intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 60 insertions, 0 deletions

diff --git a/util/generic/mapfindptr.h b/util/generic/mapfindptr.h
new file mode 100644
index 0000000000..bc10cac60f
--- /dev/null
+++ b/util/generic/mapfindptr.h
@@ -0,0 +1,60 @@
+#pragma once
+
+#include <type_traits>
+
+/** MapFindPtr usage:
+
+if (T* value = MapFindPtr(myMap, someKey) {
+    Cout << *value;
+}
+
+*/
+
+template <class Map, class K>
+inline auto MapFindPtr(Map& map, const K& key) {
+    auto i = map.find(key);
+
+    return (i == map.end() ? nullptr : &i->second);
+}
+
+template <class Map, class K>
+inline auto MapFindPtr(const Map& map, const K& key) {
+    auto i = map.find(key);
+
+    return (i == map.end() ? nullptr : &i->second);
+}
+
+/** helper for THashMap/TMap */
+template <class Derived>
+struct TMapOps {
+    template <class K>
+    inline auto FindPtr(const K& key) {
+        return MapFindPtr(static_cast<Derived&>(*this), key);
+    }
+
+    template <class K>
+    inline auto FindPtr(const K& key) const {
+        return MapFindPtr(static_cast<const Derived&>(*this), key);
+    }
+
+    template <class K, class DefaultValue>
+    inline auto Value(const K& key, const DefaultValue& defaultValue) const -> std::remove_reference_t<decltype(*this->FindPtr(key))> {
+        if (auto found = FindPtr(key)) {
+            return *found;
+        }
+        return defaultValue;
+    }
+
+    template <class K, class V>
+    inline const V& ValueRef(const K& key, V& defaultValue) const {
+        static_assert(std::is_same<std::remove_const_t<V>, typename Derived::mapped_type>::value, "Passed default value must have the same type as the underlying map's mapped_type.");
+
+        if (auto found = FindPtr(key)) {
+            return *found;
+        }
+        return defaultValue;
+    }
+
+    template <class K, class V>
+    inline const V& ValueRef(const K& key, V&& defaultValue) const = delete;
+};