@Override
    public long count() {
        if (count == null) {
            final InputStream data = getInputStream();
            final InputStream boundaryIndex = getChildInputStream(InternalStreamTypeNames.BOUNDARY_INDEX);
            count = new RASegmentInputStream(data, boundaryIndex).count();
        }
        return count;
    }
Creates a new file system stream source.

@return A new file system source.
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/FsSource.java