Add Chromium-style TimeDelta, Time and TimeTicks classes, and a new ElapsedTimer class.

src/time/time.cc

Index: src/time/time.cc
diff --git a/src/time/time.cc b/src/time/time.cc
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index 0000000000000000000000000000000000000000..1742f30b67804022f89051bbf61b9497b3bb71bb
--- /dev/null
+++ b/src/time/time.cc
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+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "time.h"
+
+#if V8_OS_POSIX
+#include <sys/time.h>
+#endif
+#if V8_OS_MACOSX
+#include <mach/mach_time.h>
+#endif
+
+#include <cstring>
+
+#include "checks.h"
+#include "cpu.h"
+#include "platform.h"
+#if V8_OS_WIN
+#define V8_WIN32_HEADERS_FULL
+#include "win32-headers.h"
+#endif
+
+namespace v8 {
+namespace internal {
+
+TimeDelta TimeDelta::FromDays(int days) {
+  return TimeDelta(days * Time::kMicrosecondsPerDay);
+}
+
+
+TimeDelta TimeDelta::FromHours(int hours) {
+  return TimeDelta(hours * Time::kMicrosecondsPerHour);
+}
+
+
+TimeDelta TimeDelta::FromMinutes(int minutes) {
+  return TimeDelta(minutes * Time::kMicrosecondsPerMinute);
+}
+
+
+TimeDelta TimeDelta::FromSeconds(int64_t seconds) {
+  return TimeDelta(seconds * Time::kMicrosecondsPerSecond);
+}
+
+
+TimeDelta TimeDelta::FromMilliseconds(int64_t milliseconds) {
+  return TimeDelta(milliseconds * Time::kMicrosecondsPerMillisecond);
+}
+
+
+TimeDelta TimeDelta::FromNanoseconds(int64_t nanoseconds) {
+  return TimeDelta(nanoseconds / Time::kNanosecondsPerMicrosecond);
+}
+
+
+int TimeDelta::InDays() const {
+  return static_cast<int>(delta_ / Time::kMicrosecondsPerDay);
+}
+
+
+int TimeDelta::InHours() const {
+  return static_cast<int>(delta_ / Time::kMicrosecondsPerHour);
+}
+
+
+int TimeDelta::InMinutes() const {
+  return static_cast<int>(delta_ / Time::kMicrosecondsPerMinute);
+}
+
+
+double TimeDelta::InSecondsF() const {
+  return static_cast<double>(delta_) / Time::kMicrosecondsPerSecond;
+}
+
+
+int64_t TimeDelta::InSeconds() const {
+  return delta_ / Time::kMicrosecondsPerSecond;
+}
+
+
+double TimeDelta::InMillisecondsF() const {
+  return static_cast<double>(delta_) / Time::kMicrosecondsPerMillisecond;
+}
+
+
+int64_t TimeDelta::InMilliseconds() const {
+  return delta_ / Time::kMicrosecondsPerMillisecond;
+}
+
+
+int64_t TimeDelta::InNanoseconds() const {
+  return delta_ * Time::kNanosecondsPerMicrosecond;
+}
+
+
+#if V8_OS_WIN
+
+// We implement time using the high-resolution timers so that we can get
+// timeouts which are smaller than 10-15ms. To avoid any drift, we
+// periodically resync the internal clock to the system clock.
+class Clock V8_FINAL {
+ public:
+  Clock() : initial_time_(CurrentWallclockTime()),
+            initial_ticks_(TimeTicks::Now()),
+            mutex_(OS::CreateMutex()) {}
+
+  ~Clock() { delete mutex_; }
+
+  Time Now() {
+    // This must be executed under lock.
+    ScopedLock sl(mutex_);
+
+    // Calculate the time elapsed since we started our timer.
+    TimeDelta elapsed = TimeTicks::Now() - initial_ticks_;
+
+    // Check if we don't need to synchronize with the wallclock yet.
+    if (elapsed.InMicroseconds() <= kMaxMicrosecondsToAvoidDrift) {
+      return initial_time_ + elapsed;
+    }
+
+    // Resynchronize with the wallclock.
+    initial_ticks_ = TimeTicks::Now();
+    initial_time_ = CurrentWallclockTime();
+    return initial_time_;
+  }
+
+  Time NowFromSystemTime() {
+    ScopedLock sl(mutex_);
+    initial_ticks_ = TimeTicks::Now();
+    initial_time_ = CurrentWallclockTime();
+    return initial_time_;
+  }
+
+ private:
+  // Time between resampling the un-granular clock for this API (1 minute).
+  static const int64_t kMaxMicrosecondsToAvoidDrift =
+      Time::kMicrosecondsPerMinute;
+
+  static Time CurrentWallclockTime() {
+    FILETIME ft;
+    ::GetSystemTimeAsFileTime(&ft);
+    return Time::FromFiletime(ft);
+  }
+
+  TimeTicks initial_ticks_;
+  Time initial_time_;
+  Mutex* mutex_;
+};
+
+
+static LazyDynamicInstance<Clock,
+    DefaultCreateTrait<Clock>,
+    ThreadSafeInitOnceTrait>::type clock = LAZY_DYNAMIC_INSTANCE_INITIALIZER;
+
+
+Time Time::Now() {
+  return clock.Pointer()->Now();
+}
+
+
+Time Time::NowFromSystemTime() {
+  return clock.Pointer()->NowFromSystemTime();
+}
+
+
+// Time between windows epoch and standard epoch.
+static const int64_t kTimeToEpochInMicroseconds = V8_INT64_C(11644473600000000);
+
+
+Time Time::FromFiletime(FILETIME ft) {
+  if (ft.dwLowDateTime == 0 && ft.dwHighDateTime == 0) {
+    return Time();
+  }
+  if (ft.dwLowDateTime == std::numeric_limits<DWORD>::max() &&
+      ft.dwHighDateTime == std::numeric_limits<DWORD>::max()) {
+    return Max();
+  }
+  int64_t us = (static_cast<uint64_t>(ft.dwLowDateTime) +
+                static_cast<uint64_t>(ft.dwHighDateTime) << 32) / 10;
+  return Time(us - kTimeToEpochInMicroseconds);
+}
+
+
+FILETIME Time::ToFiletime() const {
+  ASSERT(us_ >= 0);
+  FILETIME ft;
+  if (IsNull()) {
+    ft.dwLowDateTime = 0;
+    ft.dwHighDateTime = 0;
+    return ft;
+  }
+  if (IsMax()) {
+    ft.dwLowDateTime = std::numeric_limits<DWORD>::max();
+    ft.dwHighDateTime = std::numeric_limits<DWORD>::max();
+    return ft;
+  }
+  uint64_t us = static_cast<uint64_t>(us_ + kTimeToEpochInMicroseconds) * 10;
+  ft.dwLowDateTime = static_cast<DWORD>(us);
+  ft.dwHighDateTime = static_cast<DWORD>(us >> 32);
+  return ft;
+}
+
+#elif V8_OS_POSIX
+
+Time Time::Now() {
+  struct timeval tv;
+  int result = gettimeofday(&tv, NULL);
+  ASSERT_EQ(0, result);
+  USE(result);
+  return FromTimeval(tv);
+}
+
+
+Time Time::NowFromSystemTime() {
+  return Now();
+}
+
+
+Time Time::FromTimeval(struct timeval tv) {
+  ASSERT(tv.tv_usec >= 0);
+  ASSERT(tv.tv_usec < static_cast<suseconds_t>(kMicrosecondsPerSecond));
+  if (tv.tv_usec == 0 && tv.tv_sec == 0) {
+    return Time();
+  }
+  if (tv.tv_usec == static_cast<suseconds_t>(kMicrosecondsPerSecond - 1) &&
+      tv.tv_sec == std::numeric_limits<time_t>::max()) {
+    return Max();
+  }
+  return Time(tv.tv_sec * kMicrosecondsPerSecond + tv.tv_usec);
+}
+
+
+struct timeval Time::ToTimeval() const {
+  struct timeval tv;
+  if (IsNull()) {
+    tv.tv_sec = 0;
+    tv.tv_usec = 0;
+    return tv;
+  }
+  if (IsMax()) {
+    tv.tv_sec = std::numeric_limits<time_t>::max();
+    tv.tv_usec = static_cast<suseconds_t>(kMicrosecondsPerSecond - 1);
+    return tv;
+  }
+  tv.tv_sec = us_ / kMicrosecondsPerSecond;
+  tv.tv_usec = us_ % kMicrosecondsPerSecond;
+  return tv;
+}
+
+#endif  // V8_OS_WIN

[Michael Achenbach, 2013/08/28 10:47:17]

Is this comment not confusing, since it is the V8_OS_POSIX block that just
ended?

[Benedikt Meurer, 2013/08/28 10:58:36]

That's how we do it all over the place, unfortunately.

+
+
+Time Time::FromJsTime(double ms_since_epoch) {
+  // The epoch is a valid time, so this constructor doesn't interpret
+  // 0 as the null time.
+  if (ms_since_epoch == std::numeric_limits<double>::max()) {
+    return Max();
+  }
+  return Time(
+      static_cast<int64_t>(ms_since_epoch * kMicrosecondsPerMillisecond));
+}
+
+
+double Time::ToJsTime() const {
+  if (IsNull()) {
+    // Preserve 0 so the invalid result doesn't depend on the platform.
+    return 0;
+  }
+  if (IsMax()) {
+    // Preserve max without offset to prevent overflow.
+    return std::numeric_limits<double>::max();
+  }
+  return static_cast<double>(us_) / kMicrosecondsPerMillisecond;
+}
+
+
+#if V8_OS_WIN
+
+class TickClock {
+ public:
+  virtual ~TickClock() {}
+  virtual int64_t Now() = 0;
+};
+
+
+// Overview of time counters:
+// (1) CPU cycle counter. (Retrieved via RDTSC)
+// The CPU counter provides the highest resolution time stamp and is the least
+// expensive to retrieve. However, the CPU counter is unreliable and should not
+// be used in production. Its biggest issue is that it is per processor and it
+// is not synchronized between processors. Also, on some computers, the counters
+// will change frequency due to thermal and power changes, and stop in some
+// states.
+//
+// (2) QueryPerformanceCounter (QPC). The QPC counter provides a high-
+// resolution (100 nanoseconds) time stamp but is comparatively more expensive
+// to retrieve. What QueryPerformanceCounter actually does is up to the HAL.
+// (with some help from ACPI).
+// According to http://blogs.msdn.com/oldnewthing/archive/2005/09/02/459952.aspx
+// in the worst case, it gets the counter from the rollover interrupt on the
+// programmable interrupt timer. In best cases, the HAL may conclude that the
+// RDTSC counter runs at a constant frequency, then it uses that instead. On
+// multiprocessor machines, it will try to verify the values returned from
+// RDTSC on each processor are consistent with each other, and apply a handful
+// of workarounds for known buggy hardware. In other words, QPC is supposed to
+// give consistent result on a multiprocessor computer, but it is unreliable in
+// reality due to bugs in BIOS or HAL on some, especially old computers.
+// With recent updates on HAL and newer BIOS, QPC is getting more reliable but
+// it should be used with caution.
+//
+// (3) System time. The system time provides a low-resolution (typically 10ms
+// to 55 milliseconds) time stamp but is comparatively less expensive to
+// retrieve and more reliable.
+class HighResolutionTickClock V8_FINAL : public TickClock {
+ public:
+  explicit HighResolutionTickClock(int64_t ticks_per_second)
+      : ticks_per_second_(ticks_per_second) {
+    ASSERT_NE(0, ticks_per_second);
+  }
+  virtual ~HighResolutionTickClock() {}
+
+  virtual int64_t Now() V8_OVERRIDE {
+    LARGE_INTEGER now;
+    BOOL result = QueryPerformanceCounter(&now);
+    ASSERT(result);
+    USE(result);
+
+    // Intentionally calculate microseconds in a round about manner to avoid
+    // overflow and precision issues. Think twice before simplifying!
+    int64_t whole_seconds = now.QuadPart / ticks_per_second_;
+    int64_t leftover_ticks = now.QuadPart % ticks_per_second_;
+    int64_t ticks = (whole_seconds * Time::kMicrosecondsPerSecond) +
+        ((leftover_ticks * Time::kMicrosecondsPerSecond) / ticks_per_second_);
+
+    // Make sure we never return 0 here, so that TimeTicks::HighResNow()
+    // will never return 0.
+    return ticks + 1;
+  }
+
+ private:
+  int64_t ticks_per_second_;
+};
+
+
+class RolloverProtectedTickClock V8_FINAL : public TickClock {
+ public:
+  RolloverProtectedTickClock()
+      : mutex_(OS::CreateMutex()), last_seen_now_(0), rollover_ms_(1) {
+    // We initialize rollover_ms_ to 1 to ensure that we will never
+    // return 0 from TimeTicks::HighResNow() and TimeTicks::Now() below.
+  }
+  virtual ~RolloverProtectedTickClock() { delete mutex_; }
+
+  virtual int64_t Now() V8_OVERRIDE {
+    ScopedLock sl(mutex_);
+    // We use timeGetTime() to implement TimeTicks::Now(), which rolls over
+    // every ~49.7 days. We try to track rollover ourselves, which works if
+    // TimeTicks::Now() is called at least every 49 days.
+    // Note that we do not use GetTickCount() here, since timeGetTime() gives
+    // more predictable delta values, as described here:
+    // http://blogs.msdn.com/b/larryosterman/archive/2009/09/02/what-s-the-difference-between-gettickcount-and-timegettime.aspx
+    DWORD now = timeGetTime();
+    if (now < last_seen_now_) {
+      rollover_ms_ += V8_INT64_C(0x100000000);  // ~49.7 days.
+    }
+    last_seen_now_ = now;
+    return now + rollover_ms_;
+  }
+
+ private:
+  Mutex* mutex_;
+  DWORD last_seen_now_;
+  int64_t rollover_ms_;
+};
+
+
+static LazyDynamicInstance<RolloverProtectedTickClock,
+    DefaultCreateTrait<RolloverProtectedTickClock>,
+    ThreadSafeInitOnceTrait>::type tick_clock =
+        LAZY_DYNAMIC_INSTANCE_INITIALIZER;
+
+
+struct CreateHighResTickClockTrait {
+  static TickClock* Create() {
+    // Check if the installed hardware supports a high-resolution performance
+    // counter, and if not fallback to the low-resolution tick clock.
+    LARGE_INTEGER ticks_per_second;
+    if (!QueryPerformanceFrequency(&ticks_per_second)) {
+      return tick_clock.Pointer();
+    }
+
+    // On Athlon X2 CPUs (e.g. model 15) the QueryPerformanceCounter
+    // is unreliable, fallback to the low-resolution tick clock.
+    CPU cpu;
+    if (strcmp(cpu.vendor(), "AuthenticAMD") == 0 && cpu.family() == 15) {
+      return tick_clock.Pointer();
+    }
+
+    return new HighResolutionTickClock(ticks_per_second.QuadPart);
+  }
+};
+
+
+static LazyDynamicInstance<TickClock,
+    CreateHighResTickClockTrait,
+    ThreadSafeInitOnceTrait>::type high_res_tick_clock =
+        LAZY_DYNAMIC_INSTANCE_INITIALIZER;
+
+
+TimeTicks TimeTicks::Now() {
+  // Make sure we never return 0 here.
+  TimeTicks ticks(tick_clock.Pointer()->Now());
+  ASSERT(!ticks.IsNull());
+  return ticks;
+}
+
+
+TimeTicks TimeTicks::HighResNow() {
+  // Make sure we never return 0 here.
+  TimeTicks ticks(high_res_tick_clock.Pointer()->Now());
+  ASSERT(!ticks.IsNull());
+  return ticks;
+}
+
+#else  // V8_OS_WIN
+
+TimeTicks TimeTicks::Now() {
+  return HighResNow();
+}
+
+
+TimeTicks TimeTicks::HighResNow() {
+  int64_t ticks;
+#if V8_OS_MACOSX
+  static struct mach_timebase_info info;
+  if (info.denom == 0) {
+    kern_return_t result = mach_timebase_info(&info);
+    ASSERT_EQ(KERN_SUCCESS, result);
+    USE(result);
+  }
+  ticks = (mach_absolute_time() / Time::kNanosecondsPerMicrosecond *
+           info.numer / info.denom);
+#elif V8_OS_SOLARIS
+  ticks = (gethrtime() / Time::kNanosecondsPerMicrosecond);
+#elif V8_OS_POSIX
+  struct timespec ts;
+  int result = clock_gettime(CLOCK_MONOTONIC, &ts);
+  ASSERT_EQ(0, result);
+  USE(result);
+  ticks = (ts.tv_sec * Time::kMicrosecondsPerSecond +
+           ts.tv_nsec / Time::kNanosecondsPerMicrosecond);
+#endif  // V8_OS_MACOSX
+  // Make sure we never return 0 here.
+  return TimeTicks(ticks + 1);
+}
+
+#endif  // V8_OS_WIN
+
+} }  // namespace v8::internal