Retrieve ByteBuffer object from Bytes<ByteBuffer>

Question

I have been trying to retrieve ByteBuffer (Direct) object reference from Bytes object. Following is the code:

TestMessageWire testMessageWire = new TestMessageWire();
testMessageWire.data('H');
testMessageWire.setIntData(100);

//Below does not give ByteBuffer with correct position & offset
Bytes<ByteBuffer> bytes = Bytes.elasticByteBuffer(10);
Wire wire = new RawWire(bytes);
testMessageWire.writeMarshallable(wire);
ByteBuffer byteBuffer = ByteBuffer.wrap(bytes.toByteArray());

//Another approach, but still does not populate "byteBuffer" object correctly.
ByteBuffer byteBuffer = ByteBuffer.allocateDirect(6);
Bytes<?> bytes = Bytes.wrapForWrite(byteBuffer);
Wire wire = new RawWire(bytes);
testMessageWire.writeMarshallable(wire);

I want to avoid multiple allocation while creating ByteBuffer object. Hence, want to reuse same Bitebuffer wraped by Bytes. How can I achieve this?

Answer 1

You can create a Bytes which wraps a ByteBuffer. This avoids redundant copies.

Bytes<ByteBuffer> bytes = Bytes.elasticByteBuffer();
ByteBuffer bb = bytes.underlyingObject();

Never the less you have to ensure the the ByteBuffer's position and limit is maintained as Bytes has a separate read/write position & limit.

e.g. after writing you might want to do the following so you can read from the ByteBuffer what was written to the Bytes.

bb.position((int) bytes.readPosition());
bb.limit((int) bytes.readLimit());