blob: 1d2bd407cd283c1f4f7fef4b5945014a338cbe03 [file] [log] [blame]
// 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.
#include "src/date.h"
#include "src/base/overflowing-math.h"
#include "src/conversions.h"
#include "src/objects-inl.h"
#ifdef V8_INTL_SUPPORT
#include "src/objects/intl-objects.h"
#endif
namespace v8 {
namespace internal {
static const int kDaysIn4Years = 4 * 365 + 1;
static const int kDaysIn100Years = 25 * kDaysIn4Years - 1;
static const int kDaysIn400Years = 4 * kDaysIn100Years + 1;
static const int kDays1970to2000 = 30 * 365 + 7;
static const int kDaysOffset = 1000 * kDaysIn400Years + 5 * kDaysIn400Years -
kDays1970to2000;
static const int kYearsOffset = 400000;
static const char kDaysInMonths[] =
{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
DateCache::DateCache()
: stamp_(kNullAddress),
tz_cache_(
#ifdef V8_INTL_SUPPORT
Intl::CreateTimeZoneCache()
#else
base::OS::CreateTimezoneCache()
#endif
) {
ResetDateCache();
}
void DateCache::ResetDateCache() {
if (stamp_->value() >= Smi::kMaxValue) {
stamp_ = Smi::zero();
} else {
stamp_ = Smi::FromInt(stamp_->value() + 1);
}
DCHECK(stamp_ != Smi::FromInt(kInvalidStamp));
for (int i = 0; i < kDSTSize; ++i) {
ClearSegment(&dst_[i]);
}
dst_usage_counter_ = 0;
before_ = &dst_[0];
after_ = &dst_[1];
ymd_valid_ = false;
#ifdef V8_INTL_SUPPORT
if (!FLAG_icu_timezone_data) {
#endif
local_offset_ms_ = kInvalidLocalOffsetInMs;
#ifdef V8_INTL_SUPPORT
}
#endif
tz_cache_->Clear();
tz_name_ = nullptr;
dst_tz_name_ = nullptr;
}
// ECMA 262 - ES#sec-timeclip TimeClip (time)
double DateCache::TimeClip(double time) {
if (-kMaxTimeInMs <= time && time <= kMaxTimeInMs) {
return DoubleToInteger(time) + 0.0;
}
return std::numeric_limits<double>::quiet_NaN();
}
void DateCache::ClearSegment(DST* segment) {
segment->start_sec = kMaxEpochTimeInSec;
segment->end_sec = -kMaxEpochTimeInSec;
segment->offset_ms = 0;
segment->last_used = 0;
}
void DateCache::YearMonthDayFromDays(
int days, int* year, int* month, int* day) {
if (ymd_valid_) {
// Check conservatively if the given 'days' has
// the same year and month as the cached 'days'.
int new_day = ymd_day_ + (days - ymd_days_);
if (new_day >= 1 && new_day <= 28) {
ymd_day_ = new_day;
ymd_days_ = days;
*year = ymd_year_;
*month = ymd_month_;
*day = new_day;
return;
}
}
int save_days = days;
days += kDaysOffset;
*year = 400 * (days / kDaysIn400Years) - kYearsOffset;
days %= kDaysIn400Years;
DCHECK_EQ(save_days, DaysFromYearMonth(*year, 0) + days);
days--;
int yd1 = days / kDaysIn100Years;
days %= kDaysIn100Years;
*year += 100 * yd1;
days++;
int yd2 = days / kDaysIn4Years;
days %= kDaysIn4Years;
*year += 4 * yd2;
days--;
int yd3 = days / 365;
days %= 365;
*year += yd3;
bool is_leap = (!yd1 || yd2) && !yd3;
DCHECK_GE(days, -1);
DCHECK(is_leap || (days >= 0));
DCHECK((days < 365) || (is_leap && (days < 366)));
DCHECK(is_leap == ((*year % 4 == 0) && (*year % 100 || (*year % 400 == 0))));
DCHECK(is_leap || ((DaysFromYearMonth(*year, 0) + days) == save_days));
DCHECK(!is_leap || ((DaysFromYearMonth(*year, 0) + days + 1) == save_days));
days += is_leap;
// Check if the date is after February.
if (days >= 31 + 28 + BoolToInt(is_leap)) {
days -= 31 + 28 + BoolToInt(is_leap);
// Find the date starting from March.
for (int i = 2; i < 12; i++) {
if (days < kDaysInMonths[i]) {
*month = i;
*day = days + 1;
break;
}
days -= kDaysInMonths[i];
}
} else {
// Check January and February.
if (days < 31) {
*month = 0;
*day = days + 1;
} else {
*month = 1;
*day = days - 31 + 1;
}
}
DCHECK(DaysFromYearMonth(*year, *month) + *day - 1 == save_days);
ymd_valid_ = true;
ymd_year_ = *year;
ymd_month_ = *month;
ymd_day_ = *day;
ymd_days_ = save_days;
}
int DateCache::DaysFromYearMonth(int year, int month) {
static const int day_from_month[] = {0, 31, 59, 90, 120, 151,
181, 212, 243, 273, 304, 334};
static const int day_from_month_leap[] = {0, 31, 60, 91, 121, 152,
182, 213, 244, 274, 305, 335};
year += month / 12;
month %= 12;
if (month < 0) {
year--;
month += 12;
}
DCHECK_GE(month, 0);
DCHECK_LT(month, 12);
// year_delta is an arbitrary number such that:
// a) year_delta = -1 (mod 400)
// b) year + year_delta > 0 for years in the range defined by
// ECMA 262 - 15.9.1.1, i.e. upto 100,000,000 days on either side of
// Jan 1 1970. This is required so that we don't run into integer
// division of negative numbers.
// c) there shouldn't be an overflow for 32-bit integers in the following
// operations.
static const int year_delta = 399999;
static const int base_day = 365 * (1970 + year_delta) +
(1970 + year_delta) / 4 -
(1970 + year_delta) / 100 +
(1970 + year_delta) / 400;
int year1 = year + year_delta;
int day_from_year = 365 * year1 +
year1 / 4 -
year1 / 100 +
year1 / 400 -
base_day;
if ((year % 4 != 0) || (year % 100 == 0 && year % 400 != 0)) {
return day_from_year + day_from_month[month];
}
return day_from_year + day_from_month_leap[month];
}
void DateCache::BreakDownTime(int64_t time_ms, int* year, int* month, int* day,
int* weekday, int* hour, int* min, int* sec,
int* ms) {
int const days = DaysFromTime(time_ms);
int const time_in_day_ms = TimeInDay(time_ms, days);
YearMonthDayFromDays(days, year, month, day);
*weekday = Weekday(days);
*hour = time_in_day_ms / (60 * 60 * 1000);
*min = (time_in_day_ms / (60 * 1000)) % 60;
*sec = (time_in_day_ms / 1000) % 60;
*ms = time_in_day_ms % 1000;
}
// Implements LocalTimeZonedjustment(t, isUTC)
// ECMA 262 - ES#sec-local-time-zone-adjustment
int DateCache::GetLocalOffsetFromOS(int64_t time_ms, bool is_utc) {
double offset;
#ifdef V8_INTL_SUPPORT
if (FLAG_icu_timezone_data) {
offset = tz_cache_->LocalTimeOffset(static_cast<double>(time_ms), is_utc);
} else {
#endif
// When ICU timezone data is not used, we need to compute the timezone
// offset for a given local time.
//
// The following shows that using DST for (t - LocalTZA - hour) produces
// correct conversion where LocalTZA is the timezone offset in winter (no
// DST) and the timezone offset is assumed to have no historical change.
// Note that it does not work for the past and the future if LocalTZA (no
// DST) is different from the current LocalTZA (no DST). For instance,
// this will break for Europe/Moscow in 2012 ~ 2013 because LocalTZA was
// 4h instead of the current 3h (as of 2018).
//
// Consider transition to DST at local time L1.
// Let L0 = L1 - hour, L2 = L1 + hour,
// U1 = UTC time that corresponds to L1,
// U0 = U1 - hour.
// Transitioning to DST moves local clock one hour forward L1 => L2, so
// U0 = UTC time that corresponds to L0 = L0 - LocalTZA,
// U1 = UTC time that corresponds to L1 = L1 - LocalTZA,
// U1 = UTC time that corresponds to L2 = L2 - LocalTZA - hour.
// Note that DST(U0 - hour) = 0, DST(U0) = 0, DST(U1) = 1.
// U0 = L0 - LocalTZA - DST(L0 - LocalTZA - hour),
// U1 = L1 - LocalTZA - DST(L1 - LocalTZA - hour),
// U1 = L2 - LocalTZA - DST(L2 - LocalTZA - hour).
//
// Consider transition from DST at local time L1.
// Let L0 = L1 - hour,
// U1 = UTC time that corresponds to L1,
// U0 = U1 - hour, U2 = U1 + hour.
// Transitioning from DST moves local clock one hour back L1 => L0, so
// U0 = UTC time that corresponds to L0 (before transition)
// = L0 - LocalTZA - hour.
// U1 = UTC time that corresponds to L0 (after transition)
// = L0 - LocalTZA = L1 - LocalTZA - hour
// U2 = UTC time that corresponds to L1 = L1 - LocalTZA.
// Note that DST(U0) = 1, DST(U1) = 0, DST(U2) = 0.
// U0 = L0 - LocalTZA - DST(L0 - LocalTZA - hour) = L0 - LocalTZA - DST(U0).
// U2 = L1 - LocalTZA - DST(L1 - LocalTZA - hour) = L1 - LocalTZA - DST(U1).
// It is impossible to get U1 from local time.
if (local_offset_ms_ == kInvalidLocalOffsetInMs) {
// This gets the constant LocalTZA (arguments are ignored).
local_offset_ms_ =
tz_cache_->LocalTimeOffset(static_cast<double>(time_ms), is_utc);
}
offset = local_offset_ms_;
if (!is_utc) {
const int kMsPerHour = 3600 * 1000;
time_ms -= (offset + kMsPerHour);
}
offset += DaylightSavingsOffsetInMs(time_ms);
#ifdef V8_INTL_SUPPORT
}
#endif
DCHECK_LT(offset, kInvalidLocalOffsetInMs);
return static_cast<int>(offset);
}
void DateCache::ExtendTheAfterSegment(int time_sec, int offset_ms) {
if (after_->offset_ms == offset_ms &&
after_->start_sec - kDefaultDSTDeltaInSec <= time_sec &&
time_sec <= after_->end_sec) {
// Extend the after_ segment.
after_->start_sec = time_sec;
} else {
// The after_ segment is either invalid or starts too late.
if (!InvalidSegment(after_)) {
// If the after_ segment is valid, replace it with a new segment.
after_ = LeastRecentlyUsedDST(before_);
}
after_->start_sec = time_sec;
after_->end_sec = time_sec;
after_->offset_ms = offset_ms;
after_->last_used = ++dst_usage_counter_;
}
}
int DateCache::DaylightSavingsOffsetInMs(int64_t time_ms) {
int time_sec = (time_ms >= 0 && time_ms <= kMaxEpochTimeInMs)
? static_cast<int>(time_ms / 1000)
: static_cast<int>(EquivalentTime(time_ms) / 1000);
// Invalidate cache if the usage counter is close to overflow.
// Note that dst_usage_counter is incremented less than ten times
// in this function.
if (dst_usage_counter_ >= kMaxInt - 10) {
dst_usage_counter_ = 0;
for (int i = 0; i < kDSTSize; ++i) {
ClearSegment(&dst_[i]);
}
}
// Optimistic fast check.
if (before_->start_sec <= time_sec &&
time_sec <= before_->end_sec) {
// Cache hit.
before_->last_used = ++dst_usage_counter_;
return before_->offset_ms;
}
ProbeDST(time_sec);
DCHECK(InvalidSegment(before_) || before_->start_sec <= time_sec);
DCHECK(InvalidSegment(after_) || time_sec < after_->start_sec);
if (InvalidSegment(before_)) {
// Cache miss.
before_->start_sec = time_sec;
before_->end_sec = time_sec;
before_->offset_ms = GetDaylightSavingsOffsetFromOS(time_sec);
before_->last_used = ++dst_usage_counter_;
return before_->offset_ms;
}
if (time_sec <= before_->end_sec) {
// Cache hit.
before_->last_used = ++dst_usage_counter_;
return before_->offset_ms;
}
if (time_sec - kDefaultDSTDeltaInSec > before_->end_sec) {
// If the before_ segment ends too early, then just
// query for the offset of the time_sec
int offset_ms = GetDaylightSavingsOffsetFromOS(time_sec);
ExtendTheAfterSegment(time_sec, offset_ms);
// This swap helps the optimistic fast check in subsequent invocations.
DST* temp = before_;
before_ = after_;
after_ = temp;
return offset_ms;
}
// Now the time_sec is between
// before_->end_sec and before_->end_sec + default DST delta.
// Update the usage counter of before_ since it is going to be used.
before_->last_used = ++dst_usage_counter_;
// Check if after_ segment is invalid or starts too late.
// Note that start_sec of invalid segments is kMaxEpochTimeInSec.
int new_after_start_sec =
before_->end_sec < kMaxEpochTimeInSec - kDefaultDSTDeltaInSec
? before_->end_sec + kDefaultDSTDeltaInSec
: kMaxEpochTimeInSec;
if (new_after_start_sec <= after_->start_sec) {
int new_offset_ms = GetDaylightSavingsOffsetFromOS(new_after_start_sec);
ExtendTheAfterSegment(new_after_start_sec, new_offset_ms);
} else {
DCHECK(!InvalidSegment(after_));
// Update the usage counter of after_ since it is going to be used.
after_->last_used = ++dst_usage_counter_;
}
// Now the time_sec is between before_->end_sec and after_->start_sec.
// Only one daylight savings offset change can occur in this interval.
if (before_->offset_ms == after_->offset_ms) {
// Merge two segments if they have the same offset.
before_->end_sec = after_->end_sec;
ClearSegment(after_);
return before_->offset_ms;
}
// Binary search for daylight savings offset change point,
// but give up if we don't find it in five iterations.
for (int i = 4; i >= 0; --i) {
int delta = after_->start_sec - before_->end_sec;
int middle_sec = (i == 0) ? time_sec : before_->end_sec + delta / 2;
int offset_ms = GetDaylightSavingsOffsetFromOS(middle_sec);
if (before_->offset_ms == offset_ms) {
before_->end_sec = middle_sec;
if (time_sec <= before_->end_sec) {
return offset_ms;
}
} else {
DCHECK(after_->offset_ms == offset_ms);
after_->start_sec = middle_sec;
if (time_sec >= after_->start_sec) {
// This swap helps the optimistic fast check in subsequent invocations.
DST* temp = before_;
before_ = after_;
after_ = temp;
return offset_ms;
}
}
}
return 0;
}
void DateCache::ProbeDST(int time_sec) {
DST* before = nullptr;
DST* after = nullptr;
DCHECK(before_ != after_);
for (int i = 0; i < kDSTSize; ++i) {
if (dst_[i].start_sec <= time_sec) {
if (before == nullptr || before->start_sec < dst_[i].start_sec) {
before = &dst_[i];
}
} else if (time_sec < dst_[i].end_sec) {
if (after == nullptr || after->end_sec > dst_[i].end_sec) {
after = &dst_[i];
}
}
}
// If before or after segments were not found,
// then set them to any invalid segment.
if (before == nullptr) {
before = InvalidSegment(before_) ? before_ : LeastRecentlyUsedDST(after);
}
if (after == nullptr) {
after = InvalidSegment(after_) && before != after_
? after_ : LeastRecentlyUsedDST(before);
}
DCHECK_NOT_NULL(before);
DCHECK_NOT_NULL(after);
DCHECK(before != after);
DCHECK(InvalidSegment(before) || before->start_sec <= time_sec);
DCHECK(InvalidSegment(after) || time_sec < after->start_sec);
DCHECK(InvalidSegment(before) || InvalidSegment(after) ||
before->end_sec < after->start_sec);
before_ = before;
after_ = after;
}
DateCache::DST* DateCache::LeastRecentlyUsedDST(DST* skip) {
DST* result = nullptr;
for (int i = 0; i < kDSTSize; ++i) {
if (&dst_[i] == skip) continue;
if (result == nullptr || result->last_used > dst_[i].last_used) {
result = &dst_[i];
}
}
ClearSegment(result);
return result;
}
} // namespace internal
} // namespace v8