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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/*
* JS date methods.
*
* "For example, OS/360 devotes 26 bytes of the permanently
* resident date-turnover routine to the proper handling of
* December 31 on leap years (when it is Day 366). That
* might have been left to the operator."
*
* Frederick Brooks, 'The Second-System Effect'.
*/
#include "jsdate.h"
#include "mozilla/Atomics.h"
#include "mozilla/Casting.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/Sprintf.h"
#include "mozilla/TextUtils.h"
#include <algorithm>
#include <cstring>
#include <iterator>
#include <math.h>
#include <string.h>
#include "jsapi.h"
#include "jsfriendapi.h"
#include "jsnum.h"
#include "jstypes.h"
#ifdef JS_HAS_TEMPORAL_API
# include "builtin/temporal/Instant.h"
#endif
#include "js/CallAndConstruct.h" // JS::IsCallable
#include "js/Conversions.h"
#include "js/Date.h"
#include "js/friend/ErrorMessages.h" // js::GetErrorMessage, JSMSG_*
#include "js/LocaleSensitive.h"
#include "js/Object.h" // JS::GetBuiltinClass
#include "js/PropertySpec.h"
#include "js/Wrapper.h"
#include "util/DifferentialTesting.h"
#include "util/StringBuffer.h"
#include "util/Text.h"
#include "vm/DateObject.h"
#include "vm/DateTime.h"
#include "vm/GlobalObject.h"
#include "vm/Interpreter.h"
#include "vm/JSContext.h"
#include "vm/JSObject.h"
#include "vm/StringType.h"
#include "vm/Time.h"
#include "vm/Compartment-inl.h" // For js::UnwrapAndTypeCheckThis
#include "vm/GeckoProfiler-inl.h"
#include "vm/JSObject-inl.h"
using namespace js;
using mozilla::Atomic;
using mozilla::BitwiseCast;
using mozilla::IsAsciiAlpha;
using mozilla::IsAsciiDigit;
using mozilla::IsAsciiLowercaseAlpha;
using mozilla::NumbersAreIdentical;
using mozilla::Relaxed;
using JS::AutoCheckCannotGC;
using JS::ClippedTime;
using JS::GenericNaN;
using JS::GetBuiltinClass;
using JS::TimeClip;
using JS::ToInteger;
// When this value is non-zero, we'll round the time by this resolution.
static Atomic<uint32_t, Relaxed> sResolutionUsec;
// This is not implemented yet, but we will use this to know to jitter the time
// in the JS shell
static Atomic<bool, Relaxed> sJitter;
// The callback we will use for the Gecko implementation of Timer
// Clamping/Jittering
static Atomic<JS::ReduceMicrosecondTimePrecisionCallback, Relaxed>
sReduceMicrosecondTimePrecisionCallback;
/*
* The JS 'Date' object is patterned after the Java 'Date' object.
* Here is a script:
*
* today = new Date();
*
* print(today.toLocaleString());
*
* weekDay = today.getDay();
*
*
* These Java (and ECMA-262) methods are supported:
*
* UTC
* getDate (getUTCDate)
* getDay (getUTCDay)
* getHours (getUTCHours)
* getMinutes (getUTCMinutes)
* getMonth (getUTCMonth)
* getSeconds (getUTCSeconds)
* getMilliseconds (getUTCMilliseconds)
* getTime
* getTimezoneOffset
* getYear
* getFullYear (getUTCFullYear)
* parse
* setDate (setUTCDate)
* setHours (setUTCHours)
* setMinutes (setUTCMinutes)
* setMonth (setUTCMonth)
* setSeconds (setUTCSeconds)
* setMilliseconds (setUTCMilliseconds)
* setTime
* setYear (setFullYear, setUTCFullYear)
* toGMTString (toUTCString)
* toLocaleString
* toString
*
*
* These Java methods are not supported
*
* setDay
* before
* after
* equals
* hashCode
*/
namespace {
class DateTimeHelper {
private:
#if JS_HAS_INTL_API
static double localTZA(DateTimeInfo::ForceUTC forceUTC, double t,
DateTimeInfo::TimeZoneOffset offset);
#else
static int equivalentYearForDST(int year);
static bool isRepresentableAsTime32(double t);
static double daylightSavingTA(DateTimeInfo::ForceUTC forceUTC, double t);
static double adjustTime(DateTimeInfo::ForceUTC forceUTC, double date);
static PRMJTime toPRMJTime(DateTimeInfo::ForceUTC forceUTC, double localTime,
double utcTime);
#endif
public:
static double localTime(DateTimeInfo::ForceUTC forceUTC, double t);
static double UTC(DateTimeInfo::ForceUTC forceUTC, double t);
static JSString* timeZoneComment(JSContext* cx,
DateTimeInfo::ForceUTC forceUTC,
const char* locale, double utcTime,
double localTime);
#if !JS_HAS_INTL_API
static size_t formatTime(DateTimeInfo::ForceUTC forceUTC, char* buf,
size_t buflen, const char* fmt, double utcTime,
double localTime);
#endif
};
} // namespace
static DateTimeInfo::ForceUTC ForceUTC(const Realm* realm) {
return realm->creationOptions().forceUTC() ? DateTimeInfo::ForceUTC::Yes
: DateTimeInfo::ForceUTC::No;
}
// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 5.2.5 Mathematical Operations
static inline double PositiveModulo(double dividend, double divisor) {
MOZ_ASSERT(divisor > 0);
MOZ_ASSERT(std::isfinite(divisor));
double result = fmod(dividend, divisor);
if (result < 0) {
result += divisor;
}
return result + (+0.0);
}
static inline double Day(double t) { return floor(t / msPerDay); }
static double TimeWithinDay(double t) { return PositiveModulo(t, msPerDay); }
/* ES5 15.9.1.3. */
static inline bool IsLeapYear(double year) {
MOZ_ASSERT(ToInteger(year) == year);
return fmod(year, 4) == 0 && (fmod(year, 100) != 0 || fmod(year, 400) == 0);
}
static inline double DayFromYear(double y) {
return 365 * (y - 1970) + floor((y - 1969) / 4.0) -
floor((y - 1901) / 100.0) + floor((y - 1601) / 400.0);
}
static inline double TimeFromYear(double y) {
return DayFromYear(y) * msPerDay;
}
namespace {
struct YearMonthDay {
int32_t year;
uint32_t month;
uint32_t day;
};
} // namespace
/*
* This function returns the year, month and day corresponding to a given
* time value. The implementation closely follows (w.r.t. types and variable
* names) the algorithm shown in Figure 12 of [1].
*
* A key point of the algorithm is that it works on the so called
* Computational calendar where years run from March to February -- this
* largely avoids complications with leap years. The algorithm finds the
* date in the Computation calendar and then maps it to the Gregorian
* calendar.
*
* [1] Neri C, Schneider L., "Euclidean affine functions and their
* application to calendar algorithms."
* Softw Pract Exper. 2023;53(4):937-970. doi: 10.1002/spe.3172
*/
static YearMonthDay ToYearMonthDay(double t) {
MOZ_ASSERT(ToInteger(t) == t);
// Calendar cycles repeat every 400 years in the Gregorian calendar: a
// leap day is added every 4 years, removed every 100 years and added
// every 400 years. The number of days in 400 years is cycleInDays.
constexpr uint32_t cycleInYears = 400;
constexpr uint32_t cycleInDays = cycleInYears * 365 + (cycleInYears / 4) -
(cycleInYears / 100) + (cycleInYears / 400);
static_assert(cycleInDays == 146097, "Wrong calculation of cycleInDays.");
// The natural epoch for the Computational calendar is 0000/Mar/01 and
// there are rataDie1970Jan1 = 719468 days from this date to 1970/Jan/01,
// the epoch used by ES2024, 21.4.1.1.
constexpr uint32_t rataDie1970Jan1 = 719468;
constexpr uint32_t maxU32 = std::numeric_limits<uint32_t>::max();
// Let N_U be the number of days since the 1970/Jan/01. This function sets
// N = N_U + K, where K = rataDie1970Jan1 + s * cycleInDays and s is an
// integer number (to be chosen). Then, it evaluates 4 * N + 3 on uint32_t
// operands so that N must be positive and, to prevent overflow,
// 4 * N + 3 <= maxU32 <=> N <= (maxU32 - 3) / 4.
// Therefore, we must have 0 <= N_U + K <= (maxU32 - 3) / 4 or, in other
// words, N_U must be in [minDays, maxDays] = [-K, (maxU32 - 3) / 4 - K].
// Notice that this interval moves cycleInDays positions to the left when
// s is incremented. We chose s to get the interval's mid-point as close
// as possible to 0. For this, we wish to have:
// K ~= (maxU32 - 3) / 4 - K <=> 2 * K ~= (maxU32 - 3) / 4 <=>
// K ~= (maxU32 - 3) / 8 <=>
// rataDie1970Jan1 + s * cycleInDays ~= (maxU32 - 3) / 8 <=>
// s ~= ((maxU32 - 3) / 8 - rataDie1970Jan1) / cycleInDays ~= 3669.8.
// Therefore, we chose s = 3670. The shift and correction constants
// (see [1]) are then:
constexpr uint32_t s = 3670;
constexpr uint32_t K = rataDie1970Jan1 + s * cycleInDays;
constexpr uint32_t L = s * cycleInYears;
// [minDays, maxDays] correspond to a date range from -1'468'000/Mar/01 to
// 1'471'805/Jun/05.
constexpr int32_t minDays = -int32_t(K);
constexpr int32_t maxDays = (maxU32 - 3) / 4 - K;
static_assert(minDays == -536'895'458, "Wrong calculation of minDays or K.");
static_assert(maxDays == 536'846'365, "Wrong calculation of maxDays or K.");
// These are hard limits for the algorithm and far greater than the
// range [-8.64e15, 8.64e15] required by ES2024 21.4.1.1. Callers must
// ensure this function is not called out of the hard limits and,
// preferably, not outside the ES2024 limits.
constexpr int64_t minTime = minDays * int64_t(msPerDay);
[[maybe_unused]] constexpr int64_t maxTime = maxDays * int64_t(msPerDay);
MOZ_ASSERT(double(minTime) <= t && t <= double(maxTime));
const int64_t time = int64_t(t);
// Since time is the number of milliseconds since the epoch, 1970/Jan/01,
// one might expect N_U = time / uint64_t(msPerDay) is the number of days
// since epoch. There's a catch tough. Consider, for instance, half day
// before the epoch, that is, t = -0.5 * msPerDay. This falls on
// 1969/Dec/31 and should correspond to N_U = -1 but the above gives
// N_U = 0. Indeed, t / msPerDay = -0.5 but integer division truncates
// towards 0 (C++ [expr.mul]/4) and not towards -infinity as needed, so
// that time / uint64_t(msPerDay) = 0. To workaround this issue we perform
// the division on positive operands so that truncations towards 0 and
// -infinity are equivalent. For this, set u = time - minTime, which is
// positive as asserted above. Then, perform the division u / msPerDay and
// to the result add minTime / msPerDay = minDays to cancel the
// subtraction of minTime.
const uint64_t u = uint64_t(time - minTime);
const int32_t N_U = int32_t(u / uint64_t(msPerDay)) + minDays;
MOZ_ASSERT(minDays <= N_U && N_U <= maxDays);
const uint32_t N = uint32_t(N_U) + K;
// Some magic numbers have been explained above but, unfortunately,
// others with no precise interpretation do appear. They mostly come
// from numerical approximations of Euclidean affine functions (see [1])
// which are faster for the CPU to calculate. Unfortunately, no compiler
// can do these optimizations.
// Century C and year of the century N_C:
const uint32_t N_1 = 4 * N + 3;
const uint32_t C = N_1 / 146097;
const uint32_t N_C = N_1 % 146097 / 4;
// Year of the century Z and day of the year N_Y:
const uint32_t N_2 = 4 * N_C + 3;
const uint64_t P_2 = uint64_t(2939745) * N_2;
const uint32_t Z = uint32_t(P_2 / 4294967296);
const uint32_t N_Y = uint32_t(P_2 % 4294967296) / 2939745 / 4;
// Year Y:
const uint32_t Y = 100 * C + Z;
// Month M and day D.
// The expression for N_3 has been adapted to account for the difference
// between month numbers in ES5 15.9.1.4 (from 0 to 11) and [1] (from 1
// to 12). This is done by subtracting 65536 from the original
// expression so that M decreases by 1 and so does M_G further down.
const uint32_t N_3 = 2141 * N_Y + 132377; // 132377 = 197913 - 65536
const uint32_t M = N_3 / 65536;
const uint32_t D = N_3 % 65536 / 2141;
// Map from Computational to Gregorian calendar. Notice also the year
// correction and the type change and that Jan/01 is day 306 of the
// Computational calendar, cf. Table 1. [1]
constexpr uint32_t daysFromMar01ToJan01 = 306;
const uint32_t J = N_Y >= daysFromMar01ToJan01;
const int32_t Y_G = int32_t((Y - L) + J);
const uint32_t M_G = J ? M - 12 : M;
const uint32_t D_G = D + 1;
return {Y_G, M_G, D_G};
}
static double YearFromTime(double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
auto const year = ToYearMonthDay(t).year;
return double(year);
}
/* ES5 15.9.1.4. */
static double DayWithinYear(double t, double year) {
MOZ_ASSERT_IF(std::isfinite(t), YearFromTime(t) == year);
return Day(t) - DayFromYear(year);
}
static double MonthFromTime(double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
const auto month = ToYearMonthDay(t).month;
return double(month);
}
/* ES5 15.9.1.5. */
static double DateFromTime(double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
const auto day = ToYearMonthDay(t).day;
return double(day);
}
/* ES5 15.9.1.6. */
static int WeekDay(double t) {
/*
* We can't assert TimeClip(t) == t because we call this function with
* local times, which can be offset outside TimeClip's permitted range.
*/
MOZ_ASSERT(ToInteger(t) == t);
int result = (int(Day(t)) + 4) % 7;
if (result < 0) {
result += 7;
}
return result;
}
static inline int DayFromMonth(int month, bool isLeapYear) {
/*
* The following array contains the day of year for the first day of
* each month, where index 0 is January, and day 0 is January 1.
*/
static const int firstDayOfMonth[2][13] = {
{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365},
{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366}};
MOZ_ASSERT(0 <= month && month <= 12);
return firstDayOfMonth[isLeapYear][month];
}
template <typename T>
static inline int DayFromMonth(T month, bool isLeapYear) = delete;
/* ES5 15.9.1.12 (out of order to accommodate DaylightSavingTA). */
static double MakeDay(double year, double month, double date) {
/* Step 1. */
if (!std::isfinite(year) || !std::isfinite(month) || !std::isfinite(date)) {
return GenericNaN();
}
/* Steps 2-4. */
double y = ToInteger(year);
double m = ToInteger(month);
double dt = ToInteger(date);
/* Step 5. */
double ym = y + floor(m / 12);
/* Step 6. */
int mn = int(PositiveModulo(m, 12));
/* Steps 7-8. */
bool leap = IsLeapYear(ym);
double yearday = floor(TimeFromYear(ym) / msPerDay);
double monthday = DayFromMonth(mn, leap);
return yearday + monthday + dt - 1;
}
/* ES5 15.9.1.13 (out of order to accommodate DaylightSavingTA). */
static inline double MakeDate(double day, double time) {
/* Step 1. */
if (!std::isfinite(day) || !std::isfinite(time)) {
return GenericNaN();
}
/* Step 2. */
return day * msPerDay + time;
}
JS_PUBLIC_API double JS::MakeDate(double year, unsigned month, unsigned day) {
MOZ_ASSERT(month <= 11);
MOZ_ASSERT(day >= 1 && day <= 31);
return ::MakeDate(MakeDay(year, month, day), 0);
}
JS_PUBLIC_API double JS::MakeDate(double year, unsigned month, unsigned day,
double time) {
MOZ_ASSERT(month <= 11);
MOZ_ASSERT(day >= 1 && day <= 31);
return ::MakeDate(MakeDay(year, month, day), time);
}
JS_PUBLIC_API double JS::YearFromTime(double time) {
const auto clipped = TimeClip(time);
if (!clipped.isValid()) {
return GenericNaN();
}
return ::YearFromTime(clipped.toDouble());
}
JS_PUBLIC_API double JS::MonthFromTime(double time) {
const auto clipped = TimeClip(time);
if (!clipped.isValid()) {
return GenericNaN();
}
return ::MonthFromTime(clipped.toDouble());
}
JS_PUBLIC_API double JS::DayFromTime(double time) {
const auto clipped = TimeClip(time);
if (!clipped.isValid()) {
return GenericNaN();
}
return DateFromTime(clipped.toDouble());
}
JS_PUBLIC_API double JS::DayFromYear(double year) {
return ::DayFromYear(year);
}
JS_PUBLIC_API double JS::DayWithinYear(double time, double year) {
const auto clipped = TimeClip(time);
if (!clipped.isValid()) {
return GenericNaN();
}
return ::DayWithinYear(clipped.toDouble(), year);
}
JS_PUBLIC_API void JS::SetReduceMicrosecondTimePrecisionCallback(
JS::ReduceMicrosecondTimePrecisionCallback callback) {
sReduceMicrosecondTimePrecisionCallback = callback;
}
JS_PUBLIC_API JS::ReduceMicrosecondTimePrecisionCallback
JS::GetReduceMicrosecondTimePrecisionCallback() {
return sReduceMicrosecondTimePrecisionCallback;
}
JS_PUBLIC_API void JS::SetTimeResolutionUsec(uint32_t resolution, bool jitter) {
sResolutionUsec = resolution;
sJitter = jitter;
}
#if JS_HAS_INTL_API
// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.7 LocalTZA ( t, isUTC )
double DateTimeHelper::localTZA(DateTimeInfo::ForceUTC forceUTC, double t,
DateTimeInfo::TimeZoneOffset offset) {
MOZ_ASSERT(std::isfinite(t));
int64_t milliseconds = static_cast<int64_t>(t);
int32_t offsetMilliseconds =
DateTimeInfo::getOffsetMilliseconds(forceUTC, milliseconds, offset);
return static_cast<double>(offsetMilliseconds);
}
// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.8 LocalTime ( t )
double DateTimeHelper::localTime(DateTimeInfo::ForceUTC forceUTC, double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
MOZ_ASSERT(StartOfTime <= t && t <= EndOfTime);
return t + localTZA(forceUTC, t, DateTimeInfo::TimeZoneOffset::UTC);
}
// ES2019 draft rev 0ceb728a1adbffe42b26972a6541fd7f398b1557
// 20.3.1.9 UTC ( t )
double DateTimeHelper::UTC(DateTimeInfo::ForceUTC forceUTC, double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
if (t < (StartOfTime - msPerDay) || t > (EndOfTime + msPerDay)) {
return GenericNaN();
}
return t - localTZA(forceUTC, t, DateTimeInfo::TimeZoneOffset::Local);
}
#else
/*
* Find a year for which any given date will fall on the same weekday.
*
* This function should be used with caution when used other than
* for determining DST; it hasn't been proven not to produce an
* incorrect year for times near year boundaries.
*/
int DateTimeHelper::equivalentYearForDST(int year) {
/*
* Years and leap years on which Jan 1 is a Sunday, Monday, etc.
*
* yearStartingWith[0][i] is an example non-leap year where
* Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
*
* yearStartingWith[1][i] is an example leap year where
* Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
*
* Keep two different mappings, one for past years (< 1970), and a
* different one for future years (> 2037).
*/
static const int pastYearStartingWith[2][7] = {
{1978, 1973, 1974, 1975, 1981, 1971, 1977},
{1984, 1996, 1980, 1992, 1976, 1988, 1972}};
static const int futureYearStartingWith[2][7] = {
{2034, 2035, 2030, 2031, 2037, 2027, 2033},
{2012, 2024, 2036, 2020, 2032, 2016, 2028}};
int day = int(DayFromYear(year) + 4) % 7;
if (day < 0) {
day += 7;
}
const auto& yearStartingWith =
year < 1970 ? pastYearStartingWith : futureYearStartingWith;
return yearStartingWith[IsLeapYear(year)][day];
}
// Return true if |t| is representable as a 32-bit time_t variable, that means
// the year is in [1970, 2038).
bool DateTimeHelper::isRepresentableAsTime32(double t) {
return 0.0 <= t && t < 2145916800000.0;
}
/* ES5 15.9.1.8. */
double DateTimeHelper::daylightSavingTA(DateTimeInfo::ForceUTC forceUTC,
double t) {
if (!std::isfinite(t)) {
return GenericNaN();
}
/*
* If earlier than 1970 or after 2038, potentially beyond the ken of
* many OSes, map it to an equivalent year before asking.
*/
if (!isRepresentableAsTime32(t)) {
int year = equivalentYearForDST(int(YearFromTime(t)));
double day = MakeDay(year, MonthFromTime(t), DateFromTime(t));
t = MakeDate(day, TimeWithinDay(t));
}
int64_t utcMilliseconds = static_cast<int64_t>(t);
int32_t offsetMilliseconds =
DateTimeInfo::getDSTOffsetMilliseconds(forceUTC, utcMilliseconds);
return static_cast<double>(offsetMilliseconds);
}
double DateTimeHelper::adjustTime(DateTimeInfo::ForceUTC forceUTC,
double date) {
double localTZA = DateTimeInfo::localTZA(forceUTC);
double t = daylightSavingTA(forceUTC, date) + localTZA;
t = (localTZA >= 0) ? fmod(t, msPerDay) : -fmod(msPerDay - t, msPerDay);
return t;
}
/* ES5 15.9.1.9. */
double DateTimeHelper::localTime(DateTimeInfo::ForceUTC forceUTC, double t) {
return t + adjustTime(forceUTC, t);
}
double DateTimeHelper::UTC(DateTimeInfo::ForceUTC forceUTC, double t) {
// Following the ES2017 specification creates undesirable results at DST
// transitions. For example when transitioning from PST to PDT,
// |new Date(2016,2,13,2,0,0).toTimeString()| returns the string value
// "01:00:00 GMT-0800 (PST)" instead of "03:00:00 GMT-0700 (PDT)". Follow
// V8 and subtract one hour before computing the offset.
return t -
adjustTime(forceUTC, t - DateTimeInfo::localTZA(forceUTC) - msPerHour);
}
#endif /* JS_HAS_INTL_API */
static double LocalTime(DateTimeInfo::ForceUTC forceUTC, double t) {
return DateTimeHelper::localTime(forceUTC, t);
}
static double UTC(DateTimeInfo::ForceUTC forceUTC, double t) {
return DateTimeHelper::UTC(forceUTC, t);
}
/* ES5 15.9.1.10. */
static double HourFromTime(double t) {
return PositiveModulo(floor(t / msPerHour), HoursPerDay);
}
static double MinFromTime(double t) {
return PositiveModulo(floor(t / msPerMinute), MinutesPerHour);
}
static double SecFromTime(double t) {
return PositiveModulo(floor(t / msPerSecond), SecondsPerMinute);
}
static double msFromTime(double t) { return PositiveModulo(t, msPerSecond); }
/* ES5 15.9.1.11. */
static double MakeTime(double hour, double min, double sec, double ms) {
/* Step 1. */
if (!std::isfinite(hour) || !std::isfinite(min) || !std::isfinite(sec) ||
!std::isfinite(ms)) {
return GenericNaN();
}
/* Step 2. */
double h = ToInteger(hour);
/* Step 3. */
double m = ToInteger(min);
/* Step 4. */
double s = ToInteger(sec);
/* Step 5. */
double milli = ToInteger(ms);
/* Steps 6-7. */
return h * msPerHour + m * msPerMinute + s * msPerSecond + milli;
}
/**
* end of ECMA 'support' functions
*/
// ES2017 draft rev (TODO: Add git hash when PR 642 is merged.)
// 20.3.3.4
// Date.UTC(year [, month [, date [, hours [, minutes [, seconds [, ms]]]]]])
static bool date_UTC(JSContext* cx, unsigned argc, Value* vp) {
AutoJSMethodProfilerEntry pseudoFrame(cx, "Date", "UTC");
CallArgs args = CallArgsFromVp(argc, vp);
// Step 1.
double y;
if (!ToNumber(cx, args.get(0), &y)) {
return false;
}
// Step 2.
double m;
if (args.length() >= 2) {
if (!ToNumber(cx, args[1], &m)) {
return false;
}
} else {
m = 0;
}
// Step 3.
double dt;
if (args.length() >= 3) {
if (!ToNumber(cx, args[2], &dt)) {
return false;
}
} else {
dt = 1;
}
// Step 4.
double h;
if (args.length() >= 4) {
if (!ToNumber(cx, args[3], &h)) {
return false;
}
} else {
h = 0;
}
// Step 5.
double min;
if (args.length() >= 5) {
if (!ToNumber(cx, args[4], &min)) {
return false;
}
} else {
min = 0;
}
// Step 6.
double s;
if (args.length() >= 6) {
if (!ToNumber(cx, args[5], &s)) {
return false;
}
} else {
s = 0;
}
// Step 7.
double milli;
if (args.length() >= 7) {
if (!ToNumber(cx, args[6], &milli)) {
return false;
}
} else {
milli = 0;
}
// Step 8.
double yr = y;
if (!std::isnan(y)) {
double yint = ToInteger(y);
if (0 <= yint && yint <= 99) {
yr = 1900 + yint;
}
}
// Step 9.
ClippedTime time =
TimeClip(MakeDate(MakeDay(yr, m, dt), MakeTime(h, min, s, milli)));
args.rval().set(TimeValue(time));
return true;
}
/*
* Read and convert decimal digits from s[*i] into *result
* while *i < limit.
*
* Succeed if any digits are converted. Advance *i only
* as digits are consumed.
*/
template <typename CharT>
static bool ParseDigits(size_t* result, const CharT* s, size_t* i,
size_t limit) {
size_t init = *i;
*result = 0;
while (*i < limit && ('0' <= s[*i] && s[*i] <= '9')) {
*result *= 10;
*result += (s[*i] - '0');
++(*i);
}
return *i != init;
}
/*
* Read and convert decimal digits to the right of a decimal point,
* representing a fractional integer, from s[*i] into *result
* while *i < limit, up to 3 digits. Consumes any digits beyond 3
* without affecting the result.
*
* Succeed if any digits are converted. Advance *i only
* as digits are consumed.
*/
template <typename CharT>
static bool ParseFractional(int* result, const CharT* s, size_t* i,
size_t limit) {
int factor = 100;
size_t init = *i;
*result = 0;
for (; *i < limit && ('0' <= s[*i] && s[*i] <= '9'); ++(*i)) {
if (*i - init >= 3) {
// If we're past 3 digits, do nothing with it, but continue to
// consume the remainder of the digits
continue;
}
*result += (s[*i] - '0') * factor;
factor /= 10;
}
return *i != init;
}
/*
* Read and convert exactly n decimal digits from s[*i]
* to s[min(*i+n,limit)] into *result.
*
* Succeed if exactly n digits are converted. Advance *i only
* on success.
*/
template <typename CharT>
static bool ParseDigitsN(size_t n, size_t* result, const CharT* s, size_t* i,
size_t limit) {
size_t init = *i;
if (ParseDigits(result, s, i, std::min(limit, init + n))) {
return (*i - init) == n;
}
*i = init;
return false;
}
/*
* Read and convert n or less decimal digits from s[*i]
* to s[min(*i+n,limit)] into *result.
*
* Succeed only if greater than zero but less than or equal to n digits are
* converted. Advance *i only on success.
*/
template <typename CharT>
static bool ParseDigitsNOrLess(size_t n, size_t* result, const CharT* s,
size_t* i, size_t limit) {
size_t init = *i;
if (ParseDigits(result, s, i, std::min(limit, init + n))) {
return ((*i - init) > 0) && ((*i - init) <= n);
}
*i = init;
return false;
}
static int DaysInMonth(int year, int month) {
bool leap = IsLeapYear(year);
int result = int(DayFromMonth(month, leap) - DayFromMonth(month - 1, leap));
return result;
}
/*
* Parse a string according to the formats specified in the standard:
*
*
* These formats are based upon a simplification of the ISO 8601 Extended
* Format. As per the spec omitted month and day values are defaulted to '01',
* omitted HH:mm:ss values are defaulted to '00' and an omitted sss field is
* defaulted to '000'.
*
* For cross compatibility we allow the following extensions.
*
* These are:
*
* One or more decimal digits for milliseconds:
* The specification requires exactly three decimal digits for
* the fractional part but we allow for one or more digits.
*
* Time zone specifier without ':':
* We allow the time zone to be specified without a ':' character.
* E.g. "T19:00:00+0700" is equivalent to "T19:00:00+07:00".
*
* Date part:
*
* Year:
* YYYY (eg 1997)
*
* Year and month:
* YYYY-MM (eg 1997-07)
*
* Complete date:
* YYYY-MM-DD (eg 1997-07-16)
*
* Time part:
*
* Hours and minutes:
* Thh:mmTZD (eg T19:20+01:00)
*
* Hours, minutes and seconds:
* Thh:mm:ssTZD (eg T19:20:30+01:00)
*
* Hours, minutes, seconds and a decimal fraction of a second:
* Thh:mm:ss.sssTZD (eg T19:20:30.45+01:00)
*
* where:
*
* YYYY = four-digit year or six digit year as +YYYYYY or -YYYYYY
* MM = two-digit month (01=January, etc.)
* DD = two-digit day of month (01 through 31)
* hh = two digits of hour (00 through 24) (am/pm NOT allowed)
* mm = two digits of minute (00 through 59)
* ss = two digits of second (00 through 59)
* sss = one or more digits representing a decimal fraction of a second
* TZD = time zone designator (Z or +hh:mm or -hh:mm or missing for local)
*/
template <typename CharT>
static bool ParseISOStyleDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
size_t length, ClippedTime* result) {
size_t i = 0;
int tzMul = 1;
int dateMul = 1;
size_t year = 1970;
size_t month = 1;
size_t day = 1;
size_t hour = 0;
size_t min = 0;
size_t sec = 0;
int msec = 0;
bool isLocalTime = false;
size_t tzHour = 0;
size_t tzMin = 0;
#define PEEK(ch) (i < length && s[i] == ch)
#define NEED(ch) \
if (i >= length || s[i] != ch) { \
return false; \
} else { \
++i; \
}
#define DONE_DATE_UNLESS(ch) \
if (i >= length || s[i] != ch) { \
goto done_date; \
} else { \
++i; \
}
#define DONE_UNLESS(ch) \
if (i >= length || s[i] != ch) { \
goto done; \
} else { \
++i; \
}
#define NEED_NDIGITS(n, field) \
if (!ParseDigitsN(n, &field, s, &i, length)) { \
return false; \
}
if (PEEK('+') || PEEK('-')) {
if (PEEK('-')) {
dateMul = -1;
}
++i;
NEED_NDIGITS(6, year);
// -000000 is not a valid expanded year.
if (year == 0 && dateMul == -1) {
return false;
}
} else {
NEED_NDIGITS(4, year);
}
DONE_DATE_UNLESS('-');
NEED_NDIGITS(2, month);
DONE_DATE_UNLESS('-');
NEED_NDIGITS(2, day);
done_date:
if (PEEK('T')) {
++i;
} else {
goto done;
}
NEED_NDIGITS(2, hour);
NEED(':');
NEED_NDIGITS(2, min);
if (PEEK(':')) {
++i;
NEED_NDIGITS(2, sec);
if (PEEK('.')) {
++i;
if (!ParseFractional(&msec, s, &i, length)) {
return false;
}
}
}
if (PEEK('Z')) {
++i;
} else if (PEEK('+') || PEEK('-')) {
if (PEEK('-')) {
tzMul = -1;
}
++i;
NEED_NDIGITS(2, tzHour);
/*
* Non-standard extension to the ISO date format (permitted by ES5):
* allow "-0700" as a time zone offset, not just "-07:00".
*/
if (PEEK(':')) {
++i;
}
NEED_NDIGITS(2, tzMin);
} else {
isLocalTime = true;
}
done:
if (year > 275943 // ceil(1e8/365) + 1970
|| (month == 0 || month > 12) ||
(day == 0 || day > size_t(DaysInMonth(year, month))) || hour > 24 ||
((hour == 24) && (min > 0 || sec > 0 || msec > 0)) || min > 59 ||
sec > 59 || tzHour > 23 || tzMin > 59) {
return false;
}
if (i != length) {
return false;
}
month -= 1; /* convert month to 0-based */
double date = MakeDate(MakeDay(dateMul * double(year), month, day),
MakeTime(hour, min, sec, msec));
if (isLocalTime) {
date = UTC(forceUTC, date);
} else {
date -= tzMul * (tzHour * msPerHour + tzMin * msPerMinute);
}
*result = TimeClip(date);
return NumbersAreIdentical(date, result->toDouble());
#undef PEEK
#undef NEED
#undef DONE_UNLESS
#undef NEED_NDIGITS
}
int FixupNonFullYear(int year) {
if (year < 50) {
year += 2000;
} else if (year >= 50 && year < 100) {
year += 1900;
}
return year;
}
template <typename CharT>
bool IsPrefixOfKeyword(const CharT* s, size_t len, const char* keyword) {
while (len > 0 && *keyword) {
MOZ_ASSERT(IsAsciiAlpha(*s));
MOZ_ASSERT(IsAsciiLowercaseAlpha(*keyword));
if (unicode::ToLowerCase(static_cast<Latin1Char>(*s)) != *keyword) {
break;
}
s++, keyword++;
len--;
}
return len == 0;
}
static constexpr const char* const month_prefixes[] = {
"jan", "feb", "mar", "apr", "may", "jun",
"jul", "aug", "sep", "oct", "nov", "dec",
};
/**
* Given a string s of length >= 3, checks if it begins,
* case-insensitive, with the given lower case prefix.
*/
template <typename CharT>
bool StartsWithMonthPrefix(const CharT* s, const char* prefix) {
MOZ_ASSERT(strlen(prefix) == 3);
for (size_t i = 0; i < 3; ++i) {
MOZ_ASSERT(IsAsciiAlpha(*s));
MOZ_ASSERT(IsAsciiLowercaseAlpha(*prefix));
if (unicode::ToLowerCase(static_cast<Latin1Char>(*s)) != *prefix) {
return false;
}
++s, ++prefix;
}
return true;
}
template <typename CharT>
bool IsMonthName(const CharT* s, size_t len, int* mon) {
// Month abbreviations < 3 chars are not accepted.
if (len < 3) {
return false;
}
for (size_t m = 0; m < std::size(month_prefixes); ++m) {
if (StartsWithMonthPrefix(s, month_prefixes[m])) {
// Use numeric value.
*mon = m + 1;
return true;
}
}
return false;
}
/*
* Try to parse the following date formats:
* dd-MMM-yyyy
* dd-MMM-yy
* MMM-dd-yyyy
* MMM-dd-yy
* yyyy-MMM-dd
* yy-MMM-dd
*
* Returns true and fills all out parameters when successfully parsed
* dashed-date. Otherwise returns false and leaves out parameters untouched.
*/
template <typename CharT>
static bool TryParseDashedDatePrefix(const CharT* s, size_t length,
size_t* indexOut, int* yearOut,
int* monOut, int* mdayOut) {
size_t i = *indexOut;
size_t pre = i;
size_t mday;
if (!ParseDigitsNOrLess(6, &mday, s, &i, length)) {
return false;
}
size_t mdayDigits = i - pre;
if (i >= length || s[i] != '-') {
return false;
}
++i;
int mon = 0;
if (*monOut == -1) {
// If month wasn't already set by ParseDate, it must be in the middle of
// this format, let's look for it
size_t start = i;
for (; i < length; i++) {
if (!IsAsciiAlpha(s[i])) {
break;
}
}
if (!IsMonthName(s + start, i - start, &mon)) {
return false;
}
if (i >= length || s[i] != '-') {
return false;
}
++i;
}
pre = i;
size_t year;
if (!ParseDigitsNOrLess(6, &year, s, &i, length)) {
return false;
}
size_t yearDigits = i - pre;
if (i < length && IsAsciiDigit(s[i])) {
return false;
}
// Swap the mday and year if the year wasn't specified in full.
if (mday > 31 && year <= 31 && yearDigits < 4) {
std::swap(mday, year);
std::swap(mdayDigits, yearDigits);
}
if (mday > 31 || mdayDigits > 2) {
return false;
}
if (yearDigits < 4) {
year = FixupNonFullYear(year);
}
*indexOut = i;
*yearOut = year;
if (*monOut == -1) {
*monOut = mon;
}
*mdayOut = mday;
return true;
}
/*
* Try to parse dates in the style of YYYY-MM-DD which do not conform to
* the formal standard from ParseISOStyleDate. This includes cases such as
*
* - Year does not have 4 digits
* - Month or mday has 1 digit
* - Space in between date and time, rather than a 'T'
*
* Regarding the last case, this function only parses out the date, returning
* to ParseDate to finish parsing the time and timezone, if present.
*
* Returns true and fills all out parameters when successfully parsed
* dashed-date. Otherwise returns false and leaves out parameters untouched.
*/
template <typename CharT>
static bool TryParseDashedNumericDatePrefix(const CharT* s, size_t length,
size_t* indexOut, int* yearOut,
int* monOut, int* mdayOut) {
size_t i = *indexOut;
size_t first;
if (!ParseDigitsNOrLess(6, &first, s, &i, length)) {
return false;
}
if (i >= length || s[i] != '-') {
return false;
}
++i;
size_t second;
if (!ParseDigitsNOrLess(2, &second, s, &i, length)) {
return false;
}
if (i >= length || s[i] != '-') {
return false;
}
++i;
size_t third;
if (!ParseDigitsNOrLess(6, &third, s, &i, length)) {
return false;
}
int year;
int mon = -1;
int mday = -1;
// 1 or 2 digits for the first number is tricky; 1-12 means it's a month, 0 or
// >31 means it's a year, and 13-31 is invalid due to ambiguity.
if (first >= 1 && first <= 12) {
mon = first;
} else if (first == 0 || first > 31) {
year = first;
} else {
return false;
}
if (mon < 0) {
// If month hasn't been set yet, it's definitely the 2nd number
mon = second;
} else {
// If it has, the next number is the mday
mday = second;
}
if (mday < 0) {
// The third number is probably the mday...
mday = third;
} else {
// But otherwise, it's the year
year = third;
}
if (mon < 1 || mon > 12 || mday < 1 || mday > 31) {
return false;
}
if (year < 100) {
year = FixupNonFullYear(year);
}
*indexOut = i;
*yearOut = year;
*monOut = mon;
*mdayOut = mday;
return true;
}
struct CharsAndAction {
const char* chars;
int action;
};
static constexpr CharsAndAction keywords[] = {
// clang-format off
// AM/PM
{ "am", -1 },
{ "pm", -2 },
// Days of week.
{ "monday", 0 },
{ "tuesday", 0 },
{ "wednesday", 0 },
{ "thursday", 0 },
{ "friday", 0 },
{ "saturday", 0 },
{ "sunday", 0 },
// Time zone abbreviations.
{ "gmt", 10000 + 0 },
{ "z", 10000 + 0 },
{ "ut", 10000 + 0 },
{ "utc", 10000 + 0 },
{ "est", 10000 + 5 * 60 },
{ "edt", 10000 + 4 * 60 },
{ "cst", 10000 + 6 * 60 },
{ "cdt", 10000 + 5 * 60 },
{ "mst", 10000 + 7 * 60 },
{ "mdt", 10000 + 6 * 60 },
{ "pst", 10000 + 8 * 60 },
{ "pdt", 10000 + 7 * 60 },
// clang-format on
};
template <size_t N>
constexpr size_t MinKeywordLength(const CharsAndAction (&keywords)[N]) {
size_t min = size_t(-1);
for (const CharsAndAction& keyword : keywords) {
min = std::min(min, std::char_traits<char>::length(keyword.chars));
}
return min;
}
template <typename CharT>
static bool ParseDate(DateTimeInfo::ForceUTC forceUTC, const CharT* s,
size_t length, ClippedTime* result,
bool* countLateWeekday) {
if (length == 0) {
return false;
}
if (ParseISOStyleDate(forceUTC, s, length, result)) {
return true;
}
size_t index = 0;
int mon = -1;
bool seenMonthName = false;
// Before we begin, we need to scrub any words from the beginning of the
// string up to the first number, recording the month if we encounter it
for (; index < length; index++) {
int c = s[index];
if (strchr(" ,.-/", c)) {
continue;
}
if (!IsAsciiAlpha(c)) {
break;
}
size_t start = index;
index++;
for (; index < length; index++) {
if (!IsAsciiAlpha(s[index])) {
break;
}
}
if (IsMonthName(s + start, index - start, &mon)) {
seenMonthName = true;
}
}
if (index >= length) {
return false;
}
int year = -1;
int mday = -1;
int hour = -1;
int min = -1;
int sec = -1;
int msec = 0;
int tzOffset = -1;
// One of '+', '-', ':', '/', or 0 (the default value).
int prevc = 0;
bool seenPlusMinus = false;
bool seenFullYear = false;
bool negativeYear = false;
// Includes "GMT", "UTC", "UT", and "Z" timezone keywords
bool seenGmtAbbr = false;
// For telemetry purposes
bool seenLateWeekday = false;
// Try parsing the leading dashed-date.
//
// If successfully parsed, index is updated to the end of the date part,
// and year, mon, mday are set to the date.
// Continue parsing optional time + tzOffset parts.
//
// Otherwise, this is no-op.
bool isDashedDate =
TryParseDashedDatePrefix(s, length, &index, &year, &mon, &mday) ||
TryParseDashedNumericDatePrefix(s, length, &index, &year, &mon, &mday);
if (isDashedDate && index < length && strchr("T:+", s[index])) {
return false;
}
while (index < length) {
int c = s[index];
index++;
// Normalize U+202F (NARROW NO-BREAK SPACE). This character appears between
// the AM/PM markers for |date.toLocaleString("en")|. We have to normalize
// it for backward compatibility reasons.
if (c == 0x202F) {
c = ' ';
}
if ((c == '+' || c == '-') &&
// Reject + or - after timezone (still allowing for negative year)
((seenPlusMinus && year != -1) ||
// Reject timezones like "1995-09-26 -04:30" (if the - is right up
// against the previous number, it will get parsed as a time,
// see the other comment below)
(year != -1 && hour == -1 && !seenGmtAbbr &&
!IsAsciiDigit(s[index - 2])))) {
return false;
}
// Spaces, ASCII control characters, periods, and commas are simply ignored.
if (c <= ' ' || c == '.' || c == ',') {
continue;
}
// Parse delimiter characters. Save them to the side for future use.
if (c == '/' || c == ':' || c == '+') {
prevc = c;
continue;
}
// Dashes are delimiters if they're immediately followed by a number field.
// If they're not followed by a number field, they're simply ignored.
if (c == '-') {
if (index < length && IsAsciiDigit(s[index])) {
prevc = c;
}
continue;
}
// Skip over comments -- text inside matching parentheses. (Comments
// themselves may contain comments as long as all the parentheses properly
// match up. And apparently comments, including nested ones, may validly be
// terminated by end of input...)
if (c == '(') {
int depth = 1;
while (index < length) {
c = s[index];
index++;
if (c == '(') {
depth++;
} else if (c == ')') {
if (--depth <= 0) {
break;
}
}
}
continue;
}
// Parse a number field.
if (IsAsciiDigit(c)) {
size_t partStart = index - 1;
uint32_t u = c - '0';
while (index < length) {
c = s[index];
if (!IsAsciiDigit(c)) {
break;
}
u = u * 10 + (c - '0');
index++;
}
size_t partLength = index - partStart;
// See above for why we have to normalize U+202F.
if (c == 0x202F) {
c = ' ';
}
int n = int(u);
/*
* Allow TZA before the year, so 'Wed Nov 05 21:49:11 GMT-0800 1997'
* works.
*
* Uses of seenPlusMinus allow ':' in TZA, so Java no-timezone style
* of GMT+4:30 works.
*/
if (prevc == '-' && (tzOffset != 0 || seenPlusMinus) && partLength >= 4 &&
year < 0) {
// Parse as a negative, possibly zero-padded year if
// 1. the preceding character is '-',
// 2. the TZA is not 'GMT' (tested by |tzOffset != 0|),
// 3. or a TZA was already parsed |seenPlusMinus == true|,
// 4. the part length is at least 4 (to parse '-08' as a TZA),
// 5. and we did not already parse a year |year < 0|.
year = n;
seenFullYear = true;
negativeYear = true;
} else if ((prevc == '+' || prevc == '-') &&
// "1995-09-26-04:30" needs to be parsed as a time,
// not a time zone
(seenGmtAbbr || hour != -1)) {
/* Make ':' case below change tzOffset. */
seenPlusMinus = true;
/* offset */
if (n < 24 && partLength <= 2) {
n = n * 60; /* EG. "GMT-3" */
} else {
n = n % 100 + n / 100 * 60; /* eg "GMT-0430" */
}
if (prevc == '+') /* plus means east of GMT */
n = -n;
// Reject if not preceded by 'GMT' or if a time zone offset
// was already parsed.
if (tzOffset != 0 && tzOffset != -1) {
return false;
}
tzOffset = n;
} else if (prevc == '/' && mon >= 0 && mday >= 0 && year < 0) {
if (c <= ' ' || c == ',' || c == '/' || index >= length) {
year = n;
} else {
return false;
}
} else if (c == ':') {
if (hour < 0) {
hour = /*byte*/ n;
} else if (min < 0) {
min = /*byte*/ n;
} else {
return false;
}
} else if (c == '/') {
/*
* Until it is determined that mon is the actual month, keep
* it as 1-based rather than 0-based.
*/
if (mon < 0) {
mon = /*byte*/ n;
} else if (mday < 0) {
mday = /*byte*/ n;
} else {
return false;
}
} else if (index < length && c != ',' && c > ' ' && c != '-' &&
c != '(' &&
// Allow '.' as a delimiter until seconds have been parsed
// (this allows the decimal for milliseconds)
(c != '.' || sec != -1) &&
// Allow zulu time e.g. "09/26/1995 16:00Z", or
// '+' directly after time e.g. 00:00+0500
!(hour != -1 && strchr("Zz+", c)) &&
// Allow month or AM/PM directly after a number
(!IsAsciiAlpha(c) ||
(mon != -1 && !(strchr("AaPp", c) && index < length - 1 &&
strchr("Mm", s[index + 1]))))) {
return false;
} else if (seenPlusMinus && n < 60) { /* handle GMT-3:30 */
if (tzOffset < 0) {
tzOffset -= n;
} else {
tzOffset += n;
}
} else if (hour >= 0 && min < 0) {
min = /*byte*/ n;
} else if (prevc == ':' && min >= 0 && sec < 0) {
sec = /*byte*/ n;
if (c == '.') {
index++;
if (!ParseFractional(&msec, s, &index, length)) {
return false;
}
}
} else if (mon < 0) {
mon = /*byte*/ n;
} else if (mon >= 0 && mday < 0) {
mday = /*byte*/ n;
} else if (mon >= 0 && mday >= 0 && year < 0) {
year = n;
seenFullYear = partLength >= 4;
} else {
return false;
}
prevc = 0;
continue;
}
// Parse fields that are words: ASCII letters spelling out in English AM/PM,
// day of week, month, or an extremely limited set of legacy time zone
// abbreviations.
if (IsAsciiAlpha(c)) {
size_t start = index - 1;
while (index < length) {
c = s[index];
if (!IsAsciiAlpha(c)) {
break;
}
index++;
}
// There must be at least as many letters as in the shortest keyword.
constexpr size_t MinLength = MinKeywordLength(keywords);
if (index - start < MinLength) {
return false;
}
size_t k = std::size(keywords);
while (k-- > 0) {
// Record a month if it is a month name. Note that some numbers are
// initially treated as months; if a numeric field has already been
// interpreted as a month, store that value to the actually appropriate
// date component and set the month here.
int tryMonth;
if (IsMonthName(s + start, index - start, &tryMonth)) {
if (seenMonthName) {
// Overwrite the previous month name
mon = tryMonth;
break;
}
seenMonthName = true;
if (mon < 0) {
mon = tryMonth;
} else if (mday < 0) {
mday = mon;
mon = tryMonth;
} else if (year < 0) {
if (mday > 0) {
// If the date is of the form f l month, then when month is
// reached we have f in mon and l in mday. In order to be
// consistent with the f month l and month f l forms, we need to
// swap so that f is in mday and l is in year.
year = mday;
mday = mon;
} else {
year = mon;
}