move code supporting push, pull, and inspect to libkpod and libkpod/image

Signed-off-by: Ryan Cole <rcyoalne@gmail.com>

libkpod/container.go

@@ -2,6 +2,7 @@ package libkpod
 
 import (
 	cstorage "github.com/containers/storage"
+	"github.com/pkg/errors"
 )
 
 // FindContainer searches for a container with the given name or ID in the given store
@@ -46,3 +47,51 @@ func GetContainerRwSize(store cstorage.Store, containerID string) (int64, error)
 	}
 	return lstore.DiffSize(layer.Parent, layer.ID)
 }
+
+// GetContainerRootFsSize gets the size of the container's root filesystem
+// A container FS is split into two parts.  The first is the top layer, a
+// mutable layer, and the rest is the RootFS: the set of immutable layers
+// that make up the image on which the container is based
+func GetContainerRootFsSize(store cstorage.Store, containerID string) (int64, error) {
+	ctrStore, err := store.ContainerStore()
+	if err != nil {
+		return 0, err
+	}
+	container, err := ctrStore.Get(containerID)
+	if err != nil {
+		return 0, err
+	}
+	lstore, err := store.LayerStore()
+	if err != nil {
+		return 0, err
+	}
+
+	// Ignore the size of the top layer.   The top layer is a mutable RW layer
+	// and is not considered a part of the rootfs
+	rwLayer, err := lstore.Get(container.LayerID)
+	if err != nil {
+		return 0, err
+	}
+	layer, err := lstore.Get(rwLayer.Parent)
+	if err != nil {
+		return 0, err
+	}
+
+	size := int64(0)
+	for layer.Parent != "" {
+		layerSize, err := lstore.DiffSize(layer.Parent, layer.ID)
+		if err != nil {
+			return size, errors.Wrapf(err, "getting diffsize of layer %q and its parent %q", layer.ID, layer.Parent)
+		}
+		size += layerSize
+		layer, err = lstore.Get(layer.Parent)
+		if err != nil {
+			return 0, err
+		}
+	}
+	// Get the size of the last layer.  Has to be outside of the loop
+	// because the parent of the last layer is "", andlstore.Get("")
+	// will return an error
+	layerSize, err := lstore.DiffSize(layer.Parent, layer.ID)
+	return size + layerSize, err
+}