jni not support types as void*, unsigned int*, … What to do?

Question

I have .so (shared library) written in C++, lets call it functionality.so in which I implement different functions, here is list of some fu

Answer 1

What you want to do is this: For the void* function, use direct byte buffers. On the Java side:

native long initialize(java.nio.ByteBuffer userData);

When you call the method, make sure to allocate a direct ByteBuffer (see java.nio.ByteBuffer, and JNI nio usage):

ByteBuffer myData = ByteBuffer.allocateDirect(size);
long res = initialize(myData);

On the C side, you do this:

unsigned long res = Initialize(env->GetDirectBufferAddress(env, buffer));
return (jlong)res;

You read and write from the buffer on the Java side with the ByteBuffer methods.

You can also allocate the byte buffer on the C side with env->NewDirectByteBuffer(env, ptr, size.

Now, for the second function, I assume the unsigned long* argument is used to return a result. You can use the same approach (direct ByteBuffers), but I would recommend a different one that wouldn't entail allocating a buffer for such a small value.

On the Java side:

native long deviceOpen(long id, long[] device);

On the C side:

unsigned long c_device;
unsigned long res = DeviceOpen((unsigned long)j_id, &c_device);
env->SetLongArrayRegion(env, j_device, 0, 1, &c_device);
return (jlong)res;

Then you call the method from Java:

long[] deviceOut = new long[1];
long res = deviceOpen(id, deviceOut);
long device = deviceOut[0];

For more information on array access from JNI see JNI array operations