From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001 From: "Matt A. Tobin" Date: Fri, 2 Feb 2018 04:16:08 -0500 Subject: Add m-esr52 at 52.6.0 --- js/public/Date.h | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 170 insertions(+) create mode 100644 js/public/Date.h (limited to 'js/public/Date.h') diff --git a/js/public/Date.h b/js/public/Date.h new file mode 100644 index 000000000..cba0ea875 --- /dev/null +++ b/js/public/Date.h @@ -0,0 +1,170 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* 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 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* JavaScript date/time computation and creation functions. */ + +#ifndef js_Date_h +#define js_Date_h + +/* + * Dates in JavaScript are defined by IEEE-754 double precision numbers from + * the set: + * + * { t ∈ ℕ : -8.64e15 ≤ t ≤ +8.64e15 } ∪ { NaN } + * + * The single NaN value represents any invalid-date value. All other values + * represent idealized durations in milliseconds since the UTC epoch. (Leap + * seconds are ignored; leap days are not.) +0 is the only zero in this set. + * The limit represented by 8.64e15 milliseconds is 100 million days either + * side of 00:00 January 1, 1970 UTC. + * + * Dates in the above set are represented by the |ClippedTime| class. The + * double type is a superset of the above set, so it *may* (but need not) + * represent a date. Use ECMAScript's |TimeClip| method to produce a date from + * a double. + * + * Date *objects* are simply wrappers around |TimeClip|'d numbers, with a bunch + * of accessor methods to the various aspects of the represented date. + */ + +#include "mozilla/FloatingPoint.h" +#include "mozilla/MathAlgorithms.h" + +#include "js/Conversions.h" +#include "js/Value.h" + +struct JSContext; + +namespace JS { + +/** + * Re-query the system to determine the current time zone adjustment from UTC, + * including any component due to DST. If the time zone has changed, this will + * cause all Date object non-UTC methods and formatting functions to produce + * appropriately adjusted results. + * + * Left to its own devices, SpiderMonkey itself may occasionally call this + * method to attempt to keep up with system time changes. However, no + * particular frequency of checking is guaranteed. Embedders unable to accept + * occasional inaccuracies should call this method in response to system time + * changes, or immediately before operations requiring instantaneous + * correctness, to guarantee correct behavior. + */ +extern JS_PUBLIC_API(void) +ResetTimeZone(); + +class ClippedTime; +inline ClippedTime TimeClip(double time); + +/* + * |ClippedTime| represents the limited subset of dates/times described above. + * + * An invalid date/time may be created through the |ClippedTime::invalid| + * method. Otherwise, a |ClippedTime| may be created using the |TimeClip| + * method. + * + * In typical use, the user might wish to manipulate a timestamp. The user + * performs a series of operations on it, but the final value might not be a + * date as defined above -- it could have overflowed, acquired a fractional + * component, &c. So as a *final* step, the user passes that value through + * |TimeClip| to produce a number restricted to JavaScript's date range. + * + * APIs that accept a JavaScript date value thus accept a |ClippedTime|, not a + * double. This ensures that date/time APIs will only ever receive acceptable + * JavaScript dates. This also forces users to perform any desired clipping, + * as only the user knows what behavior is desired when clipping occurs. + */ +class ClippedTime +{ + double t; + + explicit ClippedTime(double time) : t(time) {} + friend ClippedTime TimeClip(double time); + + public: + // Create an invalid date. + ClippedTime() : t(mozilla::UnspecifiedNaN()) {} + + // Create an invalid date/time, more explicitly; prefer this to the default + // constructor. + static ClippedTime invalid() { return ClippedTime(); } + + double toDouble() const { return t; } + + bool isValid() const { return !mozilla::IsNaN(t); } +}; + +// ES6 20.3.1.15. +// +// Clip a double to JavaScript's date range (or to an invalid date) using the +// ECMAScript TimeClip algorithm. +inline ClippedTime +TimeClip(double time) +{ + // Steps 1-2. + const double MaxTimeMagnitude = 8.64e15; + if (!mozilla::IsFinite(time) || mozilla::Abs(time) > MaxTimeMagnitude) + return ClippedTime(mozilla::UnspecifiedNaN()); + + // Step 3. + return ClippedTime(ToInteger(time) + (+0.0)); +} + +// Produce a double Value from the given time. Because times may be NaN, +// prefer using this to manual canonicalization. +inline Value +TimeValue(ClippedTime time) +{ + return DoubleValue(JS::CanonicalizeNaN(time.toDouble())); +} + +// Create a new Date object whose [[DateValue]] internal slot contains the +// clipped |time|. (Users who must represent times outside that range must use +// another representation.) +extern JS_PUBLIC_API(JSObject*) +NewDateObject(JSContext* cx, ClippedTime time); + +// Year is a year, month is 0-11, day is 1-based. The return value is a number +// of milliseconds since the epoch. +// +// Consistent with the MakeDate algorithm defined in ECMAScript, this value is +// *not* clipped! Use JS::TimeClip if you need a clipped date. +JS_PUBLIC_API(double) +MakeDate(double year, unsigned month, unsigned day); + +// Takes an integer number of milliseconds since the epoch and returns the +// year. Can return NaN, and will do so if NaN is passed in. +JS_PUBLIC_API(double) +YearFromTime(double time); + +// Takes an integer number of milliseconds since the epoch and returns the +// month (0-11). Can return NaN, and will do so if NaN is passed in. +JS_PUBLIC_API(double) +MonthFromTime(double time); + +// Takes an integer number of milliseconds since the epoch and returns the +// day (1-based). Can return NaN, and will do so if NaN is passed in. +JS_PUBLIC_API(double) +DayFromTime(double time); + +// Takes an integer year and returns the number of days from epoch to the given +// year. +// NOTE: The calculation performed by this function is literally that given in +// the ECMAScript specification. Nonfinite years, years containing fractional +// components, and years outside ECMAScript's date range are not handled with +// any particular intelligence. Garbage in, garbage out. +JS_PUBLIC_API(double) +DayFromYear(double year); + +// Takes an integer number of milliseconds since the epoch and an integer year, +// returns the number of days in that year. If |time| is nonfinite, returns NaN. +// Otherwise |time| *must* correspond to a time within the valid year |year|. +// This should usually be ensured by computing |year| as |JS::DayFromYear(time)|. +JS_PUBLIC_API(double) +DayWithinYear(double time, double year); + +} // namespace JS + +#endif /* js_Date_h */ -- cgit v1.2.3