text: /* Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
  This file is part of the GNU C Library.
  
  The GNU C Library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public License as
  published by the Free Software Foundation; either version 2 of the
  License, or (at your option) any later version.
  
  The GNU C Library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Library General Public License for more details.
  
  You should have received a copy of the GNU Library General Public
  License along with the GNU C Library; see the file COPYING.LIB.  If
  not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  Cambridge, MA 02139, USA.  */
  
  #include <ansidecl.h>
  #include <localeinfo.h>
  #include <ctype.h>
  #include <stddef.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <time.h>
  
  /* Defined in mktime.c.  */
  extern CONST unsigned short int __mon_lengths[2][12];
  
  #define NOID
  #include "tzfile.h"
  
  extern int __use_tzfile;
  extern void EXFUN(__tzfile_read, (CONST char *file));
  extern void EXFUN(__tzfile_default, (char *std AND char *dst AND
  				     long int stdoff AND long int dstoff));
  extern int EXFUN(__tzfile_compute, (time_t, struct tm));
  
  #ifndef	HAVE_GNU_LD
  #define	__tzname	tzname
  #define	__daylight	daylight
  #define	__timezone	timezone
  #endif
  
  char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  int __daylight = 0;
  long int __timezone = 0L;
  
  
  #define	min(a, b)	((a) < (b) ? (a) : (b))
  #define	max(a, b)	((a) > (b) ? (a) : (b))
  #define	sign(x)		((x) < 0 ? -1 : 1)
  
  
  /* This structure contains all the information about a
     timezone given in the POSIX standard TZ envariable.  */
  typedef struct
    {
      char *name;
  
      /* When to change.  */
      enum { J0, J1, M } type;	/* Interpretation of:  */
      unsigned short int m, n, d;	/* Month, week, day.  */
      unsigned int secs;		/* Time of day.  */
  
      long int offset;		/* Seconds east of GMT (west if < 0).  */
  
      /* We cache the computed time of change for a
         given year so we don't have to recompute it.  */
      time_t change;	/* When to change to this zone.  */
      int computed_for;	/* Year above is computed for.  */
    } tz_rule;
  
  /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  static tz_rule tz_rules[2];
  
  int __tzset_run = 0;
  
  /* Interpret the TZ envariable.  */
  void
  DEFUN_VOID(__tzset)
  {
    register CONST char *tz;
    register size_t l;
    unsigned short int hh, mm, ss;
    unsigned short int whichrule;
  
    /* Free old storage.  */
    if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
      free((PTR) tz_rules[0].name);
    if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
        tz_rules[1].name != tz_rules[0].name)
      free((PTR) tz_rules[1].name);
  
    tz = getenv("TZ");
  
    if (tz != NULL && *tz == ':')
      {
        __tzfile_read(tz + 1);
        if (__use_tzfile)
  	{
  	  __tzset_run = 1;
  	  return;
  	}
        else
  	tz = NULL;
      }
  
    if (tz == NULL || *tz == '\0')
      tz = _time_info->tz;
    if (tz == NULL || *tz == '\0')
      {
        __tzfile_read((char *) NULL);
        if (!__use_tzfile)
  	{
  	  size_t len = strlen(_time_info->ut0) + 1;
  	  tz_rules[0].name = (char *) malloc(len);
  	  if (tz_rules[0].name == NULL)
  	    return;
  	  tz_rules[1].name = (char *) malloc(len);
  	  if (tz_rules[1].name == NULL)
  	    return;
  	  memcpy((PTR) tz_rules[0].name, _time_info->ut0, len);
  	  memcpy((PTR) tz_rules[1].name, _time_info->ut0, len);
  	  tz_rules[0].type = tz_rules[1].type = J0;
  	  tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
  	  tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
  	  tz_rules[0].secs = tz_rules[1].secs = 0;
  	  tz_rules[0].offset = tz_rules[1].offset = 0L;
  	  tz_rules[0].change = tz_rules[1].change = (time_t) -1;
  	  tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
  	}
        __tzset_run = 1;
        return;
      }
  
    /* Get the standard timezone name.  */
    tz_rules[0].name = (char *) malloc(strlen(tz) + 1);
    if (tz_rules[0].name == NULL)
      return;
  
    if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
        (l = strlen(tz_rules[0].name)) < 3)
      return;
  
    tz_rules[0].name = (char *) realloc((PTR) tz_rules[0].name, l + 1);
    if (tz_rules[0].name == NULL)
      return;
  
    tz += l;
  
    /* Figure out the standard offset from GMT.  */
    if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
      return;
  
    if (*tz == '-' || *tz == '+')
      tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
    else
      tz_rules[0].offset = -1L;
    switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
      {
      default:
        return;
      case 1:
        mm = 0;
      case 2:
        ss = 0;
      case 3:
        break;
      }
    tz_rules[0].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
  			 (min(hh, 12) * 60 * 60));
  
    for (l = 0; l < 3; ++l)
      {
        while (isdigit(*tz))
  	++tz;
        if (l < 2 && *tz == ':')
  	++tz;
      }
  
    /* Get the DST timezone name (if any).  */
    if (*tz == '\0')
      tz_rules[1].name = (char *) "";
    else
      {
        tz_rules[1].name = (char *) malloc(strlen(tz) + 1);
        if (tz_rules[1].name == NULL)
  	return;
        if (sscanf(tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
  	  (l = strlen(tz_rules[1].name)) < 3)
  	return;
        tz_rules[1].name = (char *) realloc((PTR) tz_rules[1].name, l + 1);
        if (tz_rules[1].name == NULL)
  	return;
      }
  
    tz += l;
  
    /* Figure out the DST offset from GMT.  */
    if (*tz == '-' || *tz == '+')
      tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
    else
      tz_rules[1].offset = -1L;
  
    switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
      {
      default:
        /* Default to one hour later than standard time.  */
        tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
        break;
  
      case 1:
        mm = 0;
      case 2:
        ss = 0;
      case 3:
        tz_rules[1].offset *= (min(ss, 59) + (min(mm, 59) * 60) +
  			     (min(hh, 12) * (60 * 60)));
        break;
      }
    for (l = 0; l < 3; ++l)
      {
        while (isdigit(*tz))
  	++tz;
        if (l < 2 && *tz == ':')
  	++tz;
      }
  
    /* If no standard or DST offset was given, default to GMT
       for standard and one hour later than standard for DST.  */
    if (*tz_rules[0].name == '\0')
      tz_rules[0].offset = 0L;
    if (*tz_rules[1].name == '\0')
      tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
  
    if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
      {
        /* There is no rule.  See if there is a default rule file.  */
        __tzfile_default (tz_rules[0].name, tz_rules[1].name,
  			tz_rules[0].offset, tz_rules[1].offset);
        if (__use_tzfile)
  	{
  	  __tzset_run = 1;
  	  return;
  	}
      }
  
    /* Figure out the standard <-> DST rules.  */
    for (whichrule = 0; whichrule < 2; ++whichrule)
      {
        register tz_rule *tzr = &tz_rules[whichrule];
        
        if (*tz != '\0' && *tz == ',')
  	{
  	  ++tz;
  	  if (*tz == '\0')
  	    return;
  	}
        
        /* Get the date of the change.  */
        if (*tz == 'J' || isdigit(*tz))
  	{
  	  char *end;
  	  tzr->type = *tz == 'J' ? J1 : J0;
  	  if (tzr->type == J1 && !isdigit(*++tz))
  	    return;
  	  tzr->d = (unsigned short int) strtoul(tz, &end, 10);
  	  if (end == tz || tzr->d > 365)
  	    return;
  	  else if (tzr->type == J1 && tzr->d == 0)
  	    return;
  	  tz = end;
  	}
        else if (*tz == 'M')
  	{
  	  int n;
  	  tzr->type = M;
  	  if (sscanf (tz, "M%hu.%hu.%hu%n",
  		      &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
  	      tzr->m < 1 || tzr->m > 12 ||
  	      tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
  	    return;
  	  tz += n;
  	}
        else if (*tz == '\0')
  	{
  	  /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
  	  tzr->type = M;
  	  if (tzr == &tz_rules[0])
  	    {
  	      tzr->m = 4;
  	      tzr->n = 1;
  	      tzr->d = 0;
  	    }
  	  else
  	    {
  	      tzr->m = 10;
  	      tzr->n = 5;
  	      tzr->d = 0;
  	    }
  	}
        else
  	return;
        
        if (*tz != '\0' && *tz != '/' && *tz != ',')
  	return;
        else if (*tz == '/')
  	{
  	  /* Get the time of day of the change.  */
  	  ++tz;
  	  if (*tz == '\0')
  	    return;
  	  switch (sscanf(tz, "%hu:%hu:%hu", &hh, &mm, &ss))
  	    {
  	    default:
  	      return;
  	    case 1:
  	      mm = 0;
  	    case 2:
  	      ss = 0;
  	    case 3:
  	      break;
  	    }
  	  for (l = 0; l < 3; ++l)
  	    {
  	      while (isdigit(*tz))
  		++tz;
  	      if (l < 2 && *tz == ':')
  		++tz;
  	    }
  	  tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
  	}
        else
  	/* Default to 2:00 AM.  */
  	tzr->secs = 2 * 60 * 60;
  
        tzr->computed_for = -1;
      }
  
    __tzset_run = 1;
  }
  
  /* Maximum length of a timezone name.  __tz_compute keeps this up to date
     (never decreasing it) when ! __use_tzfile.
     tzfile.c keeps it up to date when __use_tzfile.  */
  long int __tzname_cur_max;
  
  long int
  DEFUN_VOID(__tzname_max)
  {
    if (! __tzset_run)
      __tzset ();
  
    return __tzname_cur_max;
  }
  
  /* Figure out the exact time (as a time_t) in YEAR
     when the change described by RULE will occur and
     put it in RULE->change, saving YEAR in RULE->computed_for.
     Return nonzero if successful, zero on failure.  */
  static int
  DEFUN(compute_change, (rule, year), tz_rule *rule AND int year)
  {
    register time_t t;
    int y;
  
    if (year != -1 && rule->computed_for == year)
      /* Operations on times in 1969 will be slower.  Oh well.  */
      return 1;
       
    /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
    t = 0;
    for (y = 1970; y < year; ++y)
      t += SECSPERDAY * (__isleap (y) ? 366 : 365);
  
    switch (rule->type)
      {
      case J1:
        /* 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.  */
        t += (rule->d - 1) * SECSPERDAY;
        if (rule->d >= 60 && __isleap (year))
  	t += SECSPERDAY;
        break;
  
      case J0:
        /* n - Day of year.
  	 Just add SECSPERDAY times the day number to the time of Jan 1st.  */
        t += rule->d * SECSPERDAY;
        break;
  
      case M:
        /* Mm.n.d - Nth "Dth day" of month M.  */
        {
  	register int i, d, m1, yy0, yy1, yy2, dow;
  
  	/* First add SECSPERDAY for each day in months before M.  */
  	for (i = 0; i < rule->m - 1; ++i)
  	  t += __mon_lengths[__isleap (year)][i] * SECSPERDAY;
  
  	/* Use Zeller's Congruence to get day-of-week of first day of month. */
  	m1 = (rule->m + 9) % 12 + 1;
  	yy0 = (rule->m <= 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 += 7;
  
  	/* 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 = rule->d - dow;
  	if (d < 0)
  	  d += 7;
  	for (i = 1; i < rule->n; ++i)
  	  {
  	    if (d + 7 >= __mon_lengths[__isleap (year)][rule->m - 1])
  	      break;
  	    d += 7;
  	  }
  
  	/* D is the day-of-month (zero-origin) of the day we want.  */
  	t += d * SECSPERDAY;
        }
        break;
      }
  
    /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
       Just add the time of day and local offset from GMT, and we're done.  */
  
    rule->change = t + rule->offset + rule->secs;
    rule->computed_for = year;
    return 1;
  }
  
  
  /* Figure out the correct timezone for *TIMER and TM (which must be the same)
     and set `__tzname', `__timezone', and `__daylight' accordingly.
     Return nonzero on success, zero on failure.  */
  int
  DEFUN(__tz_compute, (timer, tm),
        time_t timer AND const struct tm *tm)
  {
    if (! __tzset_run)
      __tzset ();
  
    if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
        ! compute_change (&tz_rules[1], 1900 + tm->tm_year))
      return 0;
  
    __daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
    __timezone = tz_rules[__daylight ? 1 : 0].offset;
    __tzname[0] = (char *) tz_rules[0].name;
    __tzname[1] = (char *) tz_rules[1].name;
  
    {
      /* Keep __tzname_cur_max up to date.  */
      size_t len0 = strlen (__tzname[0]);
      size_t len1 = strlen (__tzname[1]);
      if (len0 > __tzname_cur_max)
        __tzname_cur_max = len0;
      if (len1 > __tzname_cur_max)
        __tzname_cur_max = len1;
    }
  
    return 1;
  }
  