@Override
    public byte[] getBuffer() {
        if (offset == buffer.length) {
            return this.buffer;
        } else {
            return copyBuffer();
        }
    }
Be careful that if internal buffer's length is as same as offset,
then just return internal buffer without copying memory for improving performance.
@return
commons-buffer/src/main/java/com/navercorp/pinpoint/common/buffer/FixedBuffer.java