void putNextEntry() throws IOException {
        checkNotClosed();
        if (!currentEntryClosed) {
            throw new IOException("Current nested stream is not closed");
        }
        segmentCount++;
        if (segmentCount >= 2) {
            // Start writing segments on the 2nd stream to be added
            segmentOutputStream.addSegment();
        }
        currentEntryClosed = false;
    }
Class used to write multiple streams to a single stream separated by segments
by a segment marker (boundary).
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/RANestedOutputStream.java