client/base/time.h

/*
  Copyright 2014 Google Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
*/

// Time represents an absolute point in time, internally represented as
// microseconds (s/1,000,000) since a platform-dependent epoch.  Each
// platform's epoch, along with other system-dependent clock interface
// routines, is defined in time_PLATFORM.cc.
//
// TimeDelta represents a duration of time, internally represented in
// microseconds.
//
// TimeTicks represents an abstract time that is always incrementing for use
// in measuring time durations. It is internally represented in microseconds.
// It can not be converted to a human-readable time, but is guaranteed not to
// decrease (if the user changes the computer clock, Time::Now() may actually
// decrease or jump).
//
// These classes are represented as only a 64-bit value, so they can be
// efficiently passed by value.

#ifndef GOOPY_BASE_TIME_H_
#define GOOPY_BASE_TIME_H_
#pragma once

#include <time.h>

#if defined(OS_POSIX)
// For struct timeval.
#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>
#endif

#include "base/basictypes.h"

namespace base {

class Time;
class TimeTicks;

// This unit test does a lot of manual time manipulation.
class PageLoadTrackerUnitTest;

// TimeDelta ------------------------------------------------------------------

class TimeDelta {
 public:
  TimeDelta() : delta_(0) {
  }

  // Converts units of time to TimeDeltas.
  static TimeDelta FromDays(int64 days);
  static TimeDelta FromHours(int64 hours);
  static TimeDelta FromMinutes(int64 minutes);
  static TimeDelta FromSeconds(int64 secs);
  static TimeDelta FromMilliseconds(int64 ms);
  static TimeDelta FromMicroseconds(int64 us);

  // 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.
  int64 ToInternalValue() const {
    return delta_;
  }

#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 InSeconds() const;
  double InMillisecondsF() const;
  int64 InMilliseconds() const;
  int64 InMillisecondsRoundedUp() const;
  int64 InMicroseconds() const;

  TimeDelta& operator=(TimeDelta other) {
    delta_ = other.delta_;
    return *this;
  }

  // Computations with other deltas.
  TimeDelta operator+(TimeDelta other) const {
    return TimeDelta(delta_ + other.delta_);
  }
  TimeDelta operator-(TimeDelta other) const {
    return TimeDelta(delta_ - other.delta_);
  }

  TimeDelta& operator+=(TimeDelta other) {
    delta_ += other.delta_;
    return *this;
  }
  TimeDelta& operator-=(TimeDelta other) {
    delta_ -= other.delta_;
    return *this;
  }
  TimeDelta operator-() const {
    return TimeDelta(-delta_);
  }

  // Computations with ints, note that we only allow multiplicative operations
  // with ints, and additive operations with other deltas.
  TimeDelta operator*(int64 a) const {
    return TimeDelta(delta_ * a);
  }
  TimeDelta operator/(int64 a) const {
    return TimeDelta(delta_ / a);
  }
  TimeDelta& operator*=(int64 a) {
    delta_ *= a;
    return *this;
  }
  TimeDelta& operator/=(int64 a) {
    delta_ /= a;
    return *this;
  }
  int64 operator/(TimeDelta a) const {
    return delta_ / a.delta_;
  }

  // Defined below because it depends on the definition of the other classes.
  Time operator+(Time t) const;
  TimeTicks operator+(TimeTicks t) const;

  // 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 class Time;
  friend class TimeTicks;
  friend TimeDelta operator*(int64 a, TimeDelta td);

  // 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 delta_us) : delta_(delta_us) {
  }

  // Delta in microseconds.
  int64 delta_;
};

inline TimeDelta operator*(int64 a, TimeDelta td) {
  return TimeDelta(a * td.delta_);
}

// Time -----------------------------------------------------------------------

// Represents a wall clock time.
class Time {
 public:
  static const int64 kMillisecondsPerSecond = 1000;
  static const int64 kMicrosecondsPerMillisecond = 1000;
  static const int64 kMicrosecondsPerSecond = kMicrosecondsPerMillisecond *
                                              kMillisecondsPerSecond;
  static const int64 kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
  static const int64 kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
  static const int64 kMicrosecondsPerDay = kMicrosecondsPerHour * 24;
  static const int64 kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
  static const int64 kNanosecondsPerMicrosecond = 1000;
  static const int64 kNanosecondsPerSecond = kNanosecondsPerMicrosecond *
                                             kMicrosecondsPerSecond;

#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 kWindowsEpochDeltaMicroseconds;
#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 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.
  explicit Time() : us_(0) {
  }

  // Returns true if the time object has not been initialized.
  bool is_null() const {
    return us_ == 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 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)
  struct timeval ToTimeVal() 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. If the high resolution
  // timer is not enabled, calls to ActivateHighResolutionTimer will fail.
  // When disabling the high resolution timer, this function will not cause
  // the high resolution timer to be deactivated, but will prevent future
  // activations.
  // Must be called from the main thread.
  // For more details see comments in time_win.cc.
  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.
  // All callers to activate the high resolution timer must eventually call
  // this function to deactivate the high resolution timer.
  static bool ActivateHighResolutionTimer(bool activate);
#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);
  }

  // Converts an integer value representing Time to a class. This is used
  // when deserializing a |Time| 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 Time FromInternalValue(int64 us) {
    return Time(us);
  }

  // For serializing, 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 ToInternalValue() const {
    return us_;
  }

  // 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;

  Time& operator=(Time other) {
    us_ = other.us_;
    return *this;
  }

  // Compute the difference between two times.
  TimeDelta operator-(Time other) const {
    return TimeDelta(us_ - other.us_);
  }

  // Modify by some time delta.
  Time& operator+=(TimeDelta delta) {
    us_ += delta.delta_;
    return *this;
  }
  Time& operator-=(TimeDelta delta) {
    us_ -= delta.delta_;
    return *this;
  }

  // Return a new time modified by some delta.
  Time operator+(TimeDelta delta) const {
    return Time(us_ + delta.delta_);
  }
  Time operator-(TimeDelta delta) const {
    return Time(us_ - delta.delta_);
  }

  // Comparison operators
  bool operator==(Time other) const {
    return us_ == other.us_;
  }
  bool operator!=(Time other) const {
    return us_ != other.us_;
  }
  bool operator<(Time other) const {
    return us_ < other.us_;
  }
  bool operator<=(Time other) const {
    return us_ <= other.us_;
  }
  bool operator>(Time other) const {
    return us_ > other.us_;
  }
  bool operator>=(Time other) const {
    return us_ >= other.us_;
  }

 private:
  friend class TimeDelta;

  explicit Time(int64 us) : us_(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);

  // The representation of Jan 1, 1970 UTC in microseconds since the
  // platform-dependent epoch.
  static const int64 kTimeTToMicrosecondsOffset;

#if defined(OS_WIN)
  // Indicates whether fast timers are usable right now.  For instance,
  // when using battery power, we might elect to prevent high speed timers
  // which would draw more power.
  static bool high_resolution_timer_enabled_;
#endif

  // Time in microseconds in UTC.
  int64 us_;
};

// Inline the TimeDelta factory methods, for fast TimeDelta construction.

// static
inline TimeDelta TimeDelta::FromDays(int64 days) {
  return TimeDelta(days * Time::kMicrosecondsPerDay);
}

// static
inline TimeDelta TimeDelta::FromHours(int64 hours) {
  return TimeDelta(hours * Time::kMicrosecondsPerHour);
}

// static
inline TimeDelta TimeDelta::FromMinutes(int64 minutes) {
  return TimeDelta(minutes * Time::kMicrosecondsPerMinute);
}

// static
inline TimeDelta TimeDelta::FromSeconds(int64 secs) {
  return TimeDelta(secs * Time::kMicrosecondsPerSecond);
}

// static
inline TimeDelta TimeDelta::FromMilliseconds(int64 ms) {
  return TimeDelta(ms * Time::kMicrosecondsPerMillisecond);
}

// static
inline TimeDelta TimeDelta::FromMicroseconds(int64 us) {
  return TimeDelta(us);
}

inline Time TimeDelta::operator+(Time t) const {
  return Time(t.us_ + delta_);
}

// TimeTicks ------------------------------------------------------------------

class TimeTicks {
 public:
  TimeTicks() : ticks_(0) {
  }

  // Platform-dependent tick count representing "right now."
  // The resolution of this clock is ~1-15ms.  Resolution varies depending
  // on hardware/operating system configuration.
  static TimeTicks Now();

  // Returns a platform-dependent high-resolution tick count. Implementation
  // is hardware dependent and may or may not return sub-millisecond
  // resolution.  THIS CALL IS GENERALLY MUCH MORE EXPENSIVE THAN Now() AND
  // SHOULD ONLY BE USED WHEN IT IS REALLY NEEDED.
  static TimeTicks HighResNow();

#if defined(OS_WIN)
  // Get the absolute value of QPC time drift. For testing.
  static int64 GetQPCDriftMicroseconds();

  // Returns true if the high resolution clock is working on this system.
  // This is only for testing.
  static bool IsHighResClockWorking();
#endif

  // Returns true if this object has not been initialized.
  bool is_null() const {
    return ticks_ == 0;
  }

  // Returns the internal numeric value of the TimeTicks object.
  int64 ToInternalValue() const {
    return ticks_;
  }

  TimeTicks& operator=(TimeTicks other) {
    ticks_ = other.ticks_;
    return *this;
  }

  // Compute the difference between two times.
  TimeDelta operator-(TimeTicks other) const {
    return TimeDelta(ticks_ - other.ticks_);
  }

  // Modify by some time delta.
  TimeTicks& operator+=(TimeDelta delta) {
    ticks_ += delta.delta_;
    return *this;
  }
  TimeTicks& operator-=(TimeDelta delta) {
    ticks_ -= delta.delta_;
    return *this;
  }

  // Return a new TimeTicks modified by some delta.
  TimeTicks operator+(TimeDelta delta) const {
    return TimeTicks(ticks_ + delta.delta_);
  }
  TimeTicks operator-(TimeDelta delta) const {
    return TimeTicks(ticks_ - delta.delta_);
  }

  // Comparison operators
  bool operator==(TimeTicks other) const {
    return ticks_ == other.ticks_;
  }
  bool operator!=(TimeTicks other) const {
    return ticks_ != other.ticks_;
  }
  bool operator<(TimeTicks other) const {
    return ticks_ < other.ticks_;
  }
  bool operator<=(TimeTicks other) const {
    return ticks_ <= other.ticks_;
  }
  bool operator>(TimeTicks other) const {
    return ticks_ > other.ticks_;
  }
  bool operator>=(TimeTicks other) const {
    return ticks_ >= other.ticks_;
  }

 protected:
  friend class TimeDelta;
  friend class PageLoadTrackerUnitTest;

  // Please use Now() to create a new object. This is for internal use
  // and testing. Ticks is in microseconds.
  explicit TimeTicks(int64 ticks) : ticks_(ticks) {
  }

  // Tick count in microseconds.
  int64 ticks_;

#if defined(OS_WIN)
  typedef DWORD (*TickFunctionType)(void);
  static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
#endif
};

inline TimeTicks TimeDelta::operator+(TimeTicks t) const {
  return TimeTicks(t.ticks_ + delta_);
}

}  // namespace base

#endif  // GOOPY_BASE_TIME_H_