connection_pool.hpp

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#ifndef GUARD_SQLITE_CONNECTION_POOL_HPP_INCLUDED
#define GUARD_SQLITE_CONNECTION_POOL_HPP_INCLUDED
 
#include <condition_variable>
#include <cstddef>
#include <functional>
#include <memory>
#include <mutex>
#include <vector>
 
#include <sqlite/connection.hpp>

namespace sqlite {
inline namespace v2 {

    class connection_pool {
    public:
        using connection_factory = std::function<std::shared_ptr<connection>()>;

        class lease {
        public:
            lease() = default;
            lease(connection_pool *pool, std::shared_ptr<connection> conn);
            lease(lease &&other) noexcept;
            lease &operator=(lease &&other) noexcept;
            lease(lease const &)            = delete;
            lease &operator=(lease const &) = delete;
            ~lease();
 
            connection &operator*() const;
            connection *operator->() const;
            std::shared_ptr<connection> shared() const;
 
        private:
            struct shared_state;
            void release();
            std::shared_ptr<shared_state> state_;
            std::shared_ptr<connection> connection_;
        };

        connection_pool(std::size_t capacity, connection_factory factory);

        static connection_factory make_factory(std::string db,
                                               open_mode mode = open_mode::open_or_create,
                                               filesystem_adapter_ptr fs = {});

        lease acquire();

        std::size_t capacity() const;

        std::size_t idle_count() const;

        std::size_t created_count() const;
 
    private:
        friend class lease;
        void release(std::shared_ptr<connection> conn);
 
        connection_factory factory_;
        std::size_t capacity_;
        std::size_t created_ = 0;
        mutable std::mutex mutex_;
        std::condition_variable cv_;
        std::vector<std::shared_ptr<connection>> idle_;
    };
 
} // namespace v2
} // namespace sqlite
 
#endif