1 // Copyright (c) 2012 The Chromium 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 // Time represents an absolute point in coordinated universal time (UTC),
6 // internally represented as microseconds (s/1,000,000) since the Windows epoch
7 // (1601-01-01 00:00:00 UTC). System-dependent clock interface routines are
8 // defined in time_PLATFORM.cc. Note that values for Time may skew and jump
9 // around as the operating system makes adjustments to synchronize (e.g., with
10 // NTP servers). Thus, client code that uses the Time class must account for
11 // this.
12 //
13 // TimeDelta represents a duration of time, internally represented in
14 // microseconds.
15 //
16 // TimeTicks and ThreadTicks represent an abstract time that is most of the time
17 // incrementing, for use in measuring time durations. Internally, they are
18 // represented in microseconds. They cannot be converted to a human-readable
19 // time, but are guaranteed not to decrease (unlike the Time class). Note that
20 // TimeTicks may "stand still" (e.g., if the computer is suspended), and
21 // ThreadTicks will "stand still" whenever the thread has been de-scheduled by
22 // the operating system.
23 //
24 // All time classes are copyable, assignable, and occupy 64-bits per instance.
25 // As a result, prefer passing them by value:
26 // void MyFunction(TimeDelta arg);
27 // If circumstances require, you may also pass by const reference:
28 // void MyFunction(const TimeDelta& arg); // Not preferred.
29 //
30 // Definitions of operator<< are provided to make these types work with
31 // DCHECK_EQ() and other log macros. For human-readable formatting, see
32 // "base/i18n/time_formatting.h".
33 //
34 // So many choices! Which time class should you use? Examples:
35 //
36 // Time: Interpreting the wall-clock time provided by a remote system.
37 // Detecting whether cached resources have expired. Providing the
38 // user with a display of the current date and time. Determining
39 // the amount of time between events across re-boots of the
40 // machine.
41 //
42 // TimeTicks: Tracking the amount of time a task runs. Executing delayed
43 // tasks at the right time. Computing presentation timestamps.
44 // Synchronizing audio and video using TimeTicks as a common
45 // reference clock (lip-sync). Measuring network round-trip
46 // latency.
47 //
48 // ThreadTicks: Benchmarking how long the current thread has been doing actual
49 // work.
50
51 #ifndef BASE_TIME_TIME_H_
52 #define BASE_TIME_TIME_H_
53
54 #include <stdint.h>
55 #include <time.h>
56
57 #include <iosfwd>
58 #include <limits>
59
60 #include "base/base_export.h"
61 #include "base/compiler_specific.h"
62 #include "base/logging.h"
63 #include "base/numerics/safe_math.h"
64 #include "build/build_config.h"
65
66 #if defined(OS_FUCHSIA)
67 #include <zircon/types.h>
68 #endif
69
70 #if defined(OS_MACOSX)
71 #include <CoreFoundation/CoreFoundation.h>
72 // Avoid Mac system header macro leak.
73 #undef TYPE_BOOL
74 #endif
75
76 #if defined(OS_ANDROID)
77 #include <jni.h>
78 #endif
79
80 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
81 #include <unistd.h>
82 #include <sys/time.h>
83 #endif
84
85 #if defined(OS_WIN)
86 #include "base/gtest_prod_util.h"
87 #include "base/win/windows_types.h"
88 #endif
89
90 namespace ABI {
91 namespace Windows {
92 namespace Foundation {
93 struct DateTime;
94 } // namespace Foundation
95 } // namespace Windows
96 } // namespace ABI
97
98 namespace base {
99
100 class PlatformThreadHandle;
101 class TimeDelta;
102
103 // The functions in the time_internal namespace are meant to be used only by the
104 // time classes and functions. Please use the math operators defined in the
105 // time classes instead.
106 namespace time_internal {
107
108 // Add or subtract a TimeDelta from |value|. TimeDelta::Min()/Max() are treated
109 // as infinity and will always saturate the return value (infinity math applies
110 // if |value| also is at either limit of its spectrum). The int64_t argument and
111 // return value are in terms of a microsecond timebase.
112 BASE_EXPORT constexpr int64_t SaturatedAdd(int64_t value, TimeDelta delta);
113 BASE_EXPORT constexpr int64_t SaturatedSub(int64_t value, TimeDelta delta);
114
115 } // namespace time_internal
116
117 // TimeDelta ------------------------------------------------------------------
118
119 class BASE_EXPORT TimeDelta {
120 public:
TimeDelta()121 constexpr TimeDelta() : delta_(0) {}
122
123 // Converts units of time to TimeDeltas.
124 // WARNING: Floating point arithmetic is such that FromXXXD(t.InXXXF()) may
125 // not precisely equal |t|. Hence, floating point values should not be used
126 // for storage.
127 static constexpr TimeDelta FromDays(int days);
128 static constexpr TimeDelta FromHours(int hours);
129 static constexpr TimeDelta FromMinutes(int minutes);
130 static constexpr TimeDelta FromSeconds(int64_t secs);
131 static constexpr TimeDelta FromMilliseconds(int64_t ms);
132 static constexpr TimeDelta FromMicroseconds(int64_t us);
133 static constexpr TimeDelta FromNanoseconds(int64_t ns);
134 static constexpr TimeDelta FromSecondsD(double secs);
135 static constexpr TimeDelta FromMillisecondsD(double ms);
136 static constexpr TimeDelta FromMicrosecondsD(double us);
137 static constexpr TimeDelta FromNanosecondsD(double ns);
138 #if defined(OS_WIN)
139 static TimeDelta FromQPCValue(LONGLONG qpc_value);
140 // TODO(crbug.com/989694): Avoid base::TimeDelta factory functions
141 // based on absolute time
142 static TimeDelta FromFileTime(FILETIME ft);
143 static TimeDelta FromWinrtDateTime(ABI::Windows::Foundation::DateTime dt);
144 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
145 static TimeDelta FromTimeSpec(const timespec& ts);
146 #endif
147 #if defined(OS_FUCHSIA)
148 static TimeDelta FromZxDuration(zx_duration_t nanos);
149 #endif
150
151 // Converts an integer value representing TimeDelta to a class. This is used
152 // when deserializing a |TimeDelta| structure, using a value known to be
153 // compatible. It is not provided as a constructor because the integer type
154 // may be unclear from the perspective of a caller.
155 //
156 // DEPRECATED - Do not use in new code. http://crbug.com/634507
FromInternalValue(int64_t delta)157 static constexpr TimeDelta FromInternalValue(int64_t delta) {
158 return TimeDelta(delta);
159 }
160
161 // Returns the maximum time delta, which should be greater than any reasonable
162 // time delta we might compare it to. Adding or subtracting the maximum time
163 // delta to a time or another time delta has an undefined result.
164 static constexpr TimeDelta Max();
165
166 // Returns the minimum time delta, which should be less than than any
167 // reasonable time delta we might compare it to. Adding or subtracting the
168 // minimum time delta to a time or another time delta has an undefined result.
169 static constexpr TimeDelta Min();
170
171 // Returns the internal numeric value of the TimeDelta object. Please don't
172 // use this and do arithmetic on it, as it is more error prone than using the
173 // provided operators.
174 // For serializing, use FromInternalValue to reconstitute.
175 //
176 // DEPRECATED - Do not use in new code. http://crbug.com/634507
ToInternalValue()177 constexpr int64_t ToInternalValue() const { return delta_; }
178
179 // Returns the magnitude (absolute value) of this TimeDelta.
magnitude()180 constexpr TimeDelta magnitude() const {
181 // Some toolchains provide an incomplete C++11 implementation and lack an
182 // int64_t overload for std::abs(). The following is a simple branchless
183 // implementation:
184 const int64_t mask = delta_ >> (sizeof(delta_) * 8 - 1);
185 return TimeDelta((delta_ + mask) ^ mask);
186 }
187
188 // Returns true if the time delta is zero.
is_zero()189 constexpr bool is_zero() const { return delta_ == 0; }
190
191 // Returns true if the time delta is the maximum/minimum time delta.
is_max()192 constexpr bool is_max() const {
193 return delta_ == std::numeric_limits<int64_t>::max();
194 }
is_min()195 constexpr bool is_min() const {
196 return delta_ == std::numeric_limits<int64_t>::min();
197 }
198
199 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
200 struct timespec ToTimeSpec() const;
201 #endif
202 #if defined(OS_FUCHSIA)
203 zx_duration_t ToZxDuration() const;
204 #endif
205 #if defined(OS_WIN)
206 ABI::Windows::Foundation::DateTime ToWinrtDateTime() const;
207 #endif
208
209 // Returns the time delta in some unit. The InXYZF versions return a floating
210 // point value. The InXYZ versions return a truncated value (aka rounded
211 // towards zero, std::trunc() behavior). The InXYZFloored() versions round to
212 // lesser integers (std::floor() behavior). The XYZRoundedUp() versions round
213 // up to greater integers (std::ceil() behavior).
214 // WARNING: Floating point arithmetic is such that FromXXXD(t.InXXXF()) may
215 // not precisely equal |t|. Hence, floating point values should not be used
216 // for storage.
217 int InDays() const;
218 int InDaysFloored() const;
219 int InHours() const;
220 int InMinutes() const;
221 double InSecondsF() const;
222 int64_t InSeconds() const;
223 double InMillisecondsF() const;
224 int64_t InMilliseconds() const;
225 int64_t InMillisecondsRoundedUp() const;
InMicroseconds()226 constexpr int64_t InMicroseconds() const { return delta_; }
227 double InMicrosecondsF() const;
228 int64_t InNanoseconds() const;
229
230 // Computations with other deltas.
231 constexpr TimeDelta operator+(TimeDelta other) const {
232 return TimeDelta(time_internal::SaturatedAdd(delta_, other));
233 }
234 constexpr TimeDelta operator-(TimeDelta other) const {
235 return TimeDelta(time_internal::SaturatedSub(delta_, other));
236 }
237
238 constexpr TimeDelta& operator+=(TimeDelta other) {
239 return *this = (*this + other);
240 }
241 constexpr TimeDelta& operator-=(TimeDelta other) {
242 return *this = (*this - other);
243 }
244 constexpr TimeDelta operator-() const { return TimeDelta(-delta_); }
245
246 // Computations with numeric types.
247 template <typename T>
248 constexpr TimeDelta operator*(T a) const {
249 CheckedNumeric<int64_t> rv(delta_);
250 rv *= a;
251 if (rv.IsValid())
252 return TimeDelta(rv.ValueOrDie());
253 // Matched sign overflows. Mismatched sign underflows.
254 if ((delta_ < 0) ^ (a < 0))
255 return TimeDelta(std::numeric_limits<int64_t>::min());
256 return TimeDelta(std::numeric_limits<int64_t>::max());
257 }
258 template <typename T>
259 constexpr TimeDelta operator/(T a) const {
260 CheckedNumeric<int64_t> rv(delta_);
261 rv /= a;
262 if (rv.IsValid())
263 return TimeDelta(rv.ValueOrDie());
264 // Matched sign overflows. Mismatched sign underflows.
265 // Special case to catch divide by zero.
266 if ((delta_ < 0) ^ (a <= 0))
267 return TimeDelta(std::numeric_limits<int64_t>::min());
268 return TimeDelta(std::numeric_limits<int64_t>::max());
269 }
270 template <typename T>
271 constexpr TimeDelta& operator*=(T a) {
272 return *this = (*this * a);
273 }
274 template <typename T>
275 constexpr TimeDelta& operator/=(T a) {
276 return *this = (*this / a);
277 }
278
279 constexpr int64_t operator/(TimeDelta a) const { return delta_ / a.delta_; }
280
281 constexpr TimeDelta operator%(TimeDelta a) const {
282 return TimeDelta(delta_ % a.delta_);
283 }
284 TimeDelta& operator%=(TimeDelta other) { return *this = (*this % other); }
285
286 // Comparison operators.
287 constexpr bool operator==(TimeDelta other) const {
288 return delta_ == other.delta_;
289 }
290 constexpr bool operator!=(TimeDelta other) const {
291 return delta_ != other.delta_;
292 }
293 constexpr bool operator<(TimeDelta other) const {
294 return delta_ < other.delta_;
295 }
296 constexpr bool operator<=(TimeDelta other) const {
297 return delta_ <= other.delta_;
298 }
299 constexpr bool operator>(TimeDelta other) const {
300 return delta_ > other.delta_;
301 }
302 constexpr bool operator>=(TimeDelta other) const {
303 return delta_ >= other.delta_;
304 }
305
306 private:
307 friend constexpr int64_t time_internal::SaturatedAdd(int64_t value,
308 TimeDelta delta);
309 friend constexpr int64_t time_internal::SaturatedSub(int64_t value,
310 TimeDelta delta);
311
312 // Constructs a delta given the duration in microseconds. This is private
313 // to avoid confusion by callers with an integer constructor. Use
314 // FromSeconds, FromMilliseconds, etc. instead.
TimeDelta(int64_t delta_us)315 constexpr explicit TimeDelta(int64_t delta_us) : delta_(delta_us) {}
316
317 // Private method to build a delta from a double.
318 static constexpr TimeDelta FromDouble(double value);
319
320 // Private method to build a delta from the product of a user-provided value
321 // and a known-positive value.
322 static constexpr TimeDelta FromProduct(int64_t value, int64_t positive_value);
323
324 // Delta in microseconds.
325 int64_t delta_;
326 };
327
328 template <typename T>
329 constexpr TimeDelta operator*(T a, TimeDelta td) {
330 return td * a;
331 }
332
333 // For logging use only.
334 BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeDelta time_delta);
335
336 // Do not reference the time_internal::TimeBase template class directly. Please
337 // use one of the time subclasses instead, and only reference the public
338 // TimeBase members via those classes.
339 namespace time_internal {
340
SaturatedAdd(int64_t value,TimeDelta delta)341 constexpr int64_t SaturatedAdd(int64_t value, TimeDelta delta) {
342 // Treat Min/Max() as +/- infinity (additions involving two infinities are
343 // only valid if signs match).
344 if (delta.is_max()) {
345 CHECK_GT(value, std::numeric_limits<int64_t>::min());
346 return std::numeric_limits<int64_t>::max();
347 } else if (delta.is_min()) {
348 CHECK_LT(value, std::numeric_limits<int64_t>::max());
349 return std::numeric_limits<int64_t>::min();
350 }
351
352 return base::ClampAdd(value, delta.delta_);
353 }
354
SaturatedSub(int64_t value,TimeDelta delta)355 constexpr int64_t SaturatedSub(int64_t value, TimeDelta delta) {
356 // Treat Min/Max() as +/- infinity (subtractions involving two infinities are
357 // only valid if signs are opposite).
358 if (delta.is_max()) {
359 CHECK_LT(value, std::numeric_limits<int64_t>::max());
360 return std::numeric_limits<int64_t>::min();
361 } else if (delta.is_min()) {
362 CHECK_GT(value, std::numeric_limits<int64_t>::min());
363 return std::numeric_limits<int64_t>::max();
364 }
365
366 return base::ClampSub(value, delta.delta_);
367 }
368
369 // TimeBase--------------------------------------------------------------------
370
371 // Provides value storage and comparison/math operations common to all time
372 // classes. Each subclass provides for strong type-checking to ensure
373 // semantically meaningful comparison/math of time values from the same clock
374 // source or timeline.
375 template<class TimeClass>
376 class TimeBase {
377 public:
378 static constexpr int64_t kHoursPerDay = 24;
379 static constexpr int64_t kSecondsPerMinute = 60;
380 static constexpr int64_t kSecondsPerHour = 60 * kSecondsPerMinute;
381 static constexpr int64_t kMillisecondsPerSecond = 1000;
382 static constexpr int64_t kMillisecondsPerDay =
383 kMillisecondsPerSecond * 60 * 60 * kHoursPerDay;
384 static constexpr int64_t kMicrosecondsPerMillisecond = 1000;
385 static constexpr int64_t kMicrosecondsPerSecond =
386 kMicrosecondsPerMillisecond * kMillisecondsPerSecond;
387 static constexpr int64_t kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
388 static constexpr int64_t kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
389 static constexpr int64_t kMicrosecondsPerDay =
390 kMicrosecondsPerHour * kHoursPerDay;
391 static constexpr int64_t kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
392 static constexpr int64_t kNanosecondsPerMicrosecond = 1000;
393 static constexpr int64_t kNanosecondsPerSecond =
394 kNanosecondsPerMicrosecond * kMicrosecondsPerSecond;
395
396 // Returns true if this object has not been initialized.
397 //
398 // Warning: Be careful when writing code that performs math on time values,
399 // since it's possible to produce a valid "zero" result that should not be
400 // interpreted as a "null" value.
is_null()401 constexpr bool is_null() const { return us_ == 0; }
402
403 // Returns true if this object represents the maximum/minimum time.
is_max()404 constexpr bool is_max() const {
405 return us_ == std::numeric_limits<int64_t>::max();
406 }
is_min()407 constexpr bool is_min() const {
408 return us_ == std::numeric_limits<int64_t>::min();
409 }
410
411 // Returns the maximum/minimum times, which should be greater/less than than
412 // any reasonable time with which we might compare it.
Max()413 static constexpr TimeClass Max() {
414 return TimeClass(std::numeric_limits<int64_t>::max());
415 }
416
Min()417 static constexpr TimeClass Min() {
418 return TimeClass(std::numeric_limits<int64_t>::min());
419 }
420
421 // For serializing only. Use FromInternalValue() to reconstitute. Please don't
422 // use this and do arithmetic on it, as it is more error prone than using the
423 // provided operators.
424 //
425 // DEPRECATED - Do not use in new code. For serializing Time values, prefer
426 // Time::ToDeltaSinceWindowsEpoch().InMicroseconds(). http://crbug.com/634507
ToInternalValue()427 constexpr int64_t ToInternalValue() const { return us_; }
428
429 // The amount of time since the origin (or "zero") point. This is a syntactic
430 // convenience to aid in code readability, mainly for debugging/testing use
431 // cases.
432 //
433 // Warning: While the Time subclass has a fixed origin point, the origin for
434 // the other subclasses can vary each time the application is restarted.
since_origin()435 constexpr TimeDelta since_origin() const {
436 return TimeDelta::FromMicroseconds(us_);
437 }
438
439 constexpr TimeClass& operator=(TimeClass other) {
440 us_ = other.us_;
441 return *(static_cast<TimeClass*>(this));
442 }
443
444 // Compute the difference between two times.
445 constexpr TimeDelta operator-(TimeClass other) const {
446 return TimeDelta::FromMicroseconds(us_ - other.us_);
447 }
448
449 // Return a new time modified by some delta.
450 constexpr TimeClass operator+(TimeDelta delta) const {
451 return TimeClass(time_internal::SaturatedAdd(us_, delta));
452 }
453 constexpr TimeClass operator-(TimeDelta delta) const {
454 return TimeClass(time_internal::SaturatedSub(us_, delta));
455 }
456
457 // Modify by some time delta.
458 constexpr TimeClass& operator+=(TimeDelta delta) {
459 return static_cast<TimeClass&>(*this = (*this + delta));
460 }
461 constexpr TimeClass& operator-=(TimeDelta delta) {
462 return static_cast<TimeClass&>(*this = (*this - delta));
463 }
464
465 // Comparison operators
466 constexpr bool operator==(TimeClass other) const { return us_ == other.us_; }
467 constexpr bool operator!=(TimeClass other) const { return us_ != other.us_; }
468 constexpr bool operator<(TimeClass other) const { return us_ < other.us_; }
469 constexpr bool operator<=(TimeClass other) const { return us_ <= other.us_; }
470 constexpr bool operator>(TimeClass other) const { return us_ > other.us_; }
471 constexpr bool operator>=(TimeClass other) const { return us_ >= other.us_; }
472
473 protected:
TimeBase(int64_t us)474 constexpr explicit TimeBase(int64_t us) : us_(us) {}
475
476 // Time value in a microsecond timebase.
477 int64_t us_;
478 };
479
480 } // namespace time_internal
481
482 template <class TimeClass>
483 inline constexpr TimeClass operator+(TimeDelta delta, TimeClass t) {
484 return t + delta;
485 }
486
487 // Time -----------------------------------------------------------------------
488
489 // Represents a wall clock time in UTC. Values are not guaranteed to be
490 // monotonically non-decreasing and are subject to large amounts of skew.
491 // Time is stored internally as microseconds since the Windows epoch (1601).
492 class BASE_EXPORT Time : public time_internal::TimeBase<Time> {
493 public:
494 // Offset of UNIX epoch (1970-01-01 00:00:00 UTC) from Windows FILETIME epoch
495 // (1601-01-01 00:00:00 UTC), in microseconds. This value is derived from the
496 // following: ((1970-1601)*365+89)*24*60*60*1000*1000, where 89 is the number
497 // of leap year days between 1601 and 1970: (1970-1601)/4 excluding 1700,
498 // 1800, and 1900.
499 static constexpr int64_t kTimeTToMicrosecondsOffset =
500 INT64_C(11644473600000000);
501
502 #if defined(OS_WIN)
503 // To avoid overflow in QPC to Microseconds calculations, since we multiply
504 // by kMicrosecondsPerSecond, then the QPC value should not exceed
505 // (2^63 - 1) / 1E6. If it exceeds that threshold, we divide then multiply.
506 static constexpr int64_t kQPCOverflowThreshold = INT64_C(0x8637BD05AF7);
507 #endif
508
509 // kExplodedMinYear and kExplodedMaxYear define the platform-specific limits
510 // for values passed to FromUTCExploded() and FromLocalExploded(). Those
511 // functions will return false if passed values outside these limits. The limits
512 // are inclusive, meaning that the API should support all dates within a given
513 // limit year.
514 #if defined(OS_WIN)
515 static constexpr int kExplodedMinYear = 1601;
516 static constexpr int kExplodedMaxYear = 30827;
517 #elif defined(OS_IOS) && !__LP64__
518 static constexpr int kExplodedMinYear = std::numeric_limits<int>::min();
519 static constexpr int kExplodedMaxYear = std::numeric_limits<int>::max();
520 #elif defined(OS_MACOSX)
521 static constexpr int kExplodedMinYear = 1902;
522 static constexpr int kExplodedMaxYear = std::numeric_limits<int>::max();
523 #elif defined(OS_ANDROID)
524 // Though we use 64-bit time APIs on both 32 and 64 bit Android, some OS
525 // versions like KitKat (ARM but not x86 emulator) can't handle some early
526 // dates (e.g. before 1170). So we set min conservatively here.
527 static constexpr int kExplodedMinYear = 1902;
528 static constexpr int kExplodedMaxYear = std::numeric_limits<int>::max();
529 #else
530 static constexpr int kExplodedMinYear =
531 (sizeof(time_t) == 4 ? 1902 : std::numeric_limits<int>::min());
532 static constexpr int kExplodedMaxYear =
533 (sizeof(time_t) == 4 ? 2037 : std::numeric_limits<int>::max());
534 #endif
535
536 // Represents an exploded time that can be formatted nicely. This is kind of
537 // like the Win32 SYSTEMTIME structure or the Unix "struct tm" with a few
538 // additions and changes to prevent errors.
539 struct BASE_EXPORT Exploded {
540 int year; // Four digit year "2007"
541 int month; // 1-based month (values 1 = January, etc.)
542 int day_of_week; // 0-based day of week (0 = Sunday, etc.)
543 int day_of_month; // 1-based day of month (1-31)
544 int hour; // Hour within the current day (0-23)
545 int minute; // Minute within the current hour (0-59)
546 int second; // Second within the current minute (0-59 plus leap
547 // seconds which may take it up to 60).
548 int millisecond; // Milliseconds within the current second (0-999)
549
550 // A cursory test for whether the data members are within their
551 // respective ranges. A 'true' return value does not guarantee the
552 // Exploded value can be successfully converted to a Time value.
553 bool HasValidValues() const;
554 };
555
556 // Contains the NULL time. Use Time::Now() to get the current time.
Time()557 constexpr Time() : TimeBase(0) {}
558
559 // Returns the time for epoch in Unix-like system (Jan 1, 1970).
560 static Time UnixEpoch();
561
562 // Returns the current time. Watch out, the system might adjust its clock
563 // in which case time will actually go backwards. We don't guarantee that
564 // times are increasing, or that two calls to Now() won't be the same.
565 static Time Now();
566
567 // Returns the current time. Same as Now() except that this function always
568 // uses system time so that there are no discrepancies between the returned
569 // time and system time even on virtual environments including our test bot.
570 // For timing sensitive unittests, this function should be used.
571 static Time NowFromSystemTime();
572
573 // Converts to/from TimeDeltas relative to the Windows epoch (1601-01-01
574 // 00:00:00 UTC). Prefer these methods for opaque serialization and
575 // deserialization of time values, e.g.
576 //
577 // // Serialization:
578 // base::Time last_updated = ...;
579 // SaveToDatabase(last_updated.ToDeltaSinceWindowsEpoch().InMicroseconds());
580 //
581 // // Deserialization:
582 // base::Time last_updated = base::Time::FromDeltaSinceWindowsEpoch(
583 // base::TimeDelta::FromMicroseconds(LoadFromDatabase()));
584 static Time FromDeltaSinceWindowsEpoch(TimeDelta delta);
585 TimeDelta ToDeltaSinceWindowsEpoch() const;
586
587 // Converts to/from time_t in UTC and a Time class.
588 static Time FromTimeT(time_t tt);
589 time_t ToTimeT() const;
590
591 // Converts time to/from a double which is the number of seconds since epoch
592 // (Jan 1, 1970). Webkit uses this format to represent time.
593 // Because WebKit initializes double time value to 0 to indicate "not
594 // initialized", we map it to empty Time object that also means "not
595 // initialized".
596 static Time FromDoubleT(double dt);
597 double ToDoubleT() const;
598
599 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
600 // Converts the timespec structure to time. MacOS X 10.8.3 (and tentatively,
601 // earlier versions) will have the |ts|'s tv_nsec component zeroed out,
602 // having a 1 second resolution, which agrees with
603 // https://developer.apple.com/legacy/library/#technotes/tn/tn1150.html#HFSPlusDates.
604 static Time FromTimeSpec(const timespec& ts);
605 #endif
606
607 // Converts to/from the Javascript convention for times, a number of
608 // milliseconds since the epoch:
609 // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
610 //
611 // Don't use ToJsTime() in new code, since it contains a subtle hack (only
612 // exactly 1601-01-01 00:00 UTC is represented as 1970-01-01 00:00 UTC), and
613 // that is not appropriate for general use. Try to use ToJsTimeIgnoringNull()
614 // unless you have a very good reason to use ToJsTime().
615 static Time FromJsTime(double ms_since_epoch);
616 double ToJsTime() const;
617 double ToJsTimeIgnoringNull() const;
618
619 // Converts to/from Java convention for times, a number of milliseconds since
620 // the epoch. Because the Java format has less resolution, converting to Java
621 // time is a lossy operation.
622 static Time FromJavaTime(int64_t ms_since_epoch);
623 int64_t ToJavaTime() const;
624
625 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
626 static Time FromTimeVal(struct timeval t);
627 struct timeval ToTimeVal() const;
628 #endif
629
630 #if defined(OS_FUCHSIA)
631 static Time FromZxTime(zx_time_t time);
632 zx_time_t ToZxTime() const;
633 #endif
634
635 #if defined(OS_MACOSX)
636 static Time FromCFAbsoluteTime(CFAbsoluteTime t);
637 CFAbsoluteTime ToCFAbsoluteTime() const;
638 #endif
639
640 #if defined(OS_WIN)
641 static Time FromFileTime(FILETIME ft);
642 FILETIME ToFileTime() const;
643
644 // The minimum time of a low resolution timer. This is basically a windows
645 // constant of ~15.6ms. While it does vary on some older OS versions, we'll
646 // treat it as static across all windows versions.
647 static const int kMinLowResolutionThresholdMs = 16;
648
649 // Enable or disable Windows high resolution timer.
650 static void EnableHighResolutionTimer(bool enable);
651
652 // Read the minimum timer interval from the feature list. This should be
653 // called once after the feature list is initialized. This is needed for
654 // an experiment - see https://crbug.com/927165
655 static void ReadMinTimerIntervalLowResMs();
656
657 // Activates or deactivates the high resolution timer based on the |activate|
658 // flag. If the HighResolutionTimer is not Enabled (see
659 // EnableHighResolutionTimer), this function will return false. Otherwise
660 // returns true. Each successful activate call must be paired with a
661 // subsequent deactivate call.
662 // All callers to activate the high resolution timer must eventually call
663 // this function to deactivate the high resolution timer.
664 static bool ActivateHighResolutionTimer(bool activate);
665
666 // Returns true if the high resolution timer is both enabled and activated.
667 // This is provided for testing only, and is not tracked in a thread-safe
668 // way.
669 static bool IsHighResolutionTimerInUse();
670
671 // The following two functions are used to report the fraction of elapsed time
672 // that the high resolution timer is activated.
673 // ResetHighResolutionTimerUsage() resets the cumulative usage and starts the
674 // measurement interval and GetHighResolutionTimerUsage() returns the
675 // percentage of time since the reset that the high resolution timer was
676 // activated.
677 // ResetHighResolutionTimerUsage() must be called at least once before calling
678 // GetHighResolutionTimerUsage(); otherwise the usage result would be
679 // undefined.
680 static void ResetHighResolutionTimerUsage();
681 static double GetHighResolutionTimerUsage();
682 #endif // defined(OS_WIN)
683
684 // Converts an exploded structure representing either the local time or UTC
685 // into a Time class. Returns false on a failure when, for example, a day of
686 // month is set to 31 on a 28-30 day month. Returns Time(0) on overflow.
FromUTCExploded(const Exploded & exploded,Time * time)687 static bool FromUTCExploded(const Exploded& exploded,
688 Time* time) WARN_UNUSED_RESULT {
689 return FromExploded(false, exploded, time);
690 }
FromLocalExploded(const Exploded & exploded,Time * time)691 static bool FromLocalExploded(const Exploded& exploded,
692 Time* time) WARN_UNUSED_RESULT {
693 return FromExploded(true, exploded, time);
694 }
695
696 // Converts a string representation of time to a Time object.
697 // An example of a time string which is converted is as below:-
698 // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
699 // in the input string, FromString assumes local time and FromUTCString
700 // assumes UTC. A timezone that cannot be parsed (e.g. "UTC" which is not
701 // specified in RFC822) is treated as if the timezone is not specified.
702 //
703 // WARNING: the underlying converter is very permissive. For example: it is
704 // not checked whether a given day of the week matches the date; Feb 29
705 // silently becomes Mar 1 in non-leap years; under certain conditions, whole
706 // English sentences may be parsed successfully and yield unexpected results.
707 //
708 // TODO(iyengar) Move the FromString/FromTimeT/ToTimeT/FromFileTime to
709 // a new time converter class.
FromString(const char * time_string,Time * parsed_time)710 static bool FromString(const char* time_string,
711 Time* parsed_time) WARN_UNUSED_RESULT {
712 return FromStringInternal(time_string, true, parsed_time);
713 }
FromUTCString(const char * time_string,Time * parsed_time)714 static bool FromUTCString(const char* time_string,
715 Time* parsed_time) WARN_UNUSED_RESULT {
716 return FromStringInternal(time_string, false, parsed_time);
717 }
718
719 // Fills the given exploded structure with either the local time or UTC from
720 // this time structure (containing UTC).
UTCExplode(Exploded * exploded)721 void UTCExplode(Exploded* exploded) const {
722 return Explode(false, exploded);
723 }
LocalExplode(Exploded * exploded)724 void LocalExplode(Exploded* exploded) const {
725 return Explode(true, exploded);
726 }
727
728 // The following two functions round down the time to the nearest day in
729 // either UTC or local time. It will represent midnight on that day.
UTCMidnight()730 Time UTCMidnight() const { return Midnight(false); }
LocalMidnight()731 Time LocalMidnight() const { return Midnight(true); }
732
733 // Converts an integer value representing Time to a class. This may be used
734 // when deserializing a |Time| structure, using a value known to be
735 // compatible. It is not provided as a constructor because the integer type
736 // may be unclear from the perspective of a caller.
737 //
738 // DEPRECATED - Do not use in new code. For deserializing Time values, prefer
739 // Time::FromDeltaSinceWindowsEpoch(). http://crbug.com/634507
FromInternalValue(int64_t us)740 static constexpr Time FromInternalValue(int64_t us) { return Time(us); }
741
742 private:
743 friend class time_internal::TimeBase<Time>;
744
Time(int64_t microseconds_since_win_epoch)745 constexpr explicit Time(int64_t microseconds_since_win_epoch)
746 : TimeBase(microseconds_since_win_epoch) {}
747
748 // Explodes the given time to either local time |is_local = true| or UTC
749 // |is_local = false|.
750 void Explode(bool is_local, Exploded* exploded) const;
751
752 // Unexplodes a given time assuming the source is either local time
753 // |is_local = true| or UTC |is_local = false|. Function returns false on
754 // failure and sets |time| to Time(0). Otherwise returns true and sets |time|
755 // to non-exploded time.
756 static bool FromExploded(bool is_local,
757 const Exploded& exploded,
758 Time* time) WARN_UNUSED_RESULT;
759
760 // Rounds down the time to the nearest day in either local time
761 // |is_local = true| or UTC |is_local = false|.
762 Time Midnight(bool is_local) const;
763
764 // Converts a string representation of time to a Time object.
765 // An example of a time string which is converted is as below:-
766 // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
767 // in the input string, local time |is_local = true| or
768 // UTC |is_local = false| is assumed. A timezone that cannot be parsed
769 // (e.g. "UTC" which is not specified in RFC822) is treated as if the
770 // timezone is not specified.
771 static bool FromStringInternal(const char* time_string,
772 bool is_local,
773 Time* parsed_time) WARN_UNUSED_RESULT;
774
775 // Comparison does not consider |day_of_week| when doing the operation.
776 static bool ExplodedMostlyEquals(const Exploded& lhs,
777 const Exploded& rhs) WARN_UNUSED_RESULT;
778
779 // Converts the provided time in milliseconds since the Unix epoch (1970) to a
780 // Time object, avoiding overflows.
781 static bool FromMillisecondsSinceUnixEpoch(int64_t unix_milliseconds,
782 Time* time) WARN_UNUSED_RESULT;
783
784 // Returns the milliseconds since the Unix epoch (1970), rounding the
785 // microseconds towards -infinity.
786 int64_t ToRoundedDownMillisecondsSinceUnixEpoch() const;
787 };
788
789 // static
FromDays(int days)790 constexpr TimeDelta TimeDelta::FromDays(int days) {
791 return days == std::numeric_limits<int>::max()
792 ? Max()
793 : TimeDelta(days * Time::kMicrosecondsPerDay);
794 }
795
796 // static
FromHours(int hours)797 constexpr TimeDelta TimeDelta::FromHours(int hours) {
798 return hours == std::numeric_limits<int>::max()
799 ? Max()
800 : TimeDelta(hours * Time::kMicrosecondsPerHour);
801 }
802
803 // static
FromMinutes(int minutes)804 constexpr TimeDelta TimeDelta::FromMinutes(int minutes) {
805 return minutes == std::numeric_limits<int>::max()
806 ? Max()
807 : TimeDelta(minutes * Time::kMicrosecondsPerMinute);
808 }
809
810 // static
FromSeconds(int64_t secs)811 constexpr TimeDelta TimeDelta::FromSeconds(int64_t secs) {
812 return FromProduct(secs, Time::kMicrosecondsPerSecond);
813 }
814
815 // static
FromMilliseconds(int64_t ms)816 constexpr TimeDelta TimeDelta::FromMilliseconds(int64_t ms) {
817 return FromProduct(ms, Time::kMicrosecondsPerMillisecond);
818 }
819
820 // static
FromMicroseconds(int64_t us)821 constexpr TimeDelta TimeDelta::FromMicroseconds(int64_t us) {
822 return TimeDelta(us);
823 }
824
825 // static
FromNanoseconds(int64_t ns)826 constexpr TimeDelta TimeDelta::FromNanoseconds(int64_t ns) {
827 return TimeDelta(ns / Time::kNanosecondsPerMicrosecond);
828 }
829
830 // static
FromSecondsD(double secs)831 constexpr TimeDelta TimeDelta::FromSecondsD(double secs) {
832 return FromDouble(secs * Time::kMicrosecondsPerSecond);
833 }
834
835 // static
FromMillisecondsD(double ms)836 constexpr TimeDelta TimeDelta::FromMillisecondsD(double ms) {
837 return FromDouble(ms * Time::kMicrosecondsPerMillisecond);
838 }
839
840 // static
FromMicrosecondsD(double us)841 constexpr TimeDelta TimeDelta::FromMicrosecondsD(double us) {
842 return FromDouble(us);
843 }
844
845 // static
FromNanosecondsD(double ns)846 constexpr TimeDelta TimeDelta::FromNanosecondsD(double ns) {
847 return FromDouble(ns / Time::kNanosecondsPerMicrosecond);
848 }
849
850 // static
Max()851 constexpr TimeDelta TimeDelta::Max() {
852 return TimeDelta(std::numeric_limits<int64_t>::max());
853 }
854
855 // static
Min()856 constexpr TimeDelta TimeDelta::Min() {
857 return TimeDelta(std::numeric_limits<int64_t>::min());
858 }
859
860 // static
FromDouble(double value)861 constexpr TimeDelta TimeDelta::FromDouble(double value) {
862 return TimeDelta(saturated_cast<int64_t>(value));
863 }
864
865 // static
FromProduct(int64_t value,int64_t positive_value)866 constexpr TimeDelta TimeDelta::FromProduct(int64_t value,
867 int64_t positive_value) {
868 DCHECK(positive_value > 0); // NOLINT, DCHECK_GT isn't constexpr.
869 return value > std::numeric_limits<int64_t>::max() / positive_value
870 ? Max()
871 : value < std::numeric_limits<int64_t>::min() / positive_value
872 ? Min()
873 : TimeDelta(value * positive_value);
874 }
875
876 // For logging use only.
877 BASE_EXPORT std::ostream& operator<<(std::ostream& os, Time time);
878
879 // TimeTicks ------------------------------------------------------------------
880
881 // Represents monotonically non-decreasing clock time.
882 class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
883 public:
884 // The underlying clock used to generate new TimeTicks.
885 enum class Clock {
886 FUCHSIA_ZX_CLOCK_MONOTONIC,
887 LINUX_CLOCK_MONOTONIC,
888 IOS_CF_ABSOLUTE_TIME_MINUS_KERN_BOOTTIME,
889 MAC_MACH_ABSOLUTE_TIME,
890 WIN_QPC,
891 WIN_ROLLOVER_PROTECTED_TIME_GET_TIME
892 };
893
TimeTicks()894 constexpr TimeTicks() : TimeBase(0) {}
895
896 // Platform-dependent tick count representing "right now." When
897 // IsHighResolution() returns false, the resolution of the clock could be
898 // as coarse as ~15.6ms. Otherwise, the resolution should be no worse than one
899 // microsecond.
900 static TimeTicks Now();
901
902 // Returns true if the high resolution clock is working on this system and
903 // Now() will return high resolution values. Note that, on systems where the
904 // high resolution clock works but is deemed inefficient, the low resolution
905 // clock will be used instead.
906 static bool IsHighResolution() WARN_UNUSED_RESULT;
907
908 // Returns true if TimeTicks is consistent across processes, meaning that
909 // timestamps taken on different processes can be safely compared with one
910 // another. (Note that, even on platforms where this returns true, time values
911 // from different threads that are within one tick of each other must be
912 // considered to have an ambiguous ordering.)
913 static bool IsConsistentAcrossProcesses() WARN_UNUSED_RESULT;
914
915 #if defined(OS_FUCHSIA)
916 // Converts between TimeTicks and an ZX_CLOCK_MONOTONIC zx_time_t value.
917 static TimeTicks FromZxTime(zx_time_t nanos_since_boot);
918 zx_time_t ToZxTime() const;
919 #endif
920
921 #if defined(OS_WIN)
922 // Translates an absolute QPC timestamp into a TimeTicks value. The returned
923 // value has the same origin as Now(). Do NOT attempt to use this if
924 // IsHighResolution() returns false.
925 static TimeTicks FromQPCValue(LONGLONG qpc_value);
926 #endif
927
928 #if defined(OS_MACOSX) && !defined(OS_IOS)
929 static TimeTicks FromMachAbsoluteTime(uint64_t mach_absolute_time);
930 #endif // defined(OS_MACOSX) && !defined(OS_IOS)
931
932 #if defined(OS_ANDROID) || defined(OS_CHROMEOS)
933 // Converts to TimeTicks the value obtained from SystemClock.uptimeMillis().
934 // Note: this convertion may be non-monotonic in relation to previously
935 // obtained TimeTicks::Now() values because of the truncation (to
936 // milliseconds) performed by uptimeMillis().
937 static TimeTicks FromUptimeMillis(int64_t uptime_millis_value);
938 #endif
939
940 // Get an estimate of the TimeTick value at the time of the UnixEpoch. Because
941 // Time and TimeTicks respond differently to user-set time and NTP
942 // adjustments, this number is only an estimate. Nevertheless, this can be
943 // useful when you need to relate the value of TimeTicks to a real time and
944 // date. Note: Upon first invocation, this function takes a snapshot of the
945 // realtime clock to establish a reference point. This function will return
946 // the same value for the duration of the application, but will be different
947 // in future application runs.
948 static TimeTicks UnixEpoch();
949
950 // Returns |this| snapped to the next tick, given a |tick_phase| and
951 // repeating |tick_interval| in both directions. |this| may be before,
952 // after, or equal to the |tick_phase|.
953 TimeTicks SnappedToNextTick(TimeTicks tick_phase,
954 TimeDelta tick_interval) const;
955
956 // Returns an enum indicating the underlying clock being used to generate
957 // TimeTicks timestamps. This function should only be used for debugging and
958 // logging purposes.
959 static Clock GetClock();
960
961 // Converts an integer value representing TimeTicks to a class. This may be
962 // used when deserializing a |TimeTicks| structure, using a value known to be
963 // compatible. It is not provided as a constructor because the integer type
964 // may be unclear from the perspective of a caller.
965 //
966 // DEPRECATED - Do not use in new code. For deserializing TimeTicks values,
967 // prefer TimeTicks + TimeDelta(). http://crbug.com/634507
FromInternalValue(int64_t us)968 static constexpr TimeTicks FromInternalValue(int64_t us) {
969 return TimeTicks(us);
970 }
971
972 protected:
973 #if defined(OS_WIN)
974 typedef DWORD (*TickFunctionType)(void);
975 static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
976 #endif
977
978 private:
979 friend class time_internal::TimeBase<TimeTicks>;
980
981 // Please use Now() to create a new object. This is for internal use
982 // and testing.
TimeTicks(int64_t us)983 constexpr explicit TimeTicks(int64_t us) : TimeBase(us) {}
984 };
985
986 // For logging use only.
987 BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeTicks time_ticks);
988
989 // ThreadTicks ----------------------------------------------------------------
990
991 // Represents a clock, specific to a particular thread, than runs only while the
992 // thread is running.
993 class BASE_EXPORT ThreadTicks : public time_internal::TimeBase<ThreadTicks> {
994 public:
ThreadTicks()995 constexpr ThreadTicks() : TimeBase(0) {}
996
997 // Returns true if ThreadTicks::Now() is supported on this system.
IsSupported()998 static bool IsSupported() WARN_UNUSED_RESULT {
999 #if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
1000 (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_ANDROID) || \
1001 defined(OS_FUCHSIA)
1002 return true;
1003 #elif defined(OS_WIN)
1004 return IsSupportedWin();
1005 #else
1006 return false;
1007 #endif
1008 }
1009
1010 // Waits until the initialization is completed. Needs to be guarded with a
1011 // call to IsSupported().
WaitUntilInitialized()1012 static void WaitUntilInitialized() {
1013 #if defined(OS_WIN)
1014 WaitUntilInitializedWin();
1015 #endif
1016 }
1017
1018 // Returns thread-specific CPU-time on systems that support this feature.
1019 // Needs to be guarded with a call to IsSupported(). Use this timer
1020 // to (approximately) measure how much time the calling thread spent doing
1021 // actual work vs. being de-scheduled. May return bogus results if the thread
1022 // migrates to another CPU between two calls. Returns an empty ThreadTicks
1023 // object until the initialization is completed. If a clock reading is
1024 // absolutely needed, call WaitUntilInitialized() before this method.
1025 static ThreadTicks Now();
1026
1027 #if defined(OS_WIN)
1028 // Similar to Now() above except this returns thread-specific CPU time for an
1029 // arbitrary thread. All comments for Now() method above apply apply to this
1030 // method as well.
1031 static ThreadTicks GetForThread(const PlatformThreadHandle& thread_handle);
1032 #endif
1033
1034 // Converts an integer value representing ThreadTicks to a class. This may be
1035 // used when deserializing a |ThreadTicks| structure, using a value known to
1036 // be compatible. It is not provided as a constructor because the integer type
1037 // may be unclear from the perspective of a caller.
1038 //
1039 // DEPRECATED - Do not use in new code. For deserializing ThreadTicks values,
1040 // prefer ThreadTicks + TimeDelta(). http://crbug.com/634507
FromInternalValue(int64_t us)1041 static constexpr ThreadTicks FromInternalValue(int64_t us) {
1042 return ThreadTicks(us);
1043 }
1044
1045 private:
1046 friend class time_internal::TimeBase<ThreadTicks>;
1047
1048 // Please use Now() or GetForThread() to create a new object. This is for
1049 // internal use and testing.
ThreadTicks(int64_t us)1050 constexpr explicit ThreadTicks(int64_t us) : TimeBase(us) {}
1051
1052 #if defined(OS_WIN)
1053 FRIEND_TEST_ALL_PREFIXES(TimeTicks, TSCTicksPerSecond);
1054
1055 #if defined(ARCH_CPU_ARM64)
1056 // TSCTicksPerSecond is not supported on Windows on Arm systems because the
1057 // cycle-counting methods use the actual CPU cycle count, and not a consistent
1058 // incrementing counter.
1059 #else
1060 // Returns the frequency of the TSC in ticks per second, or 0 if it hasn't
1061 // been measured yet. Needs to be guarded with a call to IsSupported().
1062 // This method is declared here rather than in the anonymous namespace to
1063 // allow testing.
1064 static double TSCTicksPerSecond();
1065 #endif
1066
1067 static bool IsSupportedWin() WARN_UNUSED_RESULT;
1068 static void WaitUntilInitializedWin();
1069 #endif
1070 };
1071
1072 // For logging use only.
1073 BASE_EXPORT std::ostream& operator<<(std::ostream& os, ThreadTicks time_ticks);
1074
1075 } // namespace base
1076
1077 #endif // BASE_TIME_TIME_H_
1078