Support the conversion for std::unordered_map (#932)

include/yaml-cpp/node/convert.h

@@ -12,6 +12,7 @@
 #include <limits>
 #include <list>
 #include <map>
+#include <unordered_map>
 #include <sstream>
 #include <type_traits>
 #include <vector>
@@ -251,6 +252,32 @@ struct convert<std::map<K, V, C, A>> {
   }
 };
 
+// std::unordered_map
+template <typename K, typename V, typename H, typename P, typename A>
+struct convert<std::unordered_map<K, V, H, P, A>> {
+  static Node encode(const std::unordered_map<K, V, H, P, A>& rhs) {
+    Node node(NodeType::Map);
+    for (const auto& element : rhs)
+      node.force_insert(element.first, element.second);
+    return node;
+  }
+
+  static bool decode(const Node& node, std::unordered_map<K, V, H, P, A>& rhs) {
+    if (!node.IsMap())
+      return false;
+
+    rhs.clear();
+    for (const auto& element : node)
+#if defined(__GNUC__) && __GNUC__ < 4
+      // workaround for GCC 3:
+      rhs[element.first.template as<K>()] = element.second.template as<V>();
+#else
+      rhs[element.first.as<K>()] = element.second.as<V>();
+#endif
+    return true;
+  }
+};
+
 // std::vector
 template <typename T, typename A>
 struct convert<std::vector<T, A>> {