Invalid Memory Access

[Watsons]

Hi,

sorry I am rather new to JNA.

I have the following line of codes.

#pragma once
#include "barcodeImage.h"

#define K120_HANDLE HANDLE

int WINAPI setImage(K120_HANDLE hnd, unsigned char *pImage, int len, int imgType);

I use JNAerator to generate the JNA Interface file, with some amendments.

//    public int setImage(Pointer hnd, ByteBuffer pImage, int len, int format);
//    public int setImagePointer hnd, ByteByReference pImage, int len, int format);
//    public NativeLong setImage(Pointer hnd, Pointer pImage, long len, long format);
//    public NativeLong setImage(Pointer hnd, byte[] pImage, long len, long format);
    public int setImage(Pointer hnd, Pointer pImage, int len, int format);

I have tried various combinations of parameters by I am still getting the Invalid Memory Access.

java.lang.Error: Invalid memory access
    at com.sun.jna.Native.invokeInt(Native Method)
    at com.sun.jna.Function.invoke(Function.java:390)
    at com.sun.jna.Function.invoke(Function.java:323)
    at com.sun.jna.Library$Handler.invoke(Library.java:236)

Can someone kindly advise how I can resolved this error?


Thanks

[L Will Ahonen]

Hi,

You need to post more source. One of your Pointers points to invalid data, how are they initialized in the sample code vs your Java code?

BR,

Will

[Watsons]

Hi Will,

 

Sorry I am not sure what you mean by Pointers pointing to invalid data? Could you please elaborate?

 

As requested, here is how I called them.

 

PointerByReference ptrRef = new PointerByReference();
Pointer ptrImage;
byte byteImage[];

int nRet = TestJna.INSTANCE.initialise(ptrRef.getPointer());

byteImage = fileToByte("sample.bmp");
ptrImage = new Memory(byteImage.length);
ptrImage.write(0, byteImage, 0, byteImage.length);

nRet = TestJna.INSTANCE.setImage(ptrRef.getPointer(), ptrImage, byteImage.length, 1);

and the JNA interface file is

 

public interface TestJna extends StdCallLibrary {

   public static final TestJna INSTANCE = (TestJna) Native.loadLibrary("TestJna", TestJna.class);

   public int initialise(Pointer pQtf);

   public int setImage(Pointer hnd, Pointer pImage, int len, int format);

}

 

The first JNA call to initialise is ok. It always fails on the second JNA call to setImage.

 

 

Thanks

[L Will Ahonen]

Hi,

Not sure how that is supposed to be called, as we're missing a crucial puzzle piece (the C code you're trying to adapt). From a "this is how things are often implemented" perspective, it would probably be

PointerByReference willReceiveHandle=new PointerByReference();

int nRet = TestJna.INSTANCE.initialise(willReceiveHandle); // Probably will write into your PointerByReference, that's how things usually go together

Pointer handleReceived=willReceiveHandle.value();

Pointer ptrImage;

byte byteImage[];

byteImage = fileToByte("sample.bmp"); 

ptrImage = new Memory(byteImage.length);

ptrImage.write(0, byteImage, 0, byteImage.length);

nret=TestJna.INSTANCE.setImage(handleReceived, ptrImage, byteImage.length, 1);

but you really need to post the C sample code so we can help you with this.

Will

[Watsons]

Hi Will,

 

I am afraid I don't have any sample of how it should be called in C.

I only have the API document...

 

I hope this helps?

 

int WINAPI initialise(K120_HANDLE *hnd);

Description:
Initialize environment before any function call.

Arguments:
Name  I/O    Description
hnd   output handle

int WINAPI setImage(K120_HANDLE hnd, unsigned char *pImage, int len, int imgType

);

Description:

Input image which will be analysed.

Arguments:

Name        Description

hnd            handle returned by initialise funciton

pImage      image buffer pointer

len  image buffer length

imgType    image format

[L Will Ahonen]

Hi,

From that api description it looks like my code below probably will work. Do you know what format the software is expecting for the image?

Will