Function Export

pkg/crane/export.go:27–55

Export writes the filesystem contents (as a tarball) of img to w. If img has a single layer, just write the (uncompressed) contents to w so that this "just works" for images that just wrap a single blob.

(img v1.Image, w io.Writer)

// If img has a single layer, just write the (uncompressed) contents to w so
// that this "just works" for images that just wrap a single blob.
func Export(img v1.Image, w io.Writer) error {
	layers, err := img.Layers()
	if err != nil {
		return err
	}
	if len(layers) == 1 {
		// If it's a single layer...
		l := layers[0]
		mt, err := l.MediaType()
		if err != nil {
			return err
		}

		if !mt.IsLayer() {
			// ...and isn't an OCI mediaType, we don't have to flatten it.
			// This lets export work for single layer, non-tarball images.
			rc, err := l.Uncompressed()
			if err != nil {
				return err
			}
			defer rc.Close()
			_, err = io.Copy(w, rc)
			return err
		}
	}
	fs := mutate.Extract(img)
	_, err = io.Copy(w, fs)
	return err
}