1 files changed, 91 insertions, 0 deletions
diff --git a/cmd/crane/cmd/digest.go b/cmd/crane/cmd/digest.go
new file mode 100644
index 0000000..2060bbc
--- /dev/null
+++ b/cmd/crane/cmd/digest.go
@@ -0,0 +1,91 @@
+// 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 cmd
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/spf13/cobra"
+)
+
+// NewCmdDigest creates a new cobra.Command for the digest subcommand.
+func NewCmdDigest(options *[]crane.Option) *cobra.Command {
+	var tarball string
+	var fullRef bool
+	cmd := &cobra.Command{
+		Use:   "digest IMAGE",
+		Short: "Get the digest of an image",
+		Args:  cobra.MaximumNArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if tarball == "" && len(args) == 0 {
+				if err := cmd.Help(); err != nil {
+					return err
+				}
+				return errors.New("image reference required without --tarball")
+			}
+			if fullRef && tarball != "" {
+				return errors.New("cannot specify --full-ref with --tarball")
+			}
+
+			digest, err := getDigest(tarball, args, options)
+			if err != nil {
+				return err
+			}
+			if fullRef {
+				ref, err := name.ParseReference(args[0])
+				if err != nil {
+					return err
+				}
+				fmt.Println(ref.Context().Digest(digest))
+			} else {
+				fmt.Println(digest)
+			}
+			return nil
+		},
+	}
+
+	cmd.Flags().StringVar(&tarball, "tarball", "", "(Optional) path to tarball containing the image")
+	cmd.Flags().BoolVar(&fullRef, "full-ref", false, "(Optional) if true, print the full image reference by digest")
+
+	return cmd
+}
+
+func getDigest(tarball string, args []string, options *[]crane.Option) (string, error) {
+	if tarball != "" {
+		return getTarballDigest(tarball, args, options)
+	}
+
+	return crane.Digest(args[0], *options...)
+}
+
+func getTarballDigest(tarball string, args []string, options *[]crane.Option) (string, error) {
+	tag := ""
+	if len(args) > 0 {
+		tag = args[0]
+	}
+
+	img, err := crane.LoadTag(tarball, tag, *options...)
+	if err != nil {
+		return "", fmt.Errorf("loading image from %q: %w", tarball, err)
+	}
+	digest, err := img.Digest()
+	if err != nil {
+		return "", fmt.Errorf("computing digest: %w", err)
+	}
+	return digest.String(), nil
+}