buildsys: switch source download to quincy

[ceph.git] / ceph / src / civetweb / src / third_party / duktape-1.8.0 / src-separate / duk_bi_date.c

/*
 *  Date built-ins
 *
 *  Unlike most built-ins, Date has some platform dependencies for getting
 *  UTC time, converting between UTC and local time, and parsing and
 *  formatting time values.  These are all abstracted behind DUK_USE_xxx
 *  config options.  There are built-in platform specific providers for
 *  POSIX and Windows, but external providers can also be used.
 *
 *  See doc/datetime.rst.
 *
 */

#include "duk_internal.h"

/*
 *  Forward declarations
 */

DUK_LOCAL_DECL duk_double_t duk__push_this_get_timeval_tzoffset(duk_context *ctx, duk_small_uint_t flags, duk_int_t *out_tzoffset);
DUK_LOCAL_DECL duk_double_t duk__push_this_get_timeval(duk_context *ctx, duk_small_uint_t flags);
DUK_LOCAL_DECL void duk__twodigit_year_fixup(duk_context *ctx, duk_idx_t idx_val);
DUK_LOCAL_DECL duk_ret_t duk__set_this_timeval_from_dparts(duk_context *ctx, duk_double_t *dparts, duk_small_uint_t flags);

/*
 *  Other file level defines
 */

/* Debug macro to print all parts and dparts (used manually because of debug level). */
#define  DUK__DPRINT_PARTS_AND_DPARTS(parts,dparts)  do { \
                DUK_D(DUK_DPRINT("parts: %ld %ld %ld %ld %ld %ld %ld %ld, dparts: %lf %lf %lf %lf %lf %lf %lf %lf", \
                                 (long) (parts)[0], (long) (parts)[1], \
                                 (long) (parts)[2], (long) (parts)[3], \
                                 (long) (parts)[4], (long) (parts)[5], \
                                 (long) (parts)[6], (long) (parts)[7], \
                                 (double) (dparts)[0], (double) (dparts)[1], \
                                 (double) (dparts)[2], (double) (dparts)[3], \
                                 (double) (dparts)[4], (double) (dparts)[5], \
                                 (double) (dparts)[6], (double) (dparts)[7])); \
        } while (0)
#define  DUK__DPRINT_PARTS(parts)  do { \
                DUK_D(DUK_DPRINT("parts: %ld %ld %ld %ld %ld %ld %ld %ld", \
                                 (long) (parts)[0], (long) (parts)[1], \
                                 (long) (parts)[2], (long) (parts)[3], \
                                 (long) (parts)[4], (long) (parts)[5], \
                                 (long) (parts)[6], (long) (parts)[7])); \
        } while (0)
#define  DUK__DPRINT_DPARTS(dparts)  do { \
                DUK_D(DUK_DPRINT("dparts: %lf %lf %lf %lf %lf %lf %lf %lf", \
                                 (double) (dparts)[0], (double) (dparts)[1], \
                                 (double) (dparts)[2], (double) (dparts)[3], \
                                 (double) (dparts)[4], (double) (dparts)[5], \
                                 (double) (dparts)[6], (double) (dparts)[7])); \
        } while (0)

/* Equivalent year for DST calculations outside [1970,2038[ range, see
 * E5 Section 15.9.1.8.  Equivalent year has the same leap-year-ness and
 * starts with the same weekday on Jan 1.
 * https://bugzilla.mozilla.org/show_bug.cgi?id=351066
 */
#define DUK__YEAR(x) ((duk_uint8_t) ((x) - 1970))
DUK_LOCAL duk_uint8_t duk__date_equivyear[14] = {
#if 1
        /* This is based on V8 EquivalentYear() algorithm (see src/genequivyear.py):
         * http://code.google.com/p/v8/source/browse/trunk/src/date.h#146
         */

        /* non-leap year: sunday, monday, ... */
        DUK__YEAR(2023), DUK__YEAR(2035), DUK__YEAR(2019), DUK__YEAR(2031),
        DUK__YEAR(2015), DUK__YEAR(2027), DUK__YEAR(2011),

        /* leap year: sunday, monday, ... */
        DUK__YEAR(2012), DUK__YEAR(2024), DUK__YEAR(2008), DUK__YEAR(2020),
        DUK__YEAR(2032), DUK__YEAR(2016), DUK__YEAR(2028)
#endif

#if 0
        /* This is based on Rhino EquivalentYear() algorithm:
         * https://github.com/mozilla/rhino/blob/f99cc11d616f0cdda2c42bde72b3484df6182947/src/org/mozilla/javascript/NativeDate.java
         */

        /* non-leap year: sunday, monday, ... */
        DUK__YEAR(1978), DUK__YEAR(1973), DUK__YEAR(1985), DUK__YEAR(1986),
        DUK__YEAR(1981), DUK__YEAR(1971), DUK__YEAR(1977),

        /* leap year: sunday, monday, ... */
        DUK__YEAR(1984), DUK__YEAR(1996), DUK__YEAR(1980), DUK__YEAR(1992),
        DUK__YEAR(1976), DUK__YEAR(1988), DUK__YEAR(1972)
#endif
};
#undef DUK__YEAR

/*
 *  ISO 8601 subset parser.
 */

/* Parser part count. */
#define DUK__NUM_ISO8601_PARSER_PARTS  9

/* Parser part indices. */
#define DUK__PI_YEAR         0
#define DUK__PI_MONTH        1
#define DUK__PI_DAY          2
#define DUK__PI_HOUR         3
#define DUK__PI_MINUTE       4
#define DUK__PI_SECOND       5
#define DUK__PI_MILLISECOND  6
#define DUK__PI_TZHOUR       7
#define DUK__PI_TZMINUTE     8

/* Parser part masks. */
#define DUK__PM_YEAR         (1 << DUK__PI_YEAR)
#define DUK__PM_MONTH        (1 << DUK__PI_MONTH)
#define DUK__PM_DAY          (1 << DUK__PI_DAY)
#define DUK__PM_HOUR         (1 << DUK__PI_HOUR)
#define DUK__PM_MINUTE       (1 << DUK__PI_MINUTE)
#define DUK__PM_SECOND       (1 << DUK__PI_SECOND)
#define DUK__PM_MILLISECOND  (1 << DUK__PI_MILLISECOND)
#define DUK__PM_TZHOUR       (1 << DUK__PI_TZHOUR)
#define DUK__PM_TZMINUTE     (1 << DUK__PI_TZMINUTE)

/* Parser separator indices. */
#define DUK__SI_PLUS         0
#define DUK__SI_MINUS        1
#define DUK__SI_T            2
#define DUK__SI_SPACE        3
#define DUK__SI_COLON        4
#define DUK__SI_PERIOD       5
#define DUK__SI_Z            6
#define DUK__SI_NUL          7

/* Parser separator masks. */
#define DUK__SM_PLUS         (1 << DUK__SI_PLUS)
#define DUK__SM_MINUS        (1 << DUK__SI_MINUS)
#define DUK__SM_T            (1 << DUK__SI_T)
#define DUK__SM_SPACE        (1 << DUK__SI_SPACE)
#define DUK__SM_COLON        (1 << DUK__SI_COLON)
#define DUK__SM_PERIOD       (1 << DUK__SI_PERIOD)
#define DUK__SM_Z            (1 << DUK__SI_Z)
#define DUK__SM_NUL          (1 << DUK__SI_NUL)

/* Rule control flags. */
#define DUK__CF_NEG          (1 << 0)  /* continue matching, set neg_tzoffset flag */
#define DUK__CF_ACCEPT       (1 << 1)  /* accept string */
#define DUK__CF_ACCEPT_NUL   (1 << 2)  /* accept string if next char is NUL (otherwise reject) */

#define DUK__PACK_RULE(partmask,sepmask,nextpart,flags)  \
        ((duk_uint32_t) (partmask) + \
         (((duk_uint32_t) (sepmask)) << 9) + \
         (((duk_uint32_t) (nextpart)) << 17) + \
         (((duk_uint32_t) (flags)) << 21))

#define DUK__UNPACK_RULE(rule,var_nextidx,var_flags)  do { \
                (var_nextidx) = (duk_small_uint_t) (((rule) >> 17) & 0x0f); \
                (var_flags) = (duk_small_uint_t) ((rule) >> 21); \
        } while (0)

#define DUK__RULE_MASK_PART_SEP  0x1ffffUL

/* Matching separator index is used in the control table */
DUK_LOCAL const duk_uint8_t duk__parse_iso8601_seps[] = {
        DUK_ASC_PLUS /*0*/, DUK_ASC_MINUS /*1*/, DUK_ASC_UC_T /*2*/, DUK_ASC_SPACE /*3*/,
        DUK_ASC_COLON /*4*/, DUK_ASC_PERIOD /*5*/, DUK_ASC_UC_Z /*6*/, DUK_ASC_NUL /*7*/
};

/* Rule table: first matching rule is used to determine what to do next. */
DUK_LOCAL const duk_uint32_t duk__parse_iso8601_control[] = {
        DUK__PACK_RULE(DUK__PM_YEAR, DUK__SM_MINUS, DUK__PI_MONTH, 0),
        DUK__PACK_RULE(DUK__PM_MONTH, DUK__SM_MINUS, DUK__PI_DAY, 0),
        DUK__PACK_RULE(DUK__PM_YEAR | DUK__PM_MONTH | DUK__PM_DAY, DUK__SM_T | DUK__SM_SPACE, DUK__PI_HOUR, 0),
        DUK__PACK_RULE(DUK__PM_HOUR, DUK__SM_COLON, DUK__PI_MINUTE, 0),
        DUK__PACK_RULE(DUK__PM_MINUTE, DUK__SM_COLON, DUK__PI_SECOND, 0),
        DUK__PACK_RULE(DUK__PM_SECOND, DUK__SM_PERIOD, DUK__PI_MILLISECOND, 0),
        DUK__PACK_RULE(DUK__PM_TZHOUR, DUK__SM_COLON, DUK__PI_TZMINUTE, 0),
        DUK__PACK_RULE(DUK__PM_YEAR | DUK__PM_MONTH | DUK__PM_DAY | DUK__PM_HOUR /*Note1*/ | DUK__PM_MINUTE | DUK__PM_SECOND | DUK__PM_MILLISECOND, DUK__SM_PLUS, DUK__PI_TZHOUR, 0),
        DUK__PACK_RULE(DUK__PM_YEAR | DUK__PM_MONTH | DUK__PM_DAY | DUK__PM_HOUR /*Note1*/ | DUK__PM_MINUTE | DUK__PM_SECOND | DUK__PM_MILLISECOND, DUK__SM_MINUS, DUK__PI_TZHOUR, DUK__CF_NEG),
        DUK__PACK_RULE(DUK__PM_YEAR | DUK__PM_MONTH | DUK__PM_DAY | DUK__PM_HOUR /*Note1*/ | DUK__PM_MINUTE | DUK__PM_SECOND | DUK__PM_MILLISECOND, DUK__SM_Z, 0, DUK__CF_ACCEPT_NUL),
        DUK__PACK_RULE(DUK__PM_YEAR | DUK__PM_MONTH | DUK__PM_DAY | DUK__PM_HOUR /*Note1*/ | DUK__PM_MINUTE | DUK__PM_SECOND | DUK__PM_MILLISECOND | DUK__PM_TZHOUR /*Note2*/ | DUK__PM_TZMINUTE, DUK__SM_NUL, 0, DUK__CF_ACCEPT)

        /* Note1: the specification doesn't require matching a time form with
         *        just hours ("HH"), but we accept it here, e.g. "2012-01-02T12Z".
         *
         * Note2: the specification doesn't require matching a timezone offset
         *        with just hours ("HH"), but accept it here, e.g. "2012-01-02T03:04:05+02"
         */
};

DUK_LOCAL duk_bool_t duk__parse_string_iso8601_subset(duk_context *ctx, const char *str) {
        duk_int_t parts[DUK__NUM_ISO8601_PARSER_PARTS];
        duk_double_t dparts[DUK_DATE_IDX_NUM_PARTS];
        duk_double_t d;
        const duk_uint8_t *p;
        duk_small_uint_t part_idx = 0;
        duk_int_t accum = 0;
        duk_small_uint_t ndigits = 0;
        duk_bool_t neg_year = 0;
        duk_bool_t neg_tzoffset = 0;
        duk_uint_fast8_t ch;
        duk_small_uint_t i;

        /* During parsing, month and day are one-based; set defaults here. */
        DUK_MEMZERO(parts, sizeof(parts));
        DUK_ASSERT(parts[DUK_DATE_IDX_YEAR] == 0);  /* don't care value, year is mandatory */
        parts[DUK_DATE_IDX_MONTH] = 1;
        parts[DUK_DATE_IDX_DAY] = 1;

        /* Special handling for year sign. */
        p = (const duk_uint8_t *) str;
        ch = p[0];
        if (ch == DUK_ASC_PLUS) {
                p++;
        } else if (ch == DUK_ASC_MINUS) {
                neg_year = 1;
                p++;
        }

        for (;;) {
                ch = *p++;
                DUK_DDD(DUK_DDDPRINT("parsing, part_idx=%ld, char=%ld ('%c')",
                                     (long) part_idx, (long) ch,
                                     (int) ((ch >= 0x20 && ch <= 0x7e) ? ch : DUK_ASC_QUESTION)));

                if (ch >= DUK_ASC_0 && ch <= DUK_ASC_9) {
                        if (ndigits >= 9) {
                                DUK_DDD(DUK_DDDPRINT("too many digits -> reject"));
                                goto reject;
                        }
                        if (part_idx == DUK__PI_MILLISECOND /*msec*/ && ndigits >= 3) {
                                /* ignore millisecond fractions after 3 */
                        } else {
                                accum = accum * 10 + ((duk_int_t) ch) - ((duk_int_t) DUK_ASC_0) + 0x00;
                                ndigits++;
                        }
                } else {
                        duk_uint_fast32_t match_val;
                        duk_small_int_t sep_idx;

                        if (ndigits <= 0) {
                                goto reject;
                        }
                        if (part_idx == DUK__PI_MILLISECOND) {
                                /* complete the millisecond field */
                                while (ndigits < 3) {
                                        accum *= 10;
                                        ndigits++;
                                }
                        }
                        parts[part_idx] = accum;
                        DUK_DDD(DUK_DDDPRINT("wrote part %ld -> value %ld", (long) part_idx, (long) accum));

                        accum = 0;
                        ndigits = 0;

                        for (i = 0; i < (duk_small_uint_t) (sizeof(duk__parse_iso8601_seps) / sizeof(duk_uint8_t)); i++) {
                                if (duk__parse_iso8601_seps[i] == ch) {
                                        break;
                                }
                        }
                        if (i == (duk_small_uint_t) (sizeof(duk__parse_iso8601_seps) / sizeof(duk_uint8_t))) {
                                DUK_DDD(DUK_DDDPRINT("separator character doesn't match -> reject"));
                                goto reject;
                        }

                        sep_idx = i;
                        match_val = (1UL << part_idx) + (1UL << (sep_idx + 9));  /* match against rule part/sep bits */

                        for (i = 0; i < (duk_small_uint_t) (sizeof(duk__parse_iso8601_control) / sizeof(duk_uint32_t)); i++) {
                                duk_uint_fast32_t rule = duk__parse_iso8601_control[i];
                                duk_small_uint_t nextpart;
                                duk_small_uint_t cflags;

                                DUK_DDD(DUK_DDDPRINT("part_idx=%ld, sep_idx=%ld, match_val=0x%08lx, considering rule=0x%08lx",
                                                     (long) part_idx, (long) sep_idx,
                                                     (unsigned long) match_val, (unsigned long) rule));

                                if ((rule & match_val) != match_val) {
                                        continue;
                                }

                                DUK__UNPACK_RULE(rule, nextpart, cflags);

                                DUK_DDD(DUK_DDDPRINT("rule match -> part_idx=%ld, sep_idx=%ld, match_val=0x%08lx, "
                                                     "rule=0x%08lx -> nextpart=%ld, cflags=0x%02lx",
                                                     (long) part_idx, (long) sep_idx,
                                                     (unsigned long) match_val, (unsigned long) rule,
                                                     (long) nextpart, (unsigned long) cflags));

                                if (cflags & DUK__CF_NEG) {
                                        neg_tzoffset = 1;
                                }

                                if (cflags & DUK__CF_ACCEPT) {
                                        goto accept;
                                }

                                if (cflags & DUK__CF_ACCEPT_NUL) {
                                        DUK_ASSERT(*(p - 1) != (char) 0);
                                        if (*p == DUK_ASC_NUL) {
                                                goto accept;
                                        }
                                        goto reject;
                                }

                                part_idx = nextpart;
                                break;
                        }  /* rule match */

                        if (i == (duk_small_uint_t) (sizeof(duk__parse_iso8601_control) / sizeof(duk_uint32_t))) {
                                DUK_DDD(DUK_DDDPRINT("no rule matches -> reject"));
                                goto reject;
                        }

                        if (ch == 0) {
                                /* This shouldn't be necessary, but check just in case
                                 * to avoid any chance of overruns.
                                 */
                                DUK_DDD(DUK_DDDPRINT("NUL after rule matching (should not happen) -> reject"));
                                goto reject;
                        }
                }  /* if-digit-else-ctrl */
        }  /* char loop */

        /* We should never exit the loop above. */
        DUK_UNREACHABLE();

 reject:
        DUK_DDD(DUK_DDDPRINT("reject"));
        return 0;

 accept:
        DUK_DDD(DUK_DDDPRINT("accept"));

        /* Apply timezone offset to get the main parts in UTC */
        if (neg_year) {
                parts[DUK__PI_YEAR] = -parts[DUK__PI_YEAR];
        }
        if (neg_tzoffset) {
                parts[DUK__PI_HOUR] += parts[DUK__PI_TZHOUR];
                parts[DUK__PI_MINUTE] += parts[DUK__PI_TZMINUTE];
        } else {
                parts[DUK__PI_HOUR] -= parts[DUK__PI_TZHOUR];
                parts[DUK__PI_MINUTE] -= parts[DUK__PI_TZMINUTE];
        }
        parts[DUK__PI_MONTH] -= 1;  /* zero-based month */
        parts[DUK__PI_DAY] -= 1;  /* zero-based day */

        /* Use double parts, they tolerate unnormalized time.
         *
         * Note: DUK_DATE_IDX_WEEKDAY is initialized with a bogus value (DUK__PI_TZHOUR)
         * on purpose.  It won't be actually used by duk_bi_date_get_timeval_from_dparts(),
         * but will make the value initialized just in case, and avoid any
         * potential for Valgrind issues.
         */
        for (i = 0; i < DUK_DATE_IDX_NUM_PARTS; i++) {
                DUK_DDD(DUK_DDDPRINT("part[%ld] = %ld", (long) i, (long) parts[i]));
                dparts[i] = parts[i];
        }

        d = duk_bi_date_get_timeval_from_dparts(dparts, 0 /*flags*/);
        duk_push_number(ctx, d);
        return 1;
}

/*
 *  Date/time parsing helper.
 *
 *  Parse a datetime string into a time value.  We must first try to parse
 *  the input according to the standard format in E5.1 Section 15.9.1.15.
 *  If that fails, we can try to parse using custom parsing, which can
 *  either be platform neutral (custom code) or platform specific (using
 *  existing platform API calls).
 *
 *  Note in particular that we must parse whatever toString(), toUTCString(),
 *  and toISOString() can produce; see E5.1 Section 15.9.4.2.
 *
 *  Returns 1 to allow tail calling.
 *
 *  There is much room for improvement here with respect to supporting
 *  alternative datetime formats.  For instance, V8 parses '2012-01-01' as
 *  UTC and '2012/01/01' as local time.
 */

DUK_LOCAL duk_ret_t duk__parse_string(duk_context *ctx, const char *str) {
        /* XXX: there is a small risk here: because the ISO 8601 parser is
         * very loose, it may end up parsing some datetime values which
         * would be better parsed with a platform specific parser.
         */

        DUK_ASSERT(str != NULL);
        DUK_DDD(DUK_DDDPRINT("parse datetime from string '%s'", (const char *) str));

        if (duk__parse_string_iso8601_subset(ctx, str) != 0) {
                return 1;
        }

#if defined(DUK_USE_DATE_PARSE_STRING)
        /* Contract, either:
         * - Push value on stack and return 1
         * - Don't push anything on stack and return 0
         */

        if (DUK_USE_DATE_PARSE_STRING(ctx, str) != 0) {
                return 1;
        }
#else
        /* No platform-specific parsing, this is not an error. */
#endif

        duk_push_nan(ctx);
        return 1;
}

/*
 *  Calendar helpers
 *
 *  Some helpers are used for getters and can operate on normalized values
 *  which can be represented with 32-bit signed integers.  Other helpers are
 *  needed by setters and operate on un-normalized double values, must watch
 *  out for non-finite numbers etc.
 */

DUK_LOCAL duk_uint8_t duk__days_in_month[12] = {
        (duk_uint8_t) 31, (duk_uint8_t) 28, (duk_uint8_t) 31, (duk_uint8_t) 30,
        (duk_uint8_t) 31, (duk_uint8_t) 30, (duk_uint8_t) 31, (duk_uint8_t) 31,
        (duk_uint8_t) 30, (duk_uint8_t) 31, (duk_uint8_t) 30, (duk_uint8_t) 31
};

/* Maximum iteration count for computing UTC-to-local time offset when
 * creating an Ecmascript time value from local parts.
 */
#define DUK__LOCAL_TZOFFSET_MAXITER   4

/* Because 'day since epoch' can be negative and is used to compute weekday
 * using a modulo operation, add this multiple of 7 to avoid negative values
 * when year is below 1970 epoch.  Ecmascript time values are restricted to
 * +/- 100 million days from epoch, so this adder fits nicely into 32 bits.
 * Round to a multiple of 7 (= floor(100000000 / 7) * 7) and add margin.
 */
#define DUK__WEEKDAY_MOD_ADDER  (20000000 * 7)  /* 0x08583b00 */

DUK_INTERNAL duk_bool_t duk_bi_date_is_leap_year(duk_int_t year) {
        if ((year % 4) != 0) {
                return 0;
        }
        if ((year % 100) != 0) {
                return 1;
        }
        if ((year % 400) != 0) {
                return 0;
        }
        return 1;
}

DUK_INTERNAL duk_bool_t duk_bi_date_timeval_in_valid_range(duk_double_t x) {
        return (x >= -DUK_DATE_MSEC_100M_DAYS && x <= DUK_DATE_MSEC_100M_DAYS);
}

DUK_INTERNAL duk_bool_t duk_bi_date_timeval_in_leeway_range(duk_double_t x) {
        return (x >= -DUK_DATE_MSEC_100M_DAYS_LEEWAY && x <= DUK_DATE_MSEC_100M_DAYS_LEEWAY);
}

DUK_INTERNAL duk_bool_t duk_bi_date_year_in_valid_range(duk_double_t x) {
        return (x >= DUK_DATE_MIN_ECMA_YEAR && x <= DUK_DATE_MAX_ECMA_YEAR);
}

DUK_LOCAL duk_double_t duk__timeclip(duk_double_t x) {
        if (!DUK_ISFINITE(x)) {
                return DUK_DOUBLE_NAN;
        }

        if (!duk_bi_date_timeval_in_valid_range(x)) {
                return DUK_DOUBLE_NAN;
        }

        x = duk_js_tointeger_number(x);

        /* Here we'd have the option to normalize -0 to +0. */
        return x;
}

/* Integer division which floors also negative values correctly. */
DUK_LOCAL duk_int_t duk__div_floor(duk_int_t a, duk_int_t b) {
        DUK_ASSERT(b > 0);
        if (a >= 0) {
                return a / b;
        } else {
                /* e.g. a = -4, b = 5  -->  -4 - 5 + 1 / 5  -->  -8 / 5  -->  -1
                 *      a = -5, b = 5  -->  -5 - 5 + 1 / 5  -->  -9 / 5  -->  -1
                 *      a = -6, b = 5  -->  -6 - 5 + 1 / 5  -->  -10 / 5  -->  -2
                 */
                return (a - b + 1) / b;
        }
}

/* Compute day number of the first day of a given year. */
DUK_LOCAL duk_int_t duk__day_from_year(duk_int_t year) {
        /* Note: in integer arithmetic, (x / 4) is same as floor(x / 4) for non-negative
         * values, but is incorrect for negative ones.
         */
        return 365 * (year - 1970)
               + duk__div_floor(year - 1969, 4)
               - duk__div_floor(year - 1901, 100)
               + duk__div_floor(year - 1601, 400);
}

/* Given a day number, determine year and day-within-year. */
DUK_LOCAL duk_int_t duk__year_from_day(duk_int_t day, duk_small_int_t *out_day_within_year) {
        duk_int_t year;
        duk_int_t diff_days;

        /* estimate year upwards (towards positive infinity), then back down;
         * two iterations should be enough
         */

        if (day >= 0) {
                year = 1970 + day / 365;
        } else {
                year = 1970 + day / 366;
        }

        for (;;) {
                diff_days = duk__day_from_year(year) - day;
                DUK_DDD(DUK_DDDPRINT("year=%ld day=%ld, diff_days=%ld", (long) year, (long) day, (long) diff_days));
                if (diff_days <= 0) {
                        DUK_ASSERT(-diff_days < 366);  /* fits into duk_small_int_t */
                        *out_day_within_year = -diff_days;
                        DUK_DDD(DUK_DDDPRINT("--> year=%ld, day-within-year=%ld",
                                             (long) year, (long) *out_day_within_year));
                        DUK_ASSERT(*out_day_within_year >= 0);
                        DUK_ASSERT(*out_day_within_year < (duk_bi_date_is_leap_year(year) ? 366 : 365));
                        return year;
                }

                /* Note: this is very tricky; we must never 'overshoot' the
                 * correction downwards.
                 */
                year -= 1 + (diff_days - 1) / 366;  /* conservative */
        }
}

/* Given a (year, month, day-within-month) triple, compute day number.
 * The input triple is un-normalized and may contain non-finite values.
 */
DUK_LOCAL duk_double_t duk__make_day(duk_double_t year, duk_double_t month, duk_double_t day) {
        duk_int_t day_num;
        duk_bool_t is_leap;
        duk_small_int_t i, n;

        /* Assume that year, month, day are all coerced to whole numbers.
         * They may also be NaN or infinity, in which case this function
         * must return NaN or infinity to ensure time value becomes NaN.
         * If 'day' is NaN, the final return will end up returning a NaN,
         * so it doesn't need to be checked here.
         */

        if (!DUK_ISFINITE(year) || !DUK_ISFINITE(month)) {
                return DUK_DOUBLE_NAN;
        }

        year += DUK_FLOOR(month / 12.0);

        month = DUK_FMOD(month, 12.0);
        if (month < 0.0) {
                /* handle negative values */
                month += 12.0;
        }

        /* The algorithm in E5.1 Section 15.9.1.12 normalizes month, but
         * does not normalize the day-of-month (nor check whether or not
         * it is finite) because it's not necessary for finding the day
         * number which matches the (year,month) pair.
         *
         * We assume that duk__day_from_year() is exact here.
         *
         * Without an explicit infinity / NaN check in the beginning,
         * day_num would be a bogus integer here.
         *
         * It's possible for 'year' to be out of integer range here.
         * If so, we need to return NaN without integer overflow.
         * This fixes test-bug-setyear-overflow.js.
         */

        if (!duk_bi_date_year_in_valid_range(year)) {
                DUK_DD(DUK_DDPRINT("year not in ecmascript valid range, avoid integer overflow: %lf", (double) year));
                return DUK_DOUBLE_NAN;
        }
        day_num = duk__day_from_year((duk_int_t) year);
        is_leap = duk_bi_date_is_leap_year((duk_int_t) year);

        n = (duk_small_int_t) month;
        for (i = 0; i < n; i++) {
                day_num += duk__days_in_month[i];
                if (i == 1 && is_leap) {
                        day_num++;
                }
        }

        /* If 'day' is NaN, returns NaN. */
        return (duk_double_t) day_num + day;
}

/* Split time value into parts.  The time value is assumed to be an internal
 * one, i.e. finite, no fractions.  Possible local time adjustment has already
 * been applied when reading the time value.
 */
DUK_INTERNAL void duk_bi_date_timeval_to_parts(duk_double_t d, duk_int_t *parts, duk_double_t *dparts, duk_small_uint_t flags) {
        duk_double_t d1, d2;
        duk_int_t t1, t2;
        duk_int_t day_since_epoch;
        duk_int_t year;  /* does not fit into 16 bits */
        duk_small_int_t day_in_year;
        duk_small_int_t month;
        duk_small_int_t day;
        duk_small_int_t dim;
        duk_int_t jan1_since_epoch;
        duk_small_int_t jan1_weekday;
        duk_int_t equiv_year;
        duk_small_uint_t i;
        duk_bool_t is_leap;
        duk_small_int_t arridx;

        DUK_ASSERT(DUK_ISFINITE(d));    /* caller checks */
        DUK_ASSERT(DUK_FLOOR(d) == d);  /* no fractions in internal time */

        /* The timevalue must be in valid Ecmascript range, but since a local
         * time offset can be applied, we need to allow a +/- 24h leeway to
         * the value.  In other words, although the UTC time is within the
         * Ecmascript range, the local part values can be just outside of it.
         */
        DUK_UNREF(duk_bi_date_timeval_in_leeway_range);
        DUK_ASSERT(duk_bi_date_timeval_in_leeway_range(d));

        /* these computations are guaranteed to be exact for the valid
         * E5 time value range, assuming milliseconds without fractions.
         */
        d1 = (duk_double_t) DUK_FMOD(d, (double) DUK_DATE_MSEC_DAY);
        if (d1 < 0.0) {
                /* deal with negative values */
                d1 += (duk_double_t) DUK_DATE_MSEC_DAY;
        }
        d2 = DUK_FLOOR((double) (d / (duk_double_t) DUK_DATE_MSEC_DAY));
        DUK_ASSERT(d2 * ((duk_double_t) DUK_DATE_MSEC_DAY) + d1 == d);
        /* now expected to fit into a 32-bit integer */
        t1 = (duk_int_t) d1;
        t2 = (duk_int_t) d2;
        day_since_epoch = t2;
        DUK_ASSERT((duk_double_t) t1 == d1);
        DUK_ASSERT((duk_double_t) t2 == d2);

        /* t1 = milliseconds within day (fits 32 bit)
         * t2 = day number from epoch (fits 32 bit, may be negative)
         */

        parts[DUK_DATE_IDX_MILLISECOND] = t1 % 1000; t1 /= 1000;
        parts[DUK_DATE_IDX_SECOND] = t1 % 60; t1 /= 60;
        parts[DUK_DATE_IDX_MINUTE] = t1 % 60; t1 /= 60;
        parts[DUK_DATE_IDX_HOUR] = t1;
        DUK_ASSERT(parts[DUK_DATE_IDX_MILLISECOND] >= 0 && parts[DUK_DATE_IDX_MILLISECOND] <= 999);
        DUK_ASSERT(parts[DUK_DATE_IDX_SECOND] >= 0 && parts[DUK_DATE_IDX_SECOND] <= 59);
        DUK_ASSERT(parts[DUK_DATE_IDX_MINUTE] >= 0 && parts[DUK_DATE_IDX_MINUTE] <= 59);
        DUK_ASSERT(parts[DUK_DATE_IDX_HOUR] >= 0 && parts[DUK_DATE_IDX_HOUR] <= 23);

        DUK_DDD(DUK_DDDPRINT("d=%lf, d1=%lf, d2=%lf, t1=%ld, t2=%ld, parts: hour=%ld min=%ld sec=%ld msec=%ld",
                             (double) d, (double) d1, (double) d2, (long) t1, (long) t2,
                             (long) parts[DUK_DATE_IDX_HOUR],
                             (long) parts[DUK_DATE_IDX_MINUTE],
                             (long) parts[DUK_DATE_IDX_SECOND],
                             (long) parts[DUK_DATE_IDX_MILLISECOND]));

        /* This assert depends on the input parts representing time inside
         * the Ecmascript range.
         */
        DUK_ASSERT(t2 + DUK__WEEKDAY_MOD_ADDER >= 0);
        parts[DUK_DATE_IDX_WEEKDAY] = (t2 + 4 + DUK__WEEKDAY_MOD_ADDER) % 7;  /* E5.1 Section 15.9.1.6 */
        DUK_ASSERT(parts[DUK_DATE_IDX_WEEKDAY] >= 0 && parts[DUK_DATE_IDX_WEEKDAY] <= 6);

        year = duk__year_from_day(t2, &day_in_year);
        day = day_in_year;
        is_leap = duk_bi_date_is_leap_year(year);
        for (month = 0; month < 12; month++) {
                dim = duk__days_in_month[month];
                if (month == 1 && is_leap) {
                        dim++;
                }
                DUK_DDD(DUK_DDDPRINT("month=%ld, dim=%ld, day=%ld",
                                     (long) month, (long) dim, (long) day));
                if (day < dim) {
                        break;
                }
                day -= dim;
        }
        DUK_DDD(DUK_DDDPRINT("final month=%ld", (long) month));
        DUK_ASSERT(month >= 0 && month <= 11);
        DUK_ASSERT(day >= 0 && day <= 31);

        /* Equivalent year mapping, used to avoid DST trouble when platform
         * may fail to provide reasonable DST answers for dates outside the
         * ordinary range (e.g. 1970-2038).  An equivalent year has the same
         * leap-year-ness as the original year and begins on the same weekday
         * (Jan 1).
         *
         * The year 2038 is avoided because there seem to be problems with it
         * on some platforms.  The year 1970 is also avoided as there were
         * practical problems with it; an equivalent year is used for it too,
         * which breaks some DST computations for 1970 right now, see e.g.
         * test-bi-date-tzoffset-brute-fi.js.
         */
        if ((flags & DUK_DATE_FLAG_EQUIVYEAR) && (year < 1971 || year > 2037)) {
                DUK_ASSERT(is_leap == 0 || is_leap == 1);

                jan1_since_epoch = day_since_epoch - day_in_year;  /* day number for Jan 1 since epoch */
                DUK_ASSERT(jan1_since_epoch + DUK__WEEKDAY_MOD_ADDER >= 0);
                jan1_weekday = (jan1_since_epoch + 4 + DUK__WEEKDAY_MOD_ADDER) % 7;  /* E5.1 Section 15.9.1.6 */
                DUK_ASSERT(jan1_weekday >= 0 && jan1_weekday <= 6);
                arridx = jan1_weekday;
                if (is_leap) {
                        arridx += 7;
                }
                DUK_ASSERT(arridx >= 0 && arridx < (duk_small_int_t) (sizeof(duk__date_equivyear) / sizeof(duk_uint8_t)));

                equiv_year = (duk_int_t) duk__date_equivyear[arridx] + 1970;
                year = equiv_year;
                DUK_DDD(DUK_DDDPRINT("equiv year mapping, year=%ld, day_in_year=%ld, day_since_epoch=%ld, "
                                     "jan1_since_epoch=%ld, jan1_weekday=%ld -> equiv year %ld",
                                     (long) year, (long) day_in_year, (long) day_since_epoch,
                                     (long) jan1_since_epoch, (long) jan1_weekday, (long) equiv_year));
        }

        parts[DUK_DATE_IDX_YEAR] = year;
        parts[DUK_DATE_IDX_MONTH] = month;
        parts[DUK_DATE_IDX_DAY] = day;

        if (flags & DUK_DATE_FLAG_ONEBASED) {
                parts[DUK_DATE_IDX_MONTH]++;  /* zero-based -> one-based */
                parts[DUK_DATE_IDX_DAY]++;    /* -""- */
        }

        if (dparts != NULL) {
                for (i = 0; i < DUK_DATE_IDX_NUM_PARTS; i++) {
                        dparts[i] = (duk_double_t) parts[i];
                }
        }
}

/* Compute time value from (double) parts.  The parts can be either UTC
 * or local time; if local, they need to be (conceptually) converted into
 * UTC time.  The parts may represent valid or invalid time, and may be
 * wildly out of range (but may cancel each other and still come out in
 * the valid Date range).
 */
DUK_INTERNAL duk_double_t duk_bi_date_get_timeval_from_dparts(duk_double_t *dparts, duk_small_uint_t flags) {
#if defined(DUK_USE_PARANOID_DATE_COMPUTATION)
        /* See comments below on MakeTime why these are volatile. */
        volatile duk_double_t tmp_time;
        volatile duk_double_t tmp_day;
        volatile duk_double_t d;
#else
        duk_double_t tmp_time;
        duk_double_t tmp_day;
        duk_double_t d;
#endif
        duk_small_uint_t i;
        duk_int_t tzoff, tzoffprev1, tzoffprev2;

        /* Expects 'this' at top of stack on entry. */

        /* Coerce all finite parts with ToInteger().  ToInteger() must not
         * be called for NaN/Infinity because it will convert e.g. NaN to
         * zero.  If ToInteger() has already been called, this has no side
         * effects and is idempotent.
         *
         * Don't read dparts[DUK_DATE_IDX_WEEKDAY]; it will cause Valgrind
         * issues if the value is uninitialized.
         */
        for (i = 0; i <= DUK_DATE_IDX_MILLISECOND; i++) {
                /* SCANBUILD: scan-build complains here about assigned value
                 * being garbage or undefined.  This is correct but operating
                 * on undefined values has no ill effect and is ignored by the
                 * caller in the case where this happens.
                 */
                d = dparts[i];
                if (DUK_ISFINITE(d)) {
                        dparts[i] = duk_js_tointeger_number(d);
                }
        }

        /* Use explicit steps in computation to try to ensure that
         * computation happens with intermediate results coerced to
         * double values (instead of using something more accurate).
         * E.g. E5.1 Section 15.9.1.11 requires use of IEEE 754
         * rules (= Ecmascript '+' and '*' operators).
         *
         * Without 'volatile' even this approach fails on some platform
         * and compiler combinations.  For instance, gcc 4.8.1 on Ubuntu
         * 64-bit, with -m32 and without -std=c99, test-bi-date-canceling.js
         * would fail because of some optimizations when computing tmp_time
         * (MakeTime below).  Adding 'volatile' to tmp_time solved this
         * particular problem (annoyingly, also adding debug prints or
         * running the executable under valgrind hides it).
         */

        /* MakeTime */
        tmp_time = 0.0;
        tmp_time += dparts[DUK_DATE_IDX_HOUR] * ((duk_double_t) DUK_DATE_MSEC_HOUR);
        tmp_time += dparts[DUK_DATE_IDX_MINUTE] * ((duk_double_t) DUK_DATE_MSEC_MINUTE);
        tmp_time += dparts[DUK_DATE_IDX_SECOND] * ((duk_double_t) DUK_DATE_MSEC_SECOND);
        tmp_time += dparts[DUK_DATE_IDX_MILLISECOND];

        /* MakeDay */
        tmp_day = duk__make_day(dparts[DUK_DATE_IDX_YEAR], dparts[DUK_DATE_IDX_MONTH], dparts[DUK_DATE_IDX_DAY]);

        /* MakeDate */
        d = tmp_day * ((duk_double_t) DUK_DATE_MSEC_DAY) + tmp_time;

        DUK_DDD(DUK_DDDPRINT("time=%lf day=%lf --> timeval=%lf",
                             (double) tmp_time, (double) tmp_day, (double) d));

        /* Optional UTC conversion. */
        if (flags & DUK_DATE_FLAG_LOCALTIME) {
                /* DUK_USE_DATE_GET_LOCAL_TZOFFSET() needs to be called with a
                 * time value computed from UTC parts.  At this point we only
                 * have 'd' which is a time value computed from local parts, so
                 * it is off by the UTC-to-local time offset which we don't know
                 * yet.  The current solution for computing the UTC-to-local
                 * time offset is to iterate a few times and detect a fixed
                 * point or a two-cycle loop (or a sanity iteration limit),
                 * see test-bi-date-local-parts.js and test-bi-date-tzoffset-basic-fi.js.
                 *
                 * E5.1 Section 15.9.1.9:
                 * UTC(t) = t - LocalTZA - DaylightSavingTA(t - LocalTZA)
                 *
                 * For NaN/inf, DUK_USE_DATE_GET_LOCAL_TZOFFSET() returns 0.
                 */

#if 0
                /* Old solution: don't iterate, incorrect */
                tzoff = DUK_USE_DATE_GET_LOCAL_TZOFFSET(d);
                DUK_DDD(DUK_DDDPRINT("tzoffset w/o iteration, tzoff=%ld", (long) tzoff));
                d -= tzoff * 1000L;
                DUK_UNREF(tzoffprev1);
                DUK_UNREF(tzoffprev2);
#endif

                /* Iteration solution */
                tzoff = 0;
                tzoffprev1 = 999999999L;  /* invalid value which never matches */
                for (i = 0; i < DUK__LOCAL_TZOFFSET_MAXITER; i++) {
                        tzoffprev2 = tzoffprev1;
                        tzoffprev1 = tzoff;
                        tzoff = DUK_USE_DATE_GET_LOCAL_TZOFFSET(d - tzoff * 1000L);
                        DUK_DDD(DUK_DDDPRINT("tzoffset iteration, i=%d, tzoff=%ld, tzoffprev1=%ld tzoffprev2=%ld",
                                             (int) i, (long) tzoff, (long) tzoffprev1, (long) tzoffprev2));
                        if (tzoff == tzoffprev1) {
                                DUK_DDD(DUK_DDDPRINT("tzoffset iteration finished, i=%d, tzoff=%ld, tzoffprev1=%ld, tzoffprev2=%ld",
                                                     (int) i, (long) tzoff, (long) tzoffprev1, (long) tzoffprev2));
                                break;
                        } else if (tzoff == tzoffprev2) {
                                /* Two value cycle, see e.g. test-bi-date-tzoffset-basic-fi.js.
                                 * In these cases, favor a higher tzoffset to get a consistent
                                 * result which is independent of iteration count.  Not sure if
                                 * this is a generically correct solution.
                                 */
                                DUK_DDD(DUK_DDDPRINT("tzoffset iteration two-value cycle, i=%d, tzoff=%ld, tzoffprev1=%ld, tzoffprev2=%ld",
                                                     (int) i, (long) tzoff, (long) tzoffprev1, (long) tzoffprev2));
                                if (tzoffprev1 > tzoff) {
                                        tzoff = tzoffprev1;
                                }
                                break;
                        }
                }
                DUK_DDD(DUK_DDDPRINT("tzoffset iteration, tzoff=%ld", (long) tzoff));
                d -= tzoff * 1000L;
        }

        /* TimeClip(), which also handles Infinity -> NaN conversion */
        d = duk__timeclip(d);

        return d;
}

/*
 *  API oriented helpers
 */

/* Push 'this' binding, check that it is a Date object; then push the
 * internal time value.  At the end, stack is: [ ... this timeval ].
 * Returns the time value.  Local time adjustment is done if requested.
 */
DUK_LOCAL duk_double_t duk__push_this_get_timeval_tzoffset(duk_context *ctx, duk_small_uint_t flags, duk_int_t *out_tzoffset) {
        duk_hthread *thr = (duk_hthread *) ctx;
        duk_hobject *h;
        duk_double_t d;
        duk_int_t tzoffset = 0;

        duk_push_this(ctx);
        h = duk_get_hobject(ctx, -1);  /* XXX: getter with class check, useful in built-ins */
        if (h == NULL || DUK_HOBJECT_GET_CLASS_NUMBER(h) != DUK_HOBJECT_CLASS_DATE) {
                DUK_ERROR_TYPE(thr, "expected Date");
        }

        duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_VALUE);
        d = duk_to_number(ctx, -1);
        duk_pop(ctx);

        if (DUK_ISNAN(d)) {
                if (flags & DUK_DATE_FLAG_NAN_TO_ZERO) {
                        d = 0.0;
                }
                if (flags & DUK_DATE_FLAG_NAN_TO_RANGE_ERROR) {
                        DUK_ERROR_RANGE(thr, "Invalid Date");
                }
        }
        /* if no NaN handling flag, may still be NaN here, but not Inf */
        DUK_ASSERT(!DUK_ISINF(d));

        if (flags & DUK_DATE_FLAG_LOCALTIME) {
                /* Note: DST adjustment is determined using UTC time.
                 * If 'd' is NaN, tzoffset will be 0.
                 */
                tzoffset = DUK_USE_DATE_GET_LOCAL_TZOFFSET(d);  /* seconds */
                d += tzoffset * 1000L;
        }
        if (out_tzoffset) {
                *out_tzoffset = tzoffset;
        }

        /* [ ... this ] */
        return d;
}

DUK_LOCAL duk_double_t duk__push_this_get_timeval(duk_context *ctx, duk_small_uint_t flags) {
        return duk__push_this_get_timeval_tzoffset(ctx, flags, NULL);
}

/* Set timeval to 'this' from dparts, push the new time value onto the
 * value stack and return 1 (caller can then tail call us).  Expects
 * the value stack to contain 'this' on the stack top.
 */
DUK_LOCAL duk_ret_t duk__set_this_timeval_from_dparts(duk_context *ctx, duk_double_t *dparts, duk_small_uint_t flags) {
        duk_double_t d;

        /* [ ... this ] */

        d = duk_bi_date_get_timeval_from_dparts(dparts, flags);
        duk_push_number(ctx, d);  /* -> [ ... this timeval_new ] */
        duk_dup_top(ctx);         /* -> [ ... this timeval_new timeval_new ] */
        duk_put_prop_stridx(ctx, -3, DUK_STRIDX_INT_VALUE);

        /* stack top: new time value, return 1 to allow tail calls */
        return 1;
}

/* 'out_buf' must be at least DUK_BI_DATE_ISO8601_BUFSIZE long. */
DUK_LOCAL void duk__format_parts_iso8601(duk_int_t *parts, duk_int_t tzoffset, duk_small_uint_t flags, duk_uint8_t *out_buf) {
        char yearstr[8];   /* "-123456\0" */
        char tzstr[8];     /* "+11:22\0" */
        char sep = (flags & DUK_DATE_FLAG_SEP_T) ? DUK_ASC_UC_T : DUK_ASC_SPACE;

        DUK_ASSERT(parts[DUK_DATE_IDX_MONTH] >= 1 && parts[DUK_DATE_IDX_MONTH] <= 12);
        DUK_ASSERT(parts[DUK_DATE_IDX_DAY] >= 1 && parts[DUK_DATE_IDX_DAY] <= 31);
        DUK_ASSERT(parts[DUK_DATE_IDX_YEAR] >= -999999 && parts[DUK_DATE_IDX_YEAR] <= 999999);

        /* Note: %06d for positive value, %07d for negative value to include
         * sign and 6 digits.
         */
        DUK_SNPRINTF(yearstr,
                     sizeof(yearstr),
                     (parts[DUK_DATE_IDX_YEAR] >= 0 && parts[DUK_DATE_IDX_YEAR] <= 9999) ? "%04ld" :
                            ((parts[DUK_DATE_IDX_YEAR] >= 0) ? "+%06ld" : "%07ld"),
                     (long) parts[DUK_DATE_IDX_YEAR]);
        yearstr[sizeof(yearstr) - 1] = (char) 0;

        if (flags & DUK_DATE_FLAG_LOCALTIME) {
                /* tzoffset seconds are dropped; 16 bits suffice for
                 * time offset in minutes
                 */
                if (tzoffset >= 0) {
                        duk_small_int_t tmp = tzoffset / 60;
                        DUK_SNPRINTF(tzstr, sizeof(tzstr), "+%02d:%02d", (int) (tmp / 60), (int) (tmp % 60));
                } else {
                        duk_small_int_t tmp = -tzoffset / 60;
                        DUK_SNPRINTF(tzstr, sizeof(tzstr), "-%02d:%02d", (int) (tmp / 60), (int) (tmp % 60));
                }
                tzstr[sizeof(tzstr) - 1] = (char) 0;
        } else {
                tzstr[0] = DUK_ASC_UC_Z;
                tzstr[1] = (char) 0;
        }

        /* Unlike year, the other parts fit into 16 bits so %d format
         * is portable.
         */
        if ((flags & DUK_DATE_FLAG_TOSTRING_DATE) && (flags & DUK_DATE_FLAG_TOSTRING_TIME)) {
                DUK_SPRINTF((char *) out_buf, "%s-%02d-%02d%c%02d:%02d:%02d.%03d%s",
                            (const char *) yearstr, (int) parts[DUK_DATE_IDX_MONTH], (int) parts[DUK_DATE_IDX_DAY], (int) sep,
                            (int) parts[DUK_DATE_IDX_HOUR], (int) parts[DUK_DATE_IDX_MINUTE],
                            (int) parts[DUK_DATE_IDX_SECOND], (int) parts[DUK_DATE_IDX_MILLISECOND], (const char *) tzstr);
        } else if (flags & DUK_DATE_FLAG_TOSTRING_DATE) {
                DUK_SPRINTF((char *) out_buf, "%s-%02d-%02d",
                            (const char *) yearstr, (int) parts[DUK_DATE_IDX_MONTH], (int) parts[DUK_DATE_IDX_DAY]);
        } else {
                DUK_ASSERT(flags & DUK_DATE_FLAG_TOSTRING_TIME);
                DUK_SPRINTF((char *) out_buf, "%02d:%02d:%02d.%03d%s",
                            (int) parts[DUK_DATE_IDX_HOUR], (int) parts[DUK_DATE_IDX_MINUTE],
                            (int) parts[DUK_DATE_IDX_SECOND], (int) parts[DUK_DATE_IDX_MILLISECOND],
                            (const char *) tzstr);
        }
}

/* Helper for string conversion calls: check 'this' binding, get the
 * internal time value, and format date and/or time in a few formats.
 * Return value allows tail calls.
 */
DUK_LOCAL duk_ret_t duk__to_string_helper(duk_context *ctx, duk_small_uint_t flags) {
        duk_double_t d;
        duk_int_t parts[DUK_DATE_IDX_NUM_PARTS];
        duk_int_t tzoffset;  /* seconds, doesn't fit into 16 bits */
        duk_bool_t rc;
        duk_uint8_t buf[DUK_BI_DATE_ISO8601_BUFSIZE];

        DUK_UNREF(rc);  /* unreferenced with some options */

        d = duk__push_this_get_timeval_tzoffset(ctx, flags, &tzoffset);
        if (DUK_ISNAN(d)) {
                duk_push_hstring_stridx(ctx, DUK_STRIDX_INVALID_DATE);
                return 1;
        }
        DUK_ASSERT(DUK_ISFINITE(d));

        /* formatters always get one-based month/day-of-month */
        duk_bi_date_timeval_to_parts(d, parts, NULL, DUK_DATE_FLAG_ONEBASED);
        DUK_ASSERT(parts[DUK_DATE_IDX_MONTH] >= 1 && parts[DUK_DATE_IDX_MONTH] <= 12);
        DUK_ASSERT(parts[DUK_DATE_IDX_DAY] >= 1 && parts[DUK_DATE_IDX_DAY] <= 31);

        if (flags & DUK_DATE_FLAG_TOSTRING_LOCALE) {
                /* try locale specific formatter; if it refuses to format the
                 * string, fall back to an ISO 8601 formatted value in local
                 * time.
                 */
#if defined(DUK_USE_DATE_FORMAT_STRING)
                /* Contract, either:
                 * - Push string to value stack and return 1
                 * - Don't push anything and return 0
                 */

                rc = DUK_USE_DATE_FORMAT_STRING(ctx, parts, tzoffset, flags);
                if (rc != 0) {
                        return 1;
                }
#else
                /* No locale specific formatter; this is OK, we fall back
                 * to ISO 8601.
                 */
#endif
        }

        /* Different calling convention than above used because the helper
         * is shared.
         */
        duk__format_parts_iso8601(parts, tzoffset, flags, buf);
        duk_push_string(ctx, (const char *) buf);
        return 1;
}

/* Helper for component getter calls: check 'this' binding, get the
 * internal time value, split it into parts (either as UTC time or
 * local time), push a specified component as a return value to the
 * value stack and return 1 (caller can then tail call us).
 */
DUK_LOCAL duk_ret_t duk__get_part_helper(duk_context *ctx, duk_small_uint_t flags_and_idx) {
        duk_double_t d;
        duk_int_t parts[DUK_DATE_IDX_NUM_PARTS];
        duk_small_uint_t idx_part = (duk_small_uint_t) (flags_and_idx >> DUK_DATE_FLAG_VALUE_SHIFT);  /* unpack args */

        DUK_ASSERT_DISABLE(idx_part >= 0);  /* unsigned */
        DUK_ASSERT(idx_part < DUK_DATE_IDX_NUM_PARTS);

        d = duk__push_this_get_timeval(ctx, flags_and_idx);
        if (DUK_ISNAN(d)) {
                duk_push_nan(ctx);
                return 1;
        }
        DUK_ASSERT(DUK_ISFINITE(d));

        duk_bi_date_timeval_to_parts(d, parts, NULL, flags_and_idx);  /* no need to mask idx portion */

        /* Setter APIs detect special year numbers (0...99) and apply a +1900
         * only in certain cases.  The legacy getYear() getter applies -1900
         * unconditionally.
         */
        duk_push_int(ctx, (flags_and_idx & DUK_DATE_FLAG_SUB1900) ? parts[idx_part] - 1900 : parts[idx_part]);
        return 1;
}

/* Helper for component setter calls: check 'this' binding, get the
 * internal time value, split it into parts (either as UTC time or
 * local time), modify one or more components as specified, recompute
 * the time value, set it as the internal value.  Finally, push the
 * new time value as a return value to the value stack and return 1
 * (caller can then tail call us).
 */
DUK_LOCAL duk_ret_t duk__set_part_helper(duk_context *ctx, duk_small_uint_t flags_and_maxnargs) {
        duk_double_t d;
        duk_int_t parts[DUK_DATE_IDX_NUM_PARTS];
        duk_double_t dparts[DUK_DATE_IDX_NUM_PARTS];
        duk_idx_t nargs;
        duk_small_uint_t maxnargs = (duk_small_uint_t) (flags_and_maxnargs >> DUK_DATE_FLAG_VALUE_SHIFT);  /* unpack args */
        duk_small_uint_t idx_first, idx;
        duk_small_uint_t i;

        nargs = duk_get_top(ctx);
        d = duk__push_this_get_timeval(ctx, flags_and_maxnargs);
        DUK_ASSERT(DUK_ISFINITE(d) || DUK_ISNAN(d));

        if (DUK_ISFINITE(d)) {
                duk_bi_date_timeval_to_parts(d, parts, dparts, flags_and_maxnargs);
        } else {
                /* NaN timevalue: we need to coerce the arguments, but
                 * the resulting internal timestamp needs to remain NaN.
                 * This works but is not pretty: parts and dparts will
                 * be partially uninitialized, but we only write to them.
                 */
        }

        /*
         *  Determining which datetime components to overwrite based on
         *  stack arguments is a bit complicated, but important to factor
         *  out from setters themselves for compactness.
         *
         *  If DUK_DATE_FLAG_TIMESETTER, maxnargs indicates setter type:
         *
         *   1 -> millisecond
         *   2 -> second, [millisecond]
         *   3 -> minute, [second], [millisecond]
         *   4 -> hour, [minute], [second], [millisecond]
         *
         *  Else:
         *
         *   1 -> date
         *   2 -> month, [date]
         *   3 -> year, [month], [date]
         *
         *  By comparing nargs and maxnargs (and flags) we know which
         *  components to override.  We rely on part index ordering.
         */

        if (flags_and_maxnargs & DUK_DATE_FLAG_TIMESETTER) {
                DUK_ASSERT(maxnargs >= 1 && maxnargs <= 4);
                idx_first = DUK_DATE_IDX_MILLISECOND - (maxnargs - 1);
        } else {
                DUK_ASSERT(maxnargs >= 1 && maxnargs <= 3);
                idx_first = DUK_DATE_IDX_DAY - (maxnargs - 1);
        }
        DUK_ASSERT_DISABLE(idx_first >= 0);  /* unsigned */
        DUK_ASSERT(idx_first < DUK_DATE_IDX_NUM_PARTS);

        for (i = 0; i < maxnargs; i++) {
                if ((duk_idx_t) i >= nargs) {
                        /* no argument given -> leave components untouched */
                        break;
                }
                idx = idx_first + i;
                DUK_ASSERT_DISABLE(idx >= 0);  /* unsigned */
                DUK_ASSERT(idx < DUK_DATE_IDX_NUM_PARTS);

                if (idx == DUK_DATE_IDX_YEAR && (flags_and_maxnargs & DUK_DATE_FLAG_YEAR_FIXUP)) {
                        duk__twodigit_year_fixup(ctx, (duk_idx_t) i);
                }

                dparts[idx] = duk_to_number(ctx, i);

                if (idx == DUK_DATE_IDX_DAY) {
                        /* Day-of-month is one-based in the API, but zero-based
                         * internally, so fix here.  Note that month is zero-based
                         * both in the API and internally.
                         */
                        /* SCANBUILD: complains about use of uninitialized values.
                         * The complaint is correct, but operating in undefined
                         * values here is intentional in some cases and the caller
                         * ignores the results.
                         */
                        dparts[idx] -= 1.0;
                }
        }

        /* Leaves new timevalue on stack top and returns 1, which is correct
         * for part setters.
         */
        if (DUK_ISFINITE(d)) {
                return duk__set_this_timeval_from_dparts(ctx, dparts, flags_and_maxnargs);
        } else {
                /* Internal timevalue is already NaN, so don't touch it. */
                duk_push_nan(ctx);
                return 1;
        }
}

/* Apply ToNumber() to specified index; if ToInteger(val) in [0,99], add
 * 1900 and replace value at idx_val.
 */
DUK_LOCAL void duk__twodigit_year_fixup(duk_context *ctx, duk_idx_t idx_val) {
        duk_double_t d;

        /* XXX: idx_val would fit into 16 bits, but using duk_small_uint_t
         * might not generate better code due to casting.
         */

        /* E5 Sections 15.9.3.1, B.2.4, B.2.5 */
        duk_to_number(ctx, idx_val);
        if (duk_is_nan(ctx, idx_val)) {
                return;
        }
        duk_dup(ctx, idx_val);
        duk_to_int(ctx, -1);
        d = duk_get_number(ctx, -1);  /* get as double to handle huge numbers correctly */
        if (d >= 0.0 && d <= 99.0) {
                d += 1900.0;
                duk_push_number(ctx, d);
                duk_replace(ctx, idx_val);
        }
        duk_pop(ctx);
}

/* Set datetime parts from stack arguments, defaulting any missing values.
 * Day-of-week is not set; it is not required when setting the time value.
 */
DUK_LOCAL void duk__set_parts_from_args(duk_context *ctx, duk_double_t *dparts, duk_idx_t nargs) {
        duk_double_t d;
        duk_small_uint_t i;
        duk_small_uint_t idx;

        /* Causes a ToNumber() coercion, but doesn't break coercion order since
         * year is coerced first anyway.
         */
        duk__twodigit_year_fixup(ctx, 0);

        /* There are at most 7 args, but we use 8 here so that also
         * DUK_DATE_IDX_WEEKDAY gets initialized (to zero) to avoid the potential
         * for any Valgrind gripes later.
         */
        for (i = 0; i < 8; i++) {
                /* Note: rely on index ordering */
                idx = DUK_DATE_IDX_YEAR + i;
                if ((duk_idx_t) i < nargs) {
                        d = duk_to_number(ctx, (duk_idx_t) i);
                        if (idx == DUK_DATE_IDX_DAY) {
                                /* Convert day from one-based to zero-based (internal).  This may
                                 * cause the day part to be negative, which is OK.
                                 */
                                d -= 1.0;
                        }
                } else {
                        /* All components default to 0 except day-of-month which defaults
                         * to 1.  However, because our internal day-of-month is zero-based,
                         * it also defaults to zero here.
                         */
                        d = 0.0;
                }
                dparts[idx] = d;
        }

        DUK_DDD(DUK_DDDPRINT("parts from args -> %lf %lf %lf %lf %lf %lf %lf %lf",
                             (double) dparts[0], (double) dparts[1],
                             (double) dparts[2], (double) dparts[3],
                             (double) dparts[4], (double) dparts[5],
                             (double) dparts[6], (double) dparts[7]));
}

/*
 *  Helper to format a time value into caller buffer, used by logging.
 *  'out_buf' must be at least DUK_BI_DATE_ISO8601_BUFSIZE long.
 */

DUK_INTERNAL void duk_bi_date_format_timeval(duk_double_t timeval, duk_uint8_t *out_buf) {
        duk_int_t parts[DUK_DATE_IDX_NUM_PARTS];

        duk_bi_date_timeval_to_parts(timeval,
                                     parts,
                                     NULL,
                                     DUK_DATE_FLAG_ONEBASED);

        duk__format_parts_iso8601(parts,
                                  0 /*tzoffset*/,
                                  DUK_DATE_FLAG_TOSTRING_DATE |
                                  DUK_DATE_FLAG_TOSTRING_TIME |
                                  DUK_DATE_FLAG_SEP_T /*flags*/,
                                  out_buf);
}

/*
 *  Indirect magic value lookup for Date methods.
 *
 *  Date methods don't put their control flags into the function magic value
 *  because they wouldn't fit into a LIGHTFUNC's magic field.  Instead, the
 *  magic value is set to an index pointing to the array of control flags
 *  below.
 *
 *  This must be kept in strict sync with genbuiltins.py!
 */

static duk_uint16_t duk__date_magics[] = {
        /* 0: toString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_TOSTRING_TIME + DUK_DATE_FLAG_LOCALTIME,

        /* 1: toDateString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_LOCALTIME,

        /* 2: toTimeString */
        DUK_DATE_FLAG_TOSTRING_TIME + DUK_DATE_FLAG_LOCALTIME,

        /* 3: toLocaleString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_TOSTRING_TIME + DUK_DATE_FLAG_TOSTRING_LOCALE + DUK_DATE_FLAG_LOCALTIME,

        /* 4: toLocaleDateString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_TOSTRING_LOCALE + DUK_DATE_FLAG_LOCALTIME,

        /* 5: toLocaleTimeString */
        DUK_DATE_FLAG_TOSTRING_TIME + DUK_DATE_FLAG_TOSTRING_LOCALE + DUK_DATE_FLAG_LOCALTIME,

        /* 6: toUTCString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_TOSTRING_TIME,

        /* 7: toISOString */
        DUK_DATE_FLAG_TOSTRING_DATE + DUK_DATE_FLAG_TOSTRING_TIME + DUK_DATE_FLAG_NAN_TO_RANGE_ERROR + DUK_DATE_FLAG_SEP_T,

        /* 8: getFullYear */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_YEAR << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 9: getUTCFullYear */
        0 + (DUK_DATE_IDX_YEAR << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 10: getMonth */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_MONTH << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 11: getUTCMonth */
        0 + (DUK_DATE_IDX_MONTH << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 12: getDate */
        DUK_DATE_FLAG_ONEBASED + DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_DAY << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 13: getUTCDate */
        DUK_DATE_FLAG_ONEBASED + (DUK_DATE_IDX_DAY << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 14: getDay */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_WEEKDAY << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 15: getUTCDay */
        0 + (DUK_DATE_IDX_WEEKDAY << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 16: getHours */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_HOUR << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 17: getUTCHours */
        0 + (DUK_DATE_IDX_HOUR << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 18: getMinutes */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_MINUTE << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 19: getUTCMinutes */
        0 + (DUK_DATE_IDX_MINUTE << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 20: getSeconds */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_SECOND << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 21: getUTCSeconds */
        0 + (DUK_DATE_IDX_SECOND << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 22: getMilliseconds */
        DUK_DATE_FLAG_LOCALTIME + (DUK_DATE_IDX_MILLISECOND << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 23: getUTCMilliseconds */
        0 + (DUK_DATE_IDX_MILLISECOND << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 24: setMilliseconds */
        DUK_DATE_FLAG_TIMESETTER + DUK_DATE_FLAG_LOCALTIME + (1 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 25: setUTCMilliseconds */
        DUK_DATE_FLAG_TIMESETTER + (1 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 26: setSeconds */
        DUK_DATE_FLAG_TIMESETTER + DUK_DATE_FLAG_LOCALTIME + (2 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 27: setUTCSeconds */
        DUK_DATE_FLAG_TIMESETTER + (2 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 28: setMinutes */
        DUK_DATE_FLAG_TIMESETTER + DUK_DATE_FLAG_LOCALTIME + (3 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 29: setUTCMinutes */
        DUK_DATE_FLAG_TIMESETTER + (3 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 30: setHours */
        DUK_DATE_FLAG_TIMESETTER + DUK_DATE_FLAG_LOCALTIME + (4 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 31: setUTCHours */
        DUK_DATE_FLAG_TIMESETTER + (4 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 32: setDate */
        DUK_DATE_FLAG_LOCALTIME + (1 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 33: setUTCDate */
        0 + (1 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 34: setMonth */
        DUK_DATE_FLAG_LOCALTIME + (2 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 35: setUTCMonth */
        0 + (2 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 36: setFullYear */
        DUK_DATE_FLAG_NAN_TO_ZERO + DUK_DATE_FLAG_LOCALTIME + (3 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 37: setUTCFullYear */
        DUK_DATE_FLAG_NAN_TO_ZERO + (3 << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 38: getYear */
        DUK_DATE_FLAG_LOCALTIME + DUK_DATE_FLAG_SUB1900 + (DUK_DATE_IDX_YEAR << DUK_DATE_FLAG_VALUE_SHIFT),

        /* 39: setYear */
        DUK_DATE_FLAG_NAN_TO_ZERO + DUK_DATE_FLAG_YEAR_FIXUP + (3 << DUK_DATE_FLAG_VALUE_SHIFT),
};

DUK_LOCAL duk_small_uint_t duk__date_get_indirect_magic(duk_context *ctx) {
        duk_small_int_t magicidx = (duk_small_uint_t) duk_get_current_magic(ctx);
        DUK_ASSERT(magicidx >= 0 && magicidx < (duk_small_int_t) (sizeof(duk__date_magics) / sizeof(duk_uint16_t)));
        return (duk_small_uint_t) duk__date_magics[magicidx];
}

/*
 *  Constructor calls
 */

DUK_INTERNAL duk_ret_t duk_bi_date_constructor(duk_context *ctx) {
        duk_idx_t nargs = duk_get_top(ctx);
        duk_bool_t is_cons = duk_is_constructor_call(ctx);
        duk_double_t dparts[DUK_DATE_IDX_NUM_PARTS];
        duk_double_t d;

        DUK_DDD(DUK_DDDPRINT("Date constructor, nargs=%ld, is_cons=%ld", (long) nargs, (long) is_cons));

        duk_push_object_helper(ctx,
                               DUK_HOBJECT_FLAG_EXTENSIBLE |
                               DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_DATE),
                               DUK_BIDX_DATE_PROTOTYPE);

        /* Unlike most built-ins, the internal [[PrimitiveValue]] of a Date
         * is mutable.
         */

        if (nargs == 0 || !is_cons) {
                d = duk__timeclip(DUK_USE_DATE_GET_NOW(ctx));
                duk_push_number(ctx, d);
                duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_INT_VALUE, DUK_PROPDESC_FLAGS_W);
                if (!is_cons) {
                        /* called as a normal function: return new Date().toString() */
                        duk_to_string(ctx, -1);
                }
                return 1;
        } else if (nargs == 1) {
                duk_to_primitive(ctx, 0, DUK_HINT_NONE);
                if (duk_is_string(ctx, 0)) {
                        duk__parse_string(ctx, duk_to_string(ctx, 0));
                        duk_replace(ctx, 0);  /* may be NaN */
                }
                d = duk__timeclip(duk_to_number(ctx, 0));
                duk_push_number(ctx, d);
                duk_xdef_prop_stridx(ctx, -2, DUK_STRIDX_INT_VALUE, DUK_PROPDESC_FLAGS_W);
                return 1;
        }

        duk__set_parts_from_args(ctx, dparts, nargs);

        /* Parts are in local time, convert when setting. */

        (void) duk__set_this_timeval_from_dparts(ctx, dparts, DUK_DATE_FLAG_LOCALTIME /*flags*/);  /* -> [ ... this timeval ] */
        duk_pop(ctx);  /* -> [ ... this ] */
        return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_date_constructor_parse(duk_context *ctx) {
        return duk__parse_string(ctx, duk_to_string(ctx, 0));
}

DUK_INTERNAL duk_ret_t duk_bi_date_constructor_utc(duk_context *ctx) {
        duk_idx_t nargs = duk_get_top(ctx);
        duk_double_t dparts[DUK_DATE_IDX_NUM_PARTS];
        duk_double_t d;

        /* Behavior for nargs < 2 is implementation dependent: currently we'll
         * set a NaN time value (matching V8 behavior) in this case.
         */

        if (nargs < 2) {
                duk_push_nan(ctx);
        } else {
                duk__set_parts_from_args(ctx, dparts, nargs);
                d = duk_bi_date_get_timeval_from_dparts(dparts, 0 /*flags*/);
                duk_push_number(ctx, d);
        }
        return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_date_constructor_now(duk_context *ctx) {
        duk_double_t d;

        d = DUK_USE_DATE_GET_NOW(ctx);
        DUK_ASSERT(duk__timeclip(d) == d);  /* TimeClip() should never be necessary */
        duk_push_number(ctx, d);
        return 1;
}

/*
 *  String/JSON conversions
 *
 *  Human readable conversions are now basically ISO 8601 with a space
 *  (instead of 'T') as the date/time separator.  This is a good baseline
 *  and is platform independent.
 *
 *  A shared native helper to provide many conversions.  Magic value contains
 *  a set of flags.  The helper provides:
 *
 *    toString()
 *    toDateString()
 *    toTimeString()
 *    toLocaleString()
 *    toLocaleDateString()
 *    toLocaleTimeString()
 *    toUTCString()
 *    toISOString()
 *
 *  Notes:
 *
 *    - Date.prototype.toGMTString() and Date.prototype.toUTCString() are
 *      required to be the same Ecmascript function object (!), so it is
 *      omitted from here.
 *
 *    - Date.prototype.toUTCString(): E5.1 specification does not require a
 *      specific format, but result should be human readable.  The
 *      specification suggests using ISO 8601 format with a space (instead
 *      of 'T') separator if a more human readable format is not available.
 *
 *    - Date.prototype.toISOString(): unlike other conversion functions,
 *      toISOString() requires a RangeError for invalid date values.
 */

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_tostring_shared(duk_context *ctx) {
        duk_small_uint_t flags = duk__date_get_indirect_magic(ctx);
        return duk__to_string_helper(ctx, flags);
}

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_value_of(duk_context *ctx) {
        /* This native function is also used for Date.prototype.getTime()
         * as their behavior is identical.
         */

        duk_double_t d = duk__push_this_get_timeval(ctx, 0 /*flags*/);  /* -> [ this ] */
        DUK_ASSERT(DUK_ISFINITE(d) || DUK_ISNAN(d));
        duk_push_number(ctx, d);
        return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_to_json(duk_context *ctx) {
        /* Note: toJSON() is a generic function which works even if 'this'
         * is not a Date.  The sole argument is ignored.
         */

        duk_push_this(ctx);
        duk_to_object(ctx, -1);

        duk_dup_top(ctx);
        duk_to_primitive(ctx, -1, DUK_HINT_NUMBER);
        if (duk_is_number(ctx, -1)) {
                duk_double_t d = duk_get_number(ctx, -1);
                if (!DUK_ISFINITE(d)) {
                        duk_push_null(ctx);
                        return 1;
                }
        }
        duk_pop(ctx);

        duk_get_prop_stridx(ctx, -1, DUK_STRIDX_TO_ISO_STRING);
        duk_dup(ctx, -2);  /* -> [ O toIsoString O ] */
        duk_call_method(ctx, 0);
        return 1;
}

/*
 *  Getters.
 *
 *  Implementing getters is quite easy.  The internal time value is either
 *  NaN, or represents milliseconds (without fractions) from Jan 1, 1970.
 *  The internal time value can be converted to integer parts, and each
 *  part will be normalized and will fit into a 32-bit signed integer.
 *
 *  A shared native helper to provide all getters.  Magic value contains
 *  a set of flags and also packs the date component index argument.  The
 *  helper provides:
 *
 *    getFullYear()
 *    getUTCFullYear()
 *    getMonth()
 *    getUTCMonth()
 *    getDate()
 *    getUTCDate()
 *    getDay()
 *    getUTCDay()
 *    getHours()
 *    getUTCHours()
 *    getMinutes()
 *    getUTCMinutes()
 *    getSeconds()
 *    getUTCSeconds()
 *    getMilliseconds()
 *    getUTCMilliseconds()
 *    getYear()
 *
 *  Notes:
 *
 *    - Date.prototype.getDate(): 'date' means day-of-month, and is
 *      zero-based in internal calculations but public API expects it to
 *      be one-based.
 *
 *    - Date.prototype.getTime() and Date.prototype.valueOf() have identical
 *      behavior.  They have separate function objects, but share the same C
 *      function (duk_bi_date_prototype_value_of).
 */

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_get_shared(duk_context *ctx) {
        duk_small_uint_t flags_and_idx = duk__date_get_indirect_magic(ctx);
        return duk__get_part_helper(ctx, flags_and_idx);
}

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_get_timezone_offset(duk_context *ctx) {
        /*
         *  Return (t - LocalTime(t)) in minutes:
         *
         *    t - LocalTime(t) = t - (t + LocalTZA + DaylightSavingTA(t))
         *                     = -(LocalTZA + DaylightSavingTA(t))
         *
         *  where DaylightSavingTA() is checked for time 't'.
         *
         *  Note that the sign of the result is opposite to common usage,
         *  e.g. for EE(S)T which normally is +2h or +3h from UTC, this
         *  function returns -120 or -180.
         *
         */

        duk_double_t d;
        duk_int_t tzoffset;

        /* Note: DST adjustment is determined using UTC time. */
        d = duk__push_this_get_timeval(ctx, 0 /*flags*/);
        DUK_ASSERT(DUK_ISFINITE(d) || DUK_ISNAN(d));
        if (DUK_ISNAN(d)) {
                duk_push_nan(ctx);
        } else {
                DUK_ASSERT(DUK_ISFINITE(d));
                tzoffset = DUK_USE_DATE_GET_LOCAL_TZOFFSET(d);
                duk_push_int(ctx, -tzoffset / 60);
        }
        return 1;
}

/*
 *  Setters.
 *
 *  Setters are a bit more complicated than getters.  Component setters
 *  break down the current time value into its (normalized) component
 *  parts, replace one or more components with -unnormalized- new values,
 *  and the components are then converted back into a time value.  As an
 *  example of using unnormalized values:
 *
 *    var d = new Date(1234567890);
 *
 *  is equivalent to:
 *
 *    var d = new Date(0);
 *    d.setUTCMilliseconds(1234567890);
 *
 *  A shared native helper to provide almost all setters.  Magic value
 *  contains a set of flags and also packs the "maxnargs" argument.  The
 *  helper provides:
 *
 *    setMilliseconds()
 *    setUTCMilliseconds()
 *    setSeconds()
 *    setUTCSeconds()
 *    setMinutes()
 *    setUTCMinutes()
 *    setHours()
 *    setUTCHours()
 *    setDate()
 *    setUTCDate()
 *    setMonth()
 *    setUTCMonth()
 *    setFullYear()
 *    setUTCFullYear()
 *    setYear()
 *
 *  Notes:
 *
 *    - Date.prototype.setYear() (Section B addition): special year check
 *      is omitted.  NaN / Infinity will just flow through and ultimately
 *      result in a NaN internal time value.
 *
 *    - Date.prototype.setYear() does not have optional arguments for
 *      setting month and day-in-month (like setFullYear()), but we indicate
 *      'maxnargs' to be 3 to get the year written to the correct component
 *      index in duk__set_part_helper().  The function has nargs == 1, so only
 *      the year will be set regardless of actual argument count.
 */

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_set_shared(duk_context *ctx) {
        duk_small_uint_t flags_and_maxnargs = duk__date_get_indirect_magic(ctx);
        return duk__set_part_helper(ctx, flags_and_maxnargs);
}

DUK_INTERNAL duk_ret_t duk_bi_date_prototype_set_time(duk_context *ctx) {
        duk_double_t d;

        (void) duk__push_this_get_timeval(ctx, 0 /*flags*/); /* -> [ timeval this ] */
        d = duk__timeclip(duk_to_number(ctx, 0));
        duk_push_number(ctx, d);
        duk_dup_top(ctx);
        duk_put_prop_stridx(ctx, -3, DUK_STRIDX_INT_VALUE); /* -> [ timeval this timeval ] */

        return 1;
}