1 files changed, 94 insertions, 0 deletions
diff --git a/pkg/name/digest.go b/pkg/name/digest.go
new file mode 100644
index 0000000..c049c1e
--- /dev/null
+++ b/pkg/name/digest.go
@@ -0,0 +1,94 @@
+// 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 name
+
+import (
+	// nolint: depguard
+	_ "crypto/sha256" // Recommended by go-digest.
+	"strings"
+
+	"github.com/opencontainers/go-digest"
+)
+
+const digestDelim = "@"
+
+// Digest stores a digest name in a structured form.
+type Digest struct {
+	Repository
+	digest   string
+	original string
+}
+
+// Ensure Digest implements Reference
+var _ Reference = (*Digest)(nil)
+
+// Context implements Reference.
+func (d Digest) Context() Repository {
+	return d.Repository
+}
+
+// Identifier implements Reference.
+func (d Digest) Identifier() string {
+	return d.DigestStr()
+}
+
+// DigestStr returns the digest component of the Digest.
+func (d Digest) DigestStr() string {
+	return d.digest
+}
+
+// Name returns the name from which the Digest was derived.
+func (d Digest) Name() string {
+	return d.Repository.Name() + digestDelim + d.DigestStr()
+}
+
+// String returns the original input string.
+func (d Digest) String() string {
+	return d.original
+}
+
+// NewDigest returns a new Digest representing the given name.
+func NewDigest(name string, opts ...Option) (Digest, error) {
+	// Split on "@"
+	parts := strings.Split(name, digestDelim)
+	if len(parts) != 2 {
+		return Digest{}, newErrBadName("a digest must contain exactly one '@' separator (e.g. registry/repository@digest) saw: %s", name)
+	}
+	base := parts[0]
+	dig := parts[1]
+	prefix := digest.Canonical.String() + ":"
+	if !strings.HasPrefix(dig, prefix) {
+		return Digest{}, newErrBadName("unsupported digest algorithm: %s", dig)
+	}
+	hex := strings.TrimPrefix(dig, prefix)
+	if err := digest.Canonical.Validate(hex); err != nil {
+		return Digest{}, err
+	}
+
+	tag, err := NewTag(base, opts...)
+	if err == nil {
+		base = tag.Repository.Name()
+	}
+
+	repo, err := NewRepository(base, opts...)
+	if err != nil {
+		return Digest{}, err
+	}
+	return Digest{
+		Repository: repo,
+		digest:     dig,
+		original:   name,
+	}, nil
+}