Line data Source code
1 : // Copyright 2012 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_DATE_H_
6 : #define V8_DATE_H_
7 :
8 : #include "src/base/timezone-cache.h"
9 : #include "src/globals.h"
10 : #include "src/objects/smi.h"
11 :
12 : namespace v8 {
13 : namespace internal {
14 :
15 : class DateCache {
16 : public:
17 : static const int kMsPerMin = 60 * 1000;
18 : static const int kSecPerDay = 24 * 60 * 60;
19 : static const int64_t kMsPerDay = kSecPerDay * 1000;
20 : static const int64_t kMsPerMonth = kMsPerDay * 30;
21 :
22 : // The largest time that can be passed to OS date-time library functions.
23 : static const int kMaxEpochTimeInSec = kMaxInt;
24 : static const int64_t kMaxEpochTimeInMs =
25 : static_cast<int64_t>(kMaxInt) * 1000;
26 :
27 : // The largest time that can be stored in JSDate.
28 : static const int64_t kMaxTimeInMs =
29 : static_cast<int64_t>(864000000) * 10000000;
30 :
31 : // Conservative upper bound on time that can be stored in JSDate
32 : // before UTC conversion.
33 : static const int64_t kMaxTimeBeforeUTCInMs = kMaxTimeInMs + kMsPerMonth;
34 :
35 : // Sentinel that denotes an invalid local offset.
36 : static const int kInvalidLocalOffsetInMs = kMaxInt;
37 : // Sentinel that denotes an invalid cache stamp.
38 : // It is an invariant of DateCache that cache stamp is non-negative.
39 : static const int kInvalidStamp = -1;
40 :
41 : DateCache();
42 :
43 62873 : virtual ~DateCache() {
44 62873 : delete tz_cache_;
45 62873 : tz_cache_ = nullptr;
46 62868 : }
47 :
48 :
49 : // Clears cached timezone information and increments the cache stamp.
50 : void ResetDateCache();
51 :
52 :
53 : // Computes floor(time_ms / kMsPerDay).
54 : static int DaysFromTime(int64_t time_ms) {
55 93950 : if (time_ms < 0) time_ms -= (kMsPerDay - 1);
56 93950 : return static_cast<int>(time_ms / kMsPerDay);
57 : }
58 :
59 :
60 : // Computes modulo(time_ms, kMsPerDay) given that
61 : // days = floor(time_ms / kMsPerDay).
62 : static int TimeInDay(int64_t time_ms, int days) {
63 76931 : return static_cast<int>(time_ms - days * kMsPerDay);
64 : }
65 :
66 : // ECMA 262 - ES#sec-timeclip TimeClip (time)
67 : static double TimeClip(double time);
68 :
69 : // Given the number of days since the epoch, computes the weekday.
70 : // ECMA 262 - 15.9.1.6.
71 : int Weekday(int days) {
72 144236 : int result = (days + 4) % 7;
73 144236 : return result >= 0 ? result : result + 7;
74 : }
75 :
76 :
77 : bool IsLeap(int year) {
78 16812 : return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
79 : }
80 :
81 : // ECMA 262 - ES#sec-local-time-zone-adjustment
82 : int LocalOffsetInMs(int64_t time, bool is_utc) {
83 122071 : return GetLocalOffsetFromOS(time, is_utc);
84 : }
85 :
86 :
87 53361 : const char* LocalTimezone(int64_t time_ms) {
88 53361 : if (time_ms < 0 || time_ms > kMaxEpochTimeInMs) {
89 16812 : time_ms = EquivalentTime(time_ms);
90 : }
91 53361 : bool is_dst = DaylightSavingsOffsetInMs(time_ms) != 0;
92 53361 : const char** name = is_dst ? &dst_tz_name_ : &tz_name_;
93 53361 : if (*name == nullptr) {
94 120 : *name = tz_cache_->LocalTimezone(static_cast<double>(time_ms));
95 : }
96 53361 : return *name;
97 : }
98 :
99 : // ECMA 262 - 15.9.5.26
100 : int TimezoneOffset(int64_t time_ms) {
101 : int64_t local_ms = ToLocal(time_ms);
102 53487 : return static_cast<int>((time_ms - local_ms) / kMsPerMin);
103 : }
104 :
105 : // ECMA 262 - ES#sec-localtime-t
106 : // LocalTime(t) = t + LocalTZA(t, true)
107 : int64_t ToLocal(int64_t time_ms) {
108 119037 : return time_ms + LocalOffsetInMs(time_ms, true);
109 : }
110 :
111 : // ECMA 262 - ES#sec-utc-t
112 : // UTC(t) = t - LocalTZA(t, false)
113 : int64_t ToUTC(int64_t time_ms) {
114 3034 : return time_ms - LocalOffsetInMs(time_ms, false);
115 : }
116 :
117 :
118 : // Computes a time equivalent to the given time according
119 : // to ECMA 262 - 15.9.1.9.
120 : // The issue here is that some library calls don't work right for dates
121 : // that cannot be represented using a non-negative signed 32 bit integer
122 : // (measured in whole seconds based on the 1970 epoch).
123 : // We solve this by mapping the time to a year with same leap-year-ness
124 : // and same starting day for the year. The ECMAscript specification says
125 : // we must do this, but for compatibility with other browsers, we use
126 : // the actual year if it is in the range 1970..2037
127 16812 : int64_t EquivalentTime(int64_t time_ms) {
128 : int days = DaysFromTime(time_ms);
129 16812 : int time_within_day_ms = static_cast<int>(time_ms - days * kMsPerDay);
130 : int year, month, day;
131 16812 : YearMonthDayFromDays(days, &year, &month, &day);
132 16812 : int new_days = DaysFromYearMonth(EquivalentYear(year), month) + day - 1;
133 16812 : return static_cast<int64_t>(new_days) * kMsPerDay + time_within_day_ms;
134 : }
135 :
136 : // Returns an equivalent year in the range [2008-2035] matching
137 : // - leap year,
138 : // - week day of first day.
139 : // ECMA 262 - 15.9.1.9.
140 16812 : int EquivalentYear(int year) {
141 16812 : int week_day = Weekday(DaysFromYearMonth(year, 0));
142 16812 : int recent_year = (IsLeap(year) ? 1956 : 1967) + (week_day * 12) % 28;
143 : // Find the year in the range 2008..2037 that is equivalent mod 28.
144 : // Add 3*28 to give a positive argument to the modulus operator.
145 16812 : return 2008 + (recent_year + 3 * 28 - 2008) % 28;
146 : }
147 :
148 : // Given the number of days since the epoch, computes
149 : // the corresponding year, month, and day.
150 : void YearMonthDayFromDays(int days, int* year, int* month, int* day);
151 :
152 : // Computes the number of days since the epoch for
153 : // the first day of the given month in the given year.
154 : int DaysFromYearMonth(int year, int month);
155 :
156 : // Breaks down the time value.
157 : void BreakDownTime(int64_t time_ms, int* year, int* month, int* day,
158 : int* weekday, int* hour, int* min, int* sec, int* ms);
159 :
160 : // Cache stamp is used for invalidating caches in JSDate.
161 : // We increment the stamp each time when the timezone information changes.
162 : // JSDate objects perform stamp check and invalidate their caches if
163 : // their saved stamp is not equal to the current stamp.
164 : Smi stamp() { return stamp_; }
165 : void* stamp_address() { return &stamp_; }
166 :
167 : // These functions are virtual so that we can override them when testing.
168 19290 : virtual int GetDaylightSavingsOffsetFromOS(int64_t time_sec) {
169 19290 : double time_ms = static_cast<double>(time_sec * 1000);
170 19290 : return static_cast<int>(tz_cache_->DaylightSavingsOffset(time_ms));
171 : }
172 :
173 : virtual int GetLocalOffsetFromOS(int64_t time_ms, bool is_utc);
174 :
175 : private:
176 : // The implementation relies on the fact that no time zones have
177 : // more than one daylight savings offset change per 19 days.
178 : // In Egypt in 2010 they decided to suspend DST during Ramadan. This
179 : // led to a short interval where DST is in effect from September 10 to
180 : // September 30.
181 : static const int kDefaultDSTDeltaInSec = 19 * kSecPerDay;
182 :
183 : // Size of the Daylight Savings Time cache.
184 : static const int kDSTSize = 32;
185 :
186 : // Daylight Savings Time segment stores a segment of time where
187 : // daylight savings offset does not change.
188 : struct DST {
189 : int start_sec;
190 : int end_sec;
191 : int offset_ms;
192 : int last_used;
193 : };
194 :
195 : // Computes the daylight savings offset for the given time.
196 : // ECMA 262 - 15.9.1.8
197 : int DaylightSavingsOffsetInMs(int64_t time_ms);
198 :
199 : // Sets the before_ and the after_ segments from the DST cache such that
200 : // the before_ segment starts earlier than the given time and
201 : // the after_ segment start later than the given time.
202 : // Both segments might be invalid.
203 : // The last_used counters of the before_ and after_ are updated.
204 : void ProbeDST(int time_sec);
205 :
206 : // Finds the least recently used segment from the DST cache that is not
207 : // equal to the given 'skip' segment.
208 : DST* LeastRecentlyUsedDST(DST* skip);
209 :
210 : // Extends the after_ segment with the given point or resets it
211 : // if it starts later than the given time + kDefaultDSTDeltaInSec.
212 : inline void ExtendTheAfterSegment(int time_sec, int offset_ms);
213 :
214 : // Makes the given segment invalid.
215 : inline void ClearSegment(DST* segment);
216 :
217 : bool InvalidSegment(DST* segment) {
218 : return segment->start_sec > segment->end_sec;
219 : }
220 :
221 : Smi stamp_;
222 :
223 : // Daylight Saving Time cache.
224 : DST dst_[kDSTSize];
225 : int dst_usage_counter_;
226 : DST* before_;
227 : DST* after_;
228 :
229 : int local_offset_ms_;
230 :
231 : // Year/Month/Day cache.
232 : bool ymd_valid_;
233 : int ymd_days_;
234 : int ymd_year_;
235 : int ymd_month_;
236 : int ymd_day_;
237 :
238 : // Timezone name cache
239 : const char* tz_name_;
240 : const char* dst_tz_name_;
241 :
242 : base::TimezoneCache* tz_cache_;
243 : };
244 :
245 : } // namespace internal
246 : } // namespace v8
247 :
248 : #endif // V8_DATE_H_
|
