1 files changed, 52 insertions, 0 deletions
diff --git a/pkg/crane/digest.go b/pkg/crane/digest.go
new file mode 100644
index 0000000..868a570
--- /dev/null
+++ b/pkg/crane/digest.go
@@ -0,0 +1,52 @@
+// 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 crane
+
+import "github.com/google/go-containerregistry/pkg/logs"
+
+// Digest returns the sha256 hash of the remote image at ref.
+func Digest(ref string, opt ...Option) (string, error) {
+	o := makeOptions(opt...)
+	if o.Platform != nil {
+		desc, err := getManifest(ref, opt...)
+		if err != nil {
+			return "", err
+		}
+		if !desc.MediaType.IsIndex() {
+			return desc.Digest.String(), nil
+		}
+
+		// TODO: does not work for indexes which contain schema v1 manifests
+		img, err := desc.Image()
+		if err != nil {
+			return "", err
+		}
+		digest, err := img.Digest()
+		if err != nil {
+			return "", err
+		}
+		return digest.String(), nil
+	}
+	desc, err := Head(ref, opt...)
+	if err != nil {
+		logs.Warn.Printf("HEAD request failed, falling back on GET: %v", err)
+		rdesc, err := getManifest(ref, opt...)
+		if err != nil {
+			return "", err
+		}
+		return rdesc.Digest.String(), nil
+	}
+	return desc.Digest.String(), nil
+}