ReadVersion(ctx context.Context, origvolume, volume, path, versionID string, opts ReadOptions) (FileInfo, error)
	ReadXL(ctx context.Context, volume, path string, readData bool) (RawFileInfo, error)
	RenameData(ctx context.Context, srcVolume, srcPath string, fi FileInfo, dstVolume, dstPath string, opts RenameOptions) (RenameDataResp, error)

	// File operations.

    while (true) {
      when (source.select(options)) {
        in 0..2 -> {
          completeEvent(id, type, data)
          return true
        }

        in 3..4 -> {
          source.readData(data)
        }

        in 5..7 -> {
          data.writeByte('\n'.code) // 'data' on a line of its own.
        }

        in 8..9 -> {
          id = source.readUtf8LineStrict().takeIf { it.isNotEmpty() }