refactor GetNamespace to simplify logic and improve readability

Author: allnes

modules/core/util/include/util.hpp

@@ -51,18 +51,21 @@ int GetNumThreads();
 template <typename T>
 constexpr std::string_view GetNamespace() {
 #if defined(_MSC_VER)
-  constexpr auto func = std::string_view{__FUNCSIG__};
+  constexpr std::string_view func{__FUNCSIG__};
   auto start = func.find("GetNamespace<") + 13;
   for (auto p : {"class ", "struct ", "enum ", "union "})
-    if (func.substr(start).starts_with(p)) start += p.size();
+    if (func.substr(start).starts_with(p)) {
+      start += std::string_view{p}.size();
+      break;
+    }
 #else
-  constexpr auto func = std::string_view{__PRETTY_FUNCTION__};
+  constexpr std::string_view func{__PRETTY_FUNCTION__};
   auto start = func.find("T = ") + 4;
 #endif
   auto end = func.find_first_of(";]> ,>", start);
-  if (end == std::string_view::npos) return {};
-  auto ns_end = func.rfind("::", end);
-  return (ns_end != std::string_view::npos && ns_end > start) ? func.substr(start, ns_end - start) : std::string_view{};
+  auto ns = func.substr(start, end - start);
+  auto pos = ns.rfind("::");
+  return (pos != std::string_view::npos) ? ns.substr(0, pos) : std::string_view{};
 }
 
 inline std::shared_ptr<nlohmann::json> InitJSONPtr() { return std::make_shared<nlohmann::json>(); }