dblru_cache.h

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#ifndef META_DBLRU_CACHE_H_
#define META_DBLRU_CACHE_H_

#if META_HAS_STD_SHARED_PTR_ATOMICS
#include <atomic>
#else
#include <mutex>
#include "util/shim.h"
#endif
#include <functional>
#include <vector>

#include "caching/maps/locking_map.h"
#include "util/optional.h"

namespace meta
{
namespace caching
{

template<class Key, class Value,
         template <class, class> class Map = locking_map>
class dblru_cache
{
  public:
    dblru_cache(uint64_t max_size);

    dblru_cache(dblru_cache&&);

    dblru_cache& operator=(dblru_cache);

    ~dblru_cache() = default;

    void swap(dblru_cache& other);

    void insert(const Key& key, const Value& value);

    template <class... Args>
    void emplace(Args&&... args);

    util::optional<Value> find(const Key& key);

    void clear();

  private:
    void handle_insert();

    std::shared_ptr<Map<Key, Value>> get_primary_map() const;

    std::shared_ptr<Map<Key, Value>> get_secondary_map() const;

    uint64_t max_size_;

#if META_HAS_STD_SHARED_PTR_ATOMICS
    std::atomic<uint64_t> current_size_;
#else
    uint64_t current_size_;
    std::unique_ptr<std::mutex> mutables_{make_unique<std::mutex>()};
#endif

    std::shared_ptr<Map<Key, Value>> primary_;

    std::shared_ptr<Map<Key, Value>> secondary_;
};

template <class Key, class Value>
using default_dblru_cache = dblru_cache<Key, Value>;
}
}

#include "caching/dblru_cache.tcc"
#endif