зеркало из https://github.com/mozilla/gecko-dev.git
139 строки
4.7 KiB
C++
139 строки
4.7 KiB
C++
/* -*- 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 {
|
||
|
||
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<double>()) {}
|
||
|
||
// 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<double>());
|
||
|
||
// 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);
|
||
|
||
} // namespace JS
|
||
|
||
#endif /* js_Date_h */
|