Handle function pointer in a structure in SWIG java

Question

I am very new to this question answer forum and same in the swig. I am not sure if I am following correct steps to generate wrappers for java and C using swig interface file.

my header example.h file looks like below

#ifndef INCLUDE_ARTIK_WEBSOCKET_H_
#define INCLUDE_ARTIK_WEBSOCKET_H_

#ifdef __cplusplus
extern "C" {
#endif
typedef enum {
    SAMPLE_WEBSOCKET_CLOSED = 1,
    SAMPLE_WEBSOCKET_CONNECTED,
    SAMPLE_WEBSOCKET_HANDSHAKE_ERROR
} sample_websocket_connection_state;

typedef void *sample_websocket_handle;

typedef struct {
    char *uri;
void *private_data;
} sample_websocket_config;


typedef struct {
    void(*websocket_request) (
                sample_websocket_handle * handle,
                sample_websocket_config * config
                );

} sample_websocket_module;

extern const sample_websocket_module websocket_module;

#ifdef __cplusplus
}
#endif
#endif

And my interface file test_app.i looks like below:

%module  test_app 
%{
#include "example.h"
%}

%include "example.h"

And when I generate wrappers using command swig -java test_app.i which generates following files

sample_websocket_config.java
sample_websocket_module.java
SWIGTYPE_p_void.java
test_app.java
test_app_wrap.c
sample_websocket_connection_state.java
SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void.java

test_appJNI.java

typedef struct {
void(*websocket_request) (
            sample_websocket_handle * handle,
            sample_websocket_config * config
            );

} sample_websocket_module;

above code generates sample_websocket_module.java class which looks like below

public class sample_websocket_module {
  private transient long swigCPtr;
  protected transient boolean swigCMemOwn;

  protected sample_websocket_module(long cPtr, boolean cMemoryOwn) {
    swigCMemOwn = cMemoryOwn;
    swigCPtr = cPtr;
  }

  protected static long getCPtr(sample_websocket_module obj) {
    return (obj == null) ? 0 : obj.swigCPtr;
  }

  protected void finalize() {
    delete();
  }

  public synchronized void delete() {
    if (swigCPtr != 0) {
      if (swigCMemOwn) {
        swigCMemOwn = false;
        test_appJNI.delete_sample_websocket_module(swigCPtr);
      }
      swigCPtr = 0;
    }
  }

  public void setWebsocket_request(SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void value) {
    test_appJNI.sample_websocket_module_websocket_request_set(swigCPtr, this, SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void.getCPtr(value));
  }

  public SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void getWebsocket_request() {
    long cPtr = test_appJNI.sample_websocket_module_websocket_request_get(swigCPtr, this);
    return (cPtr == 0) ? null : new SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void(cPtr, false);
  }

  public sample_websocket_module() {
    this(test_appJNI.new_sample_websocket_module(), true);
  }

}

So I am not sure how to provide arguments to this function as it has merged both the arguments and created a separate class SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void.java.

    public class SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void {
  private transient long swigCPtr;

  protected SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void(long cPtr, @SuppressWarnings("unused") boolean futureUse) {
    swigCPtr = cPtr;
  }

  protected SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void() {
    swigCPtr = 0;
  }

  protected static long getCPtr(SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void obj) {
    return (obj == null) ? 0 : obj.swigCPtr;
  }
}

and this is the function which is using above class. So how can I provide values to this function.

public void setWebsocket_request(SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void value) {
    test_appJNI.sample_websocket_module_websocket_request_set(swigCPtr, this, SWIGTYPE_p_f_p_p_void_p_sample_websocket_config__void.getCPtr(value));
  }

Thanks in advance.

WillShackleford · Accepted Answer · 2017-09-29 19:30:20Z

1

I think you will need to add some C code that will do the pointer dereference that you could then call. You can add a function in the interface file that will get pasted into the test_app_wrap.c.

So test_app.i becomes:

%module  test_app 
%{
#include "example.h"

    void callwebsocketreq(sample_websocket_module *mod, 
               sample_websocket_handle * handle,
                sample_websocket_config * config) {
        (*mod->websocket_request)(handle,config);
    }

%}

%include "example.h"
void callwebsocketreq(sample_websocket_module *mod, 
               sample_websocket_handle * handle,
                sample_websocket_config * config);

Now there will be a callwebsocketreq method in the test_app.java that you can call to pass in those arguments.

answered Sep 29, 2017 at 19:30

WillShackleford

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