[Swig-user] how can I return an array who's size is not static?

[Valient G. <va...@gm...>]

I'm creating a Java wrapper using Swig 1.3.29 and having some trouble
with arrays.

I have a struct which contains a byte array, the size of which is not
known at compile time.  I would like the regular get accessor to
return a byte[].    I've reduced the code to a simple example:

test.h:
typedef const char * buffer_p;
struct Test
{
#ifdef SWIG
    %immutable;
#endif
    buffer_p buf;
    int bufSize;
};

test.i:
%module TestWrapper
%{
#include "test.h"
%}
%include "typemaps.i"
%include "arrays_java.i"

%apply signed char[] { buffer_p }
%include "test.h"

Then I run "swig -java test.i"

The problem here is that swig doesn't know the size of Test.buf.  It
produces JNI code which contains the following in the buf_get method:

jresult = SWIG_JavaArrayOutSchar(jenv, result,
FillMeInAsSizeCannotBeDeterminedAutomatically);

How can I tell SWIG that the size of Test.buf is Test.bufSize?

I figured my options would go something like:
1. replace the JNI code for buf_get.
   I tried to use %native to replace the JNI code for Test_buf_get ,
but then I get errors from swig saying that Test_buf_get is defined
more then once.
2. somehow tell SWIG what the size is
   I tried adding "%apply signed char [bufSize] { buf }" before the
buf definition, but then I get an error message "test.h:8:
Warning(453): Can't apply (signed char [Test::bufSize]). No typemaps
are defined.
"
3. post-process the wrapper function to fill in the FillMeIn...
vars... Possible but ugly.

Any ideas?

TIA,
Valient