Java NIO ByteOrdering with JNA and native C code on OSX

Say you want to interact with a C program that modifies a NIO Buffer allocated from Java. Java NIO provides a way to help with this but the default ByteOrder on NIO ByteBuffers is BigEndian. By allocating the buffer with the same ordering using ByteOrder.nativeOrder(), a mismatch will not occur between native and JVM code.

Example Java class:

...

public class JNAByteOrderExample {

public static void main(String[] args)

{

FloatBuffer fb = ByteBuffer.allocateDirect(10*4).order(ByteOrder.nativeOrder()).asFloatBuffer();

for(int index =0; index<...)

{

System.out.print( " " + data.get(index) );

}

static

{

Native.register("/libdemo.dylib");

}

public static native int demo(FloatBuffer fb);

}

Example C code:

int demo( float * data )

{

int i = 0;

for( i = 0; i ...)

{

data[i]=777;

}

return 0;

}

Compile the C file with:

gcc -bundle -o libdemo.dylib -dynamic demo.c