esphome/esphome/core/preferences.h

#pragma once

#include <cstring>
#include <cstdint>

#include "esphome/core/helpers.h"

namespace esphome {

class ESPPreferenceBackend {
 public:
  virtual bool save(const uint8_t *data, size_t len) = 0;
  virtual bool load(uint8_t *data, size_t len) = 0;
};

class ESPPreferenceObject {
 public:
  ESPPreferenceObject() = default;
  ESPPreferenceObject(ESPPreferenceBackend *backend) : backend_(backend) {}

  template<typename T> bool save(const T *src) {
    if (backend_ == nullptr)
      return false;
    return backend_->save(reinterpret_cast<const uint8_t *>(src), sizeof(T));
  }

  template<typename T> bool load(T *dest) {
    if (backend_ == nullptr)
      return false;
    return backend_->load(reinterpret_cast<uint8_t *>(dest), sizeof(T));
  }

 protected:
  ESPPreferenceBackend *backend_{nullptr};
};

class ESPPreferences {
 public:
  virtual ESPPreferenceObject make_preference(size_t length, uint32_t type, bool in_flash) = 0;
  virtual ESPPreferenceObject make_preference(size_t length, uint32_t type) = 0;

  /**
   * Commit pending writes to flash.
   *
   * @return true if write is successful.
   */
  virtual bool sync() = 0;

  /**
   * Forget all unsaved changes and re-initialize the permanent preferences storage.
   * Usually followed by a restart which moves the system to "factory" conditions
   *
   * @return true if operation is successful.
   */
  virtual bool reset() = 0;

  template<typename T, enable_if_t<is_trivially_copyable<T>::value, bool> = true>
  ESPPreferenceObject make_preference(uint32_t type, bool in_flash) {
    return this->make_preference(sizeof(T), type, in_flash);
  }

  template<typename T, enable_if_t<is_trivially_copyable<T>::value, bool> = true>
  ESPPreferenceObject make_preference(uint32_t type) {
    return this->make_preference(sizeof(T), type);
  }
};

extern ESPPreferences *global_preferences;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)

}  // namespace esphome