Revision: 16938
Author: [email protected]
Date: Wed Sep 25 09:50:48 2013 UTC
Log: Revert OS::TimeCurrentMillis on Windows introduced in r16413.
BUG=chromium:288924
[email protected], [email protected]
Review URL: https://codereview.chromium.org/24529002
http://code.google.com/p/v8/source/detail?r=16938
Added:
/branches/bleeding_edge/test/mjsunit/timer.js
Modified:
/branches/bleeding_edge/src/platform-win32.cc
=======================================
--- /dev/null
+++ /branches/bleeding_edge/test/mjsunit/timer.js Wed Sep 25 09:50:48 2013
UTC
@@ -0,0 +1,35 @@
+// 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.
+
+// Tests timer milliseconds granularity.
+
+var start = Date.now();
+var end = Date.now();
+while (end - start == 0) {
+ end = Date.now();
+}
+assertTrue(end - start <= 2);
=======================================
--- /branches/bleeding_edge/src/platform-win32.cc Mon Sep 23 14:11:59 2013
UTC
+++ /branches/bleeding_edge/src/platform-win32.cc Wed Sep 25 09:50:48 2013
UTC
@@ -240,12 +240,16 @@
class Win32Time {
public:
// Constructors.
+ Win32Time();
explicit Win32Time(double jstime);
Win32Time(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
@@ -312,6 +316,12 @@
TIME_ZONE_INFORMATION Win32Time::tzinfo_;
char Win32Time::std_tz_name_[kTzNameSize];
char Win32Time::dst_tz_name_[kTzNameSize];
+
+
+// Initialize timestamp to start of epoc.
+Win32Time::Win32Time() {
+ t() = 0;
+}
// Initialize timestamp from a JavaScript timestamp.
@@ -338,6 +348,62 @@
double Win32Time::ToJSTime() {
return static_cast<double>((t() - kTimeEpoc) / kTimeScaler);
}
+
+
+// Set timestamp to current time.
+void Win32Time::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);
+}
// Guess the name of the timezone from the bias.
@@ -529,7 +595,9 @@
// Returns current time as the number of milliseconds since
// 00:00:00 UTC, January 1, 1970.
double OS::TimeCurrentMillis() {
- return Time::Now().ToJsTime();
+ Win32Time t;
+ t.SetToCurrentTime();
+ return t.ToJSTime();
}
--
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