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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 on Mac OS.
#ifndef CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_MAC_H_
#define CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_MAC_H_
#include <mach/mach.h>
#include <mach/mach_time.h>
#include "base/basictypes.h"
// A handy class for reliably measuring wall-clock time with decent resolution.
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.
uint64 GetElapsedTicks() const;
// Returns the elapsed time in milliseconds, rounded to the nearest
// millisecond.
uint64 GetElapsedMs() const;
// Returns the elapsed time in seconds, rounded to the nearest second.
uint64 GetElapsedSec() const;
uint64 start_ticks() const { return start_ticks_; }
// Returns timer frequency from cache, should be less overhead than
// ::QueryPerformanceFrequency.
static uint64 GetTimerFrequency();
// Returns current ticks.
static uint64 GetCurrentTicks();
private:
static void CollectPerfRatio();
// Captured start time.
uint64 start_ticks_;
// Captured performance counter frequency.
static bool perf_ratio_collected_;
static mach_timebase_info_data_t perf_ratio_;
};
inline HighresTimer::HighresTimer() {
Start();
}
inline void HighresTimer::Start() {
start_ticks_ = GetCurrentTicks();
}
inline uint64 HighresTimer::GetCurrentTicks() {
return mach_absolute_time();
}
inline uint64 HighresTimer::GetElapsedTicks() const {
return start_ticks_ - GetCurrentTicks();
}
#endif // CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_MAC_H_
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