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Maintaining state in SWIG Java director class

I want to access a Java graph library (Titan) from c++. Doing some research showed that JNI would get the job done. I wrote some JNI code, got it working, but it quickly became tedious, so I looked to an automated solution. I found SWIG, more specifically SWIG directors. I have no problem calling functions, however I have a problem of maintaining state going back and forth from Java and c++ using a SWIG director.
For my SWIG directors I wrote c++ interfaces exposing the functionality I wanted. Below is a sample:
GraphIfc.hpp:
struct GraphIfc {
virtual ~GraphIfc() {}
virtual VertexIfc * addVertex(const std::string& label) = 0;
};
VertexIfc.hpp:
struct VertexIfc {
virtual ~VertexIfc() {}
virtual EdgeIfc * addEdge(const std::string& label, VertexIfc * v) = 0;
};
EdgeIfc.hpp:
struct EdgeIfc {
virtual ~EdgeIfc() {}
};
Then I wrote the Java implementation:
JGraph.java:
import com.thinkaurelius.titan.core.TitanGraph;
public class JGraph extends GraphIfc {
private TitanGraph graph;
public JGraph(TitanGraph g) {
graph = g;
}
public VertexIfc addVertex(final String label) {
return new Vertex(graph.addVertex(label));
}
}
JVertex.java:
import com.thinkaurelius.titan.core.TitanVertex;
public class JVertex extends VertexIfc {
public TitanVertex vertex;
public JVertex(TitanVertex v) {
vertex = v;
}
public EdgeIfc addEdge(final String label, VertexIfc inV) {
Vertex v = (Vertex)inV;
return new Edge(vertex.addEdge(label, v.vertex));
}
}
JEdge.java:
import org.apache.tinkerpop.gremlin.structure.Edge;
public class JEdge extends EdgeIfc {
public Edge edge = null;
public JEdge(Edge e) {
edge = e;
}
}
And here's my SWIG file:
%module(directors="1") graph
%{
#include "graph.hpp"
#include "vertex.hpp"
#include "edge.hpp"
%}
%feature("director") GraphIfc;
%feature("director") VertexIfc;
%feature("director") EdgeIfc;
SWIG_DIRECTOR_OWNED(GraphIfc)
SWIG_DIRECTOR_OWNED(VertexIfc)
SWIG_DIRECTOR_OWNED(EdgeIfc)
%include "graph.hpp"
%include "vertex.hpp"
%include "edge.hpp"
%pragma(java) jniclasscode=%{
static {
try {
System.loadLibrary("graph");
} catch (UnsatisfiedLinkError e) {
System.err.println("Native code library graph failed to load.\n" + e);
System.exit(1);
}
}
%}
All of this produces:
Java proxy classes: GraphIfc, VertexIfc, EdgeIfc. These hold the c++ pointer as a long.
Intermediary JNI class in Java with functions
such as:
public static long SwigDirector_GraphIfc_addVertex(GraphIfc jself, String label) {
return VertexIfc.getCPtr(jself.addVertex(label));
}
public static long SwigDirector_VertexIfc_addEdge(VertexIfc jself, String label, long inVertex) {
return EdgeIfc.getCPtr(jself.addEdge(label, (inVertex == 0) ? null : new VertexIfc(inVertex, false)));
}
There are a two problems with these functions:
The VertexIfc being created by SwigDirector_VertexIfc_addEdge is not of type JVertex, thus my cast within addEdge will fail and throw an exception.
But more importantly, even if the type was a JVertex, the new JVertex would not contain the same value of TitanVertex as set by addVertex. Any state within the derived class (JVertex, JEdge, etc) is loss.

JNA 4.2.1 call dll method without params

i use jna 4.2.1
I have a method in the dll which returns a pointer to an object (C++)
basic_hash* getAlgorithmInstance( int algorithm )
basic_hash has the following methods (C++):
void reset ();
void partial (const byte* data, uint64 size);
void finalize (vector_byte& hash);
void hash (const byte* data, uint64 size, vector_byte& hash).
i have interface (java)
public interface HAL extends Library {
HAL INSTANCE = (HAL) Native.loadLibrary(
(Platform.isWindows() ? "HAL" : "libHAL"), HAL.class);
BasicHash getAlgorithmInstance(int i);
}
public static class BasicHash extends Structure {
public BasicHash() {}
public BasicHash(Pointer p) {
super(p);
read();
}
#Override
protected List getFieldOrder() {
return Arrays.asList(new String[] { "reset", "hash", "partial", "finalize" });
}
public interface Reset extends Callback { public void invoke();}
public Reset reset;
public interface Hash extends Callback {public void invoke(byte[] data, long size, byte[] hash);}
public Hash hash;
public interface Partial extends Callback {public void invoke(Pointer data, long size);}
public Partial partial;
public interface Finalize extends Callback {public void invoke(byte[] hash);}
public Finalize finalize;
}
and when I use the method without parameters in main()
HAL lib = HAL.INSTANCE;
BasicHash b = lib.getAlgorithmInstance(0);
b.reset.invoke();
I get an error:
Exception in thread "main" java.lang.Error: Invalid memory access
at com.sun.jna.Native.invokeVoid(Native Method)
at com.sun.jna.Function.invoke(Function.java:374)
at com.sun.jna.Function.invoke(Function.java:323)
at com.sun.jna.Function.invoke(Function.java:275)
at com.sun.jna.CallbackReference$NativeFunctionHandler.invoke(CallbackReference.java:646)
at com.sun.proxy.$Proxy1.invoke(Unknown Source)
at net.erver.ItServer.main(ItServer.java:79)
Why did I receive this error if the method resets the variables within the library? the method itself fulfills without problems (according to developers dll)
EDIT:
vector_byte has definition:
typedef unsigned char byte;
typedef std::vector< byte > vector_byte
and basic_hash has definition:
namespace HAL { namespace algorithms {
HAL_HASH_API enum class State : byte {
Normal,
Finished,
};
class HAL_HASH_API basic_hash
{
public:
virtual ~basic_hash() {}
virtual void reset() = 0;
virtual void partial( const byte*, uint64 ) = 0;
virtual void finalize( vector_byte& ) = 0;
virtual void hash( const byte*, uint64, vector_byte& ) = 0;
bool isFinished() {
return ( _state == State::Finished ? true : false );
}
protected:
State _state;
};
}
}

You need to use plain vanilla struct to pass data between JNA and your library. A C++ class (including a vector template) has a much different memory layout than does a simple C struct.

How do I use a more specific struct type in place of a more general one?

I am working on a windows device manager which will work with java.
I stick on trying to pass without error SetupDiSetClassInstallParams function. (I am trying disable an device.)
I am running exact same structure(necessary way) in C++ and I do not have any problem.
I am getting ERROR_INVALID_USER_BUFFER error. When I tried get this error in C++ I need to change SP_PROPCHANGE_PARAMS structs values with wrong ones.
My struct declerations:
public static class SP_CLASSINSTALL_HEADER extends Structure {
public static class ByReference extends SP_CLASSINSTALL_HEADER implements Structure.ByReference {
public ByReference() {
}
public ByReference(Pointer memory) {
super(memory);
}
}
public SP_CLASSINSTALL_HEADER() {
cbSize = size();
}
public SP_CLASSINSTALL_HEADER(Pointer memory) {
super(memory);
read();
}
public int cbSize;
public long InstallFunction; **/* <-- this should be int or else buffer size changes, dll cannot place variables on right places. */**
protected List getFieldOrder() {
return Arrays.asList(new String[] { "cbSize", "InstallFunction" });
}
}
public static class SP_PROPCHANGE_PARAMS extends Structure {
public static class ByReference extends SP_PROPCHANGE_PARAMS implements Structure.ByReference {
public ByReference() {
}
public ByReference(Pointer memory) {
super(memory);
}
}
public SP_PROPCHANGE_PARAMS() {
}
public SP_PROPCHANGE_PARAMS(Pointer memory) {
super(memory);
read();
}
public SP_CLASSINSTALL_HEADER ClassInstallHeader = new SP_CLASSINSTALL_HEADER();
public int StateChange;
public int Scope;
public int HwProfile;
protected List getFieldOrder() {
return Arrays.asList(new String[] { "ClassInstallHeader", "StateChange", "Scope", "HwProfile" });
}
}
My function decleration:
boolean SetupDiSetClassInstallParams(WinNT.HANDLE hDevInfo, Pointer deviceInfoData, Pointer classInstallHeader, int size);
How do I calling this function:
SP_PROPCHANGE_PARAMS spPropChangeParams = new SP_PROPCHANGE_PARAMS();
spPropChangeParams.ClassInstallHeader.InstallFunction = DISetupApi.DIF_PROPERTYCHANGE;
spPropChangeParams.Scope = DISetupApi.DICS_FLAG_GLOBAL;
spPropChangeParams.HwProfile = 0;
spPropChangeParams.StateChange = DISetupApi.DICS_DISABLE;
int spPropChangeParamsSize = spPropChangeParams.size();
SP_CLASSINSTALL_HEADER classInstallHeaderReference = new SP_CLASSINSTALL_HEADER(spPropChangeParams.getPointer());
setupApi.SetupDiSetClassInstallParams(hDevInfo, device.getSPDeviceInfoData().getPointer(), classInstallHeaderReference.getPointer(),
spPropChangeParamsSize);
How It works in c++:
SP_PROPCHANGE_PARAMS spPropChangeParams;
spPropChangeParams.ClassInstallHeader.cbSize = sizeof(SP_CLASSINSTALL_HEADER);
spPropChangeParams.ClassInstallHeader.InstallFunction = DIF_PROPERTYCHANGE;
spPropChangeParams.Scope = DICS_FLAG_GLOBAL;
spPropChangeParams.HwProfile = 0;
spPropChangeParams.StateChange = DICS_DISABLE;
SetupDiSetClassInstallParams(hDeviceInfo, &device.getDeviceInfoData(), (SP_CLASSINSTALL_HEADER*)&spPropChangeParams, sizeof(spPropChangeParams));
Actually I mixed and matched too many ways these structs and function I changed variable types of structs and parameter types of function at the end I could not get anything but error. I cannot find what is my mistake. Could you please help me solve this.
Thanks in advance!

When you're passing around a Structure, don't use Structure.getPointer() unless you have to. When you do that, JNA can't automatically synch the native and Java data, and it's error-prone to remember where to do that yourself. In your case, whatever is in the Java fields never gets copied to native memory in your call to setupApi.SetupDiSetClassInstallParams.
Change your function mapping to this:
boolean SetupDiSetClassInstallParams(WinNT.HANDLE hDevInfo, SP_DEVINFO_DATA deviceInfoData, SP_CLASSINSTALL_HEADER classInstallHeader, int size);
and change the invocation to this:
setupApi.SetupDiSetClassInstallParams(hDevInfo, device.getSPDeviceInfoData(), classInstallHeaderReference, spPropChangeParamsSize);
EDIT
If you stick to your original struct definition (where SP_CLASSINSTALL_HEADER is a field), you need to add a function mapping to the interface (extend the interface and create your own instance of the native library):
public interface MySetupApi extends SetupApi {
MySetupApi INSTANCE = (MySetupApi)Native.loadLibrary(MySetupApi.class, W32APIOptions.DEFAULT_OPTIONS);
boolean SetupDiSetClassInstallParams(WinNT.HANDLE hDevInfo, SP_DEVINFO_DATA deviceInfoData, SP_PROPCHANGE_PARAMS propChangeParams, int size);
}

Convert a C++ callback to Java

I have the following code in C++ (Cocos2d) :
typedef void (CCObject::*SEL_CallFunc)();
CCCallFunc * CCCallFunc::actionWithTarget(CCObject* pSelectorTarget,
SEL_CallFunc selector) {
CCCallFunc *pRet = new CCCallFunc();
if (pRet && pRet->initWithTarget(pSelectorTarget)) {
pRet->m_pCallFunc = selector;
pRet->autorelease();
return pRet;
}
CC_SAFE_DELETE(pRet);
return NULL;
}
When converting with swig to java I get the following :
public static CCCallFunc actionWithTarget(CCObject pSelectorTarget, SWIGTYPE_m_CCObject__f___void selector) {
long cPtr = cocos2dxMappingJNI.CCCallFunc_actionWithTarget(CCObject.getCPtr(pSelectorTarget), pSelectorTarget,
SWIGTYPE_m_CCObject__f___void.getCMemberPtr(selector));
return (cPtr == 0) ? null : new CCCallFunc(cPtr, false);
}
Where SWIGTYPE_m_CCObject__f___void is just a pointer I can't use.
How do I implement this in the SWIG interface ?
I've looked into this solution stackoverflow but couldn't implement it for my case.

I don't believe SWIG supports member function pointers in any meaningful way. However, it's possible to get it done with JavaCPP. Given this C++ code in a file named MemberFunction.h:
class MyClass {
public:
virtual ~MyClass() { }
};
typedef void (MyClass::*MyFunction)(const char *str);
void callback(MyClass* cls, MyFunction fct, const char *str) {
(cls->*fct)(str);
}
We can define and use the callback this way in Java:
import org.bytedeco.javacpp.*;
import org.bytedeco.javacpp.annotation.*;
#Platform(include="MemberFunction.h")
public class MemberFunction {
static { Loader.load(); }
public static abstract class MyClass extends Pointer {
public MyClass() { allocate(); }
private native void allocate();
#Virtual public abstract void myCallback(String str);
#Virtual #MemberGetter #Name("myCallback")
public static native MyFunction getMyCallback();
}
#Namespace("MyClass")
public static class MyFunction extends FunctionPointer {
public native void call(MyClass cls, String str);
}
public static native void callback(MyClass cls, MyFunction fct, String str);
public static void main(String[] args) {
MyClass cls = new MyClass() {
public void myCallback(String str) {
System.out.println(str);
}
};
MyFunction fct = MyClass.getMyCallback();
callback(cls, fct, "Hello World");
}
}
Which builds fine and outputs the expected result:
$ javac -cp javacpp.jar MemberFunction.java
$ java -jar javacpp.jar MemberFunction
$ java -cp javacpp.jar MemberFunction
Hello World

You probably want to look at a typemap for "SEL_CallFunc selector". The typemap squirrels the original language callback, which is called via a tramploline function. There are python examples here and here. You'll find various similar questions for java on SO.

JNA getFieldOrder() results in names not matching in HashSet() comparison (JNA's Structure.java, line 925)

Running into a maddening blocking error:
Exception in thread "main" java.lang.Error: Structure.getFieldOrder() on class com.luke.generator.GeneratorEngine$VERSION_INFO returns names ([BuildString, ProtocolMajorVer, ProtocolMinorVer]) which do not match declared field names ([BiuldString, ProtocolMajorVer, ProtocolMinorVer])
at com.sun.jna.Structure.getFields(Structure.java:925)
at com.sun.jna.Structure.deriveLayout(Structure.java:1058)
at com.sun.jna.Structure.calculateSize(Structure.java:982)
at com.sun.jna.Structure.calculateSize(Structure.java:949)
at com.sun.jna.Structure.allocateMemory(Structure.java:375)
at com.sun.jna.Structure.<init>(Structure.java:184)
at com.sun.jna.Structure.<init>(Structure.java:172)
at com.sun.jna.Structure.<init>(Structure.java:159)
at com.sun.jna.Structure.<init>(Structure.java:151)
at com.luke.generator.GeneratorEngine$.<init>(GeneratorEngine.java:108)
at com.luke.generator.connectionVersion(GeneratorEngine.java:297)
at com.luke.generator.Main.main(Main.java:161)
Platform: Intel, Windows 8
JRE 1.7, 32-bit (x86)
Eclipse Kepler, Default encoding UTF-8
jna-4.1.0.jar
32-bit CPP DLL - I can confirm that I am loading the library and calling functions that do not include parameters. I also tried passing WStrings and Strings, but that did not address the issue.
Source:
CPP struct:
typedef struct {
UINT32 ProtocolMajorVer;
UINT32 ProtocolMinorVer;
UI_STRING BuildString; // Build version for the application.
} VERSION_INFO;
CPP Function
DLL_EXPORTS RETURN_TYPES ConnectionVersion (VERSION_INFO &Version) {<body omitted>}
Java code:
//Interface definition
public interface UiApi extends StdCallLibrary {
UiApi INSTANCE = (UiApi) Native.loadLibrary(UiApiPath,UiApi.class);
final String PROTOCOLMAJORVERSION = new String("ProtocolMajorVer");
final String PROTOCOLMINORVERSION = new String("ProtocolMinorVer");
final String BUILDSTRING = new String("BuildString");
public static class VERSION_INFO extends Structure {
public static class ByReference extends VERSION_INFO implements Structure.ByReference {}
public static class ByValue extends VERSION_INFO implements Structure.ByValue {}
public int ProtocolMajorVer;
public int ProtocolMinorVer;
public byte[] BiuldString;
protected List getFieldOrder() {
return Arrays.asList(new String[] { "ProtocolMajorVer","ProtocolMinorVer","BuildString" });
}
}
//Connection
public int Connect(byte[] strServerName);
public int Disconnect();
public int CloseProject();
public int ConnectionVersion(VERSION_INFO result);
public int ConnectionVersion(VERSION_INFO.ByReference result);
public int ConnectionVersion(VERSION_INFO.ByValue result);
}
//Engine.connectionVersion() method
public static int connectionVersion() {
int nReturn = 0;
String str = new String("This is my build version\n");
UiApi uiapilib;
uiapilib = UiApi.INSTANCE;
try {
UiApi.VERSION_INFO.ByReference result = new UiApi.VERSION_INFO.ByReference();
result.ProtocolMajorVer = 0;
result.ProtocolMinorVer = 0;
result.BiuldString = str.getBytes();
nReturn = uiapilib.ConnectionVersion(result);
}
catch (Exception e) {
System.out.println("Error=" + e.getLocalizedMessage());
}
return nReturn;
}
//This is the code in main that results in exception
private static Engine engine;
engine = new GeneratorEngine();
engine.connectionVersion();
I must be missing something basic. Is there something in Eclipse that could possibly be causing the HashSet name comparisons in JNA's Structure.java (line 925) that would result in names not matching? From the exception thrown, these definitions look identical.
Thanks for any tips, guidance, fresh perspectives you can offer.

Check your spelling - the field is called BiuldString not BuildString, you have the i and u reversed.