/* Convert a broken-down timestamp to a string.  */

/*

 * Copyright 1989 The Regents of the University of California.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. 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 BY THE REGENTS AND CONTRIBUTORS "AS IS" AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

/*

 * Based on the UCB version with the copyright notice appearing above.

 *

 * This is ANSIish only when "multibyte character == plain character".

 *

 * IDENTIFICATION

 *    src/timezone/strftime.c

 */

#include "postgres.h"

#include <fcntl.h>

#include "private.h"

struct lc_time_T

{

  const char *mon[MONSPERYEAR];

  const char *month[MONSPERYEAR];

  const char *wday[DAYSPERWEEK];

  const char *weekday[DAYSPERWEEK];

  const char *X_fmt;

  const char *x_fmt;

  const char *c_fmt;

  const char *am;

  const char *pm;

  const char *date_fmt;

};

static const struct lc_time_T C_time_locale = {

  {

    "Jan", "Feb", "Mar", "Apr", "May", "Jun",

    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"

  }, {

    "January", "February", "March", "April", "May", "June",

    "July", "August", "September", "October", "November", "December"

  }, {

    "Sun", "Mon", "Tue", "Wed",

    "Thu", "Fri", "Sat"

  }, {

    "Sunday", "Monday", "Tuesday", "Wednesday",

    "Thursday", "Friday", "Saturday"

  },

  /* X_fmt */

  "%H:%M:%S",

  /*

   * x_fmt C99 and later require this format. Using just numbers (as here)

   * makes Quakers happier; it's also compatible with SVR4.

   */

  "%m/%d/%y",

  /*

   * c_fmt C99 and later require this format. Previously this code used "%D

   * %X", but we now conform to C99. Note that "%a %b %d %H:%M:%S %Y" is

   * used by Solaris 2.3.

   */

  "%a %b %e %T %Y",

  /* am */

  "AM",

  /* pm */

  "PM",

  /* date_fmt */

  "%a %b %e %H:%M:%S %Z %Y"

};

enum warn

{

  IN_NONE, IN_SOME, IN_THIS, IN_ALL

};

static char *_add(const char *str, char *pt, const char *ptlim);

static char *_conv(int n, const char *format, char *pt, const char *ptlim);

static char *_fmt(const char *format, const struct pg_tm *t, char *pt, const char *ptlim,

          enum warn *warnp);

static char *_yconv(int a, int b, bool convert_top, bool convert_yy, char *pt, char const *ptlim);

/*

 * Convert timestamp t to string s, a caller-allocated buffer of size maxsize,

 * using the given format pattern.

 *

 * Unlike standard strftime(), we guarantee to provide a null-terminated

 * result even on failure, so long as maxsize > 0.  If we overrun the buffer,

 * return an empty string rather than risking mis-encoded multibyte output.

 * (Since this module only supports C locale, you might think multibyte

 * characters are impossible --- but the time zone name printed by %Z comes

 * from outside and could contain such.)

 *

 * See also timestamptz_to_str.

 */

size_t

pg_strftime(char *s, size_t maxsize, const char *format, const struct pg_tm *t)

{

  char     *p;

  int     saved_errno = errno;

  enum warn warn = IN_NONE;

  p = _fmt(format, t, s, s + maxsize, &warn);

  if (!p)

  {

    errno = EOVERFLOW;

    if (maxsize > 0)

      *s = '\0';

    return 0;

  }

  if (p == s + maxsize)

  {

    errno = ERANGE;

    if (maxsize > 0)

      *s = '\0';

    return 0;

  }

  *p = '\0';

  errno = saved_errno;

  return p - s;

}

static char *

_fmt(const char *format, const struct pg_tm *t, char *pt,

   const char *ptlim, enum warn *warnp)

{

  struct lc_time_T const *Locale = &C_time_locale;

  for (; *format; ++format)

  {

    if (*format == '%')

    {

  label:

      switch (*++format)

      {

        default:

          /*

           * Output unknown conversion specifiers as-is, to aid

           * debugging.  This includes '%' at format end.  This

           * conforms to C23 section 7.29.3.5 paragraph 6, which

           * says behavior is undefined here.

           */

          --format;

          break;

        case 'A':

          pt = _add((t->tm_wday < 0 ||

                 t->tm_wday >= DAYSPERWEEK) ?

                "?" : Locale->weekday[t->tm_wday],

                pt, ptlim);

          continue;

        case 'a':

          pt = _add((t->tm_wday < 0 ||

                 t->tm_wday >= DAYSPERWEEK) ?

                "?" : Locale->wday[t->tm_wday],

                pt, ptlim);

          continue;

        case 'B':

          pt = _add((t->tm_mon < 0 ||

                 t->tm_mon >= MONSPERYEAR) ?

                "?" : Locale->month[t->tm_mon],

                pt, ptlim);

          continue;

        case 'b':

        case 'h':

          pt = _add((t->tm_mon < 0 ||

                 t->tm_mon >= MONSPERYEAR) ?

                "?" : Locale->mon[t->tm_mon],

                pt, ptlim);

          continue;

        case 'C':

          /*

           * %C used to do a... _fmt("%a %b %e %X %Y", t);

           * ...whereas now POSIX 1003.2 calls for something

           * completely different. (ado, 1993-05-24)

           */

          pt = _yconv(t->tm_year, TM_YEAR_BASE,

                true, false, pt, ptlim);

          continue;

        case 'c':

          {

            enum warn warn2 = IN_SOME;

            pt = _fmt(Locale->c_fmt, t, pt, ptlim, &warn2);

            if (warn2 == IN_ALL)

              warn2 = IN_THIS;

            if (warn2 > *warnp)

              *warnp = warn2;

          }

          continue;

        case 'D':

          pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp);

          continue;

        case 'd':

          pt = _conv(t->tm_mday, "%02d", pt, ptlim);

          continue;

        case 'E':

        case 'O':

          /*

           * Locale modifiers of C99 and later. The sequences %Ec

           * %EC %Ex %EX %Ey %EY %Od %oe %OH %OI %Om %OM %OS %Ou %OU

           * %OV %Ow %OW %Oy are supposed to provide alternative

           * representations.

           */

          goto label;

        case 'e':

          pt = _conv(t->tm_mday, "%2d", pt, ptlim);

          continue;

        case 'F':

          pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);

          continue;

        case 'H':

          pt = _conv(t->tm_hour, "%02d", pt, ptlim);

          continue;

        case 'I':

          pt = _conv((t->tm_hour % 12) ?

                 (t->tm_hour % 12) : 12,

                 "%02d", pt, ptlim);

          continue;

        case 'j':

          pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);

          continue;

        case 'k':

          /*

           * This used to be... _conv(t->tm_hour % 12 ? t->tm_hour %

           * 12 : 12, 2, ' '); ...and has been changed to the below

           * to match SunOS 4.1.1 and Arnold Robbins' strftime

           * version 3.0. That is, "%k" and "%l" have been swapped.

           * (ado, 1993-05-24)

           */

          pt = _conv(t->tm_hour, "%2d", pt, ptlim);

          continue;

#ifdef KITCHEN_SINK

        case 'K':

          /*

           * After all this time, still unclaimed!

           */

          pt = _add("kitchen sink", pt, ptlim);

          continue;

#endif              /* defined KITCHEN_SINK */

        case 'l':

          /*

           * This used to be... _conv(t->tm_hour, 2, ' '); ...and

           * has been changed to the below to match SunOS 4.1.1 and

           * Arnold Robbin's strftime version 3.0. That is, "%k" and

           * "%l" have been swapped. (ado, 1993-05-24)

           */

          pt = _conv((t->tm_hour % 12) ?

                 (t->tm_hour % 12) : 12,

                 "%2d", pt, ptlim);

          continue;

        case 'M':

          pt = _conv(t->tm_min, "%02d", pt, ptlim);

          continue;

        case 'm':

          pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);

          continue;

        case 'n':

          pt = _add("\n", pt, ptlim);

          continue;

        case 'p':

          pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?

                Locale->pm :

                Locale->am,

                pt, ptlim);

          continue;

        case 'R':

          pt = _fmt("%H:%M", t, pt, ptlim, warnp);

          continue;

        case 'r':

          pt = _fmt("%I:%M:%S %p", t, pt, ptlim, warnp);

          continue;

        case 'S':

          pt = _conv(t->tm_sec, "%02d", pt, ptlim);

          continue;

        case 'T':

          pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp);

          continue;

        case 't':

          pt = _add("\t", pt, ptlim);

          continue;

        case 'U':

          pt = _conv((t->tm_yday + DAYSPERWEEK -

                t->tm_wday) / DAYSPERWEEK,

                 "%02d", pt, ptlim);

          continue;

        case 'u':

          /*

           * From Arnold Robbins' strftime version 3.0: "ISO 8601:

           * Weekday as a decimal number [1 (Monday) - 7]" (ado,

           * 1993-05-24)

           */

          pt = _conv((t->tm_wday == 0) ?

                 DAYSPERWEEK : t->tm_wday,

                 "%d", pt, ptlim);

          continue;

        case 'V':   /* ISO 8601 week number */

        case 'G':   /* ISO 8601 year (four digits) */

        case 'g':   /* ISO 8601 year (two digits) */

/*

 * From Arnold Robbins' strftime version 3.0: "the week number of the

 * year (the first Monday as the first day of week 1) as a decimal number

 * (01-53)."

 * (ado, 1993-05-24)

 *

 * From <https://www.cl.cam.ac.uk/~mgk25/iso-time.html> by Markus Kuhn:

 * "Week 01 of a year is per definition the first week which has the

 * Thursday in this year, which is equivalent to the week which contains

 * the fourth day of January. In other words, the first week of a new year

 * is the week which has the majority of its days in the new year. Week 01

 * might also contain days from the previous year and the week before week

 * 01 of a year is the last week (52 or 53) of the previous year even if

 * it contains days from the new year. A week starts with Monday (day 1)

 * and ends with Sunday (day 7). For example, the first week of the year

 * 1997 lasts from 1996-12-30 to 1997-01-05..."

 * (ado, 1996-01-02)

 */

          {

            int     year;

            int     base;

            int     yday;

            int     wday;

            int     w;

            year = t->tm_year;

            base = TM_YEAR_BASE;

            yday = t->tm_yday;

            wday = t->tm_wday;

            for (;;)

            {

              int     len;

              int     bot;

              int     top;

              len = isleap_sum(year, base) ?

                DAYSPERLYEAR :

                DAYSPERNYEAR;

              /*

               * What yday (-3 ... 3) does the ISO year begin

               * on?

               */

              bot = ((yday + 11 - wday) %

                   DAYSPERWEEK) - 3;

              /*

               * What yday does the NEXT ISO year begin on?

               */

              top = bot -

                (len % DAYSPERWEEK);

              if (top < -3)

                top += DAYSPERWEEK;

              top += len;

              if (yday >= top)

              {

                ++base;

                w = 1;

                break;

              }

              if (yday >= bot)

              {

                w = 1 + ((yday - bot) /

                     DAYSPERWEEK);

                break;

              }

              --base;

              yday += isleap_sum(year, base) ?

                DAYSPERLYEAR :

                DAYSPERNYEAR;

            }

            if (*format == 'V')

              pt = _conv(w, "%02d",

                     pt, ptlim);

            else if (*format == 'g')

            {

              *warnp = IN_ALL;

              pt = _yconv(year, base,

                    false, true,

                    pt, ptlim);

            }

            else

              pt = _yconv(year, base,

                    true, true,

                    pt, ptlim);

          }

          continue;

        case 'v':

          /*

           * From Arnold Robbins' strftime version 3.0: "date as

           * dd-bbb-YYYY" (ado, 1993-05-24)

           */

          pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp);

          continue;

        case 'W':

          pt = _conv((t->tm_yday + DAYSPERWEEK -

                (t->tm_wday ?

                 (t->tm_wday - 1) :

                 (DAYSPERWEEK - 1))) / DAYSPERWEEK,

                 "%02d", pt, ptlim);

          continue;

        case 'w':

          pt = _conv(t->tm_wday, "%d", pt, ptlim);

          continue;

        case 'X':

          pt = _fmt(Locale->X_fmt, t, pt, ptlim, warnp);

          continue;

        case 'x':

          {

            enum warn warn2 = IN_SOME;

            pt = _fmt(Locale->x_fmt, t, pt, ptlim, &warn2);

            if (warn2 == IN_ALL)

              warn2 = IN_THIS;

            if (warn2 > *warnp)

              *warnp = warn2;

          }

          continue;

        case 'y':

          *warnp = IN_ALL;

          pt = _yconv(t->tm_year, TM_YEAR_BASE,

                false, true,

                pt, ptlim);

          continue;

        case 'Y':

          pt = _yconv(t->tm_year, TM_YEAR_BASE,

                true, true,

                pt, ptlim);

          continue;

        case 'Z':

          if (t->tm_zone != NULL)

            pt = _add(t->tm_zone, pt, ptlim);

          /*

           * C99 and later say that %Z must be replaced by the empty

           * string if the time zone abbreviation is not

           * determinable.

           */

          continue;

        case 'z':

          {

            long    diff;

            char const *sign;

            bool    negative;

            diff = t->TM_GMTOFF;

            negative = diff < 0;

            if (diff == 0)

            {

              if (t->tm_zone != NULL)

                negative = t->tm_zone[0] == '-';

            }

            if (negative)

            {

              sign = "-";

              diff = -diff;

            }

            else

              sign = "+";

            pt = _add(sign, pt, ptlim);

            diff /= SECSPERMIN;

            diff = (diff / MINSPERHOUR) * 100 +

              (diff % MINSPERHOUR);

            pt = _conv(diff, "%04d", pt, ptlim);

          }

          continue;

        case '+':

          pt = _fmt(Locale->date_fmt, t, pt, ptlim,

                warnp);

          continue;

        case '%':

          break;

      }

    }

    if (pt == ptlim)

      break;

    *pt++ = *format;

  }

  return pt;

}

static char *

_conv(int n, const char *format, char *pt, const char *ptlim)

{

  char    buf[INT_STRLEN_MAXIMUM(int) + 1];

  sprintf(buf, format, n);

  return _add(buf, pt, ptlim);

}

static char *

_add(const char *str, char *pt, const char *ptlim)

{

  while (pt < ptlim && (*pt = *str++) != '\0')

    ++pt;

  return pt;

}

/*

 * POSIX and the C Standard are unclear or inconsistent about

 * what %C and %y do if the year is negative or exceeds 9999.

 * Use the convention that %C concatenated with %y yields the

 * same output as %Y, and that %Y contains at least 4 bytes,

 * with more only if necessary.

 */

static char *

_yconv(int a, int b, bool convert_top, bool convert_yy,

     char *pt, const char *ptlim)

{

  int     lead;

  int     trail;

  int     DIVISOR = 100;

  trail = a % DIVISOR + b % DIVISOR;

  lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;

  trail %= DIVISOR;

  if (trail < 0 && lead > 0)

  {

    trail += DIVISOR;

    --lead;

  }

  else if (lead < 0 && trail > 0)

  {

    trail -= DIVISOR;

    ++lead;

  }

  if (convert_top)

  {

    if (lead == 0 && trail < 0)

      pt = _add("-0", pt, ptlim);

    else

      pt = _conv(lead, "%02d", pt, ptlim);

  }

  if (convert_yy)

    pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);

  return pt;

}