fsfw/storagemanager/ConstStorageAccessor.h

#ifndef FRAMEWORK_STORAGEMANAGER_CONSTSTORAGEACCESSOR_H_
#define FRAMEWORK_STORAGEMANAGER_CONSTSTORAGEACCESSOR_H_

#include <framework/storagemanager/storeAddress.h>
#include <framework/returnvalues/HasReturnvaluesIF.h>
#include <cstddef>

class StorageManagerIF;

/**
 * @brief 	Helper classes to facilitate safe access to storages which is also
 * 			conforming to RAII principles
 * @details
 * Accessor class which can be returned by pool manager or passed and set by
 * pool managers to have safe access to the pool resources.
 *
 * These helper can be used together with the StorageManager classes to manage
 * access to a storage. It can take care of thread-safety while also providing
 * mechanisms to automatically clear storage data.
 */
class ConstStorageAccessor {
	//! StorageManager classes have exclusive access to private variables.
	template<uint8_t NUMBER_OF_POOLS>
	friend class PoolManager;
	template<uint8_t NUMBER_OF_POOLS>
	friend class LocalPool;
public:
	/**
	 * @brief	Simple constructor which takes the store ID of the storage
	 * 			entry to access.
	 * @param storeId
	 */
	ConstStorageAccessor(store_address_t storeId);
	ConstStorageAccessor(store_address_t storeId, StorageManagerIF* store);

	/**
	 * @brief 	The destructor in default configuration takes care of
	 * 			deleting the accessed pool entry and unlocking the mutex
	 */
	virtual ~ConstStorageAccessor();

	/**
	 * @brief	Returns a pointer to the read-only data
	 * @return
	 */
	const uint8_t* data() const;

	/**
	 * @brief	Copies the read-only data to the supplied pointer
	 * @param pointer
	 */
	virtual ReturnValue_t getDataCopy(uint8_t *pointer, size_t maxSize);

	/**
	 * @brief   Calling this will prevent the Accessor from deleting the data
	 *          when the destructor is called.
	 */
	void release();

	/**
	 * Get the size of the data
	 * @return
	 */
	size_t size() const;

	/**
	 * Get the storage ID.
	 * @return
	 */
	store_address_t getId() const;

	void print() const;

	/**
	 * @brief	Move ctor and move assignment allow returning accessors as
	 * 			a returnvalue. They prevent resource being free prematurely.
	 * Refer to: https://github.com/MicrosoftDocs/cpp-docs/blob/master/docs/cpp/
	 * move-constructors-and-move-assignment-operators-cpp.md
	 * @param
	 * @return
	 */
	ConstStorageAccessor& operator= (ConstStorageAccessor&&);
	ConstStorageAccessor(ConstStorageAccessor&&);

	//! The copy ctor and copy assignemnt should be deleted implicitely
	//! according to https://foonathan.net/2019/02/special-member-functions/
	//! but I still deleted them to make it more explicit. (remember rule of 5).
	ConstStorageAccessor& operator=(const ConstStorageAccessor&) = delete;
	ConstStorageAccessor(const ConstStorageAccessor&) = delete;
protected:
	const uint8_t* constDataPointer = nullptr;
	store_address_t storeId;
	size_t size_ = 0;
	//! Managing pool, has to assign itself.
	StorageManagerIF* store = nullptr;
	bool deleteData = true;

	enum class AccessState {
		UNINIT,
		ASSIGNED
	};
	//! Internal state for safety reasons.
	AccessState internalState = AccessState::UNINIT;
	/**
	 * Used by the pool manager instances to assign themselves to the
	 * accessor. This is necessary to delete the data when the acessor
	 * exits the scope ! The internal state will be considered read
	 * when this function is called, so take care all data is set properly as
	 * well.
	 * @param
	 */
	void assignStore(StorageManagerIF*);
};


#endif /* FRAMEWORK_STORAGEMANAGER_CONSTSTORAGEACCESSOR_H_ */