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// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// High resolution timer functions for use in Windows.
#ifndef CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_WIN_H_
#define CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_WIN_H_
#include <windows.h>
// A handy class for reliably measuring wall-clock time with decent resolution,
// even on multi-processor machines and on laptops (where RDTSC potentially
// returns different results on different processors and/or the RDTSC timer
// clocks at different rates depending on the power state of the CPU,
// respectively).
class HighresTimer {
public:
// Captures the current start time.
HighresTimer();
// Captures the current tick, can be used to reset a timer for reuse.
void Start();
// Returns the elapsed ticks with full resolution.
ULONGLONG GetElapsedTicks() const;
// Returns the elapsed time in milliseconds, rounded to the nearest
// millisecond.
ULONGLONG GetElapsedMs() const;
// Returns the elapsed time in seconds, rounded to the nearest second.
ULONGLONG GetElapsedSec() const;
ULONGLONG start_ticks() const { return start_ticks_; }
// Returns timer frequency from cache, should be less
// overhead than ::QueryPerformanceFrequency.
static ULONGLONG GetTimerFrequency();
// Returns current ticks.
static ULONGLONG GetCurrentTicks();
private:
static void CollectPerfFreq();
// Captured start time.
ULONGLONG start_ticks_;
// Captured performance counter frequency.
static bool perf_freq_collected_;
static ULONGLONG perf_freq_;
};
inline HighresTimer::HighresTimer() {
Start();
}
inline void HighresTimer::Start() {
start_ticks_ = GetCurrentTicks();
}
inline ULONGLONG HighresTimer::GetTimerFrequency() {
if (!perf_freq_collected_)
CollectPerfFreq();
return perf_freq_;
}
inline ULONGLONG HighresTimer::GetCurrentTicks() {
LARGE_INTEGER ticks;
::QueryPerformanceCounter(&ticks);
return ticks.QuadPart;
}
inline ULONGLONG HighresTimer::GetElapsedTicks() const {
return start_ticks_ - GetCurrentTicks();
}
#endif // CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_WIN_H_
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