libc/tzcode/strftime.c

/* 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".
*/

#include "private.h"

#include <fcntl.h>
#include <locale.h>
#include <stdio.h>

#ifndef DEPRECATE_TWO_DIGIT_YEARS
# define DEPRECATE_TWO_DIGIT_YEARS false
#endif

#if defined(__BIONIC__)

/* LP32 had a 32-bit time_t, so we need to work around that here. */
#if defined(__LP64__)
#define time64_t time_t
#define mktime64 mktime
#define localtime64_r localtime_r
#else
#include <time64.h>
#endif

#include <ctype.h>

#endif

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;
};

#define Locale  (&C_time_locale)

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 *, char *, const char *, int);
static char *   _conv(int, const char *, char *, const char *);
static char *   _fmt(const char *, const struct tm *, char *, const char *,
            enum warn *);
static char *   _yconv(int, int, bool, bool, char *, const char *, int);

#ifndef YEAR_2000_NAME
#define YEAR_2000_NAME  "CHECK_STRFTIME_FORMATS_FOR_TWO_DIGIT_YEARS"
#endif /* !defined YEAR_2000_NAME */

#if HAVE_STRFTIME_L
size_t
strftime_l(char *s, size_t maxsize, char const *format, struct tm const *t,
	   locale_t locale)
{
  /* Just call strftime, as only the C locale is supported.  */
  return strftime(s, maxsize, format, t);
}
#endif

#define FORCE_LOWER_CASE 0x100 /* Android extension. */

size_t
strftime(char *s, size_t maxsize, const char *format, const struct tm *t)
{
    char *  p;
    int saved_errno = errno;
    enum warn warn = IN_NONE;

    tzset();
    p = _fmt(format, t, s, s + maxsize, &warn);
    if (!p) {
       errno = EOVERFLOW;
       return 0;
    }
    if (DEPRECATE_TWO_DIGIT_YEARS
          && warn != IN_NONE && getenv(YEAR_2000_NAME)) {
        fprintf(stderr, "\n");
        fprintf(stderr, "strftime format \"%s\" ", format);
        fprintf(stderr, "yields only two digits of years in ");
        if (warn == IN_SOME)
            fprintf(stderr, "some locales");
        else if (warn == IN_THIS)
            fprintf(stderr, "the current locale");
        else    fprintf(stderr, "all locales");
        fprintf(stderr, "\n");
    }
    if (p == s + maxsize) {
        errno = ERANGE;
        return 0;
    }
    *p = '\0';
    errno = saved_errno;
    return p - s;
}

static char *getformat(int modifier, char *normal, char *underscore,
                       char *dash, char *zero) {
    switch (modifier) {
    case '_':
        return underscore;
    case '-':
        return dash;
    case '0':
        return zero;
    }
    return normal;
}

// Android-added: fall back mechanism when TM_ZONE is not initialized.
#ifdef TM_ZONE
static const char* _safe_tm_zone(const struct tm* tm) {
  const char* zone = tm->TM_ZONE;
  if (!zone || !*zone) {
    // "The value of tm_isdst shall be positive if Daylight Savings Time is
    // in effect, 0 if Daylight Savings Time is not in effect, and negative
    // if the information is not available."
    if (tm->tm_isdst == 0) {
      zone = tzname[0];
    } else if (tm->tm_isdst > 0) {
      zone = tzname[1];
    }

    // "Replaced by the timezone name or abbreviation, or by no bytes if no
    // timezone information exists."
    if (!zone || !*zone) zone = "";
  }

  return zone;
}
#endif

static char *
_fmt(const char *format, const struct tm *t, char *pt,
        const char *ptlim, enum warn *warnp)
{
    for ( ; *format; ++format) {
        if (*format == '%') {
            int modifier = 0;
label:
            switch (*++format) {
            case '\0':
                --format;
                break;
            case 'A':
                pt = _add((t->tm_wday < 0 ||
                    t->tm_wday >= DAYSPERWEEK) ?
                    "?" : Locale->weekday[t->tm_wday],
                    pt, ptlim, modifier);
                continue;
            case 'a':
                pt = _add((t->tm_wday < 0 ||
                    t->tm_wday >= DAYSPERWEEK) ?
                    "?" : Locale->wday[t->tm_wday],
                    pt, ptlim, modifier);
                continue;
            case 'B':
                pt = _add((t->tm_mon < 0 ||
                                t->tm_mon >= MONSPERYEAR) ?
                                "?" : Locale->month[t->tm_mon],
                                pt, ptlim, modifier);
                continue;
            case 'b':
            case 'h':
                pt = _add((t->tm_mon < 0 ||
                    t->tm_mon >= MONSPERYEAR) ?
                    "?" : Locale->mon[t->tm_mon],
                    pt, ptlim, modifier);
                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, modifier);
                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, getformat(modifier, "02", " 2", "  ", "02"), 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 '_':
            case '-':
            case '0':
            case '^':
            case '#':
                modifier = *format;
                goto label;
            case 'e':
              pt = _conv(t->tm_mday, getformat(modifier, " 2", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'F':
                pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);
                continue;
            case 'H':
              pt = _conv(t->tm_hour, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'I':
              pt = _conv((t->tm_hour % 12) ? (t->tm_hour % 12) : 12,
                         getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'j':
              pt = _conv(t->tm_yday + 1, getformat(modifier, "03", " 3", "  ", "03"), 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, getformat(modifier, " 2", " 2", "  ", "02"), 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,
                           getformat(modifier, " 2", " 2", "  ", "02"), pt, ptlim);
                continue;
            case 'M':
              pt = _conv(t->tm_min, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'm':
              pt = _conv(t->tm_mon + 1, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'n':
                pt = _add("\n", pt, ptlim, modifier);
                continue;
            case 'P':
            case 'p':
                pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
                    Locale->pm :
                    Locale->am,
                    pt, ptlim, (*format == 'P') ? FORCE_LOWER_CASE : modifier);
                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, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 's':
                {
                    struct tm   tm;
                    char buf[INT_STRLEN_MAXIMUM(time64_t) + 1] __attribute__((__uninitialized__));
                    time64_t    mkt;

                    tm = *t;
                    mkt = mktime64(&tm);
					/* There is no portable, definitive
					   test for whether whether mktime
					   succeeded, so treat (time_t) -1 as
					   the success that it might be.  */
                    if (TYPE_SIGNED(time64_t)) {
                      intmax_t n = mkt;
                      sprintf(buf, "%"PRIdMAX, n);
                    } else {
                      uintmax_t n = mkt;
                      sprintf(buf, "%"PRIuMAX, n);
                    }
                    pt = _add(buf, pt, ptlim, modifier);
                }
                continue;
            case 'T':
                pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp);
                continue;
            case 't':
                pt = _add("\t", pt, ptlim, modifier);
                continue;
            case 'U':
              pt = _conv((t->tm_yday + DAYSPERWEEK - t->tm_wday) / DAYSPERWEEK,
                         getformat(modifier, "02", " 2", "  ", "02"), 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, "  ", 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;
                    }
#ifdef XPG4_1994_04_09
                    if ((w == 52 &&
                        t->tm_mon == TM_JANUARY) ||
                        (w == 1 &&
                        t->tm_mon == TM_DECEMBER))
                            w = 53;
#endif /* defined XPG4_1994_04_09 */
                    if (*format == 'V')
                      pt = _conv(w, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
                    else if (*format == 'g') {
                        *warnp = IN_ALL;
                        pt = _yconv(year, base,
                            false, true,
                            pt, ptlim, modifier);
                    } else  pt = _yconv(year, base,
                            true, true,
                            pt, ptlim, modifier);
                }
                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,
                  getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
              continue;
            case 'w':
              pt = _conv(t->tm_wday, "  ", 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, modifier);
                continue;
            case 'Y':
                pt = _yconv(t->tm_year, TM_YEAR_BASE,
                    true, true,
                    pt, ptlim, modifier);
                continue;
            case 'Z':
#ifdef TM_ZONE
                // BEGIN: Android-changed.
                pt = _add(_safe_tm_zone(t), pt, ptlim, modifier);
                // END: Android-changed.
#elif HAVE_TZNAME
                if (t->tm_isdst >= 0)
                    pt = _add(tzname[t->tm_isdst != 0],
                        pt, ptlim);
#endif
                /*
                ** C99 and later say that %Z must be
                ** replaced by the empty string if the
                ** time zone abbreviation is not
                ** determinable.
                */
                continue;
            case 'z':
#if defined TM_GMTOFF || USG_COMPAT || ALTZONE
                {
                long     diff;
                char const *    sign;
                bool negative;

# ifdef TM_GMTOFF
                diff = t->TM_GMTOFF;
# else
                /*
                ** C99 and later say that the UT offset must
                ** be computed by looking only at
                ** tm_isdst. This requirement is
                ** incorrect, since it means the code
                ** must rely on magic (in this case
                ** altzone and timezone), and the
                ** magic might not have the correct
                ** offset. Doing things correctly is
                ** tricky and requires disobeying the standard;
                ** see GNU C strftime for details.
                ** For now, punt and conform to the
                ** standard, even though it's incorrect.
                **
                ** C99 and later say that %z must be replaced by
                ** the empty string if the time zone is not
                ** determinable, so output nothing if the
                ** appropriate variables are not available.
                */
                if (t->tm_isdst < 0)
                    continue;
                if (t->tm_isdst == 0)
#  if USG_COMPAT
                    diff = -timezone;
#  else
                    continue;
#  endif
                else
#  if ALTZONE
                    diff = -altzone;
#  else
                    continue;
#  endif
# endif
                negative = diff < 0;
                if (diff == 0) {
#ifdef TM_ZONE
                  // Android-changed: do not use TM_ZONE as it is as it may be null.
                  {
                    const char* zone = _safe_tm_zone(t);
                    negative = zone[0] == '-';
                  }
#else
                    negative = t->tm_isdst < 0;
# if HAVE_TZNAME
                    if (tzname[t->tm_isdst != 0][0] == '-')
                        negative = true;
# endif
#endif
                }
                if (negative) {
                    sign = "-";
                    diff = -diff;
                } else  sign = "+";
                pt = _add(sign, pt, ptlim, modifier);
                diff /= SECSPERMIN;
                diff = (diff / MINSPERHOUR) * 100 +
                    (diff % MINSPERHOUR);
                pt = _conv(diff, getformat(modifier, "04", " 4", "  ", "04"), pt, ptlim);
                }
#endif
                continue;
            case '+':
                pt = _fmt(Locale->date_fmt, t, pt, ptlim,
                    warnp);
                continue;
            case '%':
            /*
            ** X311J/88-090 (4.12.3.5): if conversion char is
            ** undefined, behavior is undefined. Print out the
            ** character itself as printf(3) also does.
            */
            default:
                break;
            }
        }
        if (pt == ptlim)
            break;
        *pt++ = *format;
    }
    return pt;
}

static char *
_conv(int n, const char *format, char *pt, const char *ptlim)
{
  // The original implementation used snprintf(3) here, but rolling our own is
  // about 5x faster. Seems like a good trade-off for so little code, especially
  // for users like logcat that have a habit of formatting 10k times all at
  // once...

  // Format is '0' or ' ' for the fill character, followed by a single-digit
  // width or ' ' for "whatever".
  //   %d -> "  "
  //  %2d -> " 2"
  // %02d -> "02"
  char fill = format[0];
  int width = format[1] == ' ' ? 0 : format[1] - '0';

  char buf[32] __attribute__((__uninitialized__));

  // Terminate first, so we can walk backwards from the least-significant digit
  // without having to later reverse the result.
  char* p = &buf[31];
  *--p = '\0';
  char* end = p;

  // Output digits backwards, from least-significant to most.
  while (n >= 10) {
    *--p = '0' + (n % 10);
    n /= 10;
  }
  *--p = '0' + n;

  // Fill if more digits are required by the format.
  while ((end - p) < width) {
    *--p = fill;
  }

  return _add(p, pt, ptlim, 0);
}

static char *
_add(const char *str, char *pt, const char *const ptlim, int modifier)
{
        int c;

        switch (modifier) {
        case FORCE_LOWER_CASE:
                while (pt < ptlim && (*pt = tolower(*str++)) != '\0') {
                        ++pt;
                }
                break;

        case '^':
                while (pt < ptlim && (*pt = toupper(*str++)) != '\0') {
                        ++pt;
                }
                break;

        case '#':
                while (pt < ptlim && (c = *str++) != '\0') {
                        if (isupper(c)) {
                                c = tolower(c);
                        } else if (islower(c)) {
                                c = toupper(c);
                        }
                        *pt = c;
                        ++pt;
                }

                break;

        default:
                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 modifier)
{
    register int    lead;
    register int    trail;

#define 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, modifier);
        else
          pt = _conv(lead, getformat(modifier, "02", " 2", "  ", "02"), pt, ptlim);
    }
    if (convert_yy)
      pt = _conv(((trail < 0) ? -trail : trail), getformat(modifier, "02", " 2", "  ", "02"), pt,
                 ptlim);
    return pt;
}