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