原文链接
/* ------------------------------------------------------------------------- */
/*
* An implementation of JNI methods in com.vladium.utils.SystemInformation
* 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 [vlad@trilogy.com]
*/
/* ------------------------------------------------------------------------- */
#include <windows.h>
#include <process.h>
#include <winbase.h>
#include "com_vladium_utils_SystemInformation.h"
static jint s_PID;
static HANDLE s_currentProcess;
static int s_numberOfProcessors;
/* ------------------------------------------------------------------------- */
/*
* A helper function for converting FILETIME to a LONGLONG [safe from memory
* alignment point of view].
*/
static LONGLONG
fileTimeToInt64 (const FILETIME * time)
{
ULARGE_INTEGER _time;
_time.LowPart = time->dwLowDateTime;
_time.HighPart = time->dwHighDateTime;
return _time.QuadPart;
}
/* ......................................................................... */
/*
* 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)
{
SYSTEM_INFO systemInfo;
s_PID = _getpid ();
s_currentProcess = GetCurrentProcess ();
GetSystemInfo (& systemInfo);
s_numberOfProcessors = systemInfo.dwNumberOfProcessors;
return JNI_VERSION_1_2;
}
/* ......................................................................... */
/*
* Class: com_vladium_utils_SystemInformation
* Method: getProcessID
* Signature: ()I
*/
JNIEXPORT jint JNICALL
Java_com_vladium_utils_SystemInformation_getProcessID (JNIEnv * env, jclass cls)
{
return s_PID;
}
/* ......................................................................... */
/*
* Class: com_vladium_utils_SystemInformation
* Method: getProcessCPUTime
* Signature: ()J
*/
JNIEXPORT jlong JNICALL
Java_com_vladium_utils_SystemInformation_getProcessCPUTime (JNIEnv * env, jclass cls)
{
FILETIME creationTime, exitTime, kernelTime, userTime;
GetProcessTimes (s_currentProcess, & creationTime, & exitTime, & kernelTime, & userTime);
return (jlong) ((fileTimeToInt64 (& kernelTime) + fileTimeToInt64 (& userTime)) /
(s_numberOfProcessors * 10000));
}
/* ......................................................................... */
/* define min elapsed time (in units of 10E-7 sec): */
#define MIN_ELAPSED_TIME (10000)
/*
* Class: com_vladium_utils_SystemInformation
* Method: getProcessCPUUsage
* Signature: ()D
*/
JNIEXPORT jdouble JNICALL
Java_com_vladium_utils_SystemInformation_getProcessCPUUsage (JNIEnv * env, jclass cls)
{
FILETIME creationTime, exitTime, kernelTime, userTime, nowTime;
LONGLONG elapsedTime;
GetProcessTimes (s_currentProcess, & creationTime, & exitTime, & kernelTime, & userTime);
GetSystemTimeAsFileTime (& nowTime);
/*
NOTE: win32 system time is not very precise [~10ms resolution], use
sufficiently long sampling intervals if you make use of this method.
*/
elapsedTime = fileTimeToInt64 (& nowTime) - fileTimeToInt64 (& creationTime);
if (elapsedTime < MIN_ELAPSED_TIME)
return 0.0;
else
return ((jdouble) (fileTimeToInt64 (& kernelTime) + fileTimeToInt64 (& userTime))) /
(s_numberOfProcessors * elapsedTime);
}
#undef MIN_ELAPSED_TIME
