Add glide.yaml and vendor deps

vendor/github.com/docker/distribution/digest/verifiers.go

@@ -0,0 +1,44 @@
+package digest
+
+import (
+	"hash"
+	"io"
+)
+
+// Verifier presents a general verification interface to be used with message
+// digests and other byte stream verifications. Users instantiate a Verifier
+// from one of the various methods, write the data under test to it then check
+// the result with the Verified method.
+type Verifier interface {
+	io.Writer
+
+	// Verified will return true if the content written to Verifier matches
+	// the digest.
+	Verified() bool
+}
+
+// NewDigestVerifier returns a verifier that compares the written bytes
+// against a passed in digest.
+func NewDigestVerifier(d Digest) (Verifier, error) {
+	if err := d.Validate(); err != nil {
+		return nil, err
+	}
+
+	return hashVerifier{
+		hash:   d.Algorithm().Hash(),
+		digest: d,
+	}, nil
+}
+
+type hashVerifier struct {
+	digest Digest
+	hash   hash.Hash
+}
+
+func (hv hashVerifier) Write(p []byte) (n int, err error) {
+	return hv.hash.Write(p)
+}
+
+func (hv hashVerifier) Verified() bool {
+	return hv.digest == NewDigest(hv.digest.Algorithm(), hv.hash)
+}