}
        return null
      }
    }

    private fun newSource(index: Int): Source {
      val fileSource = fileSystem.source(cleanFiles[index])
      if (civilizedFileSystem) return fileSource

      lockingSourceCount++
      return object : ForwardingSource(fileSource) {
        private var closed = false

        override fun close() {
          super.close()
          if (!closed) {