1 files changed, 53 insertions, 0 deletions
diff --git a/libpod/diff.go b/libpod/diff.go
new file mode 100644
index 000000000..055bb7fe8
--- /dev/null
+++ b/libpod/diff.go
@@ -0,0 +1,53 @@
+package libpod
+
+import (
+	"github.com/containers/storage/pkg/archive"
+	"github.com/kubernetes-incubator/cri-o/libpod/layers"
+	"github.com/pkg/errors"
+)
+
+// GetDiff returns the differences between the two images, layers, or containers
+func (r *Runtime) GetDiff(from, to string) ([]archive.Change, error) {
+	toLayer, err := r.getLayerID(to)
+	if err != nil {
+		return nil, err
+	}
+	fromLayer := ""
+	if from != "" {
+		fromLayer, err = r.getLayerID(from)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return r.store.Changes(fromLayer, toLayer)
+}
+
+// GetLayerID gets a full layer id given a full or partial id
+// If the id matches a container or image, the id of the top layer is returned
+// If the id matches a layer, the top layer id is returned
+func (r *Runtime) getLayerID(id string) (string, error) {
+	var toLayer string
+	toImage, err := r.GetImage(id)
+	if err != nil {
+		toCtr, err := r.store.Container(id)
+		if err != nil {
+			toLayer, err = layers.FullID(r.store, id)
+			if err != nil {
+				return "", errors.Errorf("layer, image, or container %s does not exist", id)
+			}
+		} else {
+			toLayer = toCtr.LayerID
+		}
+	} else {
+		toLayer = toImage.TopLayer
+	}
+	return toLayer, nil
+}
+
+func (r *Runtime) getLayerParent(layerID string) (string, error) {
+	layer, err := r.store.Layer(layerID)
+	if err != nil {
+		return "", err
+	}
+	return layer.Parent, nil
+}