SWIG Proxy Class Array Parameter

demo.cpp

#include "demo.h"
#include <iostream>
using namespace std;

void myFunction(struct MyStruct arg[], int amount)
{
  for (int i = 0; i < amount; i++) {
    cerr << " el[" << i << "] a=" << arg[i].a << ", b=" << arg[i].b << std::endl;
  }
}

demo.h

#ifndef DEMO_H
#define DEMO_H

struct MyStruct {
  int a;
  int b;
};

void myFunction(struct MyStruct arg[], int amount);

#endif /* DEMO_H */

demo.i

%module Demo

%pragma(java) jniclasscode=%{
    static {
        try {
            System.loadLibrary("demo");
        } catch (UnsatisfiedLinkError e) {
            System.err.println("Native code library failed to load: " + e.getMessage());
            throw e;
        }
    }

    private DemoJNI()
    {
        throw new IllegalStateException("Instances of class " + getClass().getSimpleName() + " should not be instantiated");
    }
%}

%pragma(java) modulecode=%{
  public static void main(String[] args) {
    MyStruct[] ms = new MyStruct[4];

    System.err.println("Java level:");
    for (int i = 0; i < 4; i++) {
      ms[i] = new MyStruct();
      ms[i].setA(i);
      ms[i].setB(i + 1);

      System.err.println(" " + ms[i].getA() + ", " + ms[i].getB());
    }

    myFunction(ms, 4);
  }
%}

%{
#include "demo.h"
%}

// In order to allow classes generated from this module to be available to other
// modules, we need to set the constructor and getCPtr method as public.
// http://www.swig.org/Doc2.0/Java.html
%include <java.swg>
SWIG_JAVABODY_PROXY(public, public, SWIGTYPE)
SWIG_JAVABODY_TYPEWRAPPER(public, public, public, SWIGTYPE)

%include <carrays.i>
%array_class(struct MyStruct, MyStructArray);

%typemap(jni) MyStruct arg[] "jobject"
%typemap(jstype) MyStruct arg[] "MyStruct[]"
%typemap(jtype) MyStruct arg[] "MyStructArray"
%typemap(javain, pre="    if ($javainput.length == 0 || $javainput.length < amount)
      throw new IllegalArgumentException(\"Must provide big enough array\");
    MyStructArray arr = new MyStructArray(amount);
    System.err.println(\"javain level:\");
    for (int i = 0; i < amount; i++) {
      arr.setitem(i, $javainput[i]);
      System.err.println(\" \" + arr.getitem(i).getA() + \", \" + arr.getitem(i).getB());
    }
    System.err.println(\"C++ level:\");") MyStruct arg[] "arr"
%typemap(in) MyStruct arg[] {
    jclass objectClass = jenv->GetObjectClass(jarg1);
    jmethodID getCPtrMethod = jenv->GetStaticMethodID(objectClass, "getCPtr", "(LMyStructArray;)J");
    if (getCPtrMethod == NULL)
      return $null;
    jlong cptr = jenv->CallStaticLongMethod(objectClass, getCPtrMethod, jarg1);
    arg1 = (MyStruct *) cptr;
}

%include "demo.h"

Makefile

CC=g++
LD=$(CC)
JC=javac

DEPS=demo.h
OBJ=demo.o demo_wrap.o
LIB_OUT=libdemo.so
JAVA_HOME?=$(shell readlink -f /usr/bin/javac | sed "s:bin/javac::")
IFLAGS=-I$(JAVA_HOME)/include -I$(JAVA_HOME)/include/linux

JAVA_CLASSES=Demo DemoJNI MyStruct MyStructArray
JAVA_SRC=$(patsubst %,%.java,$(JAVA_CLASSES))
JAVA_OUT=$(patsubst %,%.class,$(JAVA_CLASSES))

SWIG_GENERATED=$(JAVA_SRC) demo_wrap.cxx

all: $(LIB_OUT) java

demo.o: demo.cpp
demo_wrap.o: demo_wrap.cxx
$(OBJ):
	$(CC) -c -o $@ $^ $(IFLAGS) -fPIC

$(LIB_OUT): $(OBJ)
	$(LD) -o $(LIB_OUT) $(OBJ) -shared

java: $(JAVA_OUT)
$(JAVA_OUT): %.class : %.java
	$(JC) $^

swig: $(SWIG_GENERATED)
$(SWIG_GENERATED): demo.i $(DEPS)
	swig -c++ -java demo.i

clean:
	rm -rf *.so *.o *.java *wrap.cxx *.class

.PHONY: all clean swig java

run.sh

#!/bin/bash

java -Djava.library.path=. Demo

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