/src/postgres/src/timezone/localtime.c

Source
/* Convert timestamp from pg_time_t to struct pg_tm.  */

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

/*
 * Leap second handling from Bradley White.
 * POSIX-style TZ environment variable handling from Guy Harris.
 */

/* this file needs to build in both frontend and backend contexts */
#include "c.h"

#include <fcntl.h>

#include "datatype/timestamp.h"
#include "pgtz.h"

#include "private.h"
#include "tzfile.h"


#ifndef WILDABBR
/*
 * Someone might make incorrect use of a time zone abbreviation:
 *  1.  They might reference tzname[0] before calling tzset (explicitly
 *    or implicitly).
 *  2.  They might reference tzname[1] before calling tzset (explicitly
 *    or implicitly).
 *  3.  They might reference tzname[1] after setting to a time zone
 *    in which Daylight Saving Time is never observed.
 *  4.  They might reference tzname[0] after setting to a time zone
 *    in which Standard Time is never observed.
 *  5.  They might reference tm.tm_zone after calling offtime.
 * What's best to do in the above cases is open to debate;
 * for now, we just set things up so that in any of the five cases
 * WILDABBR is used. Another possibility: initialize tzname[0] to the
 * string "tzname[0] used before set", and similarly for the other cases.
 * And another: initialize tzname[0] to "ERA", with an explanation in the
 * manual page of what this "time zone abbreviation" means (doing this so
 * that tzname[0] has the "normal" length of three characters).
 */
#define WILDABBR  "   "
#endif              /* !defined WILDABBR */

static const char wildabbr[] = WILDABBR;

static const char gmt[] = "GMT";

/*
 * The DST rules to use if a POSIX TZ string has no rules.
 * Default to US rules as of 2017-05-07.
 * POSIX does not specify the default DST rules;
 * for historical reasons, US rules are a common default.
 */
#define TZDEFRULESTRING ",M3.2.0,M11.1.0"

/* structs ttinfo, lsinfo, state have been moved to pgtz.h */

enum r_type
{
  JULIAN_DAY,         /* Jn = Julian day */
  DAY_OF_YEAR,        /* n = day of year */
  MONTH_NTH_DAY_OF_WEEK,    /* Mm.n.d = month, week, day of week */
};

struct rule
{
  enum r_type r_type;     /* type of rule */
  int     r_day;      /* day number of rule */
  int     r_week;     /* week number of rule */
  int     r_mon;      /* month number of rule */
  int32   r_time;     /* transition time of rule */
};

/*
 * Prototypes for static functions.
 */

static struct pg_tm *gmtsub(pg_time_t const *timep, int32 offset,
              struct pg_tm *tmp);
static bool increment_overflow(int *ip, int j);
static bool increment_overflow_time(pg_time_t *tp, int32 j);
static int64 leapcorr(struct state const *sp, pg_time_t t);
static struct pg_tm *timesub(pg_time_t const *timep,
               int32 offset, struct state const *sp,
               struct pg_tm *tmp);
static bool typesequiv(struct state const *sp, int a, int b);


/*
 * Section 4.12.3 of X3.159-1989 requires that
 *  Except for the strftime function, these functions [asctime,
 *  ctime, gmtime, localtime] return values in one of two static
 *  objects: a broken-down time structure and an array of char.
 * Thanks to Paul Eggert for noting this.
 */

static struct pg_tm tm;

/* Initialize *S to a value based on UTOFF, ISDST, and DESIGIDX.  */
static void
init_ttinfo(struct ttinfo *s, int32 utoff, bool isdst, int desigidx)
{
  s->tt_utoff = utoff;
  s->tt_isdst = isdst;
  s->tt_desigidx = desigidx;
  s->tt_ttisstd = false;
  s->tt_ttisut = false;
}

static int32
detzcode(const char *const codep)
{
  int32   result;
  int     i;
  int32   one = 1;
  int32   halfmaxval = one << (32 - 2);
  int32   maxval = halfmaxval - 1 + halfmaxval;
  int32   minval = -1 - maxval;

  result = codep[0] & 0x7f;
  for (i = 1; i < 4; ++i)
    result = (result << 8) | (codep[i] & 0xff);

  if (codep[0] & 0x80)
  {
    /*
     * Do two's-complement negation even on non-two's-complement machines.
     * If the result would be minval - 1, return minval.
     */
    result -= !TWOS_COMPLEMENT(int32) && result != 0;
    result += minval;
  }
  return result;
}

static int64
detzcode64(const char *const codep)
{
  uint64    result;
  int     i;
  int64   one = 1;
  int64   halfmaxval = one << (64 - 2);
  int64   maxval = halfmaxval - 1 + halfmaxval;
  int64   minval = -TWOS_COMPLEMENT(int64) - maxval;

  result = codep[0] & 0x7f;
  for (i = 1; i < 8; ++i)
    result = (result << 8) | (codep[i] & 0xff);

  if (codep[0] & 0x80)
  {
    /*
     * Do two's-complement negation even on non-two's-complement machines.
     * If the result would be minval - 1, return minval.
     */
    result -= !TWOS_COMPLEMENT(int64) && result != 0;
    result += minval;
  }
  return result;
}

static bool
differ_by_repeat(const pg_time_t t1, const pg_time_t t0)
{
  if (TYPE_BIT(pg_time_t) - TYPE_SIGNED(pg_time_t) < SECSPERREPEAT_BITS)
    return 0;
  return t1 - t0 == SECSPERREPEAT;
}

/* Input buffer for data read from a compiled tz file.  */
union input_buffer
{
  /* The first part of the buffer, interpreted as a header.  */
  struct tzhead tzhead;

  /* The entire buffer.  */
  char    buf[2 * sizeof(struct tzhead) + 2 * sizeof(struct state)
          + 4 * TZ_MAX_TIMES];
};

/* Local storage needed for 'tzloadbody'.  */
union local_storage
{
  /* The results of analyzing the file's contents after it is opened.  */
  struct file_analysis
  {
    /* The input buffer.  */
    union input_buffer u;

    /* A temporary state used for parsing a TZ string in the file.  */
    struct state st;
  }     u;

  /* We don't need the "fullname" member */
};

/* Load tz data from the file named NAME into *SP.  Read extended
 * format if DOEXTEND.  Use *LSP for temporary storage.  Return 0 on
 * success, an errno value on failure.
 * PG: If "canonname" is not NULL, then on success the canonical spelling of
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 */
static int
tzloadbody(char const *name, char *canonname, struct state *sp, bool doextend,
       union local_storage *lsp)
{
  int     i;
  int     fid;
  int     stored;
  ssize_t   nread;
  union input_buffer *up = &lsp->u.u;
  int     tzheadsize = sizeof(struct tzhead);

  sp->goback = sp->goahead = false;

  if (!name)
  {
    name = TZDEFAULT;
    if (!name)
      return EINVAL;
  }

  if (name[0] == ':')
    ++name;

  fid = pg_open_tzfile(name, canonname);
  if (fid < 0)
    return ENOENT;     /* pg_open_tzfile may not set errno */

  nread = read(fid, up->buf, sizeof up->buf);
  if (nread < tzheadsize)
  {
    int     err = nread < 0 ? errno : EINVAL;

    close(fid);
    return err;
  }
  if (close(fid) < 0)
    return errno;
  for (stored = 4; stored <= 8; stored *= 2)
  {
    int32   ttisstdcnt = detzcode(up->tzhead.tzh_ttisstdcnt);
    int32   ttisutcnt = detzcode(up->tzhead.tzh_ttisutcnt);
    int64   prevtr = 0;
    int32   prevcorr = 0;
    int32   leapcnt = detzcode(up->tzhead.tzh_leapcnt);
    int32   timecnt = detzcode(up->tzhead.tzh_timecnt);
    int32   typecnt = detzcode(up->tzhead.tzh_typecnt);
    int32   charcnt = detzcode(up->tzhead.tzh_charcnt);
    char const *p = up->buf + tzheadsize;

    /*
     * Although tzfile(5) currently requires typecnt to be nonzero,
     * support future formats that may allow zero typecnt in files that
     * have a TZ string and no transitions.
     */
    if (!(0 <= leapcnt && leapcnt < TZ_MAX_LEAPS
        && 0 <= typecnt && typecnt < TZ_MAX_TYPES
        && 0 <= timecnt && timecnt < TZ_MAX_TIMES
        && 0 <= charcnt && charcnt < TZ_MAX_CHARS
        && (ttisstdcnt == typecnt || ttisstdcnt == 0)
        && (ttisutcnt == typecnt || ttisutcnt == 0)))
      return EINVAL;
    if (nread
      < (tzheadsize   /* struct tzhead */
         + timecnt * stored /* ats */
         + timecnt    /* types */
         + typecnt * 6  /* ttinfos */
         + charcnt    /* chars */
         + leapcnt * (stored + 4) /* lsinfos */
         + ttisstdcnt   /* ttisstds */
         + ttisutcnt)) /* ttisuts */
      return EINVAL;
    sp->leapcnt = leapcnt;
    sp->timecnt = timecnt;
    sp->typecnt = typecnt;
    sp->charcnt = charcnt;

    /*
     * Read transitions, discarding those out of pg_time_t range. But
     * pretend the last transition before TIME_T_MIN occurred at
     * TIME_T_MIN.
     */
    timecnt = 0;
    for (i = 0; i < sp->timecnt; ++i)
    {
      int64   at
      = stored == 4 ? detzcode(p) : detzcode64(p);

      sp->types[i] = at <= TIME_T_MAX;
      if (sp->types[i])
      {
        pg_time_t attime
        = ((TYPE_SIGNED(pg_time_t) ? at < TIME_T_MIN : at < 0)
           ? TIME_T_MIN : at);

        if (timecnt && attime <= sp->ats[timecnt - 1])
        {
          if (attime < sp->ats[timecnt - 1])
            return EINVAL;
          sp->types[i - 1] = 0;
          timecnt--;
        }
        sp->ats[timecnt++] = attime;
      }
      p += stored;
    }

    timecnt = 0;
    for (i = 0; i < sp->timecnt; ++i)
    {
      unsigned char typ = *p++;

      if (sp->typecnt <= typ)
        return EINVAL;
      if (sp->types[i])
        sp->types[timecnt++] = typ;
    }
    sp->timecnt = timecnt;
    for (i = 0; i < sp->typecnt; ++i)
    {
      struct ttinfo *ttisp;
      unsigned char isdst,
            desigidx;

      ttisp = &sp->ttis[i];
      ttisp->tt_utoff = detzcode(p);
      p += 4;
      isdst = *p++;
      if (!(isdst < 2))
        return EINVAL;
      ttisp->tt_isdst = isdst;
      desigidx = *p++;
      if (!(desigidx < sp->charcnt))
        return EINVAL;
      ttisp->tt_desigidx = desigidx;
    }
    for (i = 0; i < sp->charcnt; ++i)
      sp->chars[i] = *p++;
    sp->chars[i] = '\0';  /* ensure '\0' at end */

    /* Read leap seconds, discarding those out of pg_time_t range.  */
    leapcnt = 0;
    for (i = 0; i < sp->leapcnt; ++i)
    {
      int64   tr = stored == 4 ? detzcode(p) : detzcode64(p);
      int32   corr = detzcode(p + stored);

      p += stored + 4;
      /* Leap seconds cannot occur before the Epoch.  */
      if (tr < 0)
        return EINVAL;
      if (tr <= TIME_T_MAX)
      {
        /*
         * Leap seconds cannot occur more than once per UTC month, and
         * UTC months are at least 28 days long (minus 1 second for a
         * negative leap second).  Each leap second's correction must
         * differ from the previous one's by 1 second.
         */
        if (tr - prevtr < 28 * SECSPERDAY - 1
          || (corr != prevcorr - 1 && corr != prevcorr + 1))
          return EINVAL;
        sp->lsis[leapcnt].ls_trans = prevtr = tr;
        sp->lsis[leapcnt].ls_corr = prevcorr = corr;
        leapcnt++;
      }
    }
    sp->leapcnt = leapcnt;

    for (i = 0; i < sp->typecnt; ++i)
    {
      struct ttinfo *ttisp;

      ttisp = &sp->ttis[i];
      if (ttisstdcnt == 0)
        ttisp->tt_ttisstd = false;
      else
      {
        if (*p != true && *p != false)
          return EINVAL;
        ttisp->tt_ttisstd = *p++;
      }
    }
    for (i = 0; i < sp->typecnt; ++i)
    {
      struct ttinfo *ttisp;

      ttisp = &sp->ttis[i];
      if (ttisutcnt == 0)
        ttisp->tt_ttisut = false;
      else
      {
        if (*p != true && *p != false)
          return EINVAL;
        ttisp->tt_ttisut = *p++;
      }
    }

    /*
     * If this is an old file, we're done.
     */
    if (up->tzhead.tzh_version[0] == '\0')
      break;
    nread -= p - up->buf;
    memmove(up->buf, p, nread);
  }
  if (doextend && nread > 2 &&
    up->buf[0] == '\n' && up->buf[nread - 1] == '\n' &&
    sp->typecnt + 2 <= TZ_MAX_TYPES)
  {
    struct state *ts = &lsp->u.st;

    up->buf[nread - 1] = '\0';
    if (tzparse(&up->buf[1], ts, false))
    {
      /*
       * Attempt to reuse existing abbreviations. Without this,
       * America/Anchorage would be right on the edge after 2037 when
       * TZ_MAX_CHARS is 50, as sp->charcnt equals 40 (for LMT AST AWT
       * APT AHST AHDT YST AKDT AKST) and ts->charcnt equals 10 (for
       * AKST AKDT).  Reusing means sp->charcnt can stay 40 in this
       * example.
       */
      int     gotabbr = 0;
      int     charcnt = sp->charcnt;

      for (i = 0; i < ts->typecnt; i++)
      {
        char     *tsabbr = ts->chars + ts->ttis[i].tt_desigidx;
        int     j;

        for (j = 0; j < charcnt; j++)
          if (strcmp(sp->chars + j, tsabbr) == 0)
          {
            ts->ttis[i].tt_desigidx = j;
            gotabbr++;
            break;
          }
        if (!(j < charcnt))
        {
          int     tsabbrlen = strlen(tsabbr);

          if (j + tsabbrlen < TZ_MAX_CHARS)
          {
            strcpy(sp->chars + j, tsabbr);
            charcnt = j + tsabbrlen + 1;
            ts->ttis[i].tt_desigidx = j;
            gotabbr++;
          }
        }
      }
      if (gotabbr == ts->typecnt)
      {
        sp->charcnt = charcnt;

        /*
         * Ignore any trailing, no-op transitions generated by zic as
         * they don't help here and can run afoul of bugs in zic 2016j
         * or earlier.
         */
        while (1 < sp->timecnt
             && (sp->types[sp->timecnt - 1]
               == sp->types[sp->timecnt - 2]))
          sp->timecnt--;

        for (i = 0; i < ts->timecnt; i++)
          if (sp->timecnt == 0
            || (sp->ats[sp->timecnt - 1]
              < ts->ats[i] + leapcorr(sp, ts->ats[i])))
            break;
        while (i < ts->timecnt
             && sp->timecnt < TZ_MAX_TIMES)
        {
          sp->ats[sp->timecnt]
            = ts->ats[i] + leapcorr(sp, ts->ats[i]);
          sp->types[sp->timecnt] = (sp->typecnt
                        + ts->types[i]);
          sp->timecnt++;
          i++;
        }
        for (i = 0; i < ts->typecnt; i++)
          sp->ttis[sp->typecnt++] = ts->ttis[i];
      }
    }
  }
  if (sp->typecnt == 0)
    return EINVAL;
  if (sp->timecnt > 1)
  {
    for (i = 1; i < sp->timecnt; ++i)
      if (typesequiv(sp, sp->types[i], sp->types[0]) &&
        differ_by_repeat(sp->ats[i], sp->ats[0]))
      {
        sp->goback = true;
        break;
      }
    for (i = sp->timecnt - 2; i >= 0; --i)
      if (typesequiv(sp, sp->types[sp->timecnt - 1],
               sp->types[i]) &&
        differ_by_repeat(sp->ats[sp->timecnt - 1],
                 sp->ats[i]))
      {
        sp->goahead = true;
        break;
      }
  }

  /*
   * Infer sp->defaulttype from the data.  Although this default type is
   * always zero for data from recent tzdb releases, things are trickier for
   * data from tzdb 2018e or earlier.
   *
   * The first set of heuristics work around bugs in 32-bit data generated
   * by tzdb 2013c or earlier.  The workaround is for zones like
   * Australia/Macquarie where timestamps before the first transition have a
   * time type that is not the earliest standard-time type.  See:
   * https://mm.icann.org/pipermail/tz/2013-May/019368.html
   */

  /*
   * If type 0 is unused in transitions, it's the type to use for early
   * times.
   */
  for (i = 0; i < sp->timecnt; ++i)
    if (sp->types[i] == 0)
      break;
  i = i < sp->timecnt ? -1 : 0;

  /*
   * Absent the above, if there are transition times and the first
   * transition is to a daylight time find the standard type less than and
   * closest to the type of the first transition.
   */
  if (i < 0 && sp->timecnt > 0 && sp->ttis[sp->types[0]].tt_isdst)
  {
    i = sp->types[0];
    while (--i >= 0)
      if (!sp->ttis[i].tt_isdst)
        break;
  }

  /*
   * The next heuristics are for data generated by tzdb 2018e or earlier,
   * for zones like EST5EDT where the first transition is to DST.
   */

  /*
   * If no result yet, find the first standard type. If there is none, punt
   * to type zero.
   */
  if (i < 0)
  {
    i = 0;
    while (sp->ttis[i].tt_isdst)
      if (++i >= sp->typecnt)
      {
        i = 0;
        break;
      }
  }

  /*
   * A simple 'sp->defaulttype = 0;' would suffice here if we didn't have to
   * worry about 2018e-or-earlier data.  Even simpler would be to remove the
   * defaulttype member and just use 0 in its place.
   */
  sp->defaulttype = i;

  return 0;
}

/* Load tz data from the file named NAME into *SP.  Read extended
 * format if DOEXTEND.  Return 0 on success, an errno value on failure.
 * PG: If "canonname" is not NULL, then on success the canonical spelling of
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 */
int
tzload(const char *name, char *canonname, struct state *sp, bool doextend)
{
  union local_storage *lsp = malloc(sizeof *lsp);

  if (!lsp)
    return errno;
  else
  {
    int     err = tzloadbody(name, canonname, sp, doextend, lsp);

    free(lsp);
    return err;
  }
}

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

  if (sp == NULL ||
    a < 0 || a >= sp->typecnt ||
    b < 0 || b >= sp->typecnt)
    result = false;
  else
  {
    const struct ttinfo *ap = &sp->ttis[a];
    const struct ttinfo *bp = &sp->ttis[b];

    result = (ap->tt_utoff == bp->tt_utoff
          && ap->tt_isdst == bp->tt_isdst
          && ap->tt_ttisstd == bp->tt_ttisstd
          && ap->tt_ttisut == bp->tt_ttisut
          && (strcmp(&sp->chars[ap->tt_desigidx],
               &sp->chars[bp->tt_desigidx])
            == 0));
  }
  return result;
}

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

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

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

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

  while ((c = *strp) != '\0' && !is_digit(c) && c != ',' && c != '-' &&
       c != '+')
    ++strp;
  return strp;
}

/*
 * Given a pointer into an extended timezone string, scan until the ending
 * delimiter of the time zone abbreviation is located.
 * Return a pointer to the delimiter.
 *
 * As with getzname above, the legal character set is actually quite
 * restricted, with other characters producing undefined results.
 * We don't do any checking here; checking is done later in common-case code.
 */

static const char *
getqzname(const char *strp, const int delim)
{
  int     c;

  while ((c = *strp) != '\0' && c != delim)
    ++strp;
  return strp;
}

/*
 * Given a pointer into a timezone 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 || !is_digit(c = *strp))
    return NULL;
  num = 0;
  do
  {
    num = num * 10 + (c - '0');
    if (num > max)
      return NULL;   /* illegal value */
    c = *++strp;
  } while (is_digit(c));
  if (num < min)
    return NULL;     /* illegal value */
  *nump = num;
  return strp;
}

/*
 * Given a pointer into a timezone 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, int32 *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 * (int32) SECSPERHOUR;
  if (*strp == ':')
  {
    ++strp;
    strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
    if (strp == NULL)
      return NULL;
    *secsp += num * SECSPERMIN;
    if (*strp == ':')
    {
      ++strp;
      /* 'SECSPERMIN' allows for leap seconds.  */
      strp = getnum(strp, &num, 0, SECSPERMIN);
      if (strp == NULL)
        return NULL;
      *secsp += num;
    }
  }
  return strp;
}

/*
 * Given a pointer into a timezone 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, int32 *const offsetp)
{
  bool    neg = false;

  if (*strp == '-')
  {
    neg = true;
    ++strp;
  }
  else if (*strp == '+')
    ++strp;
  strp = getsecs(strp, offsetp);
  if (strp == NULL)
    return NULL;     /* illegal time */
  if (neg)
    *offsetp = -*offsetp;
  return strp;
}

/*
 * Given a pointer into a timezone 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 (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 = getoffset(strp, &rulep->r_time);
  }
  else
    rulep->r_time = 2 * SECSPERHOUR; /* default = 2:00:00 */
  return strp;
}

/*
 * Given a year, a rule, and the offset from UT at the time that rule takes
 * effect, calculate the year-relative time that rule takes effect.
 */

static int32
transtime(const int year, const struct rule *const rulep,
      const int32 offset)
{
  bool    leapyear;
  int32   value;
  int     i;
  int     d,
        m1,
        yy0,
        yy1,
        yy2,
        dow;

  INITIALIZE(value);
  leapyear = isleap(year);
  switch (rulep->r_type)
  {

    case JULIAN_DAY:

      /*
       * Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
       * years. In non-leap years, or if the day number is 59 or less,
       * just add SECSPERDAY times the day number-1 to the time of
       * January 1, midnight, to get the day.
       */
      value = (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 = rulep->r_day * SECSPERDAY;
      break;

    case MONTH_NTH_DAY_OF_WEEK:

      /*
       * Mm.n.d - nth "dth day" of month m.
       */

      /*
       * 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[(int) leapyear][rulep->r_mon - 1])
          break;
        d += DAYSPERWEEK;
      }

      /*
       * "d" is the day-of-month (zero-origin) of the day we want.
       */
      value = d * SECSPERDAY;
      for (i = 0; i < rulep->r_mon - 1; ++i)
        value += mon_lengths[(int) leapyear][i] * SECSPERDAY;
      break;
  }

  /*
   * "value" is the year-relative time of 00:00:00 UT on the day in
   * question. To get the year-relative time of the specified local time on
   * that day, add the transition time and the current offset from UT.
   */
  return value + rulep->r_time + offset;
}

/*
 * Given a POSIX section 8-style TZ string, fill in the rule tables as
 * appropriate.
 * Returns true on success, false on failure.
 */
bool
tzparse(const char *name, struct state *sp, bool lastditch)
{
  const char *stdname;
  const char *dstname = NULL;
  size_t    stdlen;
  size_t    dstlen;
  size_t    charcnt;
  int32   stdoffset;
  int32   dstoffset;
  char     *cp;
  bool    load_ok;

  stdname = name;
  if (lastditch)
  {
    /* Unlike IANA, don't assume name is exactly "GMT" */
    stdlen = strlen(name);  /* length of standard zone name */
    name += stdlen;
    stdoffset = 0;
  }
  else
  {
    if (*name == '<')
    {
      name++;
      stdname = name;
      name = getqzname(name, '>');
      if (*name != '>')
        return false;
      stdlen = name - stdname;
      name++;
    }
    else
    {
      name = getzname(name);
      stdlen = name - stdname;
    }
    if (*name == '\0')   /* we allow empty STD abbrev, unlike IANA */
      return false;
    name = getoffset(name, &stdoffset);
    if (name == NULL)
      return false;
  }
  charcnt = stdlen + 1;
  if (sizeof sp->chars < charcnt)
    return false;

  /*
   * The IANA code always tries to tzload(TZDEFRULES) here.  We do not want
   * to do that; it would be bad news in the lastditch case, where we can't
   * assume pg_open_tzfile() is sane yet.  Moreover, if we did load it and
   * it contains leap-second-dependent info, that would cause problems too.
   * Finally, IANA has deprecated the TZDEFRULES feature, so it presumably
   * will die at some point.  Desupporting it now seems like good
   * future-proofing.
   */
  load_ok = false;
  sp->goback = sp->goahead = false;  /* simulate failed tzload() */
  sp->leapcnt = 0;      /* intentionally assume no leap seconds */

  if (*name != '\0')
  {
    if (*name == '<')
    {
      dstname = ++name;
      name = getqzname(name, '>');
      if (*name != '>')
        return false;
      dstlen = name - dstname;
      name++;
    }
    else
    {
      dstname = name;
      name = getzname(name);
      dstlen = name - dstname;  /* length of DST abbr. */
    }
    if (!dstlen)
      return false;
    charcnt += dstlen + 1;
    if (sizeof sp->chars < charcnt)
      return false;
    if (*name != '\0' && *name != ',' && *name != ';')
    {
      name = getoffset(name, &dstoffset);
      if (name == NULL)
        return false;
    }
    else
      dstoffset = stdoffset - SECSPERHOUR;
    if (*name == '\0' && !load_ok)
      name = TZDEFRULESTRING;
    if (*name == ',' || *name == ';')
    {
      struct rule start;
      struct rule end;
      int     year;
      int     yearlim;
      int     timecnt;
      pg_time_t janfirst;
      int32   janoffset = 0;
      int     yearbeg;

      ++name;
      if ((name = getrule(name, &start)) == NULL)
        return false;
      if (*name++ != ',')
        return false;
      if ((name = getrule(name, &end)) == NULL)
        return false;
      if (*name != '\0')
        return false;
      sp->typecnt = 2;  /* standard time and DST */

      /*
       * Two transitions per year, from EPOCH_YEAR forward.
       */
      init_ttinfo(&sp->ttis[0], -stdoffset, false, 0);
      init_ttinfo(&sp->ttis[1], -dstoffset, true, stdlen + 1);
      sp->defaulttype = 0;
      timecnt = 0;
      janfirst = 0;
      yearbeg = EPOCH_YEAR;

      do
      {
        int32   yearsecs
        = year_lengths[isleap(yearbeg - 1)] * SECSPERDAY;

        yearbeg--;
        if (increment_overflow_time(&janfirst, -yearsecs))
        {
          janoffset = -yearsecs;
          break;
        }
      } while (EPOCH_YEAR - YEARSPERREPEAT / 2 < yearbeg);

      yearlim = yearbeg + YEARSPERREPEAT + 1;
      for (year = yearbeg; year < yearlim; year++)
      {
        int32
              starttime = transtime(year, &start, stdoffset),
              endtime = transtime(year, &end, dstoffset);
        int32
              yearsecs = (year_lengths[isleap(year)]
                    * SECSPERDAY);
        bool    reversed = endtime < starttime;

        if (reversed)
        {
          int32   swap = starttime;

          starttime = endtime;
          endtime = swap;
        }
        if (reversed
          || (starttime < endtime
            && (endtime - starttime
              < (yearsecs
                 + (stdoffset - dstoffset)))))
        {
          if (TZ_MAX_TIMES - 2 < timecnt)
            break;
          sp->ats[timecnt] = janfirst;
          if (!increment_overflow_time
            (&sp->ats[timecnt],
             janoffset + starttime))
            sp->types[timecnt++] = !reversed;
          sp->ats[timecnt] = janfirst;
          if (!increment_overflow_time
            (&sp->ats[timecnt],
             janoffset + endtime))
          {
            sp->types[timecnt++] = reversed;
            yearlim = year + YEARSPERREPEAT + 1;
          }
        }
        if (increment_overflow_time
          (&janfirst, janoffset + yearsecs))
          break;
        janoffset = 0;
      }
      sp->timecnt = timecnt;
      if (!timecnt)
      {
        sp->ttis[0] = sp->ttis[1];
        sp->typecnt = 1;  /* Perpetual DST.  */
      }
      else if (YEARSPERREPEAT < year - yearbeg)
        sp->goback = sp->goahead = true;
    }
    else
    {
      int32   theirstdoffset;
      int32   theirdstoffset;
      int32   theiroffset;
      bool    isdst;
      int     i;
      int     j;

      if (*name != '\0')
        return false;

      /*
       * 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_utoff;
          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_utoff;
          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_ttisut)
        {
          /* No adjustment to transition time */
        }
        else
        {
          /*
           * If daylight saving time is in effect, and the
           * transition time was not specified as standard time, add
           * the daylight saving 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_utoff;
        if (sp->ttis[j].tt_isdst)
          theirdstoffset = theiroffset;
        else
          theirstdoffset = theiroffset;
      }

      /*
       * Finally, fill in ttis.
       */
      init_ttinfo(&sp->ttis[0], -stdoffset, false, 0);
      init_ttinfo(&sp->ttis[1], -dstoffset, true, stdlen + 1);
      sp->typecnt = 2;
      sp->defaulttype = 0;
    }
  }
  else
  {
    dstlen = 0;
    sp->typecnt = 1;    /* only standard time */
    sp->timecnt = 0;
    init_ttinfo(&sp->ttis[0], -stdoffset, false, 0);
    sp->defaulttype = 0;
  }
  sp->charcnt = charcnt;
  cp = sp->chars;
  memcpy(cp, stdname, stdlen);
  cp += stdlen;
  *cp++ = '\0';
  if (dstlen != 0)
  {
    memcpy(cp, dstname, dstlen);
    *(cp + dstlen) = '\0';
  }
  return true;
}

static void
gmtload(struct state *const sp)
{
  if (tzload(gmt, NULL, sp, true) != 0)
    tzparse(gmt, sp, true);
}


/*
 * 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.)
 */
static struct pg_tm *
localsub(struct state const *sp, pg_time_t const *timep,
     struct pg_tm *const tmp)
{
  const struct ttinfo *ttisp;
  int     i;
  struct pg_tm *result;
  const pg_time_t t = *timep;

  if (sp == NULL)
    return gmtsub(timep, 0, tmp);
  if ((sp->goback && t < sp->ats[0]) ||
    (sp->goahead && t > sp->ats[sp->timecnt - 1]))
  {
    pg_time_t newt = t;
    pg_time_t seconds;
    pg_time_t years;

    if (t < sp->ats[0])
      seconds = sp->ats[0] - t;
    else
      seconds = t - sp->ats[sp->timecnt - 1];
    --seconds;
    years = (seconds / SECSPERREPEAT + 1) * YEARSPERREPEAT;
    seconds = years * AVGSECSPERYEAR;
    if (t < sp->ats[0])
      newt += seconds;
    else
      newt -= seconds;
    if (newt < sp->ats[0] ||
      newt > sp->ats[sp->timecnt - 1])
      return NULL;   /* "cannot happen" */
    result = localsub(sp, &newt, tmp);
    if (result)
    {
      int64   newy;

      newy = result->tm_year;
      if (t < sp->ats[0])
        newy -= years;
      else
        newy += years;
      if (!(INT_MIN <= newy && newy <= INT_MAX))
        return NULL;
      result->tm_year = newy;
    }
    return result;
  }
  if (sp->timecnt == 0 || t < sp->ats[0])
  {
    i = sp->defaulttype;
  }
  else
  {
    int     lo = 1;
    int     hi = sp->timecnt;

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

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

  /*
   * To get (wrong) behavior that's compatible with System V Release 2.0
   * you'd replace the statement below with t += ttisp->tt_utoff;
   * timesub(&t, 0L, sp, tmp);
   */
  result = timesub(&t, ttisp->tt_utoff, sp, tmp);
  if (result)
  {
    result->tm_isdst = ttisp->tt_isdst;
    result->tm_zone = unconstify(char *, &sp->chars[ttisp->tt_desigidx]);
  }
  return result;
}


struct pg_tm *
pg_localtime(const pg_time_t *timep, const pg_tz *tz)
{
  return localsub(&tz->state, timep, &tm);
}


/*
 * gmtsub is to gmtime as localsub is to localtime.
 *
 * Except we have a private "struct state" for GMT, so no sp is passed in.
 */

static struct pg_tm *
gmtsub(pg_time_t const *timep, int32 offset,
     struct pg_tm *tmp)
{
  struct pg_tm *result;

  /* GMT timezone state data is kept here */
  static struct state *gmtptr = NULL;

  if (gmtptr == NULL)
  {
    /* Allocate on first use */
    gmtptr = (struct state *) malloc(sizeof(struct state));
    if (gmtptr == NULL)
      return NULL;   /* errno should be set by malloc */
    gmtload(gmtptr);
  }

  result = timesub(timep, offset, gmtptr, tmp);

  /*
   * Could get fancy here and deliver something such as "+xx" or "-xx" if
   * offset is non-zero, but this is no time for a treasure hunt.
   */
  if (offset != 0)
    tmp->tm_zone = wildabbr;
  else
    tmp->tm_zone = gmtptr->chars;

  return result;
}

struct pg_tm *
pg_gmtime(const pg_time_t *timep)
{
  return gmtsub(timep, 0, &tm);
}

/*
 * Return the number of leap years through the end of the given year
 * where, to make the math easy, the answer for year zero is defined as zero.
 */

static int
leaps_thru_end_of_nonneg(int y)
{
  return y / 4 - y / 100 + y / 400;
}

static int
leaps_thru_end_of(const int y)
{
  return (y < 0
      ? -1 - leaps_thru_end_of_nonneg(-1 - y)
      : leaps_thru_end_of_nonneg(y));
}

static struct pg_tm *
timesub(const pg_time_t *timep, int32 offset,
    const struct state *sp, struct pg_tm *tmp)
{
  const struct lsinfo *lp;
  pg_time_t tdays;
  int     idays;      /* unsigned would be so 2003 */
  int64   rem;
  int     y;
  const int  *ip;
  int64   corr;
  bool    hit;
  int     i;

  corr = 0;
  hit = false;
  i = (sp == NULL) ? 0 : sp->leapcnt;
  while (--i >= 0)
  {
    lp = &sp->lsis[i];
    if (*timep >= lp->ls_trans)
    {
      corr = lp->ls_corr;
      hit = (*timep == lp->ls_trans
           && (i == 0 ? 0 : lp[-1].ls_corr) < corr);
      break;
    }
  }
  y = EPOCH_YEAR;
  tdays = *timep / SECSPERDAY;
  rem = *timep % SECSPERDAY;
  while (tdays < 0 || tdays >= year_lengths[isleap(y)])
  {
    int     newy;
    pg_time_t tdelta;
    int     idelta;
    int     leapdays;

    tdelta = tdays / DAYSPERLYEAR;
    if (!((!TYPE_SIGNED(pg_time_t) || INT_MIN <= tdelta)
        && tdelta <= INT_MAX))
      goto out_of_range;
    idelta = tdelta;
    if (idelta == 0)
      idelta = (tdays < 0) ? -1 : 1;
    newy = y;
    if (increment_overflow(&newy, idelta))
      goto out_of_range;
    leapdays = leaps_thru_end_of(newy - 1) -
      leaps_thru_end_of(y - 1);
    tdays -= ((pg_time_t) newy - y) * DAYSPERNYEAR;
    tdays -= leapdays;
    y = newy;
  }

  /*
   * Given the range, we can now fearlessly cast...
   */
  idays = tdays;
  rem += offset - corr;
  while (rem < 0)
  {
    rem += SECSPERDAY;
    --idays;
  }
  while (rem >= SECSPERDAY)
  {
    rem -= SECSPERDAY;
    ++idays;
  }
  while (idays < 0)
  {
    if (increment_overflow(&y, -1))
      goto out_of_range;
    idays += year_lengths[isleap(y)];
  }
  while (idays >= year_lengths[isleap(y)])
  {
    idays -= year_lengths[isleap(y)];
    if (increment_overflow(&y, 1))
      goto out_of_range;
  }
  tmp->tm_year = y;
  if (increment_overflow(&tmp->tm_year, -TM_YEAR_BASE))
    goto out_of_range;
  tmp->tm_yday = idays;

  /*
   * The "extra" mods below avoid overflow problems.
   */
  tmp->tm_wday = EPOCH_WDAY +
    ((y - EPOCH_YEAR) % DAYSPERWEEK) *
    (DAYSPERNYEAR % DAYSPERWEEK) +
    leaps_thru_end_of(y - 1) -
    leaps_thru_end_of(EPOCH_YEAR - 1) +
    idays;
  tmp->tm_wday %= DAYSPERWEEK;
  if (tmp->tm_wday < 0)
    tmp->tm_wday += DAYSPERWEEK;
  tmp->tm_hour = (int) (rem / SECSPERHOUR);
  rem %= SECSPERHOUR;
  tmp->tm_min = (int) (rem / SECSPERMIN);

  /*
   * A positive leap second requires a special representation. This uses
   * "... ??:59:60" et seq.
   */
  tmp->tm_sec = (int) (rem % SECSPERMIN) + hit;
  ip = mon_lengths[isleap(y)];
  for (tmp->tm_mon = 0; idays >= ip[tmp->tm_mon]; ++(tmp->tm_mon))
    idays -= ip[tmp->tm_mon];
  tmp->tm_mday = (int) (idays + 1);
  tmp->tm_isdst = 0;
  tmp->tm_gmtoff = offset;
  return tmp;

out_of_range:
  errno = EOVERFLOW;
  return NULL;
}

/*
 * Normalize logic courtesy Paul Eggert.
 */

static bool
increment_overflow(int *ip, int j)
{
  int const i = *ip;

  /*----------
   * If i >= 0 there can only be overflow if i + j > INT_MAX
   * or if j > INT_MAX - i; given i >= 0, INT_MAX - i cannot overflow.
   * If i < 0 there can only be overflow if i + j < INT_MIN
   * or if j < INT_MIN - i; given i < 0, INT_MIN - i cannot overflow.
   *----------
   */
  if ((i >= 0) ? (j > INT_MAX - i) : (j < INT_MIN - i))
    return true;
  *ip += j;
  return false;
}

static bool
increment_overflow_time(pg_time_t *tp, int32 j)
{
  /*----------
   * This is like
   * 'if (! (TIME_T_MIN <= *tp + j && *tp + j <= TIME_T_MAX)) ...',
   * except that it does the right thing even if *tp + j would overflow.
   *----------
   */
  if (!(j < 0
      ? (TYPE_SIGNED(pg_time_t) ? TIME_T_MIN - j <= *tp : -1 - j < *tp)
      : *tp <= TIME_T_MAX - j))
    return true;
  *tp += j;
  return false;
}

static int64
leapcorr(struct state const *sp, pg_time_t t)
{
  struct lsinfo const *lp;
  int     i;

  i = sp->leapcnt;
  while (--i >= 0)
  {
    lp = &sp->lsis[i];
    if (t >= lp->ls_trans)
      return lp->ls_corr;
  }
  return 0;
}

/*
 * Find the next DST transition time in the given zone after the given time
 *
 * *timep and *tz are input arguments, the other parameters are output values.
 *
 * When the function result is 1, *boundary is set to the pg_time_t
 * representation of the next DST transition time after *timep,
 * *before_gmtoff and *before_isdst are set to the GMT offset and isdst
 * state prevailing just before that boundary (in particular, the state
 * prevailing at *timep), and *after_gmtoff and *after_isdst are set to
 * the state prevailing just after that boundary.
 *
 * When the function result is 0, there is no known DST transition
 * after *timep, but *before_gmtoff and *before_isdst indicate the GMT
 * offset and isdst state prevailing at *timep.  (This would occur in
 * DST-less time zones, or if a zone has permanently ceased using DST.)
 *
 * A function result of -1 indicates failure (this case does not actually
 * occur in our current implementation).
 */
int
pg_next_dst_boundary(const pg_time_t *timep,
           long int *before_gmtoff,
           int *before_isdst,
           pg_time_t *boundary,
           long int *after_gmtoff,
           int *after_isdst,
           const pg_tz *tz)
{
  const struct state *sp;
  const struct ttinfo *ttisp;
  int     i;
  int     j;
  const pg_time_t t = *timep;

  sp = &tz->state;
  if (sp->timecnt == 0)
  {
    /* non-DST zone, use the defaulttype */
    ttisp = &sp->ttis[sp->defaulttype];
    *before_gmtoff = ttisp->tt_utoff;
    *before_isdst = ttisp->tt_isdst;
    return 0;
  }
  if ((sp->goback && t < sp->ats[0]) ||
    (sp->goahead && t > sp->ats[sp->timecnt - 1]))
  {
    /* For values outside the transition table, extrapolate */
    pg_time_t newt = t;
    pg_time_t seconds;
    pg_time_t tcycles;
    int64   icycles;
    int     result;

    if (t < sp->ats[0])
      seconds = sp->ats[0] - t;
    else
      seconds = t - sp->ats[sp->timecnt - 1];
    --seconds;
    tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
    ++tcycles;
    icycles = tcycles;
    if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
      return -1;
    seconds = icycles;
    seconds *= YEARSPERREPEAT;
    seconds *= AVGSECSPERYEAR;
    if (t < sp->ats[0])
      newt += seconds;
    else
      newt -= seconds;
    if (newt < sp->ats[0] ||
      newt > sp->ats[sp->timecnt - 1])
      return -1;     /* "cannot happen" */

    result = pg_next_dst_boundary(&newt, before_gmtoff,
                    before_isdst,
                    boundary,
                    after_gmtoff,
                    after_isdst,
                    tz);
    if (t < sp->ats[0])
      *boundary -= seconds;
    else
      *boundary += seconds;
    return result;
  }

  if (t >= sp->ats[sp->timecnt - 1])
  {
    /* No known transition > t, so use last known segment's type */
    i = sp->types[sp->timecnt - 1];
    ttisp = &sp->ttis[i];
    *before_gmtoff = ttisp->tt_utoff;
    *before_isdst = ttisp->tt_isdst;
    return 0;
  }
  if (t < sp->ats[0])
  {
    /* For "before", use the defaulttype */
    ttisp = &sp->ttis[sp->defaulttype];
    *before_gmtoff = ttisp->tt_utoff;
    *before_isdst = ttisp->tt_isdst;
    *boundary = sp->ats[0];
    /* And for "after", use the first segment's type */
    i = sp->types[0];
    ttisp = &sp->ttis[i];
    *after_gmtoff = ttisp->tt_utoff;
    *after_isdst = ttisp->tt_isdst;
    return 1;
  }
  /* Else search to find the boundary following t */
  {
    int     lo = 1;
    int     hi = sp->timecnt - 1;

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

      if (t < sp->ats[mid])
        hi = mid;
      else
        lo = mid + 1;
    }
    i = lo;
  }
  j = sp->types[i - 1];
  ttisp = &sp->ttis[j];
  *before_gmtoff = ttisp->tt_utoff;
  *before_isdst = ttisp->tt_isdst;
  *boundary = sp->ats[i];
  j = sp->types[i];
  ttisp = &sp->ttis[j];
  *after_gmtoff = ttisp->tt_utoff;
  *after_isdst = ttisp->tt_isdst;
  return 1;
}

/*
 * Identify a timezone abbreviation's meaning in the given zone
 *
 * Determine the GMT offset and DST flag associated with the abbreviation.
 * This is generally used only when the abbreviation has actually changed
 * meaning over time; therefore, we also take a UTC cutoff time, and return
 * the meaning in use at or most recently before that time, or the meaning
 * in first use after that time if the abbrev was never used before that.
 *
 * On success, returns true and sets *gmtoff and *isdst.  If the abbreviation
 * was never used at all in this zone, returns false.
 *
 * Note: abbrev is matched case-sensitively; it should be all-upper-case.
 */
bool
pg_interpret_timezone_abbrev(const char *abbrev,
               const pg_time_t *timep,
               long int *gmtoff,
               int *isdst,
               const pg_tz *tz)
{
  const struct state *sp;
  const char *abbrs;
  const struct ttinfo *ttisp;
  int     abbrind;
  int     cutoff;
  int     i;
  const pg_time_t t = *timep;

  sp = &tz->state;

  /*
   * Locate the abbreviation in the zone's abbreviation list.  We assume
   * there are not duplicates in the list.
   */
  abbrs = sp->chars;
  abbrind = 0;
  while (abbrind < sp->charcnt)
  {
    if (strcmp(abbrev, abbrs + abbrind) == 0)
      break;
    while (abbrs[abbrind] != '\0')
      abbrind++;
    abbrind++;
  }
  if (abbrind >= sp->charcnt)
    return false;     /* not there! */

  /*
   * Unlike pg_next_dst_boundary, we needn't sweat about extrapolation
   * (goback/goahead zones).  Finding the newest or oldest meaning of the
   * abbreviation should get us what we want, since extrapolation would just
   * be repeating the newest or oldest meanings.
   *
   * Use binary search to locate the first transition > cutoff time.  (Note
   * that sp->timecnt could be zero, in which case this loop does nothing
   * and only the defaulttype entry will be checked.)
   */
  {
    int     lo = 0;
    int     hi = sp->timecnt;

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

      if (t < sp->ats[mid])
        hi = mid;
      else
        lo = mid + 1;
    }
    cutoff = lo;
  }

  /*
   * Scan backwards to find the latest interval using the given abbrev
   * before the cutoff time.
   */
  for (i = cutoff - 1; i >= 0; i--)
  {
    ttisp = &sp->ttis[sp->types[i]];
    if (ttisp->tt_desigidx == abbrind)
    {
      *gmtoff = ttisp->tt_utoff;
      *isdst = ttisp->tt_isdst;
      return true;
    }
  }

  /*
   * Not found yet; check the defaulttype, which is notionally the era
   * before any of the entries in sp->types[].
   */
  ttisp = &sp->ttis[sp->defaulttype];
  if (ttisp->tt_desigidx == abbrind)
  {
    *gmtoff = ttisp->tt_utoff;
    *isdst = ttisp->tt_isdst;
    return true;
  }

  /*
   * Not there, so scan forwards to find the first one after the cutoff.
   */
  for (i = cutoff; i < sp->timecnt; i++)
  {
    ttisp = &sp->ttis[sp->types[i]];
    if (ttisp->tt_desigidx == abbrind)
    {
      *gmtoff = ttisp->tt_utoff;
      *isdst = ttisp->tt_isdst;
      return true;
    }
  }

  return false;       /* hm, not actually used in any interval? */
}

/*
 * Detect whether a timezone abbreviation is defined within the given zone.
 *
 * This is similar to pg_interpret_timezone_abbrev() but is not concerned
 * with a specific point in time.  We want to know if the abbreviation is
 * known at all, and if so whether it has one meaning or several.
 *
 * Returns true if the abbreviation is known, false if not.
 * If the abbreviation is known and has a single meaning (only one value
 * of gmtoff/isdst), sets *isfixed = true and sets *gmtoff and *isdst.
 * If there are multiple meanings, sets *isfixed = false.
 *
 * Note: abbrev is matched case-sensitively; it should be all-upper-case.
 */
bool
pg_timezone_abbrev_is_known(const char *abbrev,
              bool *isfixed,
              long int *gmtoff,
              int *isdst,
              const pg_tz *tz)
{
  bool    result = false;
  const struct state *sp = &tz->state;
  const char *abbrs;
  int     abbrind;

  /*
   * Locate the abbreviation in the zone's abbreviation list.  We assume
   * there are not duplicates in the list.
   */
  abbrs = sp->chars;
  abbrind = 0;
  while (abbrind < sp->charcnt)
  {
    if (strcmp(abbrev, abbrs + abbrind) == 0)
      break;
    while (abbrs[abbrind] != '\0')
      abbrind++;
    abbrind++;
  }
  if (abbrind >= sp->charcnt)
    return false;     /* definitely not there */

  /*
   * Scan the ttinfo array to find uses of the abbreviation.
   */
  for (int i = 0; i < sp->typecnt; i++)
  {
    const struct ttinfo *ttisp = &sp->ttis[i];

    if (ttisp->tt_desigidx == abbrind)
    {
      if (!result)
      {
        /* First usage */
        *isfixed = true; /* for the moment */
        *gmtoff = ttisp->tt_utoff;
        *isdst = ttisp->tt_isdst;
        result = true;
      }
      else
      {
        /* Second or later usage, does it match? */
        if (*gmtoff != ttisp->tt_utoff ||
          *isdst != ttisp->tt_isdst)
        {
          *isfixed = false;
          break;    /* no point in looking further */
        }
      }
    }
  }

  return result;
}

/*
 * Iteratively fetch all the abbreviations used in the given time zone.
 *
 * *indx is a state counter that the caller must initialize to zero
 * before the first call, and not touch between calls.
 *
 * Returns the next known abbreviation, or NULL if there are no more.
 *
 * Note: the caller typically applies pg_interpret_timezone_abbrev()
 * to each result.  While that nominally results in O(N^2) time spent
 * searching the sp->chars[] array, we don't expect any zone to have
 * enough abbreviations to make that meaningful.
 */
const char *
pg_get_next_timezone_abbrev(int *indx,
              const pg_tz *tz)
{
  const char *result;
  const struct state *sp = &tz->state;
  const char *abbrs;
  int     abbrind;

  /* If we're still in range, the result is the current abbrev. */
  abbrs = sp->chars;
  abbrind = *indx;
  if (abbrind < 0 || abbrind >= sp->charcnt)
    return NULL;
  result = abbrs + abbrind;

  /* Advance *indx past this abbrev and its trailing null. */
  while (abbrs[abbrind] != '\0')
    abbrind++;
  abbrind++;
  *indx = abbrind;

  return result;
}

/*
 * If the given timezone uses only one GMT offset, store that offset
 * into *gmtoff and return true, else return false.
 */
bool
pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff)
{
  /*
   * The zone could have more than one ttinfo, if it's historically used
   * more than one abbreviation.  We return true as long as they all have
   * the same gmtoff.
   */
  const struct state *sp;
  int     i;

  sp = &tz->state;
  for (i = 1; i < sp->typecnt; i++)
  {
    if (sp->ttis[i].tt_utoff != sp->ttis[0].tt_utoff)
      return false;
  }
  *gmtoff = sp->ttis[0].tt_utoff;
  return true;
}

/*
 * Return the name of the current timezone
 */
const char *
pg_get_timezone_name(pg_tz *tz)
{
  if (tz)
    return tz->TZname;
  return NULL;
}

/*
 * Check whether timezone is acceptable.
 *
 * What we are doing here is checking for leap-second-aware timekeeping.
 * We need to reject such TZ settings because they'll wreak havoc with our
 * date/time arithmetic.
 */
bool
pg_tz_acceptable(pg_tz *tz)
{
  struct pg_tm *tt;
  pg_time_t time2000;

  /*
   * To detect leap-second timekeeping, run pg_localtime for what should be
   * GMT midnight, 2000-01-01.  Insist that the tm_sec value be zero; any
   * other result has to be due to leap seconds.
   */
  time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
  tt = pg_localtime(&time2000, tz);
  if (!tt || tt->tm_sec != 0)
    return false;

  return true;
}

Coverage Report

Created: 2025-10-09 06:07