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Plugins/MqttClient/Source/DTMqtt/MqttCPP/iclient_persistence.h

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+// Copyright 2023 Dexter.Wan. All Rights Reserved. 
+// EMail: 45141961@qq.com
+
+#ifndef __mqtt_iclient_persistence_h
+#define __mqtt_iclient_persistence_h
+
+#include "MQTTAsync.h"
+#include "types.h"
+#include "buffer_view.h"
+#include "string_collection.h"
+#include <vector>
+
+namespace mqtt {
+
+/**
+ * Allocate memory for use with user persistence.
+ *
+ * @param n The number of bytes for the buffer.
+ * @return A pointer to the allocated memory
+ */
+inline void* persistence_malloc(size_t n) {
+	return MQTTAsync_malloc(n);
+}
+
+/**
+ * Frees memory allocated with @ref persistence_malloc().
+ * @param p Pointer to a buffer obtained by persistence_malloc.
+ */
+inline void persistence_free(void* p) {
+	MQTTAsync_free(p);
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Represents a persistent data store, used to store outbound and inbound
+ * messages while they are in flight, enabling delivery to the QoS
+ * specified. You can specify an implementation of this interface using
+ * client::client(string, string, iclient_persistence), which the
+ * client will use to persist QoS 1 and 2 messages.
+ *
+ * If the methods defined throw the MqttPersistenceException then the state
+ * of the data persisted should remain as prior to the method being called.
+ * For example, if put(string, persistable) throws an exception at any
+ * point then the data will be assumed to not be in the persistent store.
+ * Similarly if remove(string) throws an exception then the data will be
+ * assumed to still be held in the persistent store.
+ *
+ * It is up to the persistence interface to log any exceptions or error
+ * information which may be required when diagnosing a persistence failure.
+ */
+class iclient_persistence
+{
+	friend class async_client;
+	friend class mock_persistence;
+
+	/** Callbacks from the C library */
+	static int persistence_open(void** handle, const char* clientID, const char* serverURI, void* context);
+	static int persistence_close(void* handle);
+	static int persistence_put(void* handle, char* key, int bufcount, char* buffers[], int buflens[]);
+	static int persistence_get(void* handle, char* key, char** buffer, int* buflen);
+	static int persistence_remove(void* handle, char* key);
+	static int persistence_keys(void* handle, char*** keys, int* nkeys);
+	static int persistence_clear(void* handle);
+	static int persistence_containskey(void* handle, char* key);
+
+public:
+	/** Smart/shared pointer to an object of this class. */
+	using ptr_t = std::shared_ptr<iclient_persistence>;
+	/** Smart/shared pointer to a const object of this class. */
+	using const_ptr_t = std::shared_ptr<const iclient_persistence>;
+
+	/**
+	 * Virtual destructor.
+	 */
+	virtual ~iclient_persistence() {}
+	/**
+	 * Initialize the persistent store.
+	 * This uses the client ID and server name to create a unique location
+	 * for the data store.
+	 * @param clientId The identifier string for the client.
+	 * @param serverURI The server to which the client is connected.
+	 */
+	virtual void open(const string& clientId, const string& serverURI) =0;
+	/**
+	 * Close the persistent store that was previously opened.
+	 */
+	virtual void close() =0;
+	/**
+	 * Clears persistence, so that it no longer contains any persisted data.
+	 */
+	virtual void clear() =0;
+	/**
+	 * Returns whether or not data is persisted using the specified key.
+	 * @param key The key to find
+	 * @return @em true if the key exists, @em false if not.
+	 */
+	virtual bool contains_key(const string& key) =0;
+	/**
+	 * Returns a collection of keys in this persistent data store.
+	 * @return A collection of strings representing the keys in the store.
+	 */
+	virtual string_collection keys() const =0;
+	/**
+	 * Puts the specified data into the persistent store.
+	 * @param key The key.
+	 * @param bufs The data to store
+	 */
+	virtual void put(const string& key, const std::vector<string_view>& bufs) =0;
+	/**
+	 * Gets the specified data out of the persistent store.
+	 * @param key The key
+	 * @return A const view of the data associated with the key.
+	 */
+	virtual string get(const string& key) const =0;
+	/**
+	 * Remove the data for the specified key.
+	 * @param key The key
+	 */
+	virtual void remove(const string& key) =0;
+};
+
+/** Smart/shared pointer to a persistence client */
+using iclient_persistence_ptr = iclient_persistence::ptr_t;
+
+/** Smart/shared pointer to a persistence client */
+using const_iclient_persistence_ptr = iclient_persistence::const_ptr_t;
+
+/////////////////////////////////////////////////////////////////////////////
+// end namespace mqtt
+}
+
+#endif		// __mqtt_iclient_persistence_h
+