boolean hasRemaining() {
    return remaining > 0;
  }
Expensive. Makes a new buffer to hold a copy of what is in contained ByteBuffers. This call
drains this instance; it cannot be used subsequent to the call.
@return A new byte buffer with the content of all contained ByteBuffers.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/BufferChain.java