feat: expose type Layer, add Offset()

pkg/sif/image.go

@@ -5,6 +5,7 @@
 package sif
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 
@@ -13,19 +14,66 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/types"
 )
 
-var _ partial.CompressedImageCore = (*image)(nil)
+var _ v1.Image = (*image)(nil)
 
 type image struct {
 	f           *fileImage
 	desc        *v1.Descriptor
 	rawManifest []byte
 }
 
+// Layers returns the ordered collection of filesystem layers that comprise this image. The order
+// of the list is oldest/base layer first, and most-recent/top layer last.
+func (im *image) Layers() ([]v1.Layer, error) {
+	m, err := im.Manifest()
+	if err != nil {
+		return nil, err
+	}
+
+	ls := make([]v1.Layer, len(m.Layers))
+	for i, d := range m.Layers {
+		l, err := im.LayerByDigest(d.Digest)
+		if err != nil {
+			return nil, err
+		}
+
+		ls[i] = l
+	}
+
+	return ls, nil
+}
+
 // MediaType of this image's manifest.
 func (im *image) MediaType() (types.MediaType, error) {
 	return im.desc.MediaType, nil
 }
 
+// Size returns the size of the manifest.
+func (im *image) Size() (int64, error) {
+	return im.desc.Size, nil
+}
+
+// ConfigName returns the hash of the image's config file, also known as the Image ID.
+func (im *image) ConfigName() (v1.Hash, error) {
+	b, err := im.RawConfigFile()
+	if err != nil {
+		return v1.Hash{}, err
+	}
+
+	h, _, err := v1.SHA256(bytes.NewReader(b))
+	return h, err
+}
+
+// ConfigFile returns this image's config file.
+func (im *image) ConfigFile() (*v1.ConfigFile, error) {
+	b, err := im.RawConfigFile()
+	if err != nil {
+		return nil, err
+	}
+
+	return v1.ParseConfigFile(bytes.NewReader(b))
+}
+
 // RawConfigFile returns the serialized bytes of ConfigFile().
 func (im *image) RawConfigFile() ([]byte, error) {
 	manifest, err := im.Manifest()
@@ -36,9 +84,15 @@ func (im *image) RawConfigFile() ([]byte, error) {
 	return im.f.Bytes(manifest.Config.Digest)
 }
 
+// Digest returns the sha256 of this image's manifest.
+func (im *image) Digest() (v1.Hash, error) {
+	h, _, err := v1.SHA256(bytes.NewReader(im.rawManifest))
+	return h, err
+}
+
 // Manifest returns this image's Manifest object.
 func (im *image) Manifest() (*v1.Manifest, error) {
-	return partial.Manifest(im)
+	return v1.ParseManifest(bytes.NewReader(im.rawManifest))
 }
 
 // RawManifest returns the serialized bytes of Manifest().
@@ -55,22 +109,15 @@ var errLayerNotFoundInImage = errors.New("layer not found in image")
 
 // LayerByDigest returns a Layer for interacting with a particular layer of the image, looking it
 // up by "digest" (the compressed hash).
-func (im *image) LayerByDigest(h v1.Hash) (partial.CompressedLayer, error) {
+func (im *image) LayerByDigest(h v1.Hash) (v1.Layer, error) {
 	manifest, err := im.Manifest()
 	if err != nil {
 		return nil, err
 	}
 
-	if h == manifest.Config.Digest {
-		return &layer{
-			f:    im.f,
-			desc: manifest.Config,
-		}, nil
-	}
-
 	for _, desc := range manifest.Layers {
 		if h == desc.Digest {
-			return &layer{
+			return &Layer{
 				f:    im.f,
 				desc: desc,
 			}, nil
@@ -79,3 +126,13 @@ func (im *image) LayerByDigest(h v1.Hash) (partial.CompressedLayer, error) {
 
 	return nil, fmt.Errorf("%w: %v", errLayerNotFoundInImage, h)
 }
+
+// LayerByDiffID is an analog to LayerByDigest, looking up by "diff id" (the uncompressed hash).
+func (im *image) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
+	h, err := partial.DiffIDToBlob(im, h)
+	if err != nil {
+		return nil, err
+	}
+
+	return im.LayerByDigest(h)
+}

pkg/sif/image_test.go

@@ -9,7 +9,6 @@ import (
 	"testing"
 
 	v1 "github.com/google/go-containerregistry/pkg/v1"
-	"github.com/google/go-containerregistry/pkg/v1/partial"
 	"github.com/google/go-containerregistry/pkg/v1/validate"
 )
 
@@ -76,7 +75,7 @@ func TestFile_Image(t *testing.T) {
 				t.Error(err)
 			}
 
-			if d, err := partial.Descriptor(img); err != nil {
+			if d, err := img.(withDescriptor).Descriptor(); err != nil {
 				t.Error(err)
 			} else if got, want := d, tt.wantDescriptor; !reflect.DeepEqual(got, want) {
 				t.Errorf("got descriptor %+v, want %+v", got, want)

pkg/sif/index.go

@@ -11,7 +11,6 @@ import (
 	"fmt"
 
 	v1 "github.com/google/go-containerregistry/pkg/v1"
-	"github.com/google/go-containerregistry/pkg/v1/partial"
 	"github.com/google/go-containerregistry/pkg/v1/types"
 	"github.com/sylabs/sif/v2/pkg/sif"
 )
@@ -116,7 +115,7 @@ func (ix *imageIndex) Image(h v1.Hash) (v1.Image, error) {
 		desc:        desc,
 		rawManifest: b,
 	}
-	return partial.CompressedToImage(&img)
+	return &img, nil
 }
 
 // ImageIndex returns a v1.ImageIndex that this ImageIndex references.

pkg/sif/layer.go

@@ -12,34 +12,61 @@ import (
 	"github.com/google/go-containerregistry/pkg/v1/types"
 )
 
-var _ partial.CompressedLayer = (*layer)(nil)
+var _ v1.Layer = (*Layer)(nil)
 
-type layer struct {
+type Layer struct {
 	f    *fileImage
 	desc v1.Descriptor
 }
 
 // Digest returns the Hash of the compressed layer.
-func (l *layer) Digest() (v1.Hash, error) {
+func (l *Layer) Digest() (v1.Hash, error) {
 	return l.desc.Digest, nil
 }
 
+// DiffID returns the Hash of the uncompressed layer.
+func (l *Layer) DiffID() (v1.Hash, error) {
+	r, err := l.Uncompressed()
+	if err != nil {
+		return v1.Hash{}, err
+	}
+	defer r.Close()
+
+	h, _, err := v1.SHA256(r)
+	return h, err
+}
+
 // Compressed returns an io.ReadCloser for the compressed layer contents.
-func (l *layer) Compressed() (io.ReadCloser, error) {
+func (l *Layer) Compressed() (io.ReadCloser, error) {
 	return l.f.Blob(l.desc.Digest)
 }
 
+// Uncompressed returns an io.ReadCloser for the uncompressed layer contents.
+func (l *Layer) Uncompressed() (io.ReadCloser, error) {
+	cl, err := partial.CompressedToLayer(l)
+	if err != nil {
+		return nil, err
+	}
+
+	return cl.Uncompressed()
+}
+
 // Size returns the compressed size of the Layer.
-func (l *layer) Size() (int64, error) {
+func (l *Layer) Size() (int64, error) {
 	return l.desc.Size, nil
 }
 
+// Offset returns the offset within the SIF image of the Layer.
+func (l *Layer) Offset() (int64, error) {
+	return l.f.Offset(l.desc.Digest)
+}
+
 // MediaType returns the media type of the Layer.
-func (l *layer) MediaType() (types.MediaType, error) {
+func (l *Layer) MediaType() (types.MediaType, error) {
 	return l.desc.MediaType, nil
 }
 
 // Descriptor returns the original descriptor from an image manifest. See partial.Descriptor.
-func (l *layer) Descriptor() (*v1.Descriptor, error) {
+func (l *Layer) Descriptor() (*v1.Descriptor, error) {
 	return &l.desc, nil
 }

pkg/sif/sif.go

@@ -35,3 +35,13 @@ func (f *fileImage) Bytes(h v1.Hash) ([]byte, error) {
 
 	return d.GetData()
 }
+
+// Offset returns the offset within the SIF image of the blob with the supplied digest.
+func (f *fileImage) Offset(h v1.Hash) (int64, error) {
+	d, err := f.GetDescriptor(sif.WithOCIBlobDigest(h))
+	if err != nil {
+		return 0, err
+	}
+
+	return d.Offset(), nil
+}