private void storeBTreeVars(boolean toDisk) throws IOException {
    final IntToIntBtree tree = myBTree;
    if (tree != null) {
      final int BTREE_DATA_START = DATA_START + 36;
      tree.persistVars(new IntToIntBtree.BtreeDataStorage() {
        @Override
        public int persistInt(int offset, int value, boolean toDisk) throws IOException {
          return store(BTREE_DATA_START + offset, value, toDisk);
        }
      }, toDisk);
    }
  }
private void storeBTreeVars(boolean toDisk)