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/* ------------------------------------------------------------------------- */
/*
* A win32 implementation of JNI methods in com.vladium.utils.timing.HRTimer
* class. The author compiled it using Microsoft Visual C++ but the code
* should be easy to use with any compiler for win32 platform.
*
* For simplicity, this implementaion assumes JNI 1.2+ and omits error handling.
*
* (C) 2002, Vladimir Roubtsov [vroubtsov@illinoisalumni.org]
*/
/* ------------------------------------------------------------------------- */
#if !defined NDEBUG
#include <stdio.h>
#endif // NDEBUG
#include <windows.h>
#include "com_vladium_utils_timing_HRTimer.h"
// scale factor for converting a performancce counter reading into milliseconds:
static jdouble s_scaleFactor;
/* ------------------------------------------------------------------------- */
/*
* This method was added in JNI 1.2. It is executed once before any other
* methods are called and is ostensibly for negotiating JNI spec versions, but
* can also be conveniently used for initializing variables that will not
* change throughout the lifetime of this process.
*/
JNIEXPORT jint JNICALL
JNI_OnLoad (JavaVM * vm, void * reserved)
{
LARGE_INTEGER counterFrequency;
QueryPerformanceFrequency (& counterFrequency);
// NOTE: counterFrequency will be zero for a machine that does not have
// support for a high-resolution counter. This is only likely for very
// old hardware but for a robust implementation you should handle this
// case.
#if !defined NDEBUG
printf ("PCFrequency called: %I64d\n", counterFrequency.QuadPart);
#endif
s_scaleFactor = counterFrequency.QuadPart / 1000.0;
return JNI_VERSION_1_2;
}
/* ......................................................................... */
/*
* Class: com_vladium_utils_timing_HRTimer
* Method: getTime
* Signature: ()D
*/
JNIEXPORT jdouble JNICALL
Java_com_vladium_utils_timing_HRTimer_getTime (JNIEnv * e, jclass cls)
{
LARGE_INTEGER counterReading;
QueryPerformanceCounter (& counterReading);
return counterReading.QuadPart / s_scaleFactor;
}
/* ------------------------------------------------------------------------- */
/* end of file */
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