strftime.c

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/* -*- c-file-style: "linux" -*- */

/*
 * strftime.c
 *
 * Public-domain implementation of ANSI C library routine.
 *
 * It's written in old-style C for maximal portability.
 * However, since I'm used to prototypes, I've included them too.
 *
 * If you want stuff in the System V ascftime routine, add the SYSV_EXT define.
 * For extensions from SunOS, add SUNOS_EXT.
 * For stuff needed to implement the P1003.2 date command, add POSIX2_DATE.
 * For VMS dates, add VMS_EXT.
 * For a an RFC822 time format, add MAILHEADER_EXT.
 * For ISO week years, add ISO_DATE_EXT.
 * For complete POSIX semantics, add POSIX_SEMANTICS.
 *
 * The code for %c, %x, and %X now follows the 1003.2 specification for
 * the POSIX locale.
 * This version ignores LOCALE information.
 * It also doesn't worry about multi-byte characters.
 * So there.
 *
 * This file is also shipped with GAWK (GNU Awk), gawk specific bits of
 * code are included if GAWK is defined.
 *
 * Arnold Robbins
 * January, February, March, 1991
 * Updated March, April 1992
 * Updated April, 1993
 * Updated February, 1994
 * Updated May, 1994
 * Updated January, 1995
 * Updated September, 1995
 * Updated January, 1996
 *
 * Fixes from ado@elsie.nci.nih.gov
 * February 1991, May 1992
 * Fixes from Tor Lillqvist tml@tik.vtt.fi
 * May, 1993
 * Further fixes from ado@elsie.nci.nih.gov
 * February 1994
 * %z code from chip@chinacat.unicom.com
 * Applied September 1995
 * %V code fixed (again) and %G, %g added,
 * January 1996
 */

#include "ruby/ruby.h"
#include "ruby/encoding.h"
#include "timev.h"

#ifndef GAWK
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <errno.h>
#endif
#if defined(TM_IN_SYS_TIME) || !defined(GAWK)
#include <sys/types.h>
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#endif
#include <math.h>

/* defaults: season to taste */
#define SYSV_EXT        1       /* stuff in System V ascftime routine */
#define SUNOS_EXT       1       /* stuff in SunOS strftime routine */
#define POSIX2_DATE     1       /* stuff in Posix 1003.2 date command */
#define VMS_EXT         1       /* include %v for VMS date format */
#define MAILHEADER_EXT  1       /* add %z for HHMM format */
#define ISO_DATE_EXT    1       /* %G and %g for year of ISO week */

#if defined(ISO_DATE_EXT)
#if ! defined(POSIX2_DATE)
#define POSIX2_DATE     1
#endif
#endif

#if defined(POSIX2_DATE)
#if ! defined(SYSV_EXT)
#define SYSV_EXT        1
#endif
#if ! defined(SUNOS_EXT)
#define SUNOS_EXT       1
#endif
#endif

#if defined(POSIX2_DATE)
#define adddecl(stuff)  stuff
#else
#define adddecl(stuff)
#endif

#undef strchr   /* avoid AIX weirdness */

#if !defined __STDC__ && !defined _WIN32
#define const   
static int weeknumber();
adddecl(static int iso8601wknum();)
static int weeknumber_v();
adddecl(static int iso8601wknum_v();)
#else
static int weeknumber(const struct tm *timeptr, int firstweekday);
adddecl(static int iso8601wknum(const struct tm *timeptr);)
static int weeknumber_v(const struct vtm *vtm, int firstweekday);
adddecl(static int iso8601wknum_v(const struct vtm *vtm);)
#endif

#ifdef STDC_HEADERS
#include <stdlib.h>
#include <string.h>
#else
extern void *malloc();
extern void *realloc();
extern char *getenv();
extern char *strchr();
#endif

#define range(low, item, hi)    max((low), min((item), (hi)))

#undef min      /* just in case */

/* min --- return minimum of two numbers */

static inline int
min(int a, int b)
{
        return (a < b ? a : b);
}

#undef max      /* also, just in case */

/* max --- return maximum of two numbers */

static inline int
max(int a, int b)
{
        return (a > b ? a : b);
}

#ifdef NO_STRING_LITERAL_CONCATENATION
#error No string literal concatenation
#endif

#define add(x,y) (rb_funcall((x), '+', 1, (y)))
#define sub(x,y) (rb_funcall((x), '-', 1, (y)))
#define mul(x,y) (rb_funcall((x), '*', 1, (y)))
#define quo(x,y) (rb_funcall((x), rb_intern("quo"), 1, (y)))
#define div(x,y) (rb_funcall((x), rb_intern("div"), 1, (y)))
#define mod(x,y) (rb_funcall((x), '%', 1, (y)))

/* strftime --- produce formatted time */

/*
 * enc is the encoding of the format. It is used as the encoding of resulted
 * string, but the name of the month and weekday are always US-ASCII. So it
 * is only used for the timezone name on Windows.
 */
static size_t
rb_strftime_with_timespec(char *s, size_t maxsize, const char *format, rb_encoding *enc, const struct vtm *vtm, VALUE timev, struct timespec *ts, int gmt)
{
        const char *const endp = s + maxsize;
        const char *const start = s;
        const char *sp, *tp;
#define TBUFSIZE 100
        auto char tbuf[TBUFSIZE];
        long off;
        ptrdiff_t i;
        int w;
        long y;
        int precision, flags, colons;
        char padding;
        enum {LEFT, CHCASE, LOWER, UPPER};
#define BIT_OF(n) (1U<<(n))
#ifdef MAILHEADER_EXT
        int sign;
#endif

        /* various tables, useful in North America */
        static const char days_l[][10] = {
                "Sunday", "Monday", "Tuesday", "Wednesday",
                "Thursday", "Friday", "Saturday",
        };
        static const char months_l[][10] = {
                "January", "February", "March", "April",
                "May", "June", "July", "August", "September",
                "October", "November", "December",
        };
        static const char ampm[][3] = { "AM", "PM", };

        if (s == NULL || format == NULL || vtm == NULL || maxsize == 0)
                return 0;

        /* quick check if we even need to bother */
        if (strchr(format, '%') == NULL && strlen(format) + 1 >= maxsize) {
        err:
                errno = ERANGE;
                return 0;
        }

        if (enc && (enc == rb_usascii_encoding() ||
            enc == rb_ascii8bit_encoding() || enc == rb_locale_encoding())) {
            enc = NULL;
        }

        for (; *format && s < endp - 1; format++) {
#define FLAG_FOUND() do { \
                        if (precision > 0) \
                                goto unknown; \
                } while (0)
#define NEEDS(n) do if (s >= endp || (n) >= endp - s - 1) goto err; while (0)
#define FILL_PADDING(i) do { \
        if (!(flags & BIT_OF(LEFT)) && precision > (i)) { \
                NEEDS(precision); \
                memset(s, padding ? padding : ' ', precision - (i)); \
                s += precision - (i); \
        } \
        else { \
                NEEDS(i); \
        } \
} while (0);
#define FMT(def_pad, def_prec, fmt, val) \
                do { \
                        int l; \
                        if (precision <= 0) precision = (def_prec); \
                        if (flags & BIT_OF(LEFT)) precision = 1; \
                        l = snprintf(s, endp - s, \
                                     ((padding == '0' || (!padding && (def_pad) == '0')) ? "%0*"fmt : "%*"fmt), \
                                     precision, (val)); \
                        if (l < 0) goto err; \
                        s += l; \
                } while (0)
#define STRFTIME(fmt) \
                do { \
                        i = rb_strftime_with_timespec(s, endp - s, (fmt), enc, vtm, timev, ts, gmt); \
                        if (!i) return 0; \
                        if (precision > i) {\
                                NEEDS(precision); \
                                memmove(s + precision - i, s, i);\
                                memset(s, padding ? padding : ' ', precision - i); \
                                s += precision; \
                        }\
                        else s += i; \
                } while (0)
#define FMTV(def_pad, def_prec, fmt, val) \
                do { \
                        VALUE tmp = (val); \
                        if (FIXNUM_P(tmp)) { \
                                FMT((def_pad), (def_prec), "l"fmt, FIX2LONG(tmp)); \
                        } \
                        else { \
                                VALUE args[2], result; \
                                size_t l; \
                                if (precision <= 0) precision = (def_prec); \
                                if (flags & BIT_OF(LEFT)) precision = 1; \
                                args[0] = INT2FIX(precision); \
                                args[1] = (val); \
                                if (padding == '0' || (!padding && (def_pad) == '0')) \
                                        result = rb_str_format(2, args, rb_str_new2("%0*"fmt)); \
                                else \
                                        result = rb_str_format(2, args, rb_str_new2("%*"fmt)); \
                                l = strlcpy(s, StringValueCStr(result), endp-s); \
                                if ((size_t)(endp-s) <= l) \
                                        goto err; \
                                s += l; \
                        } \
                } while (0)

                if (*format != '%') {
                        *s++ = *format;
                        continue;
                }
                tp = tbuf;
                sp = format;
                precision = -1;
                flags = 0;
                padding = 0;
                colons = 0;
        again:
                switch (*++format) {
                case '\0':
                        format--;
                        goto unknown;

                case '%':
                        FILL_PADDING(1);
                        *s++ = '%';
                        continue;

                case 'a':       /* abbreviated weekday name */
                        if (flags & BIT_OF(CHCASE)) {
                                flags &= ~(BIT_OF(LOWER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(UPPER);
                        }
                        if (vtm->wday < 0 || vtm->wday > 6)
                                i = 1, tp = "?";
                        else
                                i = 3, tp = days_l[vtm->wday];
                        break;

                case 'A':       /* full weekday name */
                        if (flags & BIT_OF(CHCASE)) {
                                flags &= ~(BIT_OF(LOWER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(UPPER);
                        }
                        if (vtm->wday < 0 || vtm->wday > 6)
                                i = 1, tp = "?";
                        else
                                i = strlen(tp = days_l[vtm->wday]);
                        break;

#ifdef SYSV_EXT
                case 'h':       /* abbreviated month name */
#endif
                case 'b':       /* abbreviated month name */
                        if (flags & BIT_OF(CHCASE)) {
                                flags &= ~(BIT_OF(LOWER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(UPPER);
                        }
                        if (vtm->mon < 1 || vtm->mon > 12)
                                i = 1, tp = "?";
                        else
                                i = 3, tp = months_l[vtm->mon-1];
                        break;

                case 'B':       /* full month name */
                        if (flags & BIT_OF(CHCASE)) {
                                flags &= ~(BIT_OF(LOWER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(UPPER);
                        }
                        if (vtm->mon < 1 || vtm->mon > 12)
                                i = 1, tp = "?";
                        else
                                i = strlen(tp = months_l[vtm->mon-1]);
                        break;

                case 'c':       /* appropriate date and time representation */
                        STRFTIME("%a %b %e %H:%M:%S %Y");
                        continue;

                case 'd':       /* day of the month, 01 - 31 */
                        i = range(1, vtm->mday, 31);
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'H':       /* hour, 24-hour clock, 00 - 23 */
                        i = range(0, vtm->hour, 23);
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'I':       /* hour, 12-hour clock, 01 - 12 */
                        i = range(0, vtm->hour, 23);
                        if (i == 0)
                                i = 12;
                        else if (i > 12)
                                i -= 12;
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'j':       /* day of the year, 001 - 366 */
                        i = range(1, vtm->yday, 366);
                        FMT('0', 3, "d", (int)i);
                        continue;

                case 'm':       /* month, 01 - 12 */
                        i = range(1, vtm->mon, 12);
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'M':       /* minute, 00 - 59 */
                        i = range(0, vtm->min, 59);
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'p':       /* AM or PM based on 12-hour clock */
                case 'P':       /* am or pm based on 12-hour clock */
                        if ((*format == 'p' && (flags & BIT_OF(CHCASE))) ||
                            (*format == 'P' && !(flags & (BIT_OF(CHCASE)|BIT_OF(UPPER))))) {
                                flags &= ~(BIT_OF(UPPER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(LOWER);
                        }
                        i = range(0, vtm->hour, 23);
                        if (i < 12)
                                tp = ampm[0];
                        else
                                tp = ampm[1];
                        i = 2;
                        break;

                case 's':
                        if (ts) {
                                time_t sec = ts->tv_sec;
                                if (~(time_t)0 <= 0)
                                    FMT('0', 1, PRI_TIMET_PREFIX"d", sec);
                                else
                                    FMT('0', 1, PRI_TIMET_PREFIX"u", sec);
                        }
                        else {
                                VALUE sec = div(timev, INT2FIX(1));
                                FMTV('0', 1, "d", sec);
                        }
                        continue;

                case 'S':       /* second, 00 - 60 */
                        i = range(0, vtm->sec, 60);
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'U':       /* week of year, Sunday is first day of week */
                        FMT('0', 2, "d", weeknumber_v(vtm, 0));
                        continue;

                case 'w':       /* weekday, Sunday == 0, 0 - 6 */
                        i = range(0, vtm->wday, 6);
                        FMT('0', 1, "d", (int)i);
                        continue;

                case 'W':       /* week of year, Monday is first day of week */
                        FMT('0', 2, "d", weeknumber_v(vtm, 1));
                        continue;

                case 'x':       /* appropriate date representation */
                        STRFTIME("%m/%d/%y");
                        continue;

                case 'X':       /* appropriate time representation */
                        STRFTIME("%H:%M:%S");
                        continue;

                case 'y':       /* year without a century, 00 - 99 */
                        i = NUM2INT(mod(vtm->year, INT2FIX(100)));
                        FMT('0', 2, "d", (int)i);
                        continue;

                case 'Y':       /* year with century */
                        if (FIXNUM_P(vtm->year)) {
                                long y = FIX2LONG(vtm->year);
                                FMT('0', 0 <= y ? 4 : 5, "ld", y);
                        }
                        else {
                                FMTV('0', 4, "d", vtm->year);
                        }
                        continue;

#ifdef MAILHEADER_EXT
                case 'z':       /* time zone offset east of GMT e.g. -0600 */
                        if (gmt) {
                                off = 0;
                        }
                        else {
                                off = NUM2LONG(rb_funcall(vtm->utc_offset, rb_intern("round"), 0));
                        }
                        if (off < 0) {
                                off = -off;
                                sign = -1;
                        } else {
                                sign = +1;
                        }
                        switch (colons) {
                        case 0: /* %z -> +hhmm */
                                precision = precision <= 5 ? 2 : precision-3;
                                NEEDS(precision + 3);
                                break;

                        case 1: /* %:z -> +hh:mm */
                                precision = precision <= 6 ? 2 : precision-4;
                                NEEDS(precision + 4);
                                break;

                        case 2: /* %::z -> +hh:mm:ss */
                                precision = precision <= 9 ? 2 : precision-7;
                                NEEDS(precision + 7);
                                break;

                        case 3: /* %:::z -> +hh[:mm[:ss]] */
                                if (off % 3600 == 0) {
                                        precision = precision <= 3 ? 2 : precision-1;
                                        NEEDS(precision + 3);
                                }
                                else if (off % 60 == 0) {
                                        precision = precision <= 6 ? 2 : precision-4;
                                        NEEDS(precision + 4);
                                }
                                else {
                                        precision = precision <= 9 ? 2 : precision-7;
                                        NEEDS(precision + 9);
                                }
                                break;

                        default:
                                format--;
                                goto unknown;
                        }
                        i = snprintf(s, endp - s, (padding == ' ' ? "%+*ld" : "%+.*ld"),
                                     precision + 1, sign * (off / 3600));
                        if (i < 0) goto err;
                        if (sign < 0 && off < 3600) {
                                *(padding == ' ' ? s + i - 2 : s) = '-';
                        }
                        s += i;
                        off = off % 3600;
                        if (colons == 3 && off == 0)
                                continue;
                        if (1 <= colons)
                            *s++ = ':';
                        i = snprintf(s, endp - s, "%02d", (int)(off / 60));
                        if (i < 0) goto err;
                        s += i;
                        off = off % 60;
                        if (colons == 3 && off == 0)
                                continue;
                        if (2 <= colons) {
                            *s++ = ':';
                            i = snprintf(s, endp - s, "%02d", (int)off);
                            if (i < 0) goto err;
                            s += i;
                        }
                        continue;
#endif /* MAILHEADER_EXT */

                case 'Z':       /* time zone name or abbreviation */
                        if (flags & BIT_OF(CHCASE)) {
                                flags &= ~(BIT_OF(UPPER)|BIT_OF(CHCASE));
                                flags |= BIT_OF(LOWER);
                        }
                        if (gmt) {
                                i = 3;
                                tp = "UTC";
                                break;
                        }
                        if (vtm->zone == NULL) {
                            i = 0;
                        }
                        else {
                            tp = vtm->zone;
                            if (enc) {
                                for (i = 0; i < TBUFSIZE && tp[i]; i++) {
                                    if ((unsigned char)tp[i] > 0x7F) {
                                        VALUE str = rb_str_conv_enc_opts(rb_str_new_cstr(tp), rb_locale_encoding(), enc, ECONV_UNDEF_REPLACE|ECONV_INVALID_REPLACE, Qnil);
                                        i = strlcpy(tbuf, RSTRING_PTR(str), TBUFSIZE);
                                        tp = tbuf;
                                        break;
                                    }
                                }
                            }
                            else
                                i = strlen(tp);
                        }
                        break;

#ifdef SYSV_EXT
                case 'n':       /* same as \n */
                        FILL_PADDING(1);
                        *s++ = '\n';
                        continue;

                case 't':       /* same as \t */
                        FILL_PADDING(1);
                        *s++ = '\t';
                        continue;

                case 'D':       /* date as %m/%d/%y */
                        STRFTIME("%m/%d/%y");
                        continue;

                case 'e':       /* day of month, blank padded */
                        FMT(' ', 2, "d", range(1, vtm->mday, 31));
                        continue;

                case 'r':       /* time as %I:%M:%S %p */
                        STRFTIME("%I:%M:%S %p");
                        continue;

                case 'R':       /* time as %H:%M */
                        STRFTIME("%H:%M");
                        continue;

                case 'T':       /* time as %H:%M:%S */
                        STRFTIME("%H:%M:%S");
                        continue;
#endif

#ifdef SUNOS_EXT
                case 'k':       /* hour, 24-hour clock, blank pad */
                        i = range(0, vtm->hour, 23);
                        FMT(' ', 2, "d", (int)i);
                        continue;

                case 'l':       /* hour, 12-hour clock, 1 - 12, blank pad */
                        i = range(0, vtm->hour, 23);
                        if (i == 0)
                                i = 12;
                        else if (i > 12)
                                i -= 12;
                        FMT(' ', 2, "d", (int)i);
                        continue;
#endif


#ifdef VMS_EXT
                case 'v':       /* date as dd-bbb-YYYY */
                        STRFTIME("%e-%^b-%4Y");
                        continue;
#endif


#ifdef POSIX2_DATE
                case 'C':
                        FMTV('0', 2, "d", div(vtm->year, INT2FIX(100)));
                        continue;

                case 'E':
                        /* POSIX locale extensions, ignored for now */
                        if (!format[1] || !strchr("cCxXyY", format[1]))
                                goto unknown;
                        goto again;
                case 'O':
                        /* POSIX locale extensions, ignored for now */
                        if (!format[1] || !strchr("deHkIlmMSuUVwWy", format[1]))
                                goto unknown;
                        goto again;

                case 'V':       /* week of year according ISO 8601 */
                        FMT('0', 2, "d", iso8601wknum_v(vtm));
                        continue;

                case 'u':
                /* ISO 8601: Weekday as a decimal number [1 (Monday) - 7] */
                        FMT('0', 1, "d", vtm->wday == 0 ? 7 : vtm->wday);
                        continue;
#endif  /* POSIX2_DATE */

#ifdef ISO_DATE_EXT
                case 'G':
                case 'g':
                        /*
                         * Year of ISO week.
                         *
                         * If it's December but the ISO week number is one,
                         * that week is in next year.
                         * If it's January but the ISO week number is 52 or
                         * 53, that week is in last year.
                         * Otherwise, it's this year.
                         */
                        {
                                VALUE yv = vtm->year;
                                w = iso8601wknum_v(vtm);
                                if (vtm->mon == 12 && w == 1)
                                        yv = add(yv, INT2FIX(1));
                                else if (vtm->mon == 1 && w >= 52)
                                        yv = sub(yv, INT2FIX(1));

                                if (*format == 'G') {
                                        if (FIXNUM_P(yv)) {
                                                const long y = FIX2LONG(yv);
                                                FMT('0', 0 <= y ? 4 : 5, "ld", y);
                                        }
                                        else {
                                                FMTV('0', 4, "d", yv);
                                        }
                                }
                                else {
                                        yv = mod(yv, INT2FIX(100));
                                        y = FIX2LONG(yv);
                                        FMT('0', 2, "ld", y);
                                }
                                continue;
                        }

#endif /* ISO_DATE_EXT */


                case 'L':
                        w = 3;
                        goto subsec;

                case 'N':
                        /*
                         * fractional second digits. default is 9 digits
                         * (nanosecond).
                         *
                         * %3N  millisecond (3 digits)
                         * %6N  microsecond (6 digits)
                         * %9N  nanosecond (9 digits)
                         */
                        w = 9;
                subsec:
                        if (precision <= 0) {
                            precision = w;
                        }
                        NEEDS(precision);

                        if (ts) {
                                long subsec = ts->tv_nsec;
                                if (9 < precision) {
                                        snprintf(s, endp - s, "%09ld", subsec);
                                        memset(s+9, '0', precision-9);
                                        s += precision;
                                }
                                else {
                                        int i;
                                        for (i = 0; i < 9-precision; i++)
                                                subsec /= 10;
                                        snprintf(s, endp - s, "%0*ld", precision, subsec);
                                        s += precision;
                                }
                        }
                        else {
                                VALUE subsec = mod(timev, INT2FIX(1));
                                int ww;
                                long n;

                                ww = precision;
                                while (9 <= ww) {
                                        subsec = mul(subsec, INT2FIX(1000000000));
                                        ww -= 9;
                                }
                                n = 1;
                                for (; 0 < ww; ww--)
                                        n *= 10;
                                if (n != 1)
                                        subsec = mul(subsec, INT2FIX(n));
                                subsec = div(subsec, INT2FIX(1));

                                if (FIXNUM_P(subsec)) {
                                        (void)snprintf(s, endp - s, "%0*ld", precision, FIX2LONG(subsec));
                                        s += precision;
                                }
                                else {
                                        VALUE args[2], result;
                                        args[0] = INT2FIX(precision);
                                        args[1] = subsec;
                                        result = rb_str_format(2, args, rb_str_new2("%0*d"));
                                        (void)strlcpy(s, StringValueCStr(result), endp-s);
                                        s += precision;
                                }
                        }
                        continue;

                case 'F':       /*  Equivalent to %Y-%m-%d */
                        STRFTIME("%Y-%m-%d");
                        continue;

                case '-':
                        FLAG_FOUND();
                        flags |= BIT_OF(LEFT);
                        padding = precision = 0;
                        goto again;

                case '^':
                        FLAG_FOUND();
                        flags |= BIT_OF(UPPER);
                        goto again;

                case '#':
                        FLAG_FOUND();
                        flags |= BIT_OF(CHCASE);
                        goto again;

                case '_':
                        FLAG_FOUND();
                        padding = ' ';
                        goto again;

                case ':':
                        {
                                size_t l = strspn(format, ":");
                                if (l > 3 || format[l] != 'z') goto unknown;
                                colons = (int)l;
                                format += l - 1;
                        }
                        goto again;

                case '0':
                        padding = '0';
                case '1':  case '2': case '3': case '4':
                case '5': case '6':  case '7': case '8': case '9':
                        {
                                char *e;
                                precision = (int)strtoul(format, &e, 10);
                                format = e - 1;
                                goto again;
                        }

                default:
                unknown:
                        i = format - sp + 1;
                        tp = sp;
                        precision = -1;
                        flags = 0;
                        padding = 0;
                        colons = 0;
                        break;
                }
                if (i) {
                        FILL_PADDING(i);
                        memcpy(s, tp, i);
                        switch (flags & (BIT_OF(UPPER)|BIT_OF(LOWER))) {
                        case BIT_OF(UPPER):
                                do {
                                        if (ISLOWER(*s)) *s = TOUPPER(*s);
                                } while (s++, --i);
                                break;
                        case BIT_OF(LOWER):
                                do {
                                        if (ISUPPER(*s)) *s = TOLOWER(*s);
                                } while (s++, --i);
                                break;
                        default:
                                s += i;
                                break;
                        }
                }
        }
        if (s >= endp) {
                goto err;
        }
        if (*format == '\0') {
                *s = '\0';
                return (s - start);
        } else
                return 0;
}

size_t
rb_strftime(char *s, size_t maxsize, const char *format, rb_encoding *enc, const struct vtm *vtm, VALUE timev, int gmt)
{
    return rb_strftime_with_timespec(s, maxsize, format, enc, vtm, timev, NULL, gmt);
}

size_t
rb_strftime_timespec(char *s, size_t maxsize, const char *format, rb_encoding *enc, const struct vtm *vtm, struct timespec *ts, int gmt)
{
    return rb_strftime_with_timespec(s, maxsize, format, enc, vtm, Qnil, ts, gmt);
}

/* isleap --- is a year a leap year? */

static int
isleap(long year)
{
        return ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
}


static void
vtm2tm_noyear(const struct vtm *vtm, struct tm *result)
{
    struct tm tm;

    /* for isleap() in iso8601wknum.  +100 is -1900 (mod 400). */
    tm.tm_year = FIX2INT(mod(vtm->year, INT2FIX(400))) + 100;

    tm.tm_mon = vtm->mon-1;
    tm.tm_mday = vtm->mday;
    tm.tm_hour = vtm->hour;
    tm.tm_min = vtm->min;
    tm.tm_sec = vtm->sec;
    tm.tm_wday = vtm->wday;
    tm.tm_yday = vtm->yday-1;
    tm.tm_isdst = vtm->isdst;
#if defined(HAVE_STRUCT_TM_TM_GMTOFF)
    tm.tm_gmtoff = NUM2LONG(vtm->utc_offset);
#endif
#if defined(HAVE_TM_ZONE)
    tm.tm_zone = (char *)vtm->zone;
#endif
    *result = tm;
}

#ifdef POSIX2_DATE
/* iso8601wknum --- compute week number according to ISO 8601 */

static int
iso8601wknum(const struct tm *timeptr)
{
        /*
         * From 1003.2:
         *      If the week (Monday to Sunday) containing January 1
         *      has four or more days in the new year, then it is week 1;
         *      otherwise it is the highest numbered week of the previous
         *      year (52 or 53), and the next week is week 1.
         *
         * ADR: This means if Jan 1 was Monday through Thursday,
         *      it was week 1, otherwise week 52 or 53.
         *
         * XPG4 erroneously included POSIX.2 rationale text in the
         * main body of the standard. Thus it requires week 53.
         */

        int weeknum, jan1day;

        /* get week number, Monday as first day of the week */
        weeknum = weeknumber(timeptr, 1);

        /*
         * With thanks and tip of the hatlo to tml@tik.vtt.fi
         *
         * What day of the week does January 1 fall on?
         * We know that
         *      (timeptr->tm_yday - jan1.tm_yday) MOD 7 ==
         *              (timeptr->tm_wday - jan1.tm_wday) MOD 7
         * and that
         *      jan1.tm_yday == 0
         * and that
         *      timeptr->tm_wday MOD 7 == timeptr->tm_wday
         * from which it follows that. . .
         */
        jan1day = timeptr->tm_wday - (timeptr->tm_yday % 7);
        if (jan1day < 0)
                jan1day += 7;

        /*
         * If Jan 1 was a Monday through Thursday, it was in
         * week 1.  Otherwise it was last year's highest week, which is
         * this year's week 0.
         *
         * What does that mean?
         * If Jan 1 was Monday, the week number is exactly right, it can
         *      never be 0.
         * If it was Tuesday through Thursday, the weeknumber is one
         *      less than it should be, so we add one.
         * Otherwise, Friday, Saturday or Sunday, the week number is
         * OK, but if it is 0, it needs to be 52 or 53.
         */
        switch (jan1day) {
        case 1:         /* Monday */
                break;
        case 2:         /* Tuesday */
        case 3:         /* Wednesday */
        case 4:         /* Thursday */
                weeknum++;
                break;
        case 5:         /* Friday */
        case 6:         /* Saturday */
        case 0:         /* Sunday */
                if (weeknum == 0) {
#ifdef USE_BROKEN_XPG4
                        /* XPG4 (as of March 1994) says 53 unconditionally */
                        weeknum = 53;
#else
                        /* get week number of last week of last year */
                        struct tm dec31ly;      /* 12/31 last year */
                        dec31ly = *timeptr;
                        dec31ly.tm_year--;
                        dec31ly.tm_mon = 11;
                        dec31ly.tm_mday = 31;
                        dec31ly.tm_wday = (jan1day == 0) ? 6 : jan1day - 1;
                        dec31ly.tm_yday = 364 + isleap(dec31ly.tm_year + 1900L);
                        weeknum = iso8601wknum(& dec31ly);
#endif
                }
                break;
        }

        if (timeptr->tm_mon == 11) {
                /*
                 * The last week of the year
                 * can be in week 1 of next year.
                 * Sigh.
                 *
                 * This can only happen if
                 *      M   T  W
                 *      29  30 31
                 *      30  31
                 *      31
                 */
                int wday, mday;

                wday = timeptr->tm_wday;
                mday = timeptr->tm_mday;
                if (   (wday == 1 && (mday >= 29 && mday <= 31))
                    || (wday == 2 && (mday == 30 || mday == 31))
                    || (wday == 3 &&  mday == 31))
                        weeknum = 1;
        }

        return weeknum;
}

static int
iso8601wknum_v(const struct vtm *vtm)
{
        struct tm tm;
        vtm2tm_noyear(vtm, &tm);
        return iso8601wknum(&tm);
}

#endif

/* weeknumber --- figure how many weeks into the year */

/* With thanks and tip of the hatlo to ado@elsie.nci.nih.gov */

static int
weeknumber(const struct tm *timeptr, int firstweekday)
{
        int wday = timeptr->tm_wday;
        int ret;

        if (firstweekday == 1) {
                if (wday == 0)  /* sunday */
                        wday = 6;
                else
                        wday--;
        }
        ret = ((timeptr->tm_yday + 7 - wday) / 7);
        if (ret < 0)
                ret = 0;
        return ret;
}

static int
weeknumber_v(const struct vtm *vtm, int firstweekday)
{
        struct tm tm;
        vtm2tm_noyear(vtm, &tm);
        return weeknumber(&tm, firstweekday);
}

#if 0
/* ADR --- I'm loathe to mess with ado's code ... */

Date:         Wed, 24 Apr 91 20:54:08 MDT
From: Michal Jaegermann <audfax!emory!vm.ucs.UAlberta.CA!NTOMCZAK>
To: arnold@audiofax.com

Hi Arnold,
in a process of fixing of strftime() in libraries on Atari ST I grabbed
some pieces of code from your own strftime.  When doing that it came
to mind that your weeknumber() function compiles a little bit nicer
in the following form:
/*
 * firstweekday is 0 if starting in Sunday, non-zero if in Monday
 */
{
    return (timeptr->tm_yday - timeptr->tm_wday +
            (firstweekday ? (timeptr->tm_wday ? 8 : 1) : 7)) / 7;
}
How nicer it depends on a compiler, of course, but always a tiny bit.

   Cheers,
   Michal
   ntomczak@vm.ucs.ualberta.ca
#endif

#ifdef  TEST_STRFTIME

/*
 * NAME:
 *      tst
 *
 * SYNOPSIS:
 *      tst
 *
 * DESCRIPTION:
 *      "tst" is a test driver for the function "strftime".
 *
 * OPTIONS:
 *      None.
 *
 * AUTHOR:
 *      Karl Vogel
 *      Control Data Systems, Inc.
 *      vogelke@c-17igp.wpafb.af.mil
 *
 * BUGS:
 *      None noticed yet.
 *
 * COMPILE:
 *      cc -o tst -DTEST_STRFTIME strftime.c
 */

/* ADR: I reformatted this to my liking, and deleted some unneeded code. */

#ifndef NULL
#include        <stdio.h>
#endif
#include        <sys/time.h>
#include        <string.h>

#define         MAXTIME         132

/*
 * Array of time formats.
 */

static char *array[] =
{
        "(%%A)      full weekday name, var length (Sunday..Saturday)  %A",
        "(%%B)       full month name, var length (January..December)  %B",
        "(%%C)                                               Century  %C",
        "(%%D)                                       date (%%m/%%d/%%y)  %D",
        "(%%E)                           Locale extensions (ignored)  %E",
        "(%%H)                          hour (24-hour clock, 00..23)  %H",
        "(%%I)                          hour (12-hour clock, 01..12)  %I",
        "(%%M)                                       minute (00..59)  %M",
        "(%%O)                           Locale extensions (ignored)  %O",
        "(%%R)                                 time, 24-hour (%%H:%%M)  %R",
        "(%%S)                                       second (00..60)  %S",
        "(%%T)                              time, 24-hour (%%H:%%M:%%S)  %T",
        "(%%U)    week of year, Sunday as first day of week (00..53)  %U",
        "(%%V)                    week of year according to ISO 8601  %V",
        "(%%W)    week of year, Monday as first day of week (00..53)  %W",
        "(%%X)     appropriate locale time representation (%H:%M:%S)  %X",
        "(%%Y)                           year with century (1970...)  %Y",
        "(%%Z) timezone (EDT), or blank if timezone not determinable  %Z",
        "(%%a)          locale's abbreviated weekday name (Sun..Sat)  %a",
        "(%%b)            locale's abbreviated month name (Jan..Dec)  %b",
        "(%%c)           full date (Sat Nov  4 12:02:33 1989)%n%t%t%t  %c",
        "(%%d)                             day of the month (01..31)  %d",
        "(%%e)               day of the month, blank-padded ( 1..31)  %e",
        "(%%h)                                should be same as (%%b)  %h",
        "(%%j)                            day of the year (001..366)  %j",
        "(%%k)               hour, 24-hour clock, blank pad ( 0..23)  %k",
        "(%%l)               hour, 12-hour clock, blank pad ( 1..12)  %l",
        "(%%m)                                        month (01..12)  %m",
        "(%%p)              locale's AM or PM based on 12-hour clock  %p",
        "(%%r)                   time, 12-hour (same as %%I:%%M:%%S %%p)  %r",
        "(%%u) ISO 8601: Weekday as decimal number [1 (Monday) - 7]   %u",
        "(%%v)                                VMS date (dd-bbb-YYYY)  %v",
        "(%%w)                       day of week (0..6, Sunday == 0)  %w",
        "(%%x)                appropriate locale date representation  %x",
        "(%%y)                      last two digits of year (00..99)  %y",
        "(%%z)      timezone offset east of GMT as HHMM (e.g. -0500)  %z",
        (char *) NULL
};

/* main routine. */

int
main(int argc, char **argv)
{
        long time();

        char *next;
        char string[MAXTIME];

        int k;
        int length;

        struct tm *tm;

        long clock;

        /* Call the function. */

        clock = time((long *) 0);
        tm = localtime(&clock);

        for (k = 0; next = array[k]; k++) {
                length = strftime(string, MAXTIME, next, tm);
                printf("%s\n", string);
        }

        exit(0);
}
#endif  /* TEST_STRFTIME */

---