Reviewers: Jakob, danno,
Description:
Revert OS::TimeCurrentMillis on Windows introduced in r16413.
BUG=
Please review this at https://codereview.chromium.org/24529002/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+77, -9 lines):
M src/platform-win32.cc
A + test/mjsunit/timer.js
Index: src/platform-win32.cc
diff --git a/src/platform-win32.cc b/src/platform-win32.cc
index
7b26dfb7bf5ebfd04accf78a85972bf64d3ac2b7..41a4f1450c9351d1a92d1b23f4e9c3e4a93be9de
100644
--- a/src/platform-win32.cc
+++ b/src/platform-win32.cc
@@ -240,12 +240,16 @@ void MathSetup() {
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
@@ -314,6 +318,12 @@ 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.
Win32Time::Win32Time(double jstime) {
t() = static_cast<int64_t>(jstime) * kTimeScaler + kTimeEpoc;
@@ -340,6 +350,62 @@ double Win32Time::ToJSTime() {
}
+// 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.
// The guess is very biased towards the northern hemisphere.
const char* Win32Time::GuessTimezoneNameFromBias(int bias) {
@@ -529,7 +595,9 @@ 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();
+ Win32Time t;
+ t.SetToCurrentTime();
+ return t.ToJSTime();
}
Index: test/mjsunit/timer.js
diff --git a/test/mjsunit/array-push-non-smi-value.js
b/test/mjsunit/timer.js
similarity index 88%
copy from test/mjsunit/array-push-non-smi-value.js
copy to test/mjsunit/timer.js
index
460dd2a911e88a592c221f9d3426ff69b14e0e9d..5ed234ad5328d5782f9c6bb5b7b2f04551471e6c
100644
--- a/test/mjsunit/array-push-non-smi-value.js
+++ b/test/mjsunit/timer.js
@@ -25,12 +25,12 @@
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-// Check pushes of non-SMI values.
-var a = [];
-function func() {
- return a.push(0x40000000) > 60;
-}
+// Tests timer milliseconds granularity.
-assertFalse(func());
-assertFalse(func());
-assertFalse(func());
+var start = new Date();
+for (var i = 0; i < 10000; i++) {
+ var end = new Date();
+ assertTrue(start <= end);
+ assertTrue(end - start <= 1);
+ start = end;
+}
--
--
v8-dev mailing list
[email protected]
http://groups.google.com/group/v8-dev
---
You received this message because you are subscribed to the Google Groups "v8-dev" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.
