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copied!<p>The simplest solution is to <a href="https://stackoverflow.com/a/10495755/168175">use SWIG's <code><carrays.i></code> to make a type that wraps an array</a> of <code>float</code> and an array of <code>int</code> and any other types you care about. These can be converted to <code>SWIGTYPE_p_float</code> etc. trivially using the <code>cast()</code> member function. The problem is that this can't automatically be converted to a <code>SWIGTYPE_p_void</code> from within Java. You could in theory call:</p> <pre><code>new SWIGTYPE_p_void(FloatArray.getCPtr(myfloatarr)); </code></pre> <p>but for various reasons (not least it's cumbersome) that's less than ideal. (It also has issues with memory ownership and garbage collection).</p> <p>So instead I defined an interface:</p> <pre><code>public interface VoidPtr { public long asVoidPtr(); } </code></pre> <p>That we can make the wrapped version of your library take as input and the array classes <code>FloatArray</code>, <code>IntArray</code> etc. implement for us.</p> <p>This ends up with the module file:</p> <pre><code>%module test %include <carrays.i> %typemap(javainterfaces) FloatArray "VoidPtr" %typemap(javainterfaces) IntArray "VoidPtr" %typemap(javacode) FloatArray %{ public long asVoidPtr() { return getCPtr(this); } %} %typemap(javacode) IntArray %{ public long asVoidPtr() { return getCPtr(this); } %} %array_class(float, FloatArray); %array_class(int, IntArray); %typemap(jstype) void *arr "VoidPtr" %typemap(javain) void *arr "$javainput.asVoidPtr()" void foo(void *arr); </code></pre> <p>Which modifies <code>void *arr</code> to be treated as our <code>VoidPtr</code> type and automatically calls the <code>asVoidPtr()</code> method. You could use <a href="http://www.swig.org/Doc1.3/Typemaps.html#Typemaps_nn13" rel="nofollow noreferrer">typemap copying</a> or macros to make this less repetitive. (Note, there's a possible issue with <a href="http://www.swig.org/Doc1.3/Java.html#java_pgcpp" rel="nofollow noreferrer">premature garbage collection</a> that might need to be addressed here depending on how you planned to use this)</p> <p>This allows us to write code like:</p> <pre><code>public class run { public static void main(String[] argv) { FloatArray arr = new FloatArray(100); test.foo(arr); } } </code></pre> <p>I think this is the easiest, cleanest solution. There are several other ways you could solve this though:</p> <ol> <li><p>It's also possible to write some code that would take an actual Java array rather than just the SWIG <code>array_class</code> and implement this interface by calling a JNI function to obtain the underlying pointer. You'd have to write a version of this for every primitive type though, just like the above.</p> <p>An interface file could then look something like:</p> <pre><code>%module test %{ void foo(void *arr); %} %typemap(in,numinputs=0) JNIEnv *env "$1 = jenv;" %rename(foo) fooFloat; %rename(foo) fooInt; %inline %{ void fooFloat(JNIEnv *env, jfloatArray arr) { jboolean isCopy; foo((*env)->GetFloatArrayElements(env, arr, &isCopy)); // Release after call with desired semantics } void fooInt(JNIEnv *env, jintArray arr) { jboolean isCopy; foo((*env)->GetIntArrayElements(env, arr, &isCopy)); // Release after call } %} void foo(void *arr); </code></pre> <p>Which then gives you overloads of <code>foo</code> which take <code>float[]</code> and <code>int[]</code> as well as <code>SWIGTYPE_p_void</code>.</p></li> <li><p>You could use a trick with a union:</p> <pre><code>%inline %{ union Bodge { void *v; float *f; int *i; }; %} </code></pre> <p>although this is considered bad form, it does generate you a Java interface that can be used to convert from <code>SWIGTYPE_p_int</code> to <code>SWIGTYPE_p_void</code>.</p></li> <li><p>I think it's possible to make <code>FloatArray</code> inherit from <code>SWIGTYPE_p_void</code>, something like the following compiled but untested code:</p> <pre><code>%module test %include <carrays.i> %typemap(javabase) FloatArray "SWIGTYPE_p_void" %typemap(javabody) FloatArray %{ private long swigCPtr; // Minor bodge to work around private variable in parent private boolean swigCMemOwn; public $javaclassname(long cPtr, boolean cMemoryOwn) { super(cPtr, cMemoryOwn); this.swigCPtr = SWIGTYPE_p_void.getCPtr(this); swigCMemOwn = cMemoryOwn; } %} %array_class(float, FloatArray); void foo(void *arr); </code></pre> <p>This duplicates the pointer on the Java side, but nothing changes that (currently) in either the void pointer or array classes so that's not as big a problem as it first seems. (You could also make it protected in the base class with an alternative typemap I think, or use a modified version of <code>carrays.i</code> that gets <code>swigCPtr</code> via the <code>getCPtr</code> function instead)</p></li> </ol>

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