday = days_in_month[result->tm_mon];
                result->tm_yday--;
            }
            else {
                result->tm_mday--;
                result->tm_yday--;
            }
            result->tm_wday = (result->tm_wday + 6) % 7;
        }
        else {
            int leap = leap_year_p(result->tm_year + 1900);
            if (result->tm_yday == (leap ? 365 : 364)) {
                result->tm_year++;
                result->tm_mon = 0; /* January */
                result->tm_mday = 1;
                result->tm_yday = 0;
            }
            else if (result->tm_mday == (leap ? leap_year_days_in_month :
                                                common_year_days_in_month)[result->tm_mon]) {
                result->tm_mon++;
                result->tm_mday = 1;
                result->tm_yday++;
            }
            else {
                result->tm_mday++;
                result->tm_yday++;
            }
            result->tm_wday = (result->tm_wday + 1) % 7;
        }
    }
    result->tm_isdst = 0;
    result->tm_gmtoff = 0;
#if defined(HAVE_TM_ZONE)
    result->tm_zone = (char *)"UTC";
#endif
    return result;
#else
    return GMTIME(timep, *result);
#endif
}

static long this_year = 0;
static time_t known_leap_seconds_limit;
static int number_of_leap_seconds_known;

static void
init_leap_second_info()
{
    /*
     * leap seconds are determined by IERS.
     * It is announced 6 months before the leap second.
     * So no one knows leap seconds in the future after the next year.
     */
    if (this_year == 0) {
        time_t now;
        struct tm *tm, result;
        struct vtm vtm;
        VALUE timexv;
        now = time(NULL);
        gmtime(&now);
        tm = gmtime_with_leapsecond(&now, &result);
        if (!tm) return;
        this_year = tm->tm_year;

        if (TIMET_MAX - now < (time_t)(366*86400))
            known_leap_seconds_limit = TIMET_MAX;
        else
            known_leap_seconds_limit = now + (time_t)(366*86400);

        gmtime_with_leapsecond(&known_leap_seconds_limit, &result);

        vtm.year = LONG2NUM(result.tm_year + 1900);
        vtm.mon = result.tm_mon + 1;
        vtm.mday = result.tm_mday;
        vtm.hour = result.tm_hour;
        vtm.min = result.tm_min;
        vtm.sec = result.tm_sec;
        vtm.subsecx = INT2FIX(0);
        vtm.utc_offset = INT2FIX(0);

        timexv = timegmxv_noleapsecond(&vtm);

        number_of_leap_seconds_known = NUM2INT(sub(TIMET2NUM(known_leap_seconds_limit), rb_time_unmagnify(timexv)));
    }
}

static VALUE
timegmxv(struct vtm *vtm)
{
    VALUE timexv;
    struct tm tm;
    time_t t;
    const char *errmsg;

    /* The first leap second is 1972-06-30 23:59:60 UTC.
     * No leap seconds before. */
    if (RTEST(gt(INT2FIX(1972), vtm->year)))
        return timegmxv_noleapsecond(vtm);

    init_leap_second_info();

    timexv = timegmxv_noleapsecond(vtm);

    if (RTEST(lt(rb_time_magnify(TIMET2NUM(known_leap_seconds_limit)), timexv))) {
        return add(timexv, rb_time_magnify(INT2NUM(number_of_leap_seconds_known)));
    }

    tm.tm_year = rb_long2int(NUM2LONG(vtm->year) - 1900);
    tm.tm_mon = vtm->mon - 1;
    tm.tm_mday = vtm->mday;
    tm.tm_hour = vtm->hour;
    tm.tm_min = vtm->min;
    tm.tm_sec = vtm->sec;
    tm.tm_isdst = 0;

    errmsg = find_time_t(&tm, 1, &t);
    if (errmsg)
        rb_raise(rb_eArgError, "%s", errmsg);
    return add(rb_time_magnify(TIMET2NUM(t)), vtm->subsecx);
}

static struct vtm *
gmtimexv(VALUE timexv, struct vtm *result)
{
    time_t t;
    struct tm tm;
    VALUE subsecx;
    VALUE timev;

    if (RTEST(lt(timexv, INT2FIX(0)))) {
        gmtimexv_noleapsecond(timexv, result);
        return result;
    }

    init_leap_second_info();

    if (RTEST(lt(rb_time_magnify(LONG2NUM(known_leap_seconds_limit)), timexv))) {
        timexv = sub(timexv, rb_time_magnify(INT2NUM(number_of_leap_seconds_known)));
        gmtimexv_noleapsecond(timexv, result);
        return result;
    }

    divmodv(timexv, INT2FIX(TIME_SCALE), &timev, &subsecx);

    t = NUM2TIMET(timev);
    if (!gmtime_with_leapsecond(&t, &tm))
        return NULL;

    result->year = LONG2NUM((long)tm.tm_year + 1900);
    result->mon = tm.tm_mon + 1;
    result->mday = tm.tm_mday;
    result->hour = tm.tm_hour;
    result->min = tm.tm_min;
    result->sec = tm.tm_sec;
    result->subsecx = subsecx;
    result->utc_offset = INT2FIX(0);
    result->wday = tm.tm_wday;
    result->yday = tm.tm_yday+1;
    result->isdst = tm.tm_isdst;
    result->zone = "UTC";

    return result;
}

static struct tm *localtime_with_gmtoff(const time_t *t, struct tm *result, long *gmtoff);

/*
 * The idea is come from Perl:
 * http://use.perl.org/articles/08/02/07/197204.shtml
 *
 * compat_common_month_table is generated by following program.
 * This table finds the last month which start the same day of a week.
 * The year 2037 is not used because
 * http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=522949
 *
 *  #!/usr/bin/ruby 
 *
 *  require 'date'
 *
 *  h = {}
 *  2036.downto(2010) {|y|
 *    1.upto(12) {|m|
 *      next if m == 2 && y % 4 == 0
 *      d = Date.new(y,m,1)
 *      h[m] ||= {}
 *      h[m][d.wday] ||= y
 *    }   
 *  } 
 *
 *  1.upto(12) {|m|
 *    print "{"
 *    0.upto(6) {|w|
 *      y = h[m][w]
 *      print " #{y},"
 *    }
 *    puts "},"
 *  }
 *
 */
static int compat_common_month_table[12][7] = {
  /* Sun   Mon   Tue   Wed   Thu   Fri   Sat */
  { 2034, 2035, 2036, 2031, 2032, 2027, 2033 }, /* January */
  { 2026, 2027, 2033, 2034, 2035, 2030, 2031 }, /* February */
  { 2026, 2032, 2033, 2034, 2035, 2030, 2036 }, /* March */
  { 2035, 2030, 2036, 2026, 2032, 2033, 2034 }, /* April */
  { 2033, 2034, 2035, 2030, 2036, 2026, 2032 }, /* May */
  { 2036, 2026, 2032, 2033, 2034, 2035, 2030 }, /* June */
  { 2035, 2030, 2036, 2026, 2032, 2033, 2034 }, /* July */
  { 2032, 2033, 2034, 2035, 2030, 2036, 2026 }, /* August */
  { 2030, 2036, 2026, 2032, 2033, 2034, 2035 }, /* September */
  { 2034, 2035, 2030, 2036, 2026, 2032, 2033 }, /* October */
  { 2026, 2032, 2033, 2034, 2035, 2030, 2036 }, /* November */
  { 2030, 2036, 2026, 2032, 2033, 2034, 2035 }, /* December */
};

/*
 * compat_leap_month_table is generated by following program.
 *
 *  #!/usr/bin/ruby 
 * 
 *  require 'date'
 * 
 *  h = {}
 *  2037.downto(2010) {|y|
 *    1.upto(12) {|m|
 *      next unless m == 2 && y % 4 == 0
 *      d = Date.new(y,m,1)
 *      h[m] ||= {}
 *      h[m][d.wday] ||= y
 *    }
 *  }
 * 
 *  2.upto(2) {|m|
 *    0.upto(6) {|w|
 *      y = h[m][w]
 *      print " #{y},"
 *    }
 *    puts
 *  }
 */
static int compat_leap_month_table[7] = {
/* Sun   Mon   Tue   Wed   Thu   Fri   Sat */
  2032, 2016, 2028, 2012, 2024, 2036, 2020, /* February */
};

static int
calc_wday(int year, int month, int day)
{
    int a, y, m;
    int wday;

    a = (14 - month) / 12;
    y = year + 4800 - a;
    m = month + 12 * a - 3;
    wday = day + (153*m+2)/5 + 365*y + y/4 - y/100 + y/400 + 2;
    wday = wday % 7;
    return wday;
}

static VALUE
guess_local_offset(struct vtm *vtm_utc)
{
    VALUE off = INT2FIX(0);
    struct tm tm;
    long gmtoff;
    time_t t;
    struct vtm vtm2;
    VALUE timev;
    int y, wday;

# if defined(NEGATIVE_TIME_T)
    /* 1901-12-13 20:45:52 UTC : The oldest time in 32-bit signed time_t. */
    if (localtime_with_gmtoff((t = (time_t)0x80000000, &t), &tm, &gmtoff))
	off = LONG2FIX(gmtoff);
    else
# endif
    /* 1970-01-01 00:00:00 UTC : The Unix epoch - the oldest time in portable time_t. */
    if (localtime_with_gmtoff((t = 0, &t), &tm, &gmtoff))
	off = LONG2FIX(gmtoff);

    /* The first DST is at 1916 in German.
     * So we don't need to care DST before that. */
    if (lt(vtm_utc->year, INT2FIX(1916)))
        return off;

    /* It is difficult to guess future. */

    vtm2 = *vtm_utc;

    /* guess using a year before 2038. */
    y = NUM2INT(mod(vtm_utc->year, INT2FIX(400)));
    wday = calc_wday(y, vtm_utc->mon, 1);
    if (vtm_utc->mon == 2 && leap_year_p(y))
        vtm2.year = INT2FIX(compat_leap_month_table[wday]);
    else
        vtm2.year = INT2FIX(compat_common_month_table[vtm_utc->mon-1][wday]);

    timev = rb_time_unmagnify(timegmxv(&vtm2));
    t = NUM2TIMET(timev);
    if (localtime_with_gmtoff(&t, &tm, &gmtoff))
        return LONG2FIX(gmtoff);

    {
        /* Use the current time offset as a last resort. */
        static time_t now = 0;
        static long now_gmtoff = 0;
        if (now == 0) {
            now = time(NULL);
            localtime_with_gmtoff(&now, &tm, &now_gmtoff);
        }
        return LONG2FIX(now_gmtoff);
    }
}

static VALUE
small_vtm_sub(struct vtm *vtm1, struct vtm *vtm2)
{
    int off;

    off = vtm1->sec - vtm2->sec;
    off += (vtm1->min - vtm2->min) * 60;
    off += (vtm1->hour - vtm2->hour) * 3600;
    if (ne(vtm1->year, vtm2->year))
        off += lt(vtm1->year, vtm2->year) ? -24*3600 : 24*3600;
    else if (vtm1->mon != vtm2->mon)
        off += vtm1->mon < vtm2->mon ? -24*3600 : 24*3600;
    else if (vtm1->mday != vtm2->mday)
        off += vtm1->mday < vtm2->mday ? -24*3600 : 24*3600;

    return INT2FIX(off);
}

static VALUE
timelocalxv(struct vtm *vtm)
{
    time_t t;
    struct tm tm;
    VALUE v;
    VALUE timexv1, timexv2;
    struct vtm vtm1, vtm2;
    int n;

    if (FIXNUM_P(vtm->year)) {
        long l = FIX2LONG(vtm->year) - 1900;
        if (l < INT_MIN || INT_MAX < l)
            goto no_localtime;
        tm.tm_year = (int)l;
    }
    else {
        v = sub(vtm->year, INT2FIX(1900));
        if (lt(v, INT2NUM(INT_MIN)) || lt(INT2NUM(INT_MAX), v))
            goto no_localtime;
        tm.tm_year = NUM2INT(v);
    }

    tm.tm_mon = vtm->mon-1;
    tm.tm_mday = vtm->mday;
    tm.tm_hour = vtm->hour;
    tm.tm_min = vtm->min;
    tm.tm_sec = vtm->sec;
    tm.tm_isdst = vtm->isdst;

    if (find_time_t(&tm, 0, &t))
        goto no_localtime;
    return add(rb_time_magnify(TIMET2NUM(t)), vtm->subsecx);

  no_localtime:
    timexv1 = timegmxv(vtm);

    if (!localtimexv(timexv1, &vtm1))
        rb_raise(rb_eArgError, "localtimexv error");

    n = vtmcmp(vtm, &vtm1);
    if (n == 0) {
        timexv1 = sub(timexv1, rb_time_magnify(INT2FIX(12*3600)));
        if (!localtimexv(timexv1, &vtm1))
            rb_raise(rb_eArgError, "localtimexv error");
        n = 1;
    }

    if (n < 0) {
        timexv2 = timexv1;
        vtm2 = vtm1;
        timexv1 = sub(timexv1, rb_time_magnify(INT2FIX(24*3600)));
        if (!localtimexv(timexv1, &vtm1))
            rb_raise(rb_eArgError, "localtimexv error");
    }
    else {
        timexv2 = add(timexv1, rb_time_magnify(INT2FIX(24*3600)));
        if (!localtimexv(timexv2, &vtm2))
            rb_raise(rb_eArgError, "localtimexv error");
    }
    timexv1 = add(timexv1, rb_time_magnify(small_vtm_sub(vtm, &vtm1)));
    timexv2 = add(timexv2, rb_time_magnify(small_vtm_sub(vtm, &vtm2)));

    if (eq(timexv1, timexv2))
        return timexv1;

    if (!localtimexv(timexv1, &vtm1))
        rb_raise(rb_eArgError, "localtimexv error");
    if (vtm->hour != vtm1.hour || vtm->min != vtm1.min || vtm->sec != vtm1.sec)
        return timexv2;

    if (!localtimexv(timexv2, &vtm2))
        rb_raise(rb_eArgError, "localtimexv error");
    if (vtm->hour != vtm2.hour || vtm->min != vtm2.min || vtm->sec != vtm2.sec)
        return timexv1;

    if (vtm->isdst)
        return lt(vtm1.utc_offset, vtm2.utc_offset) ? timexv2 : timexv1;
    else
        return lt(vtm1.utc_offset, vtm2.utc_offset) ? timexv1 : timexv2;
}

static struct tm *
localtime_with_gmtoff(const time_t *t, struct tm *result, long *gmtoff)
{
    struct tm tm;

    if (LOCALTIME(t, tm)) {
#if defined(HAVE_STRUCT_TM_TM_GMTOFF)
	*gmtoff = tm.tm_gmtoff;
#else
	struct tm *u, *l;
	long off;
	struct tm tmbuf;
	l = &tm;
	u = GMTIME(t, tmbuf);
	if (!u)
	    return NULL;
	if (l->tm_year != u->tm_year)
	    off = l->tm_year < u->tm_year ? -1 : 1;
	else if (l->tm_mon != u->tm_mon)
	    off = l->tm_mon < u->tm_mon ? -1 : 1;
	else if (l->tm_mday != u->tm_mday)
	    off = l->tm_mday < u->tm_mday ? -1 : 1;
	else
	    off = 0;
	off = off * 24 + l->tm_hour - u->tm_hour;
	off = off * 60 + l->tm_min - u->tm_min;
	off = off * 60 + l->tm_sec - u->tm_sec;
	*gmtoff = off;
#endif
        *result = tm;
	return result;
    }
    return NULL;
}

static struct vtm *
localtimexv(VALUE timexv, struct vtm *result)
{
    VALUE timev, subsecx, offset;
    divmodv(timexv, INT2FIX(TIME_SCALE), &timev, &subsecx);

    if (le(TIMET2NUM(TIMET_MIN), timev) &&
        le(timev, TIMET2NUM(TIMET_MAX))) {
        time_t t;
        struct tm tm;
	long gmtoff;
        t = NUM2TIMET(timev);

        if (localtime_with_gmtoff(&t, &tm, &gmtoff)) {
            result->year = LONG2NUM((long)tm.tm_year + 1900);
            result->mon = tm.tm_mon + 1;
            result->mday = tm.tm_mday;
            result->hour = tm.tm_hour;
            result->min = tm.tm_min;
            result->sec = tm.tm_sec;
            result->subsecx = subsecx;
            result->wday = tm.tm_wday;
            result->yday = tm.tm_yday+1;
            result->isdst = tm.tm_isdst;
            result->utc_offset = LONG2NUM(gmtoff);
#if defined(HAVE_TM_ZONE)
            result->zone = zone_str(tm.tm_zone);
#elif defined(HAVE_TZNAME) && defined(HAVE_DAYLIGHT)
            /* this needs tzset or localtime, instead of localtime_r */
            result->zone = zone_str(tzname[daylight && tm.tm_isdst]);
#else
            {
                char buf[64];
                strftime(buf, sizeof(buf), "%Z", &tm);
                result->zone = zone_str(buf);
            }
#endif

            return result;
        }
    }

    if (!gmtimexv(timexv, result))
        return NULL;

    offset = guess_local_offset(result);

    if (!gmtimexv(add(timexv, rb_time_magnify(offset)), result))
        return NULL;

    result->utc_offset = offset;

    return result;
}

struct time_object {
    VALUE timexv; /* time_t value * TIME_SCALE.  possibly Rational. */
    struct vtm vtm;
    int gmt;
    int tm_got;
};

#define GetTimeval(obj, tobj) \
    TypedData_Get_Struct(obj, struct time_object, &time_data_type, tobj)

#define IsTimeval(obj) rb_typeddata_is_kind_of(obj, &time_data_type)

#define TIME_UTC_P(tobj) ((tobj)->gmt == 1)
#define TIME_SET_UTC(tobj) ((tobj)->gmt = 1)

#define TIME_LOCALTIME_P(tobj) ((tobj)->gmt == 0)
#define TIME_SET_LOCALTIME(tobj) ((tobj)->gmt = 0)

#define TIME_FIXOFF_P(tobj) ((tobj)->gmt == 2)
#define TIME_SET_FIXOFF(tobj, off) \
    ((tobj)->gmt = 2, \
     (tobj)->vtm.utc_offset = (off), \
     (tobj)->vtm.zone = NULL)

#define TIME_COPY_GMT(tobj1, tobj2) ((tobj1)->gmt = (tobj2)->gmt)

static VALUE time_get_tm(VALUE, struct time_object *);
#define MAKE_TM(time, tobj) \
  do { \
    if ((tobj)->tm_got == 0) { \
	time_get_tm((time), (tobj)); \
    } \
  } while (0)

static void
time_mark(void *ptr)
{
    struct time_object *tobj = ptr;
    if (!tobj) return;
    rb_gc_mark(tobj->timexv);
    rb_gc_mark(tobj->vtm.year);
    rb_gc_mark(tobj->vtm.subsecx);
    rb_gc_mark(tobj->vtm.utc_offset);
}

static void
time_free(void *tobj)
{
    if (tobj) xfree(tobj);
}

static size_t
time_memsize(const void *tobj)
{
    return tobj ? sizeof(struct time_object) : 0;
}

static const rb_data_type_t time_data_type = {
    "time",
    time_mark, time_free, time_memsize,
};

static VALUE
time_s_alloc(VALUE klass)
{
    VALUE obj;
    struct time_object *tobj;

    obj = TypedData_Make_Struct(klass, struct time_object, &time_data_type, tobj);
    tobj->tm_got=0;
    tobj->timexv = INT2FIX(0);

    return obj;
}

static void
time_modify(VALUE time)
{
    rb_check_frozen(time);
    if (!OBJ_UNTRUSTED(time) && rb_safe_level() >= 4)
	rb_raise(rb_eSecurityError, "Insecure: can't modify Time");
}

static VALUE
timespec2timexv(struct timespec *ts)
{
    VALUE timexv;

    timexv = rb_time_magnify(TIMET2NUM(ts->tv_sec));
    if (ts->tv_nsec)
        timexv = add(timexv, mulquo(LONG2NUM(ts->tv_nsec), INT2FIX(TIME_SCALE), INT2FIX(1000000000)));
    return timexv;
}

static struct timespec
timexv2timespec(VALUE timexv)
{
    VALUE timev, subsecx;
    struct timespec ts;

    divmodv(timexv, INT2FIX(TIME_SCALE), &timev, &subsecx);
    if (lt(timev, TIMET2NUM(TIMET_MIN)) || lt(TIMET2NUM(TIMET_MAX), timev))
	rb_raise(rb_eArgError, "time out of system range");
    ts.tv_sec = NUM2TIMET(timev);
    ts.tv_nsec = NUM2LONG(mulquo(subsecx, INT2FIX(1000000000), INT2FIX(TIME_SCALE)));
    return ts;
}

/*
 *  Document-method: now
 *
 *  Synonym for <code>Time.new</code>. Returns a +Time+ object
 *  initialized to the current system time.
 */

static VALUE
time_init_0(VALUE time)
{
    struct time_object *tobj;
    struct timespec ts;

    time_modify(time);
    GetTimeval(time, tobj);
    tobj->tm_got=0;
    tobj->timexv = INT2FIX(0);
#ifdef HAVE_CLOCK_GETTIME
    if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
	rb_sys_fail("clock_gettime");
    }
#else
    {
        struct timeval tv;
        if (gettimeofday(&tv, 0) < 0) {
            rb_sys_fail("gettimeofday");
        }
        ts.tv_sec = tv.tv_sec;
        ts.tv_nsec = tv.tv_usec * 1000;
    }
#endif
    tobj->timexv = timespec2timexv(&ts);

    return time;
}

static VALUE
time_set_utc_offset(VALUE time, VALUE off)
{
    struct time_object *tobj;
    off = num_exact(off);

    time_modify(time);
    GetTimeval(time, tobj);

    tobj->tm_got = 0;
    TIME_SET_FIXOFF(tobj, off);

    return time;
}

static void
vtm_add_offset(struct vtm *vtm, VALUE off)
{
    int sign;
    VALUE subsec, v;
    int sec, min, hour;
    int day;

    vtm->utc_offset = sub(vtm->utc_offset, off);

    if (RTEST(lt(off, INT2FIX(0)))) {
        sign = -1;
        off = neg(off);
    }
    else {
        sign = 1;
    }
    divmodv(off, INT2FIX(1), &off, &subsec);
    divmodv(off, INT2FIX(60), &off, &v);
    sec = NUM2INT(v);
    divmodv(off, INT2FIX(60), &off, &v);
    min = NUM2INT(v);
    divmodv(off, INT2FIX(24), &off, &v);
    hour = NUM2INT(v);

    if (sign < 0) {
        subsec = neg(subsec);
        sec = -sec;
        min = -min;
        hour = -hour;
    }

    day = 0;

    if (!rb_equal(subsec, INT2FIX(0))) {
        vtm->subsecx = add(vtm->subsecx, rb_time_magnify(subsec));
        if (lt(vtm->subsecx, INT2FIX(0))) {
            vtm->subsecx = add(vtm->subsecx, INT2FIX(TIME_SCALE));
            sec -= 1;
        }
        if (le(INT2FIX(TIME_SCALE), vtm->subsecx)) {
            vtm->subsecx = sub(vtm->subsecx, INT2FIX(TIME_SCALE));
            sec += 1;
        }
        goto not_zero_sec;
    }
    if (sec) {
      not_zero_sec:
        /* If sec + subsec == 0, don't change vtm->sec.
         * It may be 60 which is a leap second. */
        vtm->sec += sec;
        if (vtm->sec < 0) {
            vtm->sec += 60;
            min -= 1;
        }
        if (60 <= vtm->sec) {
            vtm->sec -= 60;
            min += 1;
        }
    }
    if (min) {
        vtm->min += min;
        if (vtm->min < 0) {
            vtm->min += 60;
            hour -= 1;
        }
        if (60 <= vtm->min) {
            vtm->min -= 60;
            hour += 1;
        }
    }
    if (hour) {
        vtm->hour += hour;
        if (vtm->hour < 0) {
            vtm->hour += 24;
            day = -1;
        }
        if (24 <= vtm->hour) {
            vtm->hour -= 24;
            day = 1;
        }
    }

    if (day) {
        if (day < 0) {
            if (vtm->mon == 1 && vtm->mday == 1) {
                vtm->mday = 31;
                vtm->mon = 12; /* December */
                vtm->year = sub(vtm->year, INT2FIX(1));
                vtm->yday = leap_year_v_p(vtm->year) ? 365 : 364;
            }
            else if (vtm->mday == 1) {
                const int *days_in_month = leap_year_v_p(vtm->year) ?
                                           leap_year_days_in_month :
                                           common_year_days_in_month;
                vtm->mon--;
                vtm->mday = days_in_month[vtm->mon-1];
                vtm->yday--;
            }
            else {
                vtm->mday--;
                vtm->yday--;
            }
            vtm->wday = (vtm->wday + 6) % 7;
        }
        else {
            int leap = leap_year_v_p(vtm->year);
            if (vtm->mon == 12 && vtm->mday == 31) {
                vtm->year = add(vtm->year, INT2FIX(1));
                vtm->mon = 1; /* January */
                vtm->mday = 1;
                vtm->yday = 1;
            }
            else if (vtm->mday == (leap ? leap_year_days_in_month :
                                          common_year_days_in_month)[vtm->mon-1]) {
                vtm->mon++;
                vtm->mday = 1;
                vtm->yday++;
            }
            else {
                vtm->mday++;
                vtm->yday++;
            }
            vtm->wday = (vtm->wday + 1) % 7;
        }
    }
}

static VALUE
utc_offset_arg(VALUE arg)
{
    VALUE tmp;
    if (!NIL_P(tmp = rb_check_string_type(arg))) {
        int n;
        char *s = RSTRING_PTR(tmp);
        if (!rb_enc_str_asciicompat_p(tmp) ||
            RSTRING_LEN(tmp) != 6 ||
            (s[0] != '+' && s[0] != '-') ||
            !ISDIGIT(s[1]) ||
            !ISDIGIT(s[2]) ||
            s[3] != ':' ||
            !ISDIGIT(s[4]) ||
            !ISDIGIT(s[5]))
            rb_raise(rb_eArgError, "\"+HH:MM\" or \"-HH:MM\" expected for utc_offset");
        n = (s[1] * 10 + s[2] - '0' * 11) * 3600;
        n += (s[4] * 10 + s[5] - '0' * 11) * 60;
        if (s[0] == '-')
            n = -n;
        return INT2FIX(n);
    }
    else {
        return num_exact(arg);
    }
}

static VALUE
time_init_1(int argc, VALUE *argv, VALUE time)
{
    struct vtm vtm;
    VALUE v[7];
    struct time_object *tobj;

    vtm.wday = -1;
    vtm.yday = 0;
    vtm.zone = "";

    /*                             year  mon   mday  hour  min   sec   off */
    rb_scan_args(argc, argv, "16", &v[0],&v[1],&v[2],&v[3],&v[4],&v[5],&v[6]);

    vtm.year = obj2vint(v[0]);

    vtm.mon = NIL_P(v[1]) ? 1 : month_arg(v[1]);

    vtm.mday = NIL_P(v[2]) ? 1 : obj2int(v[2]);

    vtm.hour = NIL_P(v[3]) ? 0 : obj2int(v[3]);

    vtm.min  = NIL_P(v[4]) ? 0 : obj2int(v[4]);

    vtm.sec = 0;
    vtm.subsecx = INT2FIX(0);
    if (!NIL_P(v[5])) {
        VALUE sec = num_exact(v[5]);
        VALUE subsec;
        divmodv(sec, INT2FIX(1), &sec, &subsec);
        vtm.sec = NUM2INT(sec);
        vtm.subsecx = rb_time_magnify(subsec);
    }

    vtm.isdst = -1;
    vtm.utc_offset = Qnil;
    if (!NIL_P(v[6])) {
        VALUE arg = v[6];
        if (arg == ID2SYM(rb_intern("dst")))
            vtm.isdst = 1;
        else if (arg == ID2SYM(rb_intern("std")))
            vtm.isdst = 0;
        else
            vtm.utc_offset = utc_offset_arg(arg);
    }

    validate_vtm(&vtm);

    time_modify(time);
    GetTimeval(time, tobj);
    tobj->tm_got=0;
    tobj->timexv = INT2FIX(0);

    if (!NIL_P(vtm.utc_offset)) {
        VALUE off = vtm.utc_offset;
        vtm_add_offset(&vtm, neg(off));
        vtm.utc_offset = Qnil;
        tobj->timexv = timegmxv(&vtm);
        return time_set_utc_offset(time, off);
    }
    else {
        tobj->timexv = timelocalxv(&vtm);
        return time_localtime(time);
    }
}


/*
 *  call-seq:
 *     Time.new -> time
 *     Time.new(year) -> time
 *     Time.new(year, month) -> time
 *     Time.new(year, month, day) -> time
 *     Time.new(year, month, day, hour) -> time
 *     Time.new(year, month, day, hour, min) -> time
 *     Time.new(year, month, day, hour, min, sec) -> time
 *     Time.new(year, month, day, hour, min, sec, utc_offset) -> time
 *
 *  Returns a <code>Time</code> object.
 *
 *  It is initialized to the current system time if no argument.
 *  <b>Note:</b> The object created will be created using the
 *  resolution available on your system clock, and so may include
 *  fractional seconds.
 *
 *  If one or more arguments specified, the time is initialized
 *  to the specified time.
 *  _sec_ may have fraction if it is a rational.
 *
 *  _utc_offset_ is the offset from UTC.
 *  It is a string such as "+09:00" or a number of seconds such as 32400.
 *
 *     a = Time.new      #=> 2007-11-19 07:50:02 -0600
 *     b = Time.new      #=> 2007-11-19 07:50:02 -0600
 *     a == b            #=> false
 *     "%.6f" % a.to_f   #=> "1195480202.282373"
 *     "%.6f" % b.to_f   #=> "1195480202.283415"
 *
 *     Time.new(2008,6,21, 13,30,0, "+09:00") #=> 2008-06-21 13:30:00 +0900
 *
 *     # A trip for RubyConf 2007
 *     t1 = Time.new(2007,11,1,15,25,0, "+09:00") # JST (Narita)
 *     t2 = Time.new(2007,11,1,12, 5,0, "-05:00") # CDT (Minneapolis)
 *     t3 = Time.new(2007,11,1,13,25,0, "-05:00") # CDT (Minneapolis)
 *     t4 = Time.new(2007,11,1,16,53,0, "-04:00") # EDT (Charlotte) 
 *     t5 = Time.new(2007,11,5, 9,24,0, "-05:00") # EST (Charlotte)
 *     t6 = Time.new(2007,11,5,11,21,0, "-05:00") # EST (Detroit)
 *     t7 = Time.new(2007,11,5,13,45,0, "-05:00") # EST (Detroit)
 *     t8 = Time.new(2007,11,6,17,10,0, "+09:00") # JST (Narita)
 *     p((t2-t1)/3600.0)                          #=> 10.666666666666666
 *     p((t4-t3)/3600.0)                          #=> 2.466666666666667
 *     p((t6-t5)/3600.0)                          #=> 1.95
 *     p((t8-t7)/3600.0)                          #=> 13.416666666666666
 *
 */

static VALUE
time_init(int argc, VALUE *argv, VALUE time)
{
    if (argc == 0)
        return time_init_0(time);
    else
        return time_init_1(argc, argv, time);
}

static void
time_overflow_p(time_t *secp, long *nsecp)
{
    time_t tmp, sec = *secp;
    long nsec = *nsecp;

    if (nsec >= 1000000000) {	/* nsec positive overflow */
	tmp = sec + nsec / 1000000000;
	nsec %= 1000000000;
	if (sec > 0 && tmp < 0) {
	    rb_raise(rb_eRangeError, "out of Time range");
	}
	sec = tmp;
    }
    if (nsec < 0) {		/* nsec negative overflow */
	tmp = sec + NDIV(nsec,1000000000); /* negative div */
	nsec = NMOD(nsec,1000000000);      /* negative mod */
	if (sec < 0 && tmp > 0) {
	    rb_raise(rb_eRangeError, "out of Time range");
	}
	sec = tmp;
    }
#ifndef NEGATIVE_TIME_T
    if (sec < 0)
	rb_raise(rb_eArgError, "time must be positive");
#endif
    *secp = sec;
    *nsecp = nsec;
}

static VALUE nsec2timexv(time_t sec, long nsec)
{
    struct timespec ts;
    time_overflow_p(&sec, &nsec);
    ts.tv_sec = sec;
    ts.tv_nsec = nsec;
    return timespec2timexv(&ts);
}

static VALUE
time_new_internal(VALUE klass, VALUE timexv)
{
    VALUE time = time_s_alloc(klass);
    struct time_object *tobj;

    GetTimeval(time, tobj);
    tobj->timexv = num_exact(timexv);

    return time;
}

VALUE
rb_time_new(time_t sec, long usec)
{
    return time_new_internal(rb_cTime, nsec2timexv(sec, usec * 1000));
}

VALUE
rb_time_nano_new(time_t sec, long nsec)
{
    return time_new_internal(rb_cTime, nsec2timexv(sec, nsec));
}

VALUE
rb_time_num_new(VALUE timev, VALUE off)
{
    VALUE time = time_new_internal(rb_cTime, rb_time_magnify(timev));

    if (!NIL_P(off)) {
        off = utc_offset_arg(off);
        validate_utc_offset(off);
        time_set_utc_offset(time, off);
        return time;
    }

    return time;
}

static VALUE
time_new_timexv(VALUE klass, VALUE timexv)
{
    VALUE time = time_s_alloc(klass);
    struct time_object *tobj;

    GetTimeval(time, tobj);
    tobj->timexv = timexv;

    return time;
}

static struct timespec
time_timespec(VALUE num, int interval)
{
    struct timespec t;
    const char *tstr = interval ? "time interval" : "time";
    VALUE i, f, ary;

#ifndef NEGATIVE_TIME_T
    interval = 1;
#endif

    switch (TYPE(num)) {
      case T_FIXNUM:
	t.tv_sec = NUM2TIMET(num);
	if (interval && t.tv_sec < 0)
	    rb_raise(rb_eArgError, "%s must be positive", tstr);
	t.tv_nsec = 0;
	break;

      case T_FLOAT:
	if (interval && RFLOAT_VALUE(num) < 0.0)
	    rb_raise(rb_eArgError, "%s must be positive", tstr);
	else {
	    double f, d;

	    d = modf(RFLOAT_VALUE(num), &f);
	    if (d >= 0) {
		t.tv_nsec = (int)(d*1e9+0.5);
	    }
	    else if ((t.tv_nsec = (int)(-d*1e9+0.5)) > 0) {
		t.tv_nsec = 1000000000 - t.tv_nsec;
		f -= 1;
	    }
	    t.tv_sec = (time_t)f;
	    if (f != t.tv_sec) {
		rb_raise(rb_eRangeError, "%f out of Time range", RFLOAT_VALUE(num));
	    }
	}
	break;

      case T_BIGNUM:
	t.tv_sec = NUM2TIMET(num);
	if (interval && t.tv_sec < 0)
	    rb_raise(rb_eArgError, "%s must be positive", tstr);
	t.tv_nsec = 0;
	break;

      default:
        if (rb_respond_to(num, id_divmod)) {
            ary = rb_check_array_type(rb_funcall(num, id_divmod, 1, INT2FIX(1)));
            if (NIL_P(ary)) {
                goto typeerror;
            }
            i = rb_ary_entry(ary, 0);
            f = rb_ary_entry(ary, 1);
            t.tv_sec = NUM2TIMET(i);
            if (interval && t.tv_sec < 0)
                rb_raise(rb_eArgError, "%s must be positive", tstr);
            f = rb_funcall(f, id_mul, 1, INT2FIX(1000000000));
            t.tv_nsec = NUM2LONG(f);
        }
        else {
typeerror:
            rb_raise(rb_eTypeError, "can't convert %s into %s",
                     rb_obj_classname(num), tstr);
        }
	break;
    }
    return t;
}

static struct timeval
time_timeval(VALUE num, int interval)
{
    struct timespec ts;
    struct timeval tv;

    ts = time_timespec(num, interval);
    tv.tv_sec = (TYPEOF_TIMEVAL_TV_SEC)ts.tv_sec;
    tv.tv_usec = (TYPEOF_TIMEVAL_TV_USEC)(ts.tv_nsec / 1000);

    return tv;
}

struct timeval
rb_time_interval(VALUE num)
{
    return time_timeval(num, TRUE);
}

struct timeval
rb_time_timeval(VALUE time)
{
    struct time_object *tobj;
    struct timeval t;
    struct timespec ts;

    if (IsTimeval(time)) {
	GetTimeval(time, tobj);
        ts = timexv2timespec(tobj->timexv);
        t.tv_sec = (TYPEOF_TIMEVAL_TV_SEC)ts.tv_sec;
        t.tv_usec = (TYPEOF_TIMEVAL_TV_USEC)(ts.tv_nsec / 1000);
	return t;
    }
    return time_timeval(time, FALSE);
}

struct timespec
rb_time_timespec(VALUE time)
{
    struct time_object *tobj;
    struct timespec t;

    if (IsTimeval(time)) {
	GetTimeval(time, tobj);
        t = timexv2timespec(tobj->timexv);
	return t;
    }
    return time_timespec(time, FALSE);
}

/*
 *  call-seq:
 *     Time.now => time
 *
 *  Creates a new time object for the current time.
 *
 *     Time.now            #=> 2009-06-24 12:39:54 +0900
 */

static VALUE
time_s_now(VALUE klass)
{
    return rb_class_new_instance(0, NULL, klass);
}

/*
 *  call-seq:
 *     Time.at(time) => time
 *     Time.at(seconds_with_frac) => time
 *     Time.at(seconds, microseconds_with_frac) => time
 *
 *  Creates a new time object with the value given by <i>time</i>,
 *  the given number of <i>seconds_with_frac</i>, or
 *  <i>seconds</i> and <i>microseconds_with_frac</i> from the Epoch.
 *  <i>seconds_with_frac</i> and <i>microseconds_with_frac</i>
 *  can be Integer, Float, Rational, or other Numeric.
 *  non-portable feature allows the offset to be negative on some systems.
 *
 *     Time.at(0)            #=> 1969-12-31 18:00:00 -0600
 *     Time.at(Time.at(0))   #=> 1969-12-31 18:00:00 -0600
 *     Time.at(946702800)    #=> 1999-12-31 23:00:00 -0600
 *     Time.at(-284061600)   #=> 1960-12-31 00:00:00 -0600
 *     Time.at(946684800.2).usec #=> 200000
 *     Time.at(946684800, 123456.789).nsec #=> 123456789
 */

static VALUE
time_s_at(int argc, VALUE *argv, VALUE klass)
{
    VALUE time, t, timexv;

    if (rb_scan_args(argc, argv, "11", &time, &t) == 2) {
        time = num_exact(time);
        t = num_exact(t);
        timexv = add(rb_time_magnify(time), mulquo(t, INT2FIX(TIME_SCALE), INT2FIX(1000000)));
        t = time_new_timexv(klass, timexv);
    }
    else if (IsTimeval(time)) {
	struct time_object *tobj, *tobj2;
        GetTimeval(time, tobj);
        t = time_new_timexv(klass, tobj->timexv);
	GetTimeval(t, tobj2);
        TIME_COPY_GMT(tobj2, tobj);
    }
    else {
        timexv = rb_time_magnify(num_exact(time));
        t = time_new_timexv(klass, timexv);
    }

    return t;
}

static const char months[][4] = {
    "jan", "feb", "mar", "apr", "may", "jun",
    "jul", "aug", "sep", "oct", "nov", "dec",
};

static int
obj2int(VALUE obj)
{
    if (TYPE(obj) == T_STRING) {
	obj = rb_str_to_inum(obj, 10, FALSE);
    }

    return NUM2INT(obj);
}

static VALUE
obj2vint(VALUE obj)
{
    if (TYPE(obj) == T_STRING) {
	obj = rb_str_to_inum(obj, 10, FALSE);
    }
    else {
        obj = rb_to_int(obj);
    }

    return obj;
}

static int
obj2subsecx(VALUE obj, VALUE *subsecx)
{
    VALUE subsec;

    if (TYPE(obj) == T_STRING) {
	obj = rb_str_to_inum(obj, 10, FALSE);
        *subsecx = INT2FIX(0);
        return NUM2INT(obj);
    }

    divmodv(num_exact(obj), INT2FIX(1), &obj, &subsec);
    *subsecx = rb_time_magnify(subsec);
    return NUM2INT(obj);
}

static long
usec2subsecx(VALUE obj)
{
    if (TYPE(obj) == T_STRING) {
	obj = rb_str_to_inum(obj, 10, FALSE);
    }

    return mulquo(num_exact(obj), INT2FIX(TIME_SCALE), INT2FIX(1000000));
}

static int
month_arg(VALUE arg)
{
    int i, mon;

    VALUE s = rb_check_string_type(arg);
    if (!NIL_P(s)) {
        mon = 0;
        for (i=0; i<12; i++) {
            if (RSTRING_LEN(s) == 3 &&
                STRCASECMP(months[i], RSTRING_PTR(s)) == 0) {
                mon = i+1;
                break;
            }
        }
        if (mon == 0) {
            char c = RSTRING_PTR(s)[0];

            if ('0' <= c && c <= '9') {
                mon = obj2int(s);
            }
        }
    }
    else {
        mon = obj2int(arg);
    }
    return mon;
}

static void
validate_utc_offset(VALUE utc_offset)
{
    if (le(utc_offset, INT2FIX(-86400)) || ge(utc_offset, INT2FIX(86400)))
	rb_raise(rb_eArgError, "utc_offset out of range");
}

static void
validate_vtm(struct vtm *vtm)
{
    if (   vtm->mon  < 1 || vtm->mon  > 12
	|| vtm->mday < 1 || vtm->mday > 31
	|| vtm->hour < 0 || vtm->hour > 24
	|| (vtm->hour == 24 && (vtm->min > 0 || vtm->sec > 0))
	|| vtm->min  < 0 || vtm->min  > 59
	|| vtm->sec  < 0 || vtm->sec  > 60
        || lt(vtm->subsecx, INT2FIX(0)) || ge(vtm->subsecx, INT2FIX(TIME_SCALE))
        || (!NIL_P(vtm->utc_offset) && (validate_utc_offset(vtm->utc_offset), 0)))
	rb_raise(rb_eArgError, "argument out of range");
}

static void
time_arg(int argc, VALUE *argv, struct vtm *vtm)
{
    VALUE v[8];

    vtm->year = INT2FIX(0);
    vtm->mon = 0;
    vtm->mday = 0;
    vtm->hour = 0;
    vtm->min = 0;
    vtm->sec = 0;
    vtm->subsecx = INT2FIX(0);
    vtm->utc_offset = Qnil;
    vtm->wday = 0;
    vtm->yday = 0;
    vtm->isdst = 0;
    vtm->zone = "";

    if (argc == 10) {
	v[0] = argv[5];
	v[1] = argv[4];
	v[2] = argv[3];
	v[3] = argv[2];
	v[4] = argv[1];
	v[5] = argv[0];
	v[6] = Qnil;
	vtm->isdst = RTEST(argv[8]) ? 1 : 0;
    }
    else {
	rb_scan_args(argc, argv, "17", &v[0],&v[1],&v[2],&v[3],&v[4],&v[5],&v[6],&v[7]);
	/* v[6] may be usec or zone (parsedate) */
	/* v[7] is wday (parsedate; ignored) */
	vtm->wday = -1;
	vtm->isdst = -1;
    }

    vtm->year = obj2vint(v[0]);

    if (NIL_P(v[1])) {
        vtm->mon = 1;
    }
    else {
        vtm->mon = month_arg(v[1]);
    }

    if (NIL_P(v[2])) {
	vtm->mday = 1;
    }
    else {
	vtm->mday = obj2int(v[2]);
    }

    vtm->hour = NIL_P(v[3])?0:obj2int(v[3]);

    vtm->min  = NIL_P(v[4])?0:obj2int(v[4]);

    if (!NIL_P(v[6]) && argc == 7) {
        vtm->sec  = NIL_P(v[5])?0:obj2int(v[5]);
        vtm->subsecx  = usec2subsecx(v[6]);
    }
    else {
	/* when argc == 8, v[6] is timezone, but ignored */
        vtm->sec  = NIL_P(v[5])?0:obj2subsecx(v[5], &vtm->subsecx);
    }

    validate_vtm(vtm);
}

static int
leap_year_p(long y)
{
    return ((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0);
}

static time_t
timegm_noleapsecond(struct tm *tm)
{
    long tm_year = tm->tm_year;
    int tm_yday = tm->tm_mday;
    if (leap_year_p(tm_year + 1900))
	tm_yday += leap_year_yday_offset[tm->tm_mon];
    else
	tm_yday += common_year_yday_offset[tm->tm_mon];

    /*
     *  `Seconds Since the Epoch' in SUSv3:
     *  tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
     *  (tm_year-70)*31536000 + ((tm_year-69…