feat: add Namespace method to blob (#1030)

* feat: add Namespace method to blob

* lint

---------

Co-authored-by: Callum Waters <cmwaters19@gmail.com>

types/block.go

@@ -1054,6 +1054,11 @@ type Blob struct {
 	ShareVersion uint8
 }
 
+// Namespace returns the namespace of this blob encoded as a byte slice.
+func (b Blob) Namespace() []byte {
+	return append([]byte{b.NamespaceVersion}, b.NamespaceID...)
+}
+
 // StringIndented returns an indented string representation of the transactions.
 func (data *Data) StringIndented(indent string) string {
 	if data == nil {

types/block_test.go

@@ -856,3 +856,27 @@ func TestBlockIDEquals(t *testing.T) {
 	assert.True(t, blockIDEmpty.Equals(blockIDEmpty))
 	assert.False(t, blockIDEmpty.Equals(blockIDDifferent))
 }
+
+func TestBlob(t *testing.T) {
+	namespaceVersion := uint8(0)
+	namespaceID := stdbytes.Repeat([]byte{0x01}, 28)
+	data := []byte("data")
+	shareVersion := uint8(0)
+
+	blob := Blob{
+		NamespaceVersion: namespaceVersion,
+		NamespaceID:      namespaceID,
+		Data:             data,
+		ShareVersion:     shareVersion,
+	}
+
+	t.Run("blob.Namespace() returns encoded namespace", func(t *testing.T) {
+		got := blob.Namespace()
+		want := []byte{
+			0,                                        // namespace version
+			1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // namespace ID
+			1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // namespace ID
+		}
+		assert.Equal(t, want, got)
+	})
+}