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

#include "sys/types.h"  /* for time_t */
#include "string.h"
#include "limits.h" /* for CHAR_BIT et al. */

#define  _NO_OLDNAMES   /* avoid tznames */
#include "time.h"
#undef _NO_OLDNAMES

#include <errno.h>
#ifndef EOVERFLOW
# define EOVERFLOW 79
#endif

#ifdef WIN32
#define gmtime R_gmtime
#define localtime R_localtime
#define mktime R_mktime
#endif

#include "stdlib.h"
#include "stdint.h"
#include "stdio.h"
#include "fcntl.h"
#include "float.h"  /* for FLT_MAX and DBL_MAX */

#ifndef TRUE
#define TRUE    1
#endif /* !defined TRUE */

#ifndef FALSE
#define FALSE   0
#endif /* !defined FALSE */

#define TYPE_BIT(type)  (sizeof (type) * CHAR_BIT)
#define TYPE_SIGNED(type) (((type) -1) < 0)
#define TYPE_INTEGRAL(type) (((type) 0.5) != 0.5)
#define GRANDPARENTED   "Local time zone must be set--see zic manual page"
#define YEARSPERREPEAT   400    /* years before a Gregorian repeat */
#define AVGSECSPERYEAR   31556952L
#define SECSPERREPEAT ((int_fast64_t) YEARSPERREPEAT * (int_fast64_t) AVGSECSPERYEAR)
#define SECSPERREPEAT_BITS  34  /* ceil(log2(SECSPERREPEAT)) */
#define is_digit(c) ((unsigned)(c) - '0' <= 9)
#define INITIALIZE(x) (x = 0)

#include "tzfile.h"

#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;
    int     goback;
    int     goahead;
    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(const char * codep);
static time_t       detzcode64(const char * codep);
static int      differ_by_repeat(time_t t1, time_t t0);
static const char * getzname(const char * strp);
static const char * getqzname(const char * strp, const int delim);
static const char * getnum(const char * strp, int * nump, int min,
                int max);
static const char * getsecs(const char * strp, long * secsp);
static const char * getoffset(const char * strp, long * offsetp);
static const char * getrule(const char * strp, struct rule * rulep);
static void     gmtload(struct state * sp);
static struct tm *  gmtsub(const time_t * timep, long offset,
                struct tm * tmp);
static struct tm *  localsub(const time_t * timep, long offset,
                struct tm * tmp);
static int      increment_overflow(int * number, int delta);
static int      leaps_thru_end_of(int y);
static int      long_increment_overflow(long * number, int delta);
static int      long_normalize_overflow(long * tensptr,
                int * unitsptr, int base);
static int      normalize_overflow(int * tensptr, int * unitsptr,
                int base);
static void     settzname(void);
static time_t       time1(struct tm * tmp,
                struct tm * (*funcp)(const time_t *,
                long, struct tm *),
                long offset);
static time_t       time2(struct tm *tmp,
                struct tm * (*funcp)(const time_t *,
                long, struct tm*),
                long offset, int * okayp);
static time_t       time2sub(struct tm *tmp,
                struct tm * (*funcp)(const time_t *,
                long, struct tm*),
                long offset, int * okayp, int do_norm_secs);
static struct tm *  timesub(const time_t * timep, long offset,
                const struct state * sp, struct tm * tmp);
static int      tmcomp(const struct tm * atmp,
                const struct tm * btmp);
static time_t       transtime(time_t janfirst, int year,
                const struct rule * rulep, long offset);
static int      typesequiv(const struct state * sp, int a, int b);
static int      tzload(const char * name, struct state * sp,
                int doextend);
static int      tzparse(const char * name, struct state * sp,
                int lastditch);

static struct state lclmem;
static struct state gmtmem;
#define lclptr      (&lclmem)
#define gmtptr      (&gmtmem)

#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;

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

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

static time_t
detzcode64(codep)
const char * const  codep;
{
    register time_t result;
    register int    i;

    result = (codep[0] & 0x80) ?  (~(int_fast64_t) 0) : 0;
    for (i = 0; i < 8; ++i)
        result = result * 256 + (codep[i] & 0xff);
    return result;
}

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

    tzname[0] = wildabbr;
    tzname[1] = wildabbr;
    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];
    }
    /*
    ** 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
differ_by_repeat(t1, t0)
const time_t    t1;
const time_t    t0;
{
    if (TYPE_INTEGRAL(time_t) &&
        TYPE_BIT(time_t) - TYPE_SIGNED(time_t) < SECSPERREPEAT_BITS)
            return 0;
    return (int_fast64_t)t1 - (int_fast64_t)t0 == SECSPERREPEAT;
}

extern const char *getTZinfo(void);
extern void Rf_warning(const char *, ...);

static int
tzload(name, sp, doextend)
register const char *       name;
register struct state * const   sp;
register const int      doextend;
{
    register const char *       p;
    register int            i;
    register int            fid;
    register int            stored;
    register int            nread;
    union {
        struct tzhead   tzhead;
        char        buf[2 * sizeof(struct tzhead) +
                    2 * sizeof *sp +
                    4 * TZ_MAX_TIMES];
    } u;

    /* if (name == NULL && (name = TZDEFAULT) == NULL) return -1; */
    if (name == NULL) {
        name = getTZinfo();
        if( strcmp(name, "unknown") == 0 ) name = TZDEFAULT;
    }
    
    {
        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];
        const char *sname = name;

        if (name[0] == ':')
            ++name;
        doaccess = name[0] == '/';
        if (!doaccess) {
            char buf[1000];
            p = getenv("TZDIR");
            if (p == NULL) {
            snprintf(buf, 1000, "%s/share/zoneinfo", 
                 getenv("R_HOME"));
            buf[999] = '\0';
            p = buf;
            }
            /* 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) {
            Rf_warning("unknown timezone '%s'", sname);
            return -1;
        }
        if ((fid = open(name, OPEN_MODE)) == -1) {
            Rf_warning("unknown timezone '%s'", sname);
            return -1;
        }
        
    }
    nread = read(fid, u.buf, sizeof u.buf);
    if (close(fid) < 0 || nread <= 0)
        return -1;
    for (stored = 4; stored <= 8; stored *= 2) {
        int     ttisstdcnt;
        int     ttisgmtcnt;

        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 (nread - (p - u.buf) <
            sp->timecnt * stored +      /* ats */
            sp->timecnt +           /* types */
            sp->typecnt * 6 +       /* ttinfos */
            sp->charcnt +           /* chars */
            sp->leapcnt * (stored + 4) +    /* lsinfos */
            ttisstdcnt +            /* ttisstds */
            ttisgmtcnt)         /* ttisgmts */
                return -1;
        for (i = 0; i < sp->timecnt; ++i) {
            sp->ats[i] = (stored == 4) ?
                detzcode(p) : detzcode64(p);
            p += stored;
        }
        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 = (stored == 4) ?
                detzcode(p) : detzcode64(p);
            p += stored;
            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;
            }
        /*
        ** If this is an old file, we're done.
        */
        if (u.tzhead.tzh_version[0] == '\0')
            break;
        nread -= p - u.buf;
        for (i = 0; i < nread; ++i)
            u.buf[i] = p[i];
        /*
        ** If this is a narrow integer time_t system, we're done.
        */
        if (stored >= (int) sizeof(time_t) && TYPE_INTEGRAL(time_t))
            break;
    }
    if (doextend && nread > 2 &&
        u.buf[0] == '\n' && u.buf[nread - 1] == '\n' &&
        sp->typecnt + 2 <= TZ_MAX_TYPES) {
            struct state    ts;
            register int    result;

            u.buf[nread - 1] = '\0';
            result = tzparse(&u.buf[1], &ts, FALSE);
            if (result == 0 && ts.typecnt == 2 &&
                sp->charcnt + ts.charcnt <= TZ_MAX_CHARS) {
                    for (i = 0; i < 2; ++i)
                        ts.ttis[i].tt_abbrind +=
                            sp->charcnt;
                    for (i = 0; i < ts.charcnt; ++i)
                        sp->chars[sp->charcnt++] =
                            ts.chars[i];
                    i = 0;
                    while (i < ts.timecnt &&
                        ts.ats[i] <=
                        sp->ats[sp->timecnt - 1])
                            ++i;
                    while (i < ts.timecnt &&
                        sp->timecnt < TZ_MAX_TIMES) {
                        sp->ats[sp->timecnt] =
                            ts.ats[i];
                        sp->types[sp->timecnt] =
                            sp->typecnt +
                            ts.types[i];
                        ++sp->timecnt;
                        ++i;
                    }
                    sp->ttis[sp->typecnt++] = ts.ttis[0];
                    sp->ttis[sp->typecnt++] = ts.ttis[1];
            }
    }
    i = 2 * YEARSPERREPEAT;
    sp->goback = sp->goahead = sp->timecnt > i;
    sp->goback = sp->goback &&
        typesequiv(sp, sp->types[i], sp->types[0]) &&
        differ_by_repeat(sp->ats[i], sp->ats[0]);
    sp->goahead = sp->goahead &&
        typesequiv(sp, sp->types[sp->timecnt - 1],
        sp->types[sp->timecnt - 1 - i]) &&
        differ_by_repeat(sp->ats[sp->timecnt - 1],
             sp->ats[sp->timecnt - 1 - i]);
    return 0;
}

static int
typesequiv(sp, a, b)
const struct state * const  sp;
const int           a;
const int           b;
{
    register int    result;

    if (sp == NULL ||
        a < 0 || a >= sp->typecnt ||
        b < 0 || b >= sp->typecnt)
            result = FALSE;
    else {
        register const struct ttinfo *  ap = &sp->ttis[a];
        register const struct ttinfo *  bp = &sp->ttis[b];
        result = ap->tt_gmtoff == bp->tt_gmtoff &&
            ap->tt_isdst == bp->tt_isdst &&
            ap->tt_ttisstd == bp->tt_ttisstd &&
            ap->tt_ttisgmt == bp->tt_ttisgmt &&
            strcmp(&sp->chars[ap->tt_abbrind],
            &sp->chars[bp->tt_abbrind]) == 0;
    }
    return result;
}

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 don't do any checking here; checking is done later in common-case code.
*/

static const char *
getqzname(register const char *strp, const int delim)
{
    register int    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, FALSE);
    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 forward.
            */
            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;
            sp->timecnt = 0;
            for (year = EPOCH_YEAR;
                sp->timecnt + 2 <= TZ_MAX_TIMES;
                ++year) {
                    time_t  newfirst;

                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 */
                }
                sp->timecnt += 2;
                newfirst = janfirst;
                newfirst += year_lengths[isleap(year)] *
                    SECSPERDAY;
                if (newfirst <= janfirst)
                    break;
                janfirst = newfirst;
            }
        } 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, TRUE) != 0)
        (void) tzparse(gmt, sp, TRUE);
}

static void
tzsetwall(void)
{
    if (lcl_is_set < 0)
        return;
    lcl_is_set = -1;

    if (tzload((char *) NULL, lclptr, TRUE) != 0)
        gmtload(lclptr);
    settzname();
}

void
tzset(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);

    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, TRUE) != 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;
    if ((sp->goback && t < sp->ats[0]) ||
        (sp->goahead && t > sp->ats[sp->timecnt - 1])) {
            time_t          newt = t;
            register time_t     seconds;
            register time_t     tcycles;
            register int_fast64_t   icycles;

            if (t < sp->ats[0])
                seconds = sp->ats[0] - t;
            else    seconds = t - sp->ats[sp->timecnt - 1];
            --seconds;
            tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
            ++tcycles;
            icycles = tcycles;
            if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
                return NULL;
            seconds = icycles;
            seconds *= YEARSPERREPEAT;
            seconds *= AVGSECSPERYEAR;
            if (t < sp->ats[0])
                newt += seconds;
            else    newt -= seconds;
            if (newt < sp->ats[0] ||
                newt > sp->ats[sp->timecnt - 1])
                    return NULL;    /* "cannot happen" */
            result = localsub(&newt, offset, tmp);
            if (result == tmp) {
                register time_t newy;

                newy = tmp->tm_year;
                if (t < sp->ats[0])
                    newy -= icycles * YEARSPERREPEAT;
                else    newy += icycles * YEARSPERREPEAT;
                tmp->tm_year = newy;
                if (tmp->tm_year != newy)
                    return NULL;
            }
            return result;
    }
    if (sp->timecnt == 0 || t < sp->ats[0]) {
        i = 0;
        while (sp->ttis[i].tt_isdst)
            if (++i >= sp->typecnt) {
                i = 0;
                break;
            }
    } else {
        register int    lo = 1;
        register int    hi = sp->timecnt;

        while (lo < hi) {
            register int    mid = (lo + hi) >> 1;

            if (t < sp->ats[mid])
                hi = mid;
            else    lo = mid + 1;
        }
        i = (int) sp->types[lo - 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];
    return result;
}

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


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

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

    if (!gmt_is_set) {
        gmt_is_set = TRUE;
            gmtload(gmtptr);
    }
    result = timesub(timep, offset, gmtptr, tmp);
    return result;
}

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


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

static struct tm *
timesub(const time_t * const timep,
    const long offset,
    const struct state * const sp,
    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;
    i = sp->leapcnt;
    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;
    return tmp;
}


/*
** 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)(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)) {
        errno = EOVERFLOW;
        return WRONG;
    }
    }
    if (normalize_overflow(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR)) {
    errno = EOVERFLOW;
    return WRONG;
    }
    if (normalize_overflow(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY)) {
    errno = EOVERFLOW;
    return WRONG;
    }
    y = yourtm.tm_year;
    if (long_normalize_overflow(&y, &yourtm.tm_mon, MONSPERYEAR)) {
    errno = EOVERFLOW;
    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)) {
    errno = EOVERFLOW;
    return WRONG;
    }
    while (yourtm.tm_mday <= 0) {
    if (long_increment_overflow(&y, -1)) {
        errno = EOVERFLOW;
        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)) {
        errno = EOVERFLOW;
        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)) {
        errno = EOVERFLOW;
        return WRONG;
        }
    }
    }
    if (long_increment_overflow(&y, -TM_YEAR_BASE)) {
    errno = EOVERFLOW;
    return WRONG;
    }
    yourtm.tm_year = y;
    if (yourtm.tm_year != y) {
    errno = EOVERFLOW;
    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)) {
        errno = EOVERFLOW;
        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;
    } 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;
    } 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) {
            errno = EOVERFLOW;
            return WRONG;
        }
        ++lo;
        } else if (t == hi) {
        --t;
        if (t >= hi) {
            errno = EOVERFLOW;
            return WRONG;
        }
        --hi;
        }
        if (lo > hi) {
        errno = EOVERFLOW;
        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.
    */
    sp = (const struct state *)
        ((funcp == localsub) ? lclptr : gmtptr);
    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;
        }
    }
    errno = EOVERFLOW;
    return WRONG;
    }
label:
    newt = t + saved_seconds;
    if ((newt < t) != (saved_seconds < 0)) {
    errno = EOVERFLOW;
    return WRONG;
    }
    t = newt;
    if ((*funcp)(&t, offset, tmp))
    *okayp = TRUE;
    return t;
}

static time_t
time2(struct tm * const tmp,
      struct tm * (* const funcp)(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)(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 */

    /* R change.  This appears to be required by POSIX (it says
       the setting is used 'initially') and is documented for
       Solaris.
    
       Try unknown DST setting, if it was set.
    */
    if (tmp->tm_isdst >= 0) {
        tmp->tm_isdst = -1;
        t = time2(tmp, funcp, offset, &okay);
        if (okay) return t;
    }
    
    /*
    ** 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.
    */
    sp = (const struct state *) ((funcp == localsub) ?  lclptr : gmtptr);
    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;
        }
    }
    errno = EOVERFLOW;
    return WRONG;
}

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