/** Returns the unbuffered stream with the value for [index]. */
    fun getSource(index: Int): Source = sources[index]

    /** Returns the byte length of the value for [index]. */
    fun getLength(index: Int): Long = lengths[index]

    override fun close() {
      for (source in sources) {
        source.closeQuietly()
      }
    }
  }

  /** Edits the values for an entry. */