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) (See http://crbug.com/14734). System-dependent
8 // clock interface routines are defined in time_PLATFORM.cc.
9 //
10 // TimeDelta represents a duration of time, internally represented in
11 // microseconds.
12 //
13 // TimeTicks represents an abstract time that is most of the time incrementing
14 // for use in measuring time durations. It is internally represented in
15 // microseconds. It can not be converted to a human-readable time, but is
16 // guaranteed not to decrease (if the user changes the computer clock,
17 // Time::Now() may actually decrease or jump). But note that TimeTicks may
18 // "stand still", for example if the computer suspended.
19 //
20 // These classes are represented as only a 64-bit value, so they can be
21 // efficiently passed by value.
22
23 #ifndef BASE_TIME_TIME_H_
24 #define BASE_TIME_TIME_H_
25
26 #include <time.h>
27
28 #include "base/base_export.h"
29 #include "base/basictypes.h"
30 #include "build/build_config.h"
31
32 #if defined(OS_MACOSX)
33 #include <CoreFoundation/CoreFoundation.h>
34 // Avoid Mac system header macro leak.
35 #undef TYPE_BOOL
36 #endif
37
38 #if defined(OS_POSIX)
39 #include <unistd.h>
40 #include <sys/time.h>
41 #endif
42
43 #if defined(OS_WIN)
44 // For FILETIME in FromFileTime, until it moves to a new converter class.
45 // See TODO(iyengar) below.
46 #include <windows.h>
47 #endif
48
49 #include <limits>
50
51 namespace base {
52
53 class Time;
54 class TimeTicks;
55
56 // TimeDelta ------------------------------------------------------------------
57
58 class BASE_EXPORT TimeDelta {
59 public:
TimeDelta()60 TimeDelta() : delta_(0) {
61 }
62
63 // Converts units of time to TimeDeltas.
64 static TimeDelta FromDays(int days);
65 static TimeDelta FromHours(int hours);
66 static TimeDelta FromMinutes(int minutes);
67 static TimeDelta FromSeconds(int64 secs);
68 static TimeDelta FromMilliseconds(int64 ms);
69 static TimeDelta FromSecondsD(double secs);
70 static TimeDelta FromMillisecondsD(double ms);
71 static TimeDelta FromMicroseconds(int64 us);
72 #if defined(OS_WIN)
73 static TimeDelta FromQPCValue(LONGLONG qpc_value);
74 #endif
75
76 // Converts an integer value representing TimeDelta to a class. This is used
77 // when deserializing a |TimeDelta| structure, using a value known to be
78 // compatible. It is not provided as a constructor because the integer type
79 // may be unclear from the perspective of a caller.
FromInternalValue(int64 delta)80 static TimeDelta FromInternalValue(int64 delta) {
81 return TimeDelta(delta);
82 }
83
84 // Returns the maximum time delta, which should be greater than any reasonable
85 // time delta we might compare it to. Adding or subtracting the maximum time
86 // delta to a time or another time delta has an undefined result.
87 static TimeDelta Max();
88
89 // Returns the internal numeric value of the TimeDelta object. Please don't
90 // use this and do arithmetic on it, as it is more error prone than using the
91 // provided operators.
92 // For serializing, use FromInternalValue to reconstitute.
ToInternalValue()93 int64 ToInternalValue() const {
94 return delta_;
95 }
96
97 // Returns true if the time delta is the maximum time delta.
is_max()98 bool is_max() const {
99 return delta_ == std::numeric_limits<int64>::max();
100 }
101
102 #if defined(OS_POSIX)
103 struct timespec ToTimeSpec() const;
104 #endif
105
106 // Returns the time delta in some unit. The F versions return a floating
107 // point value, the "regular" versions return a rounded-down value.
108 //
109 // InMillisecondsRoundedUp() instead returns an integer that is rounded up
110 // to the next full millisecond.
111 int InDays() const;
112 int InHours() const;
113 int InMinutes() const;
114 double InSecondsF() const;
115 int64 InSeconds() const;
116 double InMillisecondsF() const;
117 int64 InMilliseconds() const;
118 int64 InMillisecondsRoundedUp() const;
119 int64 InMicroseconds() const;
120
121 TimeDelta& operator=(TimeDelta other) {
122 delta_ = other.delta_;
123 return *this;
124 }
125
126 // Computations with other deltas.
127 TimeDelta operator+(TimeDelta other) const {
128 return TimeDelta(delta_ + other.delta_);
129 }
130 TimeDelta operator-(TimeDelta other) const {
131 return TimeDelta(delta_ - other.delta_);
132 }
133
134 TimeDelta& operator+=(TimeDelta other) {
135 delta_ += other.delta_;
136 return *this;
137 }
138 TimeDelta& operator-=(TimeDelta other) {
139 delta_ -= other.delta_;
140 return *this;
141 }
142 TimeDelta operator-() const {
143 return TimeDelta(-delta_);
144 }
145
146 // Computations with ints, note that we only allow multiplicative operations
147 // with ints, and additive operations with other deltas.
148 TimeDelta operator*(int64 a) const {
149 return TimeDelta(delta_ * a);
150 }
151 TimeDelta operator/(int64 a) const {
152 return TimeDelta(delta_ / a);
153 }
154 TimeDelta& operator*=(int64 a) {
155 delta_ *= a;
156 return *this;
157 }
158 TimeDelta& operator/=(int64 a) {
159 delta_ /= a;
160 return *this;
161 }
162 int64 operator/(TimeDelta a) const {
163 return delta_ / a.delta_;
164 }
165
166 // Defined below because it depends on the definition of the other classes.
167 Time operator+(Time t) const;
168 TimeTicks operator+(TimeTicks t) const;
169
170 // Comparison operators.
171 bool operator==(TimeDelta other) const {
172 return delta_ == other.delta_;
173 }
174 bool operator!=(TimeDelta other) const {
175 return delta_ != other.delta_;
176 }
177 bool operator<(TimeDelta other) const {
178 return delta_ < other.delta_;
179 }
180 bool operator<=(TimeDelta other) const {
181 return delta_ <= other.delta_;
182 }
183 bool operator>(TimeDelta other) const {
184 return delta_ > other.delta_;
185 }
186 bool operator>=(TimeDelta other) const {
187 return delta_ >= other.delta_;
188 }
189
190 private:
191 friend class Time;
192 friend class TimeTicks;
193 friend TimeDelta operator*(int64 a, TimeDelta td);
194
195 // Constructs a delta given the duration in microseconds. This is private
196 // to avoid confusion by callers with an integer constructor. Use
197 // FromSeconds, FromMilliseconds, etc. instead.
TimeDelta(int64 delta_us)198 explicit TimeDelta(int64 delta_us) : delta_(delta_us) {
199 }
200
201 // Delta in microseconds.
202 int64 delta_;
203 };
204
205 inline TimeDelta operator*(int64 a, TimeDelta td) {
206 return TimeDelta(a * td.delta_);
207 }
208
209 // Time -----------------------------------------------------------------------
210
211 // Represents a wall clock time in UTC.
212 class BASE_EXPORT Time {
213 public:
214 static const int64 kMillisecondsPerSecond = 1000;
215 static const int64 kMicrosecondsPerMillisecond = 1000;
216 static const int64 kMicrosecondsPerSecond = kMicrosecondsPerMillisecond *
217 kMillisecondsPerSecond;
218 static const int64 kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
219 static const int64 kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
220 static const int64 kMicrosecondsPerDay = kMicrosecondsPerHour * 24;
221 static const int64 kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
222 static const int64 kNanosecondsPerMicrosecond = 1000;
223 static const int64 kNanosecondsPerSecond = kNanosecondsPerMicrosecond *
224 kMicrosecondsPerSecond;
225
226 #if !defined(OS_WIN)
227 // On Mac & Linux, this value is the delta from the Windows epoch of 1601 to
228 // the Posix delta of 1970. This is used for migrating between the old
229 // 1970-based epochs to the new 1601-based ones. It should be removed from
230 // this global header and put in the platform-specific ones when we remove the
231 // migration code.
232 static const int64 kWindowsEpochDeltaMicroseconds;
233 #endif
234
235 // Represents an exploded time that can be formatted nicely. This is kind of
236 // like the Win32 SYSTEMTIME structure or the Unix "struct tm" with a few
237 // additions and changes to prevent errors.
238 struct BASE_EXPORT Exploded {
239 int year; // Four digit year "2007"
240 int month; // 1-based month (values 1 = January, etc.)
241 int day_of_week; // 0-based day of week (0 = Sunday, etc.)
242 int day_of_month; // 1-based day of month (1-31)
243 int hour; // Hour within the current day (0-23)
244 int minute; // Minute within the current hour (0-59)
245 int second; // Second within the current minute (0-59 plus leap
246 // seconds which may take it up to 60).
247 int millisecond; // Milliseconds within the current second (0-999)
248
249 // A cursory test for whether the data members are within their
250 // respective ranges. A 'true' return value does not guarantee the
251 // Exploded value can be successfully converted to a Time value.
252 bool HasValidValues() const;
253 };
254
255 // Contains the NULL time. Use Time::Now() to get the current time.
Time()256 Time() : us_(0) {
257 }
258
259 // Returns true if the time object has not been initialized.
is_null()260 bool is_null() const {
261 return us_ == 0;
262 }
263
264 // Returns true if the time object is the maximum time.
is_max()265 bool is_max() const {
266 return us_ == std::numeric_limits<int64>::max();
267 }
268
269 // Returns the time for epoch in Unix-like system (Jan 1, 1970).
270 static Time UnixEpoch();
271
272 // Returns the current time. Watch out, the system might adjust its clock
273 // in which case time will actually go backwards. We don't guarantee that
274 // times are increasing, or that two calls to Now() won't be the same.
275 static Time Now();
276
277 // Returns the maximum time, which should be greater than any reasonable time
278 // with which we might compare it.
279 static Time Max();
280
281 // Returns the current time. Same as Now() except that this function always
282 // uses system time so that there are no discrepancies between the returned
283 // time and system time even on virtual environments including our test bot.
284 // For timing sensitive unittests, this function should be used.
285 static Time NowFromSystemTime();
286
287 // Converts to/from time_t in UTC and a Time class.
288 // TODO(brettw) this should be removed once everybody starts using the |Time|
289 // class.
290 static Time FromTimeT(time_t tt);
291 time_t ToTimeT() const;
292
293 // Converts time to/from a double which is the number of seconds since epoch
294 // (Jan 1, 1970). Webkit uses this format to represent time.
295 // Because WebKit initializes double time value to 0 to indicate "not
296 // initialized", we map it to empty Time object that also means "not
297 // initialized".
298 static Time FromDoubleT(double dt);
299 double ToDoubleT() const;
300
301 #if defined(OS_POSIX)
302 // Converts the timespec structure to time. MacOS X 10.8.3 (and tentatively,
303 // earlier versions) will have the |ts|'s tv_nsec component zeroed out,
304 // having a 1 second resolution, which agrees with
305 // https://developer.apple.com/legacy/library/#technotes/tn/tn1150.html#HFSPlusDates.
306 static Time FromTimeSpec(const timespec& ts);
307 #endif
308
309 // Converts to/from the Javascript convention for times, a number of
310 // milliseconds since the epoch:
311 // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
312 static Time FromJsTime(double ms_since_epoch);
313 double ToJsTime() const;
314
315 // Converts to Java convention for times, a number of
316 // milliseconds since the epoch.
317 int64 ToJavaTime() const;
318
319 #if defined(OS_POSIX)
320 static Time FromTimeVal(struct timeval t);
321 struct timeval ToTimeVal() const;
322 #endif
323
324 #if defined(OS_MACOSX)
325 static Time FromCFAbsoluteTime(CFAbsoluteTime t);
326 CFAbsoluteTime ToCFAbsoluteTime() const;
327 #endif
328
329 #if defined(OS_WIN)
330 static Time FromFileTime(FILETIME ft);
331 FILETIME ToFileTime() const;
332
333 // The minimum time of a low resolution timer. This is basically a windows
334 // constant of ~15.6ms. While it does vary on some older OS versions, we'll
335 // treat it as static across all windows versions.
336 static const int kMinLowResolutionThresholdMs = 16;
337
338 // Enable or disable Windows high resolution timer. If the high resolution
339 // timer is not enabled, calls to ActivateHighResolutionTimer will fail.
340 // When disabling the high resolution timer, this function will not cause
341 // the high resolution timer to be deactivated, but will prevent future
342 // activations.
343 // Must be called from the main thread.
344 // For more details see comments in time_win.cc.
345 static void EnableHighResolutionTimer(bool enable);
346
347 // Activates or deactivates the high resolution timer based on the |activate|
348 // flag. If the HighResolutionTimer is not Enabled (see
349 // EnableHighResolutionTimer), this function will return false. Otherwise
350 // returns true. Each successful activate call must be paired with a
351 // subsequent deactivate call.
352 // All callers to activate the high resolution timer must eventually call
353 // this function to deactivate the high resolution timer.
354 static bool ActivateHighResolutionTimer(bool activate);
355
356 // Returns true if the high resolution timer is both enabled and activated.
357 // This is provided for testing only, and is not tracked in a thread-safe
358 // way.
359 static bool IsHighResolutionTimerInUse();
360 #endif
361
362 // Converts an exploded structure representing either the local time or UTC
363 // into a Time class.
FromUTCExploded(const Exploded & exploded)364 static Time FromUTCExploded(const Exploded& exploded) {
365 return FromExploded(false, exploded);
366 }
FromLocalExploded(const Exploded & exploded)367 static Time FromLocalExploded(const Exploded& exploded) {
368 return FromExploded(true, exploded);
369 }
370
371 // Converts an integer value representing Time to a class. This is used
372 // when deserializing a |Time| structure, using a value known to be
373 // compatible. It is not provided as a constructor because the integer type
374 // may be unclear from the perspective of a caller.
FromInternalValue(int64 us)375 static Time FromInternalValue(int64 us) {
376 return Time(us);
377 }
378
379 // Converts a string representation of time to a Time object.
380 // An example of a time string which is converted is as below:-
381 // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
382 // in the input string, FromString assumes local time and FromUTCString
383 // assumes UTC. A timezone that cannot be parsed (e.g. "UTC" which is not
384 // specified in RFC822) is treated as if the timezone is not specified.
385 // TODO(iyengar) Move the FromString/FromTimeT/ToTimeT/FromFileTime to
386 // a new time converter class.
FromString(const char * time_string,Time * parsed_time)387 static bool FromString(const char* time_string, Time* parsed_time) {
388 return FromStringInternal(time_string, true, parsed_time);
389 }
FromUTCString(const char * time_string,Time * parsed_time)390 static bool FromUTCString(const char* time_string, Time* parsed_time) {
391 return FromStringInternal(time_string, false, parsed_time);
392 }
393
394 // For serializing, use FromInternalValue to reconstitute. Please don't use
395 // this and do arithmetic on it, as it is more error prone than using the
396 // provided operators.
ToInternalValue()397 int64 ToInternalValue() const {
398 return us_;
399 }
400
401 // Fills the given exploded structure with either the local time or UTC from
402 // this time structure (containing UTC).
UTCExplode(Exploded * exploded)403 void UTCExplode(Exploded* exploded) const {
404 return Explode(false, exploded);
405 }
LocalExplode(Exploded * exploded)406 void LocalExplode(Exploded* exploded) const {
407 return Explode(true, exploded);
408 }
409
410 // Rounds this time down to the nearest day in local time. It will represent
411 // midnight on that day.
412 Time LocalMidnight() const;
413
414 Time& operator=(Time other) {
415 us_ = other.us_;
416 return *this;
417 }
418
419 // Compute the difference between two times.
420 TimeDelta operator-(Time other) const {
421 return TimeDelta(us_ - other.us_);
422 }
423
424 // Modify by some time delta.
425 Time& operator+=(TimeDelta delta) {
426 us_ += delta.delta_;
427 return *this;
428 }
429 Time& operator-=(TimeDelta delta) {
430 us_ -= delta.delta_;
431 return *this;
432 }
433
434 // Return a new time modified by some delta.
435 Time operator+(TimeDelta delta) const {
436 return Time(us_ + delta.delta_);
437 }
438 Time operator-(TimeDelta delta) const {
439 return Time(us_ - delta.delta_);
440 }
441
442 // Comparison operators
443 bool operator==(Time other) const {
444 return us_ == other.us_;
445 }
446 bool operator!=(Time other) const {
447 return us_ != other.us_;
448 }
449 bool operator<(Time other) const {
450 return us_ < other.us_;
451 }
452 bool operator<=(Time other) const {
453 return us_ <= other.us_;
454 }
455 bool operator>(Time other) const {
456 return us_ > other.us_;
457 }
458 bool operator>=(Time other) const {
459 return us_ >= other.us_;
460 }
461
462 private:
463 friend class TimeDelta;
464
Time(int64 us)465 explicit Time(int64 us) : us_(us) {
466 }
467
468 // Explodes the given time to either local time |is_local = true| or UTC
469 // |is_local = false|.
470 void Explode(bool is_local, Exploded* exploded) const;
471
472 // Unexplodes a given time assuming the source is either local time
473 // |is_local = true| or UTC |is_local = false|.
474 static Time FromExploded(bool is_local, const Exploded& exploded);
475
476 // Converts a string representation of time to a Time object.
477 // An example of a time string which is converted is as below:-
478 // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
479 // in the input string, local time |is_local = true| or
480 // UTC |is_local = false| is assumed. A timezone that cannot be parsed
481 // (e.g. "UTC" which is not specified in RFC822) is treated as if the
482 // timezone is not specified.
483 static bool FromStringInternal(const char* time_string,
484 bool is_local,
485 Time* parsed_time);
486
487 // The representation of Jan 1, 1970 UTC in microseconds since the
488 // platform-dependent epoch.
489 static const int64 kTimeTToMicrosecondsOffset;
490
491 #if defined(OS_WIN)
492 // Indicates whether fast timers are usable right now. For instance,
493 // when using battery power, we might elect to prevent high speed timers
494 // which would draw more power.
495 static bool high_resolution_timer_enabled_;
496 // Count of activations on the high resolution timer. Only use in tests
497 // which are single threaded.
498 static int high_resolution_timer_activated_;
499 #endif
500
501 // Time in microseconds in UTC.
502 int64 us_;
503 };
504
505 // Inline the TimeDelta factory methods, for fast TimeDelta construction.
506
507 // static
FromDays(int days)508 inline TimeDelta TimeDelta::FromDays(int days) {
509 // Preserve max to prevent overflow.
510 if (days == std::numeric_limits<int>::max())
511 return Max();
512 return TimeDelta(days * Time::kMicrosecondsPerDay);
513 }
514
515 // static
FromHours(int hours)516 inline TimeDelta TimeDelta::FromHours(int hours) {
517 // Preserve max to prevent overflow.
518 if (hours == std::numeric_limits<int>::max())
519 return Max();
520 return TimeDelta(hours * Time::kMicrosecondsPerHour);
521 }
522
523 // static
FromMinutes(int minutes)524 inline TimeDelta TimeDelta::FromMinutes(int minutes) {
525 // Preserve max to prevent overflow.
526 if (minutes == std::numeric_limits<int>::max())
527 return Max();
528 return TimeDelta(minutes * Time::kMicrosecondsPerMinute);
529 }
530
531 // static
FromSeconds(int64 secs)532 inline TimeDelta TimeDelta::FromSeconds(int64 secs) {
533 // Preserve max to prevent overflow.
534 if (secs == std::numeric_limits<int64>::max())
535 return Max();
536 return TimeDelta(secs * Time::kMicrosecondsPerSecond);
537 }
538
539 // static
FromMilliseconds(int64 ms)540 inline TimeDelta TimeDelta::FromMilliseconds(int64 ms) {
541 // Preserve max to prevent overflow.
542 if (ms == std::numeric_limits<int64>::max())
543 return Max();
544 return TimeDelta(ms * Time::kMicrosecondsPerMillisecond);
545 }
546
547 // static
FromSecondsD(double secs)548 inline TimeDelta TimeDelta::FromSecondsD(double secs) {
549 // Preserve max to prevent overflow.
550 if (secs == std::numeric_limits<double>::infinity())
551 return Max();
552 return TimeDelta(secs * Time::kMicrosecondsPerSecond);
553 }
554
555 // static
FromMillisecondsD(double ms)556 inline TimeDelta TimeDelta::FromMillisecondsD(double ms) {
557 // Preserve max to prevent overflow.
558 if (ms == std::numeric_limits<double>::infinity())
559 return Max();
560 return TimeDelta(ms * Time::kMicrosecondsPerMillisecond);
561 }
562
563 // static
FromMicroseconds(int64 us)564 inline TimeDelta TimeDelta::FromMicroseconds(int64 us) {
565 // Preserve max to prevent overflow.
566 if (us == std::numeric_limits<int64>::max())
567 return Max();
568 return TimeDelta(us);
569 }
570
571 inline Time TimeDelta::operator+(Time t) const {
572 return Time(t.us_ + delta_);
573 }
574
575 // TimeTicks ------------------------------------------------------------------
576
577 class BASE_EXPORT TimeTicks {
578 public:
579 // We define this even without OS_CHROMEOS for seccomp sandbox testing.
580 #if defined(OS_LINUX)
581 // Force definition of the system trace clock; it is a chromeos-only api
582 // at the moment and surfacing it in the right place requires mucking
583 // with glibc et al.
584 static const clockid_t kClockSystemTrace = 11;
585 #endif
586
TimeTicks()587 TimeTicks() : ticks_(0) {
588 }
589
590 // Platform-dependent tick count representing "right now."
591 // The resolution of this clock is ~1-15ms. Resolution varies depending
592 // on hardware/operating system configuration.
593 static TimeTicks Now();
594
595 // Returns a platform-dependent high-resolution tick count. Implementation
596 // is hardware dependent and may or may not return sub-millisecond
597 // resolution. THIS CALL IS GENERALLY MUCH MORE EXPENSIVE THAN Now() AND
598 // SHOULD ONLY BE USED WHEN IT IS REALLY NEEDED.
599 static TimeTicks HighResNow();
600
601 static bool IsHighResNowFastAndReliable();
602
603 // Returns true if ThreadNow() is supported on this system.
IsThreadNowSupported()604 static bool IsThreadNowSupported() {
605 #if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
606 (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_ANDROID)
607 return true;
608 #else
609 return false;
610 #endif
611 }
612
613 // Returns thread-specific CPU-time on systems that support this feature.
614 // Needs to be guarded with a call to IsThreadNowSupported(). Use this timer
615 // to (approximately) measure how much time the calling thread spent doing
616 // actual work vs. being de-scheduled. May return bogus results if the thread
617 // migrates to another CPU between two calls.
618 static TimeTicks ThreadNow();
619
620 // Returns the current system trace time or, if none is defined, the current
621 // high-res time (i.e. HighResNow()). On systems where a global trace clock
622 // is defined, timestamping TraceEvents's with this value guarantees
623 // synchronization between events collected inside chrome and events
624 // collected outside (e.g. kernel, X server).
625 static TimeTicks NowFromSystemTraceTime();
626
627 #if defined(OS_WIN)
628 // Get the absolute value of QPC time drift. For testing.
629 static int64 GetQPCDriftMicroseconds();
630
631 static TimeTicks FromQPCValue(LONGLONG qpc_value);
632
633 // Returns true if the high resolution clock is working on this system.
634 // This is only for testing.
635 static bool IsHighResClockWorking();
636
637 // Enable high resolution time for TimeTicks::Now(). This function will
638 // test for the availability of a working implementation of
639 // QueryPerformanceCounter(). If one is not available, this function does
640 // nothing and the resolution of Now() remains 1ms. Otherwise, all future
641 // calls to TimeTicks::Now() will have the higher resolution provided by QPC.
642 // Returns true if high resolution time was successfully enabled.
643 static bool SetNowIsHighResNowIfSupported();
644
645 // Returns a time value that is NOT rollover protected.
646 static TimeTicks UnprotectedNow();
647 #endif
648
649 // Returns true if this object has not been initialized.
is_null()650 bool is_null() const {
651 return ticks_ == 0;
652 }
653
654 // Converts an integer value representing TimeTicks to a class. This is used
655 // when deserializing a |TimeTicks| structure, using a value known to be
656 // compatible. It is not provided as a constructor because the integer type
657 // may be unclear from the perspective of a caller.
FromInternalValue(int64 ticks)658 static TimeTicks FromInternalValue(int64 ticks) {
659 return TimeTicks(ticks);
660 }
661
662 // Get the TimeTick value at the time of the UnixEpoch. This is useful when
663 // you need to relate the value of TimeTicks to a real time and date.
664 // Note: Upon first invocation, this function takes a snapshot of the realtime
665 // clock to establish a reference point. This function will return the same
666 // value for the duration of the application, but will be different in future
667 // application runs.
668 static TimeTicks UnixEpoch();
669
670 // Returns the internal numeric value of the TimeTicks object.
671 // For serializing, use FromInternalValue to reconstitute.
ToInternalValue()672 int64 ToInternalValue() const {
673 return ticks_;
674 }
675
676 TimeTicks& operator=(TimeTicks other) {
677 ticks_ = other.ticks_;
678 return *this;
679 }
680
681 // Compute the difference between two times.
682 TimeDelta operator-(TimeTicks other) const {
683 return TimeDelta(ticks_ - other.ticks_);
684 }
685
686 // Modify by some time delta.
687 TimeTicks& operator+=(TimeDelta delta) {
688 ticks_ += delta.delta_;
689 return *this;
690 }
691 TimeTicks& operator-=(TimeDelta delta) {
692 ticks_ -= delta.delta_;
693 return *this;
694 }
695
696 // Return a new TimeTicks modified by some delta.
697 TimeTicks operator+(TimeDelta delta) const {
698 return TimeTicks(ticks_ + delta.delta_);
699 }
700 TimeTicks operator-(TimeDelta delta) const {
701 return TimeTicks(ticks_ - delta.delta_);
702 }
703
704 // Comparison operators
705 bool operator==(TimeTicks other) const {
706 return ticks_ == other.ticks_;
707 }
708 bool operator!=(TimeTicks other) const {
709 return ticks_ != other.ticks_;
710 }
711 bool operator<(TimeTicks other) const {
712 return ticks_ < other.ticks_;
713 }
714 bool operator<=(TimeTicks other) const {
715 return ticks_ <= other.ticks_;
716 }
717 bool operator>(TimeTicks other) const {
718 return ticks_ > other.ticks_;
719 }
720 bool operator>=(TimeTicks other) const {
721 return ticks_ >= other.ticks_;
722 }
723
724 protected:
725 friend class TimeDelta;
726
727 // Please use Now() to create a new object. This is for internal use
728 // and testing. Ticks is in microseconds.
TimeTicks(int64 ticks)729 explicit TimeTicks(int64 ticks) : ticks_(ticks) {
730 }
731
732 // Tick count in microseconds.
733 int64 ticks_;
734
735 #if defined(OS_WIN)
736 typedef DWORD (*TickFunctionType)(void);
737 static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
738 #endif
739 };
740
741 inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
742 return TimeTicks(t.ticks_ + delta_);
743 }
744
745 } // namespace base
746
747 #endif // BASE_TIME_TIME_H_
748