在 JNA 中传递参数

Question

This code fills a generated data structure SCANNER_FULL_PLUS_EX and then calls a function ScanReadFull_PlusEx(). Both are generated by JNAerator and supposed to create some files like Scan_F.bmp etc.

For 64 bit java on windows 10 6-bit the file names in byte[512] do not pass properly to the dll. Most of the time file names are null

    public short SCANTEST(String fileName) {

        StringBuilder BitmapNameF = new StringBuilder();
        StringBuilder BitmapNameR = new StringBuilder();
        StringBuilder BitmapNameF_IR = new StringBuilder();
        StringBuilder BitmapNameR_IR = new StringBuilder();
        StringBuilder BitmapNameF_UV = new StringBuilder();
        StringBuilder BitmapNameR_UV = new StringBuilder();

        SCANNER_FULL_PLUS_EX m_ScanFullPlusEx = new SCANNER_FULL_PLUS_EX();

        m_ScanFullPlusEx.Version = 0;
        m_ScanFullPlusEx.BrightnessFront = 100;
        m_ScanFullPlusEx.ThresholdFront = 100;
        m_ScanFullPlusEx.BrightnessRear = 100;
        m_ScanFullPlusEx.ThresholdRear = 100;
        m_ScanFullPlusEx.BitsPerPixel = 8;
        m_ScanFullPlusEx.ScanMode = 2;

        m_ScanFullPlusEx.ScanModeIR = 0;
        m_ScanFullPlusEx.ScanModeUV = 0;

        m_ScanFullPlusEx.dwImageWidth = 0;
        m_ScanFullPlusEx.dwImageHeight = 0;

        m_ScanFullPlusEx.pImageFront = new NativeLong(0);
        m_ScanFullPlusEx.dwImageSizeFront = 0;
        m_ScanFullPlusEx.pImageRear = new NativeLong(0);
        m_ScanFullPlusEx.dwImageSizeRear = 0;
        m_ScanFullPlusEx.pIR_ImageFront = new NativeLong(0);
        m_ScanFullPlusEx.dwIR_ImageSizeFront = 0;
        m_ScanFullPlusEx.pIR_ImageRear = new NativeLong(0);
        m_ScanFullPlusEx.dwIR_ImageSizeRear = 0;
        m_ScanFullPlusEx.pUV_ImageFront = new NativeLong(0);
        m_ScanFullPlusEx.dwUV_ImageSizeFront = 0;
        m_ScanFullPlusEx.pUV_ImageRear = new NativeLong(0);
        m_ScanFullPlusEx.dwUV_ImageSizeRear = 0;

        BitmapNameF.append(fileName + "F.bmp");
        BitmapNameR.append(fileName + "R.bmp");
        BitmapNameF_IR.append(fileName + "F_IR.bmp");
        BitmapNameR_IR.append(fileName + "R_IR.bmp");
        BitmapNameF_UV.append(fileName + "F_UV.bmp");
        BitmapNameR_UV.append(fileName + "R_UV.bmp");

        m_ScanFullPlusEx.ImageNameRear = Native.toByteArray(BitmapNameR.toString());
        m_ScanFullPlusEx.ImageNameFront = Native.toByteArray(BitmapNameF.toString());
        m_ScanFullPlusEx.IR_ImageNameFront = Native.toByteArray(BitmapNameF_IR.toString());
        m_ScanFullPlusEx.IR_ImageNameRear = Native.toByteArray(BitmapNameR_IR.toString());
        m_ScanFullPlusEx.UV_ImageNameFront = Native.toByteArray(BitmapNameF_UV.toString());
        m_ScanFullPlusEx.UV_ImageNameRear = Native.toByteArray(BitmapNameR_UV.toString());

        // wrap in 512 buffer
        byte[] f1 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.ImageNameRear.length;i++) f1[i]=m_ScanFullPlusEx.ImageNameRear[i]; m_ScanFullPlusEx.ImageNameRear = f1;
        byte[] f2 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.ImageNameFront.length;i++) f2[i]=m_ScanFullPlusEx.ImageNameFront[i]; m_ScanFullPlusEx.ImageNameFront = f2;
        byte[] f3 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.IR_ImageNameFront.length;i++) f3[i]=m_ScanFullPlusEx.IR_ImageNameFront[i]; m_ScanFullPlusEx.IR_ImageNameFront = f3;
        byte[] f4 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.IR_ImageNameRear.length;i++) f4[i]=m_ScanFullPlusEx.IR_ImageNameRear[i]; m_ScanFullPlusEx.IR_ImageNameRear = f4;
        byte[] f5 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.UV_ImageNameFront.length;i++) f5[i]=m_ScanFullPlusEx.UV_ImageNameFront[i]; m_ScanFullPlusEx.UV_ImageNameFront = f5;
        byte[] f6 = new byte[512]; for (int i=0; i<m_ScanFullPlusEx.UV_ImageNameRear.length;i++) f6[i]=m_ScanFullPlusEx.UV_ImageNameRear[i]; m_ScanFullPlusEx.UV_ImageNameRear = f6;

        short ret = MB2Library.INSTANCE.ScanReadFull_PlusEx(ByteBuffer.wrap(Native.toByteArray(gPort.Global)), m_ScanFullPlusEx, MB2Library.SCAN_OUTPUT_FORMAT_FILE_BMP);

        return ret;
    }

C header file for the structure.

typedef struct
{
        int Version;
        int BrightnessFront;
        int ThresholdFront;

        int BrightnessRear;
        int ThresholdRear;
        int BitsPerPixel;

        int ScanMode;   // Front/Rear/Front-Rear
        int ScanModeIR; // ( not yet implemented ) IR Front/Rear/Front-Rear
        int ScanModeUV; // ( not yet implemented ) UV Front/Rear/Front-Rear

        DWORD dwImageWidth;
        DWORD dwImageHeight;

        // Front CIS Image
        HANDLE pImageFront;
        DWORD dwImageSizeFront;

        // Rear CIS Image
        HANDLE pImageRear;
        DWORD dwImageSizeRear;

        // Front IR Image
        HANDLE pIR_ImageFront;
        DWORD dwIR_ImageSizeFront;

        // Rear IR Image
        HANDLE pIR_ImageRear;
        DWORD dwIR_ImageSizeRear;

        // Front UV Image
        HANDLE pUV_ImageFront;
        DWORD dwUV_ImageSizeFront;

        // Rear UV Image
        HANDLE pUV_ImageRear;
        DWORD dwUV_ImageSizeRear;

        // images path
        TCHAR ImageNameFront[512];
        TCHAR ImageNameRear[512];
        TCHAR IR_ImageNameFront[512];
        TCHAR IR_ImageNameRear[512];
        TCHAR UV_ImageNameFront[512];
        TCHAR UV_ImageNameRear[512];

} SCANNER_FULL_PLUS_EX;

typedef SCANNER_FULL_PLUS_EX *PSCANNER_FULL_PLUS_EX;

EDIT 1:

package mb2;

import java.util.StringTokenizer;

import java.util.Arrays;
import java.util.List;

import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.NativeLibrary;
import com.sun.jna.NativeLong;
import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.ptr.ByReference;
import com.sun.jna.ptr.PointerByReference;
import com.sun.jna.ptr.IntByReference;
import com.sun.jna.ptr.ByteByReference;
import com.sun.jna.ptr.DoubleByReference;
import com.sun.jna.ptr.FloatByReference;
import com.sun.jna.ptr.LongByReference;
import com.sun.jna.ptr.NativeLongByReference;
import com.sun.jna.ptr.ShortByReference;

public class SCANNER_FULL_PLUS_EX extends Structure {
    public int Version;
    public int BrightnessFront;
    public int ThresholdFront;
    public int BrightnessRear;
    public int ThresholdRear;
    public int BitsPerPixel;
    /** Front/Rear/Front-Rear */
    public int ScanMode;
    /** ( not yet implemented ) IR Front/Rear/Front-Rear */
    public int ScanModeIR;
    /** ( not yet implemented ) UV Front/Rear/Front-Rear */
    public int ScanModeUV;
    public int dwImageWidth;
    public int dwImageHeight;
    /**
     * Front CIS Image<br>
     * C type : HANDLE
     */
    public NativeLong pImageFront;
    public int dwImageSizeFront;
    /**
     * Rear CIS Image<br>
     * C type : HANDLE
     */
    public NativeLong pImageRear;
    public int dwImageSizeRear;
    /**
     * Front IR Image<br>
     * C type : HANDLE
     */
    public NativeLong pIR_ImageFront;
    public int dwIR_ImageSizeFront;
    /**
     * Rear IR Image<br>
     * C type : HANDLE
     */
    public NativeLong pIR_ImageRear;
    public int dwIR_ImageSizeRear;
    /**
     * Front UV Image<br>
     * C type : HANDLE
     */
    public NativeLong pUV_ImageFront;
    public int dwUV_ImageSizeFront;
    /**
     * Rear UV Image<br>
     * C type : HANDLE
     */
    public NativeLong pUV_ImageRear;
    public int dwUV_ImageSizeRear;
    /**
     * images path<br>
     * C type : TCHAR[512]
     */
    public byte[] ImageNameFront = new byte[512];
    /** C type : TCHAR[512] */
    public byte[] ImageNameRear = new byte[512];
    /** C type : TCHAR[512] */
    public byte[] IR_ImageNameFront = new byte[512];
    /** C type : TCHAR[512] */
    public byte[] IR_ImageNameRear = new byte[512];
    /** C type : TCHAR[512] */
    public byte[] UV_ImageNameFront = new byte[512];
    /** C type : TCHAR[512] */
    public byte[] UV_ImageNameRear = new byte[512];
    public SCANNER_FULL_PLUS_EX() {
        super();
    }
    protected List<String> getFieldOrder() {
        return Arrays.asList("Version", "BrightnessFront", "ThresholdFront", "BrightnessRear", "ThresholdRear", "BitsPerPixel", "ScanMode", "ScanModeIR", "ScanModeUV", "dwImageWidth", "dwImageHeight", "pImageFront", "dwImageSizeFront", "pImageRear", "dwImageSizeRear", "pIR_ImageFront", "dwIR_ImageSizeFront", "pIR_ImageRear", "dwIR_ImageSizeRear", "pUV_ImageFront", "dwUV_ImageSizeFront", "pUV_ImageRear", "dwUV_ImageSizeRear", "ImageNameFront", "ImageNameRear", "IR_ImageNameFront", "IR_ImageNameRear", "UV_ImageNameFront", "UV_ImageNameRear");
    }
    public SCANNER_FULL_PLUS_EX(Pointer peer) {
        super(peer);
    }
    public static class ByReference extends SCANNER_FULL_PLUS_EX implements Structure.ByReference {

    };
    public static class ByValue extends SCANNER_FULL_PLUS_EX implements Structure.ByValue {

    };
}

Answer 1

Welcome to the wonderful world of character encoding .

You're using Native.toByteArray() with only the String argument. This returns:

A NUL-terminated byte buffer equivalent to the given String, using the encoding returned by getDefaultStringEncoding().

It is generally a bad practice to leave encoding unspecified when converting between Strings and byte arrays. In this case, you actually do want the default system encoding but it's useful to specify that, and, in the process, understand what it's doing.

The default Windows encoding is UTF-16, which uses 16 bits to represent characters ( wchar_t in C). For ASCII character strings, like the ones you are using, that means your byte array ends up with alternating 0 bytes and 8-bit character bytes. (Feel free to instrument your code and output Arrays.toString(f1) to see this for yourself!)

The C structure uses arrays of TCHAR . This can be either a single byte or two bytes, depending on your encoding (which will match Native.toByteArray() ).

So the default encoding here is fine, except that you do need to know what that encoding is, in order to properly size your structure. You are passing 512-byte arrays when you probably need 512-TCHAR arrays (1024 bytes).

JNA structures must know their total byte size, however, and TCHAR isn't mapped in JNA. So you have to figure out CHAR_WIDTH and multiply 512 by that value in the structure. (Search JNA source code for CHAR_WIDTH for ample examples of this.)

(EDIT 1)

Thanks for providing the JNA mapping. Generally the very first thing to look at when a JNA-mapped function/structure misbehaves is the type mapping. In your case, in addition to the incorrect TCHAR mapping to byte as described above, you have mapped the HANDLE as a NativeLong . This doesn't work on Windows: HANDLE extends from PointerType and Pointers match operating system bitness, so are 64-bit on 64-bit Windows. Windows LONG on the other hand (and thus NativeLong on Windows) is always a 32-bit type.

So to summarize, you need (at least) the following changes:

1. Change the HANDLE types to map to JNA's WinNT.HANDLE class

2. Change the TCHAR byte width to match character width. One way to do this is to insert this at the top of your class (or anywhere in your project, public so it's accessible):

    private static final int CHAR_WIDTH = Boolean.getBoolean("w32.ascii")? 1: 2;

Then in your byte[] declarations, multiply 512 * CHAR_WIDTH to get the correct width.