IndexRootContainer(IndexItem root,
    IndexManager im,
    DataManager dfm) throws IOException 
{
        this.root = root;
        this.indexManager = im;
        this.dataManager = dfm;
        long nextItem = root.getNextItem();
        while (nextItem != Item.POSITION_NOT_SET) {
            StoreEntry item = indexManager.getIndex(nextItem);
            StoreLocation data = item.getKeyDataItem();
            Object key = dataManager.readItem(ROOT_MARSHALLER, data);
            map.put(key, item);
            list.add(item);
            nextItem = item.getNextItem();
            dataManager.addInterestInFile(item.getKeyFile());
        }
}

 IndexItem addRoot(IndexManager containerIndexManager,
    ContainerId key) throws IOException 
{
        if (map.containsKey(key)) {
            removeRoot(containerIndexManager, key);
        }
        StoreLocation data = dataManager.storeDataItem(ROOT_MARSHALLER, key);
        IndexItem newRoot = indexManager.createNewIndex();
        newRoot.setKeyData(data);
        IndexItem containerRoot = containerIndexManager.createNewIndex();
        containerIndexManager.storeIndex(containerRoot);
        newRoot.setValueOffset(containerRoot.getOffset());
        IndexItem last = list.isEmpty() ? null : (IndexItem)list.getLast();
        last = last == null ? root : last;
        long prev = last.getOffset();
        newRoot.setPreviousItem(prev);
        indexManager.storeIndex(newRoot);
        last.setNextItem(newRoot.getOffset());
        indexManager.storeIndex(last);
        map.put(key, newRoot);
        list.add(newRoot);
        return containerRoot;
}

 boolean doesRootExist(Object key) 
{
        return map.containsKey(key);
}

 Set<Object> getKeys() 
{
        return map.keySet();
}

 IndexItem getRoot(IndexManager containerIndexManager,
    ContainerId key) throws IOException 
{
        StoreEntry index = map.get(key);
        if (index != null) {
            return containerIndexManager.getIndex(index.getValueOffset());
        }
        return null;
}

  void removeRoot(IndexManager containerIndexManager,
    ContainerId key) throws IOException 
{
        StoreEntry oldRoot = map.remove(key);
        if (oldRoot != null) {
            dataManager.removeInterestInFile(oldRoot.getKeyFile());
            // get the container root
            IndexItem containerRoot = containerIndexManager.getIndex(oldRoot.getValueOffset());
            if (containerRoot != null) {
                containerIndexManager.freeIndex(containerRoot);
            }
            int index = list.indexOf(oldRoot);
            IndexItem prev = index  > 0 ? (IndexItem)list.get(index - 1) : root;
            prev = prev == null ? root : prev;
            IndexItem next = index <  (list.size() - 1) ? (IndexItem)list.get(index + 1) : null;
            if (next != null) {
                prev.setNextItem(next.getOffset());
                next.setPreviousItem(prev.getOffset());
                indexManager.updateIndexes(next);
            } else {
                prev.setNextItem(Item.POSITION_NOT_SET);
            }
            indexManager.updateIndexes(prev);
            list.remove(oldRoot);
            indexManager.freeIndex((IndexItem)oldRoot);
        }
}