/* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
/* This file has been modified by DJ Delorie.  These modifications are
** Copyright (C) 1995 DJ Delorie, 24 Kirsten Ave, Rochester NH,
** 03867-2954, USA.
*/

/*
 * Copyright (c) 1987, 1989 Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Arthur David Olson of the National Cancer Institute.
 *
 * Redistribution and use in source and binary forms are permitted provided
 * that: (1) source distributions retain this entire copyright notice and
 * comment, and (2) distributions including binaries display the following
 * acknowledgement:  ``This product includes software developed by the
 * University of California, Berkeley and its contributors'' in the
 * documentation or other materials provided with the distribution and in
 * all advertising materials mentioning features or use of this software.
 * Neither the name of the University nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)ctime.c	5.23 (Berkeley) 6/22/90";
#endif /* LIBC_SCCS and not lint */

/*
** Leap second handling from Bradley White (bww@k.gp.cs.cmu.edu).
** POSIX-style TZ environment variable handling from Guy Harris
** (guy@auspex.com).
*/

#include <libc/stubs.h>
#include <fcntl.h>
#include <time.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <tzfile.h>

#include <libc/unconst.h>

#include "posixrul.h"

#define P(s)		s
#define alloc_size_t	size_t
#define qsort_size_t	size_t
#define fread_size_t	size_t
#define fwrite_size_t	size_t

#define ACCESS_MODE	O_RDONLY|O_BINARY
#define OPEN_MODE	O_RDONLY|O_BINARY

/*
** 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).
*/
static char WILDABBR[] = "   ";

#ifndef TRUE
#define TRUE		1
#define FALSE		0
#endif /* !defined TRUE */

static const char GMT[] = "GMT";

struct ttinfo {		/* time type information */
  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 */
};

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

struct state {
  int leapcnt;
  int timecnt;
  int typecnt;
  int charcnt;
  time_t ats[TZ_MAX_TIMES];
  unsigned char types[TZ_MAX_TIMES];
  struct ttinfo ttis[TZ_MAX_TYPES];
  char chars[(TZ_MAX_CHARS + 1 > sizeof GMT) ? TZ_MAX_CHARS + 1 : sizeof GMT];
  struct lsinfo lsis[TZ_MAX_LEAPS];
};

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

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

/*
** Prototypes for static functions.
*/

static long		detzcode P((const char * codep));
static const char *	getzname P((const char * strp));
static const char *	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));
static void		localsub P((const time_t * timep, long offset,
				struct tm * tmp));
static void		normalize P((int * tensptr, int * unitsptr, int base));
static void		settzname P((void));
static time_t		time1 P((struct tm * tmp, void (* funcp)(const time_t * const, const long, struct tm * const),
				long offset));
static time_t		time2 P((struct tm *tmp, void (* funcp)(const time_t * const, const long, struct tm * const),
				long offset, int * okayp));
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 void		tzsetwall(void);

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

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

static int lcl_is_set;
static int gmt_is_set;

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

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

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

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

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

    tzname[ttisp->tt_isdst] =
      unconst(&sp->chars[ttisp->tt_abbrind], char *);
#if 0
    if (ttisp->tt_isdst)
      _daylight = 1;
    if (i == 0 || !ttisp->tt_isdst)
      _timezone = -(ttisp->tt_gmtoff);
    if (i == 0 || ttisp->tt_isdst)
      _altzone = -(ttisp->tt_gmtoff);
#endif
  }
  /*
   ** And to get the latest zone names into tzname. . .
   */
  for (i = 0; i < sp->timecnt; ++i)
  {
    const struct ttinfo * const ttisp = &sp->ttis[sp->types[i]];

    tzname[ttisp->tt_isdst] = unconst(&sp->chars[ttisp->tt_abbrind], char *);
  }
}

static char *
tzdir(void)
{
  static char dir[80]={0}, *cp;
  if (dir[0] == 0)
  {
    if ((cp = getenv("TZDIR")))
    {
      strcpy(dir, cp);
    }
    else if ((cp = getenv("DJDIR")))
    {
      strcpy(dir, cp);
      strcat(dir, "/zoneinfo");
    }
    else
      strcpy(dir, "./");
  }
  return dir;
}

static int
tzload(const char *name, struct state * const sp)
{
  const char * p;
  int i;
  int fid;
  char fullname[FILENAME_MAX + 1];
  const struct tzhead * tzhp;
  char buf[sizeof *sp + sizeof *tzhp];
  int ttisstdcnt;

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

  if (name[0] == ':')
    ++name;
  if (name[0] != '/')
  {
    if ((p = tzdir()) == NULL)
      return -1;
    if ((strlen(p) + strlen(name) + 1) >= sizeof fullname)
      return -1;
    strcpy(fullname, p);
    strcat(fullname, "/");
    strcat(fullname, name);
    name = fullname;
  }

  if ((fid = open(name, OPEN_MODE)) == -1)
  {
    const char *base = strrchr(name, '/');
    if (base)
      base++;
    else
      base = name;
    if (strcmp(base, "posixrules"))
      return -1;

    /* We've got a built-in copy of posixrules just in case */
    memcpy(buf, _posixrules_data, sizeof(_posixrules_data));
    i = sizeof(_posixrules_data);
  }
  else
  {
    i = read(fid, buf, sizeof buf);
    if (close(fid) != 0 || i < sizeof *tzhp)
      return -1;
  }

  tzhp = (struct tzhead *) buf;
  ttisstdcnt = (int) detzcode(tzhp->tzh_ttisstdcnt);
  sp->leapcnt = (int) detzcode(tzhp->tzh_leapcnt);
  sp->timecnt = (int) detzcode(tzhp->tzh_timecnt);
  sp->typecnt = (int) detzcode(tzhp->tzh_typecnt);
  sp->charcnt = (int) detzcode(tzhp->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))
    return -1;
  if (i < sizeof *tzhp +
      sp->timecnt * (4 + sizeof (char)) +
      sp->typecnt * (4 + 2 * sizeof (char)) +
      sp->charcnt * sizeof (char) +
      sp->leapcnt * 2 * 4 +
      ttisstdcnt * sizeof (char))
    return -1;
  p = buf + sizeof *tzhp;
  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)
  {
    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)
  {
    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)
  {
    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;
    }
  }
  return 0;
}

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

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

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

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

  while ((c = *strp) != '\0' && !isdigit(c) && c != ',' && c != '-' &&
	 c != '+')
    ++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(const char *strp, int * const nump, const int min, const int max)
{
  char c;
  int num;

  if (strp == NULL || !isdigit(*strp))
    return NULL;
  num = 0;
  while ((c = *strp) != '\0' && isdigit(c))
  {
    num = num * 10 + (c - '0');
    if (num > max)
      return NULL;
    ++strp;
  }
  if (num < min)
    return NULL;
  *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(const char *strp, long * const secsp)
{
  int num;

  strp = getnum(strp, &num, 0, HOURSPERDAY);
  if (strp == NULL)
    return NULL;
  *secsp = num * SECSPERHOUR;
  if (*strp == ':')
  {
    ++strp;
    strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
    if (strp == NULL)
      return NULL;
    *secsp += num * SECSPERMIN;
    if (*strp == ':')
    {
      ++strp;
      strp = getnum(strp, &num, 0, SECSPERMIN - 1);
      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(const char *strp, long * const offsetp)
{
  int neg;

  if (*strp == '-')
  {
    neg = 1;
    ++strp;
  }
  else if (isdigit(*strp) || *strp++ == '+')
    neg = 0;
  else
    return NULL; /* illegal offset */
  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(const char *strp, 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 (isdigit(*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 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(const time_t janfirst, const int year, const struct rule * const rulep, const long offset)
{
  int leapyear;
  time_t value=0;
  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(const char *name, struct state * const sp, const int lastditch)
{
  const char * stdname;
  const char * dstname=0;
  int stdlen;
  int dstlen;
  long stdoffset;
  long dstoffset;
  time_t * atp;
  unsigned char * typep;
  char * cp;
  int load_result;

  stdname = name;
  if (lastditch)
  {
    stdlen = strlen(name);	/* length of standard zone name */
    name += stdlen;
    if (stdlen >= sizeof sp->chars)
      stdlen = (sizeof sp->chars) - 1;
  }
  else
  {
    name = getzname(name);
    stdlen = name - stdname;
    if (stdlen < 3)
      return -1;
  }
  if (*name == '\0')
    return -1;
  else
  {
    name = getoffset(name, &stdoffset);
    if (name == NULL)
      return -1;
  }
  load_result = tzload(TZDEFRULES, sp);
  if (load_result != 0)
    sp->leapcnt = 0;		/* so, we're off a little */
  if (*name != '\0')
  {
    dstname = name;
    name = getzname(name);
    dstlen = name - dstname;	/* length of DST zone name */
    if (dstlen < 3)
      return -1;
    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;
      int year;
      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
    {
      int sawstd;
      int sawdst;
      long stdfix;
      long dstfix;
      long oldfix;
      int isdst;
      int i;

      if (*name != '\0')
	return -1;
      if (load_result != 0)
	return -1;
      /*
       ** Compute the difference between the real and
       ** prototype standard and summer time offsets
       ** from GMT, and put the real standard and summer
       ** time offsets into the rules in place of the
       ** prototype offsets.
       */
      sawstd = FALSE;
      sawdst = FALSE;
      stdfix = 0;
      dstfix = 0;
      for (i = 0; i < sp->typecnt; ++i)
      {
	if (sp->ttis[i].tt_isdst)
	{
	  oldfix = dstfix;
	  dstfix =
	    sp->ttis[i].tt_gmtoff + dstoffset;
	  if (sawdst && (oldfix != dstfix))
	    return -1;
	  sp->ttis[i].tt_gmtoff = -dstoffset;
	  sp->ttis[i].tt_abbrind = stdlen + 1;
	  sawdst = TRUE;
	}
	else
	{
	  oldfix = stdfix;
	  stdfix =
	    sp->ttis[i].tt_gmtoff + stdoffset;
	  if (sawstd && (oldfix != stdfix))
	    return -1;
	  sp->ttis[i].tt_gmtoff = -stdoffset;
	  sp->ttis[i].tt_abbrind = 0;
	  sawstd = TRUE;
	}
      }
      /*
       ** Make sure we have both standard and summer time.
       */
      if (!sawdst || !sawstd)
	return -1;
      /*
       ** Now correct the transition times by shifting
       ** them by the difference between the real and
       ** prototype offsets.  Note that this difference
       ** can be different in standard and summer time;
       ** the prototype probably has a 1-hour difference
       ** between standard and summer time, but a different
       ** difference can be specified in TZ.
       */
      isdst = FALSE; /* we start in standard time */
      for (i = 0; i < sp->timecnt; ++i)
      {
	const struct ttinfo * ttisp;

	/*
	 ** 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.
	 */
	ttisp = &sp->ttis[sp->types[i]];
	sp->ats[i] +=
	  (isdst && !ttisp->tt_ttisstd) ?
	    dstfix : stdfix;
	isdst = ttisp->tt_isdst;
      }
    }
  }
  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(struct state * const sp)
{
  if (tzload(GMT, sp) != 0)
    (void) tzparse(GMT, sp, TRUE);
}

void
tzset(void)
{
  const char * name;

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

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

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

  if (!lcl_is_set)
    tzset();
  sp = lclptr;
#ifdef ALL_STATE
  if (sp == NULL)
  {
    gmtsub(timep, offset, tmp);
    return;
  }
#endif /* defined ALL_STATE */
  if (sp->timecnt == 0 || t < sp->ats[0])
  {
    i = 0;
    while (sp->ttis[i].tt_isdst)
      if (++i >= sp->typecnt)
      {
	i = 0;
	break;
      }
  }
  else
  {
    for (i = 1; i < sp->timecnt; ++i)
      if (t < sp->ats[i])
	break;
    i = 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] = unconst(&sp->chars[ttisp->tt_abbrind], char *);
  tmp->tm_zone = unconst(&sp->chars[ttisp->tt_abbrind], char *);
}

struct tm *
localtime(const time_t * const timep)
{
  static struct tm tm;

  localsub(timep, 0L, &tm);
  return &tm;
}

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

static void
gmtsub(const time_t * const timep, const long offset, struct tm * const tmp)
{
  if (!gmt_is_set)
  {
    gmt_is_set = TRUE;
#ifdef ALL_STATE
    gmtptr = (struct state *) malloc(sizeof *gmtptr);
    if (gmtptr != NULL)
#endif /* defined ALL_STATE */
      gmtload(gmtptr);
  }
  timesub(timep, offset, gmtptr, tmp);
  /*
   ** 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
  {
#ifdef ALL_STATE
    if (gmtptr == NULL)
      tmp->TM_ZONE = GMT;
    else
      tmp->TM_ZONE = gmtptr->chars;
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
    tmp->tm_zone = gmtptr->chars;
#endif /* State Farm */
  }
}

struct tm *
gmtime(const time_t * const timep)
{
  static struct tm tm;

  gmtsub(timep, 0L, &tm);
  return &tm;
}

static void
timesub(const time_t * const timep, const long offset, const struct state * const sp, struct tm * const tmp)
{
  const struct lsinfo * lp;
  long days;
  long rem;
  int y;
  int yleap;
  const int * ip;
  long corr;
  int hit;
  int i;

  corr = 0;
  hit = FALSE;
#ifdef ALL_STATE
  i = (sp == NULL) ? 0 : sp->leapcnt;
#endif /* defined ALL_STATE */
#ifndef ALL_STATE
  i = sp->leapcnt;
#endif /* State Farm */
  while (--i >= 0)
  {
    lp = &sp->lsis[i];
    if (*timep >= lp->ls_trans)
    {
      if (*timep == lp->ls_trans)
	hit = ((i == 0 && lp->ls_corr > 0) ||
	       lp->ls_corr > sp->lsis[i - 1].ls_corr);
      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 /* 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);
  tmp->tm_sec = (int) (rem % SECSPERMIN);
  if (hit)
    /*
     ** A positive leap second requires a special
     ** representation.  This uses "... ??:59:60".
     */
    ++(tmp->tm_sec);
  tmp->tm_wday = (int) ((EPOCH_WDAY + days) % DAYSPERWEEK);
  if (tmp->tm_wday < 0)
    tmp->tm_wday += DAYSPERWEEK;
  y = EPOCH_YEAR;
  if (days >= 0)
    for ( ; ; )
    {
      yleap = isleap(y);
      if (days < (long) year_lengths[yleap])
	break;
      ++y;
      days = days - (long) year_lengths[yleap];
    }
  else
    do {
    --y;
    yleap = isleap(y);
    days = days + (long) year_lengths[yleap];
  } while (days < 0);
  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;
  tmp->tm_gmtoff = offset;
}

/*
** A la X3J11
*/

char *
asctime(const struct tm *timeptr)
{
  static const char wday_name[DAYSPERWEEK][3] = {
    "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  };
  static const char mon_name[MONSPERYEAR][3] = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  static char result[26];

  (void) sprintf(result, "%.3s %.3s%3d %02d:%02d:%02d %d\n",
		 wday_name[timeptr->tm_wday],
		 mon_name[timeptr->tm_mon],
		 timeptr->tm_mday, timeptr->tm_hour,
		 timeptr->tm_min, timeptr->tm_sec,
		 TM_YEAR_BASE + timeptr->tm_year);
  return result;
}

char *
ctime(const time_t * const timep)
{
  return asctime(localtime(timep));
}

/*
** 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. (mtxinu!kridle now).
**	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 */

static void
normalize(int * const tensptr, int * const unitsptr, const int base)
{
  if (*unitsptr >= base)
  {
    *tensptr += *unitsptr / base;
    *unitsptr %= base;
  }
  else if (*unitsptr < 0)
  {
    --*tensptr;
    *unitsptr += base;
    if (*unitsptr < 0)
    {
      *tensptr -= 1 + (-*unitsptr) / base;
      *unitsptr = base - (-*unitsptr) % base;
    }
  }
}

static int
tmcomp(const struct tm * const atmp, const struct tm * const btmp)
{
  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(struct tm *tmp, void (*const funcp)(const time_t *const,const long,struct tm *), const long offset, int * const okayp)
{
  const struct state * sp;
  int dir;
  int bits;
  int i, j ;
  int saved_seconds;
  time_t newt;
  time_t t;
  struct tm yourtm, mytm;

  *okayp = FALSE;
  yourtm = *tmp;
  if (yourtm.tm_sec >= SECSPERMIN + 2 || yourtm.tm_sec < 0)
    normalize(&yourtm.tm_min, &yourtm.tm_sec, SECSPERMIN);
  normalize(&yourtm.tm_hour, &yourtm.tm_min, MINSPERHOUR);
  normalize(&yourtm.tm_mday, &yourtm.tm_hour, HOURSPERDAY);
  normalize(&yourtm.tm_year, &yourtm.tm_mon, MONSPERYEAR);
  while (yourtm.tm_mday <= 0)
  {
    --yourtm.tm_year;
    yourtm.tm_mday +=
      year_lengths[isleap(yourtm.tm_year + TM_YEAR_BASE)];
  }
  for ( ; ; )
  {
    i = mon_lengths[isleap(yourtm.tm_year +
			   TM_YEAR_BASE)][yourtm.tm_mon];
    if (yourtm.tm_mday <= i)
      break;
    yourtm.tm_mday -= i;
    if (++yourtm.tm_mon >= MONSPERYEAR)
    {
      yourtm.tm_mon = 0;
      ++yourtm.tm_year;
    }
  }
  saved_seconds = yourtm.tm_sec;
  yourtm.tm_sec = 0;
  /*
   ** Calculate the number of magnitude bits in a time_t
   ** (this works regardless of whether time_t is
   ** signed or unsigned, though lint complains if unsigned).
   */
  for (bits = 0, t = 1; t > 0; ++bits, t <<= 1)
    ;
  /*
   ** If time_t is signed, then 0 is the median value,
   ** if time_t is unsigned, then 1 << bits is median.
   */
  t = (time_t) 1 << bits;
  for ( ; ; )
  {
    (*funcp)(&t, offset, &mytm);
    dir = tmcomp(&mytm, &yourtm);
    if (dir != 0)
    {
      if (bits-- < 0)
	return WRONG;
      if (bits < 0)
	--t;
      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.
     */
    sp = (const struct state *)
      ((funcp == localsub) ? lclptr : gmtptr);
#ifdef ALL_STATE
    if (sp == NULL)
      return WRONG;
#endif /* defined ALL_STATE */
    for (i = 0; i < sp->typecnt; ++i)
    {
      if (sp->ttis[i].tt_isdst != yourtm.tm_isdst)
	continue;
      for (j = 0; j < sp->typecnt; ++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);
	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:
  t += saved_seconds;
  (*funcp)(&t, offset, tmp);
  *okayp = TRUE;
  return t;
}

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

  if (tmp->tm_isdst > 1)
    tmp->tm_isdst = 1;
  t = time2(tmp, funcp, offset, &okay);
  if (okay || tmp->tm_isdst < 0)
    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);
#ifdef ALL_STATE
  if (sp == NULL)
    return WRONG;
#endif /* defined ALL_STATE */
  for (samei = 0; samei < sp->typecnt; ++samei)
  {
    if (sp->ttis[samei].tt_isdst != tmp->tm_isdst)
      continue;
    for (otheri = 0; otheri < sp->typecnt; ++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);
      if (okay)
	return t;
      tmp->tm_sec -= sp->ttis[otheri].tt_gmtoff -
	sp->ttis[samei].tt_gmtoff;
      tmp->tm_isdst = !tmp->tm_isdst;
    }
  }
  return WRONG;
}

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