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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_DATE_DATE_H_
#define V8_DATE_DATE_H_
#include "src/base/small-vector.h"
#include "src/base/timezone-cache.h"
#include "src/common/globals.h"
#include "src/objects/smi.h"
namespace v8 {
namespace internal {
class V8_EXPORT_PRIVATE DateCache {
public:
static const int kMsPerMin = 60 * 1000;
static const int kSecPerDay = 24 * 60 * 60;
static const int64_t kMsPerDay = kSecPerDay * 1000;
static const int64_t kMsPerMonth = kMsPerDay * 30;
// The largest time that can be passed to OS date-time library functions.
static const int kMaxEpochTimeInSec = kMaxInt;
static const int64_t kMaxEpochTimeInMs = static_cast<int64_t>(kMaxInt) * 1000;
// The largest time that can be stored in JSDate.
static const int64_t kMaxTimeInMs =
static_cast<int64_t>(864000000) * 10000000;
// Conservative upper bound on time that can be stored in JSDate
// before UTC conversion.
static const int64_t kMaxTimeBeforeUTCInMs = kMaxTimeInMs + kMsPerMonth;
// Sentinel that denotes an invalid local offset.
static const int kInvalidLocalOffsetInMs = kMaxInt;
// Sentinel that denotes an invalid cache stamp.
// It is an invariant of DateCache that cache stamp is non-negative.
static const int kInvalidStamp = -1;
DateCache();
virtual ~DateCache() {
delete tz_cache_;
tz_cache_ = nullptr;
}
// Clears cached timezone information and increments the cache stamp.
void ResetDateCache(
base::TimezoneCache::TimeZoneDetection time_zone_detection);
// Computes floor(time_ms / kMsPerDay).
static int DaysFromTime(int64_t time_ms) {
if (time_ms < 0) time_ms -= (kMsPerDay - 1);
return static_cast<int>(time_ms / kMsPerDay);
}
// Computes modulo(time_ms, kMsPerDay) given that
// days = floor(time_ms / kMsPerDay).
static int TimeInDay(int64_t time_ms, int days) {
return static_cast<int>(time_ms - days * kMsPerDay);
}
// ECMA 262 - ES#sec-timeclip TimeClip (time)
static double TimeClip(double time);
// Given the number of days since the epoch, computes the weekday.
// ECMA 262 - 15.9.1.6.
int Weekday(int days) {
int result = (days + 4) % 7;
return result >= 0 ? result : result + 7;
}
bool IsLeap(int year) {
return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}
// ECMA 262 - ES#sec-local-time-zone-adjustment
int LocalOffsetInMs(int64_t time, bool is_utc) {
return GetLocalOffsetFromOS(time, is_utc);
}
const char* LocalTimezone(int64_t time_ms) {
if (time_ms < 0 || time_ms > kMaxEpochTimeInMs) {
time_ms = EquivalentTime(time_ms);
}
bool is_dst = DaylightSavingsOffsetInMs(time_ms) != 0;
const char** name = is_dst ? &dst_tz_name_ : &tz_name_;
if (*name == nullptr) {
*name = tz_cache_->LocalTimezone(static_cast<double>(time_ms));
}
return *name;
}
// ECMA 262 - 15.9.5.26
int TimezoneOffset(int64_t time_ms) {
int64_t local_ms = ToLocal(time_ms);
return static_cast<int>((time_ms - local_ms) / kMsPerMin);
}
// ECMA 262 - ES#sec-localtime-t
// LocalTime(t) = t + LocalTZA(t, true)
int64_t ToLocal(int64_t time_ms) {
return time_ms + LocalOffsetInMs(time_ms, true);
}
// ECMA 262 - ES#sec-utc-t
// UTC(t) = t - LocalTZA(t, false)
int64_t ToUTC(int64_t time_ms) {
return time_ms - LocalOffsetInMs(time_ms, false);
}
// Computes a time equivalent to the given time according
// to ECMA 262 - 15.9.1.9.
// The issue here is that some library calls don't work right for dates
// that cannot be represented using a non-negative signed 32 bit integer
// (measured in whole seconds based on the 1970 epoch).
// We solve this by mapping the time to a year with same leap-year-ness
// and same starting day for the year. The ECMAscript specification says
// we must do this, but for compatibility with other browsers, we use
// the actual year if it is in the range 1970..2037
int64_t EquivalentTime(int64_t time_ms) {
int days = DaysFromTime(time_ms);
int time_within_day_ms = static_cast<int>(time_ms - days * kMsPerDay);
int year, month, day;
YearMonthDayFromDays(days, &year, &month, &day);
int new_days = DaysFromYearMonth(EquivalentYear(year), month) + day - 1;
return static_cast<int64_t>(new_days) * kMsPerDay + time_within_day_ms;
}
// Returns an equivalent year in the range [2008-2035] matching
// - leap year,
// - week day of first day.
// ECMA 262 - 15.9.1.9.
int EquivalentYear(int year) {
int week_day = Weekday(DaysFromYearMonth(year, 0));
int recent_year = (IsLeap(year) ? 1956 : 1967) + (week_day * 12) % 28;
// Find the year in the range 2008..2037 that is equivalent mod 28.
// Add 3*28 to give a positive argument to the modulus operator.
return 2008 + (recent_year + 3 * 28 - 2008) % 28;
}
// Given the number of days since the epoch, computes
// the corresponding year, month, and day.
void YearMonthDayFromDays(int days, int* year, int* month, int* day);
// Computes the number of days since the epoch for
// the first day of the given month in the given year.
int DaysFromYearMonth(int year, int month);
// Breaks down the time value.
void BreakDownTime(int64_t time_ms, int* year, int* month, int* day,
int* weekday, int* hour, int* min, int* sec, int* ms);
// Cache stamp is used for invalidating caches in JSDate.
// We increment the stamp each time when the timezone information changes.
// JSDate objects perform stamp check and invalidate their caches if
// their saved stamp is not equal to the current stamp.
Tagged<Smi> stamp() { return stamp_; }
void* stamp_address() { return &stamp_; }
// These functions are virtual so that we can override them when testing.
virtual int GetDaylightSavingsOffsetFromOS(int64_t time_sec) {
double time_ms = static_cast<double>(time_sec * 1000);
return static_cast<int>(tz_cache_->DaylightSavingsOffset(time_ms));
}
virtual int GetLocalOffsetFromOS(int64_t time_ms, bool is_utc);
private:
// The implementation relies on the fact that no time zones have
// more than one daylight savings offset change per 19 days.
// In Egypt in 2010 they decided to suspend DST during Ramadan. This
// led to a short interval where DST is in effect from September 10 to
// September 30.
static const int kDefaultDSTDeltaInSec = 19 * kSecPerDay;
// Size of the Daylight Savings Time cache.
static const int kDSTSize = 32;
// Daylight Savings Time segment stores a segment of time where
// daylight savings offset does not change.
struct DST {
int start_sec;
int end_sec;
int offset_ms;
int last_used;
};
// Computes the daylight savings offset for the given time.
// ECMA 262 - 15.9.1.8
int DaylightSavingsOffsetInMs(int64_t time_ms);
// Sets the before_ and the after_ segments from the DST cache such that
// the before_ segment starts earlier than the given time and
// the after_ segment start later than the given time.
// Both segments might be invalid.
// The last_used counters of the before_ and after_ are updated.
void ProbeDST(int time_sec);
// Finds the least recently used segment from the DST cache that is not
// equal to the given 'skip' segment.
DST* LeastRecentlyUsedDST(DST* skip);
// Extends the after_ segment with the given point or resets it
// if it starts later than the given time + kDefaultDSTDeltaInSec.
inline void ExtendTheAfterSegment(int time_sec, int offset_ms);
// Makes the given segment invalid.
inline void ClearSegment(DST* segment);
bool InvalidSegment(DST* segment) {
return segment->start_sec > segment->end_sec;
}
Tagged<Smi> stamp_;
// Daylight Saving Time cache.
DST dst_[kDSTSize];
int dst_usage_counter_;
DST* before_;
DST* after_;
int local_offset_ms_;
// Year/Month/Day cache.
bool ymd_valid_;
int ymd_days_;
int ymd_year_;
int ymd_month_;
int ymd_day_;
// Timezone name cache
const char* tz_name_;
const char* dst_tz_name_;
base::TimezoneCache* tz_cache_;
};
// Routines shared between Date and Temporal
// ES6 section 20.3.1.14 MakeDate (day, time)
double MakeDate(double day, double time);
// ES6 section 20.3.1.13 MakeDay (year, month, date)
double MakeDay(double year, double month, double date);
// ES6 section 20.3.1.12 MakeTime (hour, min, sec, ms)
double MakeTime(double hour, double min, double sec, double ms);
using DateBuffer = base::SmallVector<char, 128>;
enum class ToDateStringMode {
kLocalDate,
kLocalTime,
kLocalDateAndTime,
kUTCDateAndTime,
kISODateAndTime
};
// ES6 section 20.3.4.41.1 ToDateString(tv)
DateBuffer ToDateString(double time_val, DateCache* date_cache,
ToDateStringMode mode);
double ParseDateTimeString(Isolate* isolate, Handle<String> str);
} // namespace internal
} // namespace v8
#endif // V8_DATE_DATE_H_