text: // Copyright 2013 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "src/base/platform/time.h"
  
  #if V8_OS_POSIX
  #include <fcntl.h>  // for O_RDONLY
  #include <sys/time.h>
  #include <unistd.h>
  #endif
  #if V8_OS_MACOSX
  #include <mach/mach_time.h>
  #endif
  
  #include <string.h>
  
  #if V8_OS_WIN
  #include "src/base/lazy-instance.h"
  #include "src/base/win32-headers.h"
  #endif
  #include "src/base/cpu.h"
  #include "src/base/logging.h"
  #include "src/base/platform/platform.h"
  
  namespace v8 {
  namespace base {
  
  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_MACOSX
  
  TimeDelta TimeDelta::FromMachTimespec(struct mach_timespec ts) {
    DCHECK_GE(ts.tv_nsec, 0);
    DCHECK_LT(ts.tv_nsec,
              static_cast<long>(Time::kNanosecondsPerSecond));  // NOLINT
    return TimeDelta(ts.tv_sec * Time::kMicrosecondsPerSecond +
                     ts.tv_nsec / Time::kNanosecondsPerMicrosecond);
  }
  
  
  struct mach_timespec TimeDelta::ToMachTimespec() const {
    struct mach_timespec ts;
    DCHECK(delta_ >= 0);
    ts.tv_sec = delta_ / Time::kMicrosecondsPerSecond;
    ts.tv_nsec = (delta_ % Time::kMicrosecondsPerSecond) *
        Time::kNanosecondsPerMicrosecond;
    return ts;
  }
  
  #endif  // V8_OS_MACOSX
  
  
  #if V8_OS_POSIX
  
  TimeDelta TimeDelta::FromTimespec(struct timespec ts) {
    DCHECK_GE(ts.tv_nsec, 0);
    DCHECK_LT(ts.tv_nsec,
              static_cast<long>(Time::kNanosecondsPerSecond));  // NOLINT
    return TimeDelta(ts.tv_sec * Time::kMicrosecondsPerSecond +
                     ts.tv_nsec / Time::kNanosecondsPerMicrosecond);
  }
  
  
  struct timespec TimeDelta::ToTimespec() const {
    struct timespec ts;
    ts.tv_sec = delta_ / Time::kMicrosecondsPerSecond;
    ts.tv_nsec = (delta_ % Time::kMicrosecondsPerSecond) *
        Time::kNanosecondsPerMicrosecond;
    return ts;
  }
  
  #endif  // V8_OS_POSIX
  
  
  #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 FINAL {
   public:
    Clock() : initial_ticks_(GetSystemTicks()), initial_time_(GetSystemTime()) {}
  
    Time Now() {
      // Time between resampling the un-granular clock for this API (1 minute).
      const TimeDelta kMaxElapsedTime = TimeDelta::FromMinutes(1);
  
      LockGuard<Mutex> lock_guard(&mutex_);
  
      // Determine current time and ticks.
      TimeTicks ticks = GetSystemTicks();
      Time time = GetSystemTime();
  
      // Check if we need to synchronize with the system clock due to a backwards
      // time change or the amount of time elapsed.
      TimeDelta elapsed = ticks - initial_ticks_;
      if (time < initial_time_ || elapsed > kMaxElapsedTime) {
        initial_ticks_ = ticks;
        initial_time_ = time;
        return time;
      }
  
      return initial_time_ + elapsed;
    }
  
    Time NowFromSystemTime() {
      LockGuard<Mutex> lock_guard(&mutex_);
      initial_ticks_ = GetSystemTicks();
      initial_time_ = GetSystemTime();
      return initial_time_;
    }
  
   private:
    static TimeTicks GetSystemTicks() {
      return TimeTicks::Now();
    }
  
    static Time GetSystemTime() {
      FILETIME ft;
      ::GetSystemTimeAsFileTime(&ft);
      return Time::FromFiletime(ft);
    }
  
    TimeTicks initial_ticks_;
    Time initial_time_;
    Mutex mutex_;
  };
  
  
  static LazyStaticInstance<Clock, DefaultConstructTrait<Clock>,
                            ThreadSafeInitOnceTrait>::type clock =
      LAZY_STATIC_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 {
    DCHECK(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);
    DCHECK_EQ(0, result);
    USE(result);
    return FromTimeval(tv);
  }
  
  
  Time Time::NowFromSystemTime() {
    return Now();
  }
  
  
  Time Time::FromTimespec(struct timespec ts) {
    DCHECK(ts.tv_nsec >= 0);
    DCHECK(ts.tv_nsec < static_cast<long>(kNanosecondsPerSecond));  // NOLINT
    if (ts.tv_nsec == 0 && ts.tv_sec == 0) {
      return Time();
    }
    if (ts.tv_nsec == static_cast<long>(kNanosecondsPerSecond - 1) &&  // NOLINT
        ts.tv_sec == std::numeric_limits<time_t>::max()) {
      return Max();
    }
    return Time(ts.tv_sec * kMicrosecondsPerSecond +
                ts.tv_nsec / kNanosecondsPerMicrosecond);
  }
  
  
  struct timespec Time::ToTimespec() const {
    struct timespec ts;
    if (IsNull()) {
      ts.tv_sec = 0;
      ts.tv_nsec = 0;
      return ts;
    }
    if (IsMax()) {
      ts.tv_sec = std::numeric_limits<time_t>::max();
      ts.tv_nsec = static_cast<long>(kNanosecondsPerSecond - 1);  // NOLINT
      return ts;
    }
    ts.tv_sec = us_ / kMicrosecondsPerSecond;
    ts.tv_nsec = (us_ % kMicrosecondsPerSecond) * kNanosecondsPerMicrosecond;
    return ts;
  }
  
  
  Time Time::FromTimeval(struct timeval tv) {
    DCHECK(tv.tv_usec >= 0);
    DCHECK(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
  
  
  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;
    virtual bool IsHighResolution() = 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 FINAL : public TickClock {
   public:
    explicit HighResolutionTickClock(int64_t ticks_per_second)
        : ticks_per_second_(ticks_per_second) {
      DCHECK_LT(0, ticks_per_second);
    }
    virtual ~HighResolutionTickClock() {}
  
    virtual int64_t Now() OVERRIDE {
      LARGE_INTEGER now;
      BOOL result = QueryPerformanceCounter(&now);
      DCHECK(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::HighResolutionNow()
      // will never return 0.
      return ticks + 1;
    }
  
    virtual bool IsHighResolution() OVERRIDE {
      return true;
    }
  
   private:
    int64_t ticks_per_second_;
  };
  
  
  class RolloverProtectedTickClock FINAL : public TickClock {
   public:
    // We initialize rollover_ms_ to 1 to ensure that we will never
    // return 0 from TimeTicks::HighResolutionNow() and TimeTicks::Now() below.
    RolloverProtectedTickClock() : last_seen_now_(0), rollover_ms_(1) {}
    virtual ~RolloverProtectedTickClock() {}
  
    virtual int64_t Now() OVERRIDE {
      LockGuard<Mutex> lock_guard(&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
      // timeGetTime() provides 1ms granularity when combined with
      // timeBeginPeriod(). If the host application for V8 wants fast timers, it
      // can use timeBeginPeriod() to increase the resolution.
      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_) * Time::kMicrosecondsPerMillisecond;
    }
  
    virtual bool IsHighResolution() OVERRIDE {
      return false;
    }
  
   private:
    Mutex mutex_;
    DWORD last_seen_now_;
    int64_t rollover_ms_;
  };
  
  
  static LazyStaticInstance<RolloverProtectedTickClock,
                            DefaultConstructTrait<RolloverProtectedTickClock>,
                            ThreadSafeInitOnceTrait>::type tick_clock =
      LAZY_STATIC_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());
    DCHECK(!ticks.IsNull());
    return ticks;
  }
  
  
  TimeTicks TimeTicks::HighResolutionNow() {
    // Make sure we never return 0 here.
    TimeTicks ticks(high_res_tick_clock.Pointer()->Now());
    DCHECK(!ticks.IsNull());
    return ticks;
  }
  
  
  // static
  bool TimeTicks::IsHighResolutionClockWorking() {
    return high_res_tick_clock.Pointer()->IsHighResolution();
  }
  
  
  // static
  TimeTicks TimeTicks::KernelTimestampNow() { return TimeTicks(0); }
  
  
  // static
  bool TimeTicks::KernelTimestampAvailable() { return false; }
  
  #else  // V8_OS_WIN
  
  TimeTicks TimeTicks::Now() {
    return HighResolutionNow();
  }
  
  
  TimeTicks TimeTicks::HighResolutionNow() {
    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);
      DCHECK_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_LIBRT_NOT_AVAILABLE
    // TODO(bmeurer): This is a temporary hack to support cross-compiling
    // Chrome for Android in AOSP. Remove this once AOSP is fixed, also
    // cleanup the tools/gyp/v8.gyp file.
    struct timeval tv;
    int result = gettimeofday(&tv, NULL);
    DCHECK_EQ(0, result);
    USE(result);
    ticks = (tv.tv_sec * Time::kMicrosecondsPerSecond + tv.tv_usec);
  #elif V8_OS_POSIX
    struct timespec ts;
    int result = clock_gettime(CLOCK_MONOTONIC, &ts);
    DCHECK_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);
  }
  
  
  // static
  bool TimeTicks::IsHighResolutionClockWorking() {
    return true;
  }
  
  
  #if V8_OS_LINUX && !V8_LIBRT_NOT_AVAILABLE
  
  class KernelTimestampClock {
   public:
    KernelTimestampClock() : clock_fd_(-1), clock_id_(kClockInvalid) {
      clock_fd_ = open(kTraceClockDevice, O_RDONLY);
      if (clock_fd_ == -1) {
        return;
      }
      clock_id_ = get_clockid(clock_fd_);
    }
  
    virtual ~KernelTimestampClock() {
      if (clock_fd_ != -1) {
        close(clock_fd_);
      }
    }
  
    int64_t Now() {
      if (clock_id_ == kClockInvalid) {
        return 0;
      }
  
      struct timespec ts;
  
      clock_gettime(clock_id_, &ts);
      return ((int64_t)ts.tv_sec * kNsecPerSec) + ts.tv_nsec;
    }
  
    bool Available() { return clock_id_ != kClockInvalid; }
  
   private:
    static const clockid_t kClockInvalid = -1;
    static const char kTraceClockDevice[];
    static const uint64_t kNsecPerSec = 1000000000;
  
    int clock_fd_;
    clockid_t clock_id_;
  
    static int get_clockid(int fd) { return ((~(clockid_t)(fd) << 3) | 3); }
  };
  
  
  // Timestamp module name
  const char KernelTimestampClock::kTraceClockDevice[] = "/dev/trace_clock";
  
  #else
  
  class KernelTimestampClock {
   public:
    KernelTimestampClock() {}
  
    int64_t Now() { return 0; }
    bool Available() { return false; }
  };
  
  #endif  // V8_OS_LINUX && !V8_LIBRT_NOT_AVAILABLE
  
  static LazyStaticInstance<KernelTimestampClock,
                            DefaultConstructTrait<KernelTimestampClock>,
                            ThreadSafeInitOnceTrait>::type kernel_tick_clock =
      LAZY_STATIC_INSTANCE_INITIALIZER;
  
  
  // static
  TimeTicks TimeTicks::KernelTimestampNow() {
    return TimeTicks(kernel_tick_clock.Pointer()->Now());
  }
  
  
  // static
  bool TimeTicks::KernelTimestampAvailable() {
    return kernel_tick_clock.Pointer()->Available();
  }
  
  #endif  // V8_OS_WIN
  
  } }  // namespace v8::base
  