A SWIG interface file to map Matrix's olm C interface to Java

Olm.i

/*
 * Call swig:         "swig -java -c++ -package org.chatsecure.olmwrapper -outdir ~/Code/olmJava olm.i"
 */

%module olmwrapper
%{
/* Put headers and other declarations to include in the wrapper code here */
#include "olm.hh"
};

typedef unsigned int size_t; // Technically we'd want int on 32bit, long on 64 bit?
%}

typedef unsigned int size_t;  // Technically we'd want int on 32bit, long on 64 bit?

%include "olm.hh"
%include "typemaps.i"  // Standard Java <--> C Type mappings

/*
 * Map void* to Java's Direct ByteBuffer. We need to allocate mutable memory in order to construct
 * the Olm structs like Account, Session etc. The safest way to do this seems to be Java's Direct ByteBuffer.
 * The Olm methods that take allocated memory use a void * type.
 */
%typemap(jni)    (void * BYTE) "jobject"
%typemap(jtype)  (void * BYTE) "java.nio.ByteBuffer"
%typemap(jstype) (void * BYTE) "java.nio.ByteBuffer"
%typemap(javain) (void * BYTE) "$javainput"

%typemap(in) (void * BYTE) {
  if (!$input) {
    SWIG_JavaThrowException(jenv, SWIG_JavaNullPointerException, "Java data is null!");
    return $null;
  }

  $1 = ($1_ltype) JCALL1(GetDirectBufferAddress, jenv, $input);
}

/*
 * Define when to apply the new typemap: if SWIG sees a method signature (also
 * partial signature) it applies the patterns. "BYTE" is the placeholder for
 * the real parameter name.
 */
%apply (void * BYTE)   { (void * memory) };

Currently the ByteBuffer <--> (void *) input typemap isn't working. An example function signature I'm trying to target from Olm.hh is OlmSession * olm_session(void * memory);