persistent.h

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// Copyright (c) 2023 anabrid GmbH
// Contact: https://www.anabrid.com/licensing/
// SPDX-License-Identifier: MIT OR GPL-2.0-or-later
 
#pragma once
 
#ifdef ARDUINO
 
#include "utils/json.h"
#include "utils/singleton.h"
#include <list>
 
namespace nvmconfig {
 
enum class Context {
  User, 
  Flash 
};
 
struct PersistentSettings {
  virtual std::string name() const = 0;
  virtual void reset_defaults() = 0;
  virtual void fromJson(JsonObjectConst src, Context c) = 0;
  virtual void toJson(JsonObject target, Context c) const = 0;
 
  virtual void clear() {}
};
 
// Teensy EEPROM is 4KB in size. This class claims the beginning
// of this storage. The required size is generously estimated, may be much less.
// Remember increasing the storage when more data have to be stored.
static constexpr int eeprom_address = 0, eeprom_size = 2'000;
 
// This number checks as a proof that the EEPROM stores something senseful. If it
// does not store a number >= this constant, it is resetted.
// Must not start from 0 in order to distinguish from "value not found" errors,
// thus the arbitrary nonzero 0xAA prefix.
static constexpr uint32_t required_magic = 0xAA03;
 
class PersistentSettingsWriter : public utils::HeapSingleton<PersistentSettingsWriter> {
  uint32_t version; 
  static constexpr bool use_messagepack = false; 
 
public:
  std::list<PersistentSettings *> subsystems;
 
  size_t write_to_eeprom(); 
  void read_from_eeprom();  
 
  // these methods just thread over subsystems
  void reset_defaults(bool write_to_eeprom = true);
 
  void fromJson(JsonObjectConst src, Context c);
 
  void toJson(JsonObject target, Context c);
 
  void info(JsonObject target);
 
  // Update configuration with a user call.
  // void set(JsonObjectConst serialized_conf, JsonObject& msg_out);
};
 
} // namespace nvmconfig
 
#endif // ARDUINO