strftime.c

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/* 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;
}