1 files changed, 188 insertions, 0 deletions
diff --git a/pkg/v1/partial/compressed.go b/pkg/v1/partial/compressed.go
new file mode 100644
index 0000000..44989ac
--- /dev/null
+++ b/pkg/v1/partial/compressed.go
@@ -0,0 +1,188 @@
+// 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 partial
+
+import (
+	"io"
+
+	"github.com/google/go-containerregistry/internal/and"
+	"github.com/google/go-containerregistry/internal/compression"
+	"github.com/google/go-containerregistry/internal/gzip"
+	"github.com/google/go-containerregistry/internal/zstd"
+	comp "github.com/google/go-containerregistry/pkg/compression"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/types"
+)
+
+// CompressedLayer represents the bare minimum interface a natively
+// compressed layer must implement for us to produce a v1.Layer
+type CompressedLayer interface {
+	// Digest returns the Hash of the compressed layer.
+	Digest() (v1.Hash, error)
+
+	// Compressed returns an io.ReadCloser for the compressed layer contents.
+	Compressed() (io.ReadCloser, error)
+
+	// Size returns the compressed size of the Layer.
+	Size() (int64, error)
+
+	// Returns the mediaType for the compressed Layer
+	MediaType() (types.MediaType, error)
+}
+
+// compressedLayerExtender implements v1.Image using the compressed base properties.
+type compressedLayerExtender struct {
+	CompressedLayer
+}
+
+// Uncompressed implements v1.Layer
+func (cle *compressedLayerExtender) Uncompressed() (io.ReadCloser, error) {
+	rc, err := cle.Compressed()
+	if err != nil {
+		return nil, err
+	}
+
+	// Often, the "compressed" bytes are not actually-compressed.
+	// Peek at the first two bytes to determine whether it's correct to
+	// wrap this with gzip.UnzipReadCloser or zstd.UnzipReadCloser.
+	cp, pr, err := compression.PeekCompression(rc)
+	if err != nil {
+		return nil, err
+	}
+
+	prc := &and.ReadCloser{
+		Reader:    pr,
+		CloseFunc: rc.Close,
+	}
+
+	switch cp {
+	case comp.GZip:
+		return gzip.UnzipReadCloser(prc)
+	case comp.ZStd:
+		return zstd.UnzipReadCloser(prc)
+	default:
+		return prc, nil
+	}
+}
+
+// DiffID implements v1.Layer
+func (cle *compressedLayerExtender) DiffID() (v1.Hash, error) {
+	// If our nested CompressedLayer implements DiffID,
+	// then delegate to it instead.
+	if wdi, ok := cle.CompressedLayer.(WithDiffID); ok {
+		return wdi.DiffID()
+	}
+	r, err := cle.Uncompressed()
+	if err != nil {
+		return v1.Hash{}, err
+	}
+	defer r.Close()
+	h, _, err := v1.SHA256(r)
+	return h, err
+}
+
+// CompressedToLayer fills in the missing methods from a CompressedLayer so that it implements v1.Layer
+func CompressedToLayer(ul CompressedLayer) (v1.Layer, error) {
+	return &compressedLayerExtender{ul}, nil
+}
+
+// CompressedImageCore represents the base minimum interface a natively
+// compressed image must implement for us to produce a v1.Image.
+type CompressedImageCore interface {
+	ImageCore
+
+	// RawManifest returns the serialized bytes of the manifest.
+	RawManifest() ([]byte, error)
+
+	// LayerByDigest is a variation on the v1.Image method, which returns
+	// a CompressedLayer instead.
+	LayerByDigest(v1.Hash) (CompressedLayer, error)
+}
+
+// compressedImageExtender implements v1.Image by extending CompressedImageCore with the
+// appropriate methods computed from the minimal core.
+type compressedImageExtender struct {
+	CompressedImageCore
+}
+
+// Assert that our extender type completes the v1.Image interface
+var _ v1.Image = (*compressedImageExtender)(nil)
+
+// Digest implements v1.Image
+func (i *compressedImageExtender) Digest() (v1.Hash, error) {
+	return Digest(i)
+}
+
+// ConfigName implements v1.Image
+func (i *compressedImageExtender) ConfigName() (v1.Hash, error) {
+	return ConfigName(i)
+}
+
+// Layers implements v1.Image
+func (i *compressedImageExtender) Layers() ([]v1.Layer, error) {
+	hs, err := FSLayers(i)
+	if err != nil {
+		return nil, err
+	}
+	ls := make([]v1.Layer, 0, len(hs))
+	for _, h := range hs {
+		l, err := i.LayerByDigest(h)
+		if err != nil {
+			return nil, err
+		}
+		ls = append(ls, l)
+	}
+	return ls, nil
+}
+
+// LayerByDigest implements v1.Image
+func (i *compressedImageExtender) LayerByDigest(h v1.Hash) (v1.Layer, error) {
+	cl, err := i.CompressedImageCore.LayerByDigest(h)
+	if err != nil {
+		return nil, err
+	}
+	return CompressedToLayer(cl)
+}
+
+// LayerByDiffID implements v1.Image
+func (i *compressedImageExtender) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
+	h, err := DiffIDToBlob(i, h)
+	if err != nil {
+		return nil, err
+	}
+	return i.LayerByDigest(h)
+}
+
+// ConfigFile implements v1.Image
+func (i *compressedImageExtender) ConfigFile() (*v1.ConfigFile, error) {
+	return ConfigFile(i)
+}
+
+// Manifest implements v1.Image
+func (i *compressedImageExtender) Manifest() (*v1.Manifest, error) {
+	return Manifest(i)
+}
+
+// Size implements v1.Image
+func (i *compressedImageExtender) Size() (int64, error) {
+	return Size(i)
+}
+
+// CompressedToImage fills in the missing methods from a CompressedImageCore so that it implements v1.Image
+func CompressedToImage(cic CompressedImageCore) (v1.Image, error) {
+	return &compressedImageExtender{
+		CompressedImageCore: cic,
+	}, nil
+}