Java HotSpot Virtual Machine

In Java when I am calling the getBytes(bytes) I do not know the size of the byte array. Only in the C++ code I will know how long the Byte Array is going to be.

In C++ I just want to copy "cbytes" into "jbytes" such that I will be able to make use of it in Java.

Java Code:
----------------
private static native int getBytes(byte[] bytes);
.
.
byte[] bytes = null;
int status = getBytes(bytes)
..
..
C++ Code
---------------

JNIEXPORT jint JNICALL Java_getBytes
(JNIEnv *, jclass, jbyteArray jbytes)
{

char * cbytes = getCBytes();
//

return 0;

}

Could some one let me know how this can be achieved.

Thanks