Repo created

libs/base/linked_map.hpp

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+#pragma once
+
+#include "base/assert.hpp"
+
+#include <list>
+#include <unordered_map>
+
+namespace base
+{
+template <typename Key, typename Value, template <typename...> typename Map = std::unordered_map>
+class LinkedMap
+{
+public:
+  using KeyType = Key;
+  using ValueType = Value;
+  using ListType = std::list<std::pair<KeyType, ValueType>>;
+  using MapType = Map<Key, typename ListType::iterator>;
+
+  template <typename T>
+  bool Emplace(KeyType const & key, T && value)
+  {
+    if (m_map.find(key) != m_map.cend())
+      return false;
+
+    m_list.emplace_back(key, std::forward<T>(value));
+    m_map.emplace(key, std::prev(m_list.end()));
+    return true;
+  }
+
+  void PopFront()
+  {
+    CHECK(!m_map.empty(), ());
+    m_map.erase(m_list.front().first);
+    m_list.pop_front();
+  }
+
+  bool Erase(KeyType const & key)
+  {
+    auto const it = m_map.find(key);
+    if (it == m_map.cend())
+      return false;
+
+    m_list.erase(it->second);
+    m_map.erase(it);
+    return true;
+  }
+
+  bool Contains(KeyType const & key) const { return m_map.find(key) != m_map.cend(); }
+
+  ValueType const & Get(KeyType const & key) const
+  {
+    auto const it = m_map.find(key);
+    CHECK(it != m_map.cend(), ());
+
+    return it->second->second;
+  }
+
+  ValueType & Front() { return m_list.front().second; }
+
+  ValueType const & Front() const { return m_list.front().second; }
+
+  void Swap(LinkedMap & linkedMap)
+  {
+    m_map.swap(linkedMap.m_map);
+    m_list.swap(linkedMap.m_list);
+  }
+
+  size_t Size() const { return m_list.size(); }
+
+  bool IsEmpty() const { return m_list.empty(); }
+
+private:
+  ListType m_list;
+  MapType m_map;
+};
+}  // namespace base