hashentry: Add HashEntry.String()

Add String() to HashEntry. Unlike stringify(), which is used internally,
this cannot fail. "unknown-alg" is used for unidentified algorithm
values, and "<empty>" is used if base64 encoding returns an empty
string.

Signed-off-by: Sergei Trofimov <sergei.trofimov@arm.com>

hashentry.go

@@ -150,13 +150,29 @@ func ValidHashEntry(algID uint64, value []byte) error {
 	return nil
 }
 
+// String returns a string representation of the HashEntry. The representation
+// consists of the algorithm name and the base64-encoded hash value separated by
+// a semicolon.
+func (h HashEntry) String() string {
+	sAlg, ok := algToString[h.HashAlgID]
+	if !ok {
+		sAlg = "unknown-alg"
+	}
+
+	sVal := base64.StdEncoding.EncodeToString(h.HashValue)
+	if len(sVal) == 0 {
+		sVal = "<empty>"
+	}
+
+	return sAlg + ";" + sVal
+}
+
 func (h HashEntry) stringify() (string, error) {
 	sAlg, ok := algToString[h.HashAlgID]
 	if !ok {
 		return "", fmt.Errorf("unknown hash algorithm ID %d", h.HashAlgID)
 	}
 
-	//sVal := hex.EncodeToString(h.HashValue)
 	sVal := base64.StdEncoding.EncodeToString(h.HashValue)
 	if len(sVal) == 0 {
 		return "", fmt.Errorf("empty hash value")

hashentry_test.go

@@ -277,6 +277,31 @@ func TestHashEntry_Set_OK(t *testing.T) {
 	}
 }
 
+func TestHashEntry_String(t *testing.T) {
+	for _, tv := range []struct {
+		In       HashEntry
+		Expected string
+	}{
+		{
+			In: HashEntry{
+				HashAlgID: 1,
+				HashValue: []byte{0xde, 0xad, 0xbe, 0xef},
+			},
+			Expected: "sha-256;3q2+7w==",
+		},
+		{
+			In: HashEntry{
+				HashAlgID: 1337,
+				HashValue: nil,
+			},
+			Expected: "unknown-alg;<empty>",
+		},
+	} {
+		ret := tv.In.String()
+		assert.Equal(t, tv.Expected, ret)
+	}
+}
+
 func TestHashEntry_Set_mismatched_input(t *testing.T) {
 	tvs := []struct {
 		alg uint64