@Override
    public int read() throws IOException {
        int rtn = super.read();
        if (rtn != -1) {
            // did we read a byte?
            streamPosition++;
        }
        return rtn;
    }
Point at a new input stream and reset our markers. Used to avoid
allocating new buffers.

@param newIn new stream to read
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/BlockBufferedInputStream.java