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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Time represents an absolute point in coordinated universal time (UTC),
+// internally represented as microseconds (s/1,000,000) since the Windows epoch
+// (1601-01-01 00:00:00 UTC). System-dependent clock interface routines are
+// defined in time_PLATFORM.cc. Note that values for Time may skew and jump
+// around as the operating system makes adjustments to synchronize (e.g., with
+// NTP servers). Thus, client code that uses the Time class must account for
+// this.
+//
+// TimeDelta represents a duration of time, internally represented in
+// microseconds.
+//
+// TimeTicks and ThreadTicks represent an abstract time that is most of the time
+// incrementing, for use in measuring time durations. Internally, they are
+// represented in microseconds. They can not be converted to a human-readable
+// time, but are guaranteed not to decrease (unlike the Time class). Note that
+// TimeTicks may "stand still" (e.g., if the computer is suspended), and
+// ThreadTicks will "stand still" whenever the thread has been de-scheduled by
+// the operating system.
+//
+// All time classes are copyable, assignable, and occupy 64-bits per
+// instance. Thus, they can be efficiently passed by-value (as opposed to
+// by-reference).
+//
+// Definitions of operator<< are provided to make these types work with
+// DCHECK_EQ() and other log macros. For human-readable formatting, see
+// "base/i18n/time_formatting.h".
+//
+// So many choices! Which time class should you use? Examples:
+//
+// Time: Interpreting the wall-clock time provided by a remote
+// system. Detecting whether cached resources have
+// expired. Providing the user with a display of the current date
+// and time. Determining the amount of time between events across
+// re-boots of the machine.
+//
+// TimeTicks: Tracking the amount of time a task runs. Executing delayed
+// tasks at the right time. Computing presentation timestamps.
+// Synchronizing audio and video using TimeTicks as a common
+// reference clock (lip-sync). Measuring network round-trip
+// latency.
+//
+// ThreadTicks: Benchmarking how long the current thread has been doing actual
+// work.
+
+#ifndef BASE_TIME_TIME_H_
+#define BASE_TIME_TIME_H_
+
+#include <stdint.h>
+#include <time.h>
+
+#include <iosfwd>
+#include <limits>
+
+#include "base/base_export.h"
+#include "base/numerics/safe_math.h"
+#include "build/build_config.h"
+
+#if defined(OS_MACOSX)
+#include <CoreFoundation/CoreFoundation.h>
+// Avoid Mac system header macro leak.
+#undef TYPE_BOOL
+#endif
+
+#if defined(OS_POSIX)
+#include <unistd.h>
+#include <sys/time.h>
+#endif
+
+#if defined(OS_WIN)
+// For FILETIME in FromFileTime, until it moves to a new converter class.
+// See TODO(iyengar) below.
+#include <windows.h>
+
+#include "base/gtest_prod_util.h"
+#endif
+
+namespace base {
+
+class TimeDelta;
+
+// The functions in the time_internal namespace are meant to be used only by the
+// time classes and functions. Please use the math operators defined in the
+// time classes instead.
+namespace time_internal {
+
+// Add or subtract |value| from a TimeDelta. The int64_t argument and return
+// value are in terms of a microsecond timebase.
+BASE_EXPORT int64_t SaturatedAdd(TimeDelta delta, int64_t value);
+BASE_EXPORT int64_t SaturatedSub(TimeDelta delta, int64_t value);
+
+// Clamp |value| on overflow and underflow conditions. The int64_t argument and
+// return value are in terms of a microsecond timebase.
+BASE_EXPORT int64_t FromCheckedNumeric(const CheckedNumeric<int64_t> value);
+
+} // namespace time_internal
+
+// TimeDelta ------------------------------------------------------------------
+
+class BASE_EXPORT TimeDelta {
+ public:
+ TimeDelta() : delta_(0) {
+ }
+
+ // Converts units of time to TimeDeltas.
+ static TimeDelta FromDays(int days);
+ static TimeDelta FromHours(int hours);
+ static TimeDelta FromMinutes(int minutes);
+ static TimeDelta FromSeconds(int64_t secs);
+ static TimeDelta FromMilliseconds(int64_t ms);
+ static TimeDelta FromSecondsD(double secs);
+ static TimeDelta FromMillisecondsD(double ms);
+ static TimeDelta FromMicroseconds(int64_t us);
+#if defined(OS_WIN)
+ static TimeDelta FromQPCValue(LONGLONG qpc_value);
+#endif
+
+ // Converts an integer value representing TimeDelta to a class. This is used
+ // when deserializing a |TimeDelta| structure, using a value known to be
+ // compatible. It is not provided as a constructor because the integer type
+ // may be unclear from the perspective of a caller.
+ static TimeDelta FromInternalValue(int64_t delta) { return TimeDelta(delta); }
+
+ // Returns the maximum time delta, which should be greater than any reasonable
+ // time delta we might compare it to. Adding or subtracting the maximum time
+ // delta to a time or another time delta has an undefined result.
+ static TimeDelta Max();
+
+ // Returns the internal numeric value of the TimeDelta object. Please don't
+ // use this and do arithmetic on it, as it is more error prone than using the
+ // provided operators.
+ // For serializing, use FromInternalValue to reconstitute.
+ int64_t ToInternalValue() const { return delta_; }
+
+ // Returns the magnitude (absolute value) of this TimeDelta.
+ TimeDelta magnitude() const {
+ // Some toolchains provide an incomplete C++11 implementation and lack an
+ // int64_t overload for std::abs(). The following is a simple branchless
+ // implementation:
+ const int64_t mask = delta_ >> (sizeof(delta_) * 8 - 1);
+ return TimeDelta((delta_ + mask) ^ mask);
+ }
+
+ // Returns true if the time delta is zero.
+ bool is_zero() const {
+ return delta_ == 0;
+ }
+
+ // Returns true if the time delta is the maximum time delta.
+ bool is_max() const { return delta_ == std::numeric_limits<int64_t>::max(); }
+
+#if defined(OS_POSIX)
+ struct timespec ToTimeSpec() const;
+#endif
+
+ // Returns the time delta in some unit. The F versions return a floating
+ // point value, the "regular" versions return a rounded-down value.
+ //
+ // InMillisecondsRoundedUp() instead returns an integer that is rounded up
+ // to the next full millisecond.
+ int InDays() const;
+ int InHours() const;
+ int InMinutes() const;
+ double InSecondsF() const;
+ int64_t InSeconds() const;
+ double InMillisecondsF() const;
+ int64_t InMilliseconds() const;
+ int64_t InMillisecondsRoundedUp() const;
+ int64_t InMicroseconds() const;
+
+ TimeDelta& operator=(TimeDelta other) {
+ delta_ = other.delta_;
+ return *this;
+ }
+
+ // Computations with other deltas.
+ TimeDelta operator+(TimeDelta other) const {
+ return TimeDelta(time_internal::SaturatedAdd(*this, other.delta_));
+ }
+ TimeDelta operator-(TimeDelta other) const {
+ return TimeDelta(time_internal::SaturatedSub(*this, other.delta_));
+ }
+
+ TimeDelta& operator+=(TimeDelta other) {
+ return *this = (*this + other);
+ }
+ TimeDelta& operator-=(TimeDelta other) {
+ return *this = (*this - other);
+ }
+ TimeDelta operator-() const {
+ return TimeDelta(-delta_);
+ }
+
+ // Computations with numeric types.
+ template<typename T>
+ TimeDelta operator*(T a) const {
+ CheckedNumeric<int64_t> rv(delta_);
+ rv *= a;
+ return TimeDelta(time_internal::FromCheckedNumeric(rv));
+ }
+ template<typename T>
+ TimeDelta operator/(T a) const {
+ CheckedNumeric<int64_t> rv(delta_);
+ rv /= a;
+ return TimeDelta(time_internal::FromCheckedNumeric(rv));
+ }
+ template<typename T>
+ TimeDelta& operator*=(T a) {
+ return *this = (*this * a);
+ }
+ template<typename T>
+ TimeDelta& operator/=(T a) {
+ return *this = (*this / a);
+ }
+
+ int64_t operator/(TimeDelta a) const { return delta_ / a.delta_; }
+ TimeDelta operator%(TimeDelta a) const {
+ return TimeDelta(delta_ % a.delta_);
+ }
+
+ // Comparison operators.
+ bool operator==(TimeDelta other) const {
+ return delta_ == other.delta_;
+ }
+ bool operator!=(TimeDelta other) const {
+ return delta_ != other.delta_;
+ }
+ bool operator<(TimeDelta other) const {
+ return delta_ < other.delta_;
+ }
+ bool operator<=(TimeDelta other) const {
+ return delta_ <= other.delta_;
+ }
+ bool operator>(TimeDelta other) const {
+ return delta_ > other.delta_;
+ }
+ bool operator>=(TimeDelta other) const {
+ return delta_ >= other.delta_;
+ }
+
+ private:
+ friend int64_t time_internal::SaturatedAdd(TimeDelta delta, int64_t value);
+ friend int64_t time_internal::SaturatedSub(TimeDelta delta, int64_t value);
+
+ // Constructs a delta given the duration in microseconds. This is private
+ // to avoid confusion by callers with an integer constructor. Use
+ // FromSeconds, FromMilliseconds, etc. instead.
+ explicit TimeDelta(int64_t delta_us) : delta_(delta_us) {}
+
+ // Private method to build a delta from a double.
+ static TimeDelta FromDouble(double value);
+
+ // Delta in microseconds.
+ int64_t delta_;
+};
+
+template<typename T>
+inline TimeDelta operator*(T a, TimeDelta td) {
+ return td * a;
+}
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeDelta time_delta);
+
+// Do not reference the time_internal::TimeBase template class directly. Please
+// use one of the time subclasses instead, and only reference the public
+// TimeBase members via those classes.
+namespace time_internal {
+
+// TimeBase--------------------------------------------------------------------
+
+// Provides value storage and comparison/math operations common to all time
+// classes. Each subclass provides for strong type-checking to ensure
+// semantically meaningful comparison/math of time values from the same clock
+// source or timeline.
+template<class TimeClass>
+class TimeBase {
+ public:
+ static const int64_t kHoursPerDay = 24;
+ static const int64_t kMillisecondsPerSecond = 1000;
+ static const int64_t kMillisecondsPerDay =
+ kMillisecondsPerSecond * 60 * 60 * kHoursPerDay;
+ static const int64_t kMicrosecondsPerMillisecond = 1000;
+ static const int64_t kMicrosecondsPerSecond =
+ kMicrosecondsPerMillisecond * kMillisecondsPerSecond;
+ static const int64_t kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
+ static const int64_t kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
+ static const int64_t kMicrosecondsPerDay =
+ kMicrosecondsPerHour * kHoursPerDay;
+ static const int64_t kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
+ static const int64_t kNanosecondsPerMicrosecond = 1000;
+ static const int64_t kNanosecondsPerSecond =
+ kNanosecondsPerMicrosecond * kMicrosecondsPerSecond;
+
+ // Returns true if this object has not been initialized.
+ //
+ // Warning: Be careful when writing code that performs math on time values,
+ // since it's possible to produce a valid "zero" result that should not be
+ // interpreted as a "null" value.
+ bool is_null() const {
+ return us_ == 0;
+ }
+
+ // Returns true if this object represents the maximum time.
+ bool is_max() const { return us_ == std::numeric_limits<int64_t>::max(); }
+
+ // For serializing only. Use FromInternalValue() to reconstitute. Please don't
+ // use this and do arithmetic on it, as it is more error prone than using the
+ // provided operators.
+ int64_t ToInternalValue() const { return us_; }
+
+ TimeClass& operator=(TimeClass other) {
+ us_ = other.us_;
+ return *(static_cast<TimeClass*>(this));
+ }
+
+ // Compute the difference between two times.
+ TimeDelta operator-(TimeClass other) const {
+ return TimeDelta::FromMicroseconds(us_ - other.us_);
+ }
+
+ // Return a new time modified by some delta.
+ TimeClass operator+(TimeDelta delta) const {
+ return TimeClass(time_internal::SaturatedAdd(delta, us_));
+ }
+ TimeClass operator-(TimeDelta delta) const {
+ return TimeClass(-time_internal::SaturatedSub(delta, us_));
+ }
+
+ // Modify by some time delta.
+ TimeClass& operator+=(TimeDelta delta) {
+ return static_cast<TimeClass&>(*this = (*this + delta));
+ }
+ TimeClass& operator-=(TimeDelta delta) {
+ return static_cast<TimeClass&>(*this = (*this - delta));
+ }
+
+ // Comparison operators
+ bool operator==(TimeClass other) const {
+ return us_ == other.us_;
+ }
+ bool operator!=(TimeClass other) const {
+ return us_ != other.us_;
+ }
+ bool operator<(TimeClass other) const {
+ return us_ < other.us_;
+ }
+ bool operator<=(TimeClass other) const {
+ return us_ <= other.us_;
+ }
+ bool operator>(TimeClass other) const {
+ return us_ > other.us_;
+ }
+ bool operator>=(TimeClass other) const {
+ return us_ >= other.us_;
+ }
+
+ // Converts an integer value representing TimeClass to a class. This is used
+ // when deserializing a |TimeClass| structure, using a value known to be
+ // compatible. It is not provided as a constructor because the integer type
+ // may be unclear from the perspective of a caller.
+ static TimeClass FromInternalValue(int64_t us) { return TimeClass(us); }
+
+ protected:
+ explicit TimeBase(int64_t us) : us_(us) {}
+
+ // Time value in a microsecond timebase.
+ int64_t us_;
+};
+
+} // namespace time_internal
+
+template<class TimeClass>
+inline TimeClass operator+(TimeDelta delta, TimeClass t) {
+ return t + delta;
+}
+
+// Time -----------------------------------------------------------------------
+
+// Represents a wall clock time in UTC. Values are not guaranteed to be
+// monotonically non-decreasing and are subject to large amounts of skew.
+class BASE_EXPORT Time : public time_internal::TimeBase<Time> {
+ public:
+ // The representation of Jan 1, 1970 UTC in microseconds since the
+ // platform-dependent epoch.
+ static const int64_t kTimeTToMicrosecondsOffset;
+
+#if !defined(OS_WIN)
+ // On Mac & Linux, this value is the delta from the Windows epoch of 1601 to
+ // the Posix delta of 1970. This is used for migrating between the old
+ // 1970-based epochs to the new 1601-based ones. It should be removed from
+ // this global header and put in the platform-specific ones when we remove the
+ // migration code.
+ static const int64_t kWindowsEpochDeltaMicroseconds;
+#else
+ // To avoid overflow in QPC to Microseconds calculations, since we multiply
+ // by kMicrosecondsPerSecond, then the QPC value should not exceed
+ // (2^63 - 1) / 1E6. If it exceeds that threshold, we divide then multiply.
+ enum : int64_t{kQPCOverflowThreshold = 0x8637BD05AF7};
+#endif
+
+ // Represents an exploded time that can be formatted nicely. This is kind of
+ // like the Win32 SYSTEMTIME structure or the Unix "struct tm" with a few
+ // additions and changes to prevent errors.
+ struct BASE_EXPORT Exploded {
+ int year; // Four digit year "2007"
+ int month; // 1-based month (values 1 = January, etc.)
+ int day_of_week; // 0-based day of week (0 = Sunday, etc.)
+ int day_of_month; // 1-based day of month (1-31)
+ int hour; // Hour within the current day (0-23)
+ int minute; // Minute within the current hour (0-59)
+ int second; // Second within the current minute (0-59 plus leap
+ // seconds which may take it up to 60).
+ int millisecond; // Milliseconds within the current second (0-999)
+
+ // A cursory test for whether the data members are within their
+ // respective ranges. A 'true' return value does not guarantee the
+ // Exploded value can be successfully converted to a Time value.
+ bool HasValidValues() const;
+ };
+
+ // Contains the NULL time. Use Time::Now() to get the current time.
+ Time() : TimeBase(0) {
+ }
+
+ // Returns the time for epoch in Unix-like system (Jan 1, 1970).
+ static Time UnixEpoch();
+
+ // Returns the current time. Watch out, the system might adjust its clock
+ // in which case time will actually go backwards. We don't guarantee that
+ // times are increasing, or that two calls to Now() won't be the same.
+ static Time Now();
+
+ // Returns the maximum time, which should be greater than any reasonable time
+ // with which we might compare it.
+ static Time Max();
+
+ // Returns the current time. Same as Now() except that this function always
+ // uses system time so that there are no discrepancies between the returned
+ // time and system time even on virtual environments including our test bot.
+ // For timing sensitive unittests, this function should be used.
+ static Time NowFromSystemTime();
+
+ // Converts to/from time_t in UTC and a Time class.
+ // TODO(brettw) this should be removed once everybody starts using the |Time|
+ // class.
+ static Time FromTimeT(time_t tt);
+ time_t ToTimeT() const;
+
+ // Converts time to/from a double which is the number of seconds since epoch
+ // (Jan 1, 1970). Webkit uses this format to represent time.
+ // Because WebKit initializes double time value to 0 to indicate "not
+ // initialized", we map it to empty Time object that also means "not
+ // initialized".
+ static Time FromDoubleT(double dt);
+ double ToDoubleT() const;
+
+#if defined(OS_POSIX)
+ // Converts the timespec structure to time. MacOS X 10.8.3 (and tentatively,
+ // earlier versions) will have the |ts|'s tv_nsec component zeroed out,
+ // having a 1 second resolution, which agrees with
+ // https://developer.apple.com/legacy/library/#technotes/tn/tn1150.html#HFSPlusDates.
+ static Time FromTimeSpec(const timespec& ts);
+#endif
+
+ // Converts to/from the Javascript convention for times, a number of
+ // milliseconds since the epoch:
+ // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
+ static Time FromJsTime(double ms_since_epoch);
+ double ToJsTime() const;
+
+ // Converts to Java convention for times, a number of
+ // milliseconds since the epoch.
+ int64_t ToJavaTime() const;
+
+#if defined(OS_POSIX)
+ static Time FromTimeVal(struct timeval t);
+ struct timeval ToTimeVal() const;
+#endif
+
+#if defined(OS_MACOSX)
+ static Time FromCFAbsoluteTime(CFAbsoluteTime t);
+ CFAbsoluteTime ToCFAbsoluteTime() const;
+#endif
+
+#if defined(OS_WIN)
+ static Time FromFileTime(FILETIME ft);
+ FILETIME ToFileTime() const;
+
+ // The minimum time of a low resolution timer. This is basically a windows
+ // constant of ~15.6ms. While it does vary on some older OS versions, we'll
+ // treat it as static across all windows versions.
+ static const int kMinLowResolutionThresholdMs = 16;
+
+ // Enable or disable Windows high resolution timer.
+ static void EnableHighResolutionTimer(bool enable);
+
+ // Activates or deactivates the high resolution timer based on the |activate|
+ // flag. If the HighResolutionTimer is not Enabled (see
+ // EnableHighResolutionTimer), this function will return false. Otherwise
+ // returns true. Each successful activate call must be paired with a
+ // subsequent deactivate call.
+ // All callers to activate the high resolution timer must eventually call
+ // this function to deactivate the high resolution timer.
+ static bool ActivateHighResolutionTimer(bool activate);
+
+ // Returns true if the high resolution timer is both enabled and activated.
+ // This is provided for testing only, and is not tracked in a thread-safe
+ // way.
+ static bool IsHighResolutionTimerInUse();
+#endif
+
+ // Converts an exploded structure representing either the local time or UTC
+ // into a Time class.
+ static Time FromUTCExploded(const Exploded& exploded) {
+ return FromExploded(false, exploded);
+ }
+ static Time FromLocalExploded(const Exploded& exploded) {
+ return FromExploded(true, exploded);
+ }
+
+#if !defined(MOZ_SANDBOX)
+ // Converts a string representation of time to a Time object.
+ // An example of a time string which is converted is as below:-
+ // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
+ // in the input string, FromString assumes local time and FromUTCString
+ // assumes UTC. A timezone that cannot be parsed (e.g. "UTC" which is not
+ // specified in RFC822) is treated as if the timezone is not specified.
+ // TODO(iyengar) Move the FromString/FromTimeT/ToTimeT/FromFileTime to
+ // a new time converter class.
+ static bool FromString(const char* time_string, Time* parsed_time) {
+ return FromStringInternal(time_string, true, parsed_time);
+ }
+ static bool FromUTCString(const char* time_string, Time* parsed_time) {
+ return FromStringInternal(time_string, false, parsed_time);
+ }
+#endif
+
+ // Fills the given exploded structure with either the local time or UTC from
+ // this time structure (containing UTC).
+ void UTCExplode(Exploded* exploded) const {
+ return Explode(false, exploded);
+ }
+ void LocalExplode(Exploded* exploded) const {
+ return Explode(true, exploded);
+ }
+
+ // Rounds this time down to the nearest day in local time. It will represent
+ // midnight on that day.
+ Time LocalMidnight() const;
+
+ private:
+ friend class time_internal::TimeBase<Time>;
+
+ explicit Time(int64_t us) : TimeBase(us) {}
+
+ // Explodes the given time to either local time |is_local = true| or UTC
+ // |is_local = false|.
+ void Explode(bool is_local, Exploded* exploded) const;
+
+ // Unexplodes a given time assuming the source is either local time
+ // |is_local = true| or UTC |is_local = false|.
+ static Time FromExploded(bool is_local, const Exploded& exploded);
+
+#if !defined(MOZ_SANDBOX)
+ // Converts a string representation of time to a Time object.
+ // An example of a time string which is converted is as below:-
+ // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
+ // in the input string, local time |is_local = true| or
+ // UTC |is_local = false| is assumed. A timezone that cannot be parsed
+ // (e.g. "UTC" which is not specified in RFC822) is treated as if the
+ // timezone is not specified.
+ static bool FromStringInternal(const char* time_string,
+ bool is_local,
+ Time* parsed_time);
+#endif
+};
+
+// Inline the TimeDelta factory methods, for fast TimeDelta construction.
+
+// static
+inline TimeDelta TimeDelta::FromDays(int days) {
+ if (days == std::numeric_limits<int>::max())
+ return Max();
+ return TimeDelta(days * Time::kMicrosecondsPerDay);
+}
+
+// static
+inline TimeDelta TimeDelta::FromHours(int hours) {
+ if (hours == std::numeric_limits<int>::max())
+ return Max();
+ return TimeDelta(hours * Time::kMicrosecondsPerHour);
+}
+
+// static
+inline TimeDelta TimeDelta::FromMinutes(int minutes) {
+ if (minutes == std::numeric_limits<int>::max())
+ return Max();
+ return TimeDelta(minutes * Time::kMicrosecondsPerMinute);
+}
+
+// static
+inline TimeDelta TimeDelta::FromSeconds(int64_t secs) {
+ return TimeDelta(secs) * Time::kMicrosecondsPerSecond;
+}
+
+// static
+inline TimeDelta TimeDelta::FromMilliseconds(int64_t ms) {
+ return TimeDelta(ms) * Time::kMicrosecondsPerMillisecond;
+}
+
+// static
+inline TimeDelta TimeDelta::FromSecondsD(double secs) {
+ return FromDouble(secs * Time::kMicrosecondsPerSecond);
+}
+
+// static
+inline TimeDelta TimeDelta::FromMillisecondsD(double ms) {
+ return FromDouble(ms * Time::kMicrosecondsPerMillisecond);
+}
+
+// static
+inline TimeDelta TimeDelta::FromMicroseconds(int64_t us) {
+ return TimeDelta(us);
+}
+
+// static
+inline TimeDelta TimeDelta::FromDouble(double value) {
+ double max_magnitude = std::numeric_limits<int64_t>::max();
+ TimeDelta delta = TimeDelta(static_cast<int64_t>(value));
+ if (value > max_magnitude)
+ delta = Max();
+ else if (value < -max_magnitude)
+ delta = -Max();
+ return delta;
+}
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, Time time);
+
+// TimeTicks ------------------------------------------------------------------
+
+// Represents monotonically non-decreasing clock time.
+class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
+ public:
+ TimeTicks() : TimeBase(0) {
+ }
+
+ // Platform-dependent tick count representing "right now." When
+ // IsHighResolution() returns false, the resolution of the clock could be
+ // as coarse as ~15.6ms. Otherwise, the resolution should be no worse than one
+ // microsecond.
+ static TimeTicks Now();
+
+ // Returns true if the high resolution clock is working on this system and
+ // Now() will return high resolution values. Note that, on systems where the
+ // high resolution clock works but is deemed inefficient, the low resolution
+ // clock will be used instead.
+ static bool IsHighResolution();
+
+#if defined(OS_WIN)
+ // Translates an absolute QPC timestamp into a TimeTicks value. The returned
+ // value has the same origin as Now(). Do NOT attempt to use this if
+ // IsHighResolution() returns false.
+ static TimeTicks FromQPCValue(LONGLONG qpc_value);
+#endif
+
+ // Get an estimate of the TimeTick value at the time of the UnixEpoch. Because
+ // Time and TimeTicks respond differently to user-set time and NTP
+ // adjustments, this number is only an estimate. Nevertheless, this can be
+ // useful when you need to relate the value of TimeTicks to a real time and
+ // date. Note: Upon first invocation, this function takes a snapshot of the
+ // realtime clock to establish a reference point. This function will return
+ // the same value for the duration of the application, but will be different
+ // in future application runs.
+ static TimeTicks UnixEpoch();
+
+ // Returns |this| snapped to the next tick, given a |tick_phase| and
+ // repeating |tick_interval| in both directions. |this| may be before,
+ // after, or equal to the |tick_phase|.
+ TimeTicks SnappedToNextTick(TimeTicks tick_phase,
+ TimeDelta tick_interval) const;
+
+#if defined(OS_WIN)
+ protected:
+ typedef DWORD (*TickFunctionType)(void);
+ static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
+#endif
+
+ private:
+ friend class time_internal::TimeBase<TimeTicks>;
+
+ // Please use Now() to create a new object. This is for internal use
+ // and testing.
+ explicit TimeTicks(int64_t us) : TimeBase(us) {}
+};
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeTicks time_ticks);
+
+// ThreadTicks ----------------------------------------------------------------
+
+// Represents a clock, specific to a particular thread, than runs only while the
+// thread is running.
+class BASE_EXPORT ThreadTicks : public time_internal::TimeBase<ThreadTicks> {
+ public:
+ ThreadTicks() : TimeBase(0) {
+ }
+
+ // Returns true if ThreadTicks::Now() is supported on this system.
+ static bool IsSupported() {
+#if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
+ (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_ANDROID)
+ return true;
+#elif defined(OS_WIN)
+ return IsSupportedWin();
+#else
+ return false;
+#endif
+ }
+
+ // Waits until the initialization is completed. Needs to be guarded with a
+ // call to IsSupported().
+ static void WaitUntilInitialized() {
+#if defined(OS_WIN)
+ WaitUntilInitializedWin();
+#endif
+ }
+
+ // Returns thread-specific CPU-time on systems that support this feature.
+ // Needs to be guarded with a call to IsSupported(). Use this timer
+ // to (approximately) measure how much time the calling thread spent doing
+ // actual work vs. being de-scheduled. May return bogus results if the thread
+ // migrates to another CPU between two calls. Returns an empty ThreadTicks
+ // object until the initialization is completed. If a clock reading is
+ // absolutely needed, call WaitUntilInitialized() before this method.
+ static ThreadTicks Now();
+
+ private:
+ friend class time_internal::TimeBase<ThreadTicks>;
+
+ // Please use Now() to create a new object. This is for internal use
+ // and testing.
+ explicit ThreadTicks(int64_t us) : TimeBase(us) {}
+
+#if defined(OS_WIN)
+ FRIEND_TEST_ALL_PREFIXES(TimeTicks, TSCTicksPerSecond);
+
+ // Returns the frequency of the TSC in ticks per second, or 0 if it hasn't
+ // been measured yet. Needs to be guarded with a call to IsSupported().
+ // This method is declared here rather than in the anonymous namespace to
+ // allow testing.
+ static double TSCTicksPerSecond();
+
+ static bool IsSupportedWin();
+ static void WaitUntilInitializedWin();
+#endif
+};
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, ThreadTicks time_ticks);
+
+} // namespace base
+
+#endif // BASE_TIME_TIME_H_