Squash of branch setup

main/io/nvs_handler.h

@@ -0,0 +1,70 @@
+#pragma once
+#include "io/io.h"
+#include "freertos/FreeRTOS.h"
+#include "nvs.h"
+
+struct NVSIteratorGuard {
+public:
+  ~NVSIteratorGuard() {
+    if (iterator) {
+      nvs_release_iterator(iterator);
+    }
+  }
+
+  // accessors to the iterator, the internal state should not be modified directly
+  // The iterator is advanced using advance_iter(), and is changed to nullptr on error or end
+  // Caller MUST NOT release the iterator manually nor call get_iterator after advance_iter
+  const nvs_iterator_t& get_iterator() const {
+    return iterator;
+  }
+
+  void advance_iter() {
+    if (iterator) {
+      // advance the iterator and update the internal state
+      esp_err_t err = nvs_entry_next(&iterator);
+      if (err != ESP_OK) {
+        error = err;
+        iterator = nullptr;
+      }
+    }
+  }
+
+  esp_err_t get_error() const {
+    return error;
+  }
+  bool is_valid() const {
+    return iterator != nullptr && error == ESP_OK;
+  }
+  friend class NVSStorageHandler;
+private:
+  NVSIteratorGuard(nvs_iterator_t it
+    , esp_err_t err
+  ) : iterator(it), error(err) { }
+  nvs_iterator_t iterator;
+  esp_err_t error;
+};
+
+class NVSStorageHandler : public KVStorageHandler {
+public:
+  NVSStorageHandler(
+    const char* name_space
+  );
+  ~NVSStorageHandler() override;
+
+  void init(const EventGroupHandle_t& system_event_group) override;
+
+  void put(const std::string& key, const std::string& value) override;
+
+  std::string get(const std::string& key) const override;
+  esp_err_t process_all(KeyValueProcessor processor, void* arg) const override;
+  esp_err_t process_filtered(const std::string& key_prefix, KeyValueProcessor processor, void* arg) const override;
+  esp_err_t process_filtered(FilterFunc filter_func, KeyValueProcessor processor, void* arg) const override;
+
+  void remove(const std::string& key) override;
+
+private:
+  NVSIteratorGuard create_iterator() const;
+
+  nvs_handle_t nvsHandle = 0;
+  const char* name_space;
+};