@SuppressWarnings("NullableProblems")
    @Override
    public void write(final byte[] b, final int off, final int len) throws IOException {
        dataOutputStream.write(b, off, len);
        position += len;
    }
Writes <code>len</code> bytes from the specified byte array starting at
offset <code>off</code> to the data output stream.

@param b   the data.
@param off the start offset in the data.
@param len the number of bytes to write.
@throws IOException if an I/O error occurs. In particular, an
                    <code>IOException</code> is thrown if the output stream is
                    closed.
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/RASegmentOutputStream.java