michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_TimeStamp_h
michael@0: #define mozilla_TimeStamp_h
michael@0: 
michael@0: #include <stdint.h>
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/Attributes.h"
michael@0: #include "nscore.h"
michael@0: 
michael@0: namespace IPC {
michael@0: template <typename T> struct ParamTraits;
michael@0: }
michael@0: 
michael@0: #ifdef XP_WIN
michael@0: // defines TimeStampValue as a complex value keeping both
michael@0: // GetTickCount and QueryPerformanceCounter values
michael@0: #include "TimeStamp_windows.h"
michael@0: #endif
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: #ifndef XP_WIN
michael@0: typedef uint64_t TimeStampValue;
michael@0: #endif
michael@0: 
michael@0: class TimeStamp;
michael@0: 
michael@0: /**
michael@0:  * Instances of this class represent the length of an interval of time.
michael@0:  * Negative durations are allowed, meaning the end is before the start.
michael@0:  * 
michael@0:  * Internally the duration is stored as a int64_t in units of
michael@0:  * PR_TicksPerSecond() when building with NSPR interval timers, or a
michael@0:  * system-dependent unit when building with system clocks.  The
michael@0:  * system-dependent unit must be constant, otherwise the semantics of
michael@0:  * this class would be broken.
michael@0:  */
michael@0: class TimeDuration
michael@0: {
michael@0: public:
michael@0:   // The default duration is 0.
michael@0:   MOZ_CONSTEXPR TimeDuration() : mValue(0) {}
michael@0:   // Allow construction using '0' as the initial value, for readability,
michael@0:   // but no other numbers (so we don't have any implicit unit conversions).
michael@0:   struct _SomethingVeryRandomHere;
michael@0:   TimeDuration(_SomethingVeryRandomHere* aZero) : mValue(0) {
michael@0:     MOZ_ASSERT(!aZero, "Who's playing funny games here?");
michael@0:   }
michael@0:   // Default copy-constructor and assignment are OK
michael@0: 
michael@0:   double ToSeconds() const;
michael@0:   // Return a duration value that includes digits of time we think to
michael@0:   // be significant.  This method should be used when displaying a
michael@0:   // time to humans.
michael@0:   double ToSecondsSigDigits() const;
michael@0:   double ToMilliseconds() const {
michael@0:     return ToSeconds() * 1000.0;
michael@0:   }
michael@0:   double ToMicroseconds() const {
michael@0:     return ToMilliseconds() * 1000.0;
michael@0:   }
michael@0: 
michael@0:   // Using a double here is safe enough; with 53 bits we can represent
michael@0:   // durations up to over 280,000 years exactly.  If the units of
michael@0:   // mValue do not allow us to represent durations of that length,
michael@0:   // long durations are clamped to the max/min representable value
michael@0:   // instead of overflowing.
michael@0:   static inline TimeDuration FromSeconds(double aSeconds) {
michael@0:     return FromMilliseconds(aSeconds * 1000.0);
michael@0:   }
michael@0:   static TimeDuration FromMilliseconds(double aMilliseconds);
michael@0:   static inline TimeDuration FromMicroseconds(double aMicroseconds) {
michael@0:     return FromMilliseconds(aMicroseconds / 1000.0);
michael@0:   }
michael@0: 
michael@0:   static TimeDuration Forever() {
michael@0:     return FromTicks(INT64_MAX);
michael@0:   }
michael@0: 
michael@0:   TimeDuration operator+(const TimeDuration& aOther) const {
michael@0:     return TimeDuration::FromTicks(mValue + aOther.mValue);
michael@0:   }
michael@0:   TimeDuration operator-(const TimeDuration& aOther) const {
michael@0:     return TimeDuration::FromTicks(mValue - aOther.mValue);
michael@0:   }
michael@0:   TimeDuration& operator+=(const TimeDuration& aOther) {
michael@0:     mValue += aOther.mValue;
michael@0:     return *this;
michael@0:   }
michael@0:   TimeDuration& operator-=(const TimeDuration& aOther) {
michael@0:     mValue -= aOther.mValue;
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   // Block double multiplier (slower, imprecise if long duration) - Bug 853398.
michael@0:   // If required, use MultDouble explicitly and with care.
michael@0:   TimeDuration operator*(const double aMultiplier) const MOZ_DELETE;
michael@0: 
michael@0: public:
michael@0:   TimeDuration MultDouble(double aMultiplier) const {
michael@0:     return TimeDuration::FromTicks(static_cast<int64_t>(mValue * aMultiplier));
michael@0:   }
michael@0:   TimeDuration operator*(const int32_t aMultiplier) const {
michael@0:     return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
michael@0:   }
michael@0:   TimeDuration operator*(const uint32_t aMultiplier) const {
michael@0:     return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
michael@0:   }
michael@0:   TimeDuration operator*(const int64_t aMultiplier) const {
michael@0:     return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
michael@0:   }
michael@0:   TimeDuration operator/(const int64_t aDivisor) const {
michael@0:     return TimeDuration::FromTicks(mValue / aDivisor);
michael@0:   }
michael@0:   double operator/(const TimeDuration& aOther) const {
michael@0:     return static_cast<double>(mValue) / aOther.mValue;
michael@0:   }
michael@0: 
michael@0:   bool operator<(const TimeDuration& aOther) const {
michael@0:     return mValue < aOther.mValue;
michael@0:   }
michael@0:   bool operator<=(const TimeDuration& aOther) const {
michael@0:     return mValue <= aOther.mValue;
michael@0:   }
michael@0:   bool operator>=(const TimeDuration& aOther) const {
michael@0:     return mValue >= aOther.mValue;
michael@0:   }
michael@0:   bool operator>(const TimeDuration& aOther) const {
michael@0:     return mValue > aOther.mValue;
michael@0:   }
michael@0:   bool operator==(const TimeDuration& aOther) const {
michael@0:     return mValue == aOther.mValue;
michael@0:   }
michael@0: 
michael@0:   // Return a best guess at the system's current timing resolution,
michael@0:   // which might be variable.  TimeDurations below this order of
michael@0:   // magnitude are meaningless, and those at the same order of
michael@0:   // magnitude or just above are suspect.
michael@0:   static TimeDuration Resolution();
michael@0: 
michael@0:   // We could define additional operators here:
michael@0:   // -- convert to/from other time units
michael@0:   // -- scale duration by a float
michael@0:   // but let's do that on demand.
michael@0:   // Comparing durations for equality will only lead to bugs on
michael@0:   // platforms with high-resolution timers.
michael@0: 
michael@0: private:
michael@0:   friend class TimeStamp;
michael@0:   friend struct IPC::ParamTraits<mozilla::TimeDuration>;
michael@0: 
michael@0:   static TimeDuration FromTicks(int64_t aTicks) {
michael@0:     TimeDuration t;
michael@0:     t.mValue = aTicks;
michael@0:     return t;
michael@0:   }
michael@0: 
michael@0:   static TimeDuration FromTicks(double aTicks) {
michael@0:     // NOTE: this MUST be a >= test, because int64_t(double(INT64_MAX))
michael@0:     // overflows and gives INT64_MIN.
michael@0:     if (aTicks >= double(INT64_MAX))
michael@0:       return TimeDuration::FromTicks(INT64_MAX);
michael@0: 
michael@0:     // This MUST be a <= test.
michael@0:     if (aTicks <= double(INT64_MIN))
michael@0:       return TimeDuration::FromTicks(INT64_MIN);
michael@0: 
michael@0:     return TimeDuration::FromTicks(int64_t(aTicks));
michael@0:   }
michael@0: 
michael@0:   // Duration, result is implementation-specific difference of two TimeStamps
michael@0:   int64_t mValue;
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * Instances of this class represent moments in time, or a special
michael@0:  * "null" moment. We do not use the non-monotonic system clock or
michael@0:  * local time, since they can be reset, causing apparent backward
michael@0:  * travel in time, which can confuse algorithms. Instead we measure
michael@0:  * elapsed time according to the system.  This time can never go
michael@0:  * backwards (i.e. it never wraps around, at least not in less than
michael@0:  * five million years of system elapsed time). It might not advance
michael@0:  * while the system is sleeping. If TimeStamp::SetNow() is not called
michael@0:  * at all for hours or days, we might not notice the passage of some
michael@0:  * of that time.
michael@0:  * 
michael@0:  * We deliberately do not expose a way to convert TimeStamps to some
michael@0:  * particular unit. All you can do is compute a difference between two
michael@0:  * TimeStamps to get a TimeDuration. You can also add a TimeDuration
michael@0:  * to a TimeStamp to get a new TimeStamp. You can't do something
michael@0:  * meaningless like add two TimeStamps.
michael@0:  *
michael@0:  * Internally this is implemented as either a wrapper around
michael@0:  *   - high-resolution, monotonic, system clocks if they exist on this
michael@0:  *     platform
michael@0:  *   - PRIntervalTime otherwise.  We detect wraparounds of
michael@0:  *     PRIntervalTime and work around them.
michael@0:  *
michael@0:  * This class is similar to C++11's time_point, however it is
michael@0:  * explicitly nullable and provides an IsNull() method. time_point
michael@0:  * is initialized to the clock's epoch and provides a
michael@0:  * time_since_epoch() method that functions similiarly. i.e.
michael@0:  * t.IsNull() is equivalent to t.time_since_epoch() == decltype(t)::duration::zero();
michael@0:  */
michael@0: class TimeStamp
michael@0: {
michael@0: public:
michael@0:   /**
michael@0:    * Initialize to the "null" moment
michael@0:    */
michael@0:   MOZ_CONSTEXPR TimeStamp() : mValue(0) {}
michael@0:   // Default copy-constructor and assignment are OK
michael@0: 
michael@0:   /**
michael@0:    * Return true if this is the "null" moment
michael@0:    */
michael@0:   bool IsNull() const { return mValue == 0; }
michael@0:   /**
michael@0:    * Return a timestamp reflecting the current elapsed system time. This
michael@0:    * is monotonically increasing (i.e., does not decrease) over the
michael@0:    * lifetime of this process' XPCOM session.
michael@0:    *
michael@0:    * Now() is trying to ensure the best possible precision on each platform,
michael@0:    * at least one millisecond.
michael@0:    *
michael@0:    * NowLoRes() has been introduced to workaround performance problems of
michael@0:    * QueryPerformanceCounter on the Windows platform.  NowLoRes() is giving
michael@0:    * lower precision, usually 15.6 ms, but with very good performance benefit.
michael@0:    * Use it for measurements of longer times, like >200ms timeouts.
michael@0:    */
michael@0:   static TimeStamp Now() { return Now(true); }
michael@0:   static TimeStamp NowLoRes() { return Now(false); }
michael@0: 
michael@0:   /**
michael@0:    * Return a timestamp representing the time when the current process was
michael@0:    * created which will be comparable with other timestamps taken with this
michael@0:    * class. If the actual process creation time is detected to be inconsistent
michael@0:    * the @a aIsInconsistent parameter will be set to true, the returned
michael@0:    * timestamp however will still be valid though inaccurate.
michael@0:    *
michael@0:    * @param aIsInconsistent Set to true if an inconsistency was detected in the
michael@0:    * process creation time
michael@0:    * @returns A timestamp representing the time when the process was created,
michael@0:    * this timestamp is always valid even when errors are reported
michael@0:    */
michael@0:   static TimeStamp ProcessCreation(bool& aIsInconsistent);
michael@0: 
michael@0:   /**
michael@0:    * Records a process restart. After this call ProcessCreation() will return
michael@0:    * the time when the browser was restarted instead of the actual time when
michael@0:    * the process was created.
michael@0:    */
michael@0:   static void RecordProcessRestart();
michael@0: 
michael@0:   /**
michael@0:    * Compute the difference between two timestamps. Both must be non-null.
michael@0:    */
michael@0:   TimeDuration operator-(const TimeStamp& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     static_assert(-INT64_MAX > INT64_MIN, "int64_t sanity check");
michael@0:     int64_t ticks = int64_t(mValue - aOther.mValue);
michael@0:     // Check for overflow.
michael@0:     if (mValue > aOther.mValue) {
michael@0:       if (ticks < 0) {
michael@0:         ticks = INT64_MAX;
michael@0:       }
michael@0:     } else {
michael@0:       if (ticks > 0) {
michael@0:         ticks = INT64_MIN;
michael@0:       }
michael@0:     }
michael@0:     return TimeDuration::FromTicks(ticks);
michael@0:   }
michael@0: 
michael@0:   TimeStamp operator+(const TimeDuration& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     return TimeStamp(mValue + aOther.mValue);
michael@0:   }
michael@0:   TimeStamp operator-(const TimeDuration& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     return TimeStamp(mValue - aOther.mValue);
michael@0:   }
michael@0:   TimeStamp& operator+=(const TimeDuration& aOther) {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     mValue += aOther.mValue;
michael@0:     return *this;
michael@0:   }
michael@0:   TimeStamp& operator-=(const TimeDuration& aOther) {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     mValue -= aOther.mValue;
michael@0:     return *this;
michael@0:   }
michael@0: 
michael@0:   bool operator<(const TimeStamp& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue < aOther.mValue;
michael@0:   }
michael@0:   bool operator<=(const TimeStamp& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue <= aOther.mValue;
michael@0:   }
michael@0:   bool operator>=(const TimeStamp& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue >= aOther.mValue;
michael@0:   }
michael@0:   bool operator>(const TimeStamp& aOther) const {
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue > aOther.mValue;
michael@0:   }
michael@0:   bool operator==(const TimeStamp& aOther) const {
michael@0:     // Maybe it's ok to check == with null timestamps?
michael@0:     MOZ_ASSERT(!IsNull() && "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue == aOther.mValue;
michael@0:   }
michael@0:   bool operator!=(const TimeStamp& aOther) const {
michael@0:     // Maybe it's ok to check != with null timestamps?
michael@0:     MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
michael@0:     MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
michael@0:     return mValue != aOther.mValue;
michael@0:   }
michael@0: 
michael@0:   // Comparing TimeStamps for equality should be discouraged. Adding
michael@0:   // two TimeStamps, or scaling TimeStamps, is nonsense and must never
michael@0:   // be allowed.
michael@0: 
michael@0:   static NS_HIDDEN_(nsresult) Startup();
michael@0:   static NS_HIDDEN_(void) Shutdown();
michael@0: 
michael@0: private:
michael@0:   friend struct IPC::ParamTraits<mozilla::TimeStamp>;
michael@0:   friend void StartupTimelineRecordExternal(int, uint64_t);
michael@0: 
michael@0:   TimeStamp(TimeStampValue aValue) : mValue(aValue) {}
michael@0: 
michael@0:   static TimeStamp Now(bool aHighResolution);
michael@0: 
michael@0:   /**
michael@0:    * Computes the uptime of the current process in microseconds. The result
michael@0:    * is platform-dependent and needs to be checked against existing timestamps
michael@0:    * for consistency.
michael@0:    *
michael@0:    * @returns The number of microseconds since the calling process was started
michael@0:    *          or 0 if an error was encountered while computing the uptime
michael@0:    */
michael@0:   static uint64_t ComputeProcessUptime();
michael@0: 
michael@0:   /**
michael@0:    * When built with PRIntervalTime, a value of 0 means this instance
michael@0:    * is "null". Otherwise, the low 32 bits represent a PRIntervalTime,
michael@0:    * and the high 32 bits represent a counter of the number of
michael@0:    * rollovers of PRIntervalTime that we've seen. This counter starts
michael@0:    * at 1 to avoid a real time colliding with the "null" value.
michael@0:    * 
michael@0:    * PR_INTERVAL_MAX is set at 100,000 ticks per second. So the minimum
michael@0:    * time to wrap around is about 2^64/100000 seconds, i.e. about
michael@0:    * 5,849,424 years.
michael@0:    *
michael@0:    * When using a system clock, a value is system dependent.
michael@0:    */
michael@0:   TimeStampValue mValue;
michael@0: };
michael@0: 
michael@0: }
michael@0: 
michael@0: #endif /* mozilla_TimeStamp_h */