public String blockTypeToString(){
    String s = "unrecognized";
    switch( getBlockType() ){
    case BLOCK_TYPE_UNKNOWN: s = "unknown"; break;
    case BLOCK_TYPE_CATALOG: s = "DB catalog"; break;
    case BLOCK_TYPE_BPT_HEADER: s = "B+Tree header"; break;
    case BLOCK_TYPE_BPT_INTERNAL: s = "B+Tree internal"; break;
    case BLOCK_TYPE_BPT_LEAF: s = "B+Tree leaf"; break;
    }
    return s;
  }