CursorManager.h

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#pragma once
 
#include "Api.h"
#include "HandlerManager.h"
#include "IStorageBackend.h"
#include "LifecycleManager.h"
#include "ObjectManager.h"
#include "Types.h"
 
#include <cstddef>
#include <string>
#include <vector>

 
namespace nt {
    class CursorManager {
      public:
        static constexpr std::size_t PAGE_SIZE = 1;

        explicit CursorManager(IStorageBackend& backend, LifecycleManager* lifecycles = nullptr,
                               ObjectManager* objects = nullptr);

        struct cursor {
            std::string merkle_root;
            std::vector<std::string> args;
            std::vector<Tuple> page;
            std::size_t page_position = 0;
            std::size_t fetch_offset = 0; // next Merkle::Page() call starts here
            bool exhausted = false;
            bool is_ephemeral = false;
            ObjectManager::ephemeral_object_type::Generator generator;
            ObjectManager::registry* pinned_snapshot = nullptr;
        };

        cursor* Open(HandlerManager::handle* handle, const std::string& merkle_root = "");

        Tuple* Next(cursor* cursor);

        void Close(cursor* cursor);
 
      private:
        IStorageBackend& backend_;
        LifecycleManager* lifecycles_ = nullptr;
        ObjectManager* objects_ = nullptr;

        void LoadPage(cursor* c);
    };
} // namespace nt