Using DLL

Hi,

I'm trying to write a program in Java which detects how long a computer has been idle. This can't be accomplished in pure Java so I have to interface with some C/C++ code. I found a suitable Windows DLL at http://www.codeproject.com/dll/trackuseridle.asp.

The header for the DLL looks like this:

Code:

__declspec(dllimport) BOOL IdleTrackerInit();
__declspec(dllimport) void IdleTrackerTerm();
__declspec(dllimport) DWORD IdleTrackerGetLastTickCount();

I've written the following C to try and use the functionality provided by the DLL from within Java:

Code:

#include "IdleTracker.h"
#include "IdleTimer.h"
#include <jni.h>
#include <windows.h>

#define MILLISECONDS 1000

JNIEXPORT jboolean JNICALL 
Java_IdleTimer_init(JNIEnv *env, jobject obj) 
{
  return (jboolean)IdleTrackerInit();
}
JNIEXPORT void JNICALL 
Java_IdleTimer_terminate(JNIEnv *env, jobject obj) 
{
  IdleTrackerTerm();
}
JNIEXPORT jint JNICALL 
Java_IdleTimer_idleTime(JNIEnv *env, jobject obj) 
{
  return (jint)(GetTickCount() - IdleTrackerGetLastTickCount()) / MILLISECONDS;
}

However, when I try to compile with GCC, I get the following errors:

c:\windows\TEMP/cc22zcgb.o(.text+0x7):idletime.c: undefined reference to `_imp__IdleTrackerInit'
c:\windows\TEMP/cc22zcgb.o(.text+0x1d):idletime.c: undefined reference to `_imp__IdleTrackerTerm'
c:\windows\TEMP/cc22zcgb.o(.text+0x36):idletime.c: undefined reference to `_imp__IdleTrackerGetLastTickCount'

I know my Java and a good deal of C but nothing as far as C++ or Windows/DLLs. I wasn't sure if trying to access a C++ DLL from C was my problem.

Can anyone point me in the right direction to solve the problem? Any help much appreciated.

Originally Posted by hyvas

Code:

#include "IdleTracker.h"
#include "IdleTimer.h"
#include <jni.h>
#include <windows.h>

I'm not sure, but unless jni.h is inside **path_to_msvc++**\Include\, shouldn't it be double quoted (#include "jni.h")?

AFAIK __declspec(dllimport) is a MSVC qualifier so getting it to work with GCC will be difficult before you get to the troubles of name mangling

Thanks. I'll try giving MSVC a go.