gitignore modefied

https://github.com/moneroexamples/onion-monero-blockchain-explorer/pull/45

ext/vpetrigocaches/lru_cache_policy.hpp

@@ -0,0 +1,63 @@
+#ifndef LRU_CACHE_POLICY_HPP
+#define LRU_CACHE_POLICY_HPP
+
+#include <list>
+#include <unordered_map>
+#include "cache_policy.hpp"
+
+namespace caches
+{
+template <typename Key>
+class LRUCachePolicy : public ICachePolicy<Key>
+{
+
+ public:
+
+  using lru_iterator = typename std::list<Key>::const_iterator;
+  
+  LRUCachePolicy() = default;
+  ~LRUCachePolicy() = default;
+  
+  void Insert(const Key& key) override
+  {
+    lru_queue.emplace_front(key);
+    key_finder[key] = lru_queue.cbegin();
+  }
+  
+  void Touch(const Key& key) override
+  {
+    // move the touched element at the beginning of the lru_queue 
+    lru_queue.splice(lru_queue.cbegin(), lru_queue, key_finder[key]);
+  }
+  
+  void Erase(const Key& key) override
+  {
+    // remove the least recently used element
+    key_finder.erase(lru_queue.back());
+
+    lru_queue.pop_back();
+  }
+
+  // return a key of a displacement candidate
+  const Key& ReplCandidate() const override
+  {
+    return lru_queue.back();
+  }
+
+  // return a key of a displacement candidate
+  void Clear() override
+  {
+      lru_queue.clear();
+      key_finder.clear();
+  }
+  
+ private:
+
+  std::list<Key> lru_queue;
+
+  std::unordered_map<Key, lru_iterator> key_finder; 
+};
+
+} // namespace caches
+
+#endif // LRU_CACHE_POLICY_HPP