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Call a 86x Dll from Java

Am trying to call a x86 DLL that I created using VC 6, from a java project on Eclipse, first try I got an error saying that I can't call a x86 DLL from a x64 envirement and that the DLL can't be loaded. So I installed a x86 jre and I have no more problem to charge the DLL.
But when I try to call my c++ function I get the following exception:
Exception in thread "main" java.lang.UnsatisfiedLinkError: mm.SimpleDLL.SimpleDLL_Calculation_Add(II)I
Can someone please help me ?
Thank you.
SimpleDLL.h
#ifndef SIMPLE_DLL_H
#define SIMPLE_DLL_H
namespace SimpleDll
{
extern class Calculation
{
public:
static __declspec(dllexport) int Add(int a, int b);
};
}
#endif SIMPLE_DLL_H
SimpleDLL.cpp
#include "SimpleDll.h"
namespace SimpleDll
{
int Calculation::Add(int a, int b)
{ return a + b; }
}
SimpleDLL.java
package mm;
public class SimpleDLL {
static
{
System.load("D:\\SimpleDLL.dll");
}
public static void main(String ar[])
{
System.out.println("Hello world from Java");
SimpleDLL t=new SimpleDLL();
int x = t.SimpleDLL_Calculation_Add(6, 7);
System.out.println("Resultat "+x);
}
public native int SimpleDLL_Calculation_Add(int a, int b);
}
Exported DLL Functions View
Resolved using the JNA library, I used this link to walkthrough

You need to build a 32-bit DLL and a .h file using javah for the exact signature Java expects. It is usually something like
JNIEXPORT jboolean JNICALL Java_Sample1_booleanMethod
(JNIEnv *, jobject, jboolean);
from https://medium.com/#bschlining/a-simple-java-native-interface-jni-example-in-java-and-scala-68fdafe76f5f
An alternative approach is to use a library like JNA or JNR-FFI which allow you to bind to a C library without writing this bridging code.

NuiGetSensorCount Java JNA

I am just learning how to use Java JNA, and I am trying to call a simple function from the Microsoft Kinect SDK. (NuiGetSensorCount) which just returns the number of connected kinects.
Here is my attempt:
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.Pointer;
public class Driver {
public interface KinectLibrary extends Library {
KinectLibrary INSTANCE = (KinectLibrary)Native.loadLibrary(("Microsoft.Kinect"),KinectLibrary.class);
//_Check_return_ HRESULT NUIAPI NuiGetSensorCount( _In_ int * pCount );
NativeLong NuiGetSensorCount(Pointer pCount);
}
public static void main(String[] args) {
Pointer devCount = new Pointer(0);
KinectLibrary.INSTANCE.NuiGetSensorCount(devCount);
System.out.println("Devices:"+devCount.getInt(0));
}
}
But I get:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'NuiGetSensorCount': The specified procedure could not be found.
at com.sun.jna.Function.<init>(Function.java:208)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:536)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:513)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:499)
at com.sun.jna.Library$Handler.invoke(Library.java:199)
at $Proxy0.NuiGetSensorCount(Unknown Source)
at Driver.main(Driver.java:30)
Can anybody provide help of how to change my code so it finds the correct native function? And also provide some information/reference so that I could try to debug this myself (some way to see what function Java JNA is looking for, and compare it to what the .dll contains)

I figured out my problem. First, I used a program called dependency walker http://dependencywalker.com/ to view all the symbols in the DLL and I determined that the DLL I was using (Microsoft.Kinect.dll) did not actually contain the function I was trying to call. I found out that Kinect10.dll was the one I needed. After changing that, I had to make a small change to my pointer and it works perfectly!
Here is the fixed code.
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.ptr.IntByReference;
import com.sun.jna.win32.StdCallLibrary;
public class Driver{
public interface KinectLibrary extends StdCallLibrary {
KinectLibrary INSTANCE = (KinectLibrary)Native.loadLibrary(("Kinect10"),KinectLibrary.class);
//_Check_return_ HRESULT NUIAPI NuiGetSensorCount( _In_ int * pCount );
NativeLong NuiGetSensorCount(IntByReference pCount);
}
public static void main(String[] args) {
IntByReference a = new IntByReference();
KinectLibrary.INSTANCE.NuiGetSensorCount(a);
System.out.println("Devices:"+a.getValue());
}
}

Using DLL in java through JNA

I am using dll in java using JNA, but i am getting below error
Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'GetStatus': The specified procedure could not be found.
Not getting how to resolve this issue?
Please help.
Here is java code
import com.sun.jna.Library;
import com.sun.jna.Native;
/** Simple example of native library declaration and usage. */
public class First {
public interface TEST extends Library {
public String GetStatus();
}
public static void main(String[] args) {
TEST obj = (TEST ) Native.loadLibrary("TEST ", TEST .class);
System.out.println( obj.GetStatus());
}
}

This Nugget is super easy to use and works perfectly. https://www.nuget.org/packages/UnmanagedExports
You need Visual Studio 2012 (express).
Once installed, just add [RGiesecke.DllExport.DllExport] before any static function you want to export. That's it!
Example:
C#
[RGiesecke.DllExport.DllExport]
public static int YourFunction(string data)
{
/*Your code here*/
return 1;
}
Java
Add the import at the top:
import com.sun.jna.Native;
Add the interface in your class. Its your C# function name preceded by the letter "I":
public interface IYourFunction extends com.sun.jna.Library
{
public int YourFunction(String tStr);
};
Call your DLL where you need it in your class:
IYourFunction iYourFunction = (IYourFunction )Native.loadLibrary("full or relative path to DLL withouth the .dll extention", IYourFunction.class);//call JNA
System.out.println("Returned: " + IYourFunction.YourFunction("some parameter"));
EDIT:
If the DLL is 32bit, the JDK/JRE has to be 32bit as well. Add the following check to your code:
if(!System.getProperty("os.arch").equals("x86")) {
throw new Exception(".NET DLL " + "32bits JRE/JDK is required. Currently using " + System.getProperty("os.arch") + ".\r\nTry changing your PATH environement variable.");
}

JNA access to 64-bit DLL (Windows7 64-bit)

Could you please advice. I have simple DLL (under Windows 7 64-bit) and simple Java code with JNA access to this DLL.
The problem is when I use 64-bit version of this DLL looks like I can't get parameter from Java in my DLL test function giveIntGetInt, and I have no problem when I use 32-bit DLL.
Where I was wrong?
Thank you!
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;
import com.sun.jna.Pointer;
/** Simple example of native library declaration and usage. */
public class HelloWorld {
public interface simpleDLL extends Library {
simpleDLL INSTANCE = (simpleDLL) Native.loadLibrary(
(Platform.isWindows() ? "simpleDLL" : "simpleDLLLinuxPort"), simpleDLL.class);
int giveIntGetInt(int a); // int giveIntGetInt(int a);
}
public static void main(String[] args) {
int b = simpleDLL.INSTANCE.giveIntGetInt(2);
System.out.println("Hello, World\n");
System.out.println(String.format("Argument %d", b));
}
}
this is C dll method:
int simpleDLL::giveIntGetInt(int a)
{
return 2*a;
}
For example, this is I've got with 64-bit dll:
Hello, World
Argument 181140
32-bit dll:
Hello, World
Argument 4

JNA - Unable to get a call from native function to a callback function

I am using JNA to call functions of a dll file.
One of the functions requires a pointer to a callback function
// Dll function
void MyFunction (*CallBackFnName);
Below is the JNA proxy interface in java
import com.sun.jna.Callback;
import com.sun.jna.Library;
import com.sun.jna.Pointer;
public interface Dll extends Library {
interface CallBackFnName extends Callback {
void callback(Pointer dataBuffer, int dataLen);
}
public void MyFunction(Dll.CallBackFnName fn);
public int StartReading(short arg1, short arg2);
}
According to the API of the dll, after passing the pointer to a callback function to the function MyFunction(*CallBackFnName), whenever you call StartReading() function it will send data to the callback function.
When I am trying to do that, It is not calling my callback function. It is not throwing any exception also.
Below is the code from which I am calling functions:
import com.sun.jna.Native;
import com.sun.jna.Pointer;
public class Start {
private static Dll dll = (Dll) Native.loadLibrary("MyDll", Dll.class);
private static Dll.CallBackFnName fn = new Dll.CallBackFnName() {
#Override
public void callback(Pointer dataBuffer, int dataLen) {
System.err.println("Callback function is called successfully");
}
};
public static void main(String[] args) throws InterruptedException {
dll.MyFunction(fn); //passed the pointer to the callback function
short arg1 = 0;
short arg2 = 0;
dll.StartReading(arg1, arg2));
Thread.sleep(10 * 1000);
}
}
After running the above code, I am getting the following on the console:
DeviceAttach: received and accepted attach for vendor id 0x3eb, product id 0x2ffd, interface 0, device handle 0x037825E8
Main Menu (active Dev/Prod/Interface/Alt. Setting: 0x3eb/0x2ffd/0/0)
Read FailReadWritePipesMenu: WDU_Transfer(control receive) failed: error 0x2000000e ("
Read Fail")
Read FailReadWritePipesMenu: WDU_Transfer(control receive) failed: error 0x2000000e ("
Read Fail")
Read FailReadWritePipesMenu: WDU_Transfer(control receive) failed: error 0x2000000e ("
Read Fail")
Transferred 0 bytes
0 0

Don't know if you still need the answer , but to anyone else who has this problem,
I had this problem before.I had to create an anonymous class as such (using the above example),
dll.myfunc(new Dll.CallBackFnName() {
#Override
public void callback(Pointer dataBuffer, int dataLen) {
System.err.println("Callback function is called successfully");
} } );
This worked for me . although i can't explain why.