code: func (d *Driver) importLayer(id string, layerData io.Reader, parentLayerPaths []string) (size int64, err error) {
  	if !noreexec {
  		cmd := reexec.Command(append([]string{"docker-windows-write-layer", d.info.HomeDir, id}, parentLayerPaths...)...)
  		output := bytes.NewBuffer(nil)
  		cmd.Stdin = layerData
  		cmd.Stdout = output
  		cmd.Stderr = output
  
  		if err = cmd.Start(); err != nil {
  			return
  		}
  
  		if err = cmd.Wait(); err != nil {
  			return 0, fmt.Errorf("re-exec error: %v: output: %s", err, output)
  		}
  
  		return strconv.ParseInt(output.String(), 10, 64)
  	}
  	return writeLayer(layerData, d.info.HomeDir, id, parentLayerPaths...)
  }
docs: // importLayer adds a new layer to the tag and graph store based on the given data.