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

src/platform-win32.cc

Index: src/platform-win32.cc
diff --git a/src/platform-win32.cc b/src/platform-win32.cc
index f822049883b4e85674161e0f0605e94df344b297..f52bb43d9c0ca8696c49cf4b8efe886fdba618b5 100644
--- a/src/platform-win32.cc
+++ b/src/platform-win32.cc
@@ -246,15 +246,19 @@ void MathSetup() {
 // timestamps are represented as a doubles in milliseconds since 00:00:00 UTC,
 // January 1, 1970.
 
-class Win32Time {
+class Time {
  public:
   // Constructors.
-  explicit Win32Time(double jstime);
-  Win32Time(int year, int mon, int day, int hour, int min, int sec);
+  Time();
+  explicit Time(double jstime);
+  Time(int year, int mon, int day, int hour, int min, int sec);
 
   // Convert timestamp to JavaScript representation.
   double ToJSTime();
 
+  // Set timestamp to current time.
+  void SetToCurrentTime();
+
   // Returns the local timezone offset in milliseconds east of UTC. This is
   // the number of milliseconds you must add to UTC to get local time, i.e.
   // LocalOffset(CET) = 3600000 and LocalOffset(PST) = -28800000. This
@@ -296,6 +300,10 @@ class Win32Time {
   // Return whether or not daylight savings time is in effect at this time.
   bool InDST();
 
+  // Return the difference (in milliseconds) between this timestamp and
+  // another timestamp.
+  int64_t Diff(Time* other);
+
   // Accessor for FILETIME representation.
   FILETIME& ft() { return time_.ft_; }
 
@@ -317,20 +325,26 @@ class Win32Time {
 
 
 // Static variables.
-bool Win32Time::tz_initialized_ = false;
-TIME_ZONE_INFORMATION Win32Time::tzinfo_;
-char Win32Time::std_tz_name_[kTzNameSize];
-char Win32Time::dst_tz_name_[kTzNameSize];
+bool Time::tz_initialized_ = false;
+TIME_ZONE_INFORMATION Time::tzinfo_;
+char Time::std_tz_name_[kTzNameSize];
+char Time::dst_tz_name_[kTzNameSize];
+
+
+// Initialize timestamp to start of epoc.
+Time::Time() {
+  t() = 0;
+}
 
 
 // Initialize timestamp from a JavaScript timestamp.
-Win32Time::Win32Time(double jstime) {
+Time::Time(double jstime) {
   t() = static_cast<int64_t>(jstime) * kTimeScaler + kTimeEpoc;
 }
 
 
 // Initialize timestamp from date/time components.
-Win32Time::Win32Time(int year, int mon, int day, int hour, int min, int sec) {
+Time::Time(int year, int mon, int day, int hour, int min, int sec) {
   SYSTEMTIME st;
   st.wYear = year;
   st.wMonth = mon;
@@ -344,14 +358,14 @@ Win32Time::Win32Time(int year, int mon, int day, int hour, int min, int sec) {
 
 
 // Convert timestamp to JavaScript timestamp.
-double Win32Time::ToJSTime() {
+double Time::ToJSTime() {
   return static_cast<double>((t() - kTimeEpoc) / kTimeScaler);
 }
 
 
 // Guess the name of the timezone from the bias.
 // The guess is very biased towards the northern hemisphere.
-const char* Win32Time::GuessTimezoneNameFromBias(int bias) {
+const char* Time::GuessTimezoneNameFromBias(int bias) {
   static const int kHour = 60;
   switch (-bias) {
     case -9*kHour: return "Alaska";
@@ -376,7 +390,7 @@ const char* Win32Time::GuessTimezoneNameFromBias(int bias) {
 // Initialize timezone information. The timezone information is obtained from
 // windows. If we cannot get the timezone information we fall back to CET.
 // Please notice that this code is not thread-safe.
-void Win32Time::TzSet() {
+void Time::TzSet() {
   // Just return if timezone information has already been initialized.
   if (tz_initialized_) return;
 
@@ -425,16 +439,78 @@ void Win32Time::TzSet() {
 }
 
 
+// Return the difference in milliseconds between this and another timestamp.
+int64_t Time::Diff(Time* other) {
+  return (t() - other->t()) / kTimeScaler;
+}
+
+
+// Set timestamp to current time.
+void Time::SetToCurrentTime() {
+  // The default GetSystemTimeAsFileTime has a ~15.5ms resolution.
+  // Because we're fast, we like fast timers which have at least a
+  // 1ms resolution.
+  //
+  // 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.
+  //
+  // Using timeGetTime() has a drawback because it is a 32bit value
+  // and hence rolls-over every ~49days.
+  //
+  // To use the clock, we use GetSystemTimeAsFileTime as our base;
+  // and then use timeGetTime to extrapolate current time from the
+  // start time.  To deal with rollovers, we resync the clock
+  // any time when more than kMaxClockElapsedTime has passed or
+  // whenever timeGetTime creates a rollover.
+
+  static bool initialized = false;
+  static TimeStamp init_time;
+  static DWORD init_ticks;
+  static const int64_t kHundredNanosecondsPerSecond = 10000000;
+  static const int64_t kMaxClockElapsedTime =
+      60*kHundredNanosecondsPerSecond;  // 1 minute
+
+  // If we are uninitialized, we need to resync the clock.
+  bool needs_resync = !initialized;
+
+  // Get the current time.
+  TimeStamp time_now;
+  GetSystemTimeAsFileTime(&time_now.ft_);
+  DWORD ticks_now = timeGetTime();
+
+  // Check if we need to resync due to clock rollover.
+  needs_resync |= ticks_now < init_ticks;
+
+  // Check if we need to resync due to elapsed time.
+  needs_resync |= (time_now.t_ - init_time.t_) > kMaxClockElapsedTime;
+
+  // Check if we need to resync due to backwards time change.
+  needs_resync |= time_now.t_ < init_time.t_;
+
+  // Resync the clock if necessary.
+  if (needs_resync) {
+    GetSystemTimeAsFileTime(&init_time.ft_);
+    init_ticks = ticks_now = timeGetTime();
+    initialized = true;
+  }
+
+  // Finally, compute the actual time.  Why is this so hard.
+  DWORD elapsed = ticks_now - init_ticks;
+  this->time_.t_ = init_time.t_ + (static_cast<int64_t>(elapsed) * 10000);
+}
+
+
 // Return the local timezone offset in milliseconds east of UTC. This
 // takes into account whether daylight saving is in effect at the time.
 // Only times in the 32-bit Unix range may be passed to this function.
 // Also, adding the time-zone offset to the input must not overflow.
 // The function EquivalentTime() in date.js guarantees this.
-int64_t Win32Time::LocalOffset() {
+int64_t Time::LocalOffset() {
   // Initialize timezone information, if needed.
   TzSet();
 
-  Win32Time rounded_to_second(*this);
+  Time rounded_to_second(*this);
   rounded_to_second.t() = rounded_to_second.t() / 1000 / kTimeScaler *
       1000 * kTimeScaler;
   // Convert to local time using POSIX localtime function.
@@ -465,7 +541,7 @@ int64_t Win32Time::LocalOffset() {
 
 
 // Return whether or not daylight savings time is in effect at this time.
-bool Win32Time::InDST() {
+bool Time::InDST() {
   // Initialize timezone information, if needed.
   TzSet();
 
@@ -489,14 +565,14 @@ bool Win32Time::InDST() {
 
 
 // Return the daylight savings time offset for this time.
-int64_t Win32Time::DaylightSavingsOffset() {
+int64_t Time::DaylightSavingsOffset() {
   return InDST() ? 60 * kMsPerMinute : 0;
 }
 
 
 // Returns a string identifying the current timezone for the
 // timestamp taking into account daylight saving.
-char* Win32Time::LocalTimezone() {
+char* Time::LocalTimezone() {
   // Return the standard or DST time zone name based on whether daylight
   // saving is in effect at the given time.
   return InDST() ? dst_tz_name_ : std_tz_name_;
@@ -538,14 +614,22 @@ int OS::GetUserTime(uint32_t* secs,  uint32_t* usecs) {
 // Returns current time as the number of milliseconds since
 // 00:00:00 UTC, January 1, 1970.
 double OS::TimeCurrentMillis() {
-  return Time::Now().ToJsTime();
+  Time t;
+  t.SetToCurrentTime();
+  return t.ToJSTime();
+}
+
+
+// Returns the tickcounter based on timeGetTime.
+int64_t OS::Ticks() {
+  return timeGetTime() * 1000;  // Convert to microseconds.
 }
 
 
 // Returns a string identifying the current timezone taking into
 // account daylight saving.
 const char* OS::LocalTimezone(double time) {
-  return Win32Time(time).LocalTimezone();
+  return Time(time).LocalTimezone();
 }
 
 
@@ -553,7 +637,7 @@ const char* OS::LocalTimezone(double time) {
 // taking daylight savings time into account.
 double OS::LocalTimeOffset() {
   // Use current time, rounded to the millisecond.
-  Win32Time t(TimeCurrentMillis());
+  Time t(TimeCurrentMillis());
   // Time::LocalOffset inlcudes any daylight savings offset, so subtract it.
   return static_cast<double>(t.LocalOffset() - t.DaylightSavingsOffset());
 }
@@ -562,7 +646,7 @@ double OS::LocalTimeOffset() {
 // Returns the daylight savings offset in milliseconds for the given
 // time.
 double OS::DaylightSavingsOffset(double time) {
-  int64_t offset = Win32Time(time).DaylightSavingsOffset();
+  int64_t offset = Time(time).DaylightSavingsOffset();
   return static_cast<double>(offset);
 }