Add DigestIfAlgorithmUnknown

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Author: mtrmac

image/internal/putblobdigest/put_blob_digest.go

@@ -13,15 +13,15 @@ type Digester struct {
 	digester    digest.Digester // Or nil
 }
 
-// newDigester initiates computation of a digest.Canonical digest of stream,
+// newDigester initiates computation of a digest of stream using the specified algorithm,
 // if !validDigest; otherwise it just records knownDigest to be returned later.
 // The caller MUST use the returned stream instead of the original value.
-func newDigester(stream io.Reader, knownDigest digest.Digest, validDigest bool) (Digester, io.Reader) {
+func newDigester(stream io.Reader, knownDigest digest.Digest, validDigest bool, algorithm digest.Algorithm) (Digester, io.Reader) {
 	if validDigest {
 		return Digester{knownDigest: knownDigest}, stream
 	} else {
 		res := Digester{
-			digester: digest.Canonical.Digester(),
+			digester: algorithm.Digester(),
 		}
 		stream = io.TeeReader(stream, res.digester.Hash())
 		return res, stream
@@ -34,7 +34,7 @@ func newDigester(stream io.Reader, knownDigest digest.Digest, validDigest bool)
 // The caller MUST use the returned stream instead of the original value.
 func DigestIfUnknown(stream io.Reader, blobInfo types.BlobInfo) (Digester, io.Reader) {
 	d := blobInfo.Digest
-	return newDigester(stream, d, d != "")
+	return newDigester(stream, d, d != "", digest.Canonical)
 }
 
 // DigestIfCanonicalUnknown initiates computation of a digest.Canonical digest of stream,
@@ -43,7 +43,16 @@ func DigestIfUnknown(stream io.Reader, blobInfo types.BlobInfo) (Digester, io.Re
 // The caller MUST use the returned stream instead of the original value.
 func DigestIfCanonicalUnknown(stream io.Reader, blobInfo types.BlobInfo) (Digester, io.Reader) {
 	d := blobInfo.Digest
-	return newDigester(stream, d, d != "" && d.Algorithm() == digest.Canonical)
+	return newDigester(stream, d, d != "" && d.Algorithm() == digest.Canonical, digest.Canonical)
+}
+
+// DigestIfAlgorithmUnknown initiates computation of a digest of stream,
+// if a digest of the specified algorithm is not supplied in the provided blobInfo;
+// otherwise blobInfo.Digest will be used.
+// The caller MUST use the returned stream instead of the original value.
+func DigestIfAlgorithmUnknown(stream io.Reader, blobInfo types.BlobInfo, algorithm digest.Algorithm) (Digester, io.Reader) {
+	d := blobInfo.Digest
+	return newDigester(stream, d, d != "" && d.Algorithm() == algorithm, algorithm)
 }
 
 // Digest() returns a digest value possibly computed by Digester.

image/internal/putblobdigest/put_blob_digest_test.go

@@ -73,3 +73,30 @@ func TestDigestIfCanonicalUnknown(t *testing.T) {
 		},
 	})
 }
+
+func TestDigestIfAlgorithmUnknown(t *testing.T) {
+	testDigester(t, func(r io.Reader, bi types.BlobInfo) (Digester, io.Reader) {
+		return DigestIfAlgorithmUnknown(r, bi, digest.SHA512)
+	}, []testCase{
+		{
+			inputDigest:    digest.Digest("sha512:uninspected-value"),
+			computesDigest: false,
+			expectedDigest: digest.Digest("sha512:uninspected-value"),
+		},
+		{
+			inputDigest:    digest.Digest("sha256:uninspected-value"),
+			computesDigest: true,
+			expectedDigest: digest.SHA512.FromBytes(testData),
+		},
+		{
+			inputDigest:    digest.Digest("unknown-algorithm:uninspected-value"),
+			computesDigest: true,
+			expectedDigest: digest.SHA512.FromBytes(testData),
+		},
+		{
+			inputDigest:    "",
+			computesDigest: true,
+			expectedDigest: digest.SHA512.FromBytes(testData),
+		},
+	})
+}