package com.jtstand.jna; /** * * @author albert_kurucz */ import com.sun.jna.Library; import com.sun.jna.Native; import com.sun.jna.Platform; import com.sun.jna.ptr.IntByReference;

/** Simple example of JNA interface mapping and usage. */ public class HelloVisa {

// This is the standard, stable way of mapping, which supports extensive // customization and mapping of Java to native types. public interface NiVisaLibrary extends Library {

NiVisaLibrary INSTANCE = (NiVisaLibrary) Native.loadLibrary((Platform.isWindows() ? "visa32" : "????"), NiVisaLibrary.class);

//void printf(String format, Object... args); int viOpenDefaultRM(IntByReference sesn);

int viOpen(int sesn, String rsrcName, int accessMode, int openTimeout, IntByReference vi); }

public static void main(String[] args) { int status; System.out.println("viOpenDefaultRM..."); IntByReference sesn = new IntByReference(); status = NiVisaLibrary.INSTANCE.viOpenDefaultRM(sesn); System.out.println("Status:" + status);

System.out.println("viOpen..."); IntByReference vi = new IntByReference(); status = NiVisaLibrary.INSTANCE.viOpen(sesn.getValue(), "COM1", 0, 0, vi); System.out.println("Status:" + status);

} }

package com.jtstand.jna;

import com.sun.jna.*;

/** Simple example of JNA direct mapping. * Fewer automatic type conversions are supported with this method */ public class HelloDirectVisa {

static { Native.register(Platform.isWindows() ? "visa32" : "????"); }

public static native int viOpenDefaultRM(int[] sesn);

public static native int viOpen(int sesn, String rsrcName, int accessMode, int openTimeout, int[] vi);

public static void main(String[] args) { int status; System.out.println("viOpenDefaultRM..."); int[] sesn = new int[1]; status = viOpenDefaultRM(sesn); System.out.println("Status:" + status);

System.out.println("viOpen..."); int[] vi = new int[1]; status = viOpen(sesn[0], "COM1", 0, 0, vi); System.out.println("Status:" + status); } }

java.lang.ExceptionInInitializerError Caused by: java.lang.NullPointerException at java.lang.reflect.Array.getLength(Native Method) at com.sun.jna.Structure$FFIType.<init>(Structure.java:1432) at com.sun.jna.Structure$FFIType.get(Structure.java:1483) at com.sun.jna.Structure$FFIType.get(Structure.java:1450) at com.sun.jna.Structure$FFIType.getSignature(Structure.java:1492) at com.sun.jna.Native.register(Native.java:940) at com.sun.jna.Native.register(Native.java:888) at com.jtstand.jna.HelloDirectVisa.<clinit>(HelloDirectVisa.java:11)

On Jun 22, 2009, at 10:08 AM, Albert Kurucz wrote:

Can I use By-reference argument with the experimental direct calling

You can use a primitive array of length one, which has the same result.

Type mappings for interface and direct mapping are the same; direct mapping does not yet implement NativeMapped or TypeMapper conversions.

You'll get runtime errors if you attempt to use an unsupported argument type.