cache_policy.hpp

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#ifndef CACHE_POLICY_HPP
#define CACHE_POLICY_HPP

#include <unordered_set>

namespace caches
{

template <typename Key>

class ICachePolicy
{
 public:

  virtual ~ICachePolicy() {}

  // handle element insertion in a cache
  virtual void Insert(const Key& key) = 0;

  // handle request to the key-element in a cache
  virtual void Touch(const Key& key) = 0;

  // handle element deletion from a cache
  virtual void Erase(const Key& key) = 0;

  // return a key of a replacement candidate
  virtual const Key& ReplCandidate() const = 0;

  // clear the cache
  virtual void Clear() = 0;

};

template <typename Key>
class NoCachePolicy : public ICachePolicy<Key>
{
 public:

  NoCachePolicy() = default;

  ~NoCachePolicy() override = default;

  void Insert(const Key& key) override
  {
    key_storage.emplace(key);
  }

  void Touch(const Key& key) override
  {
    // do not do anything
  }

  void Erase(const Key& key) override
  {
    key_storage.erase(key);
  }

  // return a key of a displacement candidate
  const Key& ReplCandidate() const override
  {
    return *key_storage.crbegin();
  }

  // return a key of a displacement candidate
  void Clear() override
  {
    key_storage.clear();
  }

 private:

  std::unordered_set<Key> key_storage;
};

}  // namespace caches

#endif  // CACHE_POLICY_HPP