code: private static void writeLineToMasterIndex(FSDataOutputStream stream, long startHash,
        long endHash, long indexStartPos, long indexEndPos) throws IOException {
      String toWrite = startHash + " " + endHash + " " + indexStartPos + " " + indexEndPos + "\n";
      stream.write(toWrite.getBytes());
    }
docs: Writes data corresponding to part of _index to master index
  @param stream stream where to write data
  @param startHash hash of first entry in block
  @param endHash hash of last entry in block
  @param indexStartPos position (in bytes) of the beginning of the block
  @param indexEndPos position (in bytes) of the end of the block
  @throws IOException