Re: Forth DLL and Java

Hi Roger,

Roger Dube (2004-03-12 10:56):

> Has anyone tried to interface a Forth-generated DLL to Java so that
> Java can call it?

Not until right now, but it turns out that it is quite doable.

Assuming you have the following Java code

  class ForthTest {
    public native static int fsquare(int x);
    static {
      System.loadLibrary("jniforth");
    }
    public static void main(String args[]) {
      System.out.println("2*2=" + fsquare(2));
    }
  }

you can compile it

  javac ForthTest.java
  javah -jni ForthTest

and take a look at the newly generated ForthTest.h

So with the following piece of Forth code

  : SQUARE ( jni class n -- n )
>R 2DROP R> \ no callbacks to java needed
    DUP * ;

  AS Java_ForthTest_fsquare 3 EXPORT: SQUARE
  PROGRAM jniforth.dll

you can compile the DLL needed to run the program.

CMD> java ForthTest
2*2=4

There is a JNI intro in the Java docs and some tutorials on the web on
JNI can be found, too.

  http://java.sun.com/docs/books/tutorial/native1.1/stepbystep/index.html

is quite good.

> I hear that Java has specific demands for headers in
> DLL's that it will "talk to", and it would be helpful to know how to
> create such a header or interface. - Roger

You need "fully specified and mangled" names ...
Basically it's Java_package_package_Class_method, and you'll have to
look up what you need to do when overloading native methods :-)

HTH,
s.

--
Stefan Schmiedl
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