Using GetDirectBufferAddress from JNI

Question

I am trying to understand how to use GetDirectBufferAddress from the JNI layer. To understand I\'ve build a very simple example:

Answer 1

What I missed from the documentation is that by default java.nio.ByteBuffer is actually using BIG_ENDIAN byte order. Which explains the behavior I was seeing on my LITTLE_ENDIAN system. See ref here.

My code now reads as:

image_info_bb = java.nio.ByteBuffer.allocateDirect( 5 * 4 );
image_info_bb.order( java.nio.ByteOrder.LITTLE_ENDIAN );

It appears that by default it is always BIG_ENDIAN, and no effort has been made so far to provide an API for LITTLE_ENDIAN, as explained in the bug report here (JDK-5043362 : (bf) NewDirectByteBuffer always has order ByteOrder.BIG_ENDIAN).

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Documentation has been updated recently to reflect that:

• JDK-8225152 : Release Note: JNI NewDirectByteBuffer Creates Direct Buffer That Is java.nio.ByteOrder.BIG_ENDIAN