localtime.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * Most of this code is in the public domain, so clarified as of
 * June 5, 1996 by Arthur David Olson (arthur_david_olson@nih.gov).
 *
 * All modifications to this code to abstract timezones away from
 * the environment are by Tilghman Lesher, <tlesher@vcch.com>, with
 * the copyright assigned to Digium.
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * Multi-timezone Localtime code
 * 
 * \author Leap second handling Bradley White (bww@k.gp.cs.cmu.edu).
 * \author POSIX-style TZ environment variable handling from Guy Harris (guy@auspex.com).
 *
 */

/*
 * Asterisk defines
 *
 * Don't mess with these unless you're really sure you know what you're doing.
 */
#ifndef _THREAD_SAFE
#define _THREAD_SAFE
#endif
#define TZ_STRLEN_MAX   255
/* #define DEBUG */


/*LINTLIBRARY*/

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#ifdef DEBUG
#include <stdio.h>
#endif
#include "private.h"
#include "tzfile.h"
#include "asterisk/lock.h"
#include "asterisk/localtime.h"
#include "asterisk/strings.h"


#ifndef lint
#ifndef NOID
static const char elsieid[] = "@(#)localtime.c  7.57";
#endif /* !defined NOID */
#endif /* !defined lint */



/*
** 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 */

#ifdef SOLARIS
#undef TM_ZONE
#undef TM_GMTOFF 
#endif

#ifdef TM_ZONE
#ifndef WILDABBR
/*! \note
 * Someone might make incorrect use of a time zone abbreviation:
 * 1. They might reference tzname[0] before calling ast_tzset (explicitly
 *    or implicitly).
 * 2. They might reference tzname[1] before calling ast_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";
#endif /* TM_ZONE */

/*! \brief FreeBSD defines 'zone' in 'struct tm' as non-const, so don't declare this
   string as const. */
static char    gmt[] = "GMT";

/*!< \brief time type information */
struct ttinfo {
   long     tt_gmtoff;  /*!< GMT 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 GMT */
};

/*! \brief leap second information */
struct lsinfo {
   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 {
   char  name[TZ_STRLEN_MAX + 1];
   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 state   *next;
};

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 *  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 void    gmtsub P((const time_t * timep, long offset,
            struct tm * tmp, const char * zone));
static void    localsub P((const time_t * timep, long offset,
            struct tm * tmp, const char * zone));
static int     increment_overflow P((int * number, int delta));
static int     normalize_overflow P((int * tensptr, int * unitsptr,
            int base));
static time_t     time1 P((struct tm * tmp,
            void(*funcp) P((const time_t *,
            long, struct tm *, const char*)),
            long offset, const char * zone));
static time_t     time2 P((struct tm *tmp,
            void(*funcp) P((const time_t *,
            long, struct tm*, const char*)),
            long offset, int * okayp, const char * zone));
static void    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));

static struct state *   lclptr      = NULL;
static struct state *   last_lclptr = NULL;
static struct state *   gmtptr      = NULL;

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

static int     gmt_is_set;
#ifdef   _THREAD_SAFE
AST_MUTEX_DEFINE_STATIC(lcl_mutex);
AST_MUTEX_DEFINE_STATIC(tzset_mutex);
AST_MUTEX_DEFINE_STATIC(tzsetwall_mutex);
AST_MUTEX_DEFINE_STATIC(gmt_mutex);
#endif

/*
** 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 (eggert@twinsun.com) for noting this.
*/

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

#ifdef DEBUG
   fprintf(stderr,"tzload called with name=%s, sp=%d\n", name, sp);
#endif
   if (name == NULL && (name = TZDEFAULT) == NULL)
      return -1;
   {
      register int   doaccess;
      struct stat stab;
      /*
      ** 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) + 1 + strlen(name) + 1) >= sizeof fullname)
            return -1;
         (void) strncpy(fullname, p, sizeof(fullname) - 1);
         (void) strncat(fullname, "/", sizeof(fullname) - strlen(fullname) - 1);
         (void) strncat(fullname, name, sizeof(fullname) - strlen(fullname) - 1);
         /*
         ** 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;
      if ((fstat(fid, &stab) < 0) || !S_ISREG(stab.st_mode)) {
         close(fid);
         return -1;
      }
   }
   {
      struct tzhead *   tzhp;
      char     buf[sizeof *sp + sizeof *tzhp];
      int      ttisstdcnt;
      int      ttisgmtcnt;

      i = read(fid, buf, sizeof buf);
      if (close(fid) != 0)
         return -1;
      p = buf;
      p += (sizeof tzhp->tzh_magic) + (sizeof tzhp->tzh_reserved);
      ttisstdcnt = (int) detzcode(p);
      p += 4;
      ttisgmtcnt = (int) detzcode(p);
      p += 4;
      sp->leapcnt = (int) detzcode(p);
      p += 4;
      sp->timecnt = (int) detzcode(p);
      p += 4;
      sp->typecnt = (int) detzcode(p);
      p += 4;
      sp->charcnt = (int) detzcode(p);
      p += 4;
      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 - 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;
         }
      }
   }
   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
};

/*! \brief
 * Given a pointer into a time zone string, extract a number from that string.
 * \return 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(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;
}

/*! \brief
 * Given a pointer into a time zone string, extract a number of seconds,
 * in hh[:mm[:ss]] form, from the string.
 * \return 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(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;
}

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

static const char * getoffset(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;
}

/*! \brief
 * 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".
 * \return 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(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;
}

/*! \brief
 * Given the Epoch-relative time of January 1, 00:00:00 GMT, in a year, the
 * year, a rule, and the offset from GMT 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 = 0;
   register int   i;
   int      d, m1, yy0, yy1, yy2, dow;

   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 GMT 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 GMT.
   */
   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 = NULL;
   size_t            stdlen = 0;
   size_t            dstlen = 0;
   long           stdoffset = 0L;
   long           dstoffset = 0L;
   register time_t *    atp;
   register unsigned char *   typep;
   register char *         cp;
   register int         load_result;

   stdname = name;
#ifdef DEBUG
   fprintf(stderr, "tzparse(): loading default rules\n");
#endif
   load_result = tzload(TZDEFRULES, sp);
   if (load_result != 0)
      sp->leapcnt = 0;     /* so, we're off a little */
   if (*name != '\0') {
      if (*name != '\0' && *name != ',' && *name != ';') {
         name = getoffset(name, &dstoffset);
         if (name == NULL)
            return -1;
      } else   dstoffset = stdoffset - SECSPERHOUR;
      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;
         if (load_result != 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;
      }
   } 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 (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);
}

/*
** A non-static declaration of ast_tzsetwall in a system header file
** may cause a warning about this upcoming static declaration...
*/
static
#ifdef   _THREAD_SAFE
int
ast_tzsetwall_basic P((void))
#else
int
ast_tzsetwall P((void))
#endif
{
   struct state *cur_state = lclptr;

   /* Find the appropriate structure, if already parsed */
   while (cur_state != NULL) {
      if (cur_state->name[0] == '\0')
         break;
      cur_state = cur_state->next;
   }
   if (cur_state != NULL)
      return 0;
   cur_state = malloc(sizeof(struct state));
   if (cur_state == NULL) {
      return -1;
   }
   memset(cur_state,0,sizeof(struct state));
   if (tzload((char *) NULL, cur_state) != 0)
#ifdef DEBUG
   {
      fprintf(stderr, "ast_tzsetwall: calling gmtload()\n");
#endif
      gmtload(cur_state);
#ifdef DEBUG
   }
#endif

   if (last_lclptr)
      last_lclptr->next = cur_state;
   else
      lclptr = cur_state;
   last_lclptr = cur_state;
   return 0;
}

#ifdef   _THREAD_SAFE
int
ast_tzsetwall P((void))
{
   ast_mutex_lock(&tzsetwall_mutex);
   ast_tzsetwall_basic();
   ast_mutex_unlock(&tzsetwall_mutex);
   return 0;
}
#endif

#ifdef   _THREAD_SAFE
static int
ast_tzset_basic P((const char *name))
#else
int
ast_tzset P((const char *name))
#endif
{
   struct state *cur_state = lclptr;

   /* Not set at all */
   if (name == NULL) {
      return ast_tzsetwall();
   }

   /* Find the appropriate structure, if already parsed */
   while (cur_state != NULL) {
      if (!strcmp(cur_state->name,name))
         break;
      cur_state = cur_state->next;
   }
   if (cur_state != NULL)
      return 0;

   cur_state = malloc(sizeof(struct state));
   if (cur_state == NULL) {
      return -1;
   }
   memset(cur_state,0,sizeof(*cur_state));

   /* Name is set, but set to the empty string == no adjustments */
   if (name[0] == '\0') {
      /*
      ** User wants it fast rather than right.
      */
      cur_state->leapcnt = 0;    /* so, we're off a little */
      cur_state->timecnt = 0;
      cur_state->ttis[0].tt_gmtoff = 0;
      cur_state->ttis[0].tt_abbrind = 0;
      (void) strncpy(cur_state->chars, gmt, sizeof(cur_state->chars) - 1);
   } else if (tzload(name, cur_state) != 0) {
      if (name[0] == ':') {
         (void) gmtload(cur_state);
      } else if (tzparse(name, cur_state, FALSE) != 0) {
         /* If not found, load localtime */
         if (tzload("/etc/localtime", cur_state) != 0)
            /* Last ditch, get GMT */
            (void) gmtload(cur_state);
      }
   }
   strncpy(cur_state->name, name, sizeof(cur_state->name) - 1);
   if (last_lclptr)
      last_lclptr->next = cur_state;
   else
      lclptr = cur_state;
   last_lclptr = cur_state;
   return 0;
}

#ifdef   _THREAD_SAFE
void
ast_tzset P((const char *name))
{
   ast_mutex_lock(&tzset_mutex);
   ast_tzset_basic(name);
   ast_mutex_unlock(&tzset_mutex);
}
#endif

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

   sp = lclptr;
   /* Find the right zone record */
   if (zone == NULL)
      sp = NULL;
   else
      while (sp != NULL) {
         if (!strcmp(sp->name,zone))
            break;
         sp = sp->next;
      }

   if (sp == NULL) {
      ast_tzsetwall();
      sp = lclptr;
      /* Find the default zone record */
      while (sp != NULL) {
         if (sp->name[0] == '\0')
            break;
         sp = sp->next;
      }
   }

   /* Last ditch effort, use GMT */
   if (sp == NULL) {
      gmtsub(timep, offset, tmp, zone);
      return;
   }
   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 = 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);
   */
   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 */
}

struct tm *
ast_localtime(timep, p_tm, zone)
const time_t * const timep;
struct tm *p_tm;
const char * const   zone;
{
#ifdef _THREAD_SAFE
   ast_mutex_lock(&lcl_mutex);
#endif
   ast_tzset(ast_strlen_zero(zone) ? "/etc/localtime" : zone);
   localsub(timep, 0L, p_tm, zone);
#ifdef _THREAD_SAFE
   ast_mutex_unlock(&lcl_mutex);
#endif
   return(p_tm);
}

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

static void
gmtsub(timep, offset, tmp, zone)
const time_t * const timep;
const long     offset;
struct tm * const tmp;
const char * const   zone;
{
#ifdef   _THREAD_SAFE
   ast_mutex_lock(&gmt_mutex);
#endif
   if (!gmt_is_set) {
      gmt_is_set = TRUE;
      gmtptr = (struct state *) malloc(sizeof *gmtptr);
      if (gmtptr != NULL)
         gmtload(gmtptr);
   }
   ast_mutex_unlock(&gmt_mutex);
   timesub(timep, offset, gmtptr, tmp);
#ifdef TM_ZONE
   /*
   ** Could get fancy here and deliver something such as
   ** "GMT+xxxx" or "GMT-xxxx" if offset is non-zero,
   ** but this is no time for a treasure hunt.
   */
   if (offset != 0)
      tmp->TM_ZONE = wildabbr;
   else {
      if (gmtptr == NULL)
         tmp->TM_ZONE = gmt;
      else  tmp->TM_ZONE = gmtptr->chars;
   }
#endif /* defined TM_ZONE */
}

static void
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 long        days;
   register long        rem;
   register int         y;
   register int         yleap;
   register const int *    ip;
   register long        corr;
   register int         hit;
   register int         i;

   corr = 0;
   hit = 0;
   i = (sp == NULL) ? 0 : 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;
      }
   }
   days = *timep / SECSPERDAY;
   rem = *timep % SECSPERDAY;
#ifdef mc68k
   if (*timep == 0x80000000) {
      /*
      ** A 3B1 muffs the division on the most negative number.
      */
      days = -24855;
      rem = -11648;
   }
#endif /* defined mc68k */
   rem += (offset - corr);
   while (rem < 0) {
      rem += SECSPERDAY;
      --days;
   }
   while (rem >= SECSPERDAY) {
      rem -= SECSPERDAY;
      ++days;
   }
   tmp->tm_hour = (int) (rem / SECSPERHOUR);
   rem = 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;
   tmp->tm_wday = (int) ((EPOCH_WDAY + days) % DAYSPERWEEK);
   if (tmp->tm_wday < 0)
      tmp->tm_wday += DAYSPERWEEK;
   y = EPOCH_YEAR;
#define LEAPS_THRU_END_OF(y)  ((y) / 4 - (y) / 100 + (y) / 400)
   while (days < 0 || days >= (long) year_lengths[yleap = isleap(y)]) {
      register int   newy;

      newy = y + days / DAYSPERNYEAR;
      if (days < 0)
         --newy;
      days -= (newy - y) * DAYSPERNYEAR +
         LEAPS_THRU_END_OF(newy - 1) -
         LEAPS_THRU_END_OF(y - 1);
      y = newy;
   }
   tmp->tm_year = y - TM_YEAR_BASE;
   tmp->tm_yday = (int) days;
   ip = mon_lengths[yleap];
   for (tmp->tm_mon = 0; days >= (long) ip[tmp->tm_mon]; ++(tmp->tm_mon))
      days = days - (long) ip[tmp->tm_mon];
   tmp->tm_mday = (int) (days + 1);
   tmp->tm_isdst = 0;
#ifdef TM_GMTOFF
   tmp->TM_GMTOFF = offset;
#endif /* defined TM_GMTOFF */
}

char *
ast_ctime(timep)
const time_t * const timep;
{
/*
** Section 4.12.3.2 of X3.159-1989 requires that
** The ctime funciton 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 *
ast_ctime_r(timep, buf)
const time_t * const timep;
char *buf;
{
        struct tm tm;
#ifdef SOLARIS
   return asctime_r(localtime_r(timep, &tm), buf, 256);
#else
   return asctime_r(localtime_r(timep, &tm), buf);
#endif
}

/*
** 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.
** [kridle@xinet.com as of 1996-01-16.]
** 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 (eggert@twinsun.com).
*/

static int
increment_overflow(number, delta)
int * number;
int   delta;
{
   int   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
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
time2(tmp, funcp, offset, okayp, zone)
struct tm * const tmp;
void (* const     funcp) P((const time_t*, long, struct tm*, const char*));
const long     offset;
int * const    okayp;
const char * const   zone;
{
   register const struct state * sp;
   register int         dir;
   register int         bits;
   register int         i, j ;
   register int         saved_seconds;
   time_t            newt;
   time_t            t;
   struct tm         yourtm, mytm;

   *okayp = FALSE;
   yourtm = *tmp;
   if (normalize_overflow(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR))
      return WRONG;
   if (normalize_overflow(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY))
      return WRONG;
   if (normalize_overflow(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR))
      return WRONG;
   /*
   ** Turn yourtm.tm_year into an actual year number for now.
   ** It is converted back to an offset from TM_YEAR_BASE later.
   */
   if (increment_overflow(&yourtm.tm_year, TM_YEAR_BASE))
      return WRONG;
   while (yourtm.tm_mday <= 0) {
      if (increment_overflow(&yourtm.tm_year, -1))
         return WRONG;
      i = yourtm.tm_year + (1 < yourtm.tm_mon);
      yourtm.tm_mday += year_lengths[isleap(i)];
   }
   while (yourtm.tm_mday > DAYSPERLYEAR) {
      i = yourtm.tm_year + (1 < yourtm.tm_mon);
      yourtm.tm_mday -= year_lengths[isleap(i)];
      if (increment_overflow(&yourtm.tm_year, 1))
         return WRONG;
   }
   for ( ; ; ) {
      i = mon_lengths[isleap(yourtm.tm_year)][yourtm.tm_mon];
      if (yourtm.tm_mday <= i)
         break;
      yourtm.tm_mday -= i;
      if (++yourtm.tm_mon >= MONSPERYEAR) {
         yourtm.tm_mon = 0;
         if (increment_overflow(&yourtm.tm_year, 1))
            return WRONG;
      }
   }
   if (increment_overflow(&yourtm.tm_year, -TM_YEAR_BASE))
      return WRONG;
   if (yourtm.tm_year + 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;
   }
   /*
   ** Divide the search space in half
   ** (this works whether time_t is signed or unsigned).
   */
   bits = TYPE_BIT(time_t) - 1;
   /*
   ** If time_t is signed, then 0 is just above the median,
   ** assuming two's complement arithmetic.
   ** If time_t is unsigned, then (1 << bits) is just above the median.
   */
   t = TYPE_SIGNED(time_t) ? 0 : (((time_t) 1) << bits);
   for ( ; ; ) {
      (*funcp)(&t, offset, &mytm, zone);
      dir = tmcomp(&mytm, &yourtm);
      if (dir != 0) {
         if (bits-- < 0)
            return WRONG;
         if (bits < 0)
            --t; /* may be needed if new t is minimal */
         else if (dir > 0)
            t -= ((time_t) 1) << bits;
         else  t += ((time_t) 1) << bits;
         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);
      if (sp == NULL)
         return WRONG;
      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;
            (*funcp)(&newt, offset, &mytm, zone);
            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;
   (*funcp)(&t, offset, tmp, zone);
   *okayp = TRUE;
   return t;
}

static time_t
time1(tmp, funcp, offset, zone)
struct tm * const tmp;
void (* const     funcp) P((const time_t *, long, struct tm *, const char*));
const long     offset;
const char * const   zone;
{
   register time_t         t;
   register const struct state * sp;
   register int         samei, otheri;
   int            okay;

   if (tmp->tm_isdst > 1)
      tmp->tm_isdst = 1;
   t = time2(tmp, funcp, offset, &okay, zone);
#ifdef PCTS
   /*
   ** PCTS code courtesy Grant Sullivan (grant@osf.org).
   */
   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);
   if (sp == NULL)
      return WRONG;
   for (samei = sp->typecnt - 1; samei >= 0; --samei) {
      if (sp->ttis[samei].tt_isdst != tmp->tm_isdst)
         continue;
      for (otheri = sp->typecnt - 1; otheri >= 0; --otheri) {
         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, zone);
         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
ast_mktime(tmp,zone)
struct tm * const tmp;
const char * const   zone;
{
   time_t mktime_return_value;
#ifdef   _THREAD_SAFE
   ast_mutex_lock(&lcl_mutex);
#endif
   ast_tzset(!ast_strlen_zero(zone) ? zone : "/etc/localtime");
   mktime_return_value = time1(tmp, localsub, 0L, !ast_strlen_zero(zone) ? zone : "/etc/localtime");
#ifdef   _THREAD_SAFE
   ast_mutex_unlock(&lcl_mutex);
#endif
   return(mktime_return_value);
}