1 files changed, 36 insertions, 0 deletions
diff --git a/internal/feed/dataversion.go b/internal/feed/dataversion.go
new file mode 100644
index 0000000..c6f1b8d
--- /dev/null
+++ b/internal/feed/dataversion.go
@@ -0,0 +1,36 @@
+package feed
+
+//go:generate stringer -linecomment -type=DataVersion
+
+import (
+  "encoding/json"
+  "fmt"
+)
+
+// Data version for NVD feeds and feed items.
+type DataVersion byte
+
+const (
+  V40 DataVersion = iota // 4.0
+)
+
+// Unmarshal data version from JSON.
+func (me *DataVersion) UnmarshalJSON(b []byte) error {
+  // decode string, check for error
+  var s string
+  if err := json.Unmarshal(b, &s); err != nil {
+    return err
+  }
+
+  // check value
+  switch s {
+  case "4.0":
+    *me = V40
+  default:
+    // return error
+    return fmt.Errorf("unknown data version: %s", s)
+  }
+
+  // return success
+  return nil
+}