Implement OCI Image Layout support

pkg/v1/layout/blob.go

@@ -0,0 +1,38 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package layout
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+
+	"github.com/google/go-containerregistry/pkg/v1"
+)
+
+// Blob returns a blob with the given hash from the Path.
+func (l Path) Blob(h v1.Hash) (io.ReadCloser, error) {
+	return os.Open(l.blobPath(h))
+}
+
+// Bytes is a convenience function to return a blob from the Path as
+// a byte slice.
+func (l Path) Bytes(h v1.Hash) ([]byte, error) {
+	return ioutil.ReadFile(l.blobPath(h))
+}
+
+func (l Path) blobPath(h v1.Hash) string {
+	return l.path("blobs", h.Algorithm, h.Hex)
+}

pkg/v1/layout/doc.go

@@ -0,0 +1,19 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package layout provides facilities for reading/writing artifacts from/to
+// an OCI image layout on disk, see:
+//
+// https://github.com/opencontainers/image-spec/blob/master/image-layout.md
+package layout

pkg/v1/layout/image.go

@@ -0,0 +1,127 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package layout
+
+import (
+	"fmt"
+	"io"
+	"sync"
+
+	"github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/partial"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+type layoutImage struct {
+	path         Path
+	desc         v1.Descriptor
+	manifestLock sync.Mutex // Protects rawManifest
+	rawManifest  []byte
+}
+
+var _ partial.CompressedImageCore = (*layoutImage)(nil)
+
+// Image reads a v1.Image with digest h from the Path.
+func (l Path) Image(h v1.Hash) (v1.Image, error) {
+	ii, err := l.ImageIndex()
+	if err != nil {
+		return nil, err
+	}
+
+	return ii.Image(h)
+}
+
+func (li *layoutImage) MediaType() (types.MediaType, error) {
+	return li.desc.MediaType, nil
+}
+
+// Implements WithManifest for partial.Blobset.
+func (li *layoutImage) Manifest() (*v1.Manifest, error) {
+	return partial.Manifest(li)
+}
+
+func (li *layoutImage) RawManifest() ([]byte, error) {
+	li.manifestLock.Lock()
+	defer li.manifestLock.Unlock()
+	if li.rawManifest != nil {
+		return li.rawManifest, nil
+	}
+
+	b, err := li.path.Bytes(li.desc.Digest)
+	if err != nil {
+		return nil, err
+	}
+
+	li.rawManifest = b
+	return li.rawManifest, nil
+}
+
+func (li *layoutImage) RawConfigFile() ([]byte, error) {
+	manifest, err := li.Manifest()
+	if err != nil {
+		return nil, err
+	}
+
+	return li.path.Bytes(manifest.Config.Digest)
+}
+
+func (li *layoutImage) LayerByDigest(h v1.Hash) (partial.CompressedLayer, error) {
+	manifest, err := li.Manifest()
+	if err != nil {
+		return nil, err
+	}
+
+	if h == manifest.Config.Digest {
+		return partial.CompressedLayer(&compressedBlob{
+			path: li.path,
+			desc: manifest.Config,
+		}), nil
+	}
+
+	for _, desc := range manifest.Layers {
+		if h == desc.Digest {
+			switch desc.MediaType {
+			case types.OCILayer, types.DockerLayer:
+				return partial.CompressedToLayer(&compressedBlob{
+					path: li.path,
+					desc: desc,
+				})
+			default:
+				// TODO: We assume everything is a compressed blob, but that might not be true.
+				// TODO: Handle foreign layers.
+				return nil, fmt.Errorf("unexpected media type: %v for layer: %v", desc.MediaType, desc.Digest)
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("could not find layer in image: %s", h)
+}
+
+type compressedBlob struct {
+	path Path
+	desc v1.Descriptor
+}
+
+func (b *compressedBlob) Digest() (v1.Hash, error) {
+	return b.desc.Digest, nil
+}
+
+func (b *compressedBlob) Compressed() (io.ReadCloser, error) {
+	return b.path.Blob(b.desc.Digest)
+}
+
+func (b *compressedBlob) Size() (int64, error) {
+	return b.desc.Size, nil
+}

pkg/v1/layout/image_test.go

@@ -0,0 +1,108 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package layout
+
+import (
+	"testing"
+
+	"github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+	"github.com/google/go-containerregistry/pkg/v1/validate"
+)
+
+var (
+	indexDigest = v1.Hash{
+		Algorithm: "sha256",
+		Hex:       "05f95b26ed10668b7183c1e2da98610e91372fa9f510046d4ce5812addad86b5",
+	}
+	manifestDigest = v1.Hash{
+		Algorithm: "sha256",
+		Hex:       "eebff607b1628d67459b0596643fc07de70d702eccf030f0bc7bb6fc2b278650",
+	}
+	configDigest = v1.Hash{
+		Algorithm: "sha256",
+		Hex:       "6e0b05049ed9c17d02e1a55e80d6599dbfcce7f4f4b022e3c673e685789c470e",
+	}
+	bogusDigest = v1.Hash{
+		Algorithm: "sha256",
+		Hex:       "deadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef",
+	}
+	bogusPath = "testdata/does_not_exist"
+	testPath  = "testdata/test_index"
+)
+
+func TestImage(t *testing.T) {
+	lp, err := FromPath(testPath)
+	if err != nil {
+		t.Fatalf("FromPath() = %v", err)
+	}
+	img, err := lp.Image(manifestDigest)
+	if err != nil {
+		t.Fatalf("Image() = %v", err)
+	}
+
+	if err := validate.Image(img); err != nil {
+		t.Errorf("validate.Image() = %v", err)
+	}
+
+	mt, err := img.MediaType()
+	if err != nil {
+		t.Errorf("MediaType() = %v", err)
+	} else if got, want := mt, types.OCIManifestSchema1; got != want {
+		t.Errorf("MediaType(); want: %v got: %v", want, got)
+	}
+
+	cfg, err := img.LayerByDigest(configDigest)
+	if err != nil {
+		t.Fatalf("LayerByDigest(%s) = %v", configDigest, err)
+	}
+
+	cfgName, err := img.ConfigName()
+	if err != nil {
+		t.Fatalf("ConfigName() = %v", err)
+	}
+
+	cfgDigest, err := cfg.Digest()
+	if err != nil {
+		t.Fatalf("cfg.Digest() = %v", err)
+	}
+
+	if got, want := cfgDigest, cfgName; got != want {
+		t.Errorf("ConfigName(); want: %v got: %v", want, got)
+	}
+}
+
+func TestImageErrors(t *testing.T) {
+	lp, err := FromPath(testPath)
+	if err != nil {
+		t.Fatalf("FromPath() = %v", err)
+	}
+	img, err := lp.Image(manifestDigest)
+	if err != nil {
+		t.Fatalf("Image() = %v", err)
+	}
+
+	if _, err := img.LayerByDigest(bogusDigest); err == nil {
+		t.Errorf("LayerByDigest(%s) = nil, expected err", bogusDigest)
+	}
+
+	if _, err := lp.Image(bogusDigest); err == nil {
+		t.Errorf("Image(%s) = nil, expected err", bogusDigest)
+	}
+
+	if _, err := lp.Image(bogusDigest); err == nil {
+		t.Errorf("Image(%s, %s) = nil, expected err", bogusPath, bogusDigest)
+	}
+}