/* Copyright (C) 1991-2018 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 Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <ctype.h>

#include <errno.h>

#include <libc-lock.h>

#include <stdbool.h>

#include <stddef.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>

#include <timezone/tzfile.h>

#define SECSPERDAY ((time_t) 86400)

char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };

int __daylight = 0;

long int __timezone = 0L;

weak_alias (__tzname, tzname)

weak_alias (__daylight, daylight)

weak_alias (__timezone, timezone)

/* This locks all the state variables in tzfile.c and this file.  */

__libc_lock_define_initialized (static, tzset_lock)

/* This structure contains all the information about a

   timezone given in the POSIX standard TZ envariable.  */

typedef struct

  {

    const char *name;

    /* When to change.  */

    enum { J0, J1, M } type;	/* Interpretation of:  */

    unsigned short int m, n, d;	/* Month, week, day.  */

    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];

static void compute_change (tz_rule *rule, int year) __THROW;

static void tzset_internal (int always);

/* List of buffers containing time zone strings. */

struct tzstring_l

{

  struct tzstring_l *next;

  size_t len;  /* strlen(data) - doesn't count terminating NUL! */

  char data[0];

};

static struct tzstring_l *tzstring_list;

/* Allocate a permanent home for the first LEN characters of S.  It

   will never be moved or deallocated, but may share space with other

   strings.  Don't modify the returned string. */

static char *

__tzstring_len (const char *s, size_t len)

{

  char *p;

  struct tzstring_l *t, *u, *new;

  /* Walk the list and look for a match.  If this string is the same

     as the end of an already-allocated string, it can share space. */

  for (u = t = tzstring_list; t; u = t, t = t->next)

    if (len <= t->len)

      {

	p = &t->data[t->len - len];

	if (memcmp (s, p, len) == 0)

	  return p;

      }

  /* Not found; allocate a new buffer. */

  new = malloc (sizeof (struct tzstring_l) + len + 1);

  if (!new)

    return NULL;

  new->next = NULL;

  new->len = len;

  memcpy (new->data, s, len);

  new->data[len] = '\0';

  if (u)

    u->next = new;

  else

    tzstring_list = new;

  return new->data;

}

/* Allocate a permanent home for S.  It will never be moved or

   deallocated, but may share space with other strings.  Don't modify

   the returned string. */

char *

__tzstring (const char *s)

{

  return __tzstring_len (s, strlen (s));

}

static char *old_tz;

static void

update_vars (void)

{

  __daylight = tz_rules[0].offset != tz_rules[1].offset;

  __timezone = -tz_rules[0].offset;

  __tzname[0] = (char *) tz_rules[0].name;

  __tzname[1] = (char *) tz_rules[1].name;

}

static unsigned int

compute_offset (unsigned int ss, unsigned int mm, unsigned int hh)

{

  if (ss > 59)

    ss = 59;

  if (mm > 59)

    mm = 59;

  if (hh > 24)

    hh = 24;

  return ss + mm * 60 + hh * 60 * 60;

}

/* Parses the time zone name at *TZP, and writes a pointer to an

   interned string to tz_rules[WHICHRULE].name.  On success, advances

   *TZP, and returns true.  Returns false otherwise.  */

static bool

parse_tzname (const char **tzp, int whichrule)

{

  const char *start = *tzp;

  const char *p = start;

  while (('a' <= *p && *p <= 'z')

	 || ('A' <= *p && *p <= 'Z'))

      ++p;

  size_t len = p - start;

  if (len < 3)

    {

      p = *tzp;

      if (__glibc_unlikely (*p++ != '<'))

	return false;

      start = p;

      while (('a' <= *p && *p <= 'z')

	     || ('A' <= *p && *p <= 'Z')

	     || ('0' <= *p && *p <= '9')

	     || *p == '+' || *p == '-')

	++p;

      len = p - start;

      if (*p++ != '>' || len < 3)

	return false;

    }

  const char *name = __tzstring_len (start, len);

  if (name == NULL)

    return false;

  tz_rules[whichrule].name = name;

  *tzp = p;

  return true;

}

/* Parses the time zone offset at *TZP, and writes it to

   tz_rules[WHICHRULE].offset.  Returns true if the parse was

   successful.  */

static bool

parse_offset (const char **tzp, int whichrule)

{

  const char *tz = *tzp;

  if (whichrule == 0

      && (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz))))

    return false;

  long sign;

  if (*tz == '-' || *tz == '+')

    sign = *tz++ == '-' ? 1L : -1L;

  else

    sign = -1L;

  *tzp = tz;

  unsigned short int hh;

  unsigned short mm = 0;

  unsigned short ss = 0;

  int consumed = 0;

  if (sscanf (tz, "%hu%n:%hu%n:%hu%n",

	      &hh, &consumed, &mm, &consumed, &ss, &consumed) > 0)

    tz_rules[whichrule].offset = sign * compute_offset (ss, mm, hh);

  else

    /* Nothing could be parsed. */

    if (whichrule == 0)

      {

	/* Standard time defaults to offset zero.  */

	tz_rules[0].offset = 0;

	return false;

      }

      else

	/* DST defaults to one hour later than standard time.  */

	tz_rules[1].offset = tz_rules[0].offset + (60 * 60);

  *tzp = tz + consumed;

  return true;

}

/* Parses the standard <-> DST rules at *TZP.  Updates

   tz_rule[WHICHRULE].  On success, advances *TZP and returns true.

   Otherwise, returns false.  */

static bool

parse_rule (const char **tzp, int whichrule)

{

  const char *tz = *tzp;

  tz_rule *tzr = &tz_rules[whichrule];

  /* Ignore comma to support string following the incorrect

     specification in early POSIX.1 printings.  */

  tz += *tz == ',';

  /* 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 false;

      unsigned long int d = strtoul (tz, &end, 10);

      if (end == tz || d > 365)

	return false;

      if (tzr->type == J1 && d == 0)

	return false;

      tzr->d = d;

      tz = end;

    }

  else if (*tz == 'M')

    {

      tzr->type = M;

      int consumed;

      if (sscanf (tz, "M%hu.%hu.%hu%n",

		  &tzr->m, &tzr->n, &tzr->d, &consumed) != 3

	  || tzr->m < 1 || tzr->m > 12

	  || tzr->n < 1 || tzr->n > 5 || tzr->d > 6)

	return false;

      tz += consumed;

    }

  else if (*tz == '\0')

    {

      /* Daylight time rules in the U.S. are defined in the U.S. Code,

	 Title 15, Chapter 6, Subchapter IX - Standard Time.  These

	 dates were established by Congress in the Energy Policy Act

	 of 2005 [Pub. L. no. 109-58, 119 Stat 594 (2005)].

	 Below is the equivalent of "M3.2.0,M11.1.0" [/2 not needed

	 since 2:00AM is the default].  */

      tzr->type = M;

      if (tzr == &tz_rules[0])

	{

	  tzr->m = 3;

	  tzr->n = 2;

	  tzr->d = 0;

	}

      else

	{

	  tzr->m = 11;

	  tzr->n = 1;

	  tzr->d = 0;

	}

    }

  else

    return false;

  if (*tz != '\0' && *tz != '/' && *tz != ',')

    return false;

  else if (*tz == '/')

    {

      /* Get the time of day of the change.  */

      int negative;

      ++tz;

      if (*tz == '\0')

	return false;

      negative = *tz == '-';

      tz += negative;

      /* Default to 2:00 AM.  */

      unsigned short hh = 2;

      unsigned short mm = 0;

      unsigned short ss = 0;

      int consumed = 0;

      sscanf (tz, "%hu%n:%hu%n:%hu%n",

	      &hh, &consumed, &mm, &consumed, &ss, &consumed);;

      tz += consumed;

      tzr->secs = (negative ? -1 : 1) * ((hh * 60 * 60) + (mm * 60) + ss);

    }

  else

    /* Default to 2:00 AM.  */

    tzr->secs = 2 * 60 * 60;

  tzr->computed_for = -1;

  *tzp = tz;

  return true;

}

/* Parse the POSIX TZ-style string.  */

void

__tzset_parse_tz (const char *tz)

{

  /* Clear out old state and reset to unnamed UTC.  */

  memset (tz_rules, '\0', sizeof tz_rules);

  tz_rules[0].name = tz_rules[1].name = "";

  /* Get the standard timezone name.  */

  if (parse_tzname (&tz, 0) && parse_offset (&tz, 0))

    {

      /* Get the DST timezone name (if any).  */

      if (*tz != '\0')

	{

	  if (parse_tzname (&tz, 1))

	    {

	      parse_offset (&tz, 1);

	      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)

		    {

		      free (old_tz);

		      old_tz = NULL;

		      return;

		    }

		}

	    }

	  /* Figure out the standard <-> DST rules.  */

	  if (parse_rule (&tz, 0))

	    parse_rule (&tz, 1);

	}

      else

	{

	  /* There is no DST.  */

	  tz_rules[1].name = tz_rules[0].name;

	  tz_rules[1].offset = tz_rules[0].offset;

	}

    }

  update_vars ();

}

/* Interpret the TZ envariable.  */

static void

tzset_internal (int always)

{

  static int is_initialized;

  const char *tz;

  if (is_initialized && !always)

    return;

  is_initialized = 1;

  /* Examine the TZ environment variable.  */

  tz = getenv ("TZ");

  if (tz && *tz == '\0')

    /* User specified the empty string; use UTC explicitly.  */

    tz = "Universal";

  /* A leading colon means "implementation defined syntax".

     We ignore the colon and always use the same algorithm:

     try a data file, and if none exists parse the 1003.1 syntax.  */

  if (tz && *tz == ':')

    ++tz;

  /* Check whether the value changed since the last run.  */

  if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)

    /* No change, simply return.  */

    return;

  if (tz == NULL)

    /* No user specification; use the site-wide default.  */

    tz = TZDEFAULT;

  tz_rules[0].name = NULL;

  tz_rules[1].name = NULL;

  /* Save the value of `tz'.  */

  free (old_tz);

  old_tz = tz ? __strdup (tz) : NULL;

  /* Try to read a data file.  */

  __tzfile_read (tz, 0, NULL);

  if (__use_tzfile)

    return;

  /* No data file found.  Default to UTC if nothing specified.  */

  if (tz == NULL || *tz == '\0'

      || (TZDEFAULT != NULL && strcmp (tz, TZDEFAULT) == 0))

    {

      memset (tz_rules, '\0', sizeof tz_rules);

      tz_rules[0].name = tz_rules[1].name = "UTC";

      if (J0 != 0)

	tz_rules[0].type = tz_rules[1].type = J0;

      tz_rules[0].change = tz_rules[1].change = (time_t) -1;

      update_vars ();

      return;

    }

  __tzset_parse_tz (tz);

}

/* 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.  */

static void

compute_change (tz_rule *rule, int year)

{

  time_t t;

  if (year != -1 && rule->computed_for == year)

    /* Operations on times in 2 BC will be slower.  Oh well.  */

    return;

  /* First set T to January 1st, 0:00:00 GMT in YEAR.  */

  if (year > 1970)

    t = ((year - 1970) * 365

	 + /* Compute the number of leapdays between 1970 and YEAR

	      (exclusive).  There is a leapday every 4th year ...  */

	 + ((year - 1) / 4 - 1970 / 4)

	 /* ... except every 100th year ... */

	 - ((year - 1) / 100 - 1970 / 100)

	 /* ... but still every 400th year.  */

	 + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY;

  else

    t = 0;

  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.  */

      {

	unsigned int i;

	int d, m1, yy0, yy1, yy2, dow;

	const unsigned short int *myday =

	  &__mon_yday[__isleap (year)][rule->m];

	/* First add SECSPERDAY for each day in months before M.  */

	t += myday[-1] * 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 >= (int) myday[0] - myday[-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;

}

/* Figure out the correct timezone for TM and set `__tzname',

   `__timezone', and `__daylight' accordingly.  */

void

__tz_compute (time_t timer, struct tm *tm, int use_localtime)

{

  compute_change (&tz_rules[0], 1900 + tm->tm_year);

  compute_change (&tz_rules[1], 1900 + tm->tm_year);

  if (use_localtime)

    {

      int isdst;

      /* We have to distinguish between northern and southern

	 hemisphere.  For the latter the daylight saving time

	 ends in the next year.  */

      if (__builtin_expect (tz_rules[0].change

			    > tz_rules[1].change, 0))

	isdst = (timer < tz_rules[1].change

		 || timer >= tz_rules[0].change);

      else

	isdst = (timer >= tz_rules[0].change

		 && timer < tz_rules[1].change);

      tm->tm_isdst = isdst;

      tm->tm_zone = __tzname[isdst];

      tm->tm_gmtoff = tz_rules[isdst].offset;

    }

}

/* Reinterpret the TZ environment variable and set `tzname'.  */

#undef tzset

void

__tzset (void)

{

  __libc_lock_lock (tzset_lock);

  tzset_internal (1);

  if (!__use_tzfile)

    {

      /* Set `tzname'.  */

      __tzname[0] = (char *) tz_rules[0].name;

      __tzname[1] = (char *) tz_rules[1].name;

    }

  __libc_lock_unlock (tzset_lock);

}

weak_alias (__tzset, tzset)

/* Return the `struct tm' representation of *TIMER in the local timezone.

   Use local time if USE_LOCALTIME is nonzero, UTC otherwise.  */

struct tm *

__tz_convert (const time_t *timer, int use_localtime, struct tm *tp)

{

  long int leap_correction;

  int leap_extra_secs;

  if (timer == NULL)

    {

      __set_errno (EINVAL);

      return NULL;

    }

  __libc_lock_lock (tzset_lock);

  /* Update internal database according to current TZ setting.

     POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.

     This is a good idea since this allows at least a bit more parallelism.  */

  tzset_internal (tp == &_tmbuf && use_localtime);

  if (__use_tzfile)

    __tzfile_compute (*timer, use_localtime, &leap_correction,

		      &leap_extra_secs, tp);

  else

    {

      if (! __offtime (timer, 0, tp))

	tp = NULL;

      else

	__tz_compute (*timer, tp, use_localtime);

      leap_correction = 0L;

      leap_extra_secs = 0;

    }

  __libc_lock_unlock (tzset_lock);

  if (tp)

    {

      if (! use_localtime)

	{

	  tp->tm_isdst = 0;

	  tp->tm_zone = "GMT";

	  tp->tm_gmtoff = 0L;

	}

      if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp))

        tp->tm_sec += leap_extra_secs;

      else

	tp = NULL;

    }

  return tp;

}

libc_freeres_fn (free_mem)

{

  while (tzstring_list != NULL)

    {

      struct tzstring_l *old = tzstring_list;

      tzstring_list = tzstring_list->next;

      free (old);

    }

  free (old_tz);

  old_tz = NULL;

}