@SuppressWarnings({"EI_EXPOSE_REP", "EI_EXPOSE_REP2"})
        public byte[] getBuffer() {
            return buffer;
        }
An output stream buffer that tries to use a given buffer first and once that
is not big enough it delegates all calls to a real ByteArrayOutputStream.
<p>
It also allows access to the buffer and pos without a copy of the array.
stroom-util/src/main/java/stroom/util/io/InitialByteArrayOutputStream.java