Merge pull request containers#371 from nalind/tarball

Add a "tarball" transport for treating discrete tarballs as image layers

docs/policy.json.md

@@ -99,6 +99,12 @@ a directory containing one or more tags, or any of the parent directories.
 
 *Note:* See `dir:` above for semantics and restrictions on the directory paths, they apply to `oci:` equivalently.
 
+### `tarball:`
+
+The `tarball:` transport refers to tarred up container root filesystems.
+
+Scopes are ignored.
+
 ## Policy Requirements
 
 Using the mechanisms above, a set of policy requirements is looked up.  The policy requirements

tarball/doc.go

@@ -0,0 +1,48 @@
+// Package tarball provides a way to generate images using one or more layer
+// tarballs and an optional template configuration.
+//
+// An example:
+//	package main
+//
+//	import (
+//		"fmt"
+//
+//		cp "github.com/containers/image/copy"
+//		"github.com/containers/image/tarball"
+//		"github.com/containers/image/transports/alltransports"
+//
+//		imgspecv1 "github.com/containers/image/transports/alltransports"
+//	)
+//
+//	func imageFromTarball() {
+//		src, err := alltransports.ParseImageName("tarball:/var/cache/mock/fedora-26-x86_64/root_cache/cache.tar.gz")
+//		// - or -
+//		// src, err := tarball.Transport.ParseReference("/var/cache/mock/fedora-26-x86_64/root_cache/cache.tar.gz")
+//		if err != nil {
+//			panic(err)
+//		}
+//		updater, ok := src.(tarball.ConfigUpdater)
+//		if !ok {
+//			panic("unexpected: a tarball reference should implement tarball.ConfigUpdater")
+//		}
+//		config := imgspecv1.Image{
+//			Config: imgspecv1.ImageConfig{
+//				Cmd: []string{"/bin/bash"},
+//			},
+//		}
+//		annotations := make(map[string]string)
+//		annotations[imgspecv1.AnnotationDescription] = "test image built from a mock root cache"
+//		err = updater.ConfigUpdate(config, annotations)
+//		if err != nil {
+//			panic(err)
+//		}
+//		dest, err := alltransports.ParseImageName("docker-daemon:mock:latest")
+//		if err != nil {
+//			panic(err)
+//		}
+//		err = cp.Image(nil, dest, src, nil)
+//		if err != nil {
+//			panic(err)
+//		}
+//	}
+package tarball

tarball/tarball_reference.go

@@ -0,0 +1,88 @@
+package tarball
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/containers/image/docker/reference"
+	"github.com/containers/image/image"
+	"github.com/containers/image/types"
+
+	imgspecv1 "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// ConfigUpdater is an interface that ImageReferences for "tarball" images also
+// implement.  It can be used to set values for a configuration, and to set
+// image annotations which will be present in the images returned by the
+// reference's NewImage() or NewImageSource() methods.
+type ConfigUpdater interface {
+	ConfigUpdate(config imgspecv1.Image, annotations map[string]string) error
+}
+
+type tarballReference struct {
+	transport   types.ImageTransport
+	config      imgspecv1.Image
+	annotations map[string]string
+	filenames   []string
+	stdin       []byte
+}
+
+// ConfigUpdate updates the image's default configuration and adds annotations
+// which will be visible in source images created using this reference.
+func (r *tarballReference) ConfigUpdate(config imgspecv1.Image, annotations map[string]string) error {
+	r.config = config
+	if r.annotations == nil {
+		r.annotations = make(map[string]string)
+	}
+	for k, v := range annotations {
+		r.annotations[k] = v
+	}
+	return nil
+}
+
+func (r *tarballReference) Transport() types.ImageTransport {
+	return r.transport
+}
+
+func (r *tarballReference) StringWithinTransport() string {
+	return strings.Join(r.filenames, ":")
+}
+
+func (r *tarballReference) DockerReference() reference.Named {
+	return nil
+}
+
+func (r *tarballReference) PolicyConfigurationIdentity() string {
+	return ""
+}
+
+func (r *tarballReference) PolicyConfigurationNamespaces() []string {
+	return nil
+}
+
+func (r *tarballReference) NewImage(ctx *types.SystemContext) (types.Image, error) {
+	src, err := r.NewImageSource(ctx)
+	if err != nil {
+		return nil, err
+	}
+	img, err := image.FromSource(src)
+	if err != nil {
+		src.Close()
+		return nil, err
+	}
+	return img, nil
+}
+
+func (r *tarballReference) DeleteImage(ctx *types.SystemContext) error {
+	for _, filename := range r.filenames {
+		if err := os.Remove(filename); err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("error removing %q: %v", filename, err)
+		}
+	}
+	return nil
+}
+
+func (r *tarballReference) NewImageDestination(ctx *types.SystemContext) (types.ImageDestination, error) {
+	return nil, fmt.Errorf("destination not implemented yet")
+}