statement_cache.hpp

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#ifndef GUARD_SQLITE_STATEMENT_CACHE_HPP_INCLUDED
#define GUARD_SQLITE_STATEMENT_CACHE_HPP_INCLUDED
 
#include <cstddef>
#include <list>
#include <memory>
#include <mutex>
#include <string>
#include <string_view>
#include <unordered_map>
 
struct sqlite3;
struct sqlite3_stmt;

namespace sqlite {
inline namespace v2 {
    struct connection;

    struct statement_cache_config {
        std::size_t capacity = 32;   
        bool enabled         = true; 
    };

    class statement_cache {
    public:
        explicit statement_cache(statement_cache_config cfg = {});
 
        sqlite3_stmt *acquire(sqlite3 *db, std::string_view sql);
        void release(std::string_view sql, sqlite3_stmt *stmt);
        void clear(sqlite3 *db);
        void reset(statement_cache_config cfg);
        statement_cache_config config() const noexcept {
            return config_;
        }
 
    private:
        struct entry {
            std::string sql;
            sqlite3_stmt *stmt = nullptr;
        };
 
        using lru_list = std::list<entry>;
        using iterator = lru_list::iterator;
 
        statement_cache_config config_;
        lru_list lru_;
        std::unordered_map<std::string, iterator> map_;
        mutable std::mutex mutex_;
    };
} // namespace v2
} // namespace sqlite
 
#endif // GUARD_SQLITE_STATEMENT_CACHE_HPP_INCLUDED