1 files changed, 575 insertions, 0 deletions
diff --git a/mozglue/misc/TimeStamp.h b/mozglue/misc/TimeStamp.h
new file mode 100644
index 0000000000..ece1fc65b5
--- /dev/null
+++ b/mozglue/misc/TimeStamp.h
@@ -0,0 +1,575 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_TimeStamp_h
+#define mozilla_TimeStamp_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Types.h"
+#include <algorithm>  // for std::min, std::max
+#include <ostream>
+#include <stdint.h>
+#include <type_traits>
+
+namespace IPC {
+template <typename T>
+struct ParamTraits;
+}  // namespace IPC
+
+#ifdef XP_WIN
+// defines TimeStampValue as a complex value keeping both
+// GetTickCount and QueryPerformanceCounter values
+#  include "TimeStamp_windows.h"
+#endif
+
+namespace mozilla {
+
+#ifndef XP_WIN
+typedef uint64_t TimeStampValue;
+#endif
+
+class TimeStamp;
+
+/**
+ * Platform-specific implementation details of BaseTimeDuration.
+ */
+class BaseTimeDurationPlatformUtils {
+ public:
+  static MFBT_API double ToSeconds(int64_t aTicks);
+  static MFBT_API double ToSecondsSigDigits(int64_t aTicks);
+  static MFBT_API int64_t TicksFromMilliseconds(double aMilliseconds);
+  static MFBT_API int64_t ResolutionInTicks();
+};
+
+/**
+ * Instances of this class represent the length of an interval of time.
+ * Negative durations are allowed, meaning the end is before the start.
+ *
+ * Internally the duration is stored as a int64_t in units of
+ * PR_TicksPerSecond() when building with NSPR interval timers, or a
+ * system-dependent unit when building with system clocks.  The
+ * system-dependent unit must be constant, otherwise the semantics of
+ * this class would be broken.
+ *
+ * The ValueCalculator template parameter determines how arithmetic
+ * operations are performed on the integer count of ticks (mValue).
+ */
+template <typename ValueCalculator>
+class BaseTimeDuration {
+ public:
+  // The default duration is 0.
+  constexpr BaseTimeDuration() : mValue(0) {}
+  // Allow construction using '0' as the initial value, for readability,
+  // but no other numbers (so we don't have any implicit unit conversions).
+  struct _SomethingVeryRandomHere;
+  MOZ_IMPLICIT BaseTimeDuration(_SomethingVeryRandomHere* aZero) : mValue(0) {
+    MOZ_ASSERT(!aZero, "Who's playing funny games here?");
+  }
+  // Default copy-constructor and assignment are OK
+
+  // Converting copy-constructor and assignment operator
+  template <typename E>
+  explicit BaseTimeDuration(const BaseTimeDuration<E>& aOther)
+      : mValue(aOther.mValue) {}
+
+  template <typename E>
+  BaseTimeDuration& operator=(const BaseTimeDuration<E>& aOther) {
+    mValue = aOther.mValue;
+    return *this;
+  }
+
+  double ToSeconds() const {
+    if (mValue == INT64_MAX) {
+      return PositiveInfinity<double>();
+    }
+    if (mValue == INT64_MIN) {
+      return NegativeInfinity<double>();
+    }
+    return BaseTimeDurationPlatformUtils::ToSeconds(mValue);
+  }
+  // Return a duration value that includes digits of time we think to
+  // be significant.  This method should be used when displaying a
+  // time to humans.
+  double ToSecondsSigDigits() const {
+    if (mValue == INT64_MAX) {
+      return PositiveInfinity<double>();
+    }
+    if (mValue == INT64_MIN) {
+      return NegativeInfinity<double>();
+    }
+    return BaseTimeDurationPlatformUtils::ToSecondsSigDigits(mValue);
+  }
+  double ToMilliseconds() const { return ToSeconds() * 1000.0; }
+  double ToMicroseconds() const { return ToMilliseconds() * 1000.0; }
+
+  // Using a double here is safe enough; with 53 bits we can represent
+  // durations up to over 280,000 years exactly.  If the units of
+  // mValue do not allow us to represent durations of that length,
+  // long durations are clamped to the max/min representable value
+  // instead of overflowing.
+  static inline BaseTimeDuration FromSeconds(double aSeconds) {
+    return FromMilliseconds(aSeconds * 1000.0);
+  }
+  static BaseTimeDuration FromMilliseconds(double aMilliseconds) {
+    if (aMilliseconds == PositiveInfinity<double>()) {
+      return Forever();
+    }
+    if (aMilliseconds == NegativeInfinity<double>()) {
+      return FromTicks(INT64_MIN);
+    }
+    return FromTicks(
+        BaseTimeDurationPlatformUtils::TicksFromMilliseconds(aMilliseconds));
+  }
+  static inline BaseTimeDuration FromMicroseconds(double aMicroseconds) {
+    return FromMilliseconds(aMicroseconds / 1000.0);
+  }
+
+  static constexpr BaseTimeDuration Forever() { return FromTicks(INT64_MAX); }
+
+  BaseTimeDuration operator+(const BaseTimeDuration& aOther) const {
+    return FromTicks(ValueCalculator::Add(mValue, aOther.mValue));
+  }
+  BaseTimeDuration operator-(const BaseTimeDuration& aOther) const {
+    return FromTicks(ValueCalculator::Subtract(mValue, aOther.mValue));
+  }
+  BaseTimeDuration& operator+=(const BaseTimeDuration& aOther) {
+    mValue = ValueCalculator::Add(mValue, aOther.mValue);
+    return *this;
+  }
+  BaseTimeDuration& operator-=(const BaseTimeDuration& aOther) {
+    mValue = ValueCalculator::Subtract(mValue, aOther.mValue);
+    return *this;
+  }
+  BaseTimeDuration operator-() const {
+    // We don't just use FromTicks(ValueCalculator::Subtract(0, mValue))
+    // since that won't give the correct result for -TimeDuration::Forever().
+    int64_t ticks;
+    if (mValue == INT64_MAX) {
+      ticks = INT64_MIN;
+    } else if (mValue == INT64_MIN) {
+      ticks = INT64_MAX;
+    } else {
+      ticks = -mValue;
+    }
+
+    return FromTicks(ticks);
+  }
+
+  static BaseTimeDuration Max(const BaseTimeDuration& aA,
+                              const BaseTimeDuration& aB) {
+    return FromTicks(std::max(aA.mValue, aB.mValue));
+  }
+  static BaseTimeDuration Min(const BaseTimeDuration& aA,
+                              const BaseTimeDuration& aB) {
+    return FromTicks(std::min(aA.mValue, aB.mValue));
+  }
+
+ private:
+  // Block double multiplier (slower, imprecise if long duration) - Bug 853398.
+  // If required, use MultDouble explicitly and with care.
+  BaseTimeDuration operator*(const double aMultiplier) const = delete;
+
+  // Block double divisor (for the same reason, and because dividing by
+  // fractional values would otherwise invoke the int64_t variant, and rounding
+  // the passed argument can then cause divide-by-zero) - Bug 1147491.
+  BaseTimeDuration operator/(const double aDivisor) const = delete;
+
+ public:
+  BaseTimeDuration MultDouble(double aMultiplier) const {
+    return FromTicks(ValueCalculator::Multiply(mValue, aMultiplier));
+  }
+  BaseTimeDuration operator*(const int32_t aMultiplier) const {
+    return FromTicks(ValueCalculator::Multiply(mValue, aMultiplier));
+  }
+  BaseTimeDuration operator*(const uint32_t aMultiplier) const {
+    return FromTicks(ValueCalculator::Multiply(mValue, aMultiplier));
+  }
+  BaseTimeDuration operator*(const int64_t aMultiplier) const {
+    return FromTicks(ValueCalculator::Multiply(mValue, aMultiplier));
+  }
+  BaseTimeDuration operator*(const uint64_t aMultiplier) const {
+    if (aMultiplier > INT64_MAX) {
+      return Forever();
+    }
+    return FromTicks(ValueCalculator::Multiply(mValue, aMultiplier));
+  }
+  BaseTimeDuration operator/(const int64_t aDivisor) const {
+    MOZ_ASSERT(aDivisor != 0, "Division by zero");
+    return FromTicks(ValueCalculator::Divide(mValue, aDivisor));
+  }
+  double operator/(const BaseTimeDuration& aOther) const {
+    MOZ_ASSERT(aOther.mValue != 0, "Division by zero");
+    return ValueCalculator::DivideDouble(mValue, aOther.mValue);
+  }
+  BaseTimeDuration operator%(const BaseTimeDuration& aOther) const {
+    MOZ_ASSERT(aOther.mValue != 0, "Division by zero");
+    return FromTicks(ValueCalculator::Modulo(mValue, aOther.mValue));
+  }
+
+  template <typename E>
+  bool operator<(const BaseTimeDuration<E>& aOther) const {
+    return mValue < aOther.mValue;
+  }
+  template <typename E>
+  bool operator<=(const BaseTimeDuration<E>& aOther) const {
+    return mValue <= aOther.mValue;
+  }
+  template <typename E>
+  bool operator>=(const BaseTimeDuration<E>& aOther) const {
+    return mValue >= aOther.mValue;
+  }
+  template <typename E>
+  bool operator>(const BaseTimeDuration<E>& aOther) const {
+    return mValue > aOther.mValue;
+  }
+  template <typename E>
+  bool operator==(const BaseTimeDuration<E>& aOther) const {
+    return mValue == aOther.mValue;
+  }
+  template <typename E>
+  bool operator!=(const BaseTimeDuration<E>& aOther) const {
+    return mValue != aOther.mValue;
+  }
+  bool IsZero() const { return mValue == 0; }
+  explicit operator bool() const { return mValue != 0; }
+
+  friend std::ostream& operator<<(std::ostream& aStream,
+                                  const BaseTimeDuration& aDuration) {
+    return aStream << aDuration.ToMilliseconds() << " ms";
+  }
+
+  // Return a best guess at the system's current timing resolution,
+  // which might be variable.  BaseTimeDurations below this order of
+  // magnitude are meaningless, and those at the same order of
+  // magnitude or just above are suspect.
+  static BaseTimeDuration Resolution() {
+    return FromTicks(BaseTimeDurationPlatformUtils::ResolutionInTicks());
+  }
+
+  // We could define additional operators here:
+  // -- convert to/from other time units
+  // -- scale duration by a float
+  // but let's do that on demand.
+  // Comparing durations for equality will only lead to bugs on
+  // platforms with high-resolution timers.
+
+ private:
+  friend class TimeStamp;
+  friend struct IPC::ParamTraits<mozilla::BaseTimeDuration<ValueCalculator>>;
+  template <typename>
+  friend class BaseTimeDuration;
+
+  static BaseTimeDuration FromTicks(int64_t aTicks) {
+    BaseTimeDuration t;
+    t.mValue = aTicks;
+    return t;
+  }
+
+  static BaseTimeDuration FromTicks(double aTicks) {
+    // NOTE: this MUST be a >= test, because int64_t(double(INT64_MAX))
+    // overflows and gives INT64_MIN.
+    if (aTicks >= double(INT64_MAX)) {
+      return FromTicks(INT64_MAX);
+    }
+
+    // This MUST be a <= test.
+    if (aTicks <= double(INT64_MIN)) {
+      return FromTicks(INT64_MIN);
+    }
+
+    return FromTicks(int64_t(aTicks));
+  }
+
+  // Duration, result is implementation-specific difference of two TimeStamps
+  int64_t mValue;
+};
+
+/**
+ * Perform arithmetic operations on the value of a BaseTimeDuration without
+ * doing strict checks on the range of values.
+ */
+class TimeDurationValueCalculator {
+ public:
+  static int64_t Add(int64_t aA, int64_t aB) { return aA + aB; }
+  static int64_t Subtract(int64_t aA, int64_t aB) { return aA - aB; }
+
+  template <typename T>
+  static int64_t Multiply(int64_t aA, T aB) {
+    static_assert(std::is_integral_v<T>,
+                  "Using integer multiplication routine with non-integer type."
+                  " Further specialization required");
+    return aA * static_cast<int64_t>(aB);
+  }
+
+  static int64_t Divide(int64_t aA, int64_t aB) { return aA / aB; }
+  static double DivideDouble(int64_t aA, int64_t aB) {
+    return static_cast<double>(aA) / aB;
+  }
+  static int64_t Modulo(int64_t aA, int64_t aB) { return aA % aB; }
+};
+
+template <>
+inline int64_t TimeDurationValueCalculator::Multiply<double>(int64_t aA,
+                                                             double aB) {
+  return static_cast<int64_t>(aA * aB);
+}
+
+/**
+ * Specialization of BaseTimeDuration that uses TimeDurationValueCalculator for
+ * arithmetic on the mValue member.
+ *
+ * Use this class for time durations that are *not* expected to hold values of
+ * Forever (or the negative equivalent) or when such time duration are *not*
+ * expected to be used in arithmetic operations.
+ */
+typedef BaseTimeDuration<TimeDurationValueCalculator> TimeDuration;
+
+/**
+ * Instances of this class represent moments in time, or a special
+ * "null" moment. We do not use the non-monotonic system clock or
+ * local time, since they can be reset, causing apparent backward
+ * travel in time, which can confuse algorithms. Instead we measure
+ * elapsed time according to the system.  This time can never go
+ * backwards (i.e. it never wraps around, at least not in less than
+ * five million years of system elapsed time). It might not advance
+ * while the system is sleeping. If TimeStamp::SetNow() is not called
+ * at all for hours or days, we might not notice the passage of some
+ * of that time.
+ *
+ * We deliberately do not expose a way to convert TimeStamps to some
+ * particular unit. All you can do is compute a difference between two
+ * TimeStamps to get a TimeDuration. You can also add a TimeDuration
+ * to a TimeStamp to get a new TimeStamp. You can't do something
+ * meaningless like add two TimeStamps.
+ *
+ * Internally this is implemented as either a wrapper around
+ *   - high-resolution, monotonic, system clocks if they exist on this
+ *     platform
+ *   - PRIntervalTime otherwise.  We detect wraparounds of
+ *     PRIntervalTime and work around them.
+ *
+ * This class is similar to C++11's time_point, however it is
+ * explicitly nullable and provides an IsNull() method. time_point
+ * is initialized to the clock's epoch and provides a
+ * time_since_epoch() method that functions similiarly. i.e.
+ * t.IsNull() is equivalent to t.time_since_epoch() ==
+ * decltype(t)::duration::zero();
+ *
+ * Note that, since TimeStamp objects are small, prefer to pass them by value
+ * unless there is a specific reason not to do so.
+ */
+class TimeStamp {
+ public:
+  /**
+   * Initialize to the "null" moment
+   */
+  constexpr TimeStamp() : mValue(0) {}
+  // Default copy-constructor and assignment are OK
+
+  /**
+   * The system timestamps are the same as the TimeStamp
+   * retrieved by mozilla::TimeStamp. Since we need this for
+   * vsync timestamps, we enable the creation of mozilla::TimeStamps
+   * on platforms that support vsync aligned refresh drivers / compositors
+   * Verified true as of Jan 31, 2015: B2G and OS X
+   * False on Windows 7
+   * Android's event time uses CLOCK_MONOTONIC via SystemClock.uptimeMilles.
+   * So it is same value of TimeStamp posix implementation.
+   * Wayland/GTK event time also uses CLOCK_MONOTONIC on Weston/Mutter
+   * compositors.
+   * UNTESTED ON OTHER PLATFORMS
+   */
+#if defined(XP_DARWIN) || defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_GTK)
+  static TimeStamp FromSystemTime(int64_t aSystemTime) {
+    static_assert(sizeof(aSystemTime) == sizeof(TimeStampValue),
+                  "System timestamp should be same units as TimeStampValue");
+    return TimeStamp(aSystemTime);
+  }
+#endif
+
+  /**
+   * Return true if this is the "null" moment
+   */
+  bool IsNull() const { return mValue == 0; }
+
+  /**
+   * Return true if this is not the "null" moment, may be used in tests, e.g.:
+   * |if (timestamp) { ... }|
+   */
+  explicit operator bool() const { return mValue != 0; }
+
+  /**
+   * Return a timestamp reflecting the current elapsed system time. This
+   * is monotonically increasing (i.e., does not decrease) over the
+   * lifetime of this process' XPCOM session.
+   *
+   * Now() is trying to ensure the best possible precision on each platform,
+   * at least one millisecond.
+   *
+   * NowLoRes() has been introduced to workaround performance problems of
+   * QueryPerformanceCounter on the Windows platform.  NowLoRes() is giving
+   * lower precision, usually 15.6 ms, but with very good performance benefit.
+   * Use it for measurements of longer times, like >200ms timeouts.
+   */
+  static TimeStamp Now() { return Now(true); }
+  static TimeStamp NowLoRes() { return Now(false); }
+
+  /**
+   * Return a timestamp representing the time when the current process was
+   * created which will be comparable with other timestamps taken with this
+   * class.
+   *
+   * @returns A timestamp representing the time when the process was created
+   */
+  static MFBT_API TimeStamp ProcessCreation();
+
+  /**
+   * Return the very first timestamp that was taken. This can be used instead
+   * of TimeStamp::ProcessCreation() by code that might not allow running the
+   * complex logic required to compute the real process creation. This will
+   * necessarily have been recorded sometimes after TimeStamp::ProcessCreation()
+   * or at best should be equal to it.
+   *
+   * @returns The first tiemstamp that was taken by this process
+   */
+  static MFBT_API TimeStamp FirstTimeStamp();
+
+  /**
+   * Records a process restart. After this call ProcessCreation() will return
+   * the time when the browser was restarted instead of the actual time when
+   * the process was created.
+   */
+  static MFBT_API void RecordProcessRestart();
+
+  /**
+   * Compute the difference between two timestamps. Both must be non-null.
+   */
+  TimeDuration operator-(const TimeStamp& aOther) const {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
+    static_assert(-INT64_MAX > INT64_MIN, "int64_t sanity check");
+    int64_t ticks = int64_t(mValue - aOther.mValue);
+    // Check for overflow.
+    if (mValue > aOther.mValue) {
+      if (ticks < 0) {
+        ticks = INT64_MAX;
+      }
+    } else {
+      if (ticks > 0) {
+        ticks = INT64_MIN;
+      }
+    }
+    return TimeDuration::FromTicks(ticks);
+  }
+
+  TimeStamp operator+(const TimeDuration& aOther) const {
+    TimeStamp result = *this;
+    result += aOther;
+    return result;
+  }
+  TimeStamp operator-(const TimeDuration& aOther) const {
+    TimeStamp result = *this;
+    result -= aOther;
+    return result;
+  }
+  TimeStamp& operator+=(const TimeDuration& aOther) {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    TimeStampValue value = mValue + aOther.mValue;
+    // Check for underflow.
+    // (We don't check for overflow because it's not obvious what the error
+    //  behavior should be in that case.)
+    if (aOther.mValue < 0 && value > mValue) {
+      value = 0;
+    }
+    mValue = value;
+    return *this;
+  }
+  TimeStamp& operator-=(const TimeDuration& aOther) {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    TimeStampValue value = mValue - aOther.mValue;
+    // Check for underflow.
+    // (We don't check for overflow because it's not obvious what the error
+    //  behavior should be in that case.)
+    if (aOther.mValue > 0 && value > mValue) {
+      value = 0;
+    }
+    mValue = value;
+    return *this;
+  }
+
+  bool operator<(const TimeStamp& aOther) const {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
+    return mValue < aOther.mValue;
+  }
+  bool operator<=(const TimeStamp& aOther) const {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
+    return mValue <= aOther.mValue;
+  }
+  bool operator>=(const TimeStamp& aOther) const {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
+    return mValue >= aOther.mValue;
+  }
+  bool operator>(const TimeStamp& aOther) const {
+    MOZ_ASSERT(!IsNull(), "Cannot compute with a null value");
+    MOZ_ASSERT(!aOther.IsNull(), "Cannot compute with aOther null value");
+    return mValue > aOther.mValue;
+  }
+  bool operator==(const TimeStamp& aOther) const {
+    return IsNull() ? aOther.IsNull()
+                    : !aOther.IsNull() && mValue == aOther.mValue;
+  }
+  bool operator!=(const TimeStamp& aOther) const { return !(*this == aOther); }
+
+  // Comparing TimeStamps for equality should be discouraged. Adding
+  // two TimeStamps, or scaling TimeStamps, is nonsense and must never
+  // be allowed.
+
+  static MFBT_API void Startup();
+  static MFBT_API void Shutdown();
+
+ private:
+  friend struct IPC::ParamTraits<mozilla::TimeStamp>;
+  friend struct TimeStampInitialization;
+
+  MOZ_IMPLICIT
+  TimeStamp(TimeStampValue aValue) : mValue(aValue) {}
+
+  static MFBT_API TimeStamp Now(bool aHighResolution);
+
+  /**
+   * Computes the uptime of the current process in microseconds. The result
+   * is platform-dependent and needs to be checked against existing timestamps
+   * for consistency.
+   *
+   * @returns The number of microseconds since the calling process was started
+   *          or 0 if an error was encountered while computing the uptime
+   */
+  static MFBT_API uint64_t ComputeProcessUptime();
+
+  /**
+   * When built with PRIntervalTime, a value of 0 means this instance
+   * is "null". Otherwise, the low 32 bits represent a PRIntervalTime,
+   * and the high 32 bits represent a counter of the number of
+   * rollovers of PRIntervalTime that we've seen. This counter starts
+   * at 1 to avoid a real time colliding with the "null" value.
+   *
+   * PR_INTERVAL_MAX is set at 100,000 ticks per second. So the minimum
+   * time to wrap around is about 2^64/100000 seconds, i.e. about
+   * 5,849,424 years.
+   *
+   * When using a system clock, a value is system dependent.
+   */
+  TimeStampValue mValue;
+};
+
+}  // namespace mozilla
+
+#endif /* mozilla_TimeStamp_h */