[Swig-user] Java directors with byte arrays in swig callback example

[Stefan R. <sw...@mi...>]

Hi there,

I have a callback function in C++ to fill a byte array passed via pointer and size (I need some audio samples). Now I want to be able to provide this data from a callback in Java.

I realize that callbacks are handled via directors in SWIG and that I can use predefined typemaps to combine a (char*, int) in C to a byte[] in Java. Both techniques work when used on their own, but for the life of me, I can't combine them. I tried to modify the Examples/java/callback/ example in swig by simply modifying the signature of Callback::run() to Callback::run(char* buffer, int size), which compiles just fine and will call the java code in JavaCallback::run(String buffer, int size), but as soon as I force (char* buffer, int size) into a jbyteArray by adding

%apply (char *STRING, size_t LENGTH) { (char* buffer, int size) };

to example.i, SWIG will complain about "example.h:6: Warning 810: No jni typemap defined for int for use in Callback::run (skipping director method)". I tried to get a grip on the problem by running swig on a clean example with -debug-tmused and -debug-tmsearch but had no luck tracking it down.

I modified the files Examples/java/callback/ as follows:
in example.h

Callback::run(char* buffer, int size) { std::cout << "Callback::run()" << std::endl; }

Caller::call() { 
	if (_callback) {
		char* foo = (char*)malloc(1024);
		memset(foo, 47, 1024);
		foo[1023] = 0;
		_callback->run(foo, 1024); 
		free(foo);
	}
}

in runme.java

// without the apply in example.i this works
@Override
JavaCallback::run(String buffer, int size) {
  System.out.println("JavaCallback.run() " + size + " " + buffer);
}

// with the apply, this ought to work
@Override
JavaCallback::run(byte[] buffer) {
  System.out.println("JavaCallback.run() " + " " + buffer.size);
}

Please, could someone provide me with a set of typemaps to use a java director class to modify a byte array?

Best regards
Stefan