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/*
* Copyright 2009, Google Inc.
* 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.
*/
#ifndef O3D_STATSREPORT_COMMON_HIGHRES_TIMER_LINUX_H_
#define O3D_STATSREPORT_COMMON_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;
(void)gettimeofday(&tv, 0);
return tv.tv_sec * MICROS_IN_SECOND + tv.tv_usec;
}
inline uint64 HighresTimer::GetElapsedTicks() const {
return start_ticks_ - GetCurrentTicks();
}
#endif // O3D_STATSREPORT_COMMON_HIGHRES_TIMER_LINUX_H_
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