minor redesign of is_ipv4

src/checkers.cpp

@@ -5,24 +5,33 @@ namespace ada::checkers {
 
 ada_really_inline ada_constexpr bool is_ipv4(std::string_view view) noexcept {
   size_t last_dot = view.rfind('.');
-  if (last_dot == view.size() - 1) {
-    view.remove_suffix(1);
-    last_dot = view.rfind('.');
+  if (last_dot != std::string_view::npos) {
+    // We have at least one dot.
+    //
+    // If the address ends with a dot, we need to prune it (special case).
+    if (last_dot == view.size() - 1) {
+      view.remove_suffix(1);
+      last_dot = view.rfind('.');
+      if (last_dot != std::string_view::npos) {
+        view = view.substr(last_dot + 1);
+      }
+    } else {
+      // We have at least one dot and the address does not end with a dot.
+      view = view.substr(last_dot + 1);
+    }
   }
-  std::string_view number =
-      (last_dot == std::string_view::npos) ? view : view.substr(last_dot + 1);
-  if (number.empty()) {
+  if (view.empty()) {
     return false;
   }
   /** Optimization opportunity: we have basically identified the last number of
      the ipv4 if we return true here. We might as well parse it and have at
      least one number parsed when we get to parse_ipv4. */
-  if (std::all_of(number.begin(), number.end(), ada::checkers::is_digit)) {
+  if (std::all_of(view.begin(), view.end(), ada::checkers::is_digit)) {
     return true;
   }
-  return (checkers::has_hex_prefix(number) &&
-          std::all_of(number.begin() + 2, number.end(),
-                      ada::unicode::is_lowercase_hex));
+  return (checkers::has_hex_prefix(view) &&
+          (view.size() == 2 || std::all_of(view.begin() + 2, view.end(),
+                                           ada::unicode::is_lowercase_hex)));
 }
 
 // for use with path_signature, we include all characters that need percent