esphome/esphome/core/preferences.h

#pragma once

#include <cstring>
#include <cstdint>
#include <type_traits>

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_;
};

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;

#ifndef USE_ESP8266
  template<typename T, typename std::enable_if<std::is_trivially_copyable<T>::value, bool>::type = true>
#else
  // esp8266 toolchain doesn't have is_trivially_copyable
  template<typename T>
#endif
  ESPPreferenceObject make_preference(uint32_t type, bool in_flash) {
    return this->make_preference(sizeof(T), type, in_flash);
  }
#ifndef USE_ESP8266
  template<typename T, typename std::enable_if<std::is_trivially_copyable<T>::value, bool>::type = true>
#else
  template<typename T>
#endif
  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