[Swig-user] java typemaps to map a C++ container class to a Java container class

[Michael P. <puj...@la...>]

Hi

I'm binding a C++ lib to Java and to make the bindings more Java 
friendly, I want to map some C++ container classes
to corresponding idiomatic Java container classes. (a bit like 
std::string <=> Java.lang.String mapping, but for custom classes)

Here's the function for which I want to generate wrappers:

void dispatch_refresh(const pfc::list_base_const_t<metadb_handle_ptr> & 
p_list);


I want to map "const pfc::list_base_const_t<metadb_handle_ptr> &"  to 
Java type "java.util.Vector<metadb_handle>",  so I wrote this interface file
(note that list_t is a subclass of pure abstract class list_base_const_t)

/////////////////////////////////////////////////////////////

%module test
%{
/* Includes the header in the wrapper code */

/* convert Vector<metadb_handle> to pfc::list_t<metadb_handle_ptr> */
static pfc::list_t<metadb_handle_ptr> * metadb_vector_to_list(JNIEnv 
*jenv, jobject vector) {

    jclass vector_class = jenv->FindClass("java/util/Vector");
    jmethodID vector_get_method = jenv->GetMethodID(vector_class, "get", 
"(I)Ljava/lang/Object;");
    jmethodID vector_size_method = jenv->GetMethodID(vector_class, 
"size", "()I");

    jclass metadb_handle_class = jenv->FindClass("metadb_handle");
    jfieldID metadb_handle_cptr_field = 
jenv->GetFieldID(metadb_handle_class, "swigCPtr", "J");

    int size = jenv->CallIntMethod(vector, vector_size_method);

    pfc::list_t<metadb_handle_ptr> *list = new 
pfc::list_t<metadb_handle_ptr>();

    int i;
    for(i = 0 ; i < size ; i++) {
        jobject elem = jenv->CallObjectMethod(vector, vector_get_method, i);
        metadb_handle_ptr item = metadb_handle_ptr((metadb_handle 
*)jenv->GetLongField(elem, metadb_handle_cptr_field));
        list->add_item(item);
    }

    return list;
}

void dispatch_refresh(const pfc::list_base_const_t<metadb_handle_ptr> & 
p_list) {
}


%}

%typemap(jni) const pfc::list_base_const_t<metadb_handle_ptr> & "jobject"
%typemap(jtype) const pfc::list_base_const_t<metadb_handle_ptr> & "Vector"
%typemap(jstype) const pfc::list_base_const_t<metadb_handle_ptr> & "Vector"

%typemap(in) const pfc::list_base_const_t<metadb_handle_ptr> &
%{ if(!$input) {
     SWIG_JavaThrowException(jenv, SWIG_JavaNullPointerException, "null");
     return $null;
   }
   $1 = metadb_vector_to_list(jenv, $input);
 %}
  
  

%typemap(javain) const pfc::list_base_const_t<metadb_handle_ptr> & 
"$javainput"

%typemap(javaout) const pfc::list_base_const_t<metadb_handle_ptr> & {
    return $jnicall;
}

%typemap(throws) const pfc::list_base_const_t<metadb_handle_ptr> &
%{ SWIG_JavaThrowException(jenv, SWIG_JavaRuntimeException, "yop");
   return $null; %}



void dispatch_refresh(const pfc::list_base_const_t<metadb_handle_ptr> & 
p_list);

/////////////////////////////////////////////////////////////

I case you wonder were the vector arg of metadb_vector_to_list() comes 
from,
I have a reciprocal function of metadb_vector_to_list() that is not call 
through SWIG
but using JNI Invocation API and instantiating Java SWIG proxy classes 
from C++ (had to
make the constructor taking in argument object's pointer public for this 
to work).

The interface file  generates the following dispatch_refresh wrapper 
code, which compiles just fine:


SWIGEXPORT void JNICALL Java_testJNI_dispatch_1refresh(JNIEnv *jenv, 
jclass jcls, jobject jarg1) {
  pfc::list_base_const_t<metadb_handle_ptr > *arg1 = 0 ;
 
  (void)jenv;
  (void)jcls;
  if(!jarg1) {
    SWIG_JavaThrowException(jenv, SWIG_JavaNullPointerException, "null");
    return ;
  }
  /*
     const char *arg1_pstr = (const char 
*)jenv->GetStringUTFChars(jarg1, 0);
     if (!arg1_pstr) return ;
     std::string arg1_str(arg1_pstr);
     arg1 = &arg1_str;
     jenv->ReleaseStringUTFChars(jarg1, arg1_pstr);
     */
  arg1 = metadb_vector_to_list(jenv, jarg1);
 
  dispatch_refresh((pfc::list_base_const_t<metadb_handle_ptr > const 
&)*arg1);
}


The problem is that metadb_vector_to_list() allocates a list_t object 
that should be freed after the call to dispatch_refresh() using "delete 
arg1;".

To solve it:

- is there a way to insert arbitrary code after dispatch_refresh(), in 
that case to free arg1
- is there a way to have arg1 not a pointer ? that way if the original 
func is defined as

void dispatch_refresh(const pfc::list_t<metadb_handle_ptr> & p_list);

and metadb_vector_to_list() return a list_t instead of a lis_t *, the 
generated could look like:

SWIGEXPORT void JNICALL Java_testJNI_dispatch_1refresh(JNIEnv *jenv, 
jclass jcls, jobject jarg1) {
  pfc::list_t<metadb_handle_ptr > arg1;
 
  (void)jenv;
  (void)jcls;
  if(!jarg1) {
    SWIG_JavaThrowException(jenv, SWIG_JavaNullPointerException, "null");
    return ;
  }
  arg1 = metadb_vector_to_list(jenv, jarg1);
 
  dispatch_refresh(arg1);
}