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+/******************************************************************************
+ *
+ * Copyright (C) 1997-2020 by Dimitri van Heesch.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation under the terms of the GNU General Public License is hereby
+ * granted. No representations are made about the suitability of this software
+ * for any purpose. It is provided "as is" without express or implied warranty.
+ * See the GNU General Public License for more details.
+ *
+ * Documents produced by Doxygen are derivative works derived from the
+ * input used in their production; they are not affected by this license.
+ *
+ */
+
+#ifndef LINKEDMAP_H
+#define LINKEDMAP_H
+
+#include <unordered_map>
+#include <vector>
+#include <memory>
+#include <string>
+
+//! @brief Container class representing a vector of objects with unique keys.
+//! @details Elements can be quickly looked up given the key.
+//! When adding objects the order of addition is kept, and used while iterating.
+template<class T>
+class LinkedMap
+{
+ public:
+ using Ptr = std::unique_ptr<T>;
+ using Vec = std::vector<Ptr>;
+ using Map = std::unordered_map<std::string,T*>;
+ using iterator = typename Vec::iterator;
+
+ //! find an element given the key.
+ //! Returns a pointer to the element if found or nullptr if it is not found.
+ const T *find(const char *key) const
+ {
+ auto it = m_lookup.find(key);
+ return it!=m_lookup.end() ? it->second : nullptr;
+ }
+
+ //! non-const wrapper for find() const
+ T* find(const char *key)
+ {
+ return const_cast<T*>(static_cast<const LinkedMap&>(*this).find(key));
+ }
+
+ //! Adds a new element to the ordered set if it was not added already.
+ //! Return a non-owning pointer to the newly added item, or to the existing item if it was
+ //! already inserted before.
+ template<class...Args>
+ T *add(const char *key, Args&&... args)
+ {
+ T *result = find(key);
+ if (result==nullptr)
+ {
+ Ptr ptr = std::make_unique<T>(key,std::forward<Args>(args)...);
+ result = ptr.get();
+ m_lookup.insert({std::string(key),result});
+ m_entries.push_back(std::move(ptr));
+ }
+ return result;
+ }
+
+ iterator begin() { return m_entries.begin(); }
+ iterator end() { return m_entries.end(); }
+ bool empty() const { return m_entries.empty(); }
+ int size() const { return m_entries.size(); }
+
+ void clear()
+ {
+ m_entries.clear();
+ m_lookup.clear();
+ }
+
+ private:
+ Map m_lookup;
+ Vec m_entries;
+};
+
+
+#endif