gitignore modefied

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

ext/vpetrigocaches/lfu_cache_policy.hpp

@@ -0,0 +1,76 @@
+#ifndef LFU_CACHE_POLICY_HPP
+#define LFU_CACHE_POLICY_HPP
+
+#include <cstddef>
+#include <unordered_map>
+#include <map>
+#include <iostream>
+#include "cache_policy.hpp"
+
+namespace caches
+{
+template <typename Key>
+class LFUCachePolicy : public ICachePolicy<Key>
+{
+ public:
+
+  using lfu_iterator = typename std::multimap<std::size_t, Key>::iterator;
+
+  LFUCachePolicy() = default;
+
+  ~LFUCachePolicy() override = default;
+
+  void Insert(const Key& key) override
+  {
+    constexpr std::size_t INIT_VAL = 1;
+
+    // all new value initialized with the frequency 1
+    lfu_storage[key] = frequency_storage.emplace_hint(
+            frequency_storage.cbegin(), INIT_VAL, key);
+  }
+
+  void Touch(const Key& key) override
+  {
+    // get the previous frequency value of a key
+    auto elem_for_update = lfu_storage[key];
+
+    auto updated_elem = std::make_pair(
+            elem_for_update->first + 1, elem_for_update->second);
+
+    // update the previous value
+    frequency_storage.erase(elem_for_update);
+
+    lfu_storage[key] = frequency_storage.emplace_hint(
+            frequency_storage.cend(), std::move(updated_elem));
+  }
+
+  void Erase(const Key& key) override
+  {
+    frequency_storage.erase(lfu_storage[key]);
+    lfu_storage.erase(key);
+  }
+
+  const Key& ReplCandidate() const override
+  {
+    // at the beginning of the frequency_storage we have the
+    // least frequency used value
+    return frequency_storage.cbegin()->second;
+  }
+
+  // return a key of a displacement candidate
+  void Clear() override
+  {
+    frequency_storage.clear();
+    lfu_storage.clear();
+  }
+
+
+ private:
+
+  std::multimap<std::size_t, Key> frequency_storage;
+
+  std::unordered_map<Key, lfu_iterator> lfu_storage;
+};
+} // namespace caches
+
+#endif // LFU_CACHE_POLICY_HPP