feat: add digest_engine::default_digest_type()

src/digest_engine.rs

@@ -70,3 +70,15 @@ pub fn get_digest_engine(digest_type: DigestType) -> Box<dyn DigestEngine> {
         DigestType::None => Box::new(DigestEngineNone::new()),
     }
 }
+
+pub fn default_digest_type() -> DigestType {
+    let mut default = DigestType::None;
+    for digest_type in DigestType::iter() {
+        let digest_engine = get_digest_engine(digest_type.clone()).expect("Missing engine");
+        if digest_engine.is_supported() {
+            default = digest_type;
+            break;
+        }
+    }
+    default
+}