src/lib/stdtime/localtime.c

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/*
** This file is in the public domain, so clarified as of
** 1996-06-05 by Arthur David Olson.
*/

#ifndef lint
#ifndef NOID
static char     elsieid[] = "@(#)localtime.c    7.99";
#endif /* !defined NOID */
#endif /* !defined lint */

/*
** Leap second handling from Bradley White.
** POSIX-style TZ environment variable handling from Guy Harris.
*/

/*LINTLIBRARY*/

#include "private.h"
#include "tzfile.h"
#include "fcntl.h"
#include "float.h"      /* for FLT_MAX and DBL_MAX */

#ifndef TZ_ABBR_MAX_LEN
#define TZ_ABBR_MAX_LEN 16
#endif /* !defined TZ_ABBR_MAX_LEN */

#ifndef TZ_ABBR_CHAR_SET
#define TZ_ABBR_CHAR_SET \
        "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 :+-._"
#endif /* !defined TZ_ABBR_CHAR_SET */

#ifndef TZ_ABBR_ERR_CHAR
#define TZ_ABBR_ERR_CHAR        '_'
#endif /* !defined TZ_ABBR_ERR_CHAR */

/*
** SunOS 4.1.1 headers lack O_BINARY.
*/

#ifdef O_BINARY
#define OPEN_MODE       (O_RDONLY | O_BINARY)
#endif /* defined O_BINARY */
#ifndef O_BINARY
#define OPEN_MODE       O_RDONLY
#endif /* !defined O_BINARY */

#ifndef WILDABBR
/*
** Someone might make incorrect use of a time zone abbreviation:
**      1.      They might reference tzname[0] before calling tzset (explicitly
**              or implicitly).
**      2.      They might reference tzname[1] before calling tzset (explicitly
**              or implicitly).
**      3.      They might reference tzname[1] after setting to a time zone
**              in which Daylight Saving Time is never observed.
**      4.      They might reference tzname[0] after setting to a time zone
**              in which Standard Time is never observed.
**      5.      They might reference tm.TM_ZONE after calling offtime.
** What's best to do in the above cases is open to debate;
** for now, we just set things up so that in any of the five cases
** WILDABBR is used. Another possibility: initialize tzname[0] to the
** string "tzname[0] used before set", and similarly for the other cases.
** And another: initialize tzname[0] to "ERA", with an explanation in the
** manual page of what this "time zone abbreviation" means (doing this so
** that tzname[0] has the "normal" length of three characters).
*/
#define WILDABBR        "   "
#endif /* !defined WILDABBR */

static char             wildabbr[] = WILDABBR;

static const char       gmt[] = "GMT";

/*
** The DST rules to use if TZ has no rules and we can't load TZDEFRULES.
** We default to US rules as of 1999-08-17.
** POSIX 1003.1 section 8.1.1 says that the default DST rules are
** implementation dependent; for historical reasons, US rules are a
** common default.
*/
#ifndef TZDEFRULESTRING
#define TZDEFRULESTRING ",M4.1.0,M10.5.0"
#endif /* !defined TZDEFDST */

struct ttinfo {                         /* time type information */
        long            tt_gmtoff;      /* UTC offset in seconds */
        int             tt_isdst;       /* used to set tm_isdst */
        int             tt_abbrind;     /* abbreviation list index */
        int             tt_ttisstd;     /* TRUE if transition is std time */
        int             tt_ttisgmt;     /* TRUE if transition is UTC */
};

struct lsinfo {                         /* leap second information */
        time_t          ls_trans;       /* transition time */
        long            ls_corr;        /* correction to apply */
};

#define BIGGEST(a, b)   (((a) > (b)) ? (a) : (b))

#ifdef TZNAME_MAX
#define MY_TZNAME_MAX   TZNAME_MAX
#endif /* defined TZNAME_MAX */
#ifndef TZNAME_MAX
#define MY_TZNAME_MAX   255
#endif /* !defined TZNAME_MAX */

struct state {
        int             leapcnt;
        int             timecnt;
        int             typecnt;
        int             charcnt;
        time_t          ats[TZ_MAX_TIMES];
        unsigned char   types[TZ_MAX_TIMES];
        struct ttinfo   ttis[TZ_MAX_TYPES];
        char            chars[BIGGEST(BIGGEST(TZ_MAX_CHARS + 1, sizeof gmt),
                                (2 * (MY_TZNAME_MAX + 1)))];
        struct lsinfo   lsis[TZ_MAX_LEAPS];
};

struct rule {
        int             r_type;         /* type of rule--see below */
        int             r_day;          /* day number of rule */
        int             r_week;         /* week number of rule */
        int             r_mon;          /* month number of rule */
        long            r_time;         /* transition time of rule */
};

#define JULIAN_DAY              0       /* Jn - Julian day */
#define DAY_OF_YEAR             1       /* n - day of year */
#define MONTH_NTH_DAY_OF_WEEK   2       /* Mm.n.d - month, week, day of week */

/*
** Prototypes for static functions.
*/

static long             detzcode P((const char * codep));
static const char *     getzname P((const char * strp));
static const char *     getqzname P((const char * strp, const char delim));
static const char *     getnum P((const char * strp, int * nump, int min,
                                int max));
static const char *     getsecs P((const char * strp, long * secsp));
static const char *     getoffset P((const char * strp, long * offsetp));
static const char *     getrule P((const char * strp, struct rule * rulep));
static void             gmtload P((struct state * sp));
static struct tm *      gmtsub P((const time_t * timep, long offset,
                                struct tm * tmp));
static struct tm *      localsub P((const time_t * timep, long offset,
                                struct tm * tmp));
static int              increment_overflow P((int * number, int delta));
static int              leaps_thru_end_of P((int y));
static int              long_increment_overflow P((long * number, int delta));
static int              long_normalize_overflow P((long * tensptr,
                                int * unitsptr, int base));
static int              normalize_overflow P((int * tensptr, int * unitsptr,
                                int base));
static void             settzname P((void));
static time_t           time1 P((struct tm * tmp,
                                struct tm * (*funcp) P((const time_t *,
                                long, struct tm *)),
                                long offset));
static time_t           time2 P((struct tm *tmp,
                                struct tm * (*funcp) P((const time_t *,
                                long, struct tm*)),
                                long offset, int * okayp));
static time_t           time2sub P((struct tm *tmp,
                                struct tm * (*funcp) P((const time_t *,
                                long, struct tm*)),
                                long offset, int * okayp, int do_norm_secs));
static struct tm *      timesub P((const time_t * timep, long offset,
                                const struct state * sp, struct tm * tmp));
static int              tmcomp P((const struct tm * atmp,
                                const struct tm * btmp));
static time_t           transtime P((time_t janfirst, int year,
                                const struct rule * rulep, long offset));
static int              tzload P((const char * name, struct state * sp));
static int              tzparse P((const char * name, struct state * sp,
                                int lastditch));

#ifdef ALL_STATE
static struct state *   lclptr;
static struct state *   gmtptr;
#endif /* defined ALL_STATE */

#ifndef ALL_STATE
static struct state     lclmem;
static struct state     gmtmem;
#define lclptr          (&lclmem)
#define gmtptr          (&gmtmem)
#endif /* State Farm */

#ifndef TZ_STRLEN_MAX
#define TZ_STRLEN_MAX 255
#endif /* !defined TZ_STRLEN_MAX */

static char             lcl_TZname[TZ_STRLEN_MAX + 1];
static int              lcl_is_set;
static int              gmt_is_set;

char *                  tzname[2] = {
        wildabbr,
        wildabbr
};

/*
** Section 4.12.3 of X3.159-1989 requires that
**      Except for the strftime function, these functions [asctime,
**      ctime, gmtime, localtime] return values in one of two static
**      objects: a broken-down time structure and an array of char.
** Thanks to Paul Eggert for noting this.
*/

static struct tm        tm;

#ifdef USG_COMPAT
time_t                  timezone = 0;
int                     daylight = 0;
#endif /* defined USG_COMPAT */

#ifdef ALTZONE
time_t                  altzone = 0;
#endif /* defined ALTZONE */

static long
detzcode(codep)
const char * const      codep;
{
        register long   result;
        register int    i;

        result = (codep[0] & 0x80) ? ~0L : 0L;
        for (i = 0; i < 4; ++i)
                result = (result << 8) | (codep[i] & 0xff);
        return result;
}

static void
settzname P((void))
{
        register struct state * const   sp = lclptr;
        register int                    i;

        tzname[0] = wildabbr;
        tzname[1] = wildabbr;
#ifdef USG_COMPAT
        daylight = 0;
        timezone = 0;
#endif /* defined USG_COMPAT */
#ifdef ALTZONE
        altzone = 0;
#endif /* defined ALTZONE */
#ifdef ALL_STATE
        if (sp == NULL) {
                tzname[0] = tzname[1] = gmt;
                return;
        }
#endif /* defined ALL_STATE */
        for (i = 0; i < sp->typecnt; ++i) {
                register const struct ttinfo * const    ttisp = &sp->ttis[i];

                tzname[ttisp->tt_isdst] =
                        &sp->chars[ttisp->tt_abbrind];
#ifdef USG_COMPAT
                if (ttisp->tt_isdst)
                        daylight = 1;
                if (i == 0 || !ttisp->tt_isdst)
                        timezone = -(ttisp->tt_gmtoff);
#endif /* defined USG_COMPAT */
#ifdef ALTZONE
                if (i == 0 || ttisp->tt_isdst)
                        altzone = -(ttisp->tt_gmtoff);
#endif /* defined ALTZONE */
        }
        /*
        ** And to get the latest zone names into tzname. . .
        */
        for (i = 0; i < sp->timecnt; ++i) {
                register const struct ttinfo * const    ttisp =
                                                        &sp->ttis[
                                                                sp->types[i]];

                tzname[ttisp->tt_isdst] =
                        &sp->chars[ttisp->tt_abbrind];
        }
        /*
        ** Finally, scrub the abbreviations.
        ** First, replace bogus characters.
        */
        for (i = 0; i < sp->charcnt; ++i)
                if (strchr(TZ_ABBR_CHAR_SET, sp->chars[i]) == NULL)
                        sp->chars[i] = TZ_ABBR_ERR_CHAR;
        /*
        ** Second, truncate long abbreviations.
        */
        for (i = 0; i < sp->typecnt; ++i) {
                register const struct ttinfo * const    ttisp = &sp->ttis[i];
                register char *                         cp = &sp->chars[ttisp->tt_abbrind];

                if (strlen(cp) > TZ_ABBR_MAX_LEN &&
                        strcmp(cp, GRANDPARENTED) != 0)
                                *(cp + TZ_ABBR_MAX_LEN) = '\0';
        }
}

static int
tzload(name, sp)
register const char *           name;
register struct state * const   sp;
{
        register const char *   p;
        register int            i;
        register int            fid;

        if (name == NULL && (name = TZDEFAULT) == NULL) {
                return -1;
        }

        {
                register int    doaccess;
                /*
                ** Section 4.9.1 of the C standard says that
                ** "FILENAME_MAX expands to an integral constant expression
                ** that is the size needed for an array of char large enough
                ** to hold the longest file name string that the implementation
                ** guarantees can be opened."
                */
                char            fullname[FILENAME_MAX + 1];

                if (name[0] == ':')
                        ++name;
                doaccess = name[0] == '/';
                if (!doaccess) {
                        if ((p = TZDIR) == NULL)
                                return -1;
                        if ((strlen(p) + strlen(name) + 1) >= sizeof fullname)
                                return -1;
                        (void) strcpy(fullname, p);
                        (void) strcat(fullname, "/");
                        (void) strcat(fullname, name);
                        /*
                        ** Set doaccess if '.' (as in "../") shows up in name.
                        */
                        if (strchr(name, '.') != NULL)
                                doaccess = TRUE;
                        name = fullname;
                }
                if (doaccess && access(name, R_OK) != 0)
                        return -1;
                if ((fid = open(name, OPEN_MODE)) == -1)
                        return -1;
        }
        {
                struct tzhead * tzhp;
                union {
                        struct tzhead   tzhead;
                        char            buf[sizeof *sp + sizeof *tzhp];
                } u;
                int             ttisstdcnt;
                int             ttisgmtcnt;

                i = read(fid, u.buf, sizeof u.buf);
                if (close(fid) != 0)
                        return -1;
                ttisstdcnt = (int) detzcode(u.tzhead.tzh_ttisstdcnt);
                ttisgmtcnt = (int) detzcode(u.tzhead.tzh_ttisgmtcnt);
                sp->leapcnt = (int) detzcode(u.tzhead.tzh_leapcnt);
                sp->timecnt = (int) detzcode(u.tzhead.tzh_timecnt);
                sp->typecnt = (int) detzcode(u.tzhead.tzh_typecnt);
                sp->charcnt = (int) detzcode(u.tzhead.tzh_charcnt);
                p = u.tzhead.tzh_charcnt + sizeof u.tzhead.tzh_charcnt;
                if (sp->leapcnt < 0 || sp->leapcnt > TZ_MAX_LEAPS ||
                        sp->typecnt <= 0 || sp->typecnt > TZ_MAX_TYPES ||
                        sp->timecnt < 0 || sp->timecnt > TZ_MAX_TIMES ||
                        sp->charcnt < 0 || sp->charcnt > TZ_MAX_CHARS ||
                        (ttisstdcnt != sp->typecnt && ttisstdcnt != 0) ||
                        (ttisgmtcnt != sp->typecnt && ttisgmtcnt != 0))
                                return -1;
                if (i - (p - u.buf) < sp->timecnt * 4 + /* ats */
                        sp->timecnt +                   /* types */
                        sp->typecnt * (4 + 2) +         /* ttinfos */
                        sp->charcnt +                   /* chars */
                        sp->leapcnt * (4 + 4) +         /* lsinfos */
                        ttisstdcnt +                    /* ttisstds */
                        ttisgmtcnt)                     /* ttisgmts */
                                return -1;
                for (i = 0; i < sp->timecnt; ++i) {
                        sp->ats[i] = detzcode(p);
                        p += 4;
                }
                for (i = 0; i < sp->timecnt; ++i) {
                        sp->types[i] = (unsigned char) *p++;
                        if (sp->types[i] >= sp->typecnt)
                                return -1;
                }
                for (i = 0; i < sp->typecnt; ++i) {
                        register struct ttinfo *        ttisp;

                        ttisp = &sp->ttis[i];
                        ttisp->tt_gmtoff = detzcode(p);
                        p += 4;
                        ttisp->tt_isdst = (unsigned char) *p++;
                        if (ttisp->tt_isdst != 0 && ttisp->tt_isdst != 1)
                                return -1;
                        ttisp->tt_abbrind = (unsigned char) *p++;
                        if (ttisp->tt_abbrind < 0 ||
                                ttisp->tt_abbrind > sp->charcnt)
                                        return -1;
                }
                for (i = 0; i < sp->charcnt; ++i)
                        sp->chars[i] = *p++;
                sp->chars[i] = '\0';    /* ensure '\0' at end */
                for (i = 0; i < sp->leapcnt; ++i) {
                        register struct lsinfo *        lsisp;

                        lsisp = &sp->lsis[i];
                        lsisp->ls_trans = detzcode(p);
                        p += 4;
                        lsisp->ls_corr = detzcode(p);
                        p += 4;
                }
                for (i = 0; i < sp->typecnt; ++i) {
                        register struct ttinfo *        ttisp;

                        ttisp = &sp->ttis[i];
                        if (ttisstdcnt == 0)
                                ttisp->tt_ttisstd = FALSE;
                        else {
                                ttisp->tt_ttisstd = *p++;
                                if (ttisp->tt_ttisstd != TRUE &&
                                        ttisp->tt_ttisstd != FALSE)
                                                return -1;
                        }
                }
                for (i = 0; i < sp->typecnt; ++i) {
                        register struct ttinfo *        ttisp;

                        ttisp = &sp->ttis[i];
                        if (ttisgmtcnt == 0)
                                ttisp->tt_ttisgmt = FALSE;
                        else {
                                ttisp->tt_ttisgmt = *p++;
                                if (ttisp->tt_ttisgmt != TRUE &&
                                        ttisp->tt_ttisgmt != FALSE)
                                                return -1;
                        }
                }
                /*
                ** Out-of-sort ats should mean we're running on a
                ** signed time_t system but using a data file with
                ** unsigned values (or vice versa).
                */
                for (i = 0; i < sp->timecnt - 2; ++i)
                        if (sp->ats[i] > sp->ats[i + 1]) {
                                ++i;
                                if (TYPE_SIGNED(time_t)) {
                                        /*
                                        ** Ignore the end (easy).
                                        */
                                        sp->timecnt = i;
                                } else {
                                        /*
                                        ** Ignore the beginning (harder).
                                        */
                                        register int    j;

                                        for (j = 0; j + i < sp->timecnt; ++j) {
                                                sp->ats[j] = sp->ats[j + i];
                                                sp->types[j] = sp->types[j + i];
                                        }
                                        sp->timecnt = j;
                                }
                                break;
                        }
        }
        return 0;
}

static const int        mon_lengths[2][MONSPERYEAR] = {
        { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
        { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

static const int        year_lengths[2] = {
        DAYSPERNYEAR, DAYSPERLYEAR
};

/*
** Given a pointer into a time zone string, scan until a character that is not
** a valid character in a zone name is found. Return a pointer to that
** character.
*/

static const char *
getzname(strp)
register const char *   strp;
{
        register char   c;

        while ((c = *strp) != '\0' && !is_digit(c) && c != ',' && c != '-' &&
                c != '+')
                        ++strp;
        return strp;
}

/*
** Given a pointer into an extended time zone string, scan until the ending
** delimiter of the zone name is located.   Return a pointer to the delimiter.
**
** As with getzname above, the legal character set is actually quite
** restricted, with other characters producing undefined results.
** We choose not to care - allowing almost anything to be in the zone abbrev.
*/

static const char *
#if __STDC__
getqzname(register const char *strp, const char delim)
#else /* !__STDC__ */
getqzname(strp, delim)
register const char *   strp;
const char              delim;
#endif /* !__STDC__ */
{
        register char   c;

        while ((c = *strp) != '\0' && c != delim)
                ++strp;
        return strp;
}

/*
** Given a pointer into a time zone string, extract a number from that string.
** Check that the number is within a specified range; if it is not, return
** NULL.
** Otherwise, return a pointer to the first character not part of the number.
*/

static const char *
getnum(strp, nump, min, max)
register const char *   strp;
int * const             nump;
const int               min;
const int               max;
{
        register char   c;
        register int    num;

        if (strp == NULL || !is_digit(c = *strp))
                return NULL;
        num = 0;
        do {
                num = num * 10 + (c - '0');
                if (num > max)
                        return NULL;    /* illegal value */
                c = *++strp;
        } while (is_digit(c));
        if (num < min)
                return NULL;            /* illegal value */
        *nump = num;
        return strp;
}

/*
** Given a pointer into a time zone string, extract a number of seconds,
** in hh[:mm[:ss]] form, from the string.
** If any error occurs, return NULL.
** Otherwise, return a pointer to the first character not part of the number
** of seconds.
*/

static const char *
getsecs(strp, secsp)
register const char *   strp;
long * const            secsp;
{
        int     num;

        /*
        ** `HOURSPERDAY * DAYSPERWEEK - 1' allows quasi-Posix rules like
        ** "M10.4.6/26", which does not conform to Posix,
        ** but which specifies the equivalent of
        ** ``02:00 on the first Sunday on or after 23 Oct''.
        */
        strp = getnum(strp, &num, 0, HOURSPERDAY * DAYSPERWEEK - 1);
        if (strp == NULL)
                return NULL;
        *secsp = num * (long) SECSPERHOUR;
        if (*strp == ':') {
                ++strp;
                strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
                if (strp == NULL)
                        return NULL;
                *secsp += num * SECSPERMIN;
                if (*strp == ':') {
                        ++strp;
                        /* `SECSPERMIN' allows for leap seconds. */
                        strp = getnum(strp, &num, 0, SECSPERMIN);
                        if (strp == NULL)
                                return NULL;
                        *secsp += num;
                }
        }
        return strp;
}

/*
** Given a pointer into a time zone string, extract an offset, in
** [+-]hh[:mm[:ss]] form, from the string.
** If any error occurs, return NULL.
** Otherwise, return a pointer to the first character not part of the time.
*/

static const char *
getoffset(strp, offsetp)
register const char *   strp;
long * const            offsetp;
{
        register int    neg = 0;

        if (*strp == '-') {
                neg = 1;
                ++strp;
        } else if (*strp == '+')
                ++strp;
        strp = getsecs(strp, offsetp);
        if (strp == NULL)
                return NULL;            /* illegal time */
        if (neg)
                *offsetp = -*offsetp;
        return strp;
}

/*
** Given a pointer into a time zone string, extract a rule in the form
** date[/time]. See POSIX section 8 for the format of "date" and "time".
** If a valid rule is not found, return NULL.
** Otherwise, return a pointer to the first character not part of the rule.
*/

static const char *
getrule(strp, rulep)
const char *                    strp;
register struct rule * const    rulep;
{
        if (*strp == 'J') {
                /*
                ** Julian day.
                */
                rulep->r_type = JULIAN_DAY;
                ++strp;
                strp = getnum(strp, &rulep->r_day, 1, DAYSPERNYEAR);
        } else if (*strp == 'M') {
                /*
                ** Month, week, day.
                */
                rulep->r_type = MONTH_NTH_DAY_OF_WEEK;
                ++strp;
                strp = getnum(strp, &rulep->r_mon, 1, MONSPERYEAR);
                if (strp == NULL)
                        return NULL;
                if (*strp++ != '.')
                        return NULL;
                strp = getnum(strp, &rulep->r_week, 1, 5);
                if (strp == NULL)
                        return NULL;
                if (*strp++ != '.')
                        return NULL;
                strp = getnum(strp, &rulep->r_day, 0, DAYSPERWEEK - 1);
        } else if (is_digit(*strp)) {
                /*
                ** Day of year.
                */
                rulep->r_type = DAY_OF_YEAR;
                strp = getnum(strp, &rulep->r_day, 0, DAYSPERLYEAR - 1);
        } else  return NULL;            /* invalid format */
        if (strp == NULL)
                return NULL;
        if (*strp == '/') {
                /*
                ** Time specified.
                */
                ++strp;
                strp = getsecs(strp, &rulep->r_time);
        } else  rulep->r_time = 2 * SECSPERHOUR;        /* default = 2:00:00 */
        return strp;
}

/*
** Given the Epoch-relative time of January 1, 00:00:00 UTC, in a year, the
** year, a rule, and the offset from UTC at the time that rule takes effect,
** calculate the Epoch-relative time that rule takes effect.
*/

static time_t
transtime(janfirst, year, rulep, offset)
const time_t                            janfirst;
const int                               year;
register const struct rule * const      rulep;
const long                              offset;
{
        register int    leapyear;
        register time_t value;
        register int    i;
        int             d, m1, yy0, yy1, yy2, dow;

        INITIALIZE(value);
        leapyear = isleap(year);
        switch (rulep->r_type) {

        case JULIAN_DAY:
                /*
                ** Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
                ** years.
                ** In non-leap years, or if the day number is 59 or less, just
                ** add SECSPERDAY times the day number-1 to the time of
                ** January 1, midnight, to get the day.
                */
                value = janfirst + (rulep->r_day - 1) * SECSPERDAY;
                if (leapyear && rulep->r_day >= 60)
                        value += SECSPERDAY;
                break;

        case DAY_OF_YEAR:
                /*
                ** n - day of year.
                ** Just add SECSPERDAY times the day number to the time of
                ** January 1, midnight, to get the day.
                */
                value = janfirst + rulep->r_day * SECSPERDAY;
                break;

        case MONTH_NTH_DAY_OF_WEEK:
                /*
                ** Mm.n.d - nth "dth day" of month m.
                */
                value = janfirst;
                for (i = 0; i < rulep->r_mon - 1; ++i)
                        value += mon_lengths[leapyear][i] * SECSPERDAY;

                /*
                ** Use Zeller's Congruence to get day-of-week of first day of
                ** month.
                */
                m1 = (rulep->r_mon + 9) % 12 + 1;
                yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
                yy1 = yy0 / 100;
                yy2 = yy0 % 100;
                dow = ((26 * m1 - 2) / 10 +
                        1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
                if (dow < 0)
                        dow += DAYSPERWEEK;

                /*
                ** "dow" is the day-of-week of the first day of the month. Get
                ** the day-of-month (zero-origin) of the first "dow" day of the
                ** month.
                */
                d = rulep->r_day - dow;
                if (d < 0)
                        d += DAYSPERWEEK;
                for (i = 1; i < rulep->r_week; ++i) {
                        if (d + DAYSPERWEEK >=
                                mon_lengths[leapyear][rulep->r_mon - 1])
                                        break;
                        d += DAYSPERWEEK;
                }

                /*
                ** "d" is the day-of-month (zero-origin) of the day we want.
                */
                value += d * SECSPERDAY;
                break;
        }

        /*
        ** "value" is the Epoch-relative time of 00:00:00 UTC on the day in
        ** question. To get the Epoch-relative time of the specified local
        ** time on that day, add the transition time and the current offset
        ** from UTC.
        */
        return value + rulep->r_time + offset;
}

/*
** Given a POSIX section 8-style TZ string, fill in the rule tables as
** appropriate.
*/

static int
tzparse(name, sp, lastditch)
const char *                    name;
register struct state * const   sp;
const int                       lastditch;
{
        const char *                    stdname;
        const char *                    dstname;
        size_t                          stdlen;
        size_t                          dstlen;
        long                            stdoffset;
        long                            dstoffset;
        register time_t *               atp;
        register unsigned char *        typep;
        register char *                 cp;
        register int                    load_result;

        INITIALIZE(dstname);
        stdname = name;
        if (lastditch) {
                stdlen = strlen(name);  /* length of standard zone name */
                name += stdlen;
                if (stdlen >= sizeof sp->chars)
                        stdlen = (sizeof sp->chars) - 1;
                stdoffset = 0;
        } else {
                if (*name == '<') {
                        name++;
                        stdname = name;
                        name = getqzname(name, '>');
                        if (*name != '>')
                                return (-1);
                        stdlen = name - stdname;
                        name++;
                } else {
                        name = getzname(name);
                        stdlen = name - stdname;
                }
                if (*name == '\0')
                        return -1;
                name = getoffset(name, &stdoffset);
                if (name == NULL)
                        return -1;
        }
        load_result = tzload(TZDEFRULES, sp);
        if (load_result != 0)
                sp->leapcnt = 0;                /* so, we're off a little */
        if (*name != '\0') {
                if (*name == '<') {
                        dstname = ++name;
                        name = getqzname(name, '>');
                        if (*name != '>')
                                return -1;
                        dstlen = name - dstname;
                        name++;
                } else {
                        dstname = name;
                        name = getzname(name);
                        dstlen = name - dstname; /* length of DST zone name */
                }
                if (*name != '\0' && *name != ',' && *name != ';') {
                        name = getoffset(name, &dstoffset);
                        if (name == NULL)
                                return -1;
                } else  dstoffset = stdoffset - SECSPERHOUR;
                if (*name == '\0' && load_result != 0)
                        name = TZDEFRULESTRING;
                if (*name == ',' || *name == ';') {
                        struct rule     start;
                        struct rule     end;
                        register int    year;
                        register time_t janfirst;
                        time_t          starttime;
                        time_t          endtime;

                        ++name;
                        if ((name = getrule(name, &start)) == NULL)
                                return -1;
                        if (*name++ != ',')
                                return -1;
                        if ((name = getrule(name, &end)) == NULL)
                                return -1;
                        if (*name != '\0')
                                return -1;
                        sp->typecnt = 2;        /* standard time and DST */
                        /*
                        ** Two transitions per year, from EPOCH_YEAR to 2037.
                        */
                        sp->timecnt = 2 * (2037 - EPOCH_YEAR + 1);
                        if (sp->timecnt > TZ_MAX_TIMES)
                                return -1;
                        sp->ttis[0].tt_gmtoff = -dstoffset;
                        sp->ttis[0].tt_isdst = 1;
                        sp->ttis[0].tt_abbrind = stdlen + 1;
                        sp->ttis[1].tt_gmtoff = -stdoffset;
                        sp->ttis[1].tt_isdst = 0;
                        sp->ttis[1].tt_abbrind = 0;
                        atp = sp->ats;
                        typep = sp->types;
                        janfirst = 0;
                        for (year = EPOCH_YEAR; year <= 2037; ++year) {
                                starttime = transtime(janfirst, year, &start,
                                        stdoffset);
                                endtime = transtime(janfirst, year, &end,
                                        dstoffset);
                                if (starttime > endtime) {
                                        *atp++ = endtime;
                                        *typep++ = 1;   /* DST ends */
                                        *atp++ = starttime;
                                        *typep++ = 0;   /* DST begins */
                                } else {
                                        *atp++ = starttime;
                                        *typep++ = 0;   /* DST begins */
                                        *atp++ = endtime;
                                        *typep++ = 1;   /* DST ends */
                                }
                                janfirst += year_lengths[isleap(year)] *
                                        SECSPERDAY;
                        }
                } else {
                        register long   theirstdoffset;
                        register long   theirdstoffset;
                        register long   theiroffset;
                        register int    isdst;
                        register int    i;
                        register int    j;

                        if (*name != '\0')
                                return -1;
                        /*
                        ** Initial values of theirstdoffset and theirdstoffset.
                        */
                        theirstdoffset = 0;
                        for (i = 0; i < sp->timecnt; ++i) {
                                j = sp->types[i];
                                if (!sp->ttis[j].tt_isdst) {
                                        theirstdoffset =
                                                -sp->ttis[j].tt_gmtoff;
                                        break;
                                }
                        }
                        theirdstoffset = 0;
                        for (i = 0; i < sp->timecnt; ++i) {
                                j = sp->types[i];
                                if (sp->ttis[j].tt_isdst) {
                                        theirdstoffset =
                                                -sp->ttis[j].tt_gmtoff;
                                        break;
                                }
                        }
                        /*
                        ** Initially we're assumed to be in standard time.
                        */
                        isdst = FALSE;
                        theiroffset = theirstdoffset;
                        /*
                        ** Now juggle transition times and types
                        ** tracking offsets as you do.
                        */
                        for (i = 0; i < sp->timecnt; ++i) {
                                j = sp->types[i];
                                sp->types[i] = sp->ttis[j].tt_isdst;
                                if (sp->ttis[j].tt_ttisgmt) {
                                        /* No adjustment to transition time */
                                } else {
                                        /*
                                        ** If summer time is in effect, and the
                                        ** transition time was not specified as
                                        ** standard time, add the summer time
                                        ** offset to the transition time;
                                        ** otherwise, add the standard time
                                        ** offset to the transition time.
                                        */
                                        /*
                                        ** Transitions from DST to DDST
                                        ** will effectively disappear since
                                        ** POSIX provides for only one DST
                                        ** offset.
                                        */
                                        if (isdst && !sp->ttis[j].tt_ttisstd) {
                                                sp->ats[i] += dstoffset -
                                                        theirdstoffset;
                                        } else {
                                                sp->ats[i] += stdoffset -
                                                        theirstdoffset;
                                        }
                                }
                                theiroffset = -sp->ttis[j].tt_gmtoff;
                                if (sp->ttis[j].tt_isdst)
                                        theirdstoffset = theiroffset;
                                else    theirstdoffset = theiroffset;
                        }
                        /*
                        ** Finally, fill in ttis.
                        ** ttisstd and ttisgmt need not be handled.
                        */
                        sp->ttis[0].tt_gmtoff = -stdoffset;
                        sp->ttis[0].tt_isdst = FALSE;
                        sp->ttis[0].tt_abbrind = 0;
                        sp->ttis[1].tt_gmtoff = -dstoffset;
                        sp->ttis[1].tt_isdst = TRUE;
                        sp->ttis[1].tt_abbrind = stdlen + 1;
                        sp->typecnt = 2;
                }
        } else {
                dstlen = 0;
                sp->typecnt = 1;                /* only standard time */
                sp->timecnt = 0;
                sp->ttis[0].tt_gmtoff = -stdoffset;
                sp->ttis[0].tt_isdst = 0;
                sp->ttis[0].tt_abbrind = 0;
        }
        sp->charcnt = stdlen + 1;
        if (dstlen != 0)
                sp->charcnt += dstlen + 1;
        if ((size_t) sp->charcnt > sizeof sp->chars)
                return -1;
        cp = sp->chars;
        (void) strncpy(cp, stdname, stdlen);
        cp += stdlen;
        *cp++ = '\0';
        if (dstlen != 0) {
                (void) strncpy(cp, dstname, dstlen);
                *(cp + dstlen) = '\0';
        }
        return 0;
}

static void
gmtload(sp)
struct state * const    sp;
{
        if (tzload(gmt, sp) != 0)
                (void) tzparse(gmt, sp, TRUE);
}

#ifndef STD_INSPIRED
/*
** A non-static declaration of tzsetwall in a system header file
** may cause a warning about this upcoming static declaration...
*/
static
#endif /* !defined STD_INSPIRED */
void
tzsetwall P((void))
{
        if (lcl_is_set < 0)
                return;
        lcl_is_set = -1;

#ifdef ALL_STATE
        if (lclptr == NULL) {
                lclptr = (struct state *) malloc(sizeof *lclptr);
                if (lclptr == NULL) {
                        settzname();    /* all we can do */
                        return;
                }
        }
#endif /* defined ALL_STATE */
        if (tzload((char *) NULL, lclptr) != 0)
                gmtload(lclptr);
        settzname();
}

void
tzset P((void))
{
        register const char *   name;

        name = getenv("TZ");
        if (name == NULL) {
                tzsetwall();
                return;
        }

        if (lcl_is_set > 0 && strcmp(lcl_TZname, name) == 0) {
                return;
        }
        lcl_is_set = strlen(name) < sizeof lcl_TZname;
        if (lcl_is_set)
                (void) strcpy(lcl_TZname, name);

#ifdef ALL_STATE
        if (lclptr == NULL) {
                lclptr = (struct state *) malloc(sizeof *lclptr);
                if (lclptr == NULL) {
                        settzname();    /* all we can do */
                        return;
                }
        }
#endif /* defined ALL_STATE */
        if (*name == '\0') {
                /*
                ** User wants it fast rather than right.
                */
                lclptr->leapcnt = 0;            /* so, we're off a little */
                lclptr->timecnt = 0;
                lclptr->typecnt = 0;
                lclptr->ttis[0].tt_isdst = 0;
                lclptr->ttis[0].tt_gmtoff = 0;
                lclptr->ttis[0].tt_abbrind = 0;
                (void) strcpy(lclptr->chars, gmt);
        } else if (tzload(name, lclptr) != 0)
                if (name[0] == ':' || tzparse(name, lclptr, FALSE) != 0)
                        (void) gmtload(lclptr);
        settzname();
}

/*
** The easy way to behave "as if no library function calls" localtime
** is to not call it--so we drop its guts into "localsub", which can be
** freely called. (And no, the PANS doesn't require the above behavior--
** but it *is* desirable.)
**
** The unused offset argument is for the benefit of mktime variants.
*/

/*ARGSUSED*/
static struct tm *
localsub(timep, offset, tmp)
const time_t * const    timep;
const long              offset;
struct tm * const       tmp;
{
        register struct state *         sp;
        register const struct ttinfo *  ttisp;
        register int                    i;
        register struct tm *            result;
        const time_t                    t = *timep;

        sp = lclptr;
#ifdef ALL_STATE
        if (sp == NULL)
                return gmtsub(timep, offset, tmp);
#endif /* defined ALL_STATE */
        if (sp->timecnt == 0 || t < sp->ats[0]) {
                i = 0;
                while (sp->ttis[i].tt_isdst)
                        if (++i >= sp->typecnt) {
                                i = 0;
                                break;
                        }
        } else {
                for (i = 1; i < sp->timecnt; ++i)
                        if (t < sp->ats[i])
                                break;
                i = (int) sp->types[i - 1];
        }
        ttisp = &sp->ttis[i];
        /*
        ** To get (wrong) behavior that's compatible with System V Release 2.0
        ** you'd replace the statement below with
        **      t += ttisp->tt_gmtoff;
        **      timesub(&t, 0L, sp, tmp);
        */
        result = timesub(&t, ttisp->tt_gmtoff, sp, tmp);
        tmp->tm_isdst = ttisp->tt_isdst;
        tzname[tmp->tm_isdst] = &sp->chars[ttisp->tt_abbrind];
#ifdef TM_ZONE
        tmp->TM_ZONE = &sp->chars[ttisp->tt_abbrind];
#endif /* defined TM_ZONE */
        return result;
}

struct tm *
localtime(timep)
const time_t * const    timep;
{
        tzset();
        return localsub(timep, 0L, &tm);
}

/*
** Re-entrant version of localtime.
*/

struct tm *
localtime_r(const time_t * const        timep, struct tm *              tmp)
{
        return localsub(timep, 0L, tmp);
}

/*
** gmtsub is to gmtime as localsub is to localtime.
*/

static struct tm *
gmtsub(timep, offset, tmp)
const time_t * const    timep;
const long              offset;
struct tm * const       tmp;
{
        register struct tm *    result;

        if (!gmt_is_set) {
                gmt_is_set = TRUE;
#ifdef ALL_STATE
                gmtptr = (struct state *) malloc(sizeof *gmtptr);
                if (gmtptr != NULL)
#endif /* defined ALL_STATE */
                        gmtload(gmtptr);
        }
        result = timesub(timep, offset, gmtptr, tmp);
#ifdef TM_ZONE
        /*
        ** Could get fancy here and deliver something such as
        ** "UTC+xxxx" or "UTC-xxxx" if offset is non-zero,
        ** but this is no time for a treasure hunt.
        */
        if (offset != 0)
                tmp->TM_ZONE = wildabbr;
        else {
#ifdef ALL_STATE
                if (gmtptr == NULL)
                        tmp->TM_ZONE = gmt;
                else    tmp->TM_ZONE = gmtptr->chars;
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
                tmp->TM_ZONE = gmtptr->chars;
#endif /* State Farm */
        }
#endif /* defined TM_ZONE */
        return result;
}

struct tm *
gmtime(timep)
const time_t * const    timep;
{
        return gmtsub(timep, 0L, &tm);
}

/*
* Re-entrant version of gmtime.
*/

struct tm *
gmtime_r(const time_t * const   timep, struct tm *              tmp)
{
        return gmtsub(timep, 0L, tmp);
}

#ifdef STD_INSPIRED

struct tm *
offtime(timep, offset)
const time_t * const    timep;
const long              offset;
{
        return gmtsub(timep, offset, &tm);
}

#endif /* defined STD_INSPIRED */

/*
** Return the number of leap years through the end of the given year
** where, to make the math easy, the answer for year zero is defined as zero.
*/

static int
leaps_thru_end_of(y)
register const int      y;
{
        return (y >= 0) ? (y / 4 - y / 100 + y / 400) :
                -(leaps_thru_end_of(-(y + 1)) + 1);
}

static struct tm *
timesub(timep, offset, sp, tmp)
const time_t * const                    timep;
const long                              offset;
register const struct state * const     sp;
register struct tm * const              tmp;
{
        register const struct lsinfo *  lp;
        register time_t                 tdays;
        register int                    idays;  /* unsigned would be so 2003 */
        register long                   rem;
        int                             y;
        register const int *            ip;
        register long                   corr;
        register int                    hit;
        register int                    i;

        corr = 0;
        hit = 0;
#ifdef ALL_STATE
        i = (sp == NULL) ? 0 : sp->leapcnt;
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
        i = sp->leapcnt;
#endif /* State Farm */
        while (--i >= 0) {
                lp = &sp->lsis[i];
                if (*timep >= lp->ls_trans) {
                        if (*timep == lp->ls_trans) {
                                hit = ((i == 0 && lp->ls_corr > 0) ||
                                        lp->ls_corr > sp->lsis[i - 1].ls_corr);
                                if (hit)
                                        while (i > 0 &&
                                                sp->lsis[i].ls_trans ==
                                                sp->lsis[i - 1].ls_trans + 1 &&
                                                sp->lsis[i].ls_corr ==
                                                sp->lsis[i - 1].ls_corr + 1) {
                                                        ++hit;
                                                        --i;
                                        }
                        }
                        corr = lp->ls_corr;
                        break;
                }
        }
        y = EPOCH_YEAR;
        tdays = *timep / SECSPERDAY;
        rem = *timep - tdays * SECSPERDAY;
        while (tdays < 0 || tdays >= year_lengths[isleap(y)]) {
                int             newy;
                register time_t tdelta;
                register int    idelta;
                register int    leapdays;

                tdelta = tdays / DAYSPERLYEAR;
                idelta = tdelta;
                if (tdelta - idelta >= 1 || idelta - tdelta >= 1)
                        return NULL;
                if (idelta == 0)
                        idelta = (tdays < 0) ? -1 : 1;
                newy = y;
                if (increment_overflow(&newy, idelta))
                        return NULL;
                leapdays = leaps_thru_end_of(newy - 1) -
                        leaps_thru_end_of(y - 1);
                tdays -= ((time_t) newy - y) * DAYSPERNYEAR;
                tdays -= leapdays;
                y = newy;
        }
        {
                register long   seconds;

                seconds = tdays * SECSPERDAY + 0.5;
                tdays = seconds / SECSPERDAY;
                rem += seconds - tdays * SECSPERDAY;
        }
        /*
        ** Given the range, we can now fearlessly cast...
        */
        idays = tdays;
        rem += offset - corr;
        while (rem < 0) {
                rem += SECSPERDAY;
                --idays;
        }
        while (rem >= SECSPERDAY) {
                rem -= SECSPERDAY;
                ++idays;
        }
        while (idays < 0) {
                if (increment_overflow(&y, -1))
                        return NULL;
                idays += year_lengths[isleap(y)];
        }
        while (idays >= year_lengths[isleap(y)]) {
                idays -= year_lengths[isleap(y)];
                if (increment_overflow(&y, 1))
                        return NULL;
        }
        tmp->tm_year = y;
        if (increment_overflow(&tmp->tm_year, -TM_YEAR_BASE))
                return NULL;
        tmp->tm_yday = idays;
        /*
        ** The "extra" mods below avoid overflow problems.
        */
        tmp->tm_wday = EPOCH_WDAY +
                ((y - EPOCH_YEAR) % DAYSPERWEEK) *
                (DAYSPERNYEAR % DAYSPERWEEK) +
                leaps_thru_end_of(y - 1) -
                leaps_thru_end_of(EPOCH_YEAR - 1) +
                idays;
        tmp->tm_wday %= DAYSPERWEEK;
        if (tmp->tm_wday < 0)
                tmp->tm_wday += DAYSPERWEEK;
        tmp->tm_hour = (int) (rem / SECSPERHOUR);
        rem %= SECSPERHOUR;
        tmp->tm_min = (int) (rem / SECSPERMIN);
        /*
        ** A positive leap second requires a special
        ** representation. This uses "... ??:59:60" et seq.
        */
        tmp->tm_sec = (int) (rem % SECSPERMIN) + hit;
        ip = mon_lengths[isleap(y)];
        for (tmp->tm_mon = 0; idays >= ip[tmp->tm_mon]; ++(tmp->tm_mon))
                idays -= ip[tmp->tm_mon];
        tmp->tm_mday = (int) (idays + 1);
        tmp->tm_isdst = 0;
#ifdef TM_GMTOFF
        tmp->TM_GMTOFF = offset;
#endif /* defined TM_GMTOFF */
        return tmp;
}

char *
ctime(timep)
const time_t * const    timep;
{
/*
** Section 4.12.3.2 of X3.159-1989 requires that
**      The ctime function converts the calendar time pointed to by timer
**      to local time in the form of a string. It is equivalent to
**              asctime(localtime(timer))
*/
        return asctime(localtime(timep));
}

char *
ctime_r(const time_t * const    timep, char *                   buf)
{
        struct tm       mytm;

        return asctime_r(localtime_r(timep, &mytm), buf);
}

/*
** Adapted from code provided by Robert Elz, who writes:
**      The "best" way to do mktime I think is based on an idea of Bob
**      Kridle's (so its said...) from a long time ago.
**      It does a binary search of the time_t space. Since time_t's are
**      just 32 bits, its a max of 32 iterations (even at 64 bits it
**      would still be very reasonable).
*/

#ifndef WRONG
#define WRONG   (-1)
#endif /* !defined WRONG */

/*
** Simplified normalize logic courtesy Paul Eggert.
*/

static int
increment_overflow(number, delta)
int *   number;
int     delta;
{
        int     number0;

        number0 = *number;
        *number += delta;
        return (*number < number0) != (delta < 0);
}

static int
long_increment_overflow(number, delta)
long *  number;
int     delta;
{
        long    number0;

        number0 = *number;
        *number += delta;
        return (*number < number0) != (delta < 0);
}

static int
normalize_overflow(tensptr, unitsptr, base)
int * const     tensptr;
int * const     unitsptr;
const int       base;
{
        register int    tensdelta;

        tensdelta = (*unitsptr >= 0) ?
                (*unitsptr / base) :
                (-1 - (-1 - *unitsptr) / base);
        *unitsptr -= tensdelta * base;
        return increment_overflow(tensptr, tensdelta);
}

static int
long_normalize_overflow(tensptr, unitsptr, base)
long * const    tensptr;
int * const     unitsptr;
const int       base;
{
        register int    tensdelta;

        tensdelta = (*unitsptr >= 0) ?
                (*unitsptr / base) :
                (-1 - (-1 - *unitsptr) / base);
        *unitsptr -= tensdelta * base;
        return long_increment_overflow(tensptr, tensdelta);
}

static int
tmcomp(atmp, btmp)
register const struct tm * const atmp;
register const struct tm * const btmp;
{
        register int    result;

        if ((result = (atmp->tm_year - btmp->tm_year)) == 0 &&
                (result = (atmp->tm_mon - btmp->tm_mon)) == 0 &&
                (result = (atmp->tm_mday - btmp->tm_mday)) == 0 &&
                (result = (atmp->tm_hour - btmp->tm_hour)) == 0 &&
                (result = (atmp->tm_min - btmp->tm_min)) == 0)
                        result = atmp->tm_sec - btmp->tm_sec;
        return result;
}

static time_t
time2sub(tmp, funcp, offset, okayp, do_norm_secs)
struct tm * const       tmp;
struct tm * (* const    funcp) P((const time_t*, long, struct tm*));
const long              offset;
int * const             okayp;
const int               do_norm_secs;
{
        register const struct state *   sp;
        register int                    dir;
        register int                    i, j;
        register int                    saved_seconds;
        register long                   li;
        register time_t                 lo;
        register time_t                 hi;
        long                            y;
        time_t                          newt;
        time_t                          t;
        struct tm                       yourtm, mytm;

        *okayp = FALSE;
        yourtm = *tmp;
        if (do_norm_secs) {
                if (normalize_overflow(&yourtm.tm_min, &yourtm.tm_sec,
                        SECSPERMIN))
                                return WRONG;
        }
        if (normalize_overflow(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR))
                return WRONG;
        if (normalize_overflow(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY))
                return WRONG;
        y = yourtm.tm_year;
        if (long_normalize_overflow(&y, &yourtm.tm_mon, MONSPERYEAR))
                return WRONG;
        /*
        ** Turn y into an actual year number for now.
        ** It is converted back to an offset from TM_YEAR_BASE later.
        */
        if (long_increment_overflow(&y, TM_YEAR_BASE))
                return WRONG;
        while (yourtm.tm_mday <= 0) {
                if (long_increment_overflow(&y, -1))
                        return WRONG;
                li = y + (1 < yourtm.tm_mon);
                yourtm.tm_mday += year_lengths[isleap(li)];
        }
        while (yourtm.tm_mday > DAYSPERLYEAR) {
                li = y + (1 < yourtm.tm_mon);
                yourtm.tm_mday -= year_lengths[isleap(li)];
                if (long_increment_overflow(&y, 1))
                        return WRONG;
        }
        for ( ; ; ) {
                i = mon_lengths[isleap(y)][yourtm.tm_mon];
                if (yourtm.tm_mday <= i)
                        break;
                yourtm.tm_mday -= i;
                if (++yourtm.tm_mon >= MONSPERYEAR) {
                        yourtm.tm_mon = 0;
                        if (long_increment_overflow(&y, 1))
                                return WRONG;
                }
        }
        if (long_increment_overflow(&y, -TM_YEAR_BASE))
                return WRONG;
        yourtm.tm_year = y;
        if (yourtm.tm_year != y)
                return WRONG;
        if (yourtm.tm_sec >= 0 && yourtm.tm_sec < SECSPERMIN)
                saved_seconds = 0;
        else if (y + TM_YEAR_BASE < EPOCH_YEAR) {
                /*
                ** We can't set tm_sec to 0, because that might push the
                ** time below the minimum representable time.
                ** Set tm_sec to 59 instead.
                ** This assumes that the minimum representable time is
                ** not in the same minute that a leap second was deleted from,
                ** which is a safer assumption than using 58 would be.
                */
                if (increment_overflow(&yourtm.tm_sec, 1 - SECSPERMIN))
                        return WRONG;
                saved_seconds = yourtm.tm_sec;
                yourtm.tm_sec = SECSPERMIN - 1;
        } else {
                saved_seconds = yourtm.tm_sec;
                yourtm.tm_sec = 0;
        }
        /*
        ** Do a binary search (this works whatever time_t's type is).
        */
        if (!TYPE_SIGNED(time_t)) {
                lo = 0;
                hi = lo - 1;
        }
#if 0
        else if (!TYPE_INTEGRAL(time_t)) {
                if (sizeof(time_t) > sizeof(float))
                        hi = (time_t) DBL_MAX;
                else    hi = (time_t) FLT_MAX;
                lo = -hi;
        }
#endif
        else {
                lo = 1;
                for (i = 0; i < (int) TYPE_BIT(time_t) - 1; ++i)
                        lo *= 2;
                hi = -(lo + 1);
        }
        for ( ; ; ) {
                t = lo / 2 + hi / 2;
                if (t < lo)
                        t = lo;
                else if (t > hi)
                        t = hi;
                if ((*funcp)(&t, offset, &mytm) == NULL) {
                        /*
                        ** Assume that t is too extreme to be represented in
                        ** a struct tm; arrange things so that it is less
                        ** extreme on the next pass.
                        */
                        dir = (t > 0) ? 1 : -1;
                } else  dir = tmcomp(&mytm, &yourtm);
                if (dir != 0) {
                        if (t == lo) {
                                ++t;
                                if (t <= lo)
                                        return WRONG;
                                ++lo;
                        } else if (t == hi) {
                                --t;
                                if (t >= hi)
                                        return WRONG;
                                --hi;
                        }
                        if (lo > hi)
                                return WRONG;
                        if (dir > 0)
                                hi = t;
                        else    lo = t;
                        continue;
                }
                if (yourtm.tm_isdst < 0 || mytm.tm_isdst == yourtm.tm_isdst)
                        break;
                /*
                ** Right time, wrong type.
                ** Hunt for right time, right type.
                ** It's okay to guess wrong since the guess
                ** gets checked.
                */
                /*
                ** The (void *) casts are the benefit of SunOS 3.3 on Sun 2's.
                */
                sp = (const struct state *)
                        (((void *) funcp == (void *) localsub) ?
                        lclptr : gmtptr);
#ifdef ALL_STATE
                if (sp == NULL)
                        return WRONG;
#endif /* defined ALL_STATE */
                for (i = sp->typecnt - 1; i >= 0; --i) {
                        if (sp->ttis[i].tt_isdst != yourtm.tm_isdst)
                                continue;
                        for (j = sp->typecnt - 1; j >= 0; --j) {
                                if (sp->ttis[j].tt_isdst == yourtm.tm_isdst)
                                        continue;
                                newt = t + sp->ttis[j].tt_gmtoff -
                                        sp->ttis[i].tt_gmtoff;
                                if ((*funcp)(&newt, offset, &mytm) == NULL)
                                        continue;
                                if (tmcomp(&mytm, &yourtm) != 0)
                                        continue;
                                if (mytm.tm_isdst != yourtm.tm_isdst)
                                        continue;
                                /*
                                ** We have a match.
                                */
                                t = newt;
                                goto label;
                        }
                }
                return WRONG;
        }
label:
        newt = t + saved_seconds;
        if ((newt < t) != (saved_seconds < 0))
                return WRONG;
        t = newt;
        if ((*funcp)(&t, offset, tmp))
                *okayp = TRUE;
        return t;
}

static time_t
time2(tmp, funcp, offset, okayp)
struct tm * const       tmp;
struct tm * (* const    funcp) P((const time_t*, long, struct tm*));
const long              offset;
int * const             okayp;
{
        time_t  t;

        /*
        ** First try without normalization of seconds
        ** (in case tm_sec contains a value associated with a leap second).
        ** If that fails, try with normalization of seconds.
        */
        t = time2sub(tmp, funcp, offset, okayp, FALSE);
        return *okayp ? t : time2sub(tmp, funcp, offset, okayp, TRUE);
}

static time_t
time1(tmp, funcp, offset)
struct tm * const       tmp;
struct tm * (* const    funcp) P((const time_t *, long, struct tm *));
const long              offset;
{
        register time_t                 t;
        register const struct state *   sp;
        register int                    samei, otheri;
        register int                    sameind, otherind;
        register int                    i;
        register int                    nseen;
        int                             seen[TZ_MAX_TYPES];
        int                             types[TZ_MAX_TYPES];
        int                             okay;

        if (tmp->tm_isdst > 1)
                tmp->tm_isdst = 1;
        t = time2(tmp, funcp, offset, &okay);
#ifdef PCTS
        /*
        ** PCTS code courtesy Grant Sullivan.
        */
        if (okay)
                return t;
        if (tmp->tm_isdst < 0)
                tmp->tm_isdst = 0;      /* reset to std and try again */
#endif /* defined PCTS */
#ifndef PCTS
        if (okay || tmp->tm_isdst < 0)
                return t;
#endif /* !defined PCTS */
        /*
        ** We're supposed to assume that somebody took a time of one type
        ** and did some math on it that yielded a "struct tm" that's bad.
        ** We try to divine the type they started from and adjust to the
        ** type they need.
        */
        /*
        ** The (void *) casts are the benefit of SunOS 3.3 on Sun 2's.
        */
        sp = (const struct state *) (((void *) funcp == (void *) localsub) ?
                lclptr : gmtptr);
#ifdef ALL_STATE
        if (sp == NULL)
                return WRONG;
#endif /* defined ALL_STATE */
        for (i = 0; i < sp->typecnt; ++i)
                seen[i] = FALSE;
        nseen = 0;
        for (i = sp->timecnt - 1; i >= 0; --i)
                if (!seen[sp->types[i]]) {
                        seen[sp->types[i]] = TRUE;
                        types[nseen++] = sp->types[i];
                }
        for (sameind = 0; sameind < nseen; ++sameind) {
                samei = types[sameind];
                if (sp->ttis[samei].tt_isdst != tmp->tm_isdst)
                        continue;
                for (otherind = 0; otherind < nseen; ++otherind) {
                        otheri = types[otherind];
                        if (sp->ttis[otheri].tt_isdst == tmp->tm_isdst)
                                continue;
                        tmp->tm_sec += sp->ttis[otheri].tt_gmtoff -
                                        sp->ttis[samei].tt_gmtoff;
                        tmp->tm_isdst = !tmp->tm_isdst;
                        t = time2(tmp, funcp, offset, &okay);
                        if (okay)
                                return t;
                        tmp->tm_sec -= sp->ttis[otheri].tt_gmtoff -
                                        sp->ttis[samei].tt_gmtoff;
                        tmp->tm_isdst = !tmp->tm_isdst;
                }
        }
        return WRONG;
}

time_t
mktime(tmp)
struct tm * const       tmp;
{
        tzset();
        return time1(tmp, localsub, 0L);
}

#ifdef STD_INSPIRED

time_t
timelocal(tmp)
struct tm * const       tmp;
{
        tmp->tm_isdst = -1;     /* in case it wasn't initialized */
        return mktime(tmp);
}

time_t
timegm(tmp)
struct tm * const       tmp;
{
        tmp->tm_isdst = 0;
        return time1(tmp, gmtsub, 0L);
}

time_t
timeoff(tmp, offset)
struct tm * const       tmp;
const long              offset;
{
        tmp->tm_isdst = 0;
        return time1(tmp, gmtsub, offset);
}

#endif /* defined STD_INSPIRED */

#ifdef CMUCS

/*
** The following is supplied for compatibility with
** previous versions of the CMUCS runtime library.
*/

long
gtime(tmp)
struct tm * const       tmp;
{
        const time_t    t = mktime(tmp);

        if (t == WRONG)
                return -1;
        return t;
}

#endif /* defined CMUCS */

/*
** XXX--is the below the right way to conditionalize??
*/

#ifdef STD_INSPIRED

/*
** IEEE Std 1003.1-1988 (POSIX) legislates that 536457599
** shall correspond to "Wed Dec 31 23:59:59 UTC 1986", which
** is not the case if we are accounting for leap seconds.
** So, we provide the following conversion routines for use
** when exchanging timestamps with POSIX conforming systems.
*/

static long
leapcorr(timep)
time_t *        timep;
{
        register struct state *         sp;
        register struct lsinfo *        lp;
        register int                    i;

        sp = lclptr;
        i = sp->leapcnt;
        while (--i >= 0) {
                lp = &sp->lsis[i];
                if (*timep >= lp->ls_trans)
                        return lp->ls_corr;
        }
        return 0;
}

time_t
time2posix(t)
time_t  t;
{
        tzset();
        return t - leapcorr(&t);
}

time_t
posix2time(t)
time_t  t;
{
        time_t  x;
        time_t  y;

        tzset();
        /*
        ** For a positive leap second hit, the result
        ** is not unique. For a negative leap second
        ** hit, the corresponding time doesn't exist,
        ** so we return an adjacent second.
        */
        x = t + leapcorr(&t);
        y = x - leapcorr(&x);
        if (y < t) {
                do {
                        x++;
                        y = x - leapcorr(&x);
                } while (y < t);
                if (t != y)
                        return x - 1;
        } else if (y > t) {
                do {
                        --x;
                        y = x - leapcorr(&x);
                } while (y > t);
                if (t != y)
                        return x + 1;
        }
        return x;
}

#endif /* defined STD_INSPIRED */

---