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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 Linux.
#ifndef CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_LINUX_H_
#define CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_LINUX_H_
#include "base/basictypes.h"
#include <sys/time.h>
const uint64 MICROS_IN_SECOND = 1000000L;
// A handy class for reliably measuring wall-clock time with decent resolution.
//
// We want to measure time with high resolution on Linux. What to do?
//
// RDTSC? Sure, but how do you convert it to wall clock time?
// clock_gettime? It's not in all Linuxes.
//
// Let's just use gettimeofday; it's good to the microsecond.
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:
// Captured start time.
uint64 start_ticks_;
};
inline HighresTimer::HighresTimer() {
Start();
}
inline void HighresTimer::Start() {
start_ticks_ = GetCurrentTicks();
}
inline uint64 HighresTimer::GetTimerFrequency() {
// Fixed; one "tick" is one microsecond.
return MICROS_IN_SECOND;
}
inline uint64 HighresTimer::GetCurrentTicks() {
timeval tv;
gettimeofday(&tv, 0);
return tv.tv_sec * MICROS_IN_SECOND + tv.tv_usec;
}
inline uint64 HighresTimer::GetElapsedTicks() const {
return start_ticks_ - GetCurrentTicks();
}
#endif // CHROME_BROWSER_SYNC_UTIL_HIGHRES_TIMER_LINUX_H_
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