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| /* File :
This file implements a microsecond precision clock.
We can start it (reset to zero), watch it (getting the elapsed time from start in many units)
We wan also ask it to wait until a specified time.
Remark:
In Windows, the millisecond is the atomic time unit for the followings operations:
* waiting without CPU usage (with Sleep)
* getting software interuptions. In this latter case, only a precision of 10 ms is garanted in practice.
It is always possible to get an accurate time (in microseconds) by requesting a hardware clock on the mother board (if any)
However, it it not possible to use this clock to get sub-microseconds interrupts neither to sleep peacefully.
The solution I implemented is to sleep peacefully the desired numbers of microseconds then to actively wath the precision clock.
----------------------------------------------------------------------------------*/
#pragma once
#pragma message( "Including " __FILE__ )
#define MICROCLOCK_H
// #include "Globals.h"
// #include "utils.h"
class CMicroClock {
protected:
__int64 n_Start ; // time when start was called
__int64 n_Watch ; // time when couter was last watched
__int64 n_CountsPerSec ; // counter frequeny (machine dependent)
__int64 n_llCorrection ; // elapsed time of a start-watch sequence
public:
CMicroClock(void); // calculates frequency and calibrate correction factor
__int64 Start(void); // get current time in start
void Start(__int64 newStartValue); // Change the value of the start member
__int64 GetCurrentCount(void); // get current time in GetCurrentCount
// Results in seconds in double
double GetDurationSec(void) ; // calculates time between start and GetCurrentCount members
double WatchSec(void) ; // call GetCurrentCount, then calculate duration
// Results in microseconds in 64 bits integer
__int64 GetDurationMicro(void) ; // calculates time between start and GetCurrentCount members
__int64 Watch(void) ; // call GetCurrentCount, then calculate duration
__int64 WatchAndRestart(void) ; // call Watch,then use the watch date as new zero
// Results in milli seconds in long with loss of precision (unsigned long is good because it can be mapped on a dialog)
unsigned WatchMilliSec(void) ;
// Offsets the start
void Offset(__int64 offset) ; // add offset to Start as many times as possible but maintains (start <= watch)
// Provide conversions between time units and counter
double Count2sec (__int64 count) ;
__int64 Count2microsec (__int64 count) ;
__int64 Microsec2count (__int64 microsec) ;
__int64 Sec2count (double sec) ;
// wait quietly as many ms as possible with sleep,
// then wait actively the rest of the time
// a tolerance si set to allow sleeping a full millisecond even if some microseconds are missing
__int64 WaitUntil(__int64 awakeTime, __int64 round = 100) ;
};
inline CMicroClock::CMicroClock(void) {
// get frequency
LARGE_INTEGER countsPerSec; // LargeIntegers are 64 bits native integers embeded in a Union designed for compatibility with systems/compilers which does not support native 64 bits integers. The QuadPart member is the native 64 bits integer.
QueryPerformanceFrequency(&countsPerSec) ; // the current performance-counter frequency, in counts per second.
n_CountsPerSec = countsPerSec.QuadPart;
if (n_CountsPerSec == 0) throw "This computer does not support high-frequency counters. Application cannot run" ;
// Calibration
Start();
GetCurrentCount();
n_llCorrection = n_Watch - n_Start ;
// Restart in case of any use
Start() ;
}
inline __int64 CMicroClock::Start(void) {
// Sleep(10); // Ensure we will not be interrupted by any other thread for a while
QueryPerformanceCounter((LARGE_INTEGER*)&n_Start) ;
return n_Start ;
}
inline void CMicroClock::Start(__int64 newStartValue) {
n_Start = newStartValue ;
}
inline __int64 CMicroClock::GetCurrentCount(void) {
QueryPerformanceCounter((LARGE_INTEGER*)&n_Watch) ;
return n_Watch ;
}
// duration in seconds in double
inline double CMicroClock::GetDurationSec(void) {
return Count2sec(n_Watch - n_Start - n_llCorrection) ;
}
// duration in microseconds in 64 bits integer
inline __int64 CMicroClock::GetDurationMicro(void) {
return Count2microsec(n_Watch - n_Start - n_llCorrection) ;
}
inline double CMicroClock::WatchSec(void) {
GetCurrentCount() ;
return GetDurationSec() ;
}
// Convert to milli second with precision loss
inline unsigned CMicroClock::WatchMilliSec(void) {
GetCurrentCount() ;
return (unsigned)(GetDurationMicro() / 1000) ;
}
inline __int64 CMicroClock::Watch(void) {
GetCurrentCount() ;
return GetDurationMicro() ;
}
inline __int64 CMicroClock::WatchAndRestart(void) {
__int64 r = Watch() ;
n_Start = n_Watch ;
return r ;
}
inline void CMicroClock::Offset(__int64 offset) {
GetCurrentCount() ;
n_Start += offset * ((n_Watch - n_Start) / offset) ;
}
inline double CMicroClock::Count2sec (__int64 count) {
static double k = 1.0 / (double)n_CountsPerSec ;
return (double)count * k ;
}
inline __int64 CMicroClock::Count2microsec (__int64 count) {
static __int64 million = 1000000 ;
return (__int64)(count * million / n_CountsPerSec) ;
}
inline __int64 CMicroClock::Microsec2count (__int64 microsec) {
static __int64 million = 1000000 ;
return (__int64)(microsec * n_CountsPerSec / million) ;
}
inline __int64 CMicroClock::Sec2count (double sec) {
return (__int64)(sec * n_CountsPerSec) ;
}
inline __int64 CMicroClock::WaitUntil(__int64 awakeTime, __int64 round /* = 100 */ ) {
__int64 enter = Watch(), quit ;
__int64 sleep_micro = awakeTime - enter ;
unsigned sleep_ms ;
if (sleep_micro > 1000 - round) {
sleep_ms = max(1U, (unsigned)(sleep_micro/1000)) ;
Sleep(sleep_ms) ; // quiet wait, in ms
}
while ((quit = Watch()) < awakeTime) ;
return quit - enter ;
} |
[C++][SOURCE] Un "clock" réel, à la microseconde près
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